A process and catalyst for the preparation of benzene by co-feeding of acetylene and ethylene to aromatization

Abstract

The application discloses a method for preparing benzene by acetylene and ethylene co-feeding aromatization, by introducing a certain proportion of ethylene raw material in an acetylene atmosphere, ethylene as a reaction intermediate can promote the acetylene benzene preparation reaction, and the selectivity of the target product benzene is improved. The method has the characteristics of high acetylene conversion rate and high benzene selectivity in the product. The application also discloses a supported transition metal composite catalyst, which can improve the acetylene conversion rate and the benzene selectivity of the reaction to a relatively ideal level in combination with the foregoing method, and the operation is simple, the conditions are relatively mild, the industrial application requirements can be met, and large-scale industrial production is facilitated.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering and relates to a method and catalyst for the aromatization of acetylene and ethylene as co-feeds to prepare benzene. Background Technology

[0002] Light aromatic hydrocarbons such as benzene, toluene, and xylene are widely used as basic chemical raw materials in the production of chemical products such as rubber, fibers, plastics, and dyes. In recent years, with the rapid development of synthetic materials and the increasing demand for other fine chemicals, the demand for aromatic hydrocarbons has continued to rise. Currently, aromatic hydrocarbons mainly originate from catalytic reforming and hydrocarbon cracking in the petrochemical industry. The scarcity of petroleum resources makes the development of new technologies urgent. If acyclic simple molecules, such as methane, methanol, and acetylene, could be used to undergo aromatization reactions to directly transform them into high-value-added light aromatic hydrocarbons, it would open up new avenues for aromatic hydrocarbon production.

[0003] Acetylene is highly reactive, and its cyclotrimerization reaction is strongly exothermic. However, without a catalyst, the reaction at 400°C produces only a very small amount of benzene due to numerous side reactions. Reppe et al. (Ann. Chem. 1948, 560, 104) first reported a NiBr2 catalyst in 1948, which enabled the synthesis of various substituted benzene derivatives from the cyclotrimerization of alkynes using homogeneous catalysis. Since then, the aromatization of alkynes has attracted widespread attention from researchers both domestically and internationally, and many transition metals and their complexes have been found to catalyze the aromatization of acetylene.

[0004] Elsternwick et al. (USP 4424401) disclosed the acetylene aromatization reaction performance on the surface of the zeolite catalyst ZSM-5: ZSM-5 molecular sieves can catalyze this reaction well in the presence of inert gas, water, hydrogen, and alcohol, over a wide temperature range of 260-550 °C, but are highly susceptible to deactivation. Timmons et al. (USP 5118893) disclosed the acetylene aromatization reaction on the surface of a Ni- and Co-modified ZSM-5 catalyst in the presence of H2O and H2. The results showed that the reaction stability was improved to some extent, but the aromatic selectivity decreased.

[0005] Xu Lei et al. (CN105498757A) reported a supported, highly dispersed palladium-ruthenium-rhodium transition metal composite catalyst that achieved an acetylene conversion rate of over 90% and a benzene selectivity of over 70%, but the reaction stability was poor. Huang Wei et al. (CN107042120A) reported a modified supported palladium catalyst that also exhibited high acetylene conversion and benzene selectivity during the reaction, but conversion and selectivity were often not simultaneously achieved, and stability still needs improvement. Xu Li et al. (CN105498759A) disclosed a supported palladium-ruthenium-rhodium transition metal composite catalyst that achieved a 100% acetylene conversion rate and a benzene selectivity greater than 80%.

[0006] Therefore, most of the currently available optimization methods for acetylene aromatization reactions focus on catalysts, which still suffers from the drawback of sacrificing either acetylene conversion or benzene selectivity. As mentioned earlier, acetylene molecules are highly reactive, which leads to deep polymerization during the reaction, resulting in decreased benzene selectivity and thus limiting the industrial application of this reaction to some extent. Summary of the Invention

[0007] The technical problem to be solved by this invention is to provide a method and catalyst for the aromatization of acetylene and ethylene as co-feeds to prepare benzene. In particular, it can stably maintain 100% acetylene conversion and high benzene selectivity for a relatively long period of time.

[0008] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0009] This invention provides a method for preparing benzene by aromatization of acetylene and ethylene as co-feeds, wherein material components containing ethylene and acetylene, along with nitrogen gas, are introduced into a reactor to contact with a catalyst for an aromatization reaction.

