Nickel aluminate spinel-based catalyst and preparation method and application thereof

Abstract

The invention relates to a nickel aluminate spinel-based catalyst and a preparation method and application thereof, the chemical formula of the nickel aluminate spinel-based catalyst comprises any one of NiAl2O4, NiAl4Ox, NiAlOx or Ni2AlOx or a combination of at least two of the NiAl2O4, the NiAl4Ox, the NiAlOx and the Ni2AlOx, xlt; 8; the surface of the nickel aluminate spinel-based catalyst is provided with an oxide part coating layer. According to the nickel aluminate spinel-based catalyst provided by the invention, the oxide coating layer can create more nickel-oxide interface sites and enhance the interface interaction while the excellent hydrogen adsorption activation capability of nickel particles is reserved, so that the activation capability on hydrogen and diphenyl ether is promoted on one hand, and on the other hand, the nickel particles are effectively protected; carbon deposition on active sites is inhibited, so that the catalytic hydrogenolysis reaction activity under different reaction conditions is maintained, and meanwhile, the stability under complex reaction conditions is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a nickel aluminum spinel-based catalyst, a preparation method thereof, and applications thereof. Background Art

[0002] Efficiently utilizing lignin from industrial solid waste for resource conversion can close the carbon cycle and achieve a balance between carbon emissions and carbon absorption, which is of great significance for controlling the concentration of carbon dioxide in the atmosphere. Lignin is the second most abundant renewable biomass resource in nature and the only renewable aromatic biomass raw material in the world. As a natural polymer compound second only to cellulose in content, the high-value utilization of lignin has a very positive significance for the development of new energy, substitution of chemical raw materials, and environmental protection. The resource conversion of lignin is mainly achieved through depolymerization into monomers, among which catalytic hydrogenolysis is considered to be one of the most efficient depolymerization technologies currently.

[0003] The cleavage of ether bonds within lignin molecules is key to its selective hydrogenolysis and resource recovery. Current research focuses on hydrogenation depolymerization technologies, particularly catalytic transfer hydrogenolysis using liquid hydrogen sources such as alcohols and acids. On the one hand, the use of liquid hydrogen sources, instead of traditional high-pressure molecular hydrogen sources such as natural gas, effectively reduces industrial energy consumption. On the other hand, liquid hydrogen sources have a low hydrogen activation capacity during the reaction, effectively inhibiting benzene ring hydrogenation reactions and thus improving the controllability of product distribution.

[0004] However, the biggest obstacle to using liquid hydrogen sources such as alcohols for catalytic transfer hydrogenolysis of lignin is that a large amount of alcohol is often required as a solvent during the reaction process, which not only increases the economic cost but also leads to the generation of liquid ketone compounds after the hydrogen transfer reaction, thereby increasing the difficulty of separating the products of aromatic target species such as benzene and phenol after lignin depolymerization.

[0005] Prior art methods utilize trace amounts of alcohols in aqueous phase for reforming hydrogen production, which can serve as an in-situ hydrogen source for the hydrogenolysis of lignin derivatives in a coupled reaction, significantly reducing the amount of alcohol used. Furthermore, since the final products of the reforming reaction are gaseous species such as hydrogen and carbon dioxide, the difficulty of product separation is avoided. Nickel-based catalysts that achieve coupled reactions of alcohol reforming and lignin hydrogenolysis while exhibiting high hydrogen production and hydrogenolysis activity have broad application prospects. However, nickel-based catalysts are prone to carbon deposits in alcohol reforming reactions, blocking active sites and leading to severe catalyst deactivation.

[0006] Therefore, how to develop a nickel-based catalyst that has high hydrogenation depolymerization activity, is not affected by the concentration of alcohol solvents during use, has a longer service life and is more stable, and its preparation method has become a problem that needs to be solved urgently. Summary of the Invention

[0007] To solve the above technical problems, the object of the present invention is to provide a nickel aluminate spinel-based catalyst, its preparation method and uses. The nickel aluminate spinel-based catalyst of the present invention has excellent hydrocracking activity, can stably function under complex reaction conditions, has applicability to different ethylene glycol concentrations, maintains a high reaction activity under different ethylene glycol dosages, has high catalyst stability, and a partial coating structure protects the nickel active sites, and has good anti-poisoning performance.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a nickel aluminate spinel-based catalyst, and the chemical formula of the nickel aluminate spinel-based catalyst includes any one or a combination of at least two of NiAl2O4, NiAl4O x , NiAlO x or Ni2AlO x , where 1 < x < 8; the surface of the nickel aluminate spinel-based catalyst has an oxide partial coating layer.

