Catalyst for preparing p-methyl styrene through dehydrogenation of p-methyl ethylbenzene and reaction process method thereof

Abstract

The invention relates to a catalyst for preparing p-methyl styrene by dehydrogenation of p-methyl ethylbenzene and a reaction process method thereof. The catalyst mainly solves the problems of low selectivity of p-methylstyrene, poor dehydrogenation activity of the catalyst at a low water ratio and the like caused by serious two side reactions of isomerization and deethylation in a technology for preparing p-methylstyrene by dehydrogenation of p-methylethylbenzene. The invention also provides a bi-component pore-forming scheme for preparing internal mesopores of the catalyst, the pore volume and the specific surface area are obviously increased, the reaction activity and the carbon deposition resistance of the catalyst are effectively improved, and meanwhile, a reaction process method suitable for the methyl ethylbenzene dehydrogenation catalyst is also explored. In the reaction process of synthesizing p-methylstyrene by dehydrogenation of p-methyl ethylbenzene, carbon dioxide or nitrobenzene and water are simultaneously introduced as a reaction atmosphere medium, so that the reaction conversion rate can be further improved, reaction carbon deposition can be effectively controlled, and the reaction stability of the catalyst is well ensured.

Description

Technical Field

[0001] This invention relates to a catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene and a reaction process thereof, and further to the preparation of a p-methylethylbenzene dehydrogenation catalyst and a related fixed-bed reaction process thereof. Background Technology

[0002] p-Methylstyrene, due to the presence of a para-methyl group on the benzene ring within its monomer, hinders the rotation of the polymer chain, making polymer chain movement difficult, thus resulting in excellent thermodynamic properties. Copolymerization with common monomers can increase the glass transition temperature and thermal decomposition of the polymer, improving the material's processing properties. In recent years, its development and utilization abroad have begun, using it as a substitute for styrene raw materials in the synthesis of ABS, PS-type resins, etc. With economic development, the domestic market's requirements for materials are gradually increasing, and the importance of p-methylstyrene raw materials is becoming increasingly apparent. With increased attention, domestic research reports on p-methylstyrene have appeared in many fields, especially in organic synthesis and polymer materials applications, where it is highly favored.

[0003] The basic components of a catalyst for the dehydrogenation of methylethylbenzene to p-methylstyrene include a main catalyst, a co-catalyst, a pore-forming agent, and a binder. Early methylethylbenzene dehydrogenation catalysts were mainly Fe-K-Cr series, such as the published US patent UN4504594. Although these catalysts exhibited good activity and selectivity, the presence of Cr oxides in the catalysts caused environmental pollution. Fe-K-Ce catalysts effectively overcome this drawback. Replacing Cr with Ce significantly improves the catalyst's activity and stability while overcoming the high toxicity and environmental pollution associated with Cr. For example, published patents WO9710898, CN1233604, and CN1470325 demonstrate that the addition of Ce to catalysts for the dehydrogenation of methylethylbenzene to styrene can substantially improve catalyst activity and stability. However, these publications generally employ solid-phase mixing of all components to prepare the catalyst, and none of them report the reaction activity data of the Fe-K-Ce-Mo-La-Li catalytic system in the dehydrogenation of methylethylbenzene to p-methylstyrene. Existing catalysts for the dehydrogenation of p-methylethylbenzene to p-methylstyrene suffer from problems such as severe isomerization and deethylation side reactions, and low selectivity for p-methylstyrene. Furthermore, the reaction process for p-methylethylbenzene dehydrogenation is crucial. Studies have found that directly applying the previously reported and industrially produced water-oil mixed atmosphere reaction process for ethylbenzene dehydrogenation to p-methylstyrene results in poor catalyst stability. To address these issues, this invention proposes a catalyst composition formulation, preparation method, and reaction process for the dehydrogenation of p-methylethylbenzene. The process involves simultaneously introducing carbon dioxide or nitrobenzene and water as the reaction atmosphere medium. This water-carbon dioxide-oil or water-nitrobenzene-oil medium system not only stabilizes the catalyst activity but also further improves catalyst selectivity and increases the conversion rate of p-methylethylbenzene. Therefore, in the research of p-methylethylbenzene dehydrogenation to p-methylstyrene, not only should the exploration and innovation of novel catalyst systems be emphasized, but the development of suitable new reaction process methods is also an important and indispensable goal. Summary of the Invention

