CN108067262B

CN108067262B - Preparation method of high-selectivity methane oxyhalogen oxidation catalyst

Info

Publication number: CN108067262B
Application number: CN201610990985.6A
Authority: CN
Inventors: 李�杰; 张信伟; 尹泽群; 刘全杰; 倪向前
Original assignee: China Petroleum and Chemical Corp; Sinopec Fushun Research Institute of Petroleum and Petrochemicals
Current assignee: China Petroleum and Chemical Corp; Sinopec Fushun Research Institute of Petroleum and Petrochemicals
Priority date: 2016-11-11
Filing date: 2016-11-11
Publication date: 2020-09-11
Anticipated expiration: 2036-11-11
Also published as: CN108067262A

Abstract

The invention discloses a preparation method of a high-selectivity methane oxyhalogen oxidation catalyst, which comprises the following steps: (1) soaking alumina in acidic solution of sugar, and aging, drying and roasting to obtain modified alumina; (2) loading zinc on the modified alumina prepared in the step (1), drying and roasting to prepare zinc-loaded alumina (3), and mixing zirconium sulfate solid acid with aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing zirconium sulfate solid acid; (4) and (3) spraying and soaking aluminum oxide loaded with zinc by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid prepared in the step (3), and drying and roasting to obtain the methane oxyhalide catalyst.

Description

Preparation method of high-selectivity methane oxyhalogen oxidation catalyst

Technical Field

The invention relates to a preparation method of a high-selectivity methane oxyhalogen oxidation catalyst, in particular to a preparation method of a low-temperature high-selectivity methane oxyhalogen oxidation catalyst.

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) loaded CuCl on alumina₂To prepare the oxychlorination catalyst. Conner et al (Conner W C Jr, Pieters W J M, Gates W, et al, The oxydydrochlorination of methane on fumedsilica-based Cu, K, La catalysts: II. Gas phase stoichiometry. Appl Catal,1984, 11(1): 49-58；Conner W C Jr, Pieters W J M, Signorelli A J. Theoxyhydrochlorination of methane on fumed silica-based Cu, K, La catalysts: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]. AngewendteChemie 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 wtFeO_x-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 TiO₂One or more of-SiC, wherein the weight content of the main active component is 1.0-50.0% of the weight of the catalyst, and the catalyst is prepared by adopting an impregnation methodThe catalyst can catalyze the mixture of methane, oxygen and HBr aqueous solution to be converted into methyl bromide and CO with 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 high-selectivity methane oxyhalogen oxidation 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.

A method of preparing a methane halooxidation catalyst comprising the steps of:

(1) soaking alumina in acidic solution of sugar, and aging, drying and roasting to obtain modified alumina;

(2) loading zinc on the modified alumina prepared in the step (1), drying and roasting to prepare the zinc-loaded alumina

(3) Mixing zirconium sulfate solid acid with aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid;

(4) and (4) carrying out spray leaching on the zinc-loaded alumina by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid prepared in the step (3), and drying and roasting to obtain the methane oxyhalide oxidation catalyst.

The methane halide oxidation catalyst prepared by the method 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 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.

The catalyst prepared by the method has the shell thickness of 5-200 μm, preferably 10-150 μm, and more preferably 15-100 μm.

In the catalyst prepared by the method, 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 sugar used in the above method, acidic solution of sugar used in step (1) includes various water-soluble sugars, such as various monosaccharides or disaccharides, specifically aqueous solutions of fructose, glucose, sucrose, maltose, etc., preferably an acidic solution of sucrose. The mass concentration of the sugar in the acidic solution of sugar is 1% to 35%, preferably 5% to 20%. The acidic solution containing sugar has a pH of 0.1 to 6.5, preferably a pH of 1 to 3, and the pH of the solution can be adjusted using any inorganic or organic acid, preferably hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, or the like. The aging temperature is 50-95 ℃, preferably 60-80 ℃, and the aging time is 0.5-10h, preferably 2-5 h. The drying temperature after aging is 90-150 ℃, the drying time is 0.5-36h, and the drying is preferably carried out at 100-120 ℃ for 8-24 h. The calcination is carried out at 280-500 ℃ for 2-15 hours, preferably at 300-450 ℃ for 3-5 hours. The acidic solution of sugar is adopted to treat the alumina, which is beneficial to the adsorption of halogen acid on the surface of the alumina, thereby promoting the oxyhalogen reaction.

The above-mentioned method, the preparation of the alumina supporting zinc in the step (2), can employ conventional techniques, 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-loaded 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 300-600 ℃, preferably 400-500 ℃.

