Method for recycling cumene in process of preparing propylene oxide by cumene co-oxidation method

Abstract

The present invention provides a method for recycling cumene in a process of preparing propylene oxide by a cumene co-oxidation method. The method comprises: rectifying and separating the cumene in the reaction solution of α,α-dimethyl benzyl alcohol hydrogenolysis, and removing impurities by means of alkali washing. By controlling the proportion and content of cyclohexanol and phenol therein, the reuse times and recycling rate of recycled cumene can be greatly improved, and the cost of production of the propylene oxide by the cumene co-oxidation method can be effectively reduced.

Description

A method for recycling cumene in the process of preparing propylene oxide by cumene co-oxidation Technical Field

[0001] The invention belongs to the field of chemical intermediate synthesis, and particularly relates to a method for recycling cumene in the process of preparing propylene oxide by a cumene co-oxidation method. Background Art

[0002] PO (propylene oxide, CAS No. 75-56-9, molecular formula C3H6O) is an important organic chemical product of propylene derivatives and an important raw material for the production of polyurethane, polyether and surfactants.

[0003] Industrial methods for producing propylene oxide include the chlorohydrin process, the co-oxidation process (Halcon process), and the direct hydrogen peroxide oxidation process (HPPO process). The chlorohydrin process is one of the primary methods for producing propylene oxide (PO) in China, accounting for approximately 40% of the domestic production. However, the chlorohydrin process suffers from severe equipment corrosion, large amounts of wastewater and solid waste, and significant environmental pollution, and will be phased out in China. The direct hydrogen peroxide oxidation process (HPPO process) is not very economical due to the high cost of hydrogen peroxide production and high material consumption. The co-oxidation process, also known as the co-production process or indirect oxidation process, produces propylene oxide through the reaction of an organic peroxide with propylene, with the simultaneous production of organic alcohols. These processes primarily include the PO / TBA (MTBE), PO / SM, and POCHP processes. The PO / MTBE process suffers from a lengthy process and high equipment investment. Furthermore, due to the ban on MTBE in the oil blending market, the MTBE market is expected to shrink, leading to a gradual decline in the domestic market for the PO / MTBE process. The PO / SM process has a long process flow, large equipment investment, and produces large amounts of wastewater and waste gas. With the launch of large-scale domestic refining and chemical integration projects, the country has concentrated investment in multiple PO / SM processes at one time, and a large amount of ethylbenzene dehydrogenation to produce styrene has appeared in the country. The domestic SM market will be seriously oversupplied. SM is currently on the verge of profit and loss, and the overall economic efficiency of PO / SM is not high.

[0004] The co-oxidation of cumene to produce propylene oxide was first industrialized by Sumitomo Corporation of Japan. The process includes: cumene is oxidized to cumene hydroperoxide (CHP) with air at a certain temperature and pressure, and then epoxidized with propylene using cumene hydroperoxide (CHP) to produce propylene oxide. The α,α-dimethylbenzyl alcohol produced by the epoxidation reaction undergoes hydrogenolysis to produce cumene, and the cumene is recycled in the peroxidation reaction, thereby achieving the recycling of cumene.

[0005] Compared with other co-oxidation processes, the cumene co-oxidation method offers distinct advantages: a shorter process path, reduced equipment investment, and the absence of by-products. However, the process's greatest challenge lies in the hydrogenolysis of α,α-dimethylbenzyl alcohol to produce cumene. The hydrogenolysis reaction liquid contains cumene, water, unreacted hydrogen, α,α-dimethylbenzyl alcohol, cyclohexanol, cyclohexanone, and other substances. These substances easily emulsify with water, resulting in poor phase separation in the reaction liquid and the inclusion of water in the oily cumene phase, which affects cumene refining. The process's greatest drawback is the material losses associated with the process flow, which directly impact the overall process economics. Improving the recycling rate of cumene is crucial for reducing the cost of producing propylene oxide using the cumene co-oxidation method.

[0006] Summary of the Invention

[0007] The object of the present invention is to provide a method for recycling cumene in the process of preparing propylene oxide by a cumene co-oxidation method. By controlling the content of cyclohexanol in the recycled cumene, preferably simultaneously controlling the ratio of cyclohexanol and phenol impurities, the number of recycling times of the recycled cumene can be greatly increased while ensuring the product yield, thereby effectively reducing the production cost of propylene oxide.

