Catalyst for preparing benzene through catalytic pyrolysis of toluene as well as preparation method and application of catalyst
By loading Pt, Pd, and rare earth metal additives onto a γ-Al2O3 support, the problems of low activity and poor selectivity of existing catalysts were solved, achieving efficient conversion of toluene to benzene and improving the stability of the catalyst and the conversion rate of toluene.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-24
- Publication Date
- 2026-04-07
AI Technical Summary
Existing catalysts for the catalytic pyrolysis of toluene to produce benzene suffer from low activity, poor selectivity, and insufficient stability, resulting in low toluene conversion, numerous byproducts, and increased production costs.
A catalyst was prepared using γ-Al2O3 as a support, Pt and Pd as active components, and rare earth metals as auxiliary agents. The catalyst was prepared through specific calcination, impregnation, and drying steps, and then subjected to the pyrolysis reaction of toluene in a fixed-bed reactor. Pretreatment and posttreatment were carried out by molecular sieve adsorption and pressure swing adsorption devices.
The process achieves efficient conversion of toluene to benzene, with high catalyst activity, good selectivity, and strong stability, reducing by-products and lowering production costs.
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of benzene preparation, and particularly relates to a catalyst for preparing benzene by catalytic pyrolysis of toluene as well as a preparation method and application thereof. BACKGROUND
[0002] Benzene is an important basic chemical raw material and is widely used in the fields of synthetic fibers, synthetic rubber, plastics, pesticides, medicines, dyes, and spices. At present, the catalytic pyrolysis of toluene to prepare benzene is one of the important ways to obtain benzene, but there are some problems in the existing catalytic technology and catalyst. For example, the activity of some catalysts is relatively low, resulting in a low conversion rate of toluene; the selectivity of some catalysts is insufficient, which will produce more by-products, affecting the purity and yield of benzene; and the stability of some catalysts is poor, with a short service life, which needs to be frequently replaced, increasing the production cost and equipment maintenance difficulty. Therefore, it is of important practical significance to develop a catalyst for the catalytic pyrolysis of toluene to prepare benzene with high activity, high selectivity, and high stability and the corresponding catalytic technology. SUMMARY
[0003] In view of the defects of the prior art, the application provides a catalyst for preparing benzene by catalytic pyrolysis of toluene as well as a preparation method and application thereof, so as to solve the problems of low catalyst activity and poor selectivity in the process of preparing benzene by catalytic pyrolysis of toluene in the prior art and realize efficient conversion of toluene to benzene.
[0004] A catalyst for preparing benzene by catalytic pyrolysis of toluene, the catalyst comprising a carrier, an active component supported on the carrier, and an additive, the active component being Pt and Pd, the additive being a rare earth metal, the carrier being γ-Al2O3, the content of each component in the catalyst being as follows: Pt 0.5-2%, Pd 0.3-1.5%, additive 0.1-0.5%, and the balance being the carrier.
[0005] Preferably, the additive is at least one of Ce, La, Pr, and Nd.
[0006] Preferably, the specific surface area of the γ-Al2O3 is 200-300 m 2 / g, and the pore volume is 0.4-0.6 cm 3 / g.
[0007] The preparation method of the catalyst for preparing benzene by catalytic pyrolysis of toluene comprises the following steps: (1) calcining the carrier and cooling to room temperature; (2) dissolving chloroplatinic acid hexahydrate and palladium chloride in water to obtain an impregnation solution, immersing the carrier obtained in step (1) in the impregnation solution, stirring at room temperature for 12-24 h, drying, calcining, and cooling to room temperature; (3) dissolving a rare earth metal nitrate in water, adding the product of step (2) into the solution, impregnating for 6-8 h, drying, and calcining to obtain the catalyst.
[0008] Preferably, in step (1), the calcining is performed at 500-600 ℃ for 4-6 h.
[0009] Preferably, in step (2), the drying is performed at 100-120 ℃ for 6-8 h, and the calcining is performed at 400-500 ℃ for 3-5 h.
