CN108067266B - Core-shell type catalyst and preparation method and application thereof - Google Patents
Core-shell type catalyst and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a core-shell catalyst and a preparation method and application thereof. The core is zinc-loaded composite metal oxide NdCoO with perovskite structure3‑yY is oxygen vacancy, the shell is alumina containing zirconium sulfate solid acid, and the zinc-supported composite metal oxide NdCoO with a perovskite structure is loaded3‑yThe weight ratio of the aluminum oxide to the solid acid containing zirconium sulfate is 10:1-2: 1; based on the weight of alumina containing zirconium sulfate solid acid, the weight content of the zirconium sulfate solid acid is 5 to 10 weight percent, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure is used3‑yThe zinc content is 5wt% to 30wt% calculated on oxide basis. The catalyst 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 core-shell catalyst and a preparation method and application thereof, in particular to a low-temperature high-activity and selective core-shell catalyst and a preparation method and application thereof.
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 active ingredient, Bromhead et al (Bromhead J, Font-free J, Westlake D J. Process for the production of methyl or ethyl mono-chloride or bromide. EP. Patent, 0117731.1984-09-05) load 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, O2Cl form of activated catalyst surfaceAnd (3) forming OCl, activating the methane by the OCl to form Cl, and mutually converting the Cl and the OCl to carry out oxychlorination.
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 core-shell type catalyst and a preparation method and application thereof. The catalyst 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.
The core-shell catalyst has zinc-supported composite metal oxide NdCoO with perovskite structure as core3-yY is oxygen vacancy, the shell is alumina containing zirconium sulfate solid acid, and the zinc-supported composite metal oxide NdCoO with a perovskite structure is loaded3-yThe weight ratio of the zirconium sulfate-containing solid acid to the alumina containing the zirconium sulfate solid acid is 10:1-2:1, preferably 8:1-5: 1; the zirconium sulfate solid acid content is 5-10 wt%, preferably 8-15 wt%, based on the weight of the alumina containing the zirconium sulfate solid acid, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure is used as a carrier3-yThe zinc content, calculated as oxide, is from 5% to 30% by weight, preferably from 10% to 25% by weight, based on the weight.
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-supported composite metal oxide NdCoO having a perovskite structure3-yCan be spherical or strip-shaped, and is preferably spherical; zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe equivalent diameter is 1mm to 5mm, preferably 2mm to 5mm, and most preferably 2mm to 3 mm.
A preparation method of a core-shell type catalyst comprises the following steps: mixing zirconium sulfate solid acid with aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, and spray-leaching the zinc-loaded composite metal oxide NdCoO with the perovskite structure with the aluminum hydroxide slurry containing the zirconium sulfate solid acid3-yWherein y is oxygen vacancy, and the core-shell type catalyst is prepared after drying and roasting.
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 composite metal oxide NdCoO having a perovskite structure3-yCan be prepared by the conventional technology, and comprises the step of loading zinc on the composite metal oxide NdCoO with the perovskite structure3-yAny one of the methods above. Specifically, the method can adopt the method that a zinc-containing compound is impregnated and loaded on a formed composite metal oxide NdCoO with a perovskite structure3-yOr a zinc-containing compound and a composite metal oxide NdCoO with a perovskite structure3-yThe powder is kneaded and molded, and then the powder is dried and roasted to prepare the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-yWherein y is an oxygen vacancy. The composite metal oxide NdCoO with the perovskite structure3-yThe zinc-containing compound can be prepared by adopting the prior art, and 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 method, the zinc-supporting composite metal oxide NdCoO having a perovskite structure is spray-impregnated with an aluminum hydroxide slurry containing a solid acid of zirconium sulfate3-yBefore, the composite metal oxide NdCoO with the perovskite structure loaded with zinc is preferably subjected to a mixed gas of water vapor and nitrogen with the water vapor volume content of 1-15%, preferably 1-5%3-yThe treatment is carried out at the temperature of 150-. Research results show that the treatment method can improve the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-yThe hydroxyl content on the surface is not increased at the same time, so that the hydrogen of the solid acid containing zirconium sulfateThe alumina slurry can be uniformly sprayed and soaked on the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-yAround, the hydrogen-oxygen bond of aluminium hydroxide can be simultaneously supported with the zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe surface is bonded with rich hydroxyl groups, so that the pore channels are communicated, and the activity of the catalyst and the selectivity of a target product are improved.