[0008] Our research found that after repeated use of recycled isopropyl benzene, the yield of the peroxidation reaction will decrease and the catalyst of the epoxidation reaction will be deactivated; the main reason for this adverse phenomenon is that some key impurities exist in the recycled isopropyl benzene, among which cyclohexanol is a representative impurity, followed by impurities such as phenol, and these impurities will inevitably be generated during the reaction process.

[0009] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0010] The first aspect of the present invention provides a method for recycling isopropylbenzene in the process of preparing propylene oxide by a cumene co-oxidation method, wherein the cyclohexanol content in the recycled isopropylbenzene is controlled to be 2 to 1000 ppm (for example, 3 ppm, 5 ppm, 8 ppm, 12 ppm, 15 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 100 ppm, 150 ppm, 200 ppm, 400 ppm, 500 ppm, 600 ppm, 800 ppm), preferably 10 to 300 ppm; the mass ratio of cyclohexanol to phenol is (1 to 100):2, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 8:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 48:1, preferably (2 to 50):2.

[0011] A second aspect of the present invention provides a method for recycling cumene in a process of preparing propylene oxide by a cumene co-oxidation process, comprising: reacting cumene with oxygen in the air to produce cumene hydroperoxide; reacting the cumene hydroperoxide (e.g., after concentration) with propylene (e.g., in the presence of a titanium silicalite catalyst) to produce propylene oxide and α,α-dimethylbenzyl alcohol; reacting the α,α-dimethylbenzyl alcohol with hydrogen in the presence of a hydrogenolysis catalyst to produce cumene; then separating the cumene from the hydrogenolysis reaction solution by distillation; and alkali washing the separated cumene before recycling.

[0012] Among them, the cyclohexanol content in the recycled isopropylbenzene after alkali washing is controlled to be 2 to 1000 ppm (for example, 10 ppm, 50 ppm, 100 ppm, 200 ppm, 400 ppm, 500 ppm, 800 ppm, 1000 ppm, etc.), and the mass ratio of cyclohexanol to phenol is (1 to 100):2 (for example, 1:2, 10:2, 20:2, 30:2, 40:2, 80:2, 90:2, etc.).

[0013] Furthermore, the content of cyclohexanol in the recycled cumene fraction after alkali washing is controlled to be 10-300 ppm, and the mass ratio of cyclohexanol to phenol in the cumene fraction is (2-50):2.

[0014] During the reaction of cumene with oxygen, a certain amount of cumene hydroperoxide (CHP) can be added to the system as an initiator. In some embodiments of the present invention, during the peroxidation reaction, the pressure of the reaction of cumene with oxygen is 0 to 0.5 MPaG (e.g., 0.01 MPaG, 0.05 MPaG, 0.1 MPaG, 0.2 MPaG, 0.3 MPaG, 0.4 MPaG, 0.45 MPaG) and the temperature is 90 to 110° C. (e.g., 95° C., 100° C., 105° C.).

[0015] In some embodiments of the present invention, the peroxidation reactors are operated in series, and the number of reactors is 1 to n, where n≤6 (e.g., 2, 3, 4, 5); the mass concentration of cumene hydroperoxide in the peroxidation reaction liquid at the outlet of the peroxidation reactor is 10 to 30% (e.g., 12%, 15%, 18%, 20%, 25%, 28%), preferably 20 to 26%.

[0016] In some embodiments of the present invention, the peroxidation reaction liquid can be subjected to a distillation and concentration process; after the distillation and concentration, the mass concentration of the cumene hydroperoxide therein is 30-55% (for example, 32%, 35%, 38%, 40%, 45%, 50%); the concentrated cumene hydroperoxide is mixed with propylene and then enters an epoxidation reactor for epoxidation reaction, and the pressure of the reaction of cumene hydroperoxide and propylene is 3.5-8 MPaG (for example, 4 MPaG, 4.5 MPaG, 5 MPaG, 5.5 MPaG, 6 MPaG, 6.5 MPaG, 7 MPaG, 7.5 MPaG), and the reaction temperature is 40-120° C. (for example, 50° C., 60° C., 80° C., 100° C., 110° C.).

