Catalytic materials and uses thereof

Abstract

A catalytic material and a method of making the catalytic material are described. The use of the catalytic material in catalyzing ammonia decomposition processes is also described. The catalytic material comprises a metal oxide and a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof, and is particularly active in the catalytic decomposition of ammonia, even at low temperatures.

Description

[0001] This application is a divisional application of the patent application with the application number 202180027700.8, the application date of February 5, 2021, and the invention title of "Catalytic Materials and Their Uses". Technical Field

[0002] The present invention relates to catalytic materials. More specifically, the present invention relates to catalytic materials suitable for ammonia catalytic decomposition. The present invention also relates to a method for preparing a catalytic material and an ammonia decomposition method using the catalytic material. Background Art

[0003] Catalytic ammonia decomposition has long been regarded as an important tool in the environmental purification of gaseous or liquid pollutant streams. Recently, ammonia has been considered an interesting hydrogen alternative fuel due to its extremely high energy density and the convenience of its transportation for stationary and mobile applications 1 . The catalytic decomposition of ammonia produces hydrogen, which can be used to supply internal combustion engines or fuel cells. Compared with directly using hydrogen for commercial applications, hydrogen itself has difficulties in handling and a low volumetric energy density. Ammonia can be liquefied at 20 °C and about 8 bar, thus avoiding many safety problems associated with the long-distance transportation of hydrogen. In addition, due to other carbon-containing by-products generated by CO and carbon pollutants, the carbon-free decomposition of ammonia by wind and solar energy also significantly reduces the performance of fuel cells 2 .

[0004] Therefore, in recent years, ammonia has been widely used in H2 storage and other energy applications 3,4 .

[0005] However, so far, due to the thermodynamic limit of the endothermic process and the lack of effective catalytic strategies, ammonia can only be decomposed at high temperatures to produce a large amount of hydrogen. In recent years, a variety of metal catalysts for ammonia decomposition have been developed, including Ru 5-15 , Rh 16,17 , Pd 16,17 , Pt 12 , Ni 6,18–20 , Fe 19 and Co 16 . In addition, for many supports, such as SiO2 5,6 , Al2O3 5,9 , zeolite 1 , carbon nanotubes 9 , activated carbon 9 , C 12 A7 10 , MgO 12–14Research has been carried out, and the carrier shows a moderate hydrogen generation rate at high temperatures (>500 °C). However, none of these methods exhibit comparable activity at lower temperatures, making them industrially impractical. This is mainly due to limitations in the catalytic rate-determining steps (such as N recombination and N-H bond cleavage). Altering the reaction pathway is an attractive strategy for efficient hydrogen production via ammonia decomposition at low temperatures.

[0006] The present invention is designed in view of the above considerations. Summary of the Invention

[0007] According to a first aspect of the present invention, there is provided a catalytic material comprising:

[0008] a) a metal oxide, and

[0009] b) a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0010] wherein the metal oxide comprises magnesium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

[0011] According to a second aspect of the present invention, there is provided a method for preparing the catalytic material according to the first aspect, the method comprising:

[0012] a) providing a metal oxide as defined herein,

[0013] b) depositing a metal M on the metal oxide, where M is as defined herein, and

[0014] c) optionally reducing the product resulting from step b).

[0015] According to a third aspect of the present invention, there is provided a catalytic material obtainable, directly or indirectly, by the method according to the second aspect.

[0016] According to a fourth aspect of the present invention, there is provided a method for catalytic decomposition of ammonia, the method comprising the step of contacting ammonia with a catalytic material comprising:

[0017] a) a metal oxide comprising:

[0018] i) magnesium oxide comprising an exposed (111) crystal plane, or

[0019] ii) cerium oxide, or

[0020] iii) magnesium oxide comprising an exposed (111) crystal plane and cerium oxide;

[0021] b) a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof.

[0022] Suitably, the catalytic material used in the fourth aspect of the present invention is the same as the catalytic material of the first aspect of the present invention. Detailed embodiments

[0023] Throughout the description and claims of this specification, if the term "comprise" (or "comprises" or "comprising") is used herein to describe a subject matter, the use of the terms "consist of" (or "consists of" or "consisting of") or "consist essentially of" (or "consists essentially of" or "consisting essentially of") to describe the same subject matter is also contemplated.

[0024] Throughout the specification and claims of this application, unless the context requires otherwise, the singular forms include the plural forms. In particular, when using the indefinite article, unless the context requires otherwise, the specification should be understood to contemplate both the plural and the singular.

[0025] Features described in connection with a particular aspect, embodiment or example of the present invention should be understood to be applicable to any other aspect, embodiment or example described herein, unless incompatible therewith. All features disclosed in this specification (including any appended claims, abstract and drawings), and / or all steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The present invention is not limited to the details of any particular embodiment set forth herein. The present invention extends to any novel or any novel combination of the features disclosed in this specification (including any appended claims, abstract and drawings), or any novel one or any novel combination of the steps of any method or process so disclosed.

[0026] Unless otherwise specified, if the amount or concentration of a particular component of a given product is specified as a weight percentage (wt% or % w / w), the weight percentage refers to the percentage of the weight of the component relative to the total weight of the product as a whole. Those skilled in the art will understand that the sum of the weight percentages of all components of the product will total 100 wt%. However, if not all components are listed (e.g., if a product is said to "comprise" one or more particular components), the balance of the weight percentage may optionally be made up to 100 wt% by the unspecified components.

[0027] Catalytic material

[0028] In a first aspect, the present invention provides a catalytic material comprising:

[0029] a) a metal oxide, and

[0030] b) a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0031] wherein the metal oxide comprises magnesium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

[0032] The inventors surprisingly found that the present catalytic material is particularly active in the catalytic decomposition of ammonia, even at relatively low temperatures. In particular, the catalytic material is capable of achieving a hydrogen formation rate of 27.0 mmol g cat -1 h -1 at a weight hourly space velocity (WHSV) of 30,000 mL g cat -1 min -1 at only 400 °C. Without wishing to be bound by theory, the inventors believe that these results are at least partially attributed to the nature of the metal oxide support material, whose polar crystal planes can exhibit excellent proton conduction properties and thus facilitate the removal of protons from the surface of metal M. In addition, interestingly, the catalytic material allows ammonia to decompose into hydrogen without generating nitrogen oxides, thus providing an industrially attractive method for CO-free x hydrogen production in practical applications.

[0033] The metal oxide comprises magnesium oxide, wherein the magnesium oxide comprises an exposed (111) crystal plane. The (111) crystal plane of magnesium oxide is polar because it contains alternating layers of positively charged Mg 2+ and negatively charged O 2- ions, such that the outermost surface has a net charge. This is in contrast to the non-polar (110) and (100) crystal planes of magnesium oxide, which contain Mg 2+ and O 2-An equal mixture of ions such that the outermost surface is net neutral. Without wishing to be bound by theory, the inventors believe that the polar (111) crystal plane of magnesium oxide produces a significantly enhanced proton mobility, which enhances bond activation and proton removal during the ammonia decomposition reaction. Suitably, the (111) crystal plane forms at least 10% of the magnesium oxide exposed surface. For example, the amount of the (111) crystal plane in magnesium oxide can be determined by integrating the characteristic peaks in nuclear magnetic resonance. More suitably, the (111) crystal plane forms at least 20% of the magnesium oxide exposed surface. Even more suitably, the (111) crystal plane forms at least 30% of the magnesium oxide exposed surface. Still more suitably, the (111) crystal plane forms at least 40% of the magnesium oxide exposed surface. Still even more suitably, the (111) crystal plane forms 40 to 50% of the magnesium oxide exposed surface. Most suitably, the (111) crystal plane forms 44 to 48% of the magnesium oxide exposed surface.

[0034] One method employed by the inventors produced magnesium oxide in which the (111) crystal plane forms approximately 46% of the magnesium oxide exposed surface. However, the inventors have shown that the presence of a large amount of the (111) crystal plane has a significant beneficial effect on the catalytic performance of the material, such that magnesium oxide with an even higher number of the (111) crystal planes can be even more catalytically active. Thus, in any of the above embodiments, the (111) crystal plane can form up to 60%, 70%, 80%, 90% or 100% of the magnesium oxide exposed surface. For example, such an increased amount of the (111) crystal plane can be present in magnesium oxide particles having an octahedral form, where all 8 crystal planes are the (111) crystal planes.

[0035] The magnesium oxide is suitably in the form of nanoparticles (i.e., particles in which the largest dimension is less than 1 micron). The average particle size of the nanoparticles (based on the largest dimension of each particle) is suitably 50 to 500 nm, more suitably 100 to 250 nm. The nanoparticles can have various forms, but are typically provided as flakes (e.g., hexagonal flakes) having upper and lower (111) crystal planes and a thickness of 1 to 20 nm, suitably 2 to 15 nm. Alternatively, the nanoparticles can have the above-mentioned octahedral form.

[0036] It is noted that the term "magnesium oxide" used throughout this specification includes the corresponding hydrolyzed or partially hydrolyzed forms that may be present, particularly on the surface of magnesium oxide, especially after the material has been treated by hydrogen reduction.

[0037] Suitably, the magnesium oxide has a periclase crystal structure.

[0038] The metal M is typically applied to the metal oxide by chemical vapor deposition, wetness impregnation or ball milling. Thus, it can be understood that the metal M is distributed (i.e., dispersed) on the surface of the metal oxide.

[0039] The metal M may be present in the catalytic material as an oxide (e.g., ruthenium oxide), in metallic form (e.g., metallic ruthenium), or both. If the catalytic material has not undergone a reduction treatment, at least a portion of the metal M will be present as an oxide. If the catalytic material has undergone a reduction treatment, at least a portion of the metal M will be present in metallic form. In one embodiment, greater than 90 wt% (or all) of the metal M is present as an oxide. Alternatively, greater than 90 wt% (or all) of the metal M is present in metallic form.

[0040] The average particle size of the metal M (whether present as an oxide or in metallic form) is suitably from 0.5 to 100 nm. The average particle size of the metal M can be determined, for example, by transmission electron microscopy. More suitably, the average particle size of the metal M is from 2 to 20 nm.

[0041] In one embodiment, the metal M is selected from the group consisting of Ru, Fe, and mixtures thereof. In a particularly preferred embodiment, the metal M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo. In a particularly preferred embodiment, the metal M is only Ru.

[0042] In another embodiment, the metal M is a mixture of Co and Mo.

[0043] In one embodiment, the catalytic material comprises:

[0044] 0.01 - 30.0% w / w of the metal M, and

[0045] 40.0 - 99.9% w / w of the metal oxide.

[0046] The amount of the metal M refers to the amount of the element M, which can be determined by inductively coupled plasma optical emission spectrometry (ICP - OES). The metal M is present as an oxide or in metallic form. Suitably, the catalytic material comprises:

[0047] 0.01 - 20.0% w / w of the metal M, and

[0048] 40.0 - 99.9% w / w of the metal oxide.

[0049] More suitably, the catalytic material comprises:

[0050] 0.01 - 15.0% w / w of the metal M, and

[0051] 55.0 - 99.9% w / w of the metal oxide.

[0052] Even more suitably, the catalytic material comprises:

[0053] 0.5 - 10.0% w / w of the metal M, and

[0054] 70.0 - 99.5% w / w of the metal oxide.

[0055] Even more suitably, the catalytic material comprises:

[0056] 1.5 - 7.0% w / w of the metal M, and

[0057] 80.0 - 98.5% w / w of the metal oxide.

[0058] Even even more suitably, the catalytic material comprises:

[0059] 2.5 - 6.0% w / w of the metal M, and

[0060] 85.0 - 97.5% w / w of the metal oxide.

[0061] Most suitably, the catalytic material comprises:

[0062] 2.8 - 4.5% w / w of the metal M, and

[0063] 88.0 - 97.2% w / w of the metal oxide.

[0064] The catalytic material may further comprise a promoter Q. The addition of the promoter significantly improves the activity of the catalytic material. The promoter Q can be incorporated into the catalytic material by wet impregnation, which is familiar to those skilled in the art. Suitably, the promoter Q is selected from the group consisting of Cs, K, Ba, and mixtures of two or more thereof. More suitably, Q is selected from the group consisting of Cs, K, and mixtures thereof. Most suitably, Q is Cs.

[0065] If the catalytic material comprises the promoter Q, the molar ratio of the metal M to Q (i.e., M:Q) can be 1:(0.1 - 3). Suitably, the molar ratio of M to Q (i.e., M:Q) is 1:(0.5 - 1.5). More suitably, the molar ratio of M:Q is 1:(0.75 - 1.25).

[0066] The catalytic material may further comprise an acidic zeolite. The catalytic material may comprise 0.01 - 50.0% w / w of the acidic zeolite. Suitably, the catalytic material comprises 0.01 - 20.0% w / w of the acidic zeolite. In a specific embodiment, the catalytic material is ZSM - 5.

[0067] In one embodiment, the metal oxide consists essentially of or consists of magnesium oxide having any of the definitions shown above.

[0068] In an alternative embodiment, the metal oxide comprises magnesium oxide having any of the definitions shown above, and cerium oxide. Regardless of the specific morphology of the cerium oxide, the combination of cerium oxide and magnesium oxide significantly improves the catalytic performance of the catalytic material.

[0069] When the metal oxide comprises magnesium oxide and cerium oxide having any of the definitions shown above, the catalytic performance of the catalytic material is significantly improved when the cerium oxide comprises exposed (100) crystal planes. Compared with the polycrystalline form, the cubic and rod-like morphologies of cerium oxide contain an increased amount of polar (100) crystal planes. Thus, the cerium oxide suitably comprises exposed (100) crystal planes. More suitably, the (100) crystal planes form at least 20% of the exposed surface of the cerium oxide. For example, the amount of (100) crystal planes in the cerium oxide can be determined by integrating the characteristic peaks in nuclear magnetic resonance. Even more suitably, the (100) crystal planes form at least 40% of the exposed surface of the cerium oxide. Still more suitably, the (100) crystal planes form at least 60% of the exposed surface of the cerium oxide. Still more suitably, the (100) crystal planes form at least 80% of the exposed surface of the cerium oxide. Yet more suitably, the (100) crystal planes form at least 85% of the exposed surface of the cerium oxide. Most suitably, the (100) crystal planes form 88 to 96% of the exposed surface of the cerium oxide. Theoretically, the (100) crystal planes can form at most 50% of the exposed surface of cerium oxide having a rod-like morphology. In contrast, the (100) crystal planes theoretically form the entire exposed surface of cerium oxide having a cubic morphology.

[0070] In one embodiment, the cerium oxide is present as a mixture of cubic and rod-like morphologies.

[0071] In one embodiment, the cerium oxide is present mainly as a cubic morphology.

[0072] The cerium oxide is suitably in the form of nanoparticles (i.e., particles having a maximum size less than 1 micron). The average particle size of the nanoparticles (based on the maximum size of each particle) is suitably 5 - 50 nm, more suitably 10 - 30 nm. The nanoparticles can have various forms, but are typically provided in the above-mentioned rod-like and / or cubic forms.

