Production device and process technical method for preparing benzene and xylene through toluene disproportionation with high benzene yield

Abstract

The invention relates to a production device and process technical method for preparing benzene and xylene through toluene disproportionation with high benzene yield, a modified molecular sieve catalyst with high toluene conversion activity is adopted, optimized process condition parameters are selected, and the production device mainly comprises a reactor part and a fractionating tower part. The process condition parameters are as follows: the reaction pressure is 2-5MPa, the reaction temperature is 350-450 DEG C, the weight space velocity is 2-5h <-1 >, and the hydrogen-hydrocarbon molar ratio of the hydrogenation reaction is 2-5. And separating the generated dry gas and a small amount of non-aromatic hydrocarbons from the reaction product at the top of the stripping tower, sending the tower bottom material to a benzene-toluene merging tower for fractionation, respectively separating a pure benzene product and toluene at the side line of the tower, sending the tower bottom material to a xylene tower to separate a mixed xylene product and a byproduct heavy aromatic hydrocarbon, the byproduct heavy aromatics can be selectively recycled and merged into the toluene raw material and then enter the disproportionation reactor for conversion and utilization. The problems of low reaction space velocity, low one-way toluene conversion rate, large aromatic hydrocarbon loss and low benzene yield can be well solved.

Description

Technical Field

[0001] The present invention relates to a production device and a process technology method for producing benzene and xylene by disproportionation of toluene with high benzene yield, and in particular to a production device and a process technology method for disproportionation of toluene capable of increasing the benzene yield. Background Art

[0002] Aromatics are important basic raw materials for the petrochemical industry. Aromatics account for about 30% of known organic compounds. Among them, the output and scale of benzene (B), toluene (T), and xylene (X) are second only to ethylene and propylene, and they are called primary basic organic raw materials. Among the three main aromatics BTX, benzene is the basic aromatic chemical raw material with the demand second only to paraxylene (PX). It is mainly used to synthesize polymer nylon fibers and various plastics, and has a wide range of applications in the fields of medicine, pesticides, dyes, etc.

[0003] At present, large-scale industrial production of benzene is achieved through aromatics complex, which includes naphtha hydrogenation, catalytic reforming, cracked gasoline hydrogenation and other aromatics production units, as well as aromatics conversion and aromatics separation units. Among them, the toluene disproportionation unit is one of the key units in the aromatics complex, and the main products are benzene and xylene. Due to the increasing downstream demand for benzene products in recent years, toluene disproportionation conversion benzene production technology plays a more important role in adjusting the aromatics raw materials and product structure.

[0004] At present, the typical toluene disproportionation (and transalkylation) process technology for producing benzene and xylene is the hydrogen fixed bed Tatoray process jointly developed by UOP of the United States and TORAY of Japan in the 1970s. The toluene disproportionation and transalkylation process for producing benzene and xylene developed by Sinopec in China has been industrialized in 1997 (CN98122008.8, CN99113580.6, CN105272803A, US5210356). The raw materials of the toluene disproportionation and transalkylation process contain C10A heavy aromatics, and the high-space-velocity HAT series catalyst is used, so that the energy consumption and material consumption of the process unit are low, and it has excellent technical and economic indicators. At present, in addition to further improving the catalyst feed space velocity, increasing the xylene yield, reducing the reaction hydrogen-hydrocarbon ratio, and achieving energy conservation and consumption reduction, the main goal of the toluene disproportionation and transalkylation process and catalyst technology progress is to improve the catalyst's processing and conversion capacity for heavy aromatics, and to maximize the production of xylene products. At the same time, the reduction of catalyst costs is also conducive to improving the production efficiency of xylene.

[0005] Another toluene disproportionation technology for producing benzene and xylenes is the toluene shape-selective disproportionation technology for producing benzene and PX-xylene (CN93116960.7), which was first developed by Mobil Oil Corporation of the United States in the early 1990s. Sinopec has developed a combination of toluene shape-selective disproportionation and alkyl transfer (CN202110540458.6) with the goal of maximizing the yield of PX products in the product xylenes.