[0010] Preferably, in step (3), the drying is performed at 100-120 ℃ for 4-6 h, and the calcining is performed at 350-450 ℃ for 2-4 h.
[0011] Preferably, in step (3), the impregnating is performed by equal volume impregnation.
[0012] A method for preparing benzene by catalytic pyrolysis of toluene: loading the catalyst into a fixed bed reactor, mixing toluene and nitrogen gas in a volume ratio of 1: (3-4), and then feeding into the fixed bed reactor, and performing pyrolysis reaction under the conditions of a reaction temperature of 450-550 ℃ and a reaction pressure of 0.1-0.5 MPa, and then separating the reaction product by post-treatment to obtain benzene; wherein the mass space velocity of toluene is 1-3 h -1 , and the catalyst is the catalyst described in the present application.
[0013] Preferably, the toluene needs to be pretreated before being fed into the fixed bed reactor, and the pretreatment is performed by a molecular sieve adsorption column; the molecular sieve adsorption column is used for dehydration and desulfurization, and the impurities in the toluene are removed, the purity of the raw material is improved, and the damage to the catalyst is reduced.
[0014] Preferably, the post-treatment separation is performed as follows: the reaction product is condensed, the liquid product obtained by condensation is subjected to rectification to obtain benzene, and the gaseous product that is not condensed is compressed and then passed through a pressure swing adsorption device to recover toluene therein for standby use.
[0015] Advantages of the present application: The catalyst provided by the present application is used in the reaction of preparing benzene by catalytic pyrolysis of toluene, has high catalytic activity, high selectivity of toluene, and good stability, and can realize efficient conversion of toluene to benzene. DETAILED DESCRIPTION
[0016] Example 1 A catalyst for preparing benzene by catalytic pyrolysis of toluene, the catalyst comprising a carrier γ-Al2O3, an active component supported on the carrier and an auxiliary agent, the active component being Pt and Pd, the auxiliary agent being a rare earth metal Ce, the mass of the catalyst being 100%, the content of each component being as follows: Pt 0.5%, Pd 0.3%, auxiliary agent 0.1%, the balance being the carrier; the specific surface area of the γ-Al2O3 being 200 m 2 / g, the pore volume being 0.4 cm 3 / g. A preparation method of the catalyst for preparing benzene by catalytic pyrolysis of toluene, comprising the following steps: (1) calcining 100 g of the carrier at 500 ℃ for 5 h and cooling to room temperature; (2) dissolving 1.28 g of chloroplatinic acid hexahydrate H2PtCl6·6H2O and 0.50 g of palladium chloride PdCl2 in water to obtain an impregnation solution, immersing the carrier obtained in step (1) in the impregnation solution, stirring at room temperature for 18 h, drying at 110 ℃ for 7 h and calcining at 450 ℃ for 4 h, and cooling to room temperature; (3) dissolving 0.31 g of Ce (NO3)3·6H2O in water, adding the product of step (2) thereto, impregnating by equal volume for 7 h, drying at 110 ℃ for 5 h and calcining at 400 ℃ for 3 h to obtain the catalyst.
[0017] Example 2 A catalyst for preparing benzene by catalytic pyrolysis of toluene, the catalyst comprising a carrier γ-Al2O3, an active component supported on the carrier and an auxiliary agent, the active component being Pt and Pd, the auxiliary agent being a rare earth metal Ce, the mass of the catalyst being 100%, the content of each component being as follows: Pt 2.0%, Pd 1.5%, auxiliary agent 0.5%, the balance being the carrier; the specific surface area of the γ-Al2O3 being 200 m 2 / g, the pore volume being 0.4 cm 3 / g. A preparation method of the catalyst for preparing benzene by catalytic pyrolysis of toluene, comprising the following steps: (1) calcining 100 g of the carrier at 600 ℃ for 4 h and cooling to room temperature; (2) dissolving 5.14 g of chloroplatinic acid hexahydrate H2PtCl6·6H2O and 2.5 g of palladium chloride PdCl2 in water to obtain an impregnation solution, immersing the carrier obtained in step (1) in the impregnation solution, stirring at room temperature for 20 h, drying at 120 ℃ for 6 h and calcining at 480 ℃ for 3.5 h, and cooling to room temperature; (3) 1.55 g Ce (NO3)3·6H2O was dissolved in water, the product of step (2) was added thereto, impregnated with equal volume for 8 h, dried at 120 ℃ for 4 h, and calcined at 420 ℃ for 2.5 h to obtain the catalyst.
