Oxide catalyst and method for producing hydrocarbon

Abstract

To provide a new catalyst exhibiting an excellent yield in an oxidative coupling reaction of methane.SOLUTION: An oxide catalyst comprising: at least aluminum and cerium as contained elements; and at least one selective element selected from the group consisting of Group 1 elements other than hydrogen, Group 2 elements, and Group 3 elements other than cerium as the contained elements.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an oxide catalyst and a method for producing hydrocarbons. [Background technology]

[0002] Hydrocarbons with two carbon atoms (such as ethane and ethylene) are industrially important compounds because they serve as raw materials for a variety of compounds. Hydrocarbons with a carbon number of 2 are generally produced by cracking naphtha. However, from the perspective of effective resource utilization, the production of hydrocarbons with a carbon number of 2 by the oxidative coupling of methane (OCM), the main component of natural gas, is being considered.

[0003] As a catalyst that allows the OCM reaction to proceed smoothly, for example, a catalyst containing sodium and manganese, as well as silicon oxide and tungsten oxide (Mn / Na2WO4 / SiO2 catalyst) is known (Non-Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Non-Patent Document 1] Journal of Catalysis,1998,222-230 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, catalysts such as those described in Non-Patent Document 1 above have been known for the OCM reaction, but the development of a new catalyst that shows excellent yields has been desired.

[0006] Therefore, an object of the present invention is to provide a novel catalyst that exhibits an excellent yield in the oxidative coupling of methane (OCM) reaction. Another object of the present invention is to provide a method for producing hydrocarbons. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. That is, they have found that the above problems can be solved by the following configuration.

[0008] [1] An oxide catalyst, The contained elements include at least aluminum and cerium, The oxide catalyst contains, as the contained element, at least one selected element selected from the group consisting of Group 1 elements other than hydrogen, Group 2 elements, and Group 3 elements other than cerium. [2] The oxide catalyst according to [1], wherein the optional element includes at least one element selected from the group consisting of alkali metal elements, alkaline earth metal elements, and lanthanoid elements. [3] The oxide catalyst according to [1] or [2], wherein the optional element includes at least one selected from the group consisting of alkali metal elements, alkaline earth metal elements, and lanthanum. [4] The oxide catalyst according to any one of [1] to [3], wherein the optional element includes at least one selected from the group consisting of potassium, calcium, strontium, and lanthanum. [5] In addition to aluminum and cerium, the above-mentioned contained elements include: a first element selected from the group consisting of potassium, calcium, and strontium, and a second element that is a lanthanoid element other than lanthanum; containing lanthanum and a lanthanoid element other than lanthanum or strontium, containing only one tertiary element selected from the group consisting of potassium and calcium, or The oxide catalyst according to any one of [1] to [3], which contains one third element selected from the group consisting of potassium and calcium, and one fourth element selected from the above Group 1 elements other than potassium. [6] A method for producing hydrocarbons, comprising a step of carrying out oxidative coupling of methane using the oxide catalyst according to any one of [1] to [5] to produce hydrocarbons having two carbon atoms. [Effects of the Invention]

[0009] According to the present invention, a novel catalyst that exhibits excellent yields in the OCM reaction can be provided. The present invention also provides a method for producing hydrocarbons. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment.

[0011] The following describes the meaning of each description in this specification. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0012] In this specification, Group 1 elements other than hydrogen refer to lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Also, in this specification, alkali metals refer to the same elements as the above Group 1 elements other than hydrogen. In this specification, Group 2 elements refer to beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).Alkaline earth metals refer to calcium (Ca), strontium (Sr), barium (Ba), and radon (Ra). In this specification, Group 3 elements refer to scandium (Sc), yttrium (Y), lanthanoid elements, and actinoid elements. In this specification, the lanthanoid elements refer to lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). As used herein, actinide elements refer to actinium (Ac), thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), berkelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), mendelevium (Md), nobelium (No), and lawrencium (Lr).