[0004] One of the technical solutions provided by this invention addresses the shortcomings of existing catalysts, such as low activity at low water ratios and numerous side reactions like isomerization, by providing a novel p-methylethylbenzene dehydrogenation catalyst. The catalyst prepared by this method exhibits high activity and good selectivity.

[0005] The second technical solution provided by this invention is a method for preparing a catalyst adapted to one of the technical problems.

[0006] The third technical solution provided by this invention is a reaction process method that stabilizes catalyst activity and improves selectivity.

[0007] One of the above-mentioned technical solutions provided by the present invention includes the following specific contents: This invention provides a catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene. The catalyst comprises, by weight percentage: 50%-70% iron oxide; 6%-15% potassium oxide; 4%-13% cerium oxide; at least three of the following components: Co, Mo, Zr, Ba, Cu, Bi, and La, each component comprising 3%-10% as oxides; alkali metal lithium oxide modification introduced by impregnation, comprising 1%-5% as oxides; the remainder being a binder; and mesoporous channels are introduced during catalyst forming by adding a pore-forming agent at 5%-10% of the catalyst raw material weight and then removing it by calcination.

[0008] Preferably, the introduction of at least three components, Co, Mo, Zr, Ba, Cu, Bi, and La, is carried out by either a dry uniform mixing method with metal oxides or a method of immersion in metal salt solution followed by calcination.

[0009] In one embodiment of the present invention, Co is added in the form of cobalt tetroxide (Co3O4) or cobalt nitrate (Co(NO3)2), Mo is added in the form of molybdenum trioxide (MoO3) or ammonium molybdate ((NH4)2MoO4), Zr is added in the form of zirconium dioxide (ZrO2) or zirconium nitrate (Zr(NO3)4), Ba is added in the form of barium oxide (BaO) or barium nitrate (Ba(NO3)2), Cu is added in the form of copper oxide (CuO) or copper nitrate, Bi is added in the form of bismuth trioxide (Bi2O3) or bismuth nitrate (Bi(NO3)3), La is added in the form of lanthanum oxide (La2O3) or lanthanum nitrate (La(NO3)3), and Li is added by impregnation with an aqueous solution of lithium carbonate (Li2CO3).

[0010] Preferably, the adhesive is selected from any one of silicate cement, alumina sol, and silica sol.

[0011] In the catalyst forming process, the present invention adds a pore-forming agent at a weight of 5%-10% relative to the catalyst raw material; the pore-forming agent, as a template agent, forms mesopores in the catalyst after being removed by calcination.

[0012] The porogen is composed of two components: one is one of polyacrylic acid, polyacrylamide, and polyethylene glycol, used at 1%-5% of the catalyst raw material weight; the other is one of guar gum powder and bamboo fiber, used at 3%-8% of the catalyst raw material weight. The catalyst prepared from this porogen forms 2-5 nm nanoporous channels conducive to reaction, with a pore volume of 0.30-0.60 ml / g and a specific surface area of ​​50-150 m². 2 / g. The pore volume and specific surface area are significantly increased, which improves reaction diffusion and exposes more active sites in contact with the reactants, thereby increasing the conversion rate. At the same time, it also improves the catalyst's ability to resist carbon buildup and blockage. This is one of the unique features of the catalyst of the present invention.

[0013] In one embodiment of the present invention, the adhesive weight content is 10%-30% in terms of oxides.

