Efficient chlorination process of photocatalytic toluene
Through the excitation of the photocatalytic system of self-made catalysts A and B by LED blue light, the problems of equipment leakage and blockage and low selectivity in the toluene chlorination process are solved, and efficient and safe toluene chlorination are achieved, reducing energy consumption and raw material losses.
Patent Information
- Application Number
- CN202510588734.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-08
- Publication Date
- 2025-08-15
AI Technical Summary
The existing toluene chlorination process has equipment leakage and blockage problems, which affects production continuity and safety. In addition, the traditional thermal catalytic reaction has low selectivity, high energy consumption and large raw material losses.
LED blue light is used as the light source, and the photocatalytic system is formed using homemade catalysts A and B. The chlorine is excited by blue light to generate chlorine free radicals, attacking the C-H bond in the toluene molecule, forming C-Cl bonds, combining photocatalytic oxidation to treat the exhaust gas, and recycling chlorine.
It improves the selectivity and conversion rate of toluene chlorination reaction, reduces energy consumption and raw material losses, extends the catalyst usage cycle, reduces by-products, and improves the safety and economicality of production.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of toluene chlorination, in particular to a high-efficiency chlorination process of photocatalytic toluene. Background Art
[0002] Benzyl chloride, also known as benzyl chloride or chlorobenzene, is a typical organochlorine intermediate with extensive applications in dyes, pharmaceuticals, pesticides, fragrances, and organic synthesis. This wide range of applications has significantly boosted market demand for benzyl chloride. Construction of Lihai Company's benzyl chloride project began in 2010, with trial production beginning in 2013. The process utilizes advanced Belgian technology. Since its commissioning, the plant has operated stably, achieving leading domestic product quality. However, over the past decade, repeated starts and stops, coupled with equipment wear and tear, have weakened the existing production process and equipment, leading to equipment leaks and blockages, impacting the plant's production continuity, safety, and economic viability.
[0003] There are numerous methods for producing benzyl chloride. Domestically, there are two reaction processes for producing benzyl chloride from toluene chlorination: thermal chlorination and photochlorination. These processes are further categorized into batch and continuous operations. Chlorination synthesis is the core of benzyl chloride production, and its performance directly impacts both energy consumption and product quality. To meet market demand and rising environmental standards, research on toluene chlorination processes is being intensified, with innovations being made in catalyst improvements and reaction condition optimization. While ensuring reaction safety and product quality, these optimizations can reduce energy consumption and raw material losses during production, improve the return on capital investment, and help companies gain an advantage in the fiercely competitive market, driving the continuous advancement and improvement of their product technologies. Summary of the Invention
[0004] In view of the problems and shortcomings of the prior art, the present invention provides a high-efficiency chlorination process for photocatalytic toluene, which comprises the following steps:
[0005] The toluene is distilled at atmospheric pressure at a distillation temperature of 105°C-113°C. The refined toluene passes through a bottom condenser and is then pumped into a chlorination reactor containing a self-made catalyst A. The chlorine is heated by a chlorine heater and passed into the chlorination reactor while turning on the LED blue light inside the chlorination reactor. After the chlorination reaction is completed, the reaction liquid is sent to a chlorinated liquid storage tank. The hydrogen chloride gas released by the reaction is photocatalytically oxidized to produce chlorine, which is then passed into a chlorine heater to continue the reaction. The chlorinated liquid is pumped into a detoluene tower for negative pressure distillation at a distillation temperature of 117-132°C and a distillation tower pressure of -11 to -16 kPa. The toluene is separated and recovered at the top of the detoluene tower and directly returned to the chlorination reactor. The bottom product is a crude benzyl chloride product, which enters a benzyl chloride distillation tower for negative pressure distillation. The temperature at the top