[0010] The oxide coating layer on the surface of the nickel aluminate spinel-based catalyst accounts for 10% - 60% of the surface area of the nickel aluminate spinel-based catalyst particles. For example, it can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58% or 60%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0011] The nickel aluminate spinel-based catalyst provided by the present invention, while retaining the excellent hydrogen adsorption and activation ability of the nickel particles themselves, the oxide coating layer can create more nickel-oxide interface sites and enhance their interface interaction. On the one hand, it promotes the activation ability of hydrogen and diphenyl ether, and on the other hand, it effectively protects the nickel particles and inhibits carbon deposition on the active sites, thereby maintaining its catalytic hydrocracking reaction activity under different reaction conditions. Compared with the conventional nickel aluminate spinel-based catalyst that is prone to carbon deposition and deactivation, the stability of the nickel aluminate spinel-based catalyst provided by the present invention is greatly improved under complex reaction conditions.

[0012] The nickel aluminum spinel-based catalyst in the present invention exhibits high hydrogen adsorption characteristics and hydrogen activation ability in the H2 pulse adsorption experiment, proving that the surface oxide coating is partially coated, which is different from the complete coating with lower hydrogen adsorption capacity. The partial oxide coating can create more nickel-oxide interface sites and enhance its interface interaction. On the one hand, it promotes the activation ability of hydrogen and diphenyl ether, and on the other hand, it effectively protects the nickel particles and inhibits carbon deposition on the active sites, thereby maintaining its catalytic hydrogenolysis reaction activity under different reaction conditions.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] Preferably, the content of Ni particles in the nickel aluminum spinel-based catalyst is 15wt%-50wt%, for example, it can be 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, or 50wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0015] Preferably, the oxide coating layer comprises amorphous Al2O3.

[0016] Preferably, the thickness of the oxide coating layer is 1 nm-10 nm, for example, 1 nm, 3 nm or 10 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0017] Preferably, the nickel aluminum spinel-based catalyst is also loaded with a transition metal, which includes any one or a combination of at least two of nickel, cobalt, iron, ruthenium, palladium or platinum. Typical but non-limiting combinations include a combination of cobalt and iron, a combination of iron and ruthenium, a combination of ruthenium and palladium, a combination of palladium and platinum, a combination of cobalt, iron and ruthenium, a combination of ruthenium, palladium and platinum, or a combination of cobalt, iron, ruthenium, palladium and platinum, preferably nickel or ruthenium.

[0018] The present invention can also load metal sites with high hydrogen activation ability into the spinel, such as nickel, cobalt, iron, ruthenium, palladium or platinum metal components, to improve the utilization rate of in-situ hydrogen, thereby promoting the hydrogenolysis reaction activity of lignin derivatives. The transition metal elements occupy the Ni sites in the nickel-aluminum spinel-based catalyst, form strong electronic interactions with the Ni sites, enhance the hydrogen activation ability of the nickel-based catalyst, and enable the hydrogen produced by in-situ reforming to be further utilized in the hydrogenolysis reaction, thereby improving the hydrogenolysis reaction activity of the lignin derivatives.

[0019] Preferably, based on the total mass of the nickel-aluminum spinel-based catalyst as 100wt%, the content of transition metal in the nickel-aluminum spinel-based catalyst is 0.1wt%-5wt%, for example, it can be 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 2.0wt%, 3.0wt%, 4.0wt% or 5.0wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0020] In a second aspect, the present invention provides a method for preparing the nickel aluminum spinel-based catalyst as described in the first aspect, the preparation method comprising the following steps:

[0021] Step 1: Mixing nickel salt solution, aluminum salt solution and ammonia water to react to obtain a nickel-aluminum precursor;

[0022] Step 2: annealing the nickel-aluminum precursor to obtain a reaction product;

[0023] Step 3: The reaction product is reduced to obtain a nickel aluminum spinel-based catalyst.

[0024] The present invention adopts a coprecipitation method to prepare a nickel aluminum spinel-based catalyst with nickel aluminum spinel as a precursor, and partially reduces the nickel aluminum spinel-based catalyst to nickel particles by reduction while achieving oxide layer coating. The reduction reaction process is: NiAl2O4→Ni+Al2O3.

[0025] Preferably, the reducing atmosphere is a nitrogen-hydrogen mixture.

[0026] Preferably, the volume fraction of hydrogen in the nitrogen-hydrogen mixture is 1 vol.%-10 vol.%, for example, it can be 1 vol.%, 2 vol.%, 3 vol.%, 4 vol.%, 5 vol.%, 6 vol.%, 7 vol.%, 8 vol.%, 9 vol.% or 10 vol.%, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0027] Preferably, the reduction temperature is 400°C-800°C, for example, it can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] In the present invention, the reduction temperature is further controlled to be 400°C-800°C. The reduction temperature affects the degree of reduction of nickel in the nickel aluminum spinel, thereby achieving a structure partially coated with oxide. Taking NiAl2O4 as an example, if the reduction temperature is too high, NiAl2O4 will completely decompose to form Ni / Al2O3, and the coating structure will be lost; if the reduction temperature is too low, the NiO reduction temperature cannot be reached, and metallic Ni cannot be formed, resulting in a lack of hydrogen production / hydrogenation reaction activity.