[0014] The second technical solution provided by this invention is a method for preparing a catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene, comprising an alkali metal Li-modified surface acid-base method, including the following steps: (1) Mix iron oxide, potassium oxide, cerium salt or cerium oxide, at least three metal compounds selected from Co, Mo, Zr, Ba, Cu, Bi, La, a pore-forming agent and a binder evenly; The amount of pore-forming agent added is 5%-10% relative to the weight of the catalyst raw material. The pore-forming agent is a mixture composed of one of polyacrylic acid, polyacrylamide, and polyethylene glycol and one of guar gum powder and bamboo fiber. Optionally, one of polyacrylic acid, polyacrylamide, and polyethylene glycol accounts for 1%-5% of the weight of the catalyst raw material, and one of guar gum powder and bamboo fiber accounts for 3%-8% of the weight of the catalyst raw material. (2) Knead and extrude or compress the material from step (1) into tablets; (3) The shaped material is roasted at 500~800℃ for 2~6 hours; (4) Impregnate the catalyst precursor obtained in step (3) with a solution containing lithium compounds, then dry and calcine at 300~600℃ for 2~4 hours to obtain the final catalyst.

[0015] In one embodiment of the present invention, a method for preparing a catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene includes the following steps: Iron oxide, potassium oxide, and a binder are mixed to obtain a powder; the pore-forming agent, cerium nitrate, lanthanum nitrate, ammonium molybdate, copper nitrate, and deionized water are mixed to obtain a solution; the powder and solution are mixed to obtain a mixture raw material; the mixture raw material is sequentially kneaded, aged, first dried, first calcined, and impregnated with lithium carbonate aqueous solution; the impregnated material is sequentially subjected to a second dried and a second calcined to obtain a catalyst. The binder is selected from any one of silicate cement, alumina sol, and silica sol. The pore-forming agent is polyacrylic acid and bamboo fiber, or polyacrylic acid and guar gum powder.

[0016] In one embodiment of the present invention, the mass percentage of iron oxide in the mixed raw materials is 38wt%-42wt%; the mass percentage of potassium oxide in the mixed raw materials is 7wt%-9wt%; the mass percentage of binder in the mixed raw materials is 2wt%-5wt%; the mass percentage of pore-forming agent in the mixed raw materials is 5wt%-7wt%; and the mass percentage of deionized water in the mixed raw materials is 22wt%-26wt%.

[0017] In one embodiment of the present invention, the amount of raw materials is calculated relative to the weight of the catalyst raw materials; cerium oxide is added in the form of cerium nitrate, and the mass percentage of cerium nitrate in the mixture raw materials is 7wt%-9wt%; La is added in the form of lanthanum nitrate, and the mass percentage of lanthanum nitrate in the mixture raw materials is 2wt%-4wt%; Mo is added in the form of ammonium molybdate, and the mass percentage of ammonium molybdate in the mixture raw materials is 2wt%-3wt%; Cu is added in the form of copper nitrate, and the mass percentage of copper nitrate in the mixture raw materials is 2wt%-3wt%.

[0018] In one embodiment of the present invention, the aging temperature is 25-30°C, preferably room temperature, and the aging time is 24-26 hours; the first drying temperature is 80-100°C and the time is 3-4 hours; the first calcination temperature is 500-800°C and the time is 3-6 hours; the lithium carbonate aqueous solution is impregnated for 2-3 hours; the mass concentration of lithium carbonate in the lithium carbonate aqueous solution is 7%-8% (w / w); the second drying temperature is 110-120°C and the time is 2-3 hours; the second calcination temperature is 500-600°C and the time is 2-4 hours.

[0019] In this invention, conventional polyacrylamide in the art can be used to achieve the effects of this invention, and will not be described in detail here. Polyacrylamide with a molecular weight of 5000-8000kDa can be selected.

[0020] The third technical solution provided by the present invention is a reaction process for the dehydrogenation of p-methylethylbenzene to p-methylstyrene; the catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene prepared by the catalyst of the first technical solution or the preparation method described in the second technical solution is used; carbon dioxide or nitrobenzene and water are introduced simultaneously as a reaction atmosphere medium during the reaction process of dehydrogenation of p-methylethylbenzene to synthesize p-methylstyrene.