[0006] Although the process technology of producing benzene and xylene by toluene disproportionation reaction has been applied in production enterprises for nearly 50 years, in the past 20 years, except for the process technology of toluene shape-selective disproportionation to produce PX and para-xylene for the purpose of producing benzene products, various countries have invested in innovative research and technological improvement, but there are few research and development on the process technology of non-selective toluene disproportionation reaction to produce benzene and xylene, especially on toluene disproportionation equipment and process methods for high benzene production. At present, for the toluene disproportionation reaction for the purpose of producing benzene products, the research on efficient production equipment and process technology methods with high benzene selectivity, high space velocity processing capacity, high toluene conversion rate, low hydrogen consumption and high benzene purity has not been paid attention to; the existing production equipment and process technology (including catalysts) have technical problems such as low reaction space velocity, low single-pass toluene conversion rate, large aromatics loss and low benzene yield. The innovative research and development of catalysts, production equipment and process technology has very important economic and environmental value for the green and efficient production process of benzene and xylene, low energy and material consumption and reduced operating costs. Summary of the invention

[0007] In order to solve the above-mentioned technical, economic and environmental problems, the present invention provides a production device and process technology method for toluene disproportionation to produce benzene and xylene with high benzene yield. The production device and process technology method provided by the present invention are applied to toluene disproportionation to produce benzene and xylene production, and have the characteristics of high benzene yield, high product quality, high toluene conversion rate and low energy and material consumption.

[0008] The specific technical solution of the present invention is a production device and process technology method for producing benzene and xylene by toluene disproportionation with high benzene yield, characterized in that: the production device and process technology method include (1) a modified molecular sieve catalyst with high toluene conversion activity, (2) an efficient and simple process, and (3) a low-energy production device and preferred process conditions.

[0009] The modified molecular sieve catalyst with high toluene conversion activity is prepared from one or two hydrogen-type molecular sieves modified by transition metal oxides to form a three-leaf shaped particle molecular sieve catalyst.

[0010] The one or two hydrogen-type molecular sieves mentioned above are selected from nano-diamond MOR, plate-shaped ZSM-35, plate-shaped MCM-49, long strip ZSM-5 molecular sieve, nano-TNU-9 molecular sieve or a 10 / 90~50 / 50 wt / wt mixture of two of them, the modified molecular sieve accounts for 50~85wt% of the catalyst, and the rest is silica sol or nano-alumina binder.

[0011] The metal species of the molecular sieve modified transition metal oxide described above are selected from one or two of copper, nickel, cobalt, molybdenum, tin, titanium, chromium, iron, ruthenium, antimony and bismuth, and the content of the metal in the molecular sieve is 0.2-8.0wt%.

[0012] The efficient and concise process described above consists of a toluene disproportionation reaction part and a product distillation and separation part, and the product distillation and separation part uses an efficient and concise benzene-toluene combined tower for fractionation, and separates pure benzene product and toluene (circulated back to the raw material for further reaction) from the side line of the tower, and a xylene / trimethylbenzene mixture is also produced from the side line of the tower. The bottom material is heavy aromatic hydrocarbons with a carbon content of 10 or more as a by-product (sold as heavy aromatic oil).

[0013] The xylene / trimethylbenzene mixed material extracted from the side line of the efficient and simple benzene-toluene combined tower described above is sent to the xylene tower to separate the mixed xylene product and trimethylbenzene heavy aromatics, which can be recycled back to the toluene feedstock and then into the disproportionation reactor for conversion or sold as a by-product.

[0014] The low-energy production device described above consists of a disproportionation reactor part and a distillation tower part, wherein the disproportionation reactor is an axial fixed-bed reactor with airflow distribution, and a turbine-type airflow distribution device is installed on the top of the fixed-bed reactor to promote the full mixing of hydrogen and toluene and make the airflow flow into the catalyst bed in the reactor at a uniform linear velocity.

[0015] The operating parameters of the preferred process conditions described above are selected from the reaction pressure of 2-5 MPa, the reaction temperature of 350-450°C, the weight space velocity of 2-5 h -1 The hydrogen-to-hydrocarbon molar ratio in the hydrogenation reaction is 2-4, the reaction pressure is preferably 2.5-3 MPa, the reaction temperature is 360-400 °C, and the weight space velocity is 3-4 h -1 The molar ratio of hydrogen to hydrocarbon in the hydrogenation reaction is 2~3.