of the distillation tower is 85-100° C., the pressure at the distillation tower is -1 to -5 KPa, and the steam pressure is 0.25 to 0.6 MPa. The product is condensed at the top of the distillation tower to obtain the product. The bottom product is pumped into a dibenzyl chloride separation tower for negative pressure distillation. The temperature at the bottom of the dibenzyl chloride separation tower is 135-150° C., the pressure at the dibenzyl chloride separation tower is -4 to -6 KPa, and the bottom product is pumped into a dibenzyl chloride distillation tower for negative pressure distillation. The temperature at the bottom of the dibenzyl chloride distillation tower is 105-125° C., the pressure at the dibenzyl chloride distillation tower is -1 to -5 KPa, and the by-product is condensed at the top of the dibenzyl chloride distillation tower;
[0006] The preparation method of the self-made photocatalyst is:
[0007] (1) The chromium oxide sol is dried at 150-220°C for 2-8 hours under a mixed gas. After the drying is completed, the mixed gas flow rate is kept unchanged, and 1-3 mL / min of hydrogen sulfide gas is introduced. The temperature is raised to 500-750°C at a rate of 1-5°C / min and then maintained for 1-3 hours to obtain a solid material. The present invention improves the photocatalytic performance of the catalyst by doping bismuth and sulfur elements, thereby exciting chlorine to generate chlorine free radicals under blue light excitation, improving the reaction selectivity and the conversion rate of the toluene chlorination reaction. In the drying stage, the present invention uses bismuth-containing gas for drying. Under the influence of temperature, the bismuth element diffuses into the interior of the sol and combines with the sol to initially realize the loading of the bismuth element. At the same time, high-temperature drying causes the water inside the sol to vaporize, leaving pores, increasing the specific surface area of the catalyst, and then increasing multiple active sites, which is conducive to more complete contact with toluene and accelerates the chlorination reaction of toluene. In addition, ZrO2 is used as a carrier, which can be stably present in the subsequent hydrogen chloride gas photocatalytic oxidation process.
[0008] (2) 0.4-1g of solid material and 100mL of nitric acid solution were mixed and ground at 500rpm for 30min. The solid was separated and washed with deionized water. Finally, it was dried at 100℃ for 8h to obtain a homemade catalyst. The acidification grinding of the present invention promotes the reduction of the grain size, shortens the distance for photogenerated electrons and holes to migrate to the surface, reduces the occurrence of recombination, enhances the visible light catalytic performance, and at the same time, acidification improves the surface O V concentration, thereby capturing more photogenerated electrons and improving the photocatalytic efficiency.
[0009] The self-made catalyst in the present invention can be directly separated from the product and can be reused. It has high catalytic activity, is non-toxic and pollution-free, and is conducive to continuous industrial production.
[0010] Furthermore, the temperature of the chlorination reaction is 80-120°C.
[0011] Furthermore, the molar ratio of chlorine to toluene is 0.4 to 1:1.
[0012] Furthermore, the flow rate of the chlorine gas is 25 to 70 mL / min.
[0013] Furthermore, the chlorination time is 2 to 8 hours.
[0014] Furthermore, the photocatalytic oxidation is specifically to heat and mix with oxygen-containing gas in a catalytic oxidation unit, and perform a catalytic oxidation reaction under LED blue light to obtain chlorine.
[0015] Furthermore, the oxygen-containing gas contains at least 95% O2 and 1% CO2. The catalytic oxidation unit is carried out in the presence of a homemade catalyst B, and the co-heating mixing temperature is 80-140°C. The resulting gas is separated by temperature and pressure swing adsorption to complete the separation of chlorine and oxygen, and the oxygen continues to be introduced into the catalytic unit.
[0016] Furthermore, the preparation method of the homemade catalyst B is as follows: TiO2, WO3, and SnO2 are mixed in a molar ratio (Ti:W:Sn) of 1:10-50:1-5, with a ball-to-material ratio of 10:1 and a grinding speed of 400 rpm for 20 hours, and then calcined at 600°C for 5 hours in a C / Ar mixed atmosphere to form a heterojunction, reduce the activity of surface acid sites, reduce the corrosion of HCl gas on the homemade catalyst B, and improve the photocatalytic ability of the homemade catalyst B. In the C / Ar mixed atmosphere, a certain amount of C doping is formed on the surface of the homemade catalyst B, thereby improving the acid resistance of the homemade catalyst B.