[0013] As used herein, "exhibiting an excellent yield in the OCM reaction" means that the yield of hydrocarbons having two carbon atoms is excellent. Examples of hydrocarbons having two carbon atoms include ethylene and ethane. Furthermore, when only one of ethylene and ethane is produced in the OCM reaction, the yield of hydrocarbons having two carbon atoms is calculated using the amount of either ethylene or ethane produced. Furthermore, when both ethylene and ethane are produced in the OCM reaction, the yield is calculated using the total amount of ethylene and ethane produced.

[0014] <Oxide catalyst> The oxide catalyst of the present invention contains at least aluminum (Al) and cerium (Ce) as contained elements, and the contained elements include at least one selected element from the group consisting of Group 1 elements other than hydrogen, Group 2 elements, and Group 3 elements other than Ce. As a result of various investigations, the present inventors have surprisingly found that oxide catalysts containing the above-mentioned elements exhibit excellent yields in the OCM reaction. Hereinafter, showing an excellent yield in the OCM reaction will also be simply referred to as "excellent yield." The oxide catalyst of the present invention will be described in detail below.

[0015] [Contained elements] The oxide catalyst of the present invention contains at least Al and Ce as contained elements. The oxide catalyst of the present invention also contains at least one element (hereinafter also referred to as "selective element") selected from the group consisting of Group 1 elements other than hydrogen, Group 2 elements, and Group 3 elements other than Ce. That is, the oxide catalyst of the present invention contains Al, Ce, and the selective element. The oxide catalyst of the present invention contains oxygen (O).

[0016] The oxide catalyst of the present invention preferably contains, as the optional element, at least one element selected from the group consisting of alkali metal elements, alkaline earth metal elements, and lanthanoid elements. Furthermore, the oxide catalyst of the present invention more preferably contains at least one selected from the group consisting of alkali metal elements, alkaline earth metal elements, and La as the optional element. Furthermore, the oxide catalyst of the present invention preferably contains at least one element selected from the group consisting of K, Ca, Sr, and La as the optional element.

[0017] The contained elements in the oxide catalyst of the present invention preferably include two or more elements in addition to Al and Ce. The number of types of the selected elements is preferably four or less, and more preferably three or less. The number of types of the selected elements may be two.

[0018] A preferred combination of contained elements is one that includes, in addition to Al and Ce, one first element selected from the group consisting of K, Ca, and Sr, and one second element that is a lanthanoid element other than La. Furthermore, as a combination of contained elements, in addition to Al and Ce, a combination containing La and a lanthanoid element other than La or strontium is also preferable. Furthermore, as a combination of contained elements, a combination containing only one third element selected from the group consisting of K and Ca in addition to Al and Ce is also preferred. Furthermore, a combination of contained elements that includes, in addition to Al and Ce, one third element selected from the group consisting of K and Ca, and one fourth element selected from Group 1 elements other than K is also preferred.

[0019] The oxide catalyst of the present invention may contain elements other than those mentioned above. Examples of elements other than those mentioned above include transition metal elements excluding Group 3 elements. Examples of transition metal elements excluding Group 3 elements include Group 4 elements (titanium (Ti), zirconium (Zr), and hafnium (Hf)), Group 5 elements (vanadium (V), niobium (Nb), and tantalum (Ta)), and Group 6 elements (chromium (Cr), molybdenum (Mo), and tungsten (W)). Among these, Zr, Hf, Mo, or W is preferred as the transition metal element excluding Group 3 elements, and Zr or W is more preferred.