[0010] Furthermore, the volume ratio of ethylene to acetylene in the material component is 0.01-0.2, for example, it can be 0.01, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15 or 0.2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0011] Furthermore, the aromatization reaction is carried out at a temperature of 400-600℃ and an acetylene volume hourly space velocity of 500-3000 h⁻¹. -1 .

[0012] Furthermore, before the aromatization reaction, the catalyst is pretreated in situ at 500-600°C in a hydrogen atmosphere on the reaction apparatus for 1-3 h to reduce the active component to a metallic state.

[0013] The present invention also provides a catalyst used in the above method, which belongs to a supported transition metal composite catalyst, comprising a support and an active component.

[0014] Furthermore, the supported transition metal composite catalyst is prepared by room temperature equal volume impregnation method; the support is at least one of macroporous silica gel, MCM-41, and SBA-15; and the active component is ruthenium, rhodium, palladium, and zinc.

[0015] Furthermore, the palladium loading on the supported transition metal composite catalyst is 0.2-1.5% of the palladium mass as the carrier, the ruthenium loading is 0.2-1.5% of the ruthenium mass as the carrier, the rhodium loading is 0.2-1.5% of the rhodium mass as the carrier, and the zinc loading is 0.2-1.0% of the zinc mass as the carrier.

[0016] Furthermore, the preparation method of the supported transition metal composite catalyst includes the following steps:

[0017] S1. The calcined pretreated support was impregnated in an equal volume of palladium salt aqueous solution of different concentrations, dried, and calcined to obtain a supported palladium catalyst;

[0018] S2. The supported palladium catalyst obtained in step S1 is impregnated in an equal volume of ruthenium and rhodium salt aqueous solution, dried and calcined to obtain a supported ruthenium, rhodium and palladium catalyst;

[0019] S3. The supported ruthenium, rhodium, and palladium composite catalyst obtained in step S2 is impregnated in an equal volume into a zinc salt aqueous solution, dried, and calcined to obtain the supported ruthenium, rhodium, palladium, and zinc catalyst, namely the supported transition metal composite catalyst.

[0020] Furthermore, the palladium salt is PdCl2; the ruthenium salt is RuCl3; the rhodium salt is RhCl3; and the zinc salt is Zn(NO3)2.

[0021] Furthermore, the time for the equal-volume impregnation is 6-12 h; the drying temperature is 110-150℃; and the calcination is carried out in an air atmosphere by heating at 10℃ / min to 500-600℃ for 2-4 h.

[0022] The present invention has the following beneficial effects:

[0023] The method and catalyst for preparing benzene by co-feeding acetylene and ethylene provided by this invention introduce ethylene into the acetylene aromatization reaction feed components and zinc, an ethylene aromatization component, into the composition of existing acetylene aromatization reaction catalysts. On the one hand, ethylene, as an intermediate product in the acetylene aromatization reaction process, is more easily aromatized, thus having a better promoting effect on the original reaction and obtaining better results. On the other hand, the presence of ethylene has a diluting effect on acetylene, which is beneficial to suppressing the occurrence of polymerization side reactions between acetylene molecules.

[0024] The method and catalyst for preparing benzene by co-feeding acetylene and ethylene provided by this invention have the characteristics of high acetylene conversion rate and high selectivity of benzene in the product.

[0025] The method and catalyst for the aromatization of acetylene and ethylene as co-feeds provided by this invention are simple to operate, have relatively mild conditions, meet the requirements of industrial applications, and are easy to carry out large-scale industrial production. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the embodiments. These embodiments are merely preferred implementations of the present invention and are not intended to limit the invention. They should not be construed as limiting the scope of the invention to the following embodiments. All technologies implemented based on the content of this invention fall within the scope of protection of this invention. Unless otherwise specified, the reagents, equipment, and methods used in this invention are commercially available and conventionally used in this technical field.

[0027] Example 1

[0028] This embodiment provides the preparation of a Pd / Ru / Rh / SiO2 catalyst.

[0029] Macroporous silica gel (SiO2) was calcined at 550 °C for 6 h in air and then cooled to room temperature. 50 g of the calcined macroporous silica gel support was weighed and added in equal volume to a PdCl2 aqueous solution. The PdCl2 loading was denoted as 0.6% of the Pd mass of the macroporous silica gel. The sample was impregnated at room temperature for 6 h. After impregnation, the sample was dried at 110 °C and then calcined at 500 °C for 3 h in air at a rate of 10 °C / min to obtain the macroporous silica gel-supported Pd / SiO2 catalyst, denoted as Pd(0.6) / SiO2.

