CN108067265B - Preparation method of methane conversion catalyst - Google Patents
Preparation method of methane conversion catalyst Download PDFInfo
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- CN108067265B CN108067265B CN201610991016.2A CN201610991016A CN108067265B CN 108067265 B CN108067265 B CN 108067265B CN 201610991016 A CN201610991016 A CN 201610991016A CN 108067265 B CN108067265 B CN 108067265B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
- B01J27/053—Sulfates
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/06—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of zinc, cadmium or mercury
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/093—Preparation of halogenated hydrocarbons by replacement by halogens
- C07C17/15—Preparation of halogenated hydrocarbons by replacement by halogens with oxygen as auxiliary reagent, e.g. oxychlorination
- C07C17/152—Preparation of halogenated hydrocarbons by replacement by halogens with oxygen as auxiliary reagent, e.g. oxychlorination of hydrocarbons
- C07C17/154—Preparation of halogenated hydrocarbons by replacement by halogens with oxygen as auxiliary reagent, e.g. oxychlorination of hydrocarbons of saturated hydrocarbons
Abstract
The invention discloses a preparation method of a methane conversion catalyst, which comprises the following steps: mixing zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid and 2-methylimidazole, then spraying aluminum oxide loaded with zinc by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid and 2-methylimidazole, drying and roasting to obtain the methane-oxyhalogenation conversion catalyst. The catalyst prepared by the method can simultaneously improve the conversion rate of methane and the selectivity of a target product, namely the halogenated methane, inhibit the deep oxidation of the halogenated methane, and further obviously improve the yield of the halogenated methane.
Description
Technical Field
The invention relates to a preparation method of a methane conversion catalyst, in particular to a preparation method of a low-temperature high-activity selective methane oxyhalogenation conversion catalyst with a shell-core structure.
Background
The process of reacting methane with a halogen, not directly but with HCl, HBr or a metal halide as the halogen source, in the presence of oxygen to produce methyl halide is known as oxyhalogenation. The method is firstly applied to the industrial production of preparing chlorine by HCl catalytic oxidation, and is called a Deacon process.
The early methane halooxidation reactions primarily used HCl as the halogen source, while the catalysts primarily used CuCl2As an active ingredient, Bromhead et al (Bromhead J, Font-free J J, Westlake D J. Process for the production of methyl or ethyl mono-chloride or bromide. EP. Patent, 0117731.1984-09-05) supporting CuCl on alumina2To prepare the oxychlorination catalyst. Conner et al (Conner W C Jr, Pieters W J M, Gates W, et al, The oxidative catalysis of methane on fundamental-based Cu, K, La catalysis: II. Gas phase catalysis. Appl Cat, 1984, 11(1): 49-58; Conner W C Jr, Pieters W J M, Signorelli A J. The oxidative catalysis of methane on fundamental-based Cu, K, La catalysis: III. Bulk&surface analysis, appl. Catal., 1984, 11(1): 59-71) in CuCl2On the basis of catalyst the alkali metal chloride KCl or rare earth metal chloride LaCl with high melting point can be added3As an auxiliary agent, it is used for stabilizing the activity of the catalyst, thereby reducing the content of CuCl2The catalyst loss caused by low boiling point can obtain higher methane conversion rate, the catalytic effect is relatively stable, but the polychlorinated methane selectivity is also increased.
US 6452058 discloses as CuCl2Rare earth metal chloride LaCl of main auxiliary agent3The catalyst has good catalytic activity for oxychlorination, synthesizes porous LaOCl, has good catalytic performance, and has the methane conversion rate of 12 percent and the selectivity of methane chloride of 55 percent at the reaction temperature of 400 ℃.
Further studies were made on La-based catalysts, Lercher et al (Podkolzin S G, Stangland E, Lercher J A, et al, Methyl Chloride Production from Methyl over Lanthanum-based catalysts J. Am. chem. Soc., 2007, 129(9): 2569-2576), synthesized catalysts LaOCl/LaCl3Gas composition V at 540 DEG C（CH4）:V（HCl）:V（O2）:V（N2）Under the condition of 2:1:1:0.5, the methane conversion rate is 13.3%, the methane chloride selectivity is 62.6%, and the catalyst has good stability. Lercher further studied the reaction mechanism, La is a metal that enables methane to undergo oxychlorination without changing its valence state, he believes that the reaction takes place on the surface of the catalyst in an oxidation-reduction reaction, O2The Cl on the surface of the activated catalyst forms OCl, the OCl is changed into Cl after activating the methane, and the Cl and the OCl are mutually converted, so that the oxychlorination reaction is carried out.