[0021] The reactor for the dehydrogenation synthesis of p-methylstyrene by p-methylethylbenzene according to the present invention is a fixed-bed reactor, in which carbon dioxide or nitrobenzene and water are introduced simultaneously as a reaction atmosphere medium during the reaction process.

[0022] Preferably, the molar ratio of carbon dioxide, water and p-methylethylbenzene in the reaction atmosphere is 1:3:1-3:1.5:1; and the molar ratio of nitrobenzene, water and p-methylethylbenzene in the reaction atmosphere is 0.15:3:1-0.45:1.5:1.

[0023] Preferably, in the third technical solution described above, the pressure for the dehydrogenation reaction of p-methylethylbenzene is 0.05-0.20 MPa, the temperature is 600-680℃, and the reaction mass hourly space velocity (WHSV) is 0.5-1.5 h⁻¹. -1 .

[0024] The catalyst prepared by the above method was evaluated for activity in an isothermal fixed-bed reactor. The activity evaluation process for the catalyst in the dehydrogenation of p-methylethylbenzene to p-methylstyrene is as follows: Deionized water and carbon dioxide or nitrobenzene and p-methylethylbenzene are separately metered into a fixed-bed reactor. The reactor is heated by an electric resistance furnace to reach a predetermined temperature. The reactor is a stainless steel tube with an inner diameter of 12 mm. The reactants flowing out of the reactor are condensed in water and analyzed by gas chromatography.

[0025] The conversion rate of p-methylethylbenzene and the selectivity of methylstyrene are calculated using the following formula: p-Methylethylbenzene conversion rate % = (p-methylethylbenzene concentration before reaction % - p-methylethylbenzene concentration after reaction %) / p-methylethylbenzene concentration before reaction % Selectivity of p-methylstyrene % = Concentration of p-methylstyrene produced % / (Concentration of p-methylethylbenzene before reaction % - Concentration of p-methylethylbenzene after reaction %).

[0026] The technical solution of this invention has the following advantages: The catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene provided by this invention employs a two-component porogen mesoporous preparation method and an alkali metal Li-modified surface acidity / alkalinity method, as well as a reaction process method for controlling carbon deposition and by-products. This results in high dehydrogenation activity, high p-methylethylbenzene conversion, and good p-methylstyrene selectivity under low water-to-oil ratio operating conditions.

[0027] 1) One of the advantages is that the catalyst is prepared by using a polymer and bamboo fiber mixed pore-forming method, which makes the prepared catalyst have 2-5 nm pores, significantly increasing the pore volume and specific surface area, thereby enhancing reaction diffusion, exposing more effective catalytic active sites accessible to reactants, and also improving the catalyst's pore structure's resistance to carbon buildup and blockage.

[0028] 2) The second advantage is that the alkali metal lithium carbonate introduced by impregnation modifies the mesoporous surface, which completely eliminates residual acidic sites through small-sized alkaline ions, suppresses the side reactions of p-methylethylphenyl methyl methyl isomerization and p-methylethylphenyl cracking. Moreover, the lithium oxide loaded after calcination is beneficial to control the electron cloud density of iron element, which is beneficial to optimize the active center of catalyst surface.

[0029] 3) A third advantage is that the simultaneous introduction of carbon dioxide or nitrobenzene and water as the reaction atmosphere significantly enhances the catalyst activity and the selectivity for p-methylstyrene. Carbon dioxide reacts with the reaction byproduct hydrogen to generate carbon monoxide, shifting the dehydrogenation equilibrium of p-methylethylbenzene to the right and increasing its conversion rate. Simultaneously, carbon dioxide reacts with carbon deposits on the catalyst to generate carbon monoxide, which also inhibits deactivation of active sites and extends catalyst lifetime. The introduction of nitrobenzene also reacts with the byproduct hydrogen to form aniline, shifting the dehydrogenation equilibrium to the right and further increasing the conversion rate of p-methylethylbenzene.