[0017] In some embodiments of the present invention, the reaction liquid at the outlet of the epoxidation reactor undergoes a separation process to separate propylene oxide, and the remainder is a cumene solution of α,α-dimethylbenzyl alcohol, wherein the mass concentration of α,α-dimethylbenzyl alcohol is preferably 20-35%. The material containing α,α-dimethylbenzyl alcohol enters the hydrogenolysis reactor, and the reactor pressure is 1.5-3.0 MPaG (e.g., 1.8 MPaG, 2.0 MPaG, 2.2 MPaG, 2.5 MPaG, 2.8 MPaG), the reaction temperature is 130-200°C (e.g., 135°C, 140°C, 150°C, 160°C, 180°C, 195°C), and the molar ratio of α,α-dimethylbenzyl alcohol to hydrogen is 1:5-14 (e.g., 1:5.5, 1:6, 1:8, 1:10, 1:12). The hydrogenolysis catalyst is selected from a palladium-silica catalyst or a copper-zinc oxide catalyst.

[0018] In some embodiments, the hydrogenolysis reaction liquid is first processed by a distillation de-heavy tower, the recombinant branch stream of the de-heavy tower kettle enters the waste oil system, the top stream of the de-heavy tower enters the distillation de-light tower for processing, the light components at the top of the de-light tower enter the waste oil system, and the separated isopropyl benzene is obtained in the bottom of the de-light tower, the temperature of which is 110°C to 140°C (for example, 120°C, 130°C), which usually contains 1135-1367ppm (for example, 1140ppm, 1150ppm, 1200ppm, 1250ppm, 1300ppm, 1350ppm) of cyclohexanol, 100-400ppm (for example, 110ppm, 120ppm, 150ppm, 200ppm, 300ppm, 350ppm) of phenol, and about 0.2wt% of other impurities.

[0019] In some embodiments of the present invention, the distillation heavy removal tower and the distillation light removal tower can adopt a common distillation process or a double-effect distillation process; in order to save energy during the distillation process, the double-effect distillation process is preferred.

[0020] In some embodiments of the present invention, the operating process conditions of the weight removal tower include: operating at normal pressure, the number of theoretical plates of the distillation tower is 5 to 30 (for example, 6, 8, 10, 15, 20, 25, 28), and the reflux ratio is 0.1 to 5 (for example, 0.2, 0.5, 1, 1.5, 2, 3, 4, 4.5); the operating process conditions of the lightness removal tower include: operating under negative pressure, the pressure is 20 to 60 KPaA (for example, 22 KPaA, 25 KPaA, 30 KPaA, 35 KPaA, 40 KPaA, 45 KPaA, 50 KPaA, 55 KPaA, 58 KPaA), the number of theoretical plates of the distillation tower is 5 to 35 (for example, 6, 8, 10, 15, 20, 25, 28, 30, 32), and the reflux ratio is 1 to 10 (for example, 1.5, 2, 3, 4, 5, 6, 8, 9).

[0021] In some embodiments of the present invention, the cumene separated from the bottom of the lightness removal tower is washed with alkali (sodium hydroxide solution), and the oil-water mass ratio of the alkali washing process is 1:0.01-0.5 (for example, 1:0.02, 1:0.04, 1:0.08, 1:0.1, 1:0.15, 1:0.2, 1:0.3, 1:0.4, 1:0.45), preferably 1:0.05-0.2, the alkali washing temperature is 30-60°C (for example, 35°C, 40°C, 45°C, 50°C, 55°C), and the pH value of the aqueous phase is 12-14 (for example, 12.5, 13, 13.5), until the cyclohexanol content in the recycled cumene fraction after alkali washing is 2-1000 ppm, and the mass ratio of cyclohexanol to phenol is (1-100):2.

[0022] The positive effects of the present invention are at least:

[0023] By controlling the cyclohexanol content in the recycled cumene within a suitable range and further controlling the ratio of cyclohexanol to phenol, unlimited reuse of cumene can be achieved. Under this impurity ratio, the side reaction of cumene peroxidation will not be further aggravated. At the same time, the reduction of by-products in the peroxidation reaction liquid will improve the selectivity of the epoxidation reaction, thereby effectively reducing the material consumption of cumene in the process of preparing propylene oxide by the cumene method and reducing the production cost of propylene oxide. DETAILED DESCRIPTION

[0024] The present invention will be further described below through specific examples. The examples of the present invention are only for illustration of the present invention and do not limit the scope of the present invention.

[0025] Unless otherwise specified, the main raw materials and reagents involved in the following examples of the present invention were purchased from commercial sources.