[0030] Then, an equal volume of the catalyst was added to a mixed aqueous solution of RuCl3 and RhCl3, with the loading amounts of RuCl3 and RhCl3 denoted as 0.3% and 1.2% of the macroporous silica gel by mass of Ru and Rh, respectively. The mixture was impregnated at room temperature for 10 h. The resulting mixture was dried at 110 ℃ and then calcined in air at a rate of 10 ℃ / min to 500 ℃ for 5 h to obtain the macroporous silica gel-supported composite Pd / Ru / Rh / SiO2 catalyst, denoted as Pd(0.6)Ru(0.3)Rh(1.2) / SiO2. After tableting, crushing, and sieving to 20-40 mesh, it was ready for use.

[0031] Example 2

[0032] This embodiment provides the preparation of a Zn / Pd / Ru / Rh / MCM-41 catalyst.

[0033] MCM-41 was calcined at 550 °C for 6 h in air and then cooled to room temperature. 50 g of the calcined MCM-41 support was weighed and an equal volume of PdCl2 aqueous solution was added for impregnation. The PdCl2 loading was denoted as 0.6% of the MCM-41 mass by weight of Pd. The resulting aqueous solution was then impregnated at room temperature for 6 h. The resulting mixture was dried at 110 °C and then calcined at 500 °C for 3 h in air at a rate of 10 °C / min to obtain the MCM-41-supported Pd / MCM-41 catalyst, denoted as Pd(0.6) / MCM-41. Then, an equal volume of this sample was impregnated in a mixed aqueous solution of RuCl3 and RhCl3. The RuCl3 and RhCl3 loadings were denoted as 0.3% and 1.2% of the MCM-41 mass by weight of Ru and Rh, respectively. The resulting aqueous solution was then impregnated at room temperature for 10 h. The resulting mixture was dried at 110 °C and then calcined in air at 10 °C / min to 500 °C for 5 h to obtain the MCM-41-supported composite Pd / Ru / Rh / MCM-41 catalyst, denoted as Pd(0.6)Ru(0.3)Rh(1.2) / MCM-41. Finally, an equal volume of this sample was impregnated with a Zn(NO3)2 aqueous solution, with the Zn(NO3)2 loading amount recorded as 0.4% of the Zn mass of MCM-41. The solution was prepared and impregnated at room temperature for 6 h. The resulting mixture was dried at 110 °C and then calcined in air at 10 °C / min to 500 °C for 3 h to obtain the MCM-41-supported composite Zn / Pd / Ru / Rh / MCM-41 catalyst, denoted as Pd(0.6)Ru(0.3)Rh(1.2)Zn(0.4) / MCM-41. After being tableted, crushed, and sieved to 20-40 mesh, it is ready for use.

[0034] Example 3

[0035] This embodiment provides the preparation of a Zn / Pd / Ru / Rh / SBA-15 catalyst.

[0036] SBA-15 was calcined at 550 °C for 6 h in air and then cooled to room temperature. 50 g of the calcined SBA-15 support was weighed and an equal volume of PdCl2 aqueous solution was added for impregnation. The PdCl2 loading was denoted as 0.8% of the SBA-15 mass by Pd. After preparing the aqueous solution, impregnation was carried out at room temperature for 12 h. The resulting mixture was dried at 110 °C and then calcined at 500 °C for 3 h in air at a rate of 10 °C / min to obtain the SBA-15 supported Pd / SBA-15 catalyst, denoted as Pd(0.8) / SBA-15. Then, an equal volume of this sample was impregnated in a mixed aqueous solution of RuCl3 and RhCl3. The RuCl3 and RhCl3 loadings were denoted as 0.4% and 1.2% of the SBA-15 mass by Ru and Rh, respectively. After preparing the aqueous solution, impregnation was carried out at room temperature for 6 h. The resulting mixture was dried at 110 °C and then calcined in air at 10 °C / min to 500 °C for 5 h to obtain the SBA-15 supported composite Pd / Ru / Rh / SBA-15 catalyst, denoted as Pd(0.8)Ru(0.4)Rh(1.2) / SBA-15. Finally, an equal volume of this sample was impregnated with a Zn(NO3)2 aqueous solution, with the Zn(NO3)2 loading amount recorded as 0.6% of the Zn mass of SBA-15. The solution was prepared and impregnated at room temperature for 6 h. The resulting mixture was dried at 110 °C and then calcined in air at 10 °C / min to 500 °C for 3 h to obtain the SBA-15 supported composite Zn / Pd / Ru / Rh / SBA-15 catalyst, denoted as Pd(0.8)Ru(0.4)Rh(1.2)Zn(0.6) / SBA-15. After being tableted, crushed, and sieved to 20-40 mesh, it is ready for use.