The application of the catalyst in the core-shell type adopts a fixed bed process, takes methane, oxygen and halogen acid as reactants or takes a methane, oxygen and halogen acid aqueous solution as reactants to carry out the core-shell type reaction under the action of the catalyst, the reaction temperature is 250-600 ℃, the preferred temperature is 300-450 ℃, the feeding volume ratio of the methane, the halogen acid and the oxygen is (3-5): 1-3):1, and the flow rate of the methane is 10-50ml/min, the preferred flow rate is 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 core-shell type reactions involve methane steam reforming reactions, methane oxidation reactions 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 to a composite metal oxide NdCoO with a perovskite structure and with zinc loaded in the inner core of the catalyst3-yThe catalyst has rich oxygen vacancies, the oxygen concentration in the core is improved, the reaction of converting halogen acid into halogen free radicals is more favorably carried out, a small amount of methane halogenation reaction occurs, the shell is alumina containing zirconium sulfate solid acid and mainly carries out the methane halogenation reaction, the halogen free radicals generated by the core can be quickly diffused into the shell to carry out the methane halogenation reaction, and the generated halohydrocarbon is quickly diffused to the outside of the catalyst, so that the further oxidation of the catalyst is prevented, and the selectivity of the halohydrocarbon and the conversion rate of methane are obviously improved.
Detailed Description
The core-shell catalyst, its preparation and application and effects are further illustrated by the following examples, which are not intended to limit the scope of 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.
NdCoO3-yThe preparation of (a) was as follows: preparing a mixed aqueous solution containing neodymium nitrate and cobalt nitrate, wherein the molar ratio of the total amount of metal ions in the citric acid and the mixed aqueous solution is 2:1, weighing a proper amount of citric acid, slowly adding the citric acid into the mixed aqueous solution, and stirring while dropwise adding. After stirring for 5 hours, the brown solution had been dehydrated to a sticky gel, which was taken out into a drying cabinet at 110 ℃ and dried overnight. Then taking out the dried precursor, placing the precursor in a muffle furnace to be roasted for 6 hours at the constant temperature of 700 ℃, and obtaining the composite metal oxide NdCoO with the perovskite structure after molding3-yAnd y is an oxygen vacancy.
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 composite metal oxide NdCoO with perovskite structure3-y: soaking a zinc nitrate solution in NdCoO3-y 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 composite metal oxide NdCoO with the perovskite structure3-ySpherical zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe equivalent diameter 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, and spray-soaking the zinc-loaded composite metal oxide NdCoO with the perovskite structure by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid3-yDrying and roasting to prepare the core-shell 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, and the core is a composite metal oxide NdCoO with a zinc-loaded perovskite structure3-yThe shell is alumina containing zirconium sulfate solid acid, wherein the zinc-loaded composite metal oxide NdCoO with a perovskite structure3-yThe weight ratio of the alumina to the solid acid containing zirconium sulfate is 8: 1; based on the weight of alumina containing zirconium sulfate solid acid, the weight content of the zirconium sulfate solid acid is 8wt%, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure is used as a carrier3-yThe zinc content, calculated as oxide, is 25% by weight, based on the weight; 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 composite metal oxide NdCoO with perovskite structure3-y: by adopting an equal volume impregnation method on NdCoO3-yDipping zinc sulfate solution, drying and roasting after dipping, wherein the drying time is 3h, and the drying temperature is 120 ℃; the roasting time is 5h, the temperature is 450 ℃, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-ySpherical zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe equivalent diameter 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, and spray-soaking the zinc-loaded composite metal oxide NdCoO with the perovskite structure by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid3-yDrying and roasting to prepare the core-shell 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, and the core is a composite metal oxide NdCoO with a zinc-loaded perovskite structure3-yThe shell is alumina containing zirconium sulfate solid acid, wherein the zinc-loaded composite metal oxide NdCoO with a perovskite structure3-yThe weight ratio of the alumina to the solid acid containing zirconium sulfate is 7: 1; the zirconium sulfate solid acid content was 