[0029] Preferably, the reduction time is 2 h to 4 h, for example, 2 h, 2.5 h, 3 h, 3.5 h or 4 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, the nickel salt solution comprises any one of nickel nitrate solution, nickel sulfate solution or nickel chloride solution, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of nickel nitrate solution and nickel sulfate solution, a combination of nickel sulfate solution and nickel chloride solution, a combination of nickel nitrate solution and nickel chloride solution, and a combination of nickel nitrate solution, nickel sulfate solution and nickel chloride solution, preferably nickel nitrate solution.

[0031] Preferably, the aluminum salt solution comprises any one of aluminum nitrate solution, aluminum sulfate solution or aluminum chloride solution, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of aluminum nitrate solution and aluminum sulfate solution, a combination of aluminum sulfate solution and aluminum chloride solution, a combination of aluminum nitrate solution and aluminum chloride solution, and a combination of aluminum nitrate solution, aluminum sulfate solution and aluminum chloride solution, preferably aluminum nitrate solution.

[0032] Preferably, the molar ratio of the metal ions in the nickel salt solution and the aluminum salt solution is 1:(0.5-8), for example, it can be 1:05, 1:06, 1:07, 1:08, 1:09, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:8, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 1:(0.5-4).

[0033] The present invention further controls the molar ratio of metal ions in the nickel salt solution and the aluminum salt solution to be 1: (0.5-8). In the synthesis process of nickel aluminum spinel, the nickel aluminum ratio can be reasonably adjusted, such as NiAl2O4, NiAl4Ox 、NiAlO x 、Ni2AlO x etc., to appropriately change the structural properties of nickel aluminum spinel.

[0034] Preferably, the molar ratio of metal ions to ammonia in the nickel salt solution is 1:(3-8), for example, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5 or 1:8, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] Preferably, the reaction is carried out with stirring.

[0036] Preferably, the stirring time is 0.5 h-2 h, for example, 0.5 h, 1 h, 1.5 h or 2 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, after the reaction is completed, washing and drying are further performed before obtaining the nickel-aluminum precursor.

[0038] Preferably, the drying temperature is 60°C-90°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the drying time is 8h-12h, for example, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h or 12h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the annealing atmosphere is an argon environment.

[0041] Preferably, the annealing temperature is 750°C-850°C, for example, 750°C, 780°C, 800°C, 820°C or 850°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the annealing time is 5 h-10 h, for example, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, after step 1 and before step 2, the method further comprises: mixing the nickel-aluminum precursor of step 1 with a transition metal salt solution, and drying to obtain a reaction product.

[0044] Preferably, the mixing process is accompanied by stirring, and the stirring time is 1 hour to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the drying temperature is 70°C-80°C, for example, 70°C, 75°C or 80°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] Preferably, the drying time is 8h-12h, for example, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h or 12h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] Preferably, the reduction further includes a passivation treatment.

[0048] Preferably, the passivation atmosphere is a nitrogen-oxygen mixture.

[0049] Preferably, the volume fraction of oxygen in the nitrogen and oxygen mixture is 0.5 vol.%-5 vol.%, for example, it can be 0.5 vol.%, 1 vol.%, 1.5 vol.%, 2 vol.%, 2.5 vol.%, 3 vol.%, 3.5 vol.%, 4 vol.%, 4.5 vol.% or 5 vol.%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] In the present invention, the catalyst is passivated at low temperature in a low-concentration oxygen-nitrogen mixed gas to form a dense oxide layer on the catalyst surface to protect the metallic properties. If passivation is not performed, the metal on the reduced catalyst surface is easily oxidized when exposed to air, thereby destroying the metal active sites.

[0051] Preferably, the passivation temperature is 20°C-30°C, for example, it can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] Preferably, the passivation time is 0.5h-3h, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, or 3h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0054] Step 1: Mix nickel nitrate solution, aluminum nitrate solution and ammonia water according to the molar ratio of metal ions in nickel nitrate solution and aluminum nitrate solution being 1: (0.5-4), the molar ratio of metal ions in nickel nitrate solution to ammonia water being 1: (3-8), stirring and reacting for 0.5h-2h, washing until neutral, and drying the reaction product at 60°C-90°C for 8h-12h to obtain a nickel-aluminum precursor;

[0055] Step 2: annealing the nickel-aluminum precursor at 750° C.-850° C. for 5 h-10 h in an argon atmosphere to obtain a reaction product;

[0056] Step 3: The reaction product is reduced at 500°C-800°C for 2h-4h under a 1vol.%-10vol.% H2 / N2 atmosphere, and then passivated at 20°C-30°C for 0.5h-3h under a 0.5vol.%-5vol.% O2 / N2 atmosphere to obtain a nickel aluminum spinel-based catalyst.

[0057] In a third aspect, the present invention provides a use of the nickel aluminum spinel-based catalyst as described in the first aspect, wherein the nickel aluminum spinel-based catalyst is used for the hydrogenation depolymerization reaction of lignocellulosic compounds.