[0073] When the metal oxide comprises magnesium oxide having any of the definitions shown above and cerium oxide having any of the meanings shown above, the weight ratio of magnesium oxide to cerium oxide can be 1:(0.1 - 10.0). Suitably, the weight ratio of magnesium oxide to cerium oxide is 1:(0.25 - 4.0). More suitably, the weight ratio of magnesium oxide to cerium oxide is 1:(0.50 - 2.0). Even more suitably, the weight ratio of magnesium oxide to cerium oxide is 1:(0.75 - 1.25). Most suitably, the weight ratio of magnesium oxide to cerium oxide is 1:(0.90 - 1.10).

[0074] In one embodiment, the metal oxide is provided as a mixture of discrete magnesium oxide particles and discrete cerium oxide particles, each having any of the definitions shown above. In such an embodiment, the discrete single-phase particles of each oxide are prepared separately before being mixed with each other. Thus, the metal oxide can be regarded as a physical mixture of magnesium oxide and cerium oxide. Before combining the two M-loaded metal oxides, the metal M can be deposited on each metal oxide separately. Alternatively, the metal M can be deposited on the two metal oxides after combination.

[0075] In an alternative embodiment, the metal oxide is provided as a plurality of particles, at least some of which contain a mixture of magnesium oxide and cerium oxide, each having any of the definitions shown above. In such an embodiment, magnesium oxide and cerium oxide are co-synthesized to produce mixed-phase particles (i.e., a population of particles, at least some of which are not single-phase), and then the metal M is deposited thereon. Such a metal oxide can be regarded as a chemical mixture of magnesium oxide and cerium oxide.

[0076] The following paragraphs outline specific non-limiting embodiments of the catalytic material.

[0077] In one embodiment, the catalytic material comprises:

[0078] a) 40.0 - 99.9% w / w of a metal oxide, and

[0079] b) 0.01 - 30.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0080] wherein the metal oxide comprises magnesium oxide having a (111) crystal plane, and the (111) crystal plane forms at least 10% of the exposed surface of the magnesium oxide.

[0081] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0082] The average particle size of the metal M may be 0.5 - 100 nm.

[0083] In one embodiment, the catalytic material comprises:

[0084] a) 55.0 - 99.9% w / w of a metal oxide, and

[0085] b) 0.01 - 15.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0086] wherein the metal oxide comprises magnesia having a (111) crystal plane, and the (111) crystal plane forms at least 10% of the magnesia exposed surface.

[0087] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0088] The average particle size of the metal M may be 0.5 - 100 nm.

[0089] In one embodiment, the catalytic material comprises:

[0090] a) 80.0 - 98.5% w / w of a metal oxide, and

[0091] b) 1.5 - 7.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0092] wherein the metal oxide comprises magnesia having a (111) crystal plane, and the (111) crystal plane forms at least 10% of the magnesia exposed surface.

[0093] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0094] The average particle size of the metal M may be 2.0 - 20 nm.

[0095] In one embodiment, the catalytic material comprises:

[0096] a) 88.0 - 97.2% w / w of a metal oxide, and

[0097] b) 2.8 - 4.5% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0098] wherein the metal oxide comprises magnesia having a (111) crystal plane, and the (111) crystal plane forms at least 10% of the magnesia-exposed surface.

[0099] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0100] The average particle size of the metal M may be 2.0 - 20 nm.

[0101] In one embodiment, the catalytic material comprises:

[0102] a) 40.0 - 99.9% w / w of a metal oxide, and

[0103] b) 0.01 - 30.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0104] wherein the metal oxide comprises magnesia having a (111) crystal plane, and the (111) crystal plane forms at least 30% of the magnesia-exposed surface.

[0105] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0106] The average particle size of the metal M may be 0.5 - 100 nm.

[0107] In one embodiment, the catalytic material comprises:

[0108] a) 55.0 - 99.9% w / w of a metal oxide, and

[0109] b) 0.01 - 15.0% w / w of metal M, selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0110] wherein the metal oxide comprises magnesium oxide having a (111) crystal plane, and the (111) crystal plane forms at least 30% of the exposed surface of the magnesium oxide.

[0111] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0112] The average particle size of the metal M may be 0.5 - 100 nm.

[0113] In one embodiment, the catalytic material comprises:

[0114] a) 80.0 - 98.5% w / w of a metal oxide, and

[0115] b) 1.5 - 7.0% w / w of metal M, selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0116] wherein the metal oxide comprises magnesium oxide having a (111) crystal plane, and the (111) crystal plane forms at least 30% of the exposed surface of the magnesium oxide.

[0117] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0118] The average particle size of the metal M may be 2.0 - 20 nm.

[0119] In one embodiment, the catalytic material comprises:

[0120] a) 88.0 - 97.2% w / w of a metal oxide, and

[0121] b) 2.8 - 4.5% w / w of metal M, selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0122] wherein the metal oxide comprises magnesium oxide having a (111) crystal plane, and the (111) crystal plane forms at least 30% of the exposed surface of the magnesium oxide.

[0123] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0124] The average particle size of the metal M can be 2.0 - 20 nm.

[0125] In one embodiment, the catalytic material comprises:

[0126] a) 40.0 - 99.9% w / w of a metal oxide, and

[0127] b) 0.01 - 20.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0128] wherein the metal oxide comprises magnesium oxide having a (111) crystal plane, and the (111) crystal plane forms at least 10% of the exposed surface of the magnesium oxide.

[0129] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0130] The average particle size of the metal M can be 0.5 - 100 nm.

[0131] In one embodiment, the catalytic material comprises:

[0132] a) 80.0 - 98.5% w / w of a metal oxide, and

[0133] b) 1.5 - 7.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0134] wherein the metal oxide comprises magnesium oxide having a (111) crystal plane, and the (111) crystal plane forms at least 10% of the exposed surface of the magnesium oxide.

[0135] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0136] The average particle size of the metal M can be 2.0 - 20 nm.

[0137] In one embodiment, the catalytic material comprises:

[0138] a) 88.0 - 97.2% w / w of a metal oxide, and

[0139] b) 2.8 - 4.5% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0140] where the metal oxide comprises magnesium oxide having a (111) crystal plane, and the (111) crystal plane forms at least 10% of the exposed surface of the magnesium oxide.

[0141] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, where the promoter Q and the acidic zeolite have any of the definitions shown above.

[0142] The average particle size of the metal M may be 2.0 - 20 nm.

[0143] In one embodiment, the catalytic material comprises:

[0144] a) 40.0 - 99.9% w / w of a metal oxide, and

[0145] b) 0.01 - 20.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0146] where the metal oxide comprises magnesium oxide having a (111) crystal plane, and the (111) crystal plane forms at least 30% of the exposed surface of the magnesium oxide.

[0147] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, where the promoter Q and the acidic zeolite have any of the definitions shown above.

[0148] The average particle size of the metal M may be 0.5 - 100 nm.

[0149] In one embodiment, the catalytic material comprises:

[0150] a) 80.0 - 98.5% w / w of a metal oxide, and

[0151] b) 1.5 - 7.0% w / w of metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0152] wherein the metal oxide comprises magnesium oxide having a (111) crystal plane, and the (111) crystal plane forms at least 30% of the exposed surface of the magnesium oxide.

[0153] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0154] The average particle size of the metal M can be 2.0 - 20 nm.

[0155] In one embodiment, the catalytic material comprises:

[0156] a) 88.0 - 97.2% w / w of a metal oxide, and

[0157] b) 2.8 - 4.5% w / w of metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0158] wherein the metal oxide comprises magnesium oxide having a (111) crystal plane, and the (111) crystal plane forms at least 30% of the exposed surface of the magnesium oxide.

[0159] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0160] The average particle size of the metal M can be 2.0 - 20 nm.

[0161] In one embodiment, the catalytic material comprises:

[0162] a) 40.0 - 99.9% w / w of a metal oxide, and

[0163] b) 0.01 - 30.0% w / w of metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0164] wherein the metal oxide comprises magnesium oxide having a (111) crystal plane forming at least 10% of the exposed surface of the magnesium oxide and cerium oxide, suitably where the weight ratio of magnesium oxide to cerium oxide is 1:(0.1 - 10.0).

[0165] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0166] The average particle size of the metal M may be 0.5 - 100 nm.

[0167] In one embodiment, the catalytic material comprises:

[0168] a) 55.0 - 99.9% w / w of a metal oxide, and

[0169] b) 0.01 - 15.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0170] wherein the metal oxide comprises magnesia and ceria having a (111) crystal plane forming at least 10% of the magnesia exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.25 - 4.0).

[0171] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0172] The average particle size of the metal M may be 2.0 - 20 nm.

[0173] In one embodiment, the catalytic material comprises:

[0174] a) 80.0 - 98.5% w / w of a metal oxide, and

[0175] b) 1.5 - 7.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0176] wherein the metal oxide comprises magnesia and ceria having a (111) crystal plane forming at least 10% of the magnesia exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0177] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0178] The average particle size of the metal M may be 2.0 - 20 nm.

[0179] In one embodiment, the catalytic material comprises:

[0180] a) 88.0 - 97.2% w / w of a metal oxide, and

[0181] b) 2.8 - 4.5% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0182] wherein the metal oxide comprises magnesia and ceria having a (111) crystal plane forming at least 10% of the magnesia exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0183] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0184] The average particle size of the metal M may be 2.0 - 20 nm.

[0185] In one embodiment, the catalytic material comprises:

[0186] a) 40.0 - 99.9% w / w of a metal oxide, and

[0187] b) 0.01 - 30.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0188] wherein the metal oxide comprises magnesia and ceria having a (111) crystal plane forming at least 30% of the magnesia exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.1 - 10.0).

[0189] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0190] The average particle size of the metal M can be 0.5 - 100 nm.

[0191] In one embodiment, the catalytic material comprises:

[0192] a) 55.0 - 99.9% w / w of a metal oxide, and

[0193] b) 0.01 - 15.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0194] wherein the metal oxide comprises magnesia and ceria having a (111) crystal plane forming at least 30% of the magnesia exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.25 - 4.0).

[0195] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM - 5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0196] The average particle size of the metal M can be 2.0 - 20 nm.

[0197] In one embodiment, the catalytic material comprises:

[0198] a) 80.0 - 98.5% w / w of a metal oxide, and

[0199] b) 1.5 - 7.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0200] wherein the metal oxide comprises magnesia and ceria having a (111) crystal plane forming at least 30% of the magnesia exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0201] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM - 5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0202] The average particle size of the metal M can be 2.0 - 20 nm.

[0203] In one embodiment, the catalytic material comprises:

[0204] a) 88.0 - 97.2% w / w of a metal oxide, and

[0205] b) 2.8 - 4.5% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0206] wherein the metal oxide comprises magnesia and ceria having a (111) crystal plane forming at least 30% of the magnesia exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0207] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM - 5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0208] The average particle size of the metal M may be 2.0 - 20 nm.

[0209] In one embodiment, the catalytic material comprises:

[0210] a) 40.0 - 99.9% w / w of a metal oxide, and

[0211] b) 0.01 - 20.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0212] wherein the metal oxide comprises magnesia and ceria having a (111) crystal plane forming at least 10% of the magnesia exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.1 - 10.0).

[0213] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM - 5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0214] The average particle size of the metal M may be 0.5 - 100 nm.

[0215] In one embodiment, the catalytic material comprises:

[0216] a) 80.0 - 98.5% w / w of a metal oxide, and

[0217] b) 1.5 - 7.0% w / w of metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0218] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 10% of the magnesia exposed surface and cerium oxide, suitably where the weight ratio of magnesia to cerium oxide is 1:(0.50 - 2.0).

[0219] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0220] The average particle size of the metal M may be 2.0 - 20 nm.

[0221] In one embodiment, the catalytic material comprises:

[0222] a) 88.0 - 97.2% w / w of a metal oxide, and

[0223] b) 2.8 - 4.5% w / w of metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0224] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 10% of the magnesia exposed surface and cerium oxide, suitably where the weight ratio of magnesia to cerium oxide is 1:(0.50 - 2.0).

[0225] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0226] The average particle size of the metal M may be 2.0 - 20 nm.

[0227] In one embodiment, the catalytic material comprises:

[0228] a) 40.0 - 99.9% w / w of a metal oxide, and

[0229] b) 0.01 - 20.0% w / w of metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0230] wherein the metal oxide comprises magnesium oxide and cerium oxide having a (111) crystal plane forming at least 30% of the exposed surface of the magnesium oxide, suitably wherein the weight ratio of magnesium oxide to cerium oxide is 1:(0.1-10.0).

[0231] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75-1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01-20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0232] The average particle size of the metal M may be 0.5-100 nm.

[0233] In one embodiment, the catalytic material comprises:

[0234] a) 80.0-98.5% w / w of a metal oxide, and

[0235] b) 1.5-7.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0236] wherein the metal oxide comprises magnesium oxide and cerium oxide having a (111) crystal plane forming at least 30% of the exposed surface of the magnesium oxide, suitably wherein the weight ratio of magnesium oxide to cerium oxide is 1:(0.50-2.0).

[0237] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75-1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01-15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0238] The average particle size of the metal M may be 2.0-20 nm.

[0239] In one embodiment, the catalytic material comprises:

[0240] a) 88.0-97.2% w / w of a metal oxide, and

[0241] b) 2.8-4.5% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0242] wherein the metal oxide comprises magnesium oxide and cerium oxide having a (111) crystal plane forming at least 30% of the exposed surface of the magnesium oxide, suitably wherein the weight ratio of magnesium oxide to cerium oxide is 1:(0.50-2.0).

[0243] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0244] The average particle size of the metal M may be 2.0 - 20 nm.

[0245] In one embodiment, the catalytic material comprises:

[0246] a) 40.0 - 99.9% w / w of a metal oxide, and

[0247] b) 0.01 - 30.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0248] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 10% of the magnesia exposed surface and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the ceria exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.1 - 10.0).

[0249] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0250] The average particle size of the metal M may be 0.5 - 100 nm.

[0251] In one embodiment, the catalytic material comprises:

[0252] a) 55.0 - 99.9% w / w of a metal oxide, and

[0253] b) 0.01 - 15.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0254] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 10% of the magnesia exposed surface and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the ceria exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.25 - 4.0).

[0255] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0256] The average particle size of the metal M may be 0.5 - 100 nm.

[0257] In one embodiment, the catalytic material comprises:

[0258] a) 80.0 - 98.5% w / w of a metal oxide, and

[0259] b) 1.5 - 7.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0260] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 10% of the exposed surface of the magnesia and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the exposed surface of the ceria, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0261] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0262] The average particle size of the metal M may be 2.0 - 20 nm.

[0263] In one embodiment, the catalytic material comprises:

[0264] a) 88.0 - 97.2% w / w of a metal oxide, and

[0265] b) 2.8 - 4.5% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0266] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 10% of the exposed surface of the magnesia and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the exposed surface of the ceria, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0267] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0268] The average particle size of the metal M may be 2.0 - 20 nm.

[0269] In one embodiment, the catalytic material comprises:

[0270] a) 40.0 - 99.9% w / w of a metal oxide, and

[0271] b) 0.01 - 30.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0272] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 30% of the magnesia exposed surface and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the ceria exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.1 - 10.0).