[0026] Gas phase analysis conditions: Agilent 7890B, chromatographic column HP-5ms, vaporizer temperature of 290°C, detector temperature of 280°C; programmed temperature rise: 50°C for 2 min; temperature rise at a rate of 40°C / min to 100°C for 1 min; temperature rise at a rate of 10°C / min to 200°C for 2 min; temperature rise at a rate of 40°C / min to 280°C for 6 min.

[0027] Cumene was sourced from Wanhua Chemical Group;

[0028] The catalyst for the epoxidation reaction was derived from commercially available titanium silicalite molecular sieves;

[0029] The catalyst for the hydrogenolysis reaction was a commercially available copper-zinc oxide catalyst.

[0030] In the following examples and comparative examples, unless otherwise specified, the solution concentrations involved are understood to be mass concentrations.

[0031] Example 1:

[0032] 600 g of cumene was added to a 1000 ml reactor, and the temperature was raised to 102° C. 30 g of 85% cumene hydroperoxide (CHP) was pumped into the reactor as an initiator using a horizontal flow pump. Air was simultaneously introduced into the reactor at a rate of 1 L / min. During the reaction, the oxygen content in the tail gas was detected to be less than 6 mol%. After 5 h of reaction, the conversion of cumene was 20.45%, the selectivity of CHP was 92.87%, and the selectivity of side reactions was 2.52%.

[0033] After the reaction is completed, a peroxidation reaction liquid is obtained; the peroxidation reaction liquid is subjected to a first-stage alkali wash (the alkali solution is a sodium hydroxide aqueous solution with a concentration of 32 wt%) and a two-stage water wash, and then the CHP stream is concentrated. After the CHP concentration reaches 35.87%, it enters the epoxidation reaction process;

[0034] The epoxidation reaction was carried out in a fixed-bed reactor containing 100 ml of a commercially available titanium silicalite catalyst. A 35.87% CHP solution mixed with propylene was introduced into the fixed-bed reactor. The molar ratio of propylene to CHP was 5. The CHP solution feed rate was 2.5 ml / min. The reaction temperature was 75° C., the reaction pressure was 5.8 MPaG, and an epoxidation reaction solution was obtained after the reaction. The selectivity of propylene oxide in the epoxidation reaction was 96.34%.

[0035] The epoxidation reaction liquid is subjected to a distillation separation process to separate propylene oxide, and the remainder is a cumene solution of α,α-dimethylbenzyl alcohol, wherein the α,α-dimethylbenzyl alcohol content is 30%. This material is fed into a hydrogenolysis reactor for hydrogenolysis reaction to obtain cumene;

[0036] The reactor used for the hydrogenolysis reaction is a fixed-bed reactor. 80 ml of a commercially available copper-zinc oxide catalyst is loaded in the reactor. A material containing α,α-dimethylbenzyl alcohol is mixed with hydrogen and then introduced into the reactor. The molar ratio of α,α-dimethylbenzyl alcohol to hydrogen is 1:8. The feed rate of the material containing α,α-dimethylbenzyl alcohol is 2 ml / min. The reaction temperature is 175° C., the reaction pressure is 2.5 MPaG, and the reaction obtains a hydrogenolysis reaction liquid.

[0037] The hydrogenolysis reaction liquid undergoes simple phase separation to obtain an oil phase, which enters a distillation de-weighting tower to remove heavy components. The distillation de-weighting tower has 15 theoretical plates and operates at atmospheric pressure with a reflux ratio of 0.5. The recombinant fraction from the bottom of the de-weighting tower enters the waste oil system, and the fraction from the top of the de-weighting tower enters the feed of the distillation de-lighting tower.

[0038] The distillation lightness removal tower is operated under negative pressure, the pressure is 25KPaA, the theoretical plate number of the distillation lightness removal tower is 28, the reflux ratio is 5, the bottom temperature of the lightness removal tower is 125°C, and the bottom of the tower obtains the separated recycled isopropylbenzene.

[0039] The recycled isopropyl benzene undergoes an alkaline washing process (the alkaline solution is a 32wt% sodium hydroxide aqueous solution), the oil-water mass ratio of the alkaline washing is 1:0.1, the alkaline washing temperature is 50°C, the pH value of the alkaline washing aqueous phase is 13.5, until the cyclohexanol content in the recycled isopropyl benzene after alkaline washing is 244ppm, the phenol content is 5ppm, and the purity of the isopropyl benzene is 98.46%.