Wang Ye et al (Transformation of methane to propylene: a two step reacted reagent modified CeO2 nanocrystals and zeolites [ J]Angewendte Chemie International Edition, 2012, 51: 2438-; chlorine oxidation reaction of methane on catalyst of palladium oxide and manganese oxide loaded on cerium dioxide nano-rod [ D ]]University of mansion, 2013.) used a catalyst containing a rare earth element Ce as a main component, which has outstanding activity on oxychlorination. The active component of the catalyst is CeO2And the cerium-based bi-component composite oxide which can be prepared by modifying the second component is loaded on different carriers (SiO)2、Al2O3、MgO、ZrO2、TiO2Etc.). At a temperature of 480 ℃ and CH4：HCl：O2：N2: he = 4:2:1:1.5:1.5, space velocity 40mL/min, CH3Cl selectivity and yield reached 66% and 8%, which is better than the LaOCl 55% selectivity of Lercher, and 6.6% yield. The two-component catalyst has the best effect of mixing with iron, and 15 percent wtFeOx-CeO2Nanorod, reaction for 100 h CH4Conversion 23%, CH3Cl selectivity was 74%. Ce in cerium-based catalyst3 +And Ce4+The cyclic conversion of valence states plays an important role in activating HCl in oxychlorination reaction, and HCl passes through O2Activated Cl generated by activation, reaction of the activated Cl and methane to generate methane chloride, and reduced Ce3+And is also O2By oxidation to Ce4+The catalytic cycle is completed. It was also found that the morphology of the catalyst, i.e. the exposed crystal planes, had a significant effect on the activity of the catalyst, the highest being the {100} plane, the next highest being the {110} plane, and the lowest being the {111} plane (epoxidation of propylene with oxygen as oxidant on copper-based catalysts and oxychlorination of methane on cerium-based catalysts [ D)]Building university, 2012).
CN201310216352.6 discloses a catalyst for preparing methyl bromide and CO by methane bromine oxidation, which comprises a main active component and a carrier, wherein the main active component is selected from FePO4、Fe2P2O7And Fe3(P2O7)2One or more of the carriers are TiC-SiC and TiO2The catalyst is prepared by adopting an impregnation method to load impregnation liquid containing the main active component on a carrier, drying and roasting, and can catalyze the mixture of methane, oxygen and HBr aqueous solution to be converted into methyl bromide and CO at high activity and high selectivity under the reaction conditions of normal pressure and 400-800 ℃. The catalyst has good performance, and has no obvious inactivation and no carbon deposition on the catalyst in the continuous reaction process of more than 1400 hours.
CN201110198638.7 discloses a method for preparing chloromethane by oxychlorination of methane and a method for preparing methyl bromide by bromooxidation of methane. The cerium-based catalyst is suitable for methane oxyhalogenation, and can be CeO2And a cerium-based two-component composite oxide or a supported cerium-based oxide catalyst. The cerium-based catalyst can efficiently and stably catalyze methane oxyhalogen reactions, including oxychlorination and bromooxidation reactions, to generate methyl chloride and methyl bromide. The cerium-based catalyst can efficiently catalyze and convert the reactant CH4，HCl，O2Chlorine oxidation reaction is carried out to generate a product CH3Cl and CH2Cl2(ii) a The cerium-based catalyst can also efficiently convert CH4，HBr(H2O)，O2Carrying out bromine oxidation reaction to generate CH3Br，CH2Br2。
The methane oxyhalogenation reaction in the prior art has the technical problem that the high temperature is favorable for improving the conversion rate of methane, but the generated halogenated methane, particularly monohalogenated methane, can be deeply oxidized to generate CO or CO2The selectivity of the halogenated methane is obviously reduced, so that the yield of the halogenated methane is low, and therefore, the development of the methane oxyhalogenation reaction catalyst with higher methane conversion rate and halogenated methane selectivity has important significance.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation method of a methane halogenation oxidation conversion catalyst with a shell-core structure. The catalyst prepared by the method can simultaneously improve the conversion rate of methane and the selectivity of a target product, namely the halogenated methane, inhibit the deep oxidation of the halogenated methane, and further obviously improve the yield of the halogenated methane.
A method of preparing a methane conversion catalyst comprising: mixing zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid and 2-methylimidazole, then spraying aluminum oxide loaded with zinc by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid and 2-methylimidazole, drying and roasting to obtain the methane-oxyhalogenation conversion catalyst.
In the above method, the zirconium sulfate solid acid may be commercially available or prepared according to the prior art. The aluminum hydroxide slurry is generally pseudo-boehmite slurry. The pseudoboehmite is also called alumina monohydrate or pseudoboehmite, and the molecular formula is AlOOH & nH2O (n = 0.08-0.62). The method for producing the aluminum hydroxide slurry is not particularly limited, and various methods commonly used in the art may be used, and examples thereof include aluminum alkoxide hydrolysis, acid or alkali methods of aluminum salt or aluminate, and NaA1O2Introducing CO into the solution2The carbonization method of (3). The specific operation method is well known to those skilled in the art and will not be described herein.