[0273] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0274] The average particle size of the metal M may be 0.5 - 100 nm.

[0275] In one embodiment, the catalytic material comprises:

[0276] a) 55.0 - 99.9% w / w of a metal oxide, and

[0277] b) 0.01 - 15.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0278] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 30% of the magnesia exposed surface and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the ceria exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.25 - 4.0).

[0279] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0280] The average particle size of the metal M may be 0.5 - 100 nm.

[0281] In one embodiment, the catalytic material comprises:

[0282] a) 80.0 - 98.5% w / w of a metal oxide, and

[0283] b) 1.5 - 7.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0284] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 30% of the exposed surface of the magnesia and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the exposed surface of the ceria, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0285] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0286] The average particle size of the metal M may be 2.0 - 20 nm.

[0287] In one embodiment, the catalytic material comprises:

[0288] a) 88.0 - 97.2% w / w of a metal oxide, and

[0289] b) 2.8 - 4.5% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0290] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 30% of the exposed surface of the magnesia and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the exposed surface of the ceria, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0291] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0292] The average particle size of the metal M may be 2.0 - 20 nm.

[0293] In one embodiment, the catalytic material comprises:

[0294] a) 40.0 - 99.9% w / w of a metal oxide, and

[0295] b) 0.01 - 20.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo

[0296] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 10% of the exposed surface of the magnesia and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the exposed surface of the ceria, suitably wherein the weight ratio of magnesia to ceria is 1:(0.1 - 10.0).

[0297] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0298] The average particle size of the metal M may be 0.5 - 100 nm.

[0299] In one embodiment, the catalytic material comprises:

[0300] a) 80.0 - 98.5% w / w of a metal oxide, and

[0301] b) 1.5 - 7.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo

[0302] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 10% of the exposed surface of the magnesia and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the exposed surface of the ceria, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0303]

[0304] ​The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0305] The average particle size of the metal M may be 2.0 - 20 nm.

[0306] In one embodiment, the catalytic material comprises:

[0307] a) 88.0 - 97.2% w / w of a metal oxide, and

[0308] b) 2.8 - 4.5% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0309] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 10% of the magnesia exposed surface and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the ceria exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0310] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0311] The average particle size of the metal M may be 2.0 - 20 nm.

[0312] In one embodiment, the catalytic material comprises:

[0313] a) 40.0 - 99.9% w / w of a metal oxide, and

[0314] b) 0.01 - 20.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0315] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 30% of the magnesia exposed surface and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the ceria exposed surface, suitably wherein the weight ratio of magnesia to ceria is 1:(0.1 - 10.0).

[0316] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0317] The average particle size of the metal M may be 0.5 - 100 nm.

[0318] In one embodiment, the catalytic material comprises:

[0319] a) 80.0 - 98.5% w / w of a metal oxide, and

[0320] b) 1.5 - 7.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0321] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 30% of the exposed surface of magnesia and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the exposed surface of ceria, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0322] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0323] The average particle size of the metal M may be 2.0 - 20 nm.

[0324] In one embodiment, the catalytic material comprises:

[0325] a) 88.0 - 97.2% w / w of a metal oxide, and

[0326] b) 2.8 - 4.5% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0327] wherein the metal oxide comprises magnesia having a (111) crystal plane forming at least 30% of the exposed surface of magnesia and ceria having a (111) crystal plane forming at least 40% (suitably at least 80%) of the exposed surface of ceria, suitably wherein the weight ratio of magnesia to ceria is 1:(0.50 - 2.0).

[0328] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0329] The average particle size of the metal M may be 2.0 - 20 nm.

[0330] It should be understood that in any of the foregoing specific, non-limiting embodiments, the metal oxide may have any of the alternative definitions outlined above.

[0331] It should be understood that in any of the foregoing specific, non-limiting embodiments, the metal M may have any of the alternative definitions outlined above.

[0332] Preparation of catalytic material

[0333] In a second aspect, the present invention provides a method for preparing a catalytic material according to the first aspect, the method comprising:

[0334] a) providing a metal oxide as defined herein, and

[0335] b) depositing a metal M on the metal oxide, wherein M is as defined herein,

[0336] c) optionally reducing or partially reducing the product resulting from step b).

[0337] As discussed above, the metal M of the catalytic material may be present as an oxide or in metallic form or both, depending on whether the catalytic material is provided in a non-reduced state or in a reduced / partially reduced state. In one embodiment, the method further comprises an optional step c) of reducing or partially reducing the product resulting from step b). The optional step c) may include heating the product of step b) at a temperature of 200 - 600 °C for 0.5 to 10 hours in a reducing atmosphere. Suitably, the optional step c) includes heating the product of step b) at a temperature of 300 - 500 °C for 2 to 6 hours in an atmosphere of 1 - 20 vol% hydrogen (such as 3 - 8 vol%) in helium.

[0338] The metal M may be deposited on the metal oxide by chemical vapor deposition, wet impregnation or ball milling. Suitably, the metal M is deposited on the metal oxide by chemical vapor deposition. Suitably, the amount of metal M used is such that the resulting catalytic material has an amount of metal M as discussed above with respect to the first aspect.

[0339] In one embodiment, the method further comprises depositing promoter Q as defined above on the product produced in step b). Such a step occurs optionally before step c). Promoter Q is suitably deposited on the product produced in step b) by wet impregnation. Suitably, the amount of Q is such that the resulting catalytic material has an amount of Q as discussed above with respect to the first aspect.

[0340] In one embodiment, the method further comprises mixing the product produced in step b) with an acidic zeolite as defined above. Such a step occurs before the optional step c). Before mixing with the product produced in step b), the acidic zeolite may be subjected to a heat treatment at a temperature of 200 - 500 °C for 1 to 8 hours and then optionally dried in a vacuum oven.

[0341] The method may use both promoter Q and the acidic zeolite. Suitably, promoter Q is deposited on the product produced in step b), and then the resulting product (including Q) is mixed with the acidic zeolite.

[0342] The method may use preformed magnesium oxide having an exposed (111) crystal plane.

[0343] Alternatively, the method includes steps for preparing the magnesium oxide. In one embodiment, step a) includes preparing magnesium oxide having an exposed (111) crystal plane by hydrothermal synthesis. Suitably, an aqueous solution containing a magnesium salt (such as magnesium chloride) and a suitable surfactant (such as benzoic acid) is treated with a base (such as NaOH) and then subjected to hydrothermal conditions to produce a solid product, and then the solid product is calcined to produce magnesium oxide having an exposed (111) crystal plane.

[0344] In one embodiment, the metal oxide provided in step a) consists of magnesium oxide having an exposed (111) crystal plane.

[0345] In an alternative embodiment, the metal oxide provided in step a) comprises magnesium oxide and cerium oxide, wherein the magnesium oxide has an exposed (111) crystal plane. As discussed above with respect to the first aspect of the present invention, the cerium oxide may comprise an exposed (100) crystal plane. The cerium oxide having an exposed (100) crystal plane used in step a) may be preformed or may be prepared by hydrothermal synthesis. In such an embodiment, the mixture of magnesium oxide and cerium oxide provided in step a) may be provided as a physical mixture, a chemical mixture, or a mixture of both. In embodiments comprising magnesium oxide and cerium oxide, the relative amounts of the two oxides in the resulting product are as described above with respect to the first aspect.

[0346] A physical mixture can be prepared by mixing preformed magnesium oxide and cerium oxide samples. Thus, the resulting physical mixture can contain a mixture of discrete single-phase magnesium oxide particles and discrete single-phase cerium oxide particles.

[0347] A chemical mixture can be prepared by subjecting a mixture of a magnesium oxide precursor and a cerium oxide precursor to conditions sufficient to form a mixture of magnesium oxide and cerium oxide. For example, an aqueous mixture containing a magnesium salt (such as magnesium chloride) and a cerium salt (such as cerium nitrate) can be treated with a base (such as NaOH) and then subjected to hydrothermal conditions to produce a solid product, which is then calcined to produce a chemical mixture of magnesium oxide and cerium oxide. Thus, the resulting chemical mixture can contain a variety of mixed-phase particles (i.e., particle populations, at least some of which are not single-phase).

[0348] In a particular embodiment, the method further comprises the step of mixing (e.g., physically mixing) the catalytic material (i.e., the product of step b) or step c) if employed, or any intermediate step) with other catalytic materials. Suitably, the other catalytic materials comprise:

[0349] Metal oxides, wherein the metal oxides are:

[0350] Magnesium oxide having any of the definitions shown above with respect to the first aspect, or

[0351] Cerium oxide having any of the definitions shown above with respect to the first aspect, or

[0352] Magnesium oxide and cerium oxide, one or both of which having any of the definitions shown above with respect to the first aspect, and

[0353] Metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof.

[0354] The other catalytic materials may additionally comprise promoter Q and / or acidic zeolite. The magnesium oxide, cerium oxide, metal M, promoter Q, and acidic zeolite (and their respective amounts) of the other catalytic materials are suitably as defined above with respect to the first aspect of the present invention. In particular, the suitable and preferred definitions of the magnesium oxide, cerium oxide, M, Q, and acidic zeolite in the context of the first aspect of the present invention are also the suitable and preferred definitions of the magnesium oxide, cerium oxide, M, Q, and acidic zeolite of the other catalytic materials.

[0355] Suitably, the metal oxide of the other catalytic materials is cerium oxide containing exposed (100) crystal planes.

[0356] Specific non-limiting examples of the other catalytic materials are outlined in the following paragraphs.

[0357] In one embodiment, the other catalytic material comprises:

[0358] a) 40.0 - 99.9% w / w cerium oxide, wherein the (100) crystal plane forms at least 20% of the cerium oxide exposed surface.

[0359] b) 0.01 - 20.0% w / w of metal M, selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0360] In one embodiment, the other catalytic material comprises:

[0361] a) 80.0 - 98.5% w / w cerium oxide, wherein the (100) crystal plane forms at least 40% of the cerium oxide exposed surface.

[0362] b) 1.5 - 7.0% w / w of metal M, wherein M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo.

[0363] In one embodiment, the other catalytic material comprises:

[0364] a) 88.0 - 97.2% w / w cerium oxide, wherein the (100) crystal plane forms at least 60% of the cerium oxide exposed surface.

[0365] b) 2.8 - 4.5% w / w of metal M, wherein M is Ru.

[0366] Suitably, the other catalytic material further comprises a promoter Q (e.g., Cs) and / or an acidic zeolite (e.g., ZSM - 5), in an amount as described above for the first aspect.

[0367] When the metal oxide provided in step a) of the method consists of magnesium oxide comprising an exposed (111) crystal plane, it is particularly suitable to use the other catalytic material. For example, the method may include:

[0368] a) Providing a metal oxide consisting of magnesium oxide comprising an exposed (111) crystal plane, wherein the (111) crystal plane forms at least 40% of the magnesium oxide exposed surface.

[0369] b) i) Depositing metal M on the metal oxide, wherein M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo

[0370] and wherein the amounts of the metal oxide and M are such that the catalytic material comprises:

[0371] 80.0 - 98.5% w / w of the metal oxide, and

[0372] b) 1.5 - 7.0% w / w of said metal M,

[0373] b) ii) depositing promoter Q on the product produced in step b) i), where Q is Cs and the molar ratio of M:Q is 1:(0.5 - 1.5).

[0374] c) Optionally reducing or partially reducing the product produced in step b) ii),

[0375] d) Mixing the catalytic material produced in step b) ii) (or c)) with other catalytic materials, where said other catalytic materials comprise:

[0376] 80.0 - 98.5% w / w of cerium oxide, where the (100) crystal plane forms at least 40% of the exposed surface of the cerium oxide, and

[0377] 1.5 - 7.0% w / w of metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo.

[0378] One or both of said catalytic material and other catalytic materials may also comprise an acidic zeolite as defined above and / or a promoter Q as defined above.

[0379] If other catalytic materials are used, the catalytic material produced in step b) (or c)) is mixed with said other catalyst materials such that in the resulting product, the weight ratio of the metal oxide provided in step a) (e.g., magnesium oxide) to the metal oxide of said other catalytic materials (e.g., cerium oxide) is 1:(0.1 - 10.0). Suitably, in the resulting product, the weight ratio of the metal oxide provided in step a) (e.g., magnesium oxide) to the metal oxide of said other catalytic materials (e.g., cerium oxide) is 1:(0.25 - 4.0). More suitably, in the resulting product, the weight ratio of the metal oxide provided in step a) (e.g., magnesium oxide) to the metal oxide of said other catalytic materials (e.g., cerium oxide) is 1:(0.50 - 2.0). Even more suitably, in the resulting product, the weight ratio of the metal oxide provided in step a) (e.g., magnesium oxide) to the metal oxide of said other catalytic materials (e.g., cerium oxide) is 1:(0.75 - 1.25). Most suitably, in the resulting product, the weight ratio of the metal oxide provided in step a) (e.g., magnesium oxide) to the metal oxide of said other catalytic materials (e.g., cerium oxide) is 1:(0.90 - 1.10).

[0380] In a third aspect, the present invention provides a catalytic material obtainable, directly obtainable or obtainable by a method according to the second aspect.

[0381] It should be understood that the features of the second and third aspects of the present invention (e.g., metal oxides, M, Q, acidic zeolites, and their respective amounts) can have any of the definitions shown for the same features of the first aspect of the present invention above. The suitable, preferred, and optional definitions of the first aspect of the present invention are also regarded as the suitable, preferred, and optional definitions of the second and third aspects of the present invention.

[0382] Catalytic decomposition of ammonia

[0383] In a fourth aspect, the present invention provides a method for catalytic decomposition of ammonia, the method comprising the step of contacting ammonia with a catalytic material, the catalytic material comprising:

[0384] a) a metal oxide, which comprises:

[0385] i) magnesium oxide comprising an exposed (111) crystal plane, or

[0386] ii) cerium oxide, or

[0387] iii) magnesium oxide and cerium oxide comprising an exposed (111) crystal plane;

[0388] b) a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof.

[0389] The (111) crystal plane of magnesium oxide is polar because it contains alternating layers of positively charged Mg 2+ and negatively charged O 2- ions, such that the outermost surface has a net charge. This is in contrast to the non-polar (110) and (100) crystal planes of magnesium oxide, which contain equal mixtures of Mg 2+ and O 2- ions, such that the outermost surface is net neutral. Without wishing to be bound by theory, the inventors believe that the polar (111) crystal plane of magnesium oxide produces a significantly enhanced proton mobility, which improves bond activation and proton removal during the ammonia decomposition reaction. Suitably, the (111) crystal plane forms at least 10% of the exposed surface of magnesium oxide. For example, the amount of the (111) crystal plane in magnesium oxide can be determined by integrating the characteristic peaks in nuclear magnetic resonance. More suitably, the (111) crystal plane forms at least 20% of the exposed surface of magnesium oxide. Even more suitably, the (111) crystal plane forms at least 30% of the exposed surface of magnesium oxide. Still more suitably, the (111) crystal plane forms at least 40% of the exposed surface of magnesium oxide. Still even more suitably, the (111) crystal plane forms 40 - 50% of the exposed surface of magnesium oxide. Most suitably, the (111) crystal plane forms 44 - 48% of the exposed surface of magnesium oxide.