[0016] The reaction raw materials of the preferred process conditions described above are selected from pure toluene or crude toluene from petroleum processing or coal tar processing, wherein the sulfur, nitrogen and oxygen impurity content is less than 5 ppm, the toluene content is greater than 98%, and the rest are light hydrocarbons or aromatic impurities.

[0017] The above-mentioned high-benzene-yielding toluene disproportionation production device and process technology method for producing benzene and xylene are applied to the toluene disproportionation catalytic reaction production process, and its technical performance reaches a single-pass toluene conversion rate of more than 52%, a benzene selectivity of more than 48%, and an aromatics loss of less than 1.5%.

[0018] Compared with the existing toluene disproportionation technology, the present invention shows the following characteristics: The modified molecular sieve catalyst of the present invention (1) with high toluene conversion activity has better reaction performance than the existing molecular sieve catalysts for toluene shape selective disproportionation, toluene disproportionation and alkyl transfer to produce benzene (and xylene), and has the characteristics of good suitability for the reaction of toluene raw materials, high benzene selectivity and high toluene conversion rate.

[0019] The overall technical and economic efficiency of the (2) efficient and simple process adopted by the present invention is superior to the existing toluene shape-selective disproportionation process and toluene disproportionation and alkyl transfer process for producing benzene (and xylene), and it has the characteristics of high benzene quality, high operating stability, and low energy and material consumption.

[0020] The present invention adopts (3) a low-energy production device and optimized process conditions, and its technical reliability is superior to the existing toluene shape selective disproportionation device, toluene disproportionation and alkyl transfer benzene (and xylene) production device, and has the characteristics of high reaction space velocity, low operating cost, and low energy and material consumption.

[0021] As can be seen from the above, the production device and process technology method for preparing benzene and xylene by toluene disproportionation with high benzene yield provided by the present invention effectively solve the technical problems of low reaction space velocity, low single-pass toluene conversion rate, large aromatics loss, low benzene yield, and high energy and material consumption in the prior art. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the embodiments. Example 1

[0023] The long strip hydrogen-type ZSM-5 powder was vacuum impregnated with nickel nitrate solution and calcined at 450°C for 1 hour to obtain a 0.5% Ni-ZSM-5 molecular sieve with 0.5wt% Ni loaded on the ZSM-5 molecular sieve. The modified Ni-ZSM-5 molecular sieve and nano-alumina were mixed in a ratio of 60:40 and extruded into a clover-shaped catalyst with a length of 3-15 mm. The catalyst was calcined at 530°C in a muffle furnace for 2 hours to obtain a 0.5% Ni-ZSM-5 molecular sieve disproportionation catalyst.

[0024] The catalyst prepared above was loaded into an axial fixed bed reactor with airflow distribution. Figure 1The process device for producing benzene and xylene by toluene disproportionation with high benzene yield shown in the figure uses crude toluene (with sulfur, nitrogen and oxygen impurities content of 4.3 ppm and toluene content of 98.2%) from coal tar processing as the reaction raw material, at a reaction temperature of 350°C, a reaction pressure of 3.5 MPa, and H 2 In the medium atmosphere (hydrogen-to-hydrocarbon molar ratio of 2.2), the raw material mass space velocity WHSV is 3.0 h -1 The toluene disproportionation reaction process was evaluated under the conditions of , and each product was quantitatively analyzed by gas chromatograph. The analysis results are listed in Table 1. Example 2

[0025] The flake ZSM-35 powder was vacuum impregnated with a cobalt nitrate solution and calcined at 450°C for 1 hour to obtain a 1.8%Co-ZSM-35 molecular sieve in which 1.8 wt% Co was loaded on a ZSM-5 molecular sieve. Then, 5.5 wt% Mo was loaded on the catalyst by vacuum impregnation with ammonium tetramolybdate, and calcined at 500°C for 2 hours to obtain 1.8%Co-5.5%Mo-ZSM-35. The modified Co-Mo-ZSM-35 molecular sieve was mixed with nano-alumina in a ratio of 80:20 and extruded into a clover-shaped catalyst with a length of 3-15 mm. The catalyst was calcined at 530°C in a muffle furnace for 2 hours to obtain a 1.8%Co-5.5%Mo-ZSM-35 molecular sieve disproportionation catalyst.