In the above method, the zinc-supporting alumina can be prepared by a conventional technique including any method of supporting zinc on alumina. The zinc-containing compound is impregnated and loaded on the formed alumina or the zinc-containing compound and the alumina powder are kneaded and formed, and then the zinc-loaded alumina is prepared by drying and roasting. The aluminum oxide can be prepared by adopting a commercial product or according to the prior art, and the zinc-containing compound can be one or more of zinc nitrate, zinc sulfate, zinc bromide and zinc chloride. The drying time is 1-5h, preferably 2-4h, the drying temperature is 90-150 ℃, preferably 100-130 ℃; the roasting time is 3-8h, preferably 4-6h, and the temperature is 300-700 ℃, preferably 400-500 ℃.
In the above process, the 2-methylimidazole content in the aluminum hydroxide slurry containing zirconium sulfate solid acid and 2-methylimidazole is 1 to 10% by weight, preferably 3 to 7% by weight. Before the aluminum oxide loaded with zinc is subjected to spray leaching by using the weight content of 2-methylimidazole in the aluminum hydroxide slurry containing zirconium sulfate solid acid and 2-methylimidazole, the aluminum oxide loaded with zinc is preferably treated by using a water vapor nitrogen mixed gas with the water vapor volume content of 1-15%, preferably 1-5%, at the treatment temperature of 150-300 ℃, preferably 180-200 ℃ and for the treatment time of 5-30min, preferably 5-15 min, and further preferably 5-10 min. Research results show that the hydroxyl content of the surface of the aluminum oxide loaded with zinc can be improved by adopting the treatment mode on the aluminum oxide, meanwhile, the internal hydroxyl content is not improved, so that aluminum hydroxide slurry containing zirconium sulfate solid acid can be uniformly sprayed and soaked around the aluminum oxide loaded with zinc, meanwhile, the hydroxide bond of the aluminum hydroxide can be bonded with the hydroxyl rich in the surface of the aluminum oxide loaded with zinc, and the aluminum hydroxide is a pore channel which is communicated and fused, so that the activity of the catalyst and the selectivity of a target product are improved.
The catalyst has a shell-core structure, wherein the core of the catalyst is alumina loaded with zinc, and the shell of the catalyst is alumina containing solid zirconium sulfate acid, wherein the weight ratio of the alumina loaded with zinc to the alumina containing solid zirconium sulfate acid is 10:1-2:1, preferably 8:1-5: 1; the zirconium sulfate solid acid is present in an amount of 5 to 10 wt.%, preferably 8 to 15 wt.%, based on the weight of the alumina containing the zirconium sulfate solid acid, and zinc is present in an amount of 5 to 30 wt.%, preferably 10 to 25 wt.%, calculated as oxide, based on the weight of the alumina supporting zinc.
In the above catalyst, the thickness of the shell is 5 μm to 200. mu.m, preferably 10 μm to 150. mu.m, and more preferably 15 μm to 100. mu.m.
In the catalyst, the zinc-loaded alumina can be spherical or strip-shaped, and is preferably spherical; the zinc-loaded alumina has an equivalent diameter of 1mm to 5mm, preferably 2mm to 5mm, and most preferably 2mm to 3 mm.
The application of the catalyst in methane oxyhalogenation conversion adopts a fixed bed process, methane, oxygen and halogen acid are used as reactants or methane, oxygen and halogen acid aqueous solution are used as reactants to carry out methane oxyhalogenation conversion under the action of the catalyst, the reaction temperature is 250-600 ℃, preferably 300-450 ℃, the feeding volume ratio of the methane, the halogen acid and the oxygen is (3-5): 1 (1-3):1, and the flow rate of the methane is 10-50ml/min, preferably 20-40 ml/min. The halogenated acid is hydrogen chloride or hydrogen bromide or an aqueous solution thereof, preferably an aqueous hydrogen bromide solution.
Research results show that the methane oxyhalogenation conversion reaction involves a plurality of reactions such as methane steam reforming reaction, methane oxidation reaction and deep oxidation of halogenated methane, so that the selectivity of the halogenated methane cannot be effectively improved. The catalyst with the core-shell structure, which is prepared by the invention, can realize relative control of the reactions by using the difference of the sensitivity of different components of the core-shell structure to different reactions. In particular, the zinc-loaded alumina in the core of the catalyst is more favorable for carrying out the reaction of converting halogen acid into halogen free radicals to generate a small amount of methane halogenation reaction, particularly reducing the acid content of the alumina and improving the content of the halogen acid on the core, the alumina with the shell containing zirconium sulfate solid acid mainly carries out the methane halogenation reaction, the halogen free radicals generated in the core can be quickly diffused into the shell to carry out the methane halogenation reaction, and the halogen free radicals generated in the core can be quickly diffused to the outside of the catalyst after generating the halogenated hydrocarbons, so that the further oxidation of the catalyst is prevented, and the selectivity of the halogenated hydrocarbons and the conversion rate of methane are obviously improved.