[0390] A method employed by the inventors produced magnesium oxide in which the (111) crystal plane forms approximately 46% of the exposed surface of the magnesium oxide. However, the inventors have shown that the presence of a large amount of (111) crystal planes has a significant beneficial effect on the catalytic performance of the material, such that magnesium oxide with an even higher amount of (111) crystal planes can be even more catalytically active. Thus, in any of the above embodiments, the (111) crystal plane can form up to 60%, 70%, 80%, 90% or 100% of the exposed surface of the magnesium oxide. For example, such an increased amount of (111) crystal planes can be present in magnesium oxide particles having an octahedral form, where all 8 faces are (111) crystal planes.

[0391] The magnesium oxide is suitably in the form of nanoparticles (i.e., particles in which the largest dimension is less than 1 micrometer). The average particle size of the nanoparticles (based on the largest dimension of each particle) is suitably 50 to 500 nm, more suitably 100 to 250 nm. The nanoparticles can have various forms, but are typically provided as flakes (e.g., hexagonal flakes) having upper and lower (111) crystal planes and a thickness of 1 to 20 nm, suitably 2 to 15 nm. Alternatively, the nanoparticles can have the above-mentioned octahedral form.

[0392] Suitably, the magnesium oxide has a periclase crystal structure.

[0393] The cerium oxide can comprise exposed (100) crystal planes. The cubic and rod-like morphologies of cerium oxide contain an increased amount of polar (100) crystal planes compared to the polycrystalline form. Thus, the cerium oxide suitably comprises exposed (100) crystal planes. More suitably, the (100) crystal plane forms at least 20% of the exposed surface of the cerium oxide. For example, the amount of (100) crystal planes in the cerium oxide can be determined by integration of characteristic peaks in nuclear magnetic resonance. Even more suitably, the (100) crystal plane forms at least 40% of the exposed surface of the cerium oxide. Still more suitably, the (100) crystal plane forms at least 60% of the exposed surface of the cerium oxide. Still more suitably, the (100) crystal plane forms at least 80% of the exposed surface of the cerium oxide. Yet more suitably, the (100) crystal plane forms at least 85% of the exposed surface of the cerium oxide. Most suitably, the (100) crystal plane forms 88 to 96% of the exposed surface of the cerium oxide. Theoretically, the (100) crystal plane can form up to 50% of the exposed surface of cerium oxide having a rod-like morphology. In contrast, the (100) crystal plane theoretically forms all of the exposed surface of cerium oxide having a cubic morphology.

[0394] In one embodiment, the cerium oxide is present as a mixture of cubic and rod-like morphologies.

[0395] In one embodiment, the cerium oxide is present mainly as a cubic morphology.

[0396] The cerium oxide is suitably in the form of nanoparticles (i.e., particles in which the largest dimension is less than 1 micron). The average particle size of the nanoparticles (based on the largest dimension of each particle) is suitably 5 to 50 nm, more suitably 10 to 30 nm. The nanoparticles can have various forms, but are typically provided in the form of the above-mentioned rod-like and / or cubic forms.

[0397] In one embodiment, the metal oxide comprises, consists essentially of, or consists of magnesium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

[0398] In one embodiment, the metal oxide comprises, consists essentially of, or consists of cerium oxide.

[0399] In one embodiment, the metal oxide comprises, consists essentially of, or consists of magnesium oxide comprising an exposed (111) crystal plane and cerium oxide.

[0400] The metal M is typically applied to the metal oxide by chemical vapor deposition, wet impregnation, or ball milling. Thus, it should be understood that the metal M is distributed (i.e., dispersed) on the surface of the metal oxide.

[0401] The metal M can be present in the catalytic material as an oxide (e.g., ruthenium oxide), in metallic form (e.g., metallic ruthenium), or both. If the catalytic material has not undergone a reduction treatment as part of the manufacturing process, at least a portion of the metal M will be present as an oxide. If the catalytic material has undergone a reduction treatment as part of the manufacturing process, at least some of the metal M will be present in metallic form. In one embodiment, greater than 90% (or all) of the metal M is present as an oxide. Alternatively, greater than 90% (or all) of the metal M is present in metallic form.

[0402] The reduction treatment can also be applied directly before ammonia decomposition (regardless of whether the reduction treatment is part of the manufacturing process). Thus, in one embodiment, before contacting the catalytic material with ammonia, the catalytic material is heated in a reducing atmosphere at a temperature of 200 to 600 °C for 0.5 to 10 hours. Suitably, before contacting the catalytic material with ammonia, the catalytic material is heated in helium in an atmosphere of 1-20 vol% hydrogen (e.g., 3-8 vol%) at a temperature of 300-500 °C for 2 to 6 hours.

[0403] The average particle size of the metal M (regardless of whether it is present as an oxide or in metallic form) is suitably 0.5 to 100 nm. The average particle size of the metal M can be determined, for example, by transmission electron microscopy. More suitably, the average particle size of the metal M is 2-20 nm.

[0404] In one embodiment, the metal M is selected from the group consisting of Ru, Fe, and mixtures thereof. In a particularly preferred embodiment, the metal M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo. In a particularly preferred embodiment, the metal M is only Ru.

[0405] In another embodiment, the metal M is a mixture of Co and Mo.

[0406] In one embodiment, the catalytic material comprises:

[0407] 0.01 - 30.0% w / w of the metal M, and

[0408] 40.0 - 99.9% w / w of the metal oxide.

[0409] The amount of the metal M refers to the amount of element M, which can be determined by inductively coupled plasma optical emission spectrometry (ICP - OES). The metal M exists as an oxide or in metallic form. Suitably, the catalytic material comprises:

[0410] 0.01 - 20.0% w / w of the metal M, and

[0411] 40.0 - 99.9% w / w of the metal oxide.

[0412] More suitably, the catalytic material comprises:

[0413] 0.01 to 15.0% w / w of the metal M, and

[0414] 55.0 - 99.9% w / w of the metal oxide.

[0415] Even more suitably, the catalytic material comprises:

[0416] 0.5 - 10.0% w / w of the metal M, and

[0417] 70.0 - 99.5% w / w of the metal oxide.

[0418] Still more suitably, the catalytic material comprises:

[0419] 1.5 - 7.0% w / w of the metal M, and

[0420] 80.0 - 98.5% w / w of the metal oxide.

[0421] Still even more suitably, the catalytic material comprises:

[0422] 2.5 - 6.0% w / w of the metal M, and

[0423] 85.0 - 97.5% w / w of said metal oxide.

[0424] Most suitably, the catalytic material comprises:

[0425] 2.8 - 4.5% w / w of said metal M, and

[0426] 88.0 - 97.2% w / w of said metal oxide.

[0427] The catalytic material may further comprise promoter Q. The addition of the promoter significantly enhances the activity of the catalytic material. Promoter Q can be incorporated into the catalytic material by wet impregnation, which is familiar to those skilled in the art. Suitably, promoter Q is selected from the group consisting of Cs, K, Ba, and mixtures of two or more thereof. More suitably, Q is selected from the group consisting of Cs, K, and mixtures thereof. Most suitably, Q is Cs.

[0428] If the catalytic material contains promoter Q, the molar ratio of metal M to Q (i.e., M:Q) can be 1:(0.1 - 3). Suitably, the molar ratio of M:Q is 1:(0.5 - 1.5). More suitably, the molar ratio of M:Q is 1:(0.75 - 1.25).

[0429] The catalytic material may further comprise acidic zeolite. The catalytic material may contain 0.01 - 50.0% w / w of said acidic zeolite. Suitably, the catalytic material contains 0.01 - 20.0% w / w of said acidic zeolite. In a specific embodiment, the catalytic material is ZSM - 5.

[0430] The following paragraphs outline specific non - limiting embodiments of the catalytic material used in the fourth aspect of the present invention.

[0431] In one embodiment, the catalytic material comprises:

[0432] a) 40.0 - 99.9% w / w of metal oxide, and

[0433] b) 0.01 - 20.0% w / w of metal M, selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0434] wherein the metal oxide comprises cerium oxide.

[0435] The catalytic material may further comprise promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM - 5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0436] The average particle size of the metal M can be 0.5 - 100 nm.

[0437] In one embodiment, the catalytic material comprises:

[0438] a) 80.0 - 98.5% w / w of a metal oxide, and

[0439] b) 1.5 - 7.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0440] wherein the metal oxide comprises cerium oxide.

[0441] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0442] The average particle size of the metal M can be 2.0 - 20 nm.

[0443] In one embodiment, the catalytic material comprises:

[0444] a) 88.0 - 97.2% w / w of a metal oxide, and

[0445] b) 2.8 - 4.5% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0446] wherein the metal oxide comprises cerium oxide.

[0447] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0448] The average particle size of the metal M can be 2.0 - 20 nm.

[0449] In one embodiment, the catalytic material comprises:

[0450] a) 40.0 - 99.9% w / w of a metal oxide, and

[0451] b) 0.01 - 20.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0452] wherein the metal oxide comprises cerium oxide having an exposed (100) crystal plane, and the (100) crystal plane forms at least 40% of the exposed surface of the cerium oxide.

[0453] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 to 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0454] The average particle size of the metal M may be from 0.5 to 100 nm.

[0455] In one embodiment, the catalytic material comprises:

[0456] a) 80.0 - 98.5% w / w of a metal oxide, and

[0457] b) 1.5 - 7.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0458] wherein the metal oxide comprises cerium oxide having an exposed (100) crystal plane, and the (100) crystal plane forms at least 40% of the exposed surface of the cerium oxide.

[0459] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0460] The average particle size of the metal M may be from 2.0 to 20 nm.

[0461] In one embodiment, the catalytic material comprises:

[0462] a) 88.0 - 97.2% w / w of a metal oxide, and

[0463] b) 2.8 - 4.5% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0464] wherein the metal oxide comprises cerium oxide having an exposed (100) crystal plane, and the (100) crystal plane forms at least 40% of the exposed surface of the cerium oxide.

[0465] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0466] The average particle size of the metal M may be 2.0 - 20 nm.

[0467] In one embodiment, the catalytic material comprises:

[0468] a) 40.0 - 99.9% w / w of a metal oxide, and

[0469] b) 0.01 - 20.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0470] wherein the metal oxide comprises cerium oxide having an exposed (100) crystal plane, where the (100) crystal plane forms at least 40% of the exposed surface of the cerium oxide.

[0471] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0472] The average particle size of the metal M may be 0.5 - 100 nm.

[0473] In one embodiment, the catalytic material comprises:

[0474] a) 80.0 - 98.5% w / w of a metal oxide, and

[0475] b) 1.5 - 7.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0476] wherein the metal oxide comprises cerium oxide having an exposed (100) crystal plane, where the (100) crystal plane forms at least 40% of the exposed surface of the cerium oxide.

[0477] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0478] The average particle size of the metal M can be 2.0 - 20 nm.

[0479] In one embodiment, the catalytic material comprises:

[0480] a) 88.0 - 97.2% w / w of a metal oxide, and

[0481] b) 2.8 - 4.5% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0482] where the metal oxide comprises cerium oxide having an exposed (100) crystal face, where the (100) crystal face forms at least 40% of the exposed surface of the cerium oxide.

[0483] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, where the promoter Q and the acidic zeolite have any of the definitions shown above.

[0484] The average particle size of the metal M can be 2.0 - 20 nm.

[0485] In one embodiment, the catalytic material comprises:

[0486] a) 40.0 - 99.9% w / w of a metal oxide, and

[0487] b) 0.01 - 20.0% w / w of a metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0488] where the metal oxide comprises cerium oxide having an exposed (100) crystal face, where the (100) crystal face forms at least 60% of the exposed surface of the cerium oxide.

[0489] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, where the promoter Q and the acidic zeolite have any of the definitions shown above.

[0490] The average particle size of the metal M can be 0.5 - 100 nm.

[0491] In one embodiment, the catalytic material comprises:

[0492] a) 80.0 - 98.5% w / w of a metal oxide, and

[0493] b) 1.5 - 7.0% w / w of metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0494] wherein the metal oxide comprises cerium oxide having an exposed (100) crystal plane, and the (100) crystal plane forms at least 60% of the exposed surface of the cerium oxide.

[0495] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM - 5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0496] The average particle size of the metal M may be 2.0 - 20 nm.

[0497] In one embodiment, the catalytic material comprises:

[0498] a) 88.0 - 97.2% w / w of a metal oxide, and

[0499] b) 2.8 - 4.5% w / w of metal M, where M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo,

[0500] wherein the metal oxide comprises cerium oxide having an exposed (100) crystal plane, and the (100) crystal plane forms at least 60% of the exposed surface of the cerium oxide.

[0501] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM - 5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0502] The average particle size of the metal M may be 2.0 - 20 nm.

[0503] In one embodiment, the catalytic material comprises:

[0504] a) 40.0 - 99.9% w / w of a metal oxide, and

[0505] b) 0.01 - 20.0% w / w of metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0506] wherein the metal oxide comprises cerium oxide having an exposed (100) crystal plane, and the (100) crystal plane forms at least 80% of the exposed surface of the cerium oxide.

[0507] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 20.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0508] The average particle size of the metal M may be 0.5 - 100 nm.

[0509] In one embodiment, the catalytic material comprises:

[0510] a) 80.0 - 98.5% w / w of a metal oxide, and

[0511] b) 1.5 - 7.0% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0512] wherein the metal oxide comprises cerium oxide having an exposed (100) crystal plane, and the (100) crystal plane forms at least 80% of the exposed surface of the cerium oxide.

[0513] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 15.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0514] The average particle size of the metal M may be 2.0 - 20 nm.

[0515] In one embodiment, the catalytic material comprises:

[0516] a) 88.0 - 97.2% w / w of a metal oxide, and

[0517] b) 2.8 - 4.5% w / w of a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0518] wherein the metal oxide comprises cerium oxide having an exposed (100) crystal plane, and the (100) crystal plane forms at least 80% of the exposed surface of the cerium oxide.

[0519] The catalytic material may further comprise a promoter Q (such as Cs) such that the molar ratio of M:Q is 1:(0.75 - 1.25), and / or an acidic zeolite (such as ZSM-5) in an amount of 0.01 - 8.0% w / w, wherein the promoter Q and the acidic zeolite have any of the definitions shown above.

[0520] The average particle size of the metal M can be 2.0 - 20 nm.

[0521] It should be understood that in any of the foregoing specific, non - limiting embodiments, the metal oxide can have any of the alternative definitions outlined above with respect to the first to fourth aspects of the present invention.

[0522] It should be understood that in any of the foregoing specific, non - limiting embodiments, the metal M can have any of the alternative definitions outlined above with respect to the first to fourth aspects of the present invention.

[0523] In a particularly suitable embodiment, the catalytic material used in the fourth aspect is the same as the catalytic material of the first or third aspect.