[0018] Example 3 A catalyst for catalytic pyrolysis of toluene to prepare benzene, the catalyst comprising a carrier γ-Al2O3, an active component supported on the carrier, and an auxiliary agent, the active component being Pt and Pd, the auxiliary agent being a rare earth metal Ce, the content of each component in the catalyst being as follows: Pt 0.5%, Pd 1.5%, auxiliary agent 0.3%, and the balance being the carrier, the specific surface area of the γ-Al2O3 being 300 m 2 / g, and the pore volume being 0.6 cm 3 / g; and a preparation method of the catalyst for catalytic pyrolysis of toluene to prepare benzene, comprising the following steps: (1) the carrier 100 g was calcined at 500 ℃ for 6 h and cooled to room temperature; (2) 1.28 g of chloroplatinic acid hexahydrate H2PtCl6·6H2O and 2.50 g of palladium chloride PdCl2 were dissolved in water to obtain an impregnation solution, the carrier obtained in step (1) was immersed in the impregnation solution, stirred at room temperature for 12 h, dried at 100 ℃ for 8 h, and calcined at 500 ℃ for 3 h and cooled to room temperature; (3) 0.93 g Ce (NO3)3·6H2O was dissolved in water, the product of step (2) was added thereto, impregnated with equal volume for 6 h, dried at 100 ℃ for 6 h, and calcined at 350 ℃ for 4 h to obtain the catalyst.
[0019] Example 4 A catalyst for catalytic pyrolysis of toluene to prepare benzene, the catalyst comprising a carrier γ-Al2O3, an active component supported on the carrier, and an auxiliary agent, the active component being Pt and Pd, the auxiliary agent being a rare earth metal Ce, the content of each component in the catalyst being as follows: Pt 2.0%, Pd 0.3%, auxiliary agent 0.2%, and the balance being the carrier, the specific surface area of the γ-Al2O3 being 300 m 2 / g, and the pore volume being 0.6 cm 3 / g; A preparation method of the catalyst for catalytic pyrolysis of toluene to prepare benzene, comprising the following steps: (1) the carrier 100 g was calcined at 550 ℃ for 5 h and cooled to room temperature; (2) 5.14 g of hexahydrate chloroplatinic acid H2PtCl6.6H2O and 0.50 g of palladium chloride PdCl2 are dissolved in water to obtain an impregnation solution, the carrier obtained in step (1) is immersed therein, stirred at room temperature for 24 h, dried at 110°C for 7 h, and calcined at 400°C for 5 h, and then cooled to room temperature; (3) 0.62 g of Ce (NO3)3.6H2O is dissolved in water, and the product of step (2) is added thereto, impregnated in equal volume for 6 h, dried at 110°C for 5 h, and calcined at 450°C for 2 h to obtain the catalyst.