[0037] Comparative Example 1

[0038] This comparative example provides an evaluation of the reaction of the Pd(0.6)Ru(0.3)Rh(1.2) / SiO2 catalyst with acetylene as the sole feedstock.

[0039] The acetylene aromatization reaction was carried out in a fixed-bed reactor using a stainless steel reactor with an inner diameter of 10 mm and a reaction pressure of atmospheric pressure. 2 g of Pd(0.6)Ru(0.3)Rh(1.2) / SiO2 prepared in Example 1 was added to the reactor, and the temperature was increased to 500 °C at 10 °C / min and maintained for 2 h in a hydrogen atmosphere. After reduction, the atmosphere was switched to N2 for purging for 1 h, and then the temperature was increased to 550 °C before introducing a reaction gas of 10% C2H2 + 90% N2 (volume composition) at a gas hourly space velocity of 600 h⁻¹. -1 In the experiment, the gas flow rate was controlled by a mass flow meter, and the reaction products were analyzed online using a gas chromatograph equipped with a dual FID detector. The reaction results are listed in Table 1.

[0040] Table 1

[0041]

[0042] Example 4

[0043] This embodiment provides an evaluation of the reaction of the Pd(0.6)Ru(0.3)Rh(1.2) / SiO2 catalyst when acetylene and ethylene are co-fed.

[0044] The acetylene aromatization reaction was carried out in a fixed-bed reactor using a stainless steel reactor with an inner diameter of 10 mm and a reaction pressure of atmospheric pressure. 2 g of Pd(0.6)Ru(0.3)Rh(1.2) / SiO2 prepared in Example 1 was added to the reactor, and the temperature was increased to 500 °C at 10 °C / min and maintained for 2 h in a hydrogen atmosphere. After reduction, the atmosphere was switched to N2 for purging for 1 h, and then the temperature was increased to 550 °C. A reaction gas of 10% C2H2 + 1% C2H4 + 89% N2 (volume composition) was then introduced, with a gas space velocity of 600 h⁻¹. -1 In the experiment, the gas flow rate was controlled by a mass flow meter, and the reaction products were analyzed online using a gas chromatograph equipped with a dual FID detector. The reaction results are listed in Table 2.

[0045] Table 2

[0046]

[0047] The results show that the reaction system using the Pd(0.6)Ru(0.3)Rh(1.2) / SiO2 catalyst exhibits higher benzene selectivity and reaction stability when both ethylene and acetylene are present in the reaction feed components, compared to the reaction with only acetylene.

[0048] Example 5

[0049] This embodiment provides an evaluation of the reaction of the Pd(0.6)Ru(0.3)Rh(1.2)Zn(0.4) / MCM-41 catalyst when acetylene and ethylene are co-fed.

[0050] The acetylene aromatization reaction was carried out in a fixed-bed reactor using a stainless steel reactor with an inner diameter of 10 mm and a reaction pressure of atmospheric pressure. 2 g of Pd(0.6)Ru(0.3)Rh(1.2)Zn(0.4) / MCM-41 prepared in Example 2 was added to the reactor, and the temperature was increased to 500 °C at a rate of 10 °C / min and maintained for 2 h in a hydrogen atmosphere. After reduction, the atmosphere was switched to N2 for purging for 1 h, and then cooled to 500 °C before introducing a reaction gas of 30% C2H2 + 5% C2H4 + 65% N2 (volume composition) at a gas hourly space velocity (GHSV) of 1800 h⁻¹. -1In the experiment, the gas flow rate was controlled by a mass flow meter, and the reaction products were analyzed online using a gas chromatograph equipped with a dual FID detector. The reaction results are listed in Table 3.

[0051] Table 3

[0052]

[0053] The results show that the reaction system using the Pd(0.6)Ru(0.3)Rh(1.2)Zn(0.4) / MCM-41 catalyst can achieve 100% acetylene conversion and more than 85% benzene selectivity when ethylene and acetylene are present in the reaction feed components, and can maintain this performance stably for at least 4 hours.