The 2-methylimidazole template agent is added in the preparation process of the methane conversion catalyst prepared by the method, and a specific pore channel is formed in the shell of the catalyst, so that the reaction of methane and bromine free radicals in the shell is facilitated.
Detailed Description
The following examples are provided to further illustrate the methane oxyhalogenation conversion catalyst and the preparation method, application and effect thereof, but the following examples are not intended to limit the present invention. The catalyst of the invention can adopt means such as transmission electron microscope observation, electron diffraction analysis, element composition analysis and the like to confirm the core-shell structure and determine the composition of the core and the shell. The determination of the core-shell structure of the catalyst specifically adopts the following method: the sample was sufficiently ground in an agate mortar using a high-resolution transmission electron microscope (JEM 2100 LaB6, JEOL Ltd., Japan) with a resolution of 0.23 nm equipped with an X-ray energy dispersive spectrometer (EDX) from EDAX, and then ultrasonically dispersed in absolute ethanol for 20 min. And (3) dripping 2-3 drops of the suspension liquid on a micro-grid carbon film supported by a copper net, and carrying out TEM observation, electron diffraction analysis and element composition analysis on the sample after the sample is dried.
Example 1
Preparing aluminum hydroxide slurry by adopting an aluminum isopropoxide hydrolysis method: mixing water and aluminum isopropoxide according to a molar ratio of 120:1, controlling the hydrolysis temperature at 80-85 ℃, hydrolyzing the aluminum isopropoxide for 1.5h, and then aging at 90-95 ℃ for 18h to obtain aluminum hydroxide slurry with the solid content of 21.3 wt%.
Preparation of zinc-loaded alumina: an isovolumetric impregnation method is adopted to prepare alumina (a commercial product, the property is as follows: the L acid content is 0.2 mmol.g)-1(ii) a A BET specific surface area of 200; pore volume of 0.3 ml/g), drying and roasting after soaking, wherein the drying time is 2 hours and the drying temperature is 130 ℃; the roasting time is 4 hours, the temperature is 400 ℃, the zinc-loaded alumina is spherical, and the equivalent diameter of the zinc-loaded alumina is 2 mm;
spray soaking process: mixing a proper amount of zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, wherein the mass content of 2-methylimidazole in the slurry is 3%, then spraying and soaking zinc-loaded alumina with the slurry, drying and roasting to obtain a methane-oxyhalogenation conversion catalyst, wherein the drying time is 4 hours, and the drying temperature is 100 ℃; the roasting time is 6h, and the temperature is 400 ℃.
The catalyst properties were as follows: the catalyst has a core-shell structure, wherein the core is aluminum oxide loaded with zinc, and the shell is aluminum oxide containing solid zirconium sulfate acid, wherein the weight ratio of the aluminum oxide loaded with zinc to the aluminum oxide containing solid zirconium sulfate acid is 8: 1; the zirconium sulfate solid acid content was 8% by weight, based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc content was 25% by weight, calculated as oxide, based on the weight of the alumina supporting zinc; the thickness of the shell is 15 μm.
The above catalyst was evaluated for the oxyhalogenation of methane under the following conditions: the methane oxybromination reaction is carried out in a fixed bed microreactor at normal pressure. 10ml of 20-40 mesh catalyst is loaded into a quartz reaction tube, a catalyst bed layer is positioned in the middle of a heating furnace, and quartz sand is filled above and below the catalyst bed layer. The reaction gas flow rate was adjusted by a mass flow meter, and the hydrobromic acid flow rate was controlled by a peristaltic pump. And (2) under the protection of nitrogen, raising the temperature to 350 ℃, and after the temperature is constant, mixing methane, halogen acid, oxygen and nitrogen according to a volume ratio of 4:2:1:1 was passed into the reactor at a flow rate of methane of 30 ml/min. After reacting for 2h, the tail gas is washed by water, dried and analyzed on line by north SP-3420A type gas chromatography. The evaluation results are shown in Table 1
Example 2
Preparing aluminum hydroxide slurry by adopting an aluminum isopropoxide hydrolysis method: mixing water and aluminum isopropoxide according to a molar ratio of 120:1, controlling the hydrolysis temperature at 80-85 ℃, hydrolyzing the aluminum isopropoxide for 1.5h, and then aging at 90-95 ℃ for 18h to obtain aluminum hydroxide slurry with the solid content of 21.3 wt%.