[0524] It should be understood that the characteristics of the catalytic material used in the fourth aspect of the present invention (e.g., metal oxide, M, Q, acidic zeolite, and their respective amounts) can have any of the definitions shown for the same characteristics of the first aspect of the present invention. The suitable, preferred, and optional definitions of the first aspect of the present invention are also regarded as the suitable, preferred, and optional definitions of the fourth aspect of the present invention.

[0525] The catalytic method can be carried out under batch conditions or continuous - flow conditions.

[0526] The ammonia in contact with the catalytic material can be in liquid or gaseous form. Water (in liquid or gaseous form) can also be present.

[0527] In one embodiment, the ammonia is in liquid form and the catalytic process is carried out under batch conditions. The liquid ammonia is suitably present as an aqueous solution of 10 - 50 vol% ammonia.

[0528] In another embodiment, the ammonia is in gaseous form and the catalytic process is carried out under continuous - flow conditions in a fixed bed of the catalytic material.

[0529] The catalytic process can suitably be carried out in the presence of molecular oxygen. The inventors surprisingly found that the thermodynamic limit of ammonia decomposition can be overcome by adding a certain amount of O2 to partially consume hydrogen in a steady state. In one embodiment, the molar ratio of NH3:O2 is from 1:0.01 to 1:0.75. More suitably, the molar ratio of NH3:O2 is from 1:0.05 to 1:0.43. Molecular oxygen is suitably co - fed into the reaction together with ammonia. More suitably, the catalytic process is carried out under continuous - flow conditions, and molecular oxygen is co - fed into the reaction together with gaseous ammonia. The gaseous ammonia can be provided at a pressure of 0.001 to 100 bar.

[0530] The catalytic process can be carried out at a temperature of 150 - 900 °C. Suitably, the catalytic process is carried out at a temperature of 200 - 750 °C. More suitably, the catalytic process is carried out at a temperature of 250 - 550 °C. Even more suitably, the catalytic method is carried out at a temperature of 350 - 500 °C. Most suitably, the catalytic method is carried out at a temperature of 425 - 475 °C.

[0531] The catalytic method is suitably carried out at a WHSV of 5000 - 35000 mL g cat -1 h -1 More suitably, the catalytic method is carried out at a WHSV of 8000 - 32000 mL g cat -1 h -1 of the WHSV.

[0532] The following numbered statements 1 to 116 are not claims but are used to define specific aspects and embodiments of the claimed invention:

[0533] 1. A catalytic material comprising:

[0534] a) a metal oxide, and

[0535] b) a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof,

[0536] wherein the metal oxide comprises magnesium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

[0537] 2. The catalytic material according to statement 1, wherein the (111) crystal plane forms at least 10% of the exposed surface of the magnesium oxide.

[0538] 3. The catalytic material according to statement 1, wherein the (111) crystal plane forms at least 20% of the exposed surface of the magnesium oxide.

[0539] 4. The catalytic material according to statement 1, wherein the (111) crystal plane forms at least 30% of the exposed surface of the magnesium oxide.

[0540] 5. The catalytic material according to statement 1, wherein the (111) crystal plane forms at least 40% of the exposed surface of the magnesium oxide.

[0541] 6. The catalytic material according to statement 1, wherein the (111) crystal plane forms 40 - 50% of the exposed surface of the magnesium oxide.

[0542] 7. The catalytic material according to any of the preceding statements, wherein the (111) crystal plane forms more than 90% of the exposed surface of the magnesium oxide.

[0543] 8. The catalytic material according to any one of the foregoing statements, wherein the magnesium oxide is provided as nanoparticles.

[0544] 9. The catalytic material according to statement 8, wherein the nanoparticles have an average size of 100 - 250 nm.

[0545] 10. The catalytic material according to any one of the foregoing statements, wherein the metal M is selected from the group consisting of Ru, Fe, and mixtures thereof.

[0546] 11. The catalytic material according to any one of the foregoing statements, wherein the metal M is Ru.

[0547] 12. The catalytic material according to any one of the foregoing statements, wherein the catalytic material comprises:

[0548] 0.01 - 30.0% w / w of the metal M, and

[0549] 40.0 - 99.9% w / w of the metal oxide.

[0550] 13. The catalytic material according to any one of the foregoing statements, wherein the catalytic material comprises:

[0551] 0.01 - 15.0% w / w of the metal M, and

[0552] 55.0 - 99.9% w / w of the metal oxide.

[0553] 14. The catalytic material according to any one of the foregoing statements, wherein the catalytic material comprises:

[0554] 1.5 - 7.0% w / w of the metal M, and

[0555] 80.0 - 98.5% w / w of the metal oxide.

[0556] 15. The catalytic material according to any one of the foregoing statements, wherein the catalytic material comprises:

[0557] 2.5 - 6.0% w / w of the metal M, and

[0558] 85.0 - 97.5% w / w of the metal oxide.

[0559] 16. The catalytic material according to any one of the foregoing statements, wherein the metal M is distributed on the surface of the metal oxide.

[0560] 17. The catalytic material according to any one of the foregoing statements, wherein the metal M has an average particle size of 0.5 - 100 nm.

[0561] 18. The catalytic material according to any one of the foregoing statements, wherein the metal M has an average particle size of 2.0 - 20 nm.

[0562] 19. The catalytic material according to any one of the foregoing statements, which further comprises a promoter, Q.

[0563] 20. The catalytic material according to statement 19, wherein the Q is selected from the group consisting of Cs, K, Ba, and mixtures of two or more thereof.

[0564] 21. The catalytic material according to statement 19, wherein the Q is selected from the group consisting of Cs, K, and mixtures thereof.

[0565] 22. The catalytic material according to statement 19, wherein the Q is Cs.

[0566] 23. The catalytic material according to any one of statements 19 to 22, wherein the molar ratio of M:Q is 1:(0.1 - 3).

[0567] 24. The catalytic material according to any one of statements 19 to 22, wherein the molar ratio of M:Q is 1:(0.5 - 1.5).

[0568] 25. The catalytic material according to any one of statements 19 to 22, wherein the molar ratio of M:Q is 1:(0.75 - 1.25).

[0569] 26. The catalytic material according to any one of the foregoing statements, which further comprises an acidic zeolite.

[0570] 27. The catalytic material according to statement 26, wherein the acidic zeolite is ZSM - 5.

[0571] 28. The catalytic material according to statement 26 or 27, wherein the catalytic material comprises 0.01 - 50% w / w of the acidic zeolite.

[0572] 29. The catalytic material according to statement 26 or 27, wherein the catalytic material comprises 0.01 - 20% w / w of the acidic zeolite.

[0573] 30. The catalytic material according to any one of the foregoing statements, wherein the metal oxide consists of magnesium oxide.

[0574] 31. The catalytic material according to any one of statements 1 to 29, wherein the metal oxide comprises magnesium oxide and cerium oxide, wherein the magnesium oxide comprises an exposed (111) crystal plane.

[0575] 32. The catalytic material according to statement 31, wherein the cerium oxide comprises an exposed (100) crystal plane.

[0576] 33. The catalytic material according to statement 32, wherein the (100) crystal plane forms at least 20% of the exposed surface of magnesium oxide.

[0577] 34. The catalytic material according to statement 32, wherein the (100) crystal plane forms at least 40% of the exposed surface of magnesium oxide.

[0578] 35. The catalytic material according to statement 32, wherein the (100) crystal plane forms at least 60% of the exposed surface of magnesium oxide.

[0579] 36. The catalytic material according to statement 32, wherein the (100) crystal plane forms at least 80% of the exposed surface of magnesium oxide.

[0580] 37. The catalytic material according to statement 32, wherein the (100) crystal plane forms at least 85% of the exposed surface of magnesium oxide.

[0581] 38. The catalytic material according to any one of statements 31 to 37, wherein the cerium oxide exists as a mixture of cubic and rod-like morphologies.

[0582] 39. The catalytic material according to any one of statements 31 to 37, wherein the cerium oxide mainly (or completely) exists in a cubic morphology.

[0583] 40. The catalytic material according to any one of statements 31 to 39, wherein the cerium oxide is provided as nanoparticles.

[0584] 41. The catalytic material according to statement 40, wherein the nanoparticles have an average size of 10 - 30 nm.

[0585] 42. The catalytic material according to any one of statements 31 to 41, wherein the weight ratio of magnesium oxide to cerium oxide is 1:(0.1 - 10.0).

[0586] 43. The catalytic material according to any one of statements 31 to 41, wherein the weight ratio of magnesium oxide to cerium oxide is 1:(0.25 - 4.0).

[0587] 44. The catalytic material according to any one of statements 31 to 41, wherein the weight ratio of magnesium oxide to cerium oxide is 1:(0.50 - 2.0).

[0588] 45. The catalytic material according to any one of statements 31 to 41, wherein the weight ratio of magnesium oxide to cerium oxide is 1:(0.75 - 1.25).

[0589] 46. The catalytic material according to any one of statements 31 to 45, wherein the metal oxide is provided as a mixture of discrete magnesium oxide particles and discrete cerium oxide particles.

[0590] 47. The catalytic material according to any one of statements 31 to 45, wherein the metal oxide is provided as a plurality of particles, at least some of which comprise a mixture of magnesium oxide and cerium oxide.

[0591] 48. A method for preparing a catalytic material as defined in any of the foregoing statements, the method comprising the steps of:

[0592] a) providing a metal oxide as defined in any of the foregoing statements,

[0593] b) depositing a metal M on the metal oxide, where M is as defined in any of the foregoing statements, and

[0594] c) optionally reducing the product resulting from step b).

[0595] 49. The method according to statement 48, wherein in step b), the metal M is deposited on the metal oxide by chemical vapor deposition, wet impregnation or ball milling.

[0596] 50. The method according to statement 48 or 49, wherein the method further comprises depositing a promoter Q on the product resulting from step b), where Q is as defined in any of statements 19 to 25.

[0597] 51. The method according to any one of the foregoing statements 48, 49 or 50, wherein the method further comprises mixing the product resulting from step b) with an acidic zeolite, where the acidic zeolite is as defined in any of statements 27 to 29.

[0598] 52. The method according to any one of statements 48 to 51, wherein the metal oxide provided in step a) consists of magnesium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

[0599] 53. The method according to statement 52, wherein the magnesium oxide is as defined in any of statements 2 to 9.

[0600] 54. The method according to any one of statements 48 to 51, wherein the metal oxide provided in step a) comprises magnesium oxide and cerium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

[0601] 55. The method according to statement 54, wherein the metal oxide is as defined in any of statements 2 to 9 and 32 to 47.

[0602] 56. The method according to any one of statements 48 to 51, wherein the method further comprises the step of mixing the catalytic material with other catalytic materials, wherein the other catalytic materials comprise:

[0603] Metal oxides, wherein the metal oxides are:

[0604] Magnesium oxide as defined in any one of statements 1 to 9, or

[0605] Cerium oxide as defined in any one of statements 31 to 41, or

[0606] Magnesium oxide as defined in any one of statements 1 to 9 and cerium oxide as defined in any one of statements 31 to 41,

[0607] Metal M as defined in any one of statements 1 and 10 to 18.

[0608] 57. The method according to statement 56, wherein the metal oxide of the other catalytic material is different from the metal oxide of the catalytic material.

[0609] 58. The method according to statement 56 or 57, wherein the metal M of the other catalytic material is the same as the metal M of the catalytic material.

[0610] 59. The method according to statement 56, 57 or 58, wherein the other catalytic material further comprises: promoter Q as defined in any one of statements 19 to 25, optionally wherein the promoter Q of the other catalytic material is the same as the promoter Q of the catalytic material.

[0611] And / or

[0612] Acidic zeolite as defined in any one of statements 27 to 29, optionally wherein the acidic zeolite of the other catalytic material is the same as the acidic zeolite of the catalytic material.

[0613] 60. The method according to any one of statements 56 to 59, wherein the other catalytic material comprises:

[0614] a) 40.0 - 99.9% w / w of cerium oxide, wherein the (100) crystal plane forms at least 20% of the exposed surface of the cerium oxide,

[0615] b) 0.01 - 20.0% w / w of metal M, which is selected from the group consisting of Ru, Fe, Co, Mo and mixtures of two or more thereof,

[0616] 61. The method according to any one of statements 56 to 59, wherein the other catalytic material comprises:

[0617] a) 80.0 - 98.5% w / w of cerium oxide, wherein the (100) crystal plane forms at least 40% of the exposed surface of the cerium oxide, and

[0618] b) 1.5 - 7.0% w / w of metal M, wherein M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo.

[0619] 62. The method according to any one of statements 56 to 59, wherein the other catalytic material comprises:

[0620] a) 88.0 - 97.2% w / w of cerium oxide, wherein the (100) crystal plane forms at least 60% of the exposed surface of the cerium oxide.

[0621] b) 2.8 - 4.5% w / w of metal M, wherein M is Ru.

[0622] 63. The method according to any one of statements 56 to 62, wherein the metal oxide provided in step a) of the method consists of magnesium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

[0623] 64. A catalytic material obtained, directly obtained, or obtainable by the method according to any one of statements 48 to 63.

[0624] 65. A method for catalytic decomposition of ammonia, the method comprising the step of contacting ammonia with a catalytic material comprising:

[0625] a) A metal oxide, which comprises:

[0626] i) Magnesium oxide comprising an exposed (111) crystal plane, or

[0627] ii) Cerium oxide, or

[0628] iii) Magnesium oxide comprising an exposed (111) crystal plane and cerium oxide;

[0629] b) Metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof.

[0630] 66. The method according to statement 65, wherein the metal oxide comprises, consists essentially of, or consists of magnesium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

[0631] 67. The method according to statement 65, wherein the metal oxide comprises, consists essentially of, or consists of magnesium oxide and cerium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

[0632] 68. The method according to statement 65, wherein the metal oxide comprises, consists essentially of, or consists of cerium oxide.

[0633] 69. The method according to claim 65, 66 or 67, wherein the (111) crystal plane forms at least 10% of the exposed surface of magnesium oxide.

[0634] 70. The method according to claim 65, 66 or 67, wherein the (111) crystal plane forms at least 20% of the exposed surface of magnesium oxide.

[0635] 71. The method according to claim 65, 66 or 67, wherein the (111) crystal plane forms at least 30% of the exposed surface of magnesium oxide.

[0636] 72. The method according to claim 65, 66 or 67, wherein the (111) crystal plane forms at least 40% of the exposed surface of magnesium oxide.

[0637] 73. The method according to claim 65, 66 or 67, wherein the (111) crystal plane forms 40 - 50% of the exposed surface of magnesium oxide.

[0638] 74. The method according to claim 65, 66 or 67, wherein the (111) crystal plane forms more than 90% of the exposed surface of magnesium oxide.

[0639] 75. The method according to any one of statements 65 to 57 or 69 to 74, wherein the magnesium oxide is provided as nanoparticles.

[0640] 76. The method according to statement 75, wherein the nanoparticles have an average size of 100 - 250 nm.

[0641] 77. The method according to any one of statements 65 or 67 to 76, wherein the cerium oxide comprises an exposed (100) crystal plane.