[0017] Furthermore, the mixed gas flow rate in step (1) is 10 to 30 mL / min.
[0018] Furthermore, the volume ratio of tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas to argon gas in the mixed gas of step (1) is 1:10.
[0019] Furthermore, the concentration of the nitric acid solution in step (2) is 0.5 mol / L.
[0020] Compared with the prior art, the present invention has the following beneficial effects:
[0021] The present invention utilizes chlorine, toluene, and a special photocatalyst to form an efficient light absorption system. In this reaction system, by using blue light of a specific wavelength as a radiation source, the homemade catalyst is excited, causing the chlorine molecules pre-absorbed in the solution to produce a large number of chlorine free radicals. Under the continuous irradiation of blue light and the continuous excitation of the homemade catalyst A, these chlorine free radicals can quickly attack the C-H bonds in the toluene molecules. Due to the continuity of this excitation and attack, the breaking of the C-H bonds becomes extremely rapid and efficient. Subsequently, these active chlorine free radicals combine with the carbon cations in the toluene molecules to form new C-Cl bonds, thereby realizing the chlorination process of the toluene molecules. Compared with traditional thermal catalytic reactions, the photocatalytic method proposed in the present invention has shown significant advantages in improving reaction selectivity. DETAILED DESCRIPTION
[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0023] Example 1
[0024] (1) Chromium chloride and urea were mixed in a molar ratio of 2:5, and ethanol was added to prepare a chromium chloride solution with a concentration of 0.6 mol / L; the chromium chloride solution, titanium dioxide with a particle size of 10 nm, and ethyl acetate were uniformly mixed in a mass ratio of 10:2:1, and stirred at 65°C and 150 rpm for 30 minutes to obtain a chromium oxide sol;
[0025] (2) drying the chromium oxide sol at 150° C. for 2 h under a mixed gas with a mixed gas flow rate of 10 mL / min. After drying, the mixed gas flow rate is kept unchanged, and 1 mL / min of hydrogen sulfide gas is introduced. The temperature is raised to 500° C. at a rate of 1° C. / min and then maintained for 1 h to obtain a solid material; the volume ratio of tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas and argon in the mixed gas is 1:10, wherein the tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas is generated from a solid source bottle, and the raw material tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) is heated at 170° C. to generate tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas;
[0026] (3) 0.4 g of solid material and 100 mL of 0.5 mol / L nitric acid solution were mixed and ground at 500 rpm for 30 min. The resulting solid was separated, washed with deionized water, and finally dried at 100 °C for 8 h to obtain homemade catalyst A.
[0027] (4) TiO2, WO3, and SnO2 were mixed in a molar ratio (Ti:W:Sn) of 1:50:5, with a ball-to-material ratio of 10:1 and a grinding speed of 400 rpm for 20 h. The mixture was then calcined at 600°C for 5 h in a C / Ar mixed atmosphere with a volume ratio of CO2 to Ar of 1:50 to obtain a self-made catalyst B.