Preparation of zinc-loaded alumina: an isovolumetric impregnation method is adopted to prepare alumina (a commercial product, the L acid content is 0.1 mmol.g)-1(ii) a BET specific surface area of 300m2(ii)/g; pore volume of 0.5 ml/g), drying and roasting after soaking, wherein the drying time is 3 hours and the drying temperature is 120 ℃; the roasting time is 5 hours, the temperature is 450 ℃, the zinc-loaded alumina is spherical, and the equivalent diameter of the zinc-loaded alumina is 2 mm;
spray soaking process: mixing a proper amount of zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, wherein the mass content of 2-methylimidazole in the slurry is 7%, then spraying and soaking zinc-loaded alumina with the slurry, drying and roasting to obtain a methane-oxyhalogenation conversion catalyst, wherein the drying time is 3 hours, and the drying temperature is 100 ℃; the roasting time is 4 hours, and the temperature is 450 ℃.
The catalyst properties were as follows: the catalyst has a core-shell structure, wherein the core is aluminum oxide loaded with zinc, and the shell is aluminum oxide containing solid zirconium sulfate acid, wherein the weight ratio of the aluminum oxide loaded with zinc to the aluminum oxide containing solid zirconium sulfate acid is 7: 1; the zirconium sulfate solid acid content was 11% by weight, based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc content was 15% by weight, calculated as oxide, based on the weight of the alumina supporting zinc; the thickness of the shell was 30 μm.
The above catalyst was evaluated for the oxyhalogenation of methane under the same conditions as in example 1, and the evaluation results are shown in Table 1.
Example 3
Preparing aluminum hydroxide slurry by adopting an aluminum isopropoxide hydrolysis method: mixing water and aluminum isopropoxide according to a molar ratio of 120:1, controlling the hydrolysis temperature at 80-85 ℃, hydrolyzing the aluminum isopropoxide for 1.5h, and then aging at 90-95 ℃ for 18h to obtain aluminum hydroxide slurry with the solid content of 21.3 wt%.
Preparation of zinc-loaded alumina: an isovolumetric impregnation method is adopted to prepare alumina (a commercial product, the property is as follows: the L acid content is 0.05 mmol.g)-1(ii) a BET specific surface area of 250m2(ii)/g; pore volume of 0.3-0.6 ml/g, preferably 0.4 ml/g) soaking in zinc bromide solution, drying and roasting after soaking, wherein the drying time is 4 hours, and the drying temperature is 100 ℃; the roasting time is 4 hours, the temperature is 500 ℃, the zinc-loaded alumina is spherical, and the equivalent diameter of the zinc-loaded alumina is 3 mm;
spray soaking process: mixing a proper amount of zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, wherein the mass content of 2-methylimidazole in the slurry is 5%, then spraying and soaking zinc-loaded alumina with the slurry, drying and roasting to obtain a methane-oxyhalogenation conversion catalyst, wherein the drying time is 3 hours, and the drying temperature is 100 ℃; the roasting time is 4 hours, and the temperature is 450 ℃.
The catalyst properties were as follows: the catalyst has a core-shell structure, wherein the core is aluminum oxide loaded with zinc, and the shell is aluminum oxide containing solid zirconium sulfate acid, wherein the weight ratio of the aluminum oxide loaded with zinc to the aluminum oxide containing solid zirconium sulfate acid is 5: 1; the zirconium sulfate solid acid content was 15% by weight, based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc content was 10% by weight, calculated as oxide, based on the weight of the alumina supporting zinc; the thickness of the shell was 60 μm.
The above catalyst was evaluated for the oxyhalogenation of methane under the same conditions as in example 1, and the evaluation results are shown in Table 1.
Example 4
Preparing aluminum hydroxide slurry by adopting an aluminum isopropoxide hydrolysis method: mixing water and aluminum isopropoxide according to a molar ratio of 120:1, controlling the hydrolysis temperature at 80-85 ℃, hydrolyzing the aluminum isopropoxide for 1.5h, and then aging at 90-95 ℃ for 18h to obtain aluminum hydroxide slurry with the solid content of 21.3 wt%.
Preparation of zinc-loaded alumina: the method is carried out by soaking in alumina (commercially available product with the following properties: L acid content of 0.1 mmol.g)-1(ii) a BET specific surface area of 280300m2(ii)/g; pore volume of 0.5 ml/g) is soaked in zinc sulfate solution, and drying and roasting are carried out after soaking, wherein the drying time is 3h, and the drying temperature is 120 ℃; the roasting time is 5 hours, the temperature is 450 ℃, the zinc-loaded alumina is spherical, and the equivalent diameter of the zinc-loaded alumina is 2 mm; carrying out hydrothermal treatment on the zinc-loaded alumina by adopting water vapor nitrogen mixed gas with the volume content of 1%, wherein the treatment temperature is 200 ℃, and the treatment time is 10 min.
Spray soaking process: mixing a proper amount of zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, wherein the mass content of 2-methylimidazole in the slurry is 2%, then spraying and soaking zinc-loaded alumina with the slurry, drying and roasting to obtain a methane-oxyhalogenation conversion catalyst, wherein the drying time is 3 hours, and the drying temperature is 100 ℃; the roasting time is 4 hours, and the temperature is 450 ℃.