[0058] The nickel-aluminum spinel-based catalyst provided by the present invention is used in the hydrogenation depolymerization reaction process. On the one hand, it uses trace amounts of alcohols in the aqueous phase for reforming hydrogen production, which serves as an in-situ hydrogen source for the hydrogenolysis reaction in the same pot coupled reaction, thereby significantly reducing the amount of alcohol used. On the other hand, because the final products of the reforming reaction are gaseous species such as hydrogen and carbon dioxide, the problem of product separation is avoided. The nickel-aluminum spinel-based catalyst is not prone to carbon deposition in the alcohol reforming reaction and has a longer service life.

[0059] Preferably, the nickel aluminum spinel-based catalyst is used for aqueous phase reforming of alcohols coupled with hydrogenolysis of lignin derivatives.

[0060] Preferably, the nickel-aluminum spinel-based catalyst has a service life of ≥10 times for aqueous phase reforming of alcohols coupled with hydrogenolysis of lignin derivatives.

[0061] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0062] Compared with the prior art, the present invention has at least the following beneficial effects:

[0063] (1) The nickel-aluminum spinel-based catalyst provided by the present invention, while retaining the excellent hydrogen adsorption activation ability of the nickel particles themselves, the oxide coating layer can create more nickel-oxide interface sites, enhancing their interfacial interactions. On the one hand, it promotes the activation ability of hydrogen and diphenyl ether, and on the other hand, it effectively protects the nickel particles and inhibits carbon deposition on the active sites, thereby maintaining its catalytic hydrogenolysis reaction activity under different reaction conditions. Compared with conventional nickel-aluminum spinel-based catalysts that are easily deactivated by carbon deposition, the stability of the nickel-aluminum spinel-based catalyst provided by the present invention under complex reaction conditions is greatly improved.

[0064] (2) The present invention adopts a co-precipitation method to prepare a nickel aluminum spinel-based catalyst with nickel aluminum spinel as a precursor, and partially reduces the nickel aluminum spinel-based catalyst to nickel particles by reduction while achieving the coating of the oxide layer. The reduction reaction process is: NiAl2O4→Ni+Al2O3.

[0065] (3) The nickel-aluminum spinel-based catalyst provided by the present invention is applied to the hydrogenation depolymerization reaction process. On the one hand, a trace amount of alcohol is used in the aqueous phase for reforming hydrogen production, which serves as an in-situ hydrogen source for the hydrogenolysis reaction in the same pot coupled reaction, thereby significantly reducing the amount of alcohol used. On the other hand, since the final products of the reforming reaction are gaseous species such as hydrogen and carbon dioxide, the problem of product separation is avoided. The nickel-aluminum spinel-based catalyst is not prone to carbon deposition in the alcohol reforming reaction and has a longer service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 is a HRTEM image of the nickel aluminum spinel-based catalyst prepared in Example 1 of the present invention;

[0067] Figure 2 The AC-STEM image, EDS-mapping image and element content analysis image of the nickel-aluminum spinel-based catalyst prepared in Example 1 of the present invention are shown;

[0068] Figure 3 The reaction activities of the catalysts prepared in Example 1 and Comparative Example 1 of the present invention under different concentrations of ethylene glycol;

[0069] Figure 4 The reaction stability test of the catalysts prepared in Example 1 and Comparative Example 1 of the present invention in the presence of 0.2 wt.% ethylene glycol was conducted;

[0070] Figure 5 This is a reaction selectivity test of the catalyst prepared in Example 1 of the present invention in the presence of 0.2 wt.% ethylene glycol. DETAILED DESCRIPTION

[0071] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0072] In the following examples and comparative examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the field; unless otherwise specified, the experimental methods and technical means used were conventional methods and means in the field.

[0073] Example 1

[0074] This embodiment provides a nickel aluminum spinel-based catalyst, the chemical formula of which is NiAl2O4; the surface of the nickel aluminum spinel-based catalyst contains an amorphous Al2O3 partial coating layer with a thickness of 2 nm.

[0075] The preparation method of the nickel aluminum spinel-based catalyst provided in this embodiment comprises the following steps:

[0076] Step 1: Mix nickel nitrate solution, aluminum nitrate solution and ammonia water in a molar ratio of nickel to aluminum ions of 1:2, and a molar ratio of metal ions to ammonia water of 1:4 in the nickel nitrate solution. Stir and react for 1 hour, wash until neutral, and dry at 80°C for 10 hours to obtain a nickel-aluminum precursor.

[0077] Step 2: annealing the nickel-aluminum precursor at 800° C. for 8 h in an argon atmosphere to obtain a reaction product;

[0078] Step 3: The reaction product was reduced at 600°C for 3 h in a 5 vol.% H2 / N2 (100 mL / min) atmosphere, and then passivated at 25°C for 1 h in a 1 vol.% O2 / N2 (100 mL / min) atmosphere to obtain a nickel aluminum spinel-based catalyst.

[0079] The HRTEM image of the prepared nickel aluminum spinel-based catalyst is as follows: Figure 1 As shown, from Figure 1 It can be seen that after the reduction process, Ni metal particles with a size of ~10 nm are formed on the surface of nickel aluminum spinel.