[0028] (5) Toluene is distilled at atmospheric pressure at a distillation temperature of 105°C. After the refined toluene passes through a bottom condenser, it is pumped into a chlorination reactor equipped with a self-made catalyst A. Chlorine is heated by a chlorine heater and passed into the chlorination reactor while turning on the LED blue light inside the chlorination reactor. The temperature of the chlorination reaction is 80°C, the molar ratio of chlorine to toluene is 0.6:1, the flow rate of chlorine is 40mL / min, and the chlorination time is 8h. After the chlorination reaction is completed, the reaction liquid is sent to the chlorination liquid storage tank. The hydrogen chloride gas released by the reaction is photocatalytically oxidized to produce chlorine. Specifically, it is co-heated and mixed with oxygen-containing gas in a catalytic oxidation unit. The molar ratio of HCl to oxygen is 1:1. A catalytic oxidation reaction is carried out under the illumination of LED blue light to obtain chlorine. The oxygen-containing gas contains at least 95% O2 and 1% CO2. The catalytic oxidation unit is carried out in the presence of a self-made catalyst B. The co-heated mixing temperature is 120°C. The gas obtained The body is separated by temperature and pressure swing adsorption to complete the separation of chlorine and oxygen. Oxygen continues to be introduced into the catalytic unit and the chlorine heater to continue to participate in the reaction. The chlorinated liquid is pumped into the detoluene tower for negative pressure distillation. The distillation temperature is 117°C and the distillation tower pressure is -11kPa. Toluene is separated and recovered at the top of the detoluene tower and directly returned to the chlorination reactor. The bottom of the tower is crude benzyl chloride, which enters the benzyl chloride distillation tower for negative pressure distillation. The top temperature of the distillation tower is 85°C and the distillation tower pressure is -11kPa. The pressure is -2 KPa, the steam pressure is 0.25 MPa, and the product is condensed at the top of the distillation tower. The bottom product is pumped into a dichlorobenzyl separation tower for negative pressure distillation. The bottom temperature of the dichlorobenzyl separation tower is 140°C, and the pressure of the dichlorobenzyl separation tower is -5 KPa. The bottom product is pumped into a dichlorobenzyl distillation tower for negative pressure distillation. The bottom temperature of the dichlorobenzyl distillation tower is 105°C, and the pressure of the dichlorobenzyl distillation tower is -3 KPa. The by-product is condensed at the top of the dichlorobenzyl distillation tower.
[0029] Example 2
[0030] (1) Chromium chloride and urea were mixed in a molar ratio of 2:5, and ethanol was added to prepare a chromium chloride solution with a concentration of 0.6 mol / L; the chromium chloride solution, titanium dioxide with a particle size of 10 nm, and ethyl acetate were uniformly mixed in a mass ratio of 10:2:1, and stirred at 65°C and 150 rpm for 30 minutes to obtain a chromium oxide sol;
[0031] (2) drying the chromium oxide sol at 190° C. for 5 h under a mixed gas with a mixed gas flow rate of 20 mL / min. After drying, the mixed gas flow rate is kept unchanged, and 2 mL / min of hydrogen sulfide gas is introduced. The temperature is raised to 625° C. at a rate of 3° C. / min and then maintained for 2 h to obtain a solid material. The volume ratio of tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas and argon in the mixed gas is 1:10, wherein the tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas is generated from a solid source bottle, and the raw material tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) is heated at 170° C. to generate tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas.
[0032] (3) 0.7 g of solid material and 100 mL of 0.5 mol / L nitric acid solution were mixed and ground at 500 rpm for 30 min. The resulting solid was separated, washed with deionized water, and finally dried at 100 °C for 8 h to obtain homemade catalyst A.
[0033] (4) TiO2, WO3, and SnO2 were mixed in a molar ratio (Ti:W:Sn) of 1:50:5, with a ball-to-material ratio of 10:1 and a grinding speed of 400 rpm for 20 h. The mixture was then calcined at 600°C for 5 h in a C / Ar mixed atmosphere with a volume ratio of CO2 to Ar of 1:50 to obtain a self-made catalyst B.