[0020] Example 5 A catalyst for catalytic pyrolysis of toluene to produce benzene, which comprises a carrier γ-Al2O3, an active component supported on the carrier, and an auxiliary agent, the active component being Pt and Pd, and the auxiliary agent being a rare earth metal La, the content of each component in the catalyst being as follows: Pt 1.0%, Pd 0.9%, auxiliary agent 0.3%, and the balance being the carrier, the specific surface area of the γ-Al2O3 being 300 m 2 / g, and the pore volume being 0.6 cm 3 / g. A preparation method of the catalyst for catalytic pyrolysis of toluene to produce benzene, which comprises the following steps: (1) The carrier 100 g is calcined at 550°C for 5 h, and then cooled to room temperature; (2) 2.56 g of hexahydrate chloroplatinic acid H2PtCl6.6H2O and 1.50 g of palladium chloride PdCl2 are dissolved in water to obtain an impregnation solution, the carrier obtained in step (1) is immersed therein, stirred at room temperature for 24 h, dried at 110°C for 7 h, and calcined at 400°C for 5 h, and then cooled to room temperature; (3) 0.94 g of La (NO3)3.6H2O is dissolved in water, and the product of step (2) is added thereto, impregnated in equal volume for 6 h, dried at 110°C for 5 h, and calcined at 450°C for 2 h to obtain the catalyst.
[0021] Example 6 A catalyst for catalytic pyrolysis of toluene to produce benzene, which comprises a carrier γ-Al2O3, an active component supported on the carrier, and an auxiliary agent, the active component being Pt and Pd, and the auxiliary agent being a rare earth metal Pr, the content of each component in the catalyst being as follows: Pt 1.0%, Pd 0.9%, auxiliary agent 0.3%, and the balance being the carrier, the specific surface area of the γ-Al2O3 being 300 m 2 / g, and the pore volume being 0.6 cm 3 / g. The preparation method of the catalyst for preparing benzene by catalytic pyrolysis of toluene comprises the following steps: (1) calcining the carrier 100 g at 550 DEG C for 5 h and cooling to room temperature; (2) dissolving 2.56 g of hexahydrate chloroplatinic acid H2PtCl6 6H2O and 1.50 g of palladium chloride PdCl2 in water to obtain an impregnation solution, immersing the carrier obtained in step (1) in the impregnation solution, stirring at room temperature for 24 h, drying at 110 DEG C for 7 h, and calcining at 400 DEG C for 5 h and cooling to room temperature; (3) dissolving 0.93 g of Pr (NO3)3 6H2O in water, adding the product of step (2) to the water, impregnating by equal volume for 6 h, drying at 110 DEG C for 5 h, and calcining at 450 DEG C for 2 h to obtain the catalyst.
[0022] Example 7 A catalyst for preparing benzene by catalytic pyrolysis of toluene, the catalyst comprising a carrier γ-Al2O3, an active component supported on the carrier, and an additive, the active component being Pt and Pd, and the additive being a rare earth metal Nd, the mass of the catalyst being 100%, the content of each component being as follows: Pt 1.0%, Pd 0.9%, additive 0.3%, and the balance being the carrier; the specific surface area of the γ-Al2O3 being 300 m 2 / g, and the pore volume being 0.6 cm 3 / g. The preparation method of the catalyst for preparing benzene by catalytic pyrolysis of toluene comprises the following steps: (1) calcining the carrier 100 g at 550 DEG C for 5 h and cooling to room temperature; (2) dissolving 2.56 g of hexahydrate chloroplatinic acid H2PtCl6 6H2O and 1.50 g of palladium chloride PdCl2 in water to obtain an impregnation solution, immersing the carrier obtained in step (1) in the impregnation solution, stirring at room temperature for 24 h, drying at 110 DEG C for 7 h, and calcining at 400 DEG C for 5 h and cooling to room temperature; (3) dissolving 0.91 g of Nd (NO3)3 6H2O in water, adding the product of step (2) to the water, impregnating by equal volume for 6 h, drying at 110 DEG C for 5 h, and calcining at 450 DEG C for 2 h to obtain the catalyst.