11wt% based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc-supported composite metal oxide NdCoO having a perovskite structure was used3-yThe zinc content, calculated as oxide, is 15% by weight, based on the weight; 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 composite metal oxide NdCoO with perovskite structure3-y: by adopting an equal volume impregnation method on NdCoO3-yDipping zinc bromide solution, drying and roasting after dipping, wherein the drying time is 4h, and the drying temperature is 100 ℃; the roasting time is 4 hours, the temperature is 500 ℃, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-ySpherical zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe equivalent diameter is 3 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, and spray-soaking the zinc-loaded composite metal oxide NdCoO with the perovskite structure by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid3-yDrying and roasting to prepare the core-shell 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, and the core is a composite metal oxide NdCoO with a zinc-loaded perovskite structure3-yThe shell is alumina containing zirconium sulfate solid acid, wherein the zinc-loaded composite metal oxide NdCoO with a perovskite structure3-yThe weight ratio of the alumina to the solid acid containing zirconium sulfate is 5: 1; the zirconium sulfate solid acid content was 15wt% based on the weight of the alumina containing zirconium sulfate solid acid, to support the zinc-carrying composite metal oxide NdCoO having a perovskite structure3-yThe zinc content, calculated as oxide, is 10% by weight, based on the weight; 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 composite metal oxide NdCoO with perovskite structure3-y: by adopting an equal volume impregnation method on NdCoO3-yDipping zinc sulfate solution, drying and roasting after dipping, wherein the drying time is 3 hours, and the drying temperature is 120 ℃; the roasting time is 5h, the temperature is 450 ℃, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-ySpherical zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe equivalent diameter is 2 mm; adopting water vapor nitrogen mixed gas with volume content of 1 percent to carry the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-yPerforming hydrothermal treatment at 200 deg.C for 10 min.
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, and spray-soaking the zinc-loaded composite metal oxide NdCoO with the perovskite structure by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid3-yDrying and roasting to prepare the core-shell 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, and the core is a composite metal oxide NdCoO with a zinc-loaded perovskite structure3-yThe shell is alumina containing zirconium sulfate solid acid, wherein the zinc-loaded composite metal oxide NdCoO with a perovskite structure3-yThe weight ratio of the alumina to the solid acid containing zirconium sulfate is 7: 1; the zirconium sulfate solid acid content was 11wt% based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc-supported composite metal oxide NdCoO having a perovskite structure was used3-yThe zinc content, calculated as oxide, is 15% by weight, based on the weight; 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 composite metal oxide NdCoO with perovskite structure3-y: by adopting an equal volume impregnation method on NdCoO3-yDipping in zinc nitrate solution, drying and roasting after dipping, 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 composite metal oxide NdCoO with the perovskite structure3-ySpherical zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe equivalent diameter 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, and spray-soaking the zinc-loaded composite metal oxide NdCoO with the perovskite structure by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid3-yDrying and roasting to prepare the core-shell 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, and the core is a composite metal oxide NdCoO with a zinc-loaded perovskite structure3-yThe shell is alumina containing zirconium sulfate solid acid, wherein the zinc-loaded composite metal oxide NdCoO with a perovskite structure3-yThe weight ratio of the alumina to the solid acid containing zirconium sulfate is 8: 1; based on the weight of alumina containing zirconium sulfate solid acid, the weight content of the zirconium sulfate solid acid is 8wt%, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure is used as a carrier3-yThe zinc content, calculated as oxide, is 25% by weight, based on the weight; 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