[0026] The catalyst prepared above was loaded into an axial fixed bed reactor with airflow distribution. Figure 1 The process device for producing benzene and xylene by toluene disproportionation with high benzene yield shown in the figure uses pure toluene from petroleum processing (with a sulfur, nitrogen and oxygen impurity content of 1.2 ppm and a toluene content of 99.5%) as the reaction raw material, at a reaction temperature of 385°C, a reaction pressure of 3.0 MPa, and H 2 In the medium atmosphere (hydrogen-hydrocarbon molar ratio is 3), the raw material mass space velocity WHSV is 3.5 h -1 The toluene disproportionation reaction process was evaluated under the conditions of , and each product was quantitatively analyzed by gas chromatograph. The analysis results are listed in Table 1. Example 3

[0027] The nano-diamond MOR powder was vacuum impregnated with tin nitrate solution and calcined at 450°C for 1 hour to obtain a 2.5% Sn-MOR molecular sieve loaded with 2.5Sn%. The modified Sn-MOR molecular sieve was mixed with silica sol in a ratio of 50:50 and extruded into clover-shaped catalysts with a length of 3-15 mm. The catalysts were calcined at 530°C in a muffle furnace for 2 hours to obtain a 2.5% Sn-MOR molecular sieve disproportionation catalyst.

[0028] The catalyst prepared above was loaded into an axial fixed bed reactor with airflow distribution. Figure 1 The process device for producing benzene and xylene by toluene disproportionation with high benzene yield shown in the figure uses crude toluene (with sulfur, nitrogen and oxygen impurities content of 2.1 ppm and toluene content of 98.3%) from petroleum processing as the reaction raw material, at a reaction temperature of 368°C, a reaction pressure of 2.5 MPa, and H 2 In the medium atmosphere (hydrogen-to-hydrocarbon molar ratio of 2.1), the raw material mass space velocity WHSV is 2.6 h -1 The toluene disproportionation reaction process was evaluated under the conditions of , and each product was quantitatively analyzed by gas chromatograph. The analysis results are listed in Table 1. Example 4

[0029] The nano-TNU-9 molecular sieve powder was vacuum impregnated with ferric nitrate solution and calcined at 450°C for 1 hour to obtain a 3.8wt% Fe-TNU-9 molecular sieve with 3.8wt% Fe loaded on the TNU-9 molecular sieve. The modified Fe-TNU-9 molecular sieve and nano-alumina were mixed in a ratio of 70:30 and extruded into 3-15 mm clover-shaped catalysts, which were calcined at 530°C in a muffle furnace for 2 hours to obtain a 3.8wt% Fe-TNU-9 molecular sieve disproportionation catalyst.

[0030] The catalyst prepared above was loaded into an axial fixed bed reactor with airflow distribution. Figure 1 The process device for producing benzene and xylene by toluene disproportionation with high benzene yield shown in the figure uses pure toluene (with sulfur, nitrogen and oxygen impurities content of 1.0 ppm and toluene content of 99.2%) from coal tar processing as the reaction raw material, at a reaction temperature of 401°C, a reaction pressure of 3.5 MPa, and H 2 In the medium atmosphere (hydrogen-to-hydrocarbon molar ratio of 3.8), the raw material mass space velocity WHSV is 3.0 h -1 The toluene disproportionation reaction process was evaluated under the conditions of , and each product was quantitatively analyzed by gas chromatograph. The analysis results are listed in Table 1. Example 5

[0031] The flake ZSM-35 powder and the flake MCM-49 powder were mixed uniformly in a ratio of 1:1, and then vacuum impregnated with an antimony chloride solution, and calcined at 450°C for 1 hour to obtain a 4.6wt% Sb-ZSM-35 / MCM-49 molecular sieve in which 4.6wt% Sb was loaded on the ZSM-35 and MCM-49 molecular sieves. The modified Sb-ZSM-35 / MCM-49 molecular sieve and nano-alumina were mixed in a ratio of 85:15 and extruded into a clover-shaped catalyst of 3~15 mm, which was calcined in a muffle furnace at 530°C for 2 hours to obtain a 4.6wt% Sb-ZSM-35 / MCM-49 molecular sieve disproportionation catalyst.