[0080] The AC-STEM image of the prepared nickel aluminum spinel-based catalyst is shown in Figure 2 As shown, from Figure 2As can be seen from the graph, the surface of the nickel-aluminum spinel-based catalyst contains a 2nm thick coating layer, and the formation of the Al2O3 coating layer can be visually confirmed by EDS-mapping. Furthermore, the elemental content analysis chart shows that the catalyst contains Ni~24.8±3.8wt.%, Al~34.4±7.2wt.%, and O~40.8±3.0wt.%, with the Ni content close to the theoretically calculated 33wt.%.

[0081] The reaction activities of the prepared nickel aluminum spinel-based catalyst under different concentrations of ethylene glycol are as follows: Figure 3 As shown in the figure, it can be seen that the reaction rate of hydrogenolysis to produce aromatic compounds is very high, and it has good adaptability to different ethylene glycol concentrations.

[0082] The reaction stability test of the prepared nickel aluminum spinel-based catalyst in 0.2 wt.% ethylene glycol is as follows: Figure 4 As shown in the figure, it can be seen that the nickel aluminum spinel-based catalyst can maintain a high conversion rate in multiple cycle tests and its stability is greatly improved.

[0083] The reaction selectivity of the prepared nickel aluminum spinel-based catalyst under 0.2 wt.% ethylene glycol was tested as follows: Figure 5 As shown in the figure, it can be seen that the selectivity of the nickel aluminum spinel-based catalyst for phenol and benzene produced by hydrogenolysis can be maintained at around 80% as the number of cycles increases. The nickel aluminum spinel-based catalyst has excellent selectivity and stability.

[0084] Example 2

[0085] This embodiment provides a nickel aluminum spinel-based catalyst, the chemical formula of which is NiAl2O4; the surface of the nickel aluminum spinel-based catalyst contains a partial coating layer of Al2O3 oxide with a thickness of 3 nm.

[0086] The preparation method of the nickel aluminum spinel-based catalyst provided in this embodiment comprises the following steps:

[0087] Step 1: Mix nickel sulfate solution, aluminum sulfate solution and ammonia water in a molar ratio of nickel and aluminum ions of 1:2, and a molar ratio of metal ions to ammonia water in nickel nitrate solution of 1:5, stir and react for 2 hours, wash to neutrality, and dry at 60°C for 12 hours to obtain a nickel-aluminum precursor;

[0088] Step 2: annealing the nickel-aluminum precursor at 650° C. for 10 h in an argon atmosphere to obtain a reaction product;

[0089] Step 3: The reaction product was reduced at 800°C for 4 h in a 2 vol.% H2 / N2 (100 mL / min) atmosphere, and then passivated at 20°C for 3 h in a 1 vol.% O2 / N2 (100 mL / min) atmosphere to obtain a nickel aluminum spinel-based catalyst.

[0090] Example 3

[0091] This embodiment provides a nickel aluminum spinel-based catalyst, the chemical formula of the nickel aluminum spinel-based catalyst is Ni2Al1O 3.5 ; The surface of the nickel aluminum spinel-based catalyst contains a partial coating layer of Al2O3 oxide with a thickness of 4nm.

[0092] The preparation method of the nickel aluminum spinel-based catalyst provided in this embodiment comprises the following steps:

[0093] Step 1: Mix nickel sulfate solution, aluminum sulfate solution and ammonia water in a molar ratio of nickel and aluminum ions of 2:1, and a molar ratio of metal ions to ammonia water in nickel nitrate solution of 1:4, stir and react for 1 hour, wash to neutrality, and dry at 90°C for 12 hours to obtain a nickel-aluminum precursor;

[0094] Step 2: annealing the nickel-aluminum precursor at 800° C. for 10 h in an argon atmosphere to obtain a reaction product;

[0095] Step 3: The reaction product was reduced at 700°C for 4 h in a 2 vol.% H2 / N2 (100 mL / min) atmosphere, and then passivated at 20°C for 4 h in a 1 vol.% O2 / N2 (100 mL / min) atmosphere to obtain a nickel aluminum spinel-based catalyst.

[0096] Example 4

[0097] This embodiment provides a nickel aluminum spinel-based catalyst, wherein the chemical formula of the nickel aluminum spinel-based catalyst is Ni / NiAl2O4; the surface of the nickel aluminum spinel-based catalyst comprises a partial coating layer of Al2O3 oxide with a thickness of 1 nm; wherein the loading amount of transition metal nickel accounts for 5.0 wt.% of the total mass of the nickel aluminum spinel-based catalyst;

[0098] The preparation method of the nickel aluminum spinel-based catalyst provided in this embodiment comprises the following steps:

[0099] Step 1: mixing nickel nitrate solution, aluminum nitrate solution and ammonia water in a molar ratio of nickel and aluminum ions of 1:2, and a molar ratio of metal ions to ammonia water in the nickel nitrate solution of 1:3, stirring and reacting for 1 hour, washing until neutral, and drying at 80°C for 10 hours to obtain a nickel-aluminum precursor; the nickel-aluminum precursor is annealed at 800°C for 8 hours under an argon atmosphere to obtain nickel-aluminum spinel;

[0100] Step 2: Using nickel aluminum spinel as a carrier, add an appropriate amount of nickel nitrate solution (based on the mass fraction of metallic nickel and NiAl2O4 being 5%), stir for 2 hours, and then dry at 80°C for 10 hours to obtain a reaction product;

[0101] Step 3: The reaction product was reduced at 600°C for 3 h in a 5 vol.% H2 / N2 atmosphere (100 mL / min), and then passivated at 25°C for 1 h in a 1 vol.% O2 / N2 atmosphere (100 mL / min) to obtain a Ni / NiAl2O4 catalyst.