[0030] The present invention will be further illustrated below through examples: Detailed Implementation Example 1 (Bamboo fiber + polyacrylamide two-component porous catalyst) 300g of iron oxide and 64g of potassium oxide were mixed with 38g of silica sol (17g based on silicon dioxide), 25g of bamboo fiber, and 22g of polyacrylamide to form a powder. 65g of cerium nitrate, 25g of lanthanum nitrate, 22g of ammonium molybdate, and 22g of copper nitrate were dissolved in 200g of deionized water to form a solution. This solution was then added to the powder mixture. The wet material was kneaded until it formed a dough-like consistency suitable for extrusion, then extruded and granulated. The mixture was then aged at room temperature for 24 hours, dried in an oven at 80℃ for 4 hours, and calcined in a muffle furnace at 600℃ for 4 hours to obtain a crude catalyst. The crude catalyst was impregnated in a solution of 21g of lithium carbonate and 250g of water for 2 hours, dried at 110℃ for 2 hours, and then calcined at 500℃ for 4 hours to obtain the final catalyst.

[0031] Catalytic reaction process 1: 10g of catalyst is loaded into a constant-temperature fixed-bed reactor and reacted at atmospheric pressure and a liquid hourly space velocity (LHSV) of 1.0 h⁻¹. -1 Activity was evaluated under reaction temperatures of 620℃ and 635℃, and a molar ratio of carbon dioxide, water, and p-methylethylbenzene of 3:1.5:1. Test results: at 620℃, the conversion rate of p-methylethylbenzene was 75.7% and the selectivity was 95.3%; at 635℃, the conversion rate was 77.1% and the selectivity was 92.5%.

[0032] Catalytic reaction process 2: 10g of catalyst is loaded into a constant-temperature fixed-bed reactor and reacted at atmospheric pressure and a liquid hourly space velocity (LHSV) of 1.0 h⁻¹. -1Activity was evaluated under the following conditions: reaction temperatures of 620℃ and 635℃, and a molar ratio of nitrobenzene, water, and p-methylethylbenzene of 0.35:1.5:1. Test results: at 620℃, the conversion rate of p-methylethylbenzene was 73.7% and the selectivity was 93.4%; at 635℃, the conversion rate was 74.1% and the selectivity was 91.7%.

[0033] Catalytic reaction process 3: 10 g of catalyst is loaded into a constant-temperature fixed-bed reactor and reacted at atmospheric pressure and a liquid hourly space velocity (LHSV) of 1.0 h⁻¹. -1 Activity was evaluated at reaction temperatures of 620℃ and 635℃, with a water-to-p-methylethylbenzene molar ratio of 1.5:1. Test results: at 620℃, the p-methylethylbenzene conversion was 67.5% and the selectivity was 92.4%; at 635℃, the p-methylethylbenzene conversion was 69.1% and the selectivity was 89.6%.

[0034] Through numerous experimental studies, it was found that in reaction processes without the participation of carbon dioxide and nitrobenzene mediators, the conversion rate of p-methylethylbenzene by the catalyst often fluctuates within a wide range, and the selectivity of p-methylstyrene also tends to deteriorate as the conversion rate decreases. This is mainly due to the influence of carbon deposits and byproduct hydrogen. To address this drawback, we introduced carbon dioxide or nitrobenzene mediators, which significantly improved the conversion rate of p-methylethylbenzene and stabilized it at a high level. The selectivity of p-methylstyrene was also slightly improved. This is mainly because carbon dioxide can react with carbon deposits to generate carbon monoxide, ensuring a clean environment for the reaction sites on the catalyst surface and effectively exposing the reactive sites. In addition, carbon dioxide and nitrobenzene can also react with byproduct hydrogen to generate carbon monoxide and aniline, shifting the reaction equilibrium to the right and improving the conversion rate of p-methylethylbenzene.