[0054] Example 7

[0055] This embodiment provides an evaluation of the reaction of the Pd(0.8)Ru(0.4)Rh(1.2)Zn(0.6) / SBA-15 catalyst when acetylene and ethylene are co-fed.

[0056] The acetylene aromatization reaction was carried out in a fixed-bed reactor using a stainless steel reactor with an inner diameter of 10 mm and a reaction pressure of atmospheric pressure. 2 g of Pd(0.8)Ru(0.4)Rh(1.2)Zn(0.6) / SBA-15 prepared in Example 2 was added to the reactor, and the temperature was increased to 550 °C at a rate of 10 °C / min and maintained for 2 h in a hydrogen atmosphere. After reduction, the atmosphere was switched to N2 for purging for 1 h, and then the temperature was increased to 550 °C again. A reaction gas mixture of 50% C2H2 + 10% C2H4 + 40% N2 (volume composition) was introduced, with a gas space velocity of 3000 h⁻¹. -1 In the experiment, the gas flow rate was controlled by a mass flow meter, and the reaction products were analyzed online using a gas chromatograph equipped with a dual FID detector. The reaction results are listed in Table 4.

[0057] Table 4

[0058]

[0059] The results show that the reaction system using the Pd(0.8)Ru(0.4)Rh(1.2)Zn(0.6) / SBA-15 catalyst can achieve 100% acetylene conversion and more than 84% benzene selectivity when ethylene and acetylene are present in the reaction feed components, and can maintain this performance stably for at least 4 hours.

[0060] Those skilled in the art should understand that the above-described embodiments are merely illustrative of the implementation of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention. Any technical solutions obtained by adopting equivalent substitutions or equivalent transformations should be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing benzene by aromatization of acetylene and ethylene as co-feeds, characterized in that, The material components containing ethylene and acetylene, along with nitrogen gas, are introduced into the reactor to contact the catalyst and carry out an aromatization reaction. The catalyst is a supported transition metal composite catalyst comprising a support and an active component; The supported transition metal composite catalyst has a palladium loading of 0.2-1.5% (based on the mass of palladium) as the support, a ruthenium loading of 0.2-1.5% (based on the mass of ruthenium) as the support, a rhodium loading of 0.2-1.5% (based on the mass of rhodium) as the support, and a zinc loading of 0.2-1.0% (based on the mass of zinc) as the support.

2. The method according to claim 1, characterized in that, The volume ratio of ethylene to acetylene in the material composition is 0.01-0.

2.

3. The method according to claim 1, characterized in that, The aromatization reaction is carried out at a temperature of 400-600℃ and an acetylene volume hourly space velocity of 500-3000 h⁻¹.

4. The method according to claim 1, characterized in that, Before the aromatization reaction, the catalyst is pretreated in situ at 500-600℃ in a hydrogen atmosphere for 1-3 hours in the reaction apparatus to reduce the active component to a metallic state.

5. A catalyst used in the method of claim 1, characterized in that, The supported transition metal composite catalyst was prepared by a room-temperature equal-volume impregnation method. The carrier is at least one of macroporous silica gel, MCM-41, and SBA-15; The active components are ruthenium, rhodium, palladium, and zinc.

6. The catalyst according to claim 5, characterized in that, The preparation method of the supported transition metal composite catalyst includes the following steps: S1. The calcined pretreated support was impregnated in an equal volume of palladium salt aqueous solution of different concentrations, dried, and calcined to obtain a supported palladium catalyst; S2. The supported palladium catalyst obtained in step S1 is impregnated in an equal volume of ruthenium and rhodium salt aqueous solution, dried and calcined to obtain a supported ruthenium, rhodium and palladium catalyst; S3. The supported ruthenium, rhodium, and palladium composite catalyst obtained in step S2 is impregnated in an equal volume into a zinc salt aqueous solution, dried, and calcined to obtain the supported ruthenium, rhodium, palladium, and zinc catalyst, namely the supported transition metal composite catalyst.

7. The catalyst according to claim 6, characterized in that, The palladium salt is PdCl2; the ruthenium salt is RuCl3; the rhodium salt is RhCl3; and the zinc salt is Zn(NO3)2.

8. The catalyst according to claim 6, characterized in that, The time for the equal-volume impregnation is 6-12 hours; the drying temperature is 110-150℃; the calcination is carried out in an air atmosphere by heating at 10℃ / min to 500-600℃ for 2-4 hours.

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