The catalyst properties were as follows: the catalyst has a core-shell structure, wherein the core is aluminum oxide loaded with zinc, and the shell is aluminum oxide containing solid zirconium sulfate acid, wherein the weight ratio of the aluminum oxide loaded with zinc to the aluminum oxide containing solid zirconium sulfate acid is 7: 1; the zirconium sulfate solid acid content was 11% by weight, based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc content was 15% by weight, calculated as oxide, based on the weight of the alumina supporting zinc; the thickness of the shell was 30 μm.
The above catalyst was evaluated for the oxyhalogenation of methane under the same conditions as in example 1, and the evaluation results are shown in Table 1.
Example 5
Preparing aluminum hydroxide slurry by adopting a carbonization method of introducing carbon dioxide gas into sodium metaaluminate solution: will contain 30wt% CO2CO of2/N2Introducing the mixed gas into a sodium metaaluminate solution, carrying out gelling reaction at 30 ℃, controlling the pH of the reaction end point to be 10.5-11.0, aging after the reaction is finished, and washing the mixture by deionized water at 60 ℃ until the pH of the filtrate is 6.5 to obtain aluminum hydroxide slurry with the solid content of 31.2 wt%;
preparation of zinc-loaded alumina: the method is carried out by soaking in alumina (commercially available product with the following properties: L acid content of 0.1 mmol.g)-1(ii) a BET specific surface area of 300m2(ii)/g; pore volume of 0.5 ml/g), drying and roasting after soaking, wherein the drying time is 2 hours and the drying temperature is 130 ℃; the roasting time is 4 hours, the temperature is 400 ℃, the zinc-loaded alumina is spherical, and the equivalent diameter of the zinc-loaded alumina is 2 mm;
spray soaking process: mixing a proper amount of zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, wherein the mass content of 2-methylimidazole in the slurry is 8%, then spraying and soaking zinc-loaded alumina with the slurry, drying and roasting to obtain a methane-oxyhalogenation conversion catalyst, wherein the drying time is 4 hours, and the drying temperature is 100 ℃; the roasting time is 6h, and the temperature is 400 ℃.
The catalyst properties were as follows: the catalyst has a core-shell structure, wherein the core is aluminum oxide loaded with zinc, and the shell is aluminum oxide containing solid zirconium sulfate acid, wherein the weight ratio of the aluminum oxide loaded with zinc to the aluminum oxide containing solid zirconium sulfate acid is 8: 1; the zirconium sulfate solid acid content was 8% by weight, based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc content was 25% by weight, calculated as oxide, based on the weight of the alumina supporting zinc; the thickness of the shell is 15 μm.
The above catalyst was evaluated for the oxyhalogenation of methane under the same conditions as in example 1, and the evaluation results are shown in Table 1.
Example 6
Carbon with carbon dioxide gas introduced into sodium metaaluminate solutionPreparing aluminum hydroxide slurry by a chemical method: will contain 30wt% CO2CO of2/N2Introducing the mixed gas into a sodium metaaluminate solution, carrying out gelling reaction at 30 ℃, controlling the pH of the reaction end point to be 10.5-11.0, aging after the reaction is finished, and washing the mixture by deionized water at 60 ℃ until the pH of the filtrate is 6.5 to obtain aluminum hydroxide slurry with the solid content of 31.2 wt%;
preparation of zinc-loaded alumina: the method is carried out by soaking in alumina (commercially available product with the following properties: L acid content of 0.1 mmol.g)-1(ii) a BET specific surface area of 300m2(ii)/g; pore volume of 0.5 ml/g), drying and roasting after soaking, wherein the drying time is 3 hours and the drying temperature is 120 ℃; the roasting time is 5 hours, the temperature is 450 ℃, the zinc-loaded alumina is spherical, and the equivalent diameter of the zinc-loaded alumina is 2 mm;
spray soaking process: mixing a proper amount of zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, wherein the mass content of 2-methylimidazole in the slurry is 5%, then spraying and soaking zinc-loaded alumina with the slurry, drying and roasting to obtain a methane-oxyhalogenation conversion catalyst, wherein the drying time is 3 hours, and the drying temperature is 100 ℃; the roasting time is 4 hours, and the temperature is 450 ℃.
The catalyst properties were as follows: the catalyst has a core-shell structure, wherein the core is aluminum oxide loaded with zinc, and the shell is aluminum oxide containing solid zirconium sulfate acid, wherein the weight ratio of the aluminum oxide loaded with zinc to the aluminum oxide containing solid zirconium sulfate acid is 7: 1; the zirconium sulfate solid acid content was 11% by weight, based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc content was 15% by weight, calculated as oxide, based on the weight of the alumina supporting zinc; the thickness of the shell was 30 μm.