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 composite metal oxide NdCoO with perovskite structure3-y: by adopting an equal volume impregnation method on NdCoO3-yDipping zinc sulfate solution, drying and roasting after dipping, wherein the drying time is 3 hours, and the drying temperature is 120 ℃; the roasting time is 5h, the temperature is 450 ℃, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-ySpherical zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe equivalent diameter 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, and spray-soaking the zinc-loaded composite metal oxide NdCoO with the perovskite structure by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid3-yDrying and roasting to prepare the core-shell 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, and the core is a composite metal oxide NdCoO with a zinc-loaded perovskite structure3-yThe shell is alumina containing zirconium sulfate solid acid, wherein the zinc-loaded composite metal oxide NdCoO with a perovskite structure3-yThe weight ratio of the alumina to the solid acid containing zirconium sulfate is 7: 1; the zirconium sulfate solid acid content was 11wt% based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc-supported composite metal oxide NdCoO having a perovskite structure was used3-yThe zinc content, calculated as oxide, is 15% by weight, based on the weight; 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/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 composite metal oxide NdCoO with perovskite structure3-y: by adopting an equal volume impregnation method on NdCoO3-yDipping zinc bromide solution, drying and roasting after dipping, wherein the drying time is 4h, and the drying temperature is 100 ℃; the roasting time is 4 hours, the temperature is 500 ℃, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-ySpherical zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe equivalent diameter is 3 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, and spray-soaking the zinc-loaded composite metal oxide NdCoO with the perovskite structure by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid3-yDrying and roasting to prepare the core-shell 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, and the core is a composite metal oxide NdCoO with a zinc-loaded perovskite structure3-yThe shell is alumina containing zirconium sulfate solid acid, wherein the zinc-loaded composite metal oxide NdCoO with a perovskite structure3-yThe weight ratio of the alumina to the solid acid containing zirconium sulfate is 5: 1; based on the weight of alumina containing zirconium sulfate solid acidThe zirconium sulfate solid acid content was 15wt% to support the zinc composite metal oxide NdCoO having a perovskite structure3-yThe zinc content, calculated as oxide, is 10% by weight, based on the weight; 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 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 composite metal oxide NdCoO with perovskite structure3-y: by adopting an equal volume impregnation method on NdCoO3-yDipping zinc sulfate solution, drying and roasting after dipping, wherein the drying time is 3 hours, and the drying temperature is 120 ℃; the roasting time is 5h, the temperature is 450 ℃, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-ySpherical zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe equivalent diameter is 2 mm; adopting 5 percent of water vapor nitrogen mixed gas to carry the zinc composite metal oxide NdCoO with the perovskite structure3-yPerforming hydrothermal treatment at 200 deg.C for 10 min.
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, and spray-soaking the zinc-loaded composite metal oxide NdCoO with the perovskite structure by using the aluminum hydroxide slurry containing the zirconium sulfate solid acid3-yDrying and roasting to prepare the core-shell 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, and the core is negativeZinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe shell is alumina containing zirconium sulfate solid acid, wherein the zinc-loaded composite metal oxide NdCoO with a perovskite structure3-yThe weight ratio of the alumina to the solid acid containing zirconium sulfate is 7: 1; the zirconium sulfate solid acid content was 11wt% based on the weight of the alumina containing zirconium sulfate solid acid, and the zinc-supported composite metal oxide NdCoO having a perovskite structure was used3-yThe zinc content, calculated as oxide, is 15% by weight, based on the weight; 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 composite metal oxide NdCoO with perovskite structure3-y: by adopting an equal volume impregnation method on NdCoO3-yDipping in zinc nitrate solution, drying and roasting after dipping, 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 composite metal oxide NdCoO with the perovskite structure3-yIs powder;
zirconium sulfate solid acid modified alumina and zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe powder is kneaded, molded, dried and roasted to obtain the catalyst. Composite metal oxide NdCoO with perovskite structure and loaded with zinc in catalyst3-yThe weight ratio of the alumina to the solid acid containing zirconium sulfate is 8: 1; based on the weight of alumina containing zirconium sulfate solid acid, the weight content of the zirconium sulfate solid acid is 8wt%, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure is used as a carrier3-yWeight (D)The catalyst had the same composition as in example 1, except that the content of zinc calculated as oxide was 25 wt%.