[0040] Propylene oxide was prepared under the same conditions as those for the aforementioned preparation of propylene oxide (the difference being that the amount of the starting raw material cumene was reduced to 585 g, the cyclohexanol content in the recycled cumene used was 244 ppm, the phenol content was 5 ppm, and the cumene purity was 98.46%). The conversion rate of cumene in the peroxidation reaction was 20.33%, the selectivity of CHP was 92.16%, the side reaction selectivity was 2.61%, and the selectivity of propylene oxide in the epoxidation reaction was 96.12%.

[0041] Example 2:

[0042] 600 g of cumene was added to a 1000 ml reactor, and the temperature was raised to 105° C. 30 g of 85% cumene hydroperoxide (CHP) was pumped into the reactor as an initiator using a horizontal flow pump. Air was simultaneously introduced into the reactor at a rate of 1 L / min. During the reaction, the oxygen content in the tail gas was detected to be less than 6 mol%. After 5 h of reaction, the conversion of cumene was 20.71%, the selectivity of CHP was 92.68%, and the selectivity of side reactions was 2.43%.

[0043] After the reaction is completed, a peroxidation reaction liquid is obtained; the peroxidation reaction liquid is subjected to a first-stage alkali wash (the alkali solution is a sodium hydroxide aqueous solution with a concentration of 32 wt%) and a two-stage water wash, and then the CHP stream is concentrated. After the CHP concentration reaches 35.42%, it enters the epoxidation reaction process;

[0044] The epoxidation reaction was carried out in a fixed-bed reactor containing 100 ml of a commercially available titanium silicalite catalyst. A 35.42% CHP solution mixed with propylene was introduced into the fixed-bed reactor. The molar ratio of propylene to CHP was 4.5. The feed rate of the CHP solution was 2.5 ml / min. The reaction temperature was 67° C., the reaction pressure was 5 MPaG, and an epoxidation reaction solution was obtained after the reaction. The selectivity of the propylene oxide in the epoxidation reaction was 96.15%.

[0045] The epoxidation reaction liquid is subjected to a distillation separation process to separate propylene oxide, and the remainder is a cumene solution of α,α-dimethylbenzyl alcohol, wherein the α,α-dimethylbenzyl alcohol content is 28%. This material is fed into a hydrogenolysis reactor for hydrogenolysis reaction to obtain cumene;

[0046] The reactor used for the hydrogenolysis reaction is a fixed-bed reactor. 80 ml of a commercially available copper-zinc oxide catalyst is loaded in the reactor. A material containing α,α-dimethylbenzyl alcohol is mixed with hydrogen and then introduced into the reactor. The molar ratio of α,α-dimethylbenzyl alcohol to hydrogen is 1:6. The feed rate of the material containing α,α-dimethylbenzyl alcohol is 2 ml / min. The reaction temperature is 182° C., the reaction pressure is 2.5 MPaG, and the reaction obtains a hydrogenolysis reaction liquid.

[0047] The hydrogenolysis reaction liquid undergoes simple phase separation to obtain an oil phase, which enters a distillation de-weighting tower to remove heavy components. The distillation de-weighting tower has 20 theoretical plates and operates at atmospheric pressure with a reflux ratio of 0.8. The recombinant fraction from the bottom of the de-weighting tower enters the waste oil system, and the fraction from the top of the de-weighting tower enters the feed of the distillation de-lighting tower.

[0048] The distillation and lightness removal tower is operated under negative pressure, the pressure is 50KPaA, the theoretical plate number of the distillation and lightness removal tower is 35, the reflux ratio is 3, the bottom temperature of the lightness removal tower is 116°C, and the bottom of the tower obtains the separated recycled cumene.

[0049] The recycled isopropyl benzene undergoes an alkaline washing process (the alkaline solution is a 32wt% sodium hydroxide aqueous solution), the oil-water mass ratio of the alkaline washing is 1:0.5, the alkaline washing temperature is 50°C, the pH value of the alkaline washing aqueous phase is 12.8, until the cyclohexanol content in the recycled isopropyl benzene after alkaline washing is 145ppm, the phenol content is 3ppm, and the purity of the isopropyl benzene is 98.45%.