[0023] Example 8 A catalyst for preparing benzene by catalytic pyrolysis of toluene, the catalyst comprising a carrier γ-Al2O3, an active component supported on the carrier, and an auxiliary agent, the active component being Pt and Pd, the auxiliary agent being a rare earth metal Ce, the content of each component in the catalyst being as follows: Pt 0.7%, Pd 0.5%, auxiliary agent 0.2%, and the balance being the carrier, the specific surface area of the γ-Al2O3 being 300 m 2 / g, and the pore volume being 0.6 cm 3 / g. A preparation method of the catalyst for preparing benzene by catalytic pyrolysis of toluene, comprising the following steps: (1) calcining 100 g of the carrier at 550 ℃ for 5 h and cooling to room temperature; (2) dissolving 1.79 g of chloroplatinic acid hexahydrate H2PtCl6·6H2O and 0.83 g of palladium chloride PdCl2 in water to obtain an impregnation solution, immersing the carrier obtained in step (1) in the impregnation solution, stirring at room temperature for 18 h, drying at 110 ℃ for 7 h, and calcining at 450 ℃ for 5 h to obtain the catalyst. (3) dissolving 0.62 g of Ce (NO3)3·6H2O in water, adding the product of step (2) thereto, impregnating by equal volume for 6 h, drying at 110 ℃ for 5 h, and calcining at 450 ℃ for 2 h to obtain the catalyst.
[0024] Comparative Example 1 A comparative catalyst, the catalyst comprising a carrier γ-Al2O3, an active component supported on the carrier, the active component being Pt, the content of each component in the catalyst being as follows: Pt 1.0%, and the balance being the carrier, the specific surface area of the γ-Al2O3 being 300 m 2 / g, and the pore volume being 0.6 cm 3 / g. A preparation method of the catalyst for preparing benzene by catalytic pyrolysis of toluene, comprising the following steps: (1) calcining 100 g of the carrier at 550 ℃ for 5 h and cooling to room temperature; (2) dissolving 2.56 g of chloroplatinic acid hexahydrate H2PtCl6·6H2O in water to obtain an impregnation solution, immersing the carrier obtained in step (1) in the impregnation solution, stirring at room temperature for 24 h, drying at 110 ℃ for 7 h, and calcining at 400 ℃ for 5 h to obtain the catalyst.
[0025] Comparative Example 2 A comparative catalyst, the catalyst comprising a carrier γ-Al2O3, an active component supported on the carrier, the active component being Pd, no rare earth assistant, the content of each component being as follows: Pd 0.9 %, the balance being the carrier; the specific surface area of the γ-Al2O3 being 300 m 2 / g, the pore volume being 0.6 cm 3 / g; a preparation method of the catalyst for preparing benzene by catalytic pyrolysis of toluene, comprising the following steps: (1) calcining 100 g of the carrier at 550 ℃ for 5 h, and cooling to room temperature; (2) dissolving 1.50 g of palladium chloride PdCl2 in water to obtain an impregnation solution, immersing the carrier obtained in step (1) in the impregnation solution, stirring at room temperature for 24 h, drying at 110 ℃ for 7 h, and calcining at 400 ℃ for 5 h to obtain the catalyst.
[0026] Comparative Example 3 A comparative catalyst, the catalyst comprising a carrier γ-Al2O3, an active component supported on the carrier, the active component being Pd, no rare earth assistant, the content of each component being as follows: Pt 1.0 %, Pd 0.9 %, the balance being the carrier; the specific surface area of the γ-Al2O3 being 300 m 2 / g, the pore volume being 0.6 cm 3 / g; a preparation method of the catalyst for preparing benzene by catalytic pyrolysis of toluene, comprising the following steps: (1) calcining 100 g of the carrier at 550 ℃ for 5 h, and cooling to room temperature; (2) dissolving 2.56 g of hexahydrate chloroplatinic acid H2PtCl6·6H2O and 1.50 g of palladium chloride PdCl2 in water to obtain an impregnation solution, immersing the carrier obtained in step (1) in the impregnation solution, stirring at room temperature for 24 h, drying at 110 ℃ for 7 h, and calcining at 400 ℃ for 5 h to obtain the catalyst.