[0034] (5) Toluene is distilled at atmospheric pressure at a distillation temperature of 105°C. After the refined toluene passes through a bottom condenser, it is pumped into a chlorination reactor equipped with a self-made catalyst A. Chlorine is heated by a chlorine heater and passed into the chlorination reactor while turning on the LED blue light inside the chlorination reactor. The temperature of the chlorination reaction is 80°C, the molar ratio of chlorine to toluene is 0.6:1, the flow rate of chlorine is 40mL / min, and the chlorination time is 8h. After the chlorination reaction is completed, the reaction liquid is sent to the chlorination liquid storage tank. The hydrogen chloride gas released by the reaction is photocatalytically oxidized to produce chlorine. Specifically, it is co-heated and mixed with oxygen-containing gas in a catalytic oxidation unit. The molar ratio of HCl to oxygen is 1:1. A catalytic oxidation reaction is carried out under the illumination of LED blue light to obtain chlorine. The oxygen-containing gas contains at least 95% O2 and 1% CO2. The catalytic oxidation unit is carried out in the presence of a self-made catalyst B. The co-heated mixing temperature is 120°C. The gas obtained The body is separated by temperature and pressure swing adsorption to complete the separation of chlorine and oxygen. Oxygen continues to be introduced into the catalytic unit and the chlorine heater to continue to participate in the reaction. The chlorinated liquid is pumped into the detoluene tower for negative pressure distillation. The distillation temperature is 117°C and the distillation tower pressure is -11kPa. Toluene is separated and recovered at the top of the detoluene tower and directly returned to the chlorination reactor. The bottom of the tower is crude benzyl chloride, which enters the benzyl chloride distillation tower for negative pressure distillation. The top temperature of the distillation tower is 85°C and the distillation tower pressure is -11kPa. The pressure is -2 KPa, the steam pressure is 0.25 MPa, and the product is condensed at the top of the distillation tower. The bottom product is pumped into a dichlorobenzyl separation tower for negative pressure distillation. The bottom temperature of the dichlorobenzyl separation tower is 140°C, and the pressure of the dichlorobenzyl separation tower is -5 KPa. The bottom product is pumped into a dichlorobenzyl distillation tower for negative pressure distillation. The bottom temperature of the dichlorobenzyl distillation tower is 105°C, and the pressure of the dichlorobenzyl distillation tower is -3 KPa. The by-product is condensed at the top of the dichlorobenzyl distillation tower.
[0035] Example 3
[0036] (1) Chromium chloride and urea were mixed in a molar ratio of 2:5, and ethanol was added to prepare a chromium chloride solution with a concentration of 0.6 mol / L; the chromium chloride solution, titanium dioxide with a particle size of 10 nm, and ethyl acetate were uniformly mixed in a mass ratio of 10:2:1, and stirred at 65°C and 150 rpm for 30 minutes to obtain a chromium oxide sol;
[0037] (2) drying the chromium oxide sol at 150-220° C. for 8 h under a mixed gas with a mixed gas flow rate of 30 mL / min. After drying, the mixed gas flow rate is kept unchanged, and 3 mL / min of hydrogen sulfide gas is introduced. The temperature is raised to 750° C. at a rate of 5° C. / min and then maintained for 3 h to obtain a solid material. The volume ratio of tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas and argon in the mixed gas is 1:10, wherein the tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas is generated from a solid source bottle, and the raw material tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) is heated at 170° C. to generate tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas.
[0038] (3) 1 g of solid material and 100 mL of 0.5 mol / L nitric acid solution were mixed and ground at 500 rpm for 30 min. The resulting solid was separated, washed with deionized water, and finally dried at 100 °C for 8 h to obtain homemade catalyst A.
[0039] (4) TiO2, WO3, and SnO2 were mixed in a molar ratio (Ti:W:Sn) of 1:50:5, with a ball-to-material ratio of 10:1 and a grinding speed of 400 rpm for 20 h. The mixture was then calcined at 600°C for 5 h in a C / Ar mixed atmosphere with a volume ratio of CO2 to Ar of 1:50 to obtain a self-made catalyst B.