The method, the zirconium sulfate solid acid in the step (3) can be prepared by using a commercial product or 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 method, before the aluminum hydroxide slurry containing zirconium sulfate solid acid is used for spray leaching of the zinc-loaded aluminum oxide in the step (3), the zinc-loaded aluminum oxide is preferably treated by using a water vapor nitrogen gas mixture with the water vapor volume content of 1-15%, preferably 1-5%, wherein the treatment temperature is 150-. 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.

In the method, the drying time in the step (4) is 1-5h, preferably 2-4h, and the drying temperature is 90-150 ℃, preferably 100-130 ℃; the roasting time is 3-8h, preferably 4-6h, and the temperature is 300-600 ℃, preferably 400-500 ℃.

The catalyst prepared by the method is applied to methane oxyhalogenation conversion by adopting 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-. 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. Specifically, the zinc-loaded alumina in the core of the catalyst is more beneficial to the reaction of converting halogen acid into halogen free radicals to generate a small amount of methane halogenation reaction, the zirconium sulfate solid acid-containing alumina in the shell mainly performs the methane halogenation reaction, the halogen free radicals generated in the core can be quickly diffused into the shell to perform 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 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 remarkably improved.

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 modified alumina: an equal volume impregnation method is adopted to prepare alumina (a commercial product, the properties are as follows: specific surface 335 m)²Per gram, the pore volume is 0.86 ml/g), the sucrose aqueous solution is dipped, the mass concentration of the sucrose aqueous solution is 5 percent, the pH value is 2, the aging temperature is 80 ℃, the aging time is 2 hours, the drying temperature after aging is 150 ℃, the drying time is 24 hours, and the mixture is roasted at 300 ℃ for 3 hours;

preparation of zinc-loaded alumina: soaking a zinc nitrate solution on the modified alumina by an isometric soaking method, 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;

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%.

Spray soaking process: mixing a proper amount of zirconium sulfate solid acid and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, then spray-soaking zinc-loaded alumina with the aluminum hydroxide slurry containing the zirconium sulfate solid acid, and 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 modified alumina: an equal volume impregnation method is adopted to prepare alumina (a commercial product, the properties are as follows: specific surface 335 m)²Per g, pore volume of 0.86 ml/g), the glucose solution is dipped, the weight concentration of the glucose solution is 20 percent, the pH value is preferably 3, the aging temperature is 60 ℃, the aging time is 5h, the drying temperature after aging is 100 ℃ for drying 8h, and the roasting is carried out at 450 ℃ for 3 h;

preparation of zinc-loaded alumina: soaking a zinc sulfate solution on the modified alumina by an isometric soaking method, 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 and aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, then spraying and soaking aluminum oxide loaded with zinc by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid, and 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 modified alumina: an equal volume impregnation method is adopted to prepare alumina (a commercial product, the properties are as follows: specific surface 335 m)²Per g, pore volume of 0.86 ml/g), soaking fructose aqueous solution with weight concentration of 10%, pH value of 1, aging temperature of 70 deg.C, aging time of 3.5 hr, and drying at 110 deg.C for 15 hr. Roasting for 4 hours at 380 ℃;

preparation of zinc-loaded alumina: soaking a zinc bromide solution on the modified alumina by adopting an isometric soaking method, and 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;

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.

Example 4

Preparing modified alumina: an equal volume impregnation method is adopted to prepare alumina (a commercial product, the properties are as follows: specific surface 335 m)²Per g, pore volume of 0.86 ml/g), the maltose water solution with weight concentration of 20%, pH 4, aging temperature of 80 deg.C, aging time of 2 hr, drying temperature after aging of 100 deg.C, and drying time of 14 hr. Roasting for 4 hours at 350 ℃;

preparation of zinc-loaded alumina: soaking a zinc sulfate solution on the modified alumina by an isometric soaking method, 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 1%, wherein the treatment temperature is 200 ℃, and the treatment time is 10 min.

Example 5

Preparing modified alumina: an equal volume impregnation method is adopted to prepare alumina (a commercial product, the properties are as follows: specific surface 335 m)²Per g, pore volume of 0.86 ml/g) with an aqueous sucrose solutionThe concentration is 5%, the pH value is 2, the aging temperature is 80 ℃, the aging time is 2h, the drying temperature after aging is 150 ℃, the drying time is 24h, and the roasting is carried out for 3h at 300 ℃;

preparation of zinc-loaded alumina: soaking a zinc nitrate solution on the modified alumina by an isometric soaking method, 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; 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%;