[0102] Example 5

[0103] This embodiment provides a nickel aluminum spinel-based catalyst, wherein the chemical formula of the nickel aluminum spinel-based catalyst is Ru / NiAl2O4; the surface of the nickel aluminum spinel-based catalyst comprises a partial coating layer of Al2O3 oxide with a thickness of 2 nm; wherein the loading amount of transition metal ruthenium accounts for 0.5 wt.% of the total mass of the nickel aluminum spinel-based catalyst;

[0104] The preparation method of the nickel aluminum spinel-based catalyst provided in this embodiment comprises the following steps:

[0105] Step 1: mixing nickel nitrate solution, aluminum nitrate solution and ammonia water in a molar ratio of nickel and aluminum ions of 1:2, wherein the molar ratio of metal ions to ammonia water in the nickel nitrate solution is 1:2, stirring and reacting for 1 hour, washing until neutral, and drying at 80°C for 10 hours to obtain a nickel-aluminum precursor; the nickel-aluminum precursor is annealed at 800°C for 8 hours under an argon atmosphere to obtain nickel-aluminum spinel;

[0106] Step 2: Using nickel aluminum spinel as a carrier, add an appropriate amount of ruthenium nitrate solution (wherein the mass fraction of ruthenium and NiAl2O4 is 5%), stir for 2 hours, and then dry at 80°C for 10 hours to obtain a reaction product;

[0107] Step 3: The reaction product was reduced at 600°C for 3 h in a 5 vol.% H2 / N2 (100 mL / min) atmosphere, and then passivated at 25°C for 1 h in a 1 vol.% O2 / N2 (100 mL / min) atmosphere to obtain a Ru / NiAl2O4 catalyst.

[0108] Example 6

[0109] This embodiment provides a nickel aluminum spinel-based catalyst, which is different from Example 1 only in that the reduction temperature is 400° C. when preparing the nickel aluminum spinel-based catalyst.

[0110] Example 7

[0111] This embodiment provides a nickel aluminum spinel-based catalyst, which is different from Example 3 only in that the reduction temperature is 400° C. when preparing the nickel aluminum spinel-based catalyst.

[0112] Example 8

[0113] This embodiment provides a nickel-aluminum spinel-supported nickel-based catalyst, which differs from Example 4 only in that the reduction temperature is 400°C when preparing the Ni / NiAl2O4 catalyst.

[0114] Example 9

[0115] This embodiment provides a nickel aluminum spinel-based catalyst, which differs from Example 5 only in that, when preparing the nickel aluminum spinel-based catalyst, the loading amount of transition metal nickel accounts for 10 wt.% of the total mass of the nickel aluminum spinel-based catalyst.

[0116] Example 10

[0117] This embodiment provides a nickel aluminum spinel-based catalyst, which differs from Example 1 only in that the reduction temperature is 850° C. when preparing the nickel aluminum spinel-based catalyst.

[0118] Example 11

[0119] This embodiment provides a nickel aluminum spinel-based catalyst, which differs from Example 4 only in that the reduction temperature is 850° C. when preparing the nickel aluminum spinel-based catalyst.

[0120] Comparative Example 1

[0121] This comparative example provides a Ni / Al2O3-based catalyst. A conventional Al2O3-loaded Ni / Al2O3-based catalyst was prepared by a wet impregnation method. An aqueous nickel nitrate solution with the same theoretical Ni content (33 wt.%) as that in NiAl2O4 was added to γ-Al2O3 powder and stirred thoroughly for 10 minutes. The mixture was dried in an oven at 80°C overnight. The dried sample was calcined in an air flow at 400°C for 3 hours and reduced in 5 vol.% H2 / N2 (100 mL / min) at 600°C for 3 hours. It was then passivated with 1 vol.% O2 / N2 (100 mL / min) at 25°C for 1 hour.

[0122] Comparative Example 2

[0123] This comparative example provides a nickel-based catalyst completely coated with aluminum oxide. A nickel hydroxide solution and an aluminum nitrate solution are mixed according to a nickel and aluminum oxide mass ratio of 33 wt %. After stirring for 1 hour, the mixture is hydrothermally treated at 120° C. for 12 hours, washed until neutral, and dried at 80° C. for 12 hours to obtain a nickel-aluminum precursor.

[0124] The nickel-aluminum precursor was calcined in an air flow at 400°C for 3 h and reduced in 5 vol.% H2 / N2 (100 mL / min) at 600°C for 3 h, followed by passivation with 1 vol.% O2 / N2 (100 mL / min) at 25°C for 1 h.