[0040] (5) Toluene is distilled at atmospheric pressure at a distillation temperature of 105°C. After the refined toluene passes through a bottom condenser, it is pumped into a chlorination reactor equipped with a self-made catalyst A. Chlorine is heated by a chlorine heater and passed into the chlorination reactor while turning on the LED blue light inside the chlorination reactor. The temperature of the chlorination reaction is 80°C, the molar ratio of chlorine to toluene is 0.6:1, the flow rate of chlorine is 40mL / min, and the chlorination time is 8h. After the chlorination reaction is completed, the reaction liquid is sent to the chlorination liquid storage tank. The hydrogen chloride gas released by the reaction is photocatalytically oxidized to produce chlorine. Specifically, it is co-heated and mixed with oxygen-containing gas in a catalytic oxidation unit. The molar ratio of HCl to oxygen is 1:1. A catalytic oxidation reaction is carried out under the illumination of LED blue light to obtain chlorine. The oxygen-containing gas contains at least 95% O2 and 1% CO2. The catalytic oxidation unit is carried out in the presence of a self-made catalyst B. The co-heated mixing temperature is 120°C. The gas obtained The body is separated by temperature and pressure swing adsorption to complete the separation of chlorine and oxygen. Oxygen continues to be introduced into the catalytic unit and the chlorine heater to continue to participate in the reaction. The chlorinated liquid is pumped into the detoluene tower for negative pressure distillation. The distillation temperature is 117°C and the distillation tower pressure is -11kPa. Toluene is separated and recovered at the top of the detoluene tower and directly returned to the chlorination reactor. The bottom of the tower is crude benzyl chloride, which enters the benzyl chloride distillation tower for negative pressure distillation. The top temperature of the distillation tower is 85°C and the distillation tower pressure is -11kPa. The pressure is -2 KPa, the steam pressure is 0.25 MPa, and the product is condensed at the top of the distillation tower. The bottom product is pumped into a dichlorobenzyl separation tower for negative pressure distillation. The bottom temperature of the dichlorobenzyl separation tower is 140°C, and the pressure of the dichlorobenzyl separation tower is -5 KPa. The bottom product is pumped into a dichlorobenzyl distillation tower for negative pressure distillation. The bottom temperature of the dichlorobenzyl distillation tower is 105°C, and the pressure of the dichlorobenzyl distillation tower is -3 KPa. The by-product is condensed at the top of the dichlorobenzyl distillation tower.
[0041] Comparative Example 1 (without adding nano titanium dioxide)
[0042] (1) Chromium chloride and urea were mixed in a molar ratio of 2:5, and ethanol was added to prepare a 0.6 mol / L chromium chloride solution; the chromium chloride solution was mixed with ethyl acetate in a mass ratio of 10:1, and the mixture was stirred at 65°C and 150 rpm for 30 minutes to obtain a chromium oxide sol;
[0043] (2) drying the chromium oxide sol at 190° C. for 5 h under a mixed gas with a mixed gas flow rate of 20 mL / min. After drying, the mixed gas flow rate is kept unchanged, and 2 mL / min of hydrogen sulfide gas is introduced. The temperature is raised to 625° C. at a rate of 3° C. / min and then maintained for 2 h to obtain a solid material. The volume ratio of tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas and argon in the mixed gas is 1:10, wherein the tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas is generated from a solid source bottle, and the raw material tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) is heated at 170° C. to generate tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas.
[0044] (3) 0.7 g of solid material and 100 mL of 0.5 mol / L nitric acid solution were mixed and ground at 500 rpm for 30 min. The resulting solid was separated, washed with deionized water, and finally dried at 100 °C for 8 h to obtain homemade catalyst A.
[0045] The process of toluene chlorination reaction adopts the same method as Example 1.
[0046] Comparative Example 2 (without adding bismuth-containing gas)
[0047] (1) Chromium chloride and urea were mixed in a molar ratio of 2:5, and ethanol was added to prepare a chromium chloride solution with a concentration of 0.6 mol / L; the chromium chloride solution, titanium dioxide with a particle size of 10 nm, and ethyl acetate were uniformly mixed in a mass ratio of 10:2:1, and stirred at 65°C and 150 rpm for 30 minutes to obtain a chromium oxide sol;
[0048] (2) drying the chromium oxide sol at 190° C. for 5 h under a mixed gas, introducing a mixed gas flow after drying, heating the mixture to 625° C. at a rate of 3° C. / min and maintaining the temperature for 2 h to obtain a solid material; the volume ratio of hydrogen sulfide gas to argon gas in the mixed gas is 1:10;
[0049] (3) 0.7 g of solid material and 100 mL of 0.5 mol / L nitric acid solution were mixed and ground at 500 rpm for 30 min. The resulting solid was separated, washed with deionized water, and finally dried at 100 °C for 8 h to obtain the homemade catalyst;
[0050] The process of toluene chlorination reaction adopts the same method as Example 1.