[0032] The catalyst prepared above was loaded into an axial fixed bed reactor with airflow distribution. Figure 1 The process device for producing benzene and xylene by toluene disproportionation with high benzene yield shown in the figure uses crude toluene (with sulfur, nitrogen and oxygen impurities content of 3.2 ppm and toluene content of 98.5%) from coal tar processing as the reaction raw material, at a reaction temperature of 372°C, a reaction pressure of 2.9 MPa, and H 2 In the medium atmosphere (hydrogen-hydrocarbon molar ratio of 4.6), the raw material mass space velocity WHSV is 2.5 h -1 The toluene disproportionation reaction process was evaluated under the conditions of , and each product was quantitatively analyzed by gas chromatograph. The analysis results are listed in Table 1. Comparative Example 1

[0033] Ordinary rectangular hydrogen-type ZSM-5 molecular sieve powder and ordinary alumina are mixed in a ratio of 60:40 and extruded into cylindrical catalysts with a length of 3-15 mm. The catalysts are calcined at 530°C in a muffle furnace for 2 hours to obtain a ZSM-5 molecular sieve disproportionation catalyst.

[0034] The catalyst prepared above was loaded into an axial fixed bed reactor with airflow distribution. Figure 1 The process device for producing benzene and xylene by toluene disproportionation with high benzene yield shown in the figure uses pure toluene (with sulfur, nitrogen and oxygen impurities content of 1.0 ppm and toluene content of 99.5%) from coal tar processing as the reaction raw material, at a reaction temperature of 392°C, a reaction pressure of 3.0 MPa, and H 2 In the medium atmosphere (hydrogen-to-hydrocarbon molar ratio of 3.1), the raw material mass space velocity WHSV is 3.0 h -1 The toluene disproportionation reaction process was evaluated under the conditions of , and each product was quantitatively analyzed by gas chromatograph. The analysis results are listed in Table 1. Comparative Example 2

[0035] The long strip hydrogen-type ZSM-5 powder was vacuum impregnated with nickel nitrate solution and calcined at 450°C for 1 hour to obtain a 0.6% Ni-ZSM-5 molecular sieve with 0.6wt% Ni loaded on the ZSM-5 molecular sieve. The modified Ni-ZSM-5 molecular sieve and nano-alumina were mixed in a ratio of 60:40 and extruded into a clover-shaped catalyst with a length of 3-15 mm. The catalyst was calcined at 530°C in a muffle furnace for 2 hours to obtain a 0.6% Ni-ZSM-5 molecular sieve disproportionation catalyst.

[0036] The catalyst prepared above was loaded into a conventional axial fixed-bed reactor, and a conventional process device for toluene disproportionation to produce benzene and xylene was used. Pure toluene from petroleum processing (with a sulfur, nitrogen and oxygen impurity content of 0.9 ppm and a toluene content of 99.7%) was used as the reaction raw material. The reaction temperature was 381°C, the reaction pressure was 2.9 MPa, and the reaction temperature was 400 °C. 2 In the medium atmosphere (hydrogen-hydrocarbon molar ratio is 3.0), the raw material mass space velocity WHSV is 2.7 h -1 The technical performance of the toluene disproportionation reaction process was evaluated under the conditions of , and each product was quantitatively analyzed by gas chromatograph. The analysis results are listed in Table 1.

[0037] Table 1: Evaluation results of technical performance of toluene disproportionation process serial number catalyst Benzene mass (wt%) Toluene conversion rate (wt%) Benzene yield (wt%) Aromatic loss (wt%) Example 1 0.5%Ni-ZSM-5 99.97 52.4 48.3 1.4 Example 2 1.8%Co-5.5%Mo-ZSM-35 99.94 52.9 48.1 1.0 Example 3 2.5%Sn-MOR 99.95 53.2 48.5 1.2 Example 4 3.8wt% Fe-TNU-9 99.96 52.8 48.2 1.1 Example 5 4.6wt% Sb-ZSM-35 / MCM-49 99.97 53.6 49.0 1.3 Comparative Example 1 ZSM-5 99.82 46.7 44.5 2.3 Comparative Example 2 0.6%Ni-ZSM-5 99.73 48.2 45.1 2.8

[0038] Figure 1 . Production equipment and process flow chart for toluene disproportionation to produce benzene and xylenes.