[0050] Propylene oxide was prepared under the same conditions as those for the aforementioned preparation of propylene oxide (the difference being that the amount of the starting raw material cumene was reduced to 582 g, the cyclohexanol content in the recycled cumene used was 145 ppm, the phenol content was 3 ppm, and the cumene purity was 98.45%). The conversion rate of cumene in the peroxidation reaction was 20.92%, the selectivity of CHP was 92.36%, the side reaction selectivity was 2.52%, and the selectivity of propylene oxide in the epoxidation reaction was 96.45%.

[0051] Example 3:

[0052] 600 g of cumene was added to a 1000 ml reactor, and the temperature was raised to 101° C. 30 g of 85% cumene hydroperoxide (CHP) was pumped into the reactor as an initiator using a horizontal flow pump. Air was simultaneously introduced into the reactor at a rate of 1 L / min. During the reaction, the oxygen content in the tail gas was detected to be less than 6 mol%. After 5 h of reaction, the conversion of cumene was 20.61%, the selectivity of CHP was 92.20%, and the selectivity of side reactions was 2.41%.

[0053] After the reaction is completed, a peroxidation reaction liquid is obtained; the peroxidation reaction liquid is subjected to a first-stage alkali wash (the alkali solution is a sodium hydroxide aqueous solution with a concentration of 32 wt%) and a two-stage water wash, and then the CHP stream is concentrated. After the CHP concentration reaches 35.62%, it enters the epoxidation reaction process;

[0054] The epoxidation reaction was carried out in a fixed-bed reactor containing 100 ml of a commercially available titanium silicalite catalyst. A 35.62% CHP solution mixed with propylene was introduced into the fixed-bed reactor. The molar ratio of propylene to CHP was 5. The CHP solution feed rate was 2.5 ml / min. The reaction temperature was 70° C., the reaction pressure was 5 MPaG, and an epoxidation reaction solution was obtained after the reaction. The selectivity of propylene oxide in the epoxidation reaction was 96.31%.

[0055] The epoxidation reaction liquid is subjected to a distillation separation process to separate propylene oxide, and the remainder is a cumene solution of α,α-dimethylbenzyl alcohol, wherein the α,α-dimethylbenzyl alcohol content is 32%. This material is fed into a hydrogenolysis reactor for hydrogenolysis reaction to obtain cumene;

[0056] The reactor used for the hydrogenolysis reaction is a fixed-bed reactor. 80 ml of a commercially available copper-zinc oxide catalyst is loaded in the reactor. A material containing α,α-dimethylbenzyl alcohol is mixed with hydrogen and then introduced into the reactor. The molar ratio of α,α-dimethylbenzyl alcohol to hydrogen is 1:6. The feed rate of the material containing α,α-dimethylbenzyl alcohol is 2 ml / min. The reaction temperature is 190° C., the reaction pressure is 2.5 MPaG, and the reaction obtains a hydrogenolysis reaction liquid.

[0057] The hydrogenolysis reaction liquid undergoes simple phase separation to obtain an oil phase, which enters a distillation de-weighting tower to remove heavy components. The distillation de-weighting tower has 20 theoretical plates and operates at atmospheric pressure with a reflux ratio of 0.2. The recombinant fraction from the bottom of the de-weighting tower enters the waste oil system, and the fraction from the top of the de-weighting tower enters the feed of the distillation de-lighting tower.

[0058] The distillation and lightness removal tower is operated under negative pressure, the pressure is 40KPaA, the theoretical plate number of the distillation and lightness removal tower is 30, the reflux ratio is 4, the bottom temperature of the lightness removal tower is 124°C, and the bottom of the tower obtains the separated recycled isopropylbenzene.

[0059] The recycled isopropyl benzene undergoes an alkaline washing process (the alkaline solution is a 32wt% sodium hydroxide aqueous solution), the oil-water mass ratio of the alkaline washing is 1:0.1, the alkaline washing temperature is 35°C, the pH value of the alkaline washing aqueous phase is 12.0, until the cyclohexanol content in the recycled isopropyl benzene after alkaline washing is 76ppm, the phenol content is 5ppm, and the purity of the isopropyl benzene is 98.57%.

[0060] Propylene oxide was prepared under the same conditions as those for the aforementioned preparation of propylene oxide (the difference being that the amount of the starting raw material cumene was reduced to 580 g, the cyclohexanol content in the recycled cumene used was 76 ppm, the phenol content was 5 ppm, and the cumene purity was 98.57%). The conversion rate of cumene in the peroxidation reaction was 20.92%, the selectivity of CHP was 92.26%, the side reaction selectivity was 2.51%, and the selectivity of propylene oxide in the epoxidation reaction was 96.05%.