[0051] Comparative Example 3 (without adding hydrogen sulfide gas)
[0052] (1) Chromium chloride and urea were mixed in a molar ratio of 2:5, and ethanol was added to prepare a chromium chloride solution with a concentration of 0.6 mol / L; the chromium chloride solution, titanium dioxide with a particle size of 10 nm, and ethyl acetate were uniformly mixed in a mass ratio of 10:2:1, and stirred at 65°C and 150 rpm for 30 minutes to obtain a chromium oxide sol;
[0053] (2) drying the chromium oxide sol at 190° C. for 5 h under a mixed gas with a mixed gas flow rate of 20 mL / min. After drying, the mixed gas flow rate is kept unchanged, and the temperature is raised to 625° C. at a rate of 3° C. / min and then maintained for 2 h to obtain a solid material; the volume ratio of tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas and argon in the mixed gas is 1:10, wherein the tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas is generated from a solid source bottle, and the raw material tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) is heated at 170° C. to generate tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas;
[0054] (3) 0.7 g of solid material and 100 mL of 0.5 mol / L nitric acid solution were mixed and ground at 500 rpm for 30 min. The resulting solid was separated, washed with deionized water, and finally dried at 100 °C for 8 h to obtain the homemade catalyst;
[0055] The process of toluene chlorination reaction adopts the same method as Example 1.
[0056] Comparative Example 4 (without acidification grinding)
[0057] (1) Chromium chloride and urea were mixed in a molar ratio of 2:5, and ethanol was added to prepare a chromium chloride solution with a concentration of 0.6 mol / L; the chromium chloride solution, titanium dioxide with a particle size of 10 nm, and ethyl acetate were uniformly mixed in a mass ratio of 10:2:1, and stirred at 65°C and 150 rpm for 30 minutes to obtain a chromium oxide sol;
[0058] (2) drying the chromium oxide sol at 190°C for 5 h under a mixed gas with a mixed gas flow rate of 20 mL / min. After drying, the mixed gas flow rate was kept unchanged, and 2 mL / min of hydrogen sulfide gas was introduced. The temperature was raised to 625°C at a rate of 3°C / min and then maintained for 2 h to obtain a homemade catalyst. The volume ratio of tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas and argon in the mixed gas was 1:10, wherein tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas was generated from a solid source bottle, and the raw material tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) was heated at 170°C to generate tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas.
[0059] The process of toluene chlorination reaction adopts the same method as Example 1.
[0060] Table 1 Effect of homemade catalyst on toluene chlorination reaction
[0061]
[0062]
[0063] As can be seen from the table, the doping of bismuth and sulfur elements in the homemade catalyst improves the visible light catalytic performance of the catalyst and improves the conversion rate and selectivity of toluene.
[0064] Comparative Example 5
[0065] The same method as in Example 2 was used to prepare the homemade catalyst. The process of toluene chlorination was the same as in Example 2, but the light source was changed. The effect of the light source on the toluene chlorination process can be seen in Table 2:
[0066] Table 2 Effect of homemade catalyst dosage on toluene chlorination
[0067] light source Toluene conversion rate / % Product selectivity / % LED UV light 89.6 93.0 12W fluorescent lamp 83.5 91.2 40W fluorescent lamp 90.2 92.7 High-pressure mercury lamp 62.2 85.0
[0068] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference in a claim should not be construed as limiting the claim to which it relates.