[0642] 78. The method according to any one of statements 65 or 67 to 76, wherein the (100) crystal plane forms at least 20% of the exposed surface of cerium oxide.

[0643] 79. The method according to any one of statements 65 or 67 to 76, wherein the (100) crystal plane forms at least 40% of the exposed surface of cerium oxide.

[0644] 80. The method according to any one of statements 65 or 67 to 76, wherein the (100) crystal plane forms at least 60% of the exposed surface of cerium oxide.

[0645] 81. The method according to any one of statements 65 or 67 to 76, wherein the (100) crystal plane forms at least 80% of the exposed surface of cerium oxide.

[0646] 82. The method according to any one of statements 65 or 67 to 76, wherein the (100) crystal plane forms at least 85% of the cerium oxide exposed surface.

[0647] 83. The method according to any one of statements 65 or 67 to 76, wherein the cerium oxide is present as a mixture of cubic and rod-like morphologies.

[0648] 84. The method according to any one of statements 65 or 67 to 76, wherein the cerium oxide is present mainly (or entirely) as a cubic morphology.

[0649] 85. The method according to any one of statements 65 or 67 to 84, wherein the cerium oxide is provided as nanoparticles.

[0650] 86. The method according to statement 85, wherein the nanoparticles have an average size of 10 - 30 nm.

[0651] 87. The method according to any one of statements 65 to 86, wherein the metal M is selected from the group consisting of Ru, Fe, and mixtures thereof.

[0652] 88. The method according to any one of statements 65 to 86, wherein the metal M is Ru.

[0653] 89. The method according to any one of statements 65 to 88, wherein the catalytic material comprises:

[0654] 0.01 - 30.0% w / w of the metal M, and

[0655] 40.0 - 99.9% w / w of the metal oxide.

[0656] 90. The method according to any one of statements 65 to 88, wherein the catalytic material comprises:

[0657] 0.01 - 15.0% w / w of the metal M, and

[0658] 55.0 - 99.9% w / w of the metal oxide.

[0659] 91. The method according to any one of statements 65 to 88, wherein the catalytic material comprises:

[0660] 1.5 - 7.0% w / w of the metal M, and

[0661] 80.0 - 98.5% w / w of the metal oxide.

[0662] 92. The method according to any one of statements 65 to 88, wherein the catalytic material comprises:

[0663] 2.5 - 6.0% w / w of said metal M, and

[0664] 85.0 - 97.5% w / w of said metal oxide.

[0665] 93. The method according to any one of statements 65 to 88, wherein said metal M is distributed on the surface of said metal oxide.

[0666] 94. The method according to any one of statements 65 to 93, further comprising an alkali metal Q.

[0667] 95. The method according to statement 94, wherein said alkali metal Q is selected from the group consisting of Cs, K, Ba, and mixtures of two or more thereof.

[0668] 96. The method according to statement 94, wherein said alkali metal Q is selected from the group consisting of Cs, K, and mixtures thereof.

[0669] 97. The method according to statement 94, wherein said alkali metal Q is Cs.

[0670] 98. The method according to any one of statements 94 to 97, wherein the molar ratio of M:Q is 1:(0.1 - 3).

[0671] 99. The method according to any one of statements 94 to 97, wherein the molar ratio of M:Q is 1:(0.5 - 1.5).

[0672] 100. The method according to any one of statements 94 to 97, wherein the molar ratio of M:Q is 1:(0.75 - 1.25).

[0673] 101. The method according to any one of statements 65 to 100, further comprising an acidic zeolite.

[0674] 102. The method according to statement 101, wherein said acidic zeolite is ZSM - 5.

[0675] 103. The method according to statement 101 or 102, wherein said catalytic material comprises 0.01 - 50% w / w of acidic zeolite.

[0676] 104. The method according to statement 101 or 102, wherein said catalytic material comprises 0.01 - 20% w / w of acidic zeolite.

[0677] 105. The method according to any one of statements 65 to 104, wherein the method is carried out under batch conditions.

[0678] 106. The method according to any one of statements 65 to 104, wherein the method is carried out under continuous flow conditions.

[0679] 107. The method according to any one of statements 65 to 106, wherein the ammonia is gaseous ammonia.

[0680] 108. The method according to any one of statements 65 to 106, wherein the ammonia is liquid ammonia.

[0681] 109. The method according to any one of statements 65 to 108, wherein the ammonia is contacted with the catalytic material in the presence of molecular oxygen.

[0682] 110. The method according to statement 109, wherein the molar ratio of NH3:O2 is from 1:0.01 to 1:0.75.

[0683] 111. The method according to statement 109, wherein the molar ratio of NH3:O2 is from 1:0.05 to 1:0.43.

[0684] 112. The method according to any one of statements 65 to 111, wherein the ammonia is contacted with the catalytic material at a temperature of 150 - 900 °C.

[0685] 113. The method according to any one of statements 65 to 111, wherein the ammonia is contacted with the catalytic material at a temperature of 250 - 500 °C.

[0686] 114. The method according to any one of statements 65 to 113, wherein the ammonia is provided at a pressure of 0.001 - 100 bar.

[0687] 115. The method according to any one of statements 65 to 114, wherein the ammonia is contacted with the catalytic material in the presence of steam.

[0688] 116. The method according to any one of statements 65 to 115, wherein the catalytic material is as defined in any one of statements 1 to 47 and 64.

[0689] Examples

[0690] One or more embodiments of the present invention will now be described with reference to the accompanying drawings, for illustrative purposes only, wherein:

[0691] Figure 1 Transmission electron microscopy examinations of (a) MgO(111), (b) MgO(110), and (c) MgO(100) supports are shown. The lattice spacing was calculated by measuring 10 fringes.

[0692] Figure 2The X-ray diffraction patterns of MgO(111), MgO(110), and MgO(100) supports are shown.

[0693] Figure 3 The HAADF-STEM of (a,b) 3 wt%-Ru / MgO(111) is shown. The inset of (b) is the local fast Fourier transform pattern of (b).

[0694] Figure 4 The (a) 1 H NMR, (b) trimethylphosphine oxide (TMPO)-assisted 31 P MAS NMR measurements of MgO(111), MgO(110), and MgO(100) are shown.

[0695] Figure 5 The in-situ Fourier transform infrared measurements (the normalized difference spectra between the in-situ spectra and the background spectra) of (a) Ru / MgO(111) and (b) Ru / Mg(110) samples after exposure to H2 for 15 minutes are shown. The spectra were obtained by collecting 32 scans with a resolution of 4 cm -1 , expressed in absorbance units. The sample powder was pressed into pellets and then loaded onto the sample holder. Then the sample was flushed with He at 200 °C for 30 minutes to clean the surface. After collecting the background spectra, N2 gas was passed through the sample holder at a rate of 20 mL min -1 for 15 minutes, and the in-situ sample spectra were recorded. After 15 minutes, then H2 gas was passed through at 20 mL min -1 , and the in-situ spectra were recorded. The spectra shown are the difference spectra between the in-situ spectra and the background spectra.

[0696] Figure 6 The Operando ambient pressure XPS is shown. (a,c) The O1s spectra of Ru / MgO(111) and Ru / MgO(110) respectively under continuous switching between Ar and H2 gases at 350 °C. The spectra were measured at a photon energy of 980 eV. (b,d) Depth profiling of the O1s spectra using variable photon energies under H2 at 350 °C. "5 atomic layers" corresponds to the penetration depth, with a photon energy (PE) of 980 eV; the depth of "6 atomic layers" is at PE of 1280 eV; the depth of "8 atomic layers" is at PE of 1880 eV.

[0697] Figure 7 The current-voltage tests of (a) the Ru / MgO catalyst at 25 °C and (b) the Ag-Ru / MgO catalyst at 150 °C are shown.

[0698] Figure 8 Shows the size distribution of cerium oxide nanoparticles in different morphologies (a) cube (b) rod length and their corresponding TEM images of CeO2.

[0699] Figure 9 Shows (a) the exit wave recovered from the HR-TEM image, the HR-TEM image shows cerium oxide cubes mainly with polar (100) surfaces, overlapping with the expected model crystal structure; the FFT of the (100) HR-TEM image. (b) The HRTEM image shows cerium oxide rods mainly with non-polar (110) surfaces, overlapping with the expected model crystal structure; the FFT of the (110) HRTEM image.

[0700] Figure 10 Shows the thermodynamic equilibrium of ammonia decomposition at atmospheric pressure as a function of temperature.

[0701] Figure 11 Shows the catalytic performance of ammonia decomposition on Ru-based catalysts with different MgO supports. Reaction conditions: T = 400 °C, WHSV = 15000 mL g cat -1 h -1 , 1 atm.

[0702] Figure 12 Shows the NH3 conversion on the Ru / MgO(111) catalyst as a function of WHSV at 350 °C, 375 °C, 400 °C and 425 °C.

[0703] Figure 13 Shows the NH3 conversion on the Ru / MgO(111) and CsRu / MgO(111) catalysts as a function of reaction temperature at a WHSV of 30000 mL g cat -1 h -1 .

[0704] Figure 14 Shows the Arrhenius plots of the reaction rate (ln(r)) of NH3 decomposition on the Ru / MgO(111) and Cs-Ru / MgO(111) catalysts versus 1 / T.

[0705] Figure 15 Shows the NH3 conversion and H2 yield of CsRu / MgO(111) with different O2 contents. Reaction conditions: WHSV = 4000 mL g cat -1 h -1 , 1 bar.

[0706] Figure 16Shows the comparison of (a) H2 formation rate and (b) H2 yield on Ru / MgO(111), Ru / CeO2(100), and Ru / CeO2(100)-MgO(11) at 250 °C and 300 °C and a WHSV of 30000 mL g cat -1 h -1 −1.

[0707] 1. Preparation of catalyst

[0708] 1.1. Preparation of MgO facet

[0709] MgO nanosheets with exposed (111) crystal planes (denoted as MgO(111)) were synthesized by a hydrothermal method using benzoic acid as a surfactant. Briefly, at room temperature, 2.0 g of MgCl2 and 0.12 g of benzoic acid were dissolved in 60 mL of deionized water by sonication. The resulting mixture was stirred for 10 minutes. Then, 20 mL of 2 M NaOH solution was added dropwise to the mixture to form a white precipitate. Subsequently, the slurry was transferred to a 100 mL autoclave and gradually heated to 180 °C and maintained for 24 hours. After filtration, washing with water, and vacuum drying at 80 °C overnight, a Mg(OH)2 phase precursor was obtained. After calcination in compressed air at 500 °C for 6 hours, MgO(111) nanosheets were obtained.

[0710] Commercial magnesium oxide (denoted as Com-MgO) was purchased from Sigma Aldrich.

[0711] MgO(110) with preferentially exposed (110) crystal planes was prepared by reconstruction starting from commercial MgO. Typically, 500 mg of commercial MgO was boiled in water for 5 hours and then dried overnight at 120 °C. Then, the resulting powder was calcined in vacuo at 500 °C for 6 hours.

[0712] MgO(100) with preferentially exposed (100) crystal planes was obtained by direct thermal decomposition of Mg(NO3)2 precursor at 500 °C for 5 hours.

[0713] Octahedral MgO(111) is prepared by a surface reconstruction method that involves splitting MgO nanocubes in a pH-controlled solution. Typically, MgO nanocubes (used as the basic precursor with the main (100) crystal plane) are prepared by burning magnesium ribbon in a controlled gas flow under ambient conditions. Smoky crystals are collected with a glass plate in an Ar environment to prevent surface etching in moisture, and then the smoky crystals are dissolved in an aqueous solution with carefully controlled pH. To produce the (111) crystal plane, the MgO nanocubes are allowed to age in a pH 1 solution at ambient temperature for 7 days, in which the surface slowly splits until it exposes an octahedral structure (all 8 exposed crystal planes are (111)). The obtained crystals are then calcined under vacuum to remove surface hydroxyl groups, thus forming a clean octahedral MgO(111) structure.

[0714] High surface area MgO(111) (HS-MgO(111)) is prepared by using a magnesium hydroxycarbonate precursor. First, magnesium nitrate is dissolved in water at 60 °C (11 w / w% solution). Meanwhile, in a separate flask, sodium carbonate is dissolved in water at 60 °C (11 w / w% solution), and then sodium hydroxide (40 w / w% NaOH in the solution) is added. The mixture is then heated to the boiling temperature and then cooled to ambient temperature. Filtration is carried out, and the supernatant is heated to 60 °C. The resulting solution is slowly added to the above-prepared magnesium nitrate solution to form a magnesium carbonate precipitate. The precipitate is then collected by filtration, washed in cold water, and centrifuged three times. The obtained solid is dried in an 80 °C oven. HS-MgO(111) is obtained by calcining at 500 °C for three hours.

[0715] 1.2. Preparation of Ru-loaded MgO

[0716] Supported Ru / MgO materials are prepared by chemical vapor deposition by impregnation under an inert atmosphere. Briefly, a quantitative amount of Ru3(CO) 12 is dispersed in a tetrahydrofuran (THF) solution, and then the required amount of MgO support is added. The obtained mixture is sonicated for 6 hours, and then the solvent is removed. The resulting orange powder is treated under vacuum at 70 °C for 12 hours to finally obtain a light gray powder. Then, under an Ar gas flow, these chemical precursors are heated at 2 °C / min to evaporate and deposit on MgO before reaching 350 °C and maintained at 350 °C for 5 hours. Thus, supported Ru / MgO(110), Ru / MgO(100), and Ru / Com-MgO are successfully synthesized. For Ru / MgO(111), Mg(OH)2 with an exposed polar surface is used as the precursor. The loading of Ru is similar to the above.

[0717] 1.3. Preparation of Ru-loaded CeO2-MgO(111)

[0718] The cubic polar CeO2(100) and the rod-shaped CeO2 with a predominantly non-polar (110) surface were preferentially synthesized by hydrothermal synthesis of cerium nitrate in sodium hydroxide at 180 °C and 100 °C, respectively. As previously mentioned in the case of MgO(111), Ru deposition on these oxides was prepared by chemical vapor deposition by impregnation under an inert atmosphere.

[0719] Pre-mix the physical powder mixture of Ru / CeO2(100) + Ru / MgO(111) and grind it in the same pot accordingly.

[0720] The co-synthesized CeO2(100)-MgO(111) and CeO2(110)-MgO(111) supports were prepared by hydrothermal synthesis of cerium oxide at 180 °C and 100 °C, respectively, but with an appropriate amount of magnesium oxide precursor added, see above (resulting in a CeO2:MgO weight ratio of 1:1). Briefly, the oxide precursors were added to 10 mL of 0.45 M aqueous cerium nitrate solution and dispersed by ultrasound, and then the mixed solution was added dropwise to 80 mL of NaOH solution at a specific concentration (for rods and cubes, NaOH = 6 M). After stirring for 30 minutes, the mixture was added to a 200 mL Teflon-lined stainless steel autoclave. Then the sealed autoclave was transferred to a temperature-controlled oven (for CeO2(110), T = 373 K, for CeO2(100), T = 453 K) and kept in the oven for 24 hours. After cooling, the precipitate was filtered, washed with deionized water, and dried in vacuo at 353 K for 12 hours. After that, Ru3(CO) 12 was dispersed in a tetrahydrofuran (THF) solution, and then the required amounts of CeO2(100)-MgO(111) and CeO2(110)-MgO(111) precursors were added. The resulting mixture was sonicated for 6 hours and then the solvent was removed. The resulting orange powder was treated in vacuo at 85 °C for 24 hours until a light gray powder was obtained. Finally, the powder was heated in a 5% H2 / N2 gas stream at 350 °C (ramping at 2 °C / min) for 4 hours.