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 (15)
1. A core-shell catalyst characterized by: the core is zinc-loaded composite metal oxide NdCoO with perovskite structure3-yY is oxygen vacancy, the shell is alumina containing zirconium sulfate solid acid, and the zinc-supported composite metal oxide NdCoO with a perovskite structure is loaded3-yThe weight ratio of the aluminum oxide to the solid acid containing zirconium sulfate is 10:1-2: 1; based on the weight of alumina containing zirconium sulfate solid acid, the weight content of the zirconium sulfate solid acid is 5 to 15 weight percent, and the zinc-loaded composite metal oxide NdCoO with the perovskite structure is used3-yThe zinc content is 5wt% to 30wt% calculated on oxide basis.
2. The catalyst of claim 1, wherein: zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe weight ratio of the alumina to the solid acid containing zirconium sulfate is 8:1-5: 1; the weight content of the zirconium sulfate solid acid is 8-10 wt%, and the content of zinc calculated by oxide is 10-25 wt%.
3. The catalyst of claim 1, wherein: the shell has a thickness of 5-200 μm, and the zinc-supported composite metal oxide NdCoO has a perovskite structure3-yThe equivalent diameter is 1mm-5 mm.
4. The catalyst of claim 1, wherein: the shell has a thickness of 15-100 μm, and the zinc-loaded composite has a perovskite structureMetal oxide NdCoO3-yThe equivalent diameter is 2mm-5 mm.
5. A process for the preparation of a catalyst according to any one of claims 1 to 4, characterized in that: the method comprises the following steps: mixing zirconium sulfate solid acid with aluminum hydroxide slurry to obtain aluminum hydroxide slurry containing the zirconium sulfate solid acid, and spray-leaching the zinc-loaded composite metal oxide NdCoO with the perovskite structure with the aluminum hydroxide slurry containing the zirconium sulfate solid acid3-yDrying and roasting to obtain the core-shell catalyst.
6. The method of claim 5, wherein: the zirconium sulfate solid acid is prepared by adopting a commercial product or according to the prior art.
7. The method of claim 5, wherein: the aluminum hydroxide slurry is pseudo-boehmite slurry.
8. The method of claim 5, wherein: zinc-loaded composite metal oxide NdCoO with perovskite structure3-yThe preparation method adopts the steps of impregnating and loading a zinc-containing compound in the formed NdCoO3-yOr mixing zinc-containing compound with NdCoO3-yThe powder is kneaded and molded, and then the powder is dried and roasted to prepare the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-y。
9. The method of claim 8, wherein: the NdCoO3-yThe zinc-containing compound is prepared according to the prior art, and is one or more of zinc nitrate, zinc sulfate, zinc bromide and zinc chloride.
10. The method of claim 8, 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 ℃.
11. The method of claim 10, wherein: the drying time is 2-4h, and the drying temperature is 100-130 ℃; the roasting time is 4-6h, and the temperature is 400-500 ℃.
12. The method of claim 5, wherein: spray-leaching zinc-loaded composite metal oxide NdCoO with perovskite structure by using aluminum hydroxide slurry containing zirconium sulfate solid acid3-yBefore, the mixed gas of water vapor and nitrogen with the water vapor volume content of 1-15 percent is adopted to carry the zinc-loaded composite metal oxide NdCoO with the perovskite structure3-yAnd (6) processing.
13. The method of claim 12, wherein: the treatment temperature is 150 ℃ and 300 ℃, and the treatment time is 5-30 min.
14. The method of claim 13, wherein: the treatment temperature is 180 ℃ and 200 ℃, and the treatment time is 5-10 min.
15. Use of a catalyst according to any one of claims 1 to 4 in the core-shell type, characterized in that: by adopting a fixed bed process, the method takes methane, oxygen and halogen acid as reactants or takes a methane, oxygen and halogen acid aqueous solution as reactants to carry out core-shell reaction, the reaction temperature is 250-600 ℃, the feeding volume ratio of the methane, the halogen acid and the oxygen is (3-5): 1-3):1, and the flow rate of the methane is 10-50 ml/min.
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