[0061] Comparative Example 1:

[0062] 600 g of cumene was added to a 1000 ml reactor, and the temperature was raised to 103° C. 30 g of 85% cumene hydroperoxide (CHP) was pumped into the reactor using a horizontal flow pump as an initiator. Air was simultaneously introduced into the reactor at a rate of 1 L / min. During the reaction, the oxygen content in the tail gas was detected to be less than 6 mol%. After 5 h of reaction, the conversion of cumene was 20.37%, the selectivity of CHP was 92.87%, and the selectivity of side reactions was 2.67%.

[0063] After the reaction is completed, a peroxidation reaction liquid is obtained; the peroxidation reaction liquid is subjected to a primary alkali wash (the alkali solution is a sodium hydroxide aqueous solution with a concentration of 32 wt%) and a two-stage water wash, and then the CHP material is concentrated. After the CHP concentration reaches 35.87%, it enters the epoxidation reaction process;

[0064] The epoxidation reaction was carried out in a fixed-bed reactor containing 100 ml of a commercially available titanium silicalite catalyst. A 35.87% CHP solution mixed with propylene was introduced into the fixed-bed reactor. The molar ratio of propylene to CHP was 4.8. The feed rate of the CHP solution was 2.5 ml / min. The reaction temperature was 72° C., the reaction pressure was 5 MPaG, and an epoxidation reaction solution was obtained after the reaction. The selectivity of the propylene oxide in the epoxidation reaction was 96.35%.

[0065] The epoxidation reaction liquid is subjected to a distillation separation process to separate propylene oxide, and the remainder is a cumene solution of α,α-dimethylbenzyl alcohol, wherein the α,α-dimethylbenzyl alcohol content is 30%. This material is fed into a hydrogenolysis reactor for hydrogenolysis reaction;

[0066] The reactor used for the hydrogenolysis reaction is a fixed-bed reactor. 80 ml of a commercially available copper-zinc oxide catalyst is loaded in the reactor. A material containing α,α-dimethylbenzyl alcohol is mixed with hydrogen and then introduced into the reactor. The molar ratio of α,α-dimethylbenzyl alcohol to hydrogen is 1:8. The feed rate of the material containing α,α-dimethylbenzyl alcohol is 2 ml / min. The reaction temperature is 178° C., the reaction pressure is 2.5 MPaG, and the reaction obtains a hydrogenolysis reaction liquid.

[0067] The hydrogenolysis reaction liquid undergoes simple phase separation to obtain an oil phase, which enters a distillation de-weighting tower to remove heavy components. The distillation de-weighting tower has 15 theoretical plates and operates at atmospheric pressure with a reflux ratio of 0.5. The recombinant fraction from the bottom of the de-weighting tower enters the waste oil system, and the fraction from the top of the de-weighting tower enters the feed of the distillation de-lighting tower.

[0068] The distillation lightness removal tower is operated under negative pressure, the pressure is 25KPaA, the theoretical plate number of the distillation lightness removal tower is 28, the reflux ratio is 5, the bottom temperature of the lightness removal tower is 125°C, and the bottom of the tower obtains the recycled isopropylbenzene after separation.

[0069] The recycled isopropyl benzene undergoes an alkali washing process (the alkali solution is a 32wt% sodium hydroxide aqueous solution), the oil-water mass ratio of the alkali washing is 1:0.1, the alkali washing temperature is 50°C, the pH value of the alkali washing aqueous phase is 12, until the cyclohexanol content in the recycled isopropyl benzene in the oil phase after alkali washing is 656ppm, the phenol content is 10ppm, and the purity of the isopropyl benzene is 98.91%.

[0070] Propylene oxide was prepared under the same conditions as those for the aforementioned preparation of propylene oxide (the difference being that the amount of the starting raw material cumene was reduced to 586 g, the cyclohexanol content in the recycled cumene used was 656 ppm, the phenol content was 10 ppm, and the purity of the cumene was 98.91%). The conversion rate of cumene in the peroxidation reaction was 20.05%, the selectivity of CHP was 90.16%, the side reaction selectivity was 3.78%, and the selectivity of propylene oxide in the epoxidation reaction was 94.05%.