[0020] More specific combinations of contained elements are listed below. The combinations of contained elements include a combination of Al, Ce, K, and Tb, a combination of Al, Ce, K, and Rb, a combination of Al, Ce, K, a combination of Al, Ce, K, and W, a combination of Al, Ce, K, and Li, a combination of Al, Ce, K, and Ba, a combination of Al, Ce, K, and Na, a combination of Al, Ce, K, and Zr, a combination of Al, Ce, K, and La, a combination of Al, Ce, K, and Sr, a combination of Al, Ce, K, and Cs, a combination of Al, Ce, Ca, and Tb, a combination of Al, Ce, and Ca, a combination of Al, Ce, Ca, and Y, and A. Examples of the combinations include a combination of Al, Ce, Ca, and Rb, a combination of Al, Ce, Ca, and Nd, a combination of Al, Ce, Ca, and Zr, a combination of Al, Ce, La, and Tb, a combination of Al, Ce, La, and Sr, a combination of Al, Ce, La, and Ho, a combination of Al, Ce, and La, a combination of Al, Ce, Sr, and Pr, a combination of Al, Ce, Sr, and Sm, a combination of Al, Ce, Sr, and Nd, a combination of Al, Ce, Cs, and Tm, a combination of Al, Ce, and Gd, a combination of Al, Ce, and Nd, and a combination of Al, Ce, and Sm. Among them, the combinations of contained elements include the combination of Al, Ce, K, and Tb, the combination of Al, Ce, K, and Rb, the combination of Al, Ce, K, the combination of Al, Ce, K, and Li, the combination of Al, Ce, K, and Ba, the combination of Al, Ce, K, and Zr, the combination of Al, Ce, K, and La, the combination of Al, Ce, K, and Sr, the combination of Al, Ce, Ca, and Tb, the combination of Al, Ce, and Ca, the combination of Al, Ce, Ca, and Y, and the combination of Al, Ce, and C. A combination of Al and Rb, a combination of Al, Ce, Ca, and Zr, a combination of Al, Ce, La, and Tb, a combination of Al, Ce, La, and Sr, a combination of Al, Ce, La, and Ho, a combination of Al, Ce, and La, a combination of Al, Ce, Sr, and Pr, a combination of Al, Ce, Sr, and Sm, a combination of Al, Ce, Sr, and Nd, a combination of Al, Ce, Cs, and Tm, a combination of Al, Ce, and Nd, or a combination of Al, Ce, and Sm is preferred.

[0021] (Element ratio in oxide catalyst) The ratio of constituent elements in the oxide catalyst of the present invention is not particularly limited. The oxide catalyst of the present invention contains Al and Ce as contained elements, and further contains the above-mentioned selected elements as contained elements. The oxide catalyst of the present invention also contains O.

[0022] In the oxide catalyst of the present invention, the Al content is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more, based on the total content of Al, Ce, and the optional elements. Also, in the oxide catalyst of the present invention, the Al content is preferably 99 mol% or less, more preferably 98 mol% or less, and even more preferably 95 mol% or less, based on the total content of Al, Ce, and the optional elements.

[0023] In the oxide catalyst of the present invention, the Ce content is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 3 mol% or more, based on the total content of Al, Ce, and the optional elements. Also, in the oxide catalyst of the present invention, the Ce content is preferably 20 mol% or less, more preferably 15 mol% or less, and even more preferably 10 mol% or less, based on the total content of Al, Ce, and the optional elements.

[0024] In the oxide catalyst of the present invention, the total content of the selective elements is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 3 mol% or more, based on the total content of Al, Ce, and the selective elements. Also, in the oxide catalyst of the present invention, the content of the selective elements is preferably 40 mol% or less, more preferably 20 mol% or less, and even more preferably 15 mol% or less, based on the total content of Al, Ce, and the selective elements.

[0025] In the oxide catalyst of the present invention, the O content is preferably 30 mol% or more, more preferably 35 mol% or more, even more preferably 40 mol% or more, and particularly preferably 50 mol% or more, based on the total atoms of the oxide catalyst. The O content is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 62 mol% or less, based on the total atoms of the oxide catalyst.