[0027] Catalytic performance detection The catalyst is filled into a fixed bed reactor, toluene is removed by a molecular sieve adsorption column, then the pretreated toluene is mixed with nitrogen in a volume ratio of 1: (3-4), and then is introduced into the fixed bed reactor, a pyrolysis reaction is carried out under the conditions of a reaction temperature of 450-550 ℃ and a reaction pressure of 0.1-0.5 MPa, the reaction product is condensed, the liquid product obtained by condensation is subjected to rectification to obtain benzene, and the gaseous product not condensed is compressed and then is recovered by a pressure swing adsorption device to obtain toluene for reuse; wherein the mass space velocity of toluene is 1-3 h -1 , and the specific reaction conditions and results are shown in Table 1. Table 1 Reaction conditions and reaction results 。
Claims
1. A catalyst for the catalytic pyrolysis of toluene to produce benzene, characterized in that: The catalyst comprises a support, an active component supported on the support, and an auxiliary agent. The active component is Pt and Pd, the auxiliary agent is a rare earth metal, and the support is γ-Al2O3. The mass of the catalyst is calculated as 100%, and the content of each component is as follows: Pt 0.5-2%, Pd 0.3-1.5%, auxiliary agent 0.1-0.5%, and the balance is the support.
2. The catalyst for the catalytic pyrolysis of toluene to benzene according to claim 1, characterized in that: The auxiliary agent is at least one of Ce, La, Pr, and Nd.
3. The catalyst for the catalytic pyrolysis of toluene to produce benzene according to claim 1, characterized in that: The specific surface area of the γ-Al2O3 is 200-300 m². 2 / g, pore volume 0.4-0.6cm 3 / g.
4. The method for preparing the catalyst for the catalytic pyrolysis of toluene to benzene according to claim 1, characterized in that: Includes the following steps: (1) The carrier is calcined and cooled to room temperature; (2) Dissolve chloroplatinic acid hexahydrate and palladium chloride in water to obtain an impregnation solution. Immerse the carrier obtained in step (1) in the solution, stir at room temperature for 12-24 hours, dry, calcine, and cool to room temperature. (3) Dissolve rare earth metal nitrates in water, add the product from step (2) to it, soak for 6-8 hours, dry, and calcine to obtain the catalyst.
5. The method for preparing the catalyst for the catalytic pyrolysis of toluene to benzene according to claim 4, characterized in that: In step (1), the calcination conditions are calcination at 500-600℃ for 4-6 hours.
6. The method for preparing the catalyst for the catalytic pyrolysis of toluene to benzene according to claim 4, characterized in that: In step (2), the drying conditions are drying at 100-120℃ for 6-8 hours; the calcination conditions are calcination at 400-500℃ for 3-5 hours.
7. The method for preparing the catalyst for the catalytic pyrolysis of toluene to benzene according to claim 4, characterized in that: In step (3), the drying conditions are drying at 100-120℃ for 4-6 hours; the calcination conditions are calcination at 350-450℃ for 2-4 hours; and the impregnation in step (3) is equal volume impregnation.
8. A method for producing benzene by catalytic pyrolysis of toluene, characterized in that: The catalyst was loaded into a fixed-bed reactor. Toluene and nitrogen were mixed at a volume ratio of 1:(3-4) and then introduced into the fixed-bed reactor. The pyrolysis reaction was carried out at a reaction temperature of 450-550℃ and a reaction pressure of 0.1-0.5MPa. The reaction products were post-processed and separated to obtain benzene. The mass hourly space velocity (WHSV) of toluene was 1-3 h⁻¹. -1 The catalyst is the catalyst described in claim 1, 2 or 3.
9. The method for producing benzene by catalytic pyrolysis of toluene according to claim 8, characterized in that: Before the toluene is introduced into the fixed-bed reactor, it needs to undergo pretreatment, which involves removing impurities by passing it through a molecular sieve adsorption column.
10. The method for producing benzene by catalytic pyrolysis of toluene according to claim 8, characterized in that: The post-processing separation is as follows: the reaction product is condensed, the liquid product obtained by condensation is distilled to obtain benzene, and the uncondensed gaseous product is compressed and then subjected to a pressure swing adsorption device to recover toluene for later use.