[0035] Example 2 (Guar powder + polyacrylamide two-component pore-forming catalyst) 350g of iron oxide and 64g of potassium oxide were mixed with 41g of aluminum sol (17g based on alumina), 25g of guar gum powder, and 22g of polyacrylamide to form a uniform powder. Then, 65g of cerium nitrate, 25g of lanthanum nitrate, 22g of ammonium molybdate, and 22g of copper nitrate were dissolved in 200g of deionized water to form a solution. This solution was then added to the powder mixture and kneaded until it formed a dough-like consistency suitable for extrusion. The mixture was then extruded, granulated, and aged at room temperature for 24 hours. After drying in an oven at 80°C for 4 hours, it was calcined in a muffle furnace at 800°C for 3 hours to obtain a crude catalyst. The crude catalyst was then impregnated with a solution of 21g of lithium carbonate and 250g of water for 2 hours, dried at 110°C for 2 hours, and then calcined at 600°C for 2 hours to obtain the final catalyst. The activity was evaluated according to the catalyst reaction process 1 in Example 1. Test results: at 620℃, the conversion rate of p-methylethylbenzene was 74.7% and the selectivity was 93.9%; at 635℃, the conversion rate of p-methylethylbenzene was 75.0% and the selectivity was 92.6%.

[0036] Example 3 (Catalyst with mixed pore-forming components and lithium carbonate-modified mesoporous structure) 325g of iron oxide and 64g of potassium oxide were mixed evenly with 17g of silicate cement, 25g of bamboo fiber, and 22g of polyacrylamide to form a powder. Then, 65g of cerium nitrate, 25g of lanthanum nitrate, 22g of ammonium molybdate, and 22g of copper nitrate were dissolved in 200g of deionized water to form a solution. This solution was then added to the powder mixture and kneaded until it formed a dough-like consistency suitable for extrusion. The mixture was then extruded, granulated, and aged at room temperature for 24 hours. It was then dried in an oven at 80°C for 4 hours and calcined in a muffle furnace at 500°C for 6 hours to obtain a crude catalyst. The crude catalyst was impregnated with a solution of 21g of lithium carbonate and 250g of water for 3 hours, dried at 110°C for 2 hours, and then calcined at 500°C for 4 hours to obtain the final catalyst. The activity was evaluated according to the catalyst reaction process 1 in Example 1. Test results: 75.9% conversion rate and 96.2% selectivity of p-methylethylbenzene at 620℃, and 76.9% conversion rate and 95.7% selectivity of p-methylethylbenzene at 635℃.

[0037] Comparative Example 1 This comparative example differs from Example 2 in that only 25g of guar gum powder was added as a porogen, no polyacrylamide was added, and the prepared catalyst was not impregnated with lithium carbonate solution. Activity was evaluated according to the catalyst reaction process 1 in Example 1. Test results: at 620℃, the conversion rate of p-methylethylbenzene was 57.9% and the selectivity was 89.1%; at 635℃, the conversion rate of p-methylethylbenzene was 58.30% and the selectivity was 86.5%.

[0038] Comparative Example 2 This comparative example differs from Example 2 in that the prepared catalyst was not impregnated with lithium carbonate solution. Activity was evaluated according to the catalyst reaction process 1 in Example 1. Test results: 60.1% conversion and 90.2% selectivity for p-methylethylbenzene at 620℃; 63.3% conversion and 87.9% selectivity for p-methylethylbenzene at 635℃.

[0039] Test case The weight percentage composition of the obtained catalyst is shown in Table 1, and the catalyst preparation method and activity evaluation results are shown in Table 2.

[0040] Table 1 shows the weight percentage composition of the obtained catalyst.

[0041] Table 2 Catalyst Preparation Methods and Activity Evaluation Table

[0042] The above embodiments illustrate that, on the one hand, the present invention significantly improves the catalyst's reactivity and selectivity for p-methylstyrene at low water ratios by adding at least three metals such as Mo, La, Cu, and Ba to the Fe-K-Ce catalyst system, introducing a two-component mixed pore-forming method, and combining this with lithium carbonate modification of the mesoporous surface. This significantly increases the conversion rate of p-methylethylbenzene and inhibits the occurrence of p-methylethylbenzene ethyl cracking and p-methylethylbenzene isomerization side reactions. On the other hand, by improving the reaction process, the stability of the catalyst is effectively improved, and the activity of the catalyst is enhanced to a certain extent.