[0026] The oxide catalyst of the present invention may contain elements other than those mentioned above. Examples of elements other than those mentioned above include hydrogen (H), carbon (C), nitrogen (N), fluorine (F), phosphorus (P), sulfur (S), chlorine (Cl), and bromine (Br). In the oxide catalyst of the present invention, the total content of Al, Ce, optional elements, and O is preferably 70 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and particularly preferably 99 mass% or more, based on the total mass of the oxide catalyst. The upper limit of the total content may be 100 mass%.

[0027] (Arrangement of elements in oxide catalyst) The arrangement of elements in the oxide catalyst of the present invention is not particularly limited. The oxide catalyst may be a composite oxide in which the above-mentioned constituent elements are uniformly mixed, or the oxide of each element may be unevenly distributed in a part of the oxide catalyst. In particular, it is preferable that Al, Ce, and at least one of the above-mentioned selective elements are present on the surface of the oxide catalyst, more preferably at least two of them, and even more preferably three of them. When at least one of Al, Ce, and the optional element is present on the surface of the oxide catalyst, the element may be unevenly distributed in a certain area on the surface of the oxide catalyst, or may be uniformly distributed on the surface of the oxide catalyst.

[0028] It is also preferable that the oxide of each of the above constituent elements is present in a part (e.g., the surface) of the oxide catalyst, and that the total content of the constituent elements is within the above-mentioned preferred range relative to the total mass of the oxide catalyst. One example of the above embodiment is one in which oxides of Ce and the selected elements are supported on Al2O3 as a support. The oxides of the above elements may be composite oxides containing two or more elements selected from Ce and the selected elements. The composite oxide may also contain Al. The composite oxide may also contain transition metal elements excluding Group 3 elements.

[0029] [Crystalline state of oxide catalyst] The crystalline state of the oxide catalyst of the present invention is not particularly limited. The crystalline state of the oxide catalyst may be amorphous (non-crystalline) or crystalline. When crystalline, the crystallite size is not particularly limited, and may be, for example, 0.5 to 1000 nm. Furthermore, when the oxide catalyst contains a crystalline component, it preferably contains a crystalline component derived from aluminum oxide (Al2O3).When the oxide catalyst contains a crystalline component derived from Al2O3, Al2O3 (also called α-alumina) having a trigonal α-type crystalline phase is preferred. Whether or not an oxide catalyst contains a crystalline component and the type of the crystalline component can be determined by a conventional X-ray diffraction method.

[0030] [Oxide catalyst shape] The shape of the oxide catalyst of the present invention is not particularly limited. The oxide catalyst is usually in the form of particles, and the shape of the particles is not particularly limited. Examples of the shape of the oxide catalyst include a spherical shape, a polyhedral shape (e.g., an octahedral shape, a rhombic dodecahedral shape), a polygonal prism shape, and a flat plate shape. The oxide catalyst may also be an aggregate formed by aggregating particles of the above shapes. The oxide catalyst may also be shaped into a structure having interconnected pores through which gas can pass, such as a honeycomb shape or a sponge shape.

[0031] [Oxide catalyst size] When the oxide catalyst of the present invention is in the form of particles, there is no particular limitation on the size thereof. When the oxide catalyst is in the form of particles, the particle size is, for example, 0.5 nm to 500 μm. When the oxide catalyst is in the form of particles, the particle size can be measured by a known method depending on the size. When the oxide catalyst is an embodiment in which Ce or a selected element, or an oxide of Ce or a selected element, is supported on a support, the size of the supported particles is not particularly limited, but may be, for example, 0.2 to 1000 nm.