The above catalyst was evaluated for the oxyhalogenation of methane under the same conditions as in example 1, and the evaluation results are shown in Table 1.
Example 7
Preparing aluminum hydroxide slurry by adopting a carbonization method of introducing carbon dioxide gas into sodium metaaluminate solution: will contain 30wt% CO2CO of2/N2Mixed gas is introduced into the metaaluminiumCarrying out gelling reaction in a sodium acid solution at 30 ℃, controlling the pH at the end point of the reaction to be 10.5-11.0, aging after the reaction is finished, and washing the solution by deionized water at 60 ℃ until the pH of the filtrate is 6.5 to obtain aluminum hydroxide slurry with the solid content of 31.2 wt%;
preparation of zinc-loaded alumina: the method is carried out by soaking in alumina (commercially available product with the following properties: L acid content of 0.1 mmol.g)-1(ii) a BET specific surface area of 300m2(ii)/g; pore volume of 0.5 ml/g), drying and roasting after soaking, wherein the drying time is 4h and the drying temperature is 100 ℃; the roasting time is 4 hours, the temperature is 500 ℃, the zinc-loaded alumina is spherical, and the equivalent diameter of the zinc-loaded alumina is 3 mm;
spray soaking process: mixing a proper amount of zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, wherein the mass content of 2-methylimidazole in the slurry is 5%, then spraying and soaking zinc-loaded alumina with the slurry, drying and roasting to obtain a methane-oxyhalogenation conversion catalyst, wherein the drying time is 3 hours, and the drying temperature is 100 ℃; the roasting time is 4 hours, and the temperature is 450 ℃.
The catalyst properties were as follows: the catalyst has a core-shell structure, wherein the core is aluminum oxide loaded with zinc, and the shell is aluminum oxide containing solid zirconium sulfate acid, wherein the weight ratio of the aluminum oxide loaded with zinc to the aluminum oxide containing solid zirconium sulfate acid is 5: 1; the zirconium sulfate solid acid content was 15% by weight, based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc content was 10% by weight, calculated as oxide, based on the weight of the alumina supporting zinc; the thickness of the shell was 60 μm.
The above catalyst was evaluated for the oxyhalogenation of methane under the same conditions as in example 1, and the evaluation results are shown in Table 1.
Example 8
Preparing aluminum hydroxide slurry by adopting a carbonization method of introducing carbon dioxide gas into sodium metaaluminate solution: will contain 30wt% CO2CO of2/N2Introducing the mixed gas into sodium metaaluminate solution, carrying out gelling reaction at 30 ℃, controlling the pH value of the reaction end point to be 10.5-11.0, and aging after the reaction is finishedWashing the mixture at 60 ℃ by deionized water until the pH of the filtrate is 6.5 to obtain aluminum hydroxide slurry with the solid content of 31.2 wt%;
preparation of zinc-loaded alumina: the method is carried out by soaking in alumina (commercially available product with the following properties: L acid content of 0.1 mmol.g)-1(ii) a BET specific surface area of 300m2(ii)/g; pore volume of 0.5 ml/g), drying and roasting after soaking, wherein the drying time is 3 hours and the drying temperature is 120 ℃; the roasting time is 5 hours, the temperature is 450 ℃, the zinc-loaded alumina is spherical, and the equivalent diameter of the zinc-loaded alumina is 2 mm; carrying out hydrothermal treatment on the zinc-loaded alumina by adopting water vapor nitrogen mixed gas with the volume content of 5%, wherein the treatment temperature is 200 ℃, and the treatment time is 10 min.
Spray soaking process: mixing a proper amount of zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, wherein the mass content of 2-methylimidazole in the slurry is 5%, then spraying and soaking zinc-loaded alumina with the slurry, drying and roasting to obtain a methane-oxyhalogenation conversion catalyst, wherein the drying time is 3 hours, and the drying temperature is 100 ℃; the roasting time is 4 hours, and the temperature is 450 ℃.
The catalyst properties were as follows: the catalyst has a core-shell structure, wherein the core is aluminum oxide loaded with zinc, and the shell is aluminum oxide containing solid zirconium sulfate acid, wherein the weight ratio of the aluminum oxide loaded with zinc to the aluminum oxide containing solid zirconium sulfate acid is 7: 1; the zirconium sulfate solid acid content was 11% by weight, based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc content was 15% by weight, calculated as oxide, based on the weight of the alumina supporting zinc; the thickness of the shell was 30 μm.