[0125] Test Method: The catalysts prepared in the Examples and Comparative Examples were tested. The hydrogenolysis reaction of lignin and its model derivatives was carried out in a batch pressurized reactor. The hydrotreatment reaction was carried out in a stainless steel batch reactor.

[0126] (1) Reactivity test: In the model reaction, 1 g of diphenyl ether, 50 mg of catalyst, and ethylene glycol water solvents of different concentrations were loaded into the reactor. After purging with 1 MPa N2 for 6 times and releasing the pressure to ambient pressure, 1 MPa N2 was added and the reactor was heated to 240°C (15°C / min). At this time, stirring (600 rpm) was started and the reaction was continued for 2 hours. The products were analyzed by gas chromatography-mass spectrometry. The test results of Example 1 and Comparative Example 1 are shown as follows: Figure 3 shown.

[0127] (2) Stability Test: In a model reaction, 1 g of diphenyl ether, 50 mg of catalyst, and a 0.2 wt.% aqueous ethylene glycol solution were loaded into a reactor. After purging with 1 MPa of N2 six times and releasing the pressure to ambient pressure, 1 MPa of N2 was added. The reactor was heated to 240°C (15°C / min), stirred at 600 rpm, and the reaction continued for 2 h. The product was analyzed by gas chromatography-mass spectrometry. The test results are shown in Table 1 below.

[0128] The reaction stability test results of Example 1 and Comparative Example 1 are as follows Figure 4 and Figure 5 shown.

[0129] Table 1

[0130] <![CDATA[Reactivity (mmol·g -1 ·h -1 )]]> Lignin derivative hydrogenolysis conversion rate (%) Example 1 14.3 27.8 Example 2 15.7 30.6 Example 3 15.2 28.5 Example 4 24.0 46.7 Example 5 33.8 60.1 Example 6 0.4 0.7 Example 7 3.21 5.6 Example 8 11.2 19.8 Example 9 24.6 44.2 Example 10 8.3 17.3 Example 11 14.3 27.6 Comparative Example 1 6.9 13.4 Comparative Example 2 5.2 10.6

[0131] The test results show that:

[0132] (1) It can be seen from Examples 1 to 5 that the surface of the nickel-aluminum spinel-based catalyst provided by the present invention is partially coated with an oxide coating layer. The oxide coating layer can create more nickel-oxide interface sites and enhance its interface interaction. On the one hand, it promotes the activation ability of hydrogen and diphenyl ether. On the other hand, it effectively protects the nickel particles and inhibits carbon deposition on the active sites, thereby maintaining its catalytic hydrogenolysis reaction activity under different reaction conditions. The nickel-aluminum spinel-based catalyst maintains a high reaction activity under different ethylene glycol dosages and has high catalyst stability.

[0133] (2) By comparing Example 1 with Example 6, Example 3 with Example 7, and Example 4 with Example 8, it can be seen that the present invention further controls the reduction temperature of the nickel aluminum spinel-based catalyst to be 500°C-800°C. The reduction temperature affects the degree of reduction of Ni in the NiAl2O4 structure, thereby affecting the number of Ni active sites, and on the other hand, affects the interaction between the loaded metal and NiAl2O4, thereby achieving efficient diphenyl ether conversion capacity. If the reduction temperature is too low, such as NiAl2O4 reduced at 400°C, the too low reduction temperature is not enough to reach the reduction temperature of nickel oxide in NiAl2O4, then the number of Ni active sites is significantly reduced, and the interaction between Ni and NiAl2O4 induced by the reduction process is severely limited, thereby seriously reducing the reaction activity.

[0134] (3) By comparing Example 1 with Example 10 and Example 4 with Example 11, it can be seen that the present invention further controls the reduction temperature to 500°C-800°C. When the reduction temperature is too high, the NiAl2O4 structure is completely reduced to Ni / Al2O3, thereby losing the coating structure, and the Ni-Al interface effect is significantly reduced, resulting in a decrease in activity.

[0135] (4) By comparing Example 5 with Example 9, it can be seen that the present invention can further improve the reaction activity of the catalyst and the utilization rate of in-situ hydrogen by further controlling the content of the transition metal loaded in the nickel-aluminum spinel-based catalyst to 0.1wt%-5wt%, thereby promoting the hydrogenolysis reaction activity of the lignin derivative. If the loaded transition metal content is too low, the performance improvement is not obvious. If the loaded transition metal content is too high, the cost is further increased.

[0136] (5) Pass Figure 3-Figure 5 From the comparison between Example 1 and Comparative Example 1, it can be seen that the spinel-structured catalyst prepared by the present invention, combined with the subsequent reduction treatment to obtain a nickel-aluminum spinel-based catalyst, has high catalytic activity, long service life, and high selectivity; while the Ni / Al2O3 catalyst prepared by the traditional method in Comparative Example 1 has exposed metal nickel particles formed on the surface, which not only reduces the nickel-aluminum interface sites, resulting in low catalytic activity, but also poor stability of the catalyst, and a very short service life. In the third cycle experiment, the activity basically dropped to 0%.