[0032] <Method of manufacturing oxide catalyst> The method for producing the oxide catalyst of the present invention is not particularly limited, and known methods can be used. Examples of methods for producing an oxide catalyst include a wet method and a dry method. Examples of wet methods include a method (precipitation method) in which a precursor solution containing the above-mentioned constituent elements is mixed with, for example, an alkali (e.g., sodium hydroxide, ammonia) to generate precursor particles, and then an oxide catalyst is obtained by oxidation treatment. An example of a wet method is an impregnation method, in which a support having a desired particle size is contacted with a precursor solution containing the above-mentioned elements to adsorb the precursor onto the support, followed by oxidation to obtain an oxide catalyst. The support may or may not contain the above-mentioned elements, but preferably contains the above-mentioned elements, more preferably Al, and even more preferably particles containing Al2O3. Furthermore, when the support is particles containing Al2O3, it is also preferable to use α-alumina particles. α-alumina particles may be commercially available or may be synthesized. Examples of methods for synthesizing α-alumina include methods in which precursor aluminum hydroxide (Al(OH)3) particles, boehmite (AlOOH) particles, or low-temperature phase aluminum oxide particles (e.g., γ-, η-, and θ-type aluminum oxide) particles are calcined at high temperatures (e.g., 1000°C or higher, 1100°C or higher, and 1200°C or higher). The carrier used in the impregnation method may be in the form of particles or may be formed into a predetermined shape (for example, a honeycomb shape).

[0033] The precursor solution in the wet method may contain all of the above-mentioned contained elements, or may contain some of the above-mentioned contained elements. That is, in the precipitation method and the impregnation method, the oxide catalyst may be produced, for example, by a single treatment using a precursor solution containing all of the above-mentioned contained elements, or may be produced stepwise by performing the treatment for each element using a precursor solvent containing some of the above-mentioned contained elements.

[0034] The oxidation treatment is not particularly limited as long as the precursor particles or precursor are oxidized, and can be carried out by a known method. Examples of the oxidation treatment include a method of firing at a temperature of 100 to 1500°C in an oxygen-containing atmosphere, a method of oxidizing treatment using an oxidizing agent in a gas phase, and a method of treating with an oxidizing agent in a solution. The oxidation treatment may be carried out by combining the above methods. Furthermore, a drying treatment may be carried out as necessary before or after the oxidation treatment. The drying treatment may be carried out by a known method, such as natural drying, heat drying, reduced pressure drying, solvent substitution drying, supercritical drying, freeze drying, and spray drying. The drying treatment may also be carried out by combining the above methods.

[0035] Dry methods include a powder method, a CVD (chemical vapor deposition) method, and a PVD (physical vapor deposition) method. Among dry methods, a method in which a layer or particles containing the above-mentioned contained elements are formed on a support by a CVD method or a PVD method is preferred. The powder method may be a known method, such as a method in which a solid precursor containing the above-mentioned constituent elements is mixed and then calcined. The calcination treatment may be carried out simultaneously with the oxidation treatment. As the CVD method, a known method can be used, and examples thereof include a thermal CVD method, a plasma CVD method, and an atomic layer deposition (ALD) method. As the PVD method, a known method can be used, and examples thereof include a sputtering method, a vapor deposition method, and an ion plating method. In the dry method, the oxidation treatment and drying treatment mentioned in the wet method may be carried out.

[0036] As a method for producing an oxide catalyst, among the above methods, the wet method is preferred, and the impregnation method is more preferred, in terms of ease of production.

[0037] <Hydrocarbon manufacturing method> The gas production method of the present invention is a hydrocarbon production method that includes a step (reaction step) of carrying out oxidative coupling of methane (OCM) using the oxide catalyst of the present invention to produce hydrocarbons having two carbon atoms. The method for producing a gas of the present invention is not particularly limited as long as it includes the above reaction step. In addition to the above steps, the gas production method of the present invention may include a supply step of supplying a gas containing methane to a reaction section in which the oxide catalyst of the present invention is disposed, and a purification step of purifying hydrocarbons having a carbon number of 2 from the gas containing hydrocarbons having a carbon number of 2 obtained through the reaction step. Hereinafter, each step that may be included in the gas production method of the present invention will be described.