Claims

1. A production device and process for high benzene yield by disproportionation of toluene to produce benzene and xylene, characterized by: The production device and process technology method include (1) a modified molecular sieve catalyst with high toluene conversion activity, (2) an efficient and simple process (as shown in FIG1 ), and (3) a low-energy production device and preferred process conditions.

2. According to claim 1, it is characterized in that: The modified molecular sieve catalyst with high toluene conversion activity is prepared from one or two hydrogen-type molecular sieves modified by transition metal oxides to form a three-leaf-shaped particle molecular sieve catalyst.

3. According to claim 2, it is characterized in that: The one or two hydrogen-type molecular sieves are selected from nano-diamond MOR, plate-shaped ZSM-35, plate-shaped MCM-49, long strip ZSM-5 molecular sieve, nano-TNU-9 molecular sieve or a 10 / 90~50 / 50 wt / wt mixture of two of them, the modified molecular sieve accounts for 50~85wt% of the catalyst, and the rest is silica sol or nano-alumina binder.

4. According to claim 2, it is characterized in that: The metal type of the molecular sieve modified transition metal oxide is selected from one or two of copper, nickel, cobalt, molybdenum, tin, titanium, chromium, iron, ruthenium, antimony and bismuth, and the content of the metal in the molecular sieve is 0.2-8.0wt%.

5. According to claim 1, it is characterized in that: The efficient and concise process consists of a toluene disproportionation reaction part and a product distillation and separation part, and the product distillation and separation part uses an efficient and concise benzene-toluene combined tower for fractionation, and separates pure benzene product and toluene (circulated back to the raw material for further reaction) from the side line of the tower, and a xylene / trimethylbenzene mixture is also produced from the side line of the tower. The bottom material is by-product heavy aromatics with a carbon content of ten or more (sold as heavy aromatic oil).

6. According to claim 5, it is characterized in that: The xylene / trimethylbenzene mixed material extracted from the side line of the efficient and simple benzene-toluene combined tower is sent to the xylene tower to separate the mixed xylene product and trimethylbenzene heavy aromatics, which can be recycled and incorporated into the toluene raw material and then enter the disproportionation reactor for conversion and utilization or sold as a by-product.

7. According to claim 1, it is characterized in that: The low-energy production device consists of a disproportionation reactor part and a fractionation tower part, wherein the disproportionation reactor is an axial fixed-bed reactor with airflow distribution, and a turbine-type airflow distribution device is installed on the top of the fixed-bed reactor to promote the full mixing of hydrogen and toluene and make the airflow flow into the catalyst bed in the reactor at a uniform linear velocity.

8. According to claim 1, it is characterized in that: The operating parameters of the preferred process conditions are selected from the reaction pressure of 2-5 MPa, the reaction temperature of 350-450 °C, the weight space velocity of 2-5 h -1 The hydrogen-to-hydrocarbon molar ratio in the hydrogenation reaction is 2-4, the reaction pressure is preferably 2.5-3 MPa, the reaction temperature is 360-400 °C, and the weight space velocity is 3-4 h -1 The molar ratio of hydrogen to hydrocarbon in the hydrogenation reaction is 2~3.

9. According to claim 1, it is characterized in that: The reaction raw materials of the preferred process conditions are selected from pure toluene or crude toluene from petroleum processing or coal tar processing, wherein the sulfur, nitrogen and oxygen impurity content is less than 5 ppm, the toluene content is greater than 98%, and the rest are light hydrocarbons or aromatic impurities.

10. According to claims 1 to 9, it is characterized in that: The production device and process technology method for high-yield benzene toluene disproportionation to produce benzene and xylene have technical performances of more than 52% single-pass toluene conversion, more than 48% benzene selectivity, and less than 1.5% aromatic hydrocarbon loss.

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