Comparative example 1
Preparing zirconium sulfate solid acid modified alumina by adopting an aluminum isopropoxide hydrolysis method: mixing water and aluminum isopropoxide according to a molar ratio of 120:1, controlling the hydrolysis temperature at 80-85 ℃, hydrolyzing the aluminum isopropoxide for 1.5h, aging at 90-95 ℃ for 18h to obtain aluminum hydroxide slurry with a solid content of 21.3wt%, mixing an appropriate amount of zirconium sulfate solid acid and the aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing zirconium sulfate solid acid, and filtering, drying and roasting to obtain zirconium sulfate solid acid modified aluminum oxide;
preparation of zinc-loaded alumina: an isovolumetric impregnation method is adopted to prepare alumina (a commercial product, the property is as follows: the L acid content is 0.2 mmol.g)-1(ii) a A BET specific surface area of 200; pore volume of 0.3 ml/g), drying and roasting after soaking, wherein the drying time is 2 hours and the drying temperature is 130 ℃; the roasting time is 4 hours, the temperature is 400 ℃, and the zinc-loaded alumina is in a powder shape;
mixing and kneading the zirconium sulfate solid acid modified alumina and zinc-loaded alumina powder, adding 2-methylimidazole with the same mass as that in the embodiment, drying and roasting to obtain the catalyst. The weight ratio of the alumina loaded with zinc to the alumina containing solid acid of zirconium sulfate in the catalyst is 8: 1; the catalyst composition was the same as in example 1 except that the content of zirconium sulfate solid acid was 8% by weight based on the weight of alumina containing zirconium sulfate solid acid and the content of zinc in terms of oxide was 25% by weight based on the weight of alumina supporting zinc.
The above catalyst was evaluated for the oxyhalogenation of methane under the same conditions as in example 1, and the evaluation results are shown in Table 1.
TABLE 1 results of different catalysts used in the bromination of methane
Claims (12)
1. A method for preparing a methane conversion catalyst, which is characterized by comprising the following steps: the method comprises the following steps: mixing zirconium sulfate solid acid, 2-methylimidazole and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid and 2-methylimidazole, then spraying aluminum oxide loaded with zinc by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid and 2-methylimidazole, drying and roasting to obtain the methane conversion catalyst.
2. The method of claim 1, wherein: the zirconium sulfate solid acid is prepared by adopting a commercial product or according to the prior art.
3. The method of claim 1, wherein: the preparation of the zinc-loaded alumina adopts the steps of impregnating and loading a zinc-containing compound on the formed alumina or kneading and forming the zinc-containing compound and alumina powder, and then drying and roasting to prepare the zinc-loaded alumina.
4. The method of claim 3, wherein: the zinc-containing compound is one or more of zinc nitrate, zinc sulfate, zinc bromide and zinc chloride.
5. The method of claim 3, wherein: the drying time is 1-5h, and the drying temperature is 90-150 ℃; the roasting time is 3-8h, and the temperature is 300-700 ℃.
6. The method of claim 1, wherein: the weight content of the 2-methylimidazole in the aluminum hydroxide slurry containing the zirconium sulfate solid acid and the 2-methylimidazole is 1-10%.
7. The method of claim 1, wherein: before aluminum hydroxide slurry containing zirconium sulfate solid acid and 2-methylimidazole is used for spray-soaking zinc-loaded aluminum oxide, the zinc-loaded aluminum oxide is treated by adopting water vapor nitrogen mixed gas with the water vapor volume content of 1-15%, the treatment temperature is 150-300 ℃, and the treatment time is 5-30 min.
8. A catalyst prepared by the process of any one of claims 1 to 7, wherein: the catalyst has a shell-core structure, wherein the core of the catalyst is alumina loaded with zinc, and the shell of the catalyst is alumina containing solid zirconium sulfate acid, wherein the weight ratio of the alumina loaded with zinc to the alumina containing solid zirconium sulfate acid is 10:1-2: 1; the zirconium sulfate solid acid is present in an amount of 5 to 15wt% based on the weight of the alumina containing the zirconium sulfate solid acid, and zinc is present in an amount of 5 to 30wt% in terms of oxide, based on the weight of the alumina supporting zinc.
9. The catalyst of claim 8, wherein: the weight ratio of the zinc-loaded alumina to the zirconium sulfate-containing solid acid-containing alumina is 8:1-5: 1; the zirconium sulfate solid acid is present in an amount of 8 to 10wt% based on the weight of the alumina containing the zirconium sulfate solid acid, and zinc is present in an amount of 10 to 25wt% in terms of oxide, based on the weight of the alumina supporting zinc.
10. The catalyst of claim 8, wherein: the shell has a thickness of 5 μm to 200 μm.
11. The catalyst of claim 8, wherein: the zinc-loaded alumina is spherical or strip-shaped; the equivalent diameter of the zinc-loaded alumina is 1mm-5 mm.
12. Use of the catalyst of claim 8 in methane conversion, wherein: the fixed bed process is adopted, methane, oxygen and halogen acid are taken as reactants or methane, oxygen and halogen acid aqueous solution are taken as reactants to carry out the oxyhalogenation conversion of methane under the action of a catalyst, the reaction temperature is 250-.
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