[0038] [Supply process] In the supply step, a gas containing methane is supplied to a reaction section in which an oxide catalyst is disposed. The methane-containing gas may contain components other than methane, and preferably contains an oxidizing agent, which is not particularly limited but is preferably oxygen. When the oxidizing agent is oxygen, the volume ratio of the methane content to the oxygen content is preferably 1.5 to 10.0, more preferably 1.8 to 8.0, and even more preferably 2.0 to 6.0. The total content of methane and oxidizing agent is preferably 50% by volume or more, more preferably 70% by volume or more, and even more preferably 80% by volume or more, based on the total amount of gas containing methane. The methane-containing gas may be preheated to a temperature equal to or lower than the reaction temperature in the reaction step described below.

[0039] [Reaction process] In the reaction step, OCM is carried out using the oxide catalyst of the present invention to produce hydrocarbons having two carbon atoms. The temperature in the reaction step is generally 1000° C. or lower, preferably 900° C. or lower, and may be 850° C. or lower. The lower limit is generally 600° C. or higher, preferably 700° C. or higher. The oxide catalyst of the present invention enables the production of hydrocarbons having two carbon atoms with good yield. When a gas containing oxygen is supplied as an oxidizing agent, ethane and ethylene are produced as hydrocarbons with two carbon atoms, and at the same time, carbon dioxide, carbon monoxide, hydrogen, water, etc. are produced. In the reaction step, it is preferable to contact the oxide catalyst with a gas containing methane that is supplied. The reaction between the oxide catalyst and the gas may be carried out in a fixed bed system or a fluidized bed system, with the fixed bed system being preferred. In the case of a fixed bed system, the ratio of the amount of gas supplied to the volume of the reaction section where the oxide catalyst is placed, i.e., the gas hourly space velocity (h -1 ) may be set appropriately. In addition, the ratio of the amount of gas supplied to the cross-sectional area of ​​the reaction section where the oxide catalyst is placed, that is, the linear velocity (m / s), may also be set appropriately.

[0040] [Refining process] In the purification step, hydrocarbons having a carbon number of 2 are purified from the gas containing hydrocarbons having a carbon number of 2 obtained through the reaction step. Examples of hydrocarbons having a carbon number of 2 include ethane and ethylene. The purification method is not particularly limited, and known methods can be used. Purification methods include, for example, cryogenic separation, adsorption, and absorption, with cryogenic separation being preferred. [Example]

[0041] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the following examples.

[0042] <Preparation of oxide catalyst> The oxide catalysts of the examples and the comparative examples were prepared according to the following procedure. The oxide catalyst was obtained by impregnation. Specifically, precursor particles containing the target element were attached to Al2O3 particles to obtain precursor particles, which were then calcined to obtain the oxide catalyst.

[0043] The preparation procedure for the oxide catalyst of Example 1 will be described in more detail. First, Al2O3 (Kanto Chemical Co., Inc., aluminum oxide (α-type)) particles were prepared as a support. Furthermore, a Ce-containing precursor aqueous solution (3.4 mmol, 51 mL) and a K-containing precursor aqueous solution (3.4 mmol, 51 mL) were prepared. Next, 1.0 g of Al2O3 was placed in a flask, followed by 3 mL of the Ce precursor solution, 3 mL of the K precursor solution, and then 90.65 mg of the Tb reagent solution. After the precursor solutions and reagents were added to the flask, the contents of the flask were stirred at 50°C for 6 hours. After the stirring treatment, the mixture was dried under reduced pressure at 80°C in a centrifugal evaporator (CVE-3110, manufactured by Tokyo Rika Kikai Co., Ltd.) to obtain precursor particles, which were further dried overnight at 110°C in a dryer (ETTAS ON-300S, manufactured by AS ONE Corporation). The dried precursor particles were crushed and calcined in a muffle furnace (KDF 3000plus, Denken Hydental) at 900°C for 3 hours in an air atmosphere to obtain an oxide catalyst. The Ce-containing precursor aqueous solution and the K-containing precursor aqueous solution each contained 0.2 mmol (millimol) of Ce, K, and Tb as metal elements. In other words, 0.2 mmol each of Ce, K, and Tb was supported as oxides on Al2O3 using the above procedure.