[0043] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene, characterized in that, By weight percentage, the catalyst comprises the following components: 50%-70% iron oxide, 6%-15% potassium oxide, and 4%-13% cerium oxide; at least three of the following components: Co, Mo, Zr, Ba, Cu, Bi, and La, each with a content of 3%-10% as oxides; alkali metal lithium oxide modification introduced by impregnation, with a content of 1%-5% as oxides; the remainder being a binder; and mesoporous channels are introduced during catalyst forming by adding a pore-forming agent at a weight relative to the catalyst raw material of 5%-10% and then removing it by calcination.

2. The catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene according to claim 1, characterized in that, The porogen is composed of two components. One component is one of polyacrylic acid, polyacrylamide, and polyethylene glycol, used at 1%-5% of the catalyst raw material weight. The other component is one of guar gum powder and bamboo fiber, used at 3%-8% of the catalyst raw material weight. The catalyst prepared by the porogen forms 2-5 nm nanopores that are conducive to the reaction, with a pore volume of 0.30-0.60 ml / g and a specific surface area of ​​50-150 m². 2 / g.

3. The catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene according to claim 1, characterized in that, The introduction of at least three components, Co, Mo, Zr, Ba, Cu, Bi, and La, can be achieved by either a dry uniform mixing method with metal oxides or a method of calcination after impregnation with a metal salt solution.

4. The catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene according to claim 1, characterized in that, The adhesive is selected from any one of silicate cement, alumina sol and silica sol.

5. The catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene according to claim 1, characterized in that, The adhesive content by weight is 10%-30% in terms of oxides.

6. The method for preparing the catalyst for the dehydrogenation of p-methylethylbenzene to p-methylstyrene according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Mix iron oxide, potassium oxide, cerium salt or cerium oxide, at least three metal compounds selected from Co, Mo, Zr, Ba, Cu, Bi, La, a pore-forming agent and a binder evenly; The amount of pore-forming agent added is 5%-10% relative to the weight of the catalyst raw material. The pore-forming agent is a mixture composed of one of polyacrylic acid, polyacrylamide, and polyethylene glycol and one of guar gum powder and bamboo fiber. Optionally, one of polyacrylic acid, polyacrylamide, and polyethylene glycol accounts for 1%-5% of the weight of the catalyst raw material, and one of guar gum powder and bamboo fiber accounts for 3%-8% of the weight of the catalyst raw material. (2) Knead and extrude or compress the material from step (1) into tablets; (3) The shaped material is roasted at 500~800℃ for 2~6 hours; (4) Impregnate the catalyst precursor obtained in step (3) with a solution containing lithium compounds, then dry and calcine at 300~600℃ for 2~4 hours to obtain the final catalyst.

7. A process for the dehydrogenation of p-methylethylbenzene to produce p-methylstyrene, characterized in that, The catalyst prepared by any one of claims 1-5 or by the preparation method of claim 6 is used to simultaneously introduce carbon dioxide or nitrobenzene, along with water, as a reaction atmosphere medium during the dehydrogenation of p-methylethylbenzene to p-methylstyrene.

8. The process for producing p-methylstyrene by dehydrogenation of p-methylethylbenzene according to claim 7, characterized in that, The molar ratio of carbon dioxide, water, and p-methylethylbenzene in the reaction atmosphere is 1:3:1 to 3:1.5:

1.

9. The process for producing p-methylstyrene by dehydrogenation of p-methylethylbenzene according to claim 7, characterized in that, The molar ratio of nitrobenzene, water and p-methylethylbenzene in the reaction atmosphere is 0.15:3:1-0.45:1.5:

1.

10. The process for producing p-methylstyrene by dehydrogenation of p-methylethylbenzene according to claim 7, characterized in that, The dehydrogenation reaction of p-methylethylbenzene was carried out at a pressure of 0.05-0.20 MPa, a reaction temperature of 600-680 °C, and a WHSV of 0.5-1.5 h⁻¹. -1 .

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