[0721] 1.4. Preparation of CoMo bimetallic nanoparticles

[0722] Cobalt molybdate salts and ammonium heptamolybdate salts were synthesized by a one-pot method and then calcined under ammonia to prepare CoMo nanoparticles. Briefly, a quantitative amount of cobalt nitrate hexahydrate and ammonium heptamolybdate (Co:Mo molar ratio = 1:1) were dissolved in water and stirred for 3 hours. Then the mixture was dried overnight at 100 °C and then calcined at 400 °C for 2 hours under dry air. Then, the obtained product was heated at 700 °C (heating rate of 1 °C / min) under pure ammonia for 3 hours. After cooling to room temperature, the product was passivated in nitrogen containing 0.1% oxygen to avoid over-oxidation.

[0723] 1.5. Preparation of CoMo-loaded CeO2(100)-MgO(111)

[0724] The CoMo nanoparticles obtained from 1.4 were loaded into CeO2(100)-MgO(111) with a theoretical loading of 25 wt% by ball milling for 30 minutes (the synthesis steps followed 1.3).

[0725] 1.6. Preparation of Cs-promoted Ru-loaded sample

[0726] The Cs-promoted Ru-based catalyst was prepared by wet impregnation of the Ru catalyst with a CsNO3 solution. Then it was dried overnight at 70 °C.

[0727] 1.7. Incorporation of ZSM-5 into Ru-loaded sample

[0728] First, ZSM-5 was pretreated in air at 350 °C for 4 hours and then evacuated overnight at 80 °C. Then the product was physically mixed with the Ru-loaded metal oxide in the above ratio.

[0729] 2. Catalytic decomposition of ammonia

[0730] 2.1. Continuous flow fixed bed reactor

[0731] Ammonia decomposition was carried out in a continuous-flow fixed-bed reactor equipped with a computer-controlled automatic sampling system. Typically, 50 mg of the catalyst was loaded into the center of a quartz tube packed with quartz wool. Before the reaction, the catalyst was pretreated at 350 °C under a 5% H2 / He gas flow for 4 hours. The gas was switched to an NH3 flow, and then the catalyst bed was adjusted to the target reaction temperature. For O2-promoted ammonia decomposition, a calibrated amount of O2 gas flow was introduced during the reaction. All activity tests were carried out at atmospheric pressure in the temperature range of 250 °C - 500 °C with different weight hourly space velocities (WHSV). After stabilization, the gas composition was analyzed by an on-line gas chromatograph (Agilent 7890A) equipped with a TCD detector and a HayeSep Q column. A blank test was carried out in the reactor using quartz powder instead of the Ru-MgO catalyst. No ammonia conversion was observed in the experimental temperature range.

[0732] To evaluate the catalytic effect under water flow, a fixed-bed reactor was connected to a liquid pump, and the performance was measured by titration. First, an acid solution (0.5 M) was prepared before the reaction, and a blank test without a catalyst was carried out to review the ammonia gas flow. The pretreatment of the catalyst followed the above steps. After the reaction was stabilized, the performance of the catalyst without adding water was measured. Then, water was introduced into the system for measuring activity at a predetermined flow rate.

[0733] 2.2 Liquid phase batch reactor

[0734] The ammonia decomposition in ammonia water was carried out in a batch reactor at high temperature. Typically, 20 mg of the catalyst was freshly reduced and placed in the batch reactor. Subsequently, 20 mL of ammonia water containing 33% ammonia was added to the reactor. Then, helium was flushed into the reactor 3 times to expel the internal air, and then 10 bar of helium was injected (for later GC measurement). Then, the temperature was increased to different temperatures at 5 °C / min. After the reaction, the amounts of hydrogen and ammonia were analyzed by an on-line gas chromatograph (Agilent 7890A) equipped with a TCD detector and a HayeSep Q column. Then, the hydrogen formation rate was calculated by back-titrating the ammonia water solution.

[0735] 3. Results and discussion

[0736] All MgO supports with preferentially exposed surface crystal planes were successfully synthesized and characterized by transmission electron microscopy ( Figure 1 ), where the lattice spacing was in good agreement with the literature value 21-22 . X-ray diffraction also confirmed the periclase nature of MgO ( Figure 2 ). After impregnation, although the Ru weight % loading was high, it was found that most Ru species were still dispersed in atomic form on the MgO(111) support. As Figure 3 shown, it was found that Ru species were only anchored on the highly ordered MgO(111) crystal plane, which might be due to the high stabilization energy provided by the polar support.

[0737] To study the surface properties of MgO(111), nuclear magnetic resonance (NMR) was carried out. The H 1 affinity of surface oxygen anion sites on different prepared pure MgO supports was evaluated by + H MAS NMR. As Figure 4 a shown, all with residual H +All MgO supports show two chemical shifts, one resonance near 0.7 ppm and another resonance at 5.43 ppm for MgO(111), 4.78 ppm for MgO(110), and 4.74 ppm for MgO(100). The first peak near 0.7 ppm is the resonance of protons from isolated hydroxyls (i.e., Mg-OH) and physically adsorbed water 23 , while the second peak at lower field can be attributed to bridged hydroxyl protons (i.e., Mg-O(H)-Mg). The significant shift from around 4.7 ppm for both nonpolar (100) and polar (110) surfaces to 5.4 ppm for the polar (111) surface is attributed to the preferential adsorption of protons induced by the local electric field from surface polarity, as observed in the case of ZnO 23 .

[0738] Probe-assisted 31 P MAS NMR further confirmed this polarity-induced preferential proton adsorption 23 . The adsorption of the Lewis base molecule trimethylphosphine oxide (TMPO) is expected to interact with surface cations (i.e., Mg 2+ or H + ) and reflect its corresponding chemical state through the shift in 31 P NMR. As shown in Figure 4 b, the adsorption of TMPO on bridged hydroxyl protons indeed highly depends on the surface polarity of the exposed MgO crystal plane, and an obvious shift from 43 ppm for MgO(100) and MgO(110) to 45.8 ppm for MgO can be observed (physical adsorption of TMPO is at ~41 ppm). However, no interaction between TMPO and surface Mg 2+ of these three MgO supports was observed, probably because Mg 2+ is easily hydroxylated to Mg-OH, and the interaction between Mg-OH and TMPO is too weak to produce 31 P chemical shift 24 .

[0739] Then Fourier transform infrared spectroscopy (FTIR) was used to examine the surface properties of the MgO(111) support under a dynamic reducing atmosphere at 200 °C. To further determine the relationship between protons and bridged O 2- on the polar (111) surface, in situ Fourier transform infrared measurements were carried out on Ru supported on the MgO crystal plane. Figure 5 a shows the spectrum of hydrogen passing over the anhydrous Ru / MgO sample at 200 °C for 15 minutes. Here, the broad peak at 3300 cm -1 is assigned to the –OH stretching region, which comes from the bridged O 2-The significant difference in intensity between the polar (111) crystal plane and the other two crystal planes once again reveals the high affinity of the polar carrier phase for H and the bridging O 2- The mobility of Ru metal to move H from Ru metal to the support surface in H2. After Ru / MgO(111) was exposed to N2 or Ru-MgO(110) was exposed to H2, the OH intensity was much smaller but gradually increased, which was caused by the moisture from the gas flow.

[0740] Therefore, both NMR and FTIR revealed rapid hydrogen adsorption on the polar MgO(111) support. Operando XPS was then used to probe the coverage and extent of hydrogen spillover on polar MgO(111). Figure 6 As shown in the figure, the O1s spectrum of Ru / MgO(111) can be resolved into [OH] and [O 2- The sample was first heated to 350 °C under H2 to remove the surface RuO x Then switch to Ar for the first measurement. An obvious [OH] peak was observed under Ar, which may be caused by the residual H making the unstable O 2- Interestingly, it is noted that when the gas is switched to H2, the [OH] component increases significantly from 13.6% to 26.3%, which can be inferred to be the overflow of hydrogen from the Ru surface to the O 2- Surface. Surface H on polar MgO(111) + This increase in is also in good agreement with the chemisorption experiments. When the gas was subsequently switched back to Ar, the [OH] component decreased accordingly, indicating the reversibility of this phenomenon, i.e., the surface protons migrated back to Ru. In contrast, a broad peak was observed in Ru / MgO(111), with line broadening attributed to the charging effect. This also reveals the difference in the material conduction properties in which charge can be transferred away in polar MgO(111) but retained in non-polar MgO(110). There is no obvious difference between the spectra of Ru / MgO(110) when the gas is switched between H2 and Ar. In order to detect the surface H + The depth and distance that can be moved were analyzed by synchrotron XPS at different photon energies to perform depth profiling of the O1s spectrum ( Figure 6 b, 6d). It is noteworthy that the relative [OH] signal decreases with increasing information depth (i.e., more signal comes from deeper layers), which is consistent with the H + It is mainly located near the surface, indicating that the surface H + In contrast, the O1s spectra of Ru / MgO(110) do not change significantly at different depths, which is consistent with the fact that there is little or no surface H on this sample.+ Consistent

[0741] Considering the ability of H + to penetrate through the MgO(111) surface, the proton conductivity was then measured by current-voltage tests under a hydrogen atmosphere. As Figure 7 shown, Ru / MgO(110) and Ru / MgO(100) showed similar and comparable resistances, while Ru / MgO(111) showed much lower resistance throughout the range. Notably, the differences between the spectra were even more significant under negative bias. This can be inferred as a greater mobility of the positive charge carriers (protons in this case) on the MgO(111) surface. To incorporate grain boundaries and enhance the surface mobility of charges on the MgO support, silver powder was introduced into the sample pellets and pre-reduced under flowing hydrogen at 350 °C. Figure 7 b shows the high-temperature test (150 °C), and a similar trend was again observed. The extremely low resistance of Ru / MgO(111) caused by H + conductivity was observed, which was due to the enhanced proton mobility through the polar MgO(11) surface. In summary, the above characteristics indicate that the Ru nanointerface promotes the excellent proton transport ability of the MgO(111) surface, and thus the bond activation can be enhanced by the migration of adsorbed H species from the metal surface to the MgO(11) support.

[0742] Similarly, the polar CeO2 (cubic) and non-polar CeO2 (rod-shaped) were characterized by TEM and HR-TEM, as Figure 8 and Figure 9 shown.

[0743] Ammonia decomposition is considered an attractive method for producing CO-free x H2 because ammonia is thermodynamically unstable at high temperatures. The reaction is a mild endothermic process involving the successive breaking of N-H bonds and the recombination of N and H. Although as Figure 10 shown, ammonia can start to decompose at low temperatures, the equilibrium conversion of ammonia is 98 - 99% at 425 °C, and the actual conversion highly depends on the catalyst and temperature. Efficient production of hydrogen at high weight hourly space velocities at low temperatures remains challenging. This is due to the rate-determining step limitation of the N recombination in ammonia decomposition, especially at low temperatures (300 °C - 500 °C). The high strength of the metal-N bond is typically between 500 kJ mol -1 to 630 kJ mol -1The range results in great difficulties in the activation of the formed metal-N bond. The key solution is to promote the transfer of electrons from the support or additive to the antibonding orbital of the transient metal-N during the reaction. Based on the synthesis and characterization of the catalyst, it is believed that Ru / MgO(111) exhibits high proton conduction ability, which is beneficial to the removal of protons during the N-H bond cleavage process. In this regard, electrons can be enriched and transferred at the metal sites to weaken the metal-N bond and promote ammonia decomposition at low temperatures.

[0744] After examining the thermodynamic feasibility, ammonia decomposition was carried out over our Ru-based catalyst in a continuous fixed-bed reactor. As Figure 11 shown, at 400 °C and a weight hourly space velocity (WHSV) of 15000 mL g cat -1 h -1 −1 h−1, Ru-based catalysts with different MgO supports showed a preference for ammonia decomposition. Among these samples, Ru / MgO(111) had the highest activity, which was 82.4%. In contrast, Ru / MgO(110) only showed an NH3 conversion of 43.2% under the same conditions, even though the samples had similar surface areas. This may be due to the different surface properties of MgO(111) and (110) as described above. The MgO(111) crystal plane is covered with O-terminals, which can provide a large number of basic surface sites, which is beneficial to electron supply and proton conduction. On the contrary, the alternating Mg 2+ and O 2- on the (110) surface led to a relatively low conversion rate. Ru / MgO(100) showed the lowest activity, with an NH3 conversion of 19.8%. In contrast, Ru / Com-MgO with polycrystalline commercial MgO without any preferentially exposed crystal planes showed an ammonia conversion of 24.3%, slightly higher than that of Ru / MgO(100). Therefore, MgO supports with different exposed crystal planes provide different surface configurations, which play an important role in the efficient conversion of NH3.

[0745] The effect of WHSV was studied over Ru / MgO(111) at different reaction temperatures. Figure 12 The NH3 conversion as a function of WHSV is described. It can be seen that as the WHSV increases, the ammonia conversion decreases, which may be due to the reduced residence time of NH3 at the active sites. This indicates that a relatively low WHSV is beneficial to NH3 conversion. It is worth noting that as the WHSV increases, the NH3 conversion at 425 °C decreases more slowly than that at lower reaction temperatures. Therefore, a conversion rate higher than 92% can also be obtained at 425 °C and a WHSV of 30000 mL g cat -1 h -1 −1 h−1 ( Figure 12) Comparisons were also made for different Ru loadings, as listed in Table 1. Due to the chemical deposition used for Ru loading, the actual loading is expected to be lower than the formulated loading. It is understood that the activity increases with the increase of Ru loading, and complete conversion is achieved at 425 °C and WHSV of 30,000 mL g cat -1 h -1 −1. Therefore, unless otherwise stated, a 5% experimental loading was used for the synthesis of the catalyst.

[0746] Table 1 Catalytic performance of Ru / MgO(111) with different Ru loadings

[0747]

[0748] a Determined by ICP - OES analysis. Reaction conditions: T = 450 °C, WHSV = 30,000 mL g cat -1 h -1 −1, 1 atm.

[0749] Therefore, it should be noted that the activities of different catalysts should be compared at the same temperature and WHSV (contact time). The higher the temperature and the lower the WHSV, the higher the ammonia conversion rate.