[0044] The oxide catalysts of the other examples and comparative examples were obtained in the same manner as the oxide catalyst of Example 1 above, except that the metal species contained in the support and the precursor solution used were changed as shown in Table 1 below. In Table 1, M1, M2, and M3 indicate that the precursor aqueous solutions containing M1, M2, and M3 were added to the flask in this order.

[0045] The precursors contained in each precursor aqueous solution were as follows: Li: LiNO3, Fujifilm Wako Pure Chemical Na:NaNO3, Kanto Chemical ·K: KNO3, Fujifilm Wako Pure Chemical Cs: CsNO3, Sigma ·Ca: Ca(NO3)2·4H2O, Fujifilm Wako Pure Chemical Sr: Sr(NO3)2, Alfa Aeser Ba: Ba(CH3COO)2, Fujifilm Wako Pure Chemical ·Y:Y(NO3)2·6H2O, Sigma-Aldrich ·La: La(NO3)3·6H2O, Fujifilm Wako Pure Chemical ·Ce: Ce(NO3)3·6H2O, Fujifilm Wako Pure Chemical ·Pr:Pr(NO3)3·6H2O, Sigma-Aldrich ·Nd:Nd(NO3)3·6H2O, Sigma-Aldrich ·Sm:Sm(NO3)3·6H2O, Sigma-Aldrich ·Gd: Gd(NO3)3·6H2O, Fujifilm Wako Pure Chemical ·Tb: Tb(NO3)3·6H2O, Kanto Chemical ·Ho:Ho(NO3)3·nH2O, Fujifilm Wako Pure Chemical ·Tm: Tm(NO3)3·5H2O, Aldrich ·Mn:Mn(NO3)2·6H2O, Fujifilm Wako Pure Chemical ·Zr: ZrO(NO3)2·2H2O, Fujifilm Wako Pure Chemical ·W: 5(NH4)2O·12(WO3·5H2O, Kanto Chemical

[0046] <Evaluation> The OCM reaction characteristics of each oxide catalyst of the Examples and Comparative Examples were evaluated by the following procedure. The OCM reaction characteristics of the oxide catalyst were measured by placing the oxide catalyst in a reaction tube, supplying a gas containing methane to the oxide catalyst at an adjusted temperature, and analyzing the components of the emitted gas. More specifically, a reaction tube connected to a quartz tube with an inner diameter of 4 mm (gas inlet side) and an inner diameter of 2 mm (gas outlet side) was placed with the gas inlet side facing up, and glass wool was placed on the connection from the gas inlet side, 50 mg of oxide catalyst was placed on the glass wool, and further glass wool was placed on top. The length of the 4 mm inner diameter part of the reaction tube was 160 mm, and the length of the 2 mm inner diameter part was 130 mm. The reaction tube equipped with the oxide catalyst was fixed to a ring furnace (ARF1-200-60KC, manufactured by Asahi Rika Seisakusho, heating section 170 mm) with the gas inlet side facing upward, and pretreatment was carried out for 30 minutes at a catalyst temperature of 500°C while supplying oxygen from the gas inlet side at 30 mL / min. The catalyst temperature was monitored with an R thermocouple installed near the connection part of the reaction tube and controlled with a control unit (model SU, manufactured by Chino Corporation).

[0047] After pretreatment, nitrogen gas was supplied at 30 mL / min to purge the reactor, and then a mixture of methane, oxygen, and nitrogen was supplied to the reactor at 31 mL / min. The mixture was mixed before being supplied to the reactor, with methane at a flow rate of 21 mL / min, oxygen at 7 mL / min, and nitrogen at 3 mL / min (CH4 / O2 = 3.0). A condensation-type water trap and a gas chromatograph (Micro GC FUSION, INFICON) were connected to the gas outlet side of the reactor. While the mixed gas was continuously supplied to the reaction tube, the catalyst temperature was maintained at 500°C for 40 minutes, and gas component analysis was performed using a gas chromatograph installed on the gas outlet side of the reaction tube. From the gas component analysis results obtained, the yield of hydrocarbons with a carbon number of 2 (C2 yield) at 500°C was obtained. For the gas analysis, an Rt-Msieve 5A column (0.25 mm x 10 m, carrier gas: argon, manufactured by Restek) and an Rt-U-BOND column (0.25 mm x 8 m, carrier gas: helium, manufactured by Restek) were used. After the measurement at 500°C, the catalyst temperature was increased to 550°C in 5 minutes, and the temperature was maintained and the gas composition analysis was repeated in the same manner to obtain the C2 yield. The temperature increase and gas composition analysis were repeated in 50°C increments up to 850°C.