Example 6

An equal volume impregnation method is adopted to prepare alumina (a commercial product, the properties are as follows: specific surface 335 m)²/g，Pore volume of 0.86 ml/g), the mixture is dipped into a sucrose aqueous solution, the mass concentration of the sucrose aqueous solution is 5 percent, the pH value is 2, the aging temperature is 80 ℃, the aging time is 2 hours, the drying temperature after aging is 150 ℃, the drying time is 24 hours, and the mixture is roasted at 300 ℃ for 3 hours;

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%;

Example 7

An equal volume impregnation method is adopted to prepare alumina (a commercial product, the properties are as follows: specific surface 335 m)²Per gram, the pore volume is 0.86 ml/g), the sucrose aqueous solution is dipped, the mass concentration of the sucrose aqueous solution is 5 percent, the pH value is 2, the aging temperature is 80 ℃, the aging time is 2 hours, the drying temperature after aging is 150 ℃, the drying time is 24 hours, and the mixture is roasted at 300 ℃ for 3 hours;

Example 8

preparation of zinc-loaded alumina: soaking a zinc sulfate solution on the modified alumina by an isometric soaking method, 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.

Comparative example 1

preparation of zinc-loaded alumina: soaking a zinc nitrate solution on the modified alumina by an isometric soaking method, 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 powder

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;

the catalyst is prepared by kneading and molding zirconium sulfate solid acid modified alumina and zinc-loaded alumina powder, drying and roasting. 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.

TABLE 1 results of different catalysts used in the bromination of methane

Claims

1. A preparation method of a high-selectivity methane oxyhalogen oxidation catalyst comprises the following steps:

2. The method of claim 1, wherein: the methane halide oxidation 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 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.

3. The method of claim 2, wherein: the weight ratio of the zinc-loaded alumina to the zirconium sulfate-containing solid acid-containing alumina is 8:1-5: 1; based on the weight of the alumina containing the zirconium sulfate solid acid, the weight content of the zirconium sulfate solid acid is 8 to 10 weight percent, and the content of zinc calculated by oxide is 10 to 25 weight percent.

4. The method of claim 2, wherein: the thickness of the shell is 5-200 μm, and the equivalent diameter of the zinc-loaded alumina is 1-5 mm.

5. The method of claim 4, wherein: the thickness of the shell is 10-150 μm,

the equivalent diameter of the zinc-loaded alumina is 2mm-5 mm.

6. The method of claim 1, wherein: in the method, the sugar used in the acidic solution of sugar used in the step (1) is one of fructose, glucose, sucrose or maltose, the mass concentration of the sugar in the acidic solution of sugar is 1-35%, the pH value of the acidic solution containing sugar is 0.1-6.5, the aging temperature is 50-95 ℃, the aging time is 0.5-10h, the drying temperature after aging is 90-150 ℃, the drying time is 0.5-36h, and the roasting is carried out at the temperature of 280 ℃ and 500 ℃ for 2-15 h.

7. The method of claim 6, wherein: the mass concentration of sugar in the acidic solution of sugar is 5-20%, the pH value of the acidic solution containing sugar is 1-3, the aging temperature is 60-80 ℃, the aging time is 2-5h, the drying after aging is drying for 8-24h at the temperature of 100-450 ℃, and the roasting is carried out for 3-5 h at the temperature of 300-450 ℃.

8. The method of claim 1, wherein: the preparation of the zinc-loaded alumina in the step (2) adopts the conventional technology, and comprises any method of loading zinc on alumina, drying and roasting after loading.

9. The method of claim 8, wherein: the zinc-containing compound is soaked and loaded on the formed alumina or the zinc-containing compound and alumina powder are kneaded and formed, and then the zinc-loaded alumina is prepared by drying and roasting.

10. The method of claim 1, wherein: the drying time of the step (2) is 1-5h, and the drying temperature is 90-150 ℃; the roasting time is 3-8h, and the temperature is 400-500 ℃.

11. The method of claim 1, wherein: the zirconium sulfate solid acid in the step (3) is prepared by adopting a commercial product or according to the prior art, and the aluminum hydroxide slurry is pseudo-boehmite slurry.

12. The method of claim 1, wherein: before the aluminum hydroxide slurry containing the zirconium sulfate solid acid is used for spray-soaking the zinc-loaded aluminum oxide in the step (3), 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.

13. The method of claim 12, wherein: the zinc-loaded alumina is treated by adopting water vapor nitrogen mixed gas with the water vapor volume content of 1-5%, the treatment temperature is 180-200 ℃, and the treatment time is 5-15 min.

14. The method of claim 1, wherein: in the step (4), the drying time is 2-4h, and the drying temperature is 100-130 ℃; the roasting time is 3-8h, and the roasting temperature is 400-500 ℃.

15. Use of a catalyst prepared by the process of any one of claims 1 to 14 in the oxidative conversion of methane halide, characterized in that: 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-.