[0750] Due to the electron - donating effect, alkali metal ions have been proven to be effective promoters for supported Ru - based catalysts. In this work, cesium was used as a promoter to modify the Ru / MgO(111) catalyst (Ru / Cs molar ratio is 1 / 1). As Figure 13 shown, it can be seen that the catalytic performance shows an S - shaped curve, and the conversion rate increases with the increase of temperature, which is consistent with the slightly endothermic reaction of NH3 decomposition. The ammonia conversion activity shows a significant enhancement in the range of 325 °C to 400 °C. For Ru / MgO(111), NH3 conversion reaches thermodynamic equilibrium at 450 °C and 30,000 mL g cat -1 h -1 −1 with a high WHSV, which is better than the previous reports on unpromoted Ru - based catalysts. The performance of CsRu / MgO(111) shows a similar trend to that of Ru / MgO(111); however, the incorporation of Cs significantly improves the NH3 conversion rate of the Ru / MgO(111) catalyst. It reaches complete conversion at 425 °C and WHSV of 30,000 mL g cat -1 h -1Almost complete conversion is achieved when the reaction temperature is 0.5 °C, which is higher than the conversion rate of the Ru / MgO(111) sample (92%). Under the same reaction conditions of 350°C to 400°C, an increase of more than 30% in NH3 conversion can be achieved. It is worth noting that this increase is more obvious at lower reaction temperatures.

[0751] Since the apparent activation energy (Ea) is a key parameter directly related to the catalytic performance, the Arrhenius plot was used to derive the Ea ( Figure 14 ). a Those Ru / MgO materials with 100-120 kJ / mol 10 In comparison, Ru / MgO(111) shows a much lower E a , which is 77.5 kJ / mol, showing excellent performance. Modification of Ru / MgO(111) with Cs not only improves the activity, but also leads to a decrease in apparent energy, obtaining 47.5 kJ / mol. The increased activity of the Cs-modified Ru / MgO(111) catalyst may be attributed to the change in the electronic properties of metallic Ru. Table 2 lists the comparison of Ru catalysts in the literature. The NH3 conversion of Ru / MgO(111) is 99.9% at 450 °C, which is better than most catalysts reported in the literature. The H2 formation rate was calculated based on the catalyst weight without considering the Ru content, which showed the highest H2 formation rate of 33.5 mmol g -1 min -1 . By further optimizing the exposure of the polar (111) crystal facets, Ru / octahedral-MgO(111) showed complete conversion at a lower temperature of 400 °C (entry 11 in Table 3). A MgO(111) support with higher specific surface area was also prepared by calcining a basic magnesium carbonate precursor (entry 12 in Table 3). In general, Ru / MgO(111) and Cs-promoted Ru / MgO(111) are alternative materials for efficient ammonia decomposition. Although Ru / MgO(111)-based catalysts have excellent catalytic performance in ammonia decomposition, achieving high H2 yield at low reaction temperature remains a huge challenge, which limits commercial applications, especially when used in conjunction with proton exchange membrane fuel cells for mobile applications.

[0752] Table 2 At 450 °C and atmospheric pressure (WHSV: 30000 mL g cat -1 h -1 ) NH3 conversion over Ru catalyst.

[0753]

[0754]

[0755] a CVD: Chemical Vapor Deposition; Conditions: WHSV = 15000 mL g -1 h -1 , T = 400 °C; b Conditions: WHSV = 15000 mL g -1 h -1 , T = 450 °C; c BHA: Barium hexaaluminate, Conditions: WHSV = 60000 mL g -1 h -1 ; d DP: Deposition - precipitation method, Conditions: WHSV = 36000 ml g -1 h -1 , K / Ru = 1 / 2; e Conditions: WHSV = 15000 mL g -1 h -1 , T = 450 °C.

[0756] In this paper, it is surprisingly found that ceria is also a good candidate as a Ru support in ammonia decomposition, and it may undergo a redox pathway to cleave the N - H bond. Interestingly, different morphologies of Ru - loaded ceria achieved almost 100% conversion at 450 °C under this WHSV, indicating that under comparable test conditions, its activity is even higher than that of MgO(111). However, a proper comparison can be made at a lower temperature of 400 °C before complete ammonia conversion. As can be seen from Table 3, Ru / CeO2(100) cubes seem to have higher activity compared to the corresponding CeO2(110) in rod - like form and polycrystalline CeO2 nanoparticles without specific crystal plane exposure. Thus, it is evident that the use of polar crystal planes can significantly enhance ammonia decomposition when MgO(111) and CeO2(100) are used as Ru supports.

[0757] Excitingly, the incorporation of CeO2(100) into MgO(111) produced a beneficial synergistic effect to some extent, which further increased the ammonia decomposition rate. In Table 3, Ru / CeO2(100) - MgO(111) co - synthesized by the hydrothermal method showed significantly higher activity than the physical mixture of Ru / CeO2(100)+Ru / MgO(111). It should be noted that the conversion rate of Ru / CeO2(100) - MgO(111) (Entry 7) was 80.5%, and the H2 formation rate was 27.0 mmol g cat -1 min -1. In contrast, the physical mixture (the mass ratio of the two catalysts was the same as that of the co-synthesized catalyst) showed lower activity. To further enhance the hydrogen formation rate, the acidic zeolite ZSM-5 was added to the optimized Ru / CeO2(100)-MgO(111), whose Bronsted acid sites have been shown to be able to capture ammonia at high temperatures. Therefore, a local ammonia concentration effect around the catalyst is to be expected. This allowed a H2 formation rate of 30.4 mmol g at 400 °C. cat -1 min -1 .

[0758] Table 3 NH3 conversion over different Ru-based catalysts at 400℃ and atmospheric pressure

[0759]

[0760]

[0761] In addition, it is critical to develop a new method for low-temperature NH3 decomposition while maintaining a considerable H2 space-time yield / purity. As described, the endothermicity of the decomposition reaction limits the thermodynamics and kinetics of ammonia conversion to hydrogen and nitrogen. For this need, a small amount of O2 is introduced into the reaction of ammonia to incompletely burn a portion of the formed H2 into H2O, thereby changing the total enthalpy of the decomposition reaction. Therefore, the decomposition reaction that produces H2, N2 and H2O can drive the original endothermic reaction to be converted into a thermoneutral or slightly exothermic reaction (oxidative decomposition), depending on the stoichiometry and properties of the catalyst in the steady state. However, the introduction of oxygen consumes H2 at the same time, resulting in a decrease in the theoretical H2 yield. Therefore, it is important to balance the ammonia conversion rate and the O2 content to maintain a high yield of H2 production. Figure 15 The NH3 conversion and H2 yield of CsRu / MgO(111) at different O2 contents are shown. The theoretical H2 yield (complete NH3 decomposition at 300°C) decreases with increasing O2 content (assuming that O2 reacts selectively with H2 to form H2O), which is still higher than the experimentally measured H2 yield, indicating incomplete NH3 conversion. In addition, the measured H2 yield and ammonia conversion are indeed higher at higher temperatures, close to thermodynamic values. It is interesting to see that the ammonia conversion increases with increasing O2 content in a kinetically controlled manner. Therefore, the presence of O2 on the surface can obviously help some basic pathways of the ammonia decomposition reaction. However, the formation of nitrogen oxides was not detected. It is also noted that with increasing O2 content, the H2 yield shows a volcano-type curve at 250°C (less obvious at 300°C), reaching an optimum just before the oxygen excess. This suggests that excess O2 on the surface (incomplete O2 conversion) seems to compete with ammonia decomposition for active sites. The H2 formation rate was calculated and is shown in Figure 16We introduce an O2 content of 8.26% to drive the total ΔH of the reaction to 0 kJ / mol (NH3 + 0.09O2 = 1.32H2 + 0.5N2 + 0.18H2O ΔH = 0 kJ / mol), where the theoretical optimum value of 88% H2 yield can be achieved without any energy input.

[0762] The CeO2(100) material as the Ru support seems to be superior to those of MgO(111), probably because the redox characteristics induce N-H heterolytic cleavage and the proton conductivity on its surface is significantly promoted. Excitingly, the hydrothermally co-synthesized Ru / CeO2(100)-MgO(111) mixture exhibits more superior performance at two different temperatures. For this purpose, the effectiveness of this composite catalyst for oxidative ammonia decomposition is evaluated by introducing a small amount of O2. Experimentally, from Figure 16 it can be observed that the H2 formation rates at 250 °C and 300 °C on Ru / MgO(111) and Ru / CeO2(100) are significantly increased respectively. Therefore, using a small amount of O2 during the reaction is clearly beneficial to H2 generation in ammonia oxidative decomposition.

[0763] The effectiveness of this catalyst for ammonia decomposition was also evaluated in the aqueous phase by the batch method (Table 4). Thus, 20 mg of Ru / MgO(111) was pre-reduced at 350 °C under 5% H2 for 6 h and freshly loaded into a stainless-steel batch reactor. Then 20.0 mL of H2O containing 33% NH3 was transferred into the reactor. 5 bar of He was injected and evacuated 3 times to purge the internal air / nitrogen. 10 bar of He was injected so that the outlet gas could be injected into the GC for post-reaction measurement. The reaction was allowed to proceed at 250 °C for 17.5 h. The outlet gas was injected into the GC to determine the H2 produced, and back-titration was performed to determine the amount of ammonia reacted.

[0764] Table 4 Decomposition of ammonia solution on Ru / MgO(111) maintained at 250 °C for 17.5 h in a batch reactor

[0765]

[0766] a Determined by ICP-OES analysis. Reaction conditions: T = 250 °C, 17.5 h

[0767] In addition, the performance of Ru / MgO(111) under the influence of water at high temperatures was also evaluated (Table 5). Excitingly, it was found that the water inhibition effect was low, despite the known adverse effect of water on typical catalysts. At a ratio of NH3:H2O = 2:1, the catalytic activity only decreased slightly, while at a high water ratio of NH3:H2O = 1:2, an activity higher than 60% was still maintained.

[0768] Table 5 Ammonia decomposition over Ru / MgO(111) with water at 400 °C and WHSV of 30000 mL g -1 h -1 −1 in a fixed bed reactor

[0769]

[0770] The catalytic performance of bimetallic CoMo nanoparticles supported on CeO2(100)-MgO(111) was also carried out to demonstrate the effect of non-noble metals compared to Ru (Table 6).

[0771] Table 6 Ammonia decomposition over CoMo / CeO2(100)-MgO(111) at different temperatures and WHSV

[0772]

[0773] The catalytic performance of the catalyst at high temperatures and high WHSV was also examined (Table 7). Surprisingly, it was found that even at 620 °C and WHSV of 300000 mL g -1 h -1 −1, complete conversion could still be achieved. A reference using a Johnson Matthey Fe catalyst has been included, which has a conversion rate of 51% under the same reaction conditions.

[0774] Table 7 Ammonia decomposition over Ru / CeO2(100)-MgO(111) and Johnson Matthey Fe catalyst at high temperature (620 °C) and high WHSV (300000 mL g -1 h -1 −1)

[0775]

[0776]

[0777] While specific embodiments of the invention have been described herein for purposes of reference and illustration, various modifications will be apparent to those skilled in the art without departing from the scope of the invention as defined by the appended claims.

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Claims

1. A catalytic material, comprising: a) a metal oxide, and b) a metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof, Among them, wherein the metal oxide comprises magnesium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

2. The catalytic material according to claim 1, wherein the (111) crystal plane forms at least 30% of the exposed surface of the magnesium oxide.

3. The catalytic material according to claim 1 or 2, wherein the metal M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo, preferably, wherein the metal M is only Ru.

4. The catalytic material according to claim 1, 2, or 3, wherein the catalytic material comprises: 0.01 - 30.0% w / w of the metal M, and 40.0 - 99.9% w / w of the metal oxide, preferably, wherein the catalytic material comprises: 2.5 - 6.0% w / w of the metal M, and 85.0 - 97.5% w / w of the metal oxide.

5. The catalytic material according to any one of the preceding claims, wherein the metal M has an average particle size of 0.5 - 100 nm.

6. The catalytic material according to any one of the preceding claims, which further comprises a promoter Q, wherein Q is selected from the group consisting of Cs, K, Ba, and mixtures of two or more thereof.

7. The catalytic material according to claim 6, wherein the molar ratio of M:Q is 1:(0.1 - 3).

8. The catalytic material according to any one of the preceding claims, wherein the metal oxide consists of magnesium oxide.

9. The catalytic material according to any one of claims 1 to 8, wherein the metal oxide comprises magnesium oxide and cerium oxide, and the magnesium oxide comprises an exposed (111) crystal plane.

10. The catalytic material according to claim 9, wherein the cerium oxide comprises an exposed (100) crystal plane.

11. The catalytic material according to claim 10, wherein the (100) crystal plane forms at least 40% of the exposed surface of the cerium oxide.

12. The catalytic material according to any one of claims 9, 10, and 11, wherein the metal oxide is provided as a mixture of discrete magnesium oxide particles and discrete cerium oxide particles (e.g., a physical mixture of magnesium oxide and cerium oxide), or the metal oxide is provided as a plurality of particles, at least some of which contain a mixture of magnesium oxide and cerium oxide (e.g., a chemical mixture of magnesium oxide and cerium oxide).

13. A method for preparing a catalytic material as claimed in any one of the preceding claims, the method comprising the steps of: a) providing a metal oxide as defined in any one of the preceding claims, b) depositing a metal M on the metal oxide, wherein M is as defined in any one of the preceding claims, and c) optionally reducing the product produced in step b).

14. A method for catalytic decomposition of ammonia, the method comprising the step of contacting ammonia with a catalytic material comprising: a) a metal oxide, comprising: i) magnesium oxide comprising an exposed (111) crystal plane, or ii) cerium oxide, or iii) Magnesium oxide and cerium oxide containing an exposed (111) crystal plane; b) A metal M selected from the group consisting of Ru, Fe, Co, Mo, and mixtures of two or more thereof.

15. The method according to claim 14, wherein the metal oxide comprises, consists essentially of, or consists of cerium oxide.

16. The method according to claim 14 or 15, wherein the (111) crystal plane forms at least 30% of the exposed surface of the magnesium oxide.

17. The method according to any one of claims 14, 15, and 16, wherein the cerium oxide contains an exposed (100) crystal plane.

18. The method according to any one of claims 14 to 17, wherein the (100) crystal plane forms at least 40% of the exposed surface of the cerium oxide.

19. The method according to any one of claims 14 to 18, wherein the metal M is Ru and optionally one or more selected from the group consisting of Fe, Co, and Mo, Preferably, wherein the metal M is only Ru.

20. The method according to any one of claims 14 to 19, wherein the catalytic material comprises: 0.01 - 15.0% w / w of the metal M, and 55.0 - 99.9% w / w of the metal oxide.

21. The method according to any one of claims 14 to 20, wherein the method is carried out under batch conditions or continuous flow conditions.

22. The method according to any one of claims 14 to 21, wherein the ammonia is contacted with the catalytic material in the presence of molecular oxygen, Preferably, wherein the molar ratio of ammonia to molecular oxygen is from 1:0.01 to 1:0.

75.

23. The method according to any one of claims 14 to 22, wherein the ammonia is contacted with the catalytic material at a temperature of 150 - 900 °C, preferably at a temperature of 250 - 500 °C.

24. The method according to any one of claims 14 to 23, wherein the ammonia is contacted with the catalytic material at a pressure of 0.1 to 100 bar.

25. The method according to any one of claims 14 to 24, wherein the catalytic material is as defined in any one of claims 1 to 12.

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