[0137] (6) By comparing Example 1 with Comparative Example 2, it can be seen that if fully coated Ni@Al2O3 is formed, its Ni active sites are over-encapsulated, reducing the exposure of the catalyst active sites, resulting in a significant decrease in the activation ability for hydrogen and a significant decrease in the hydrogenolysis reaction activity.

[0138] In summary, the surface of the nickel-aluminum spinel-based catalyst provided by the present invention is partially coated with an oxide coating layer. The oxide coating layer can create more nickel-oxide interface sites and enhance its interface interaction. On the one hand, it promotes the activation ability of hydrogen and diphenyl ether. On the other hand, it effectively protects the nickel particles and inhibits carbon deposition on the active sites, thereby maintaining its catalytic hydrogenolysis reaction activity under different reaction conditions. The nickel-aluminum spinel-based catalyst maintains a high reaction activity under different ethylene glycol dosages, and the catalyst is highly stable and resistant to poisoning, and has very good application prospects.

[0139] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A nickel aluminum spinel-based catalyst, characterized in that The chemical formula of the nickel aluminum spinel-based catalyst includes NiAl2O4, NiAl4O x 、NiAlO x or Ni2AlO x Any one or a combination of at least two of <x<8; The surface of the nickel aluminum spinel-based catalyst has a partial oxide coating layer.

2. The nickel-aluminum spinel-based catalyst according to claim 1, characterized in that The content of nickel particles in the nickel aluminum spinel-based catalyst is 15wt%-50wt%; Preferably, the oxide coating layer comprises amorphous Al2O3; Preferably, the thickness of the oxide coating layer is 1 nm-10 nm; Preferably, the nickel aluminum spinel-based catalyst is further loaded with a transition metal; the transition metal comprises any one or a combination of at least two of nickel, cobalt, iron, ruthenium, palladium or platinum; Preferably, based on 100 wt% of the total mass of the nickel-aluminum spinel-based catalyst, the content of the transition metal in the nickel-aluminum spinel-based catalyst is 0.1 wt%-5 wt%.

3. A method for preparing the nickel aluminum spinel-based catalyst according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: Step 1: Mixing nickel salt solution, aluminum salt solution and ammonia water to react to obtain a nickel-aluminum precursor; Step 2: annealing the nickel-aluminum precursor to obtain a reaction product; Step 3: The reaction product is reduced to obtain a nickel aluminum spinel-based catalyst.

4. The preparation method according to claim 3, characterized in that The reducing atmosphere is a nitrogen-hydrogen mixed gas; Preferably, the volume fraction of hydrogen in the nitrogen-hydrogen mixture is 1 vol.%-10 vol.%; Preferably, the reduction temperature is 500°C-800°C; Preferably, the reduction time is 2h-4h.

5. The preparation method according to claim 3 or 4, characterized in that The nickel salt solution includes any one of nickel nitrate solution, nickel sulfate solution or nickel chloride solution, or a combination of at least two thereof; Preferably, the aluminum salt solution comprises any one of aluminum nitrate solution, aluminum sulfate solution or aluminum chloride solution, or a combination of at least two thereof; Preferably, the molar ratio of metal ions in the nickel salt solution and the aluminum salt solution is 1:(0.5-8), preferably 1:(0.5-4); Preferably, the molar ratio of metal ions to ammonia water in the nickel salt solution is 1:(3-8).

6. The preparation method according to any one of claims 3 to 5, characterized in that The reaction process is accompanied by stirring; Preferably, the stirring time is 0.5h-2h; Preferably, after the reaction is completed, washing and drying are further performed before obtaining the nickel-aluminum precursor; Preferably, the drying temperature is 60°C-90°C; Preferably, the drying time is 8h-12h.

7. The preparation method according to any one of claims 3 to 6, characterized in that The annealing atmosphere is an argon environment; Preferably, the annealing temperature is 600°C-900°C; Preferably, the annealing time is 5h-10h.

8. The preparation method according to any one of claims 3 to 7, characterized in that After step 1 and before step 2, the following steps are also included: mixing the nickel-aluminum precursor of step 1 with the transition metal salt solution, and drying to obtain a reaction product; Preferably, the mixing process is accompanied by stirring, and the stirring time is 1h-3h; Preferably, the drying temperature is 70°C-80°C; Preferably, the drying time is 8h-12h.

9. The preparation method according to any one of claims 3 to 8, characterized in that After the reduction, a passivation treatment is also performed; Preferably, the passivation atmosphere is a nitrogen-oxygen mixture; Preferably, the volume fraction of oxygen in the nitrogen-oxygen mixture is 0.5 vol.%-5 vol.%; Preferably, the passivation temperature is 20°C-30°C; Preferably, the passivation time is 0.5h-3h.

10. Use of the nickel aluminum spinel-based catalyst according to claim 1 or 2, characterized in that: The nickel aluminum spinel-based catalyst is used for the hydrogenation depolymerization reaction of lignocellulosic compounds.

Images