Claims
1. A photocatalytic efficient chlorination process for toluene, characterized in that: The chlorination process comprises the following steps: The toluene is distilled at atmospheric pressure at a distillation temperature of 105°C-113°C. The refined toluene passes through a bottom condenser and is then pumped into a chlorination reactor containing a self-made catalyst A. The chlorine is heated by a chlorine heater and passed into the chlorination reactor while turning on the LED blue light inside the chlorination reactor. After the chlorination reaction is completed, the reaction liquid is sent to a chlorinated liquid storage tank. The hydrogen chloride gas released by the reaction is photocatalytically oxidized to produce chlorine, which is then passed into a chlorine heater to continue the reaction. The chlorinated liquid is pumped into a detoluene tower for negative pressure distillation at a distillation temperature of 117-132°C and a distillation tower pressure of -11 to -16 kPa. The toluene is separated and recovered at the top of the detoluene tower and directly returned to the chlorination reactor. The bottom product is a crude benzyl chloride product, which enters a benzyl chloride distillation tower for negative pressure distillation. The temperature at the top of the distillation tower is 85-100° C., the pressure at the distillation tower is -1 to -5 KPa, and the steam pressure is 0.25 to 0.6 MPa. The product is condensed at the top of the distillation tower to obtain the product. The bottom product is pumped into a dibenzyl chloride separation tower for negative pressure distillation. The temperature at the bottom of the dibenzyl chloride separation tower is 135-150° C., the pressure at the dibenzyl chloride separation tower is -4 to -6 KPa, and the bottom product is pumped into a dibenzyl chloride distillation tower for negative pressure distillation. The temperature at the bottom of the dibenzyl chloride distillation tower is 105-125° C., the pressure at the dibenzyl chloride distillation tower is -1 to -5 KPa, and the by-product is condensed at the top of the dibenzyl chloride distillation tower; The preparation method of the homemade catalyst A is: (1) drying the chromium oxide sol at 150-220° C. for 2-8 hours under a mixed gas; after drying, while maintaining the mixed gas flow rate unchanged, introducing 1-3 mL / min of hydrogen sulfide gas, heating the mixture to 500-750° C. at a rate of 1-5° C. / min, and maintaining the temperature for 1-3 hours to obtain a solid material; (2) 0.4-1 g of solid material and 100 mL of nitric acid solution were mixed, ground at 500 rpm for 30 min, and the resulting solid was separated, washed with deionized water, and finally dried at 100 °C for 8 h to obtain a homemade catalyst.
2. The efficient chlorination process of photocatalytic toluene according to claim 1, characterized in that: The temperature of the chlorination reaction is 80-120°C.
3. The efficient chlorination process of photocatalytic toluene according to claim 1, characterized in that: The molar ratio of the chlorine gas to toluene is 0.4 to 1:
1.
4. The efficient chlorination process of photocatalytic toluene according to claim 1, characterized in that: The flow rate of the chlorine gas is 25-70 mL / min.
5. The efficient chlorination process of photocatalytic toluene according to claim 1, characterized in that: The chlorination time is 2 to 8 hours.
6. The efficient chlorination process of photocatalytic toluene according to claim 1, characterized in that: The photocatalytic oxidation is specifically to heat and mix with oxygen-containing gas in a catalytic oxidation unit, and perform a catalytic oxidation reaction under LED blue light to obtain chlorine.
7. A photocatalytic efficient chlorination process for toluene according to claim 6, characterized in that: The oxygen-containing gas contains at least 95% O2 and 1% CO2. The catalytic oxidation unit is carried out in the presence of a homemade catalyst B, and the co-heat mixing temperature is 80-140°C. The obtained gas is separated by temperature-pressure swing adsorption to complete the separation of chlorine and oxygen, and oxygen continues to be introduced into the catalytic unit; the preparation method of the homemade catalyst B is: TiO2, WO3, and SnO2 are mixed in a molar ratio of Ti:W:Sn=1:10-50:1-5, with a ball-to-material ratio of 10:1 and a grinding speed of 400rpm for 20h, and then calcined at a high temperature of 600°C for 5h in a C / Ar mixed atmosphere.
8. The efficient chlorination process of photocatalytic toluene according to claim 1, characterized in that: The mixed gas flow rate in step (1) is 10 to 30 mL / min.
9. The efficient chlorination process of photocatalytic toluene according to claim 1, characterized in that: The volume ratio of tris(2,2,6,6-tetramethyl-3,5-heptanedione)bismuth(III) gas to argon gas in the mixed gas of step (1) is 1:
10.
10. The efficient photocatalytic chlorination process of toluene according to claim 9, characterized in that: The concentration of the nitric acid solution in step (2) is 0.5 mol / L.