[0048] <Result> Table 1 shows the evaluation results of the C2 yield of the oxide catalysts of each Example and each Comparative Example. In Table 1, the column "Metal content in support" indicates the ratio of the content of metal atoms in the support to the total content of all metal elements contained in the oxide catalyst. The column "M1 content" indicates the ratio of the content of M1 to the total content of all metal elements contained in the oxide catalyst. The column "M2 content" indicates the ratio of the content of M2 to the total content of all metal elements contained in the oxide catalyst. The column "M3 content" indicates the ratio of the content of M3 to the total content of all metal elements contained in the oxide catalyst. In Table 1, examples with "-" in the "M3" column indicate that no precursor solution or reagent was added as M3. The highest C2 yield is shown together with the measurement temperature in Table 1. The C2 yield is preferably 17.0% or more, more preferably 18.0% or more, and even more preferably 19.0% or more.

[0049] [Table 1]

[0050] Comparing the results in Table 1 between the Examples and Comparative Examples, it was confirmed that the oxide catalyst of the present invention, which contains at least aluminum (Al) and cerium (Ce) as contained elements and which contains at least one element selected from the group consisting of Group 1 elements other than hydrogen, Group 2 elements, and Group 3 elements other than Ce, exhibits a superior C2 yield compared to the oxide catalyst of the Comparative Example, which does not contain at least one of the contained elements. A comparison of Examples 1 to 13 with Examples 14 to 23 confirmed that a better C2 yield was achieved when the contained elements included one first element selected from the group consisting of K, Ca, and Sr in addition to Al and Ce, and one second element that is a lanthanoid element other than La, or La and a lanthanoid element other than La or Sr, or only one third element selected from the group consisting of K and Ca, or one third element selected from the group consisting of K and Ca, and one fourth element selected from the Group 1 elements other than K.

Claims

1. An oxide catalyst, The contained elements include at least aluminum and cerium, The oxide catalyst contains, as the contained element, at least one selected element selected from the group consisting of Group 1 elements other than hydrogen, Group 2 elements, and Group 3 elements other than cerium.

2. 2. The oxide catalyst according to claim 1, wherein the selective element comprises at least one element selected from the group consisting of alkali metal elements, alkaline earth metal elements, and lanthanoid elements.

3. 3. The oxide catalyst according to claim 1, wherein the optional element comprises at least one element selected from the group consisting of alkali metal elements, alkaline earth metal elements, and lanthanum.

4. 3. The oxide catalyst according to claim 1, wherein the selected element comprises at least one element selected from the group consisting of potassium, calcium, strontium, and lanthanum.

5. In addition to aluminum and cerium, the contained elements include: a first element selected from the group consisting of potassium, calcium, and strontium, and a second element that is a lanthanoid element other than lanthanum; containing lanthanum and a lanthanoid element other than lanthanum or strontium, containing only one tertiary element selected from the group consisting of potassium and calcium, or 3. The oxide catalyst according to claim 1, comprising one third element selected from the group consisting of potassium and calcium, and one fourth element selected from the Group 1 elements other than potassium.

6. A method for producing hydrocarbons, comprising a step of carrying out oxidative coupling of methane using the oxide catalyst according to claim 1 or 2 to produce hydrocarbons having two carbon atoms.

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