[0071] Comparative Example 2:

[0072] 600 g of cumene was added to a 1000 ml reactor, and the temperature was raised to 104° C. 30 g of 85% cumene hydroperoxide (CHP) was pumped into the reactor using a horizontal flow pump as an initiator. Air was simultaneously introduced into the reactor at a rate of 1 L / min. During the reaction, the oxygen content in the tail gas was detected to be less than 6 mol%. After 5 h of reaction, the conversion of cumene was 20.43%, the selectivity of CHP was 92.67%, and the selectivity of side reactions was 2.54%.

[0073] After the reaction is completed, a peroxidation reaction liquid is obtained; the peroxidation reaction liquid is subjected to a first-stage alkali wash (the alkali solution is a sodium hydroxide aqueous solution with a concentration of 32 wt%) and a two-stage water wash, and then the CHP stream is concentrated. After the CHP concentration reaches 33.24%, it enters the epoxidation reaction process;

[0074] The epoxidation reaction was carried out in a fixed-bed reactor loaded with 100 ml of a commercially available titanium silicalite catalyst. A 33.24% CHP solution mixed with propylene was introduced into the fixed-bed reactor. The molar ratio of propylene to CHP was 5.0. The CHP solution was fed at a rate of 2.5 ml / min. The reaction temperature was 76° C., and the reaction pressure was 5 MPaG. After completion of the reaction, an epoxidation reaction solution was obtained. The selectivity of the propylene oxide in the epoxidation reaction was 96.17%.

[0075] The epoxidation reaction liquid is subjected to a distillation separation process to separate propylene oxide, and the remainder is a cumene solution of α,α-dimethylbenzyl alcohol, wherein the α,α-dimethylbenzyl alcohol content is 32.2%. This material is fed into a hydrogenolysis reactor for hydrogenolysis reaction;

[0076] The reactor used for the hydrogenolysis reaction is a fixed-bed reactor. 80 ml of a commercially available copper-zinc oxide catalyst is loaded in the reactor. A material containing α,α-dimethylbenzyl alcohol is mixed with hydrogen and then introduced into the reactor. The molar ratio of α,α-dimethylbenzyl alcohol to hydrogen is 1:6. The feed rate of the material containing α,α-dimethylbenzyl alcohol is 2 ml / min. The reaction temperature is 170° C., the reaction pressure is 2.5 MPaG, and the reaction obtains a hydrogenolysis reaction liquid.

[0077] The hydrogenolysis reaction liquid undergoes simple phase separation to obtain an oil phase, which is then fed into a distillation de-weighting tower to remove heavy components. The de-weighting tower has 10 theoretical plates and operates at atmospheric pressure with a reflux ratio of 0.2. The recombinant fraction from the bottom of the de-weighting tower enters the waste oil system, while the fraction from the top of the de-weighting tower enters the feed of the distillation de-lighting tower.

[0078] The distillation lightness removal tower is operated under negative pressure, the pressure is 25KPaA, the theoretical plate number of the distillation lightness removal tower is 20, the reflux ratio is 3, the bottom temperature of the lightness removal tower is 127°C, and the bottom of the tower obtains the recycled isopropylbenzene after separation.

[0079] The recycled isopropyl benzene undergoes an alkali washing process (the alkali solution is a 32wt% sodium hydroxide aqueous solution), the oil-water mass ratio of the alkali washing is 1:0.1, the alkali washing temperature is 50°C, the pH value of the alkali washing aqueous phase is 13.1, and the cyclohexanol content in the oil phase recycled isopropyl benzene after alkali washing is 1207ppm, the phenol content is 1ppm, and the purity of the isopropyl benzene is 98.76%.

[0080] Propylene oxide was prepared under the same conditions as those for the aforementioned preparation of propylene oxide (the difference being that the amount of the starting raw material cumene was reduced to 582 g, the cyclohexanol content in the recycled cumene used was 1207 ppm, the phenol content was 1 ppm, and the purity of the cumene was 98.76%). The conversion rate of cumene in the peroxidation reaction was 20.05%, the selectivity of CHP was 90.09%, the side reaction selectivity was 3.88%, and the selectivity of propylene oxide in the epoxidation reaction was 94.50%.

[0081] Comparative Example 3:

[0082] 600 g of cumene was added to a 1000 ml reactor, and the temperature was raised to 102° C. 30 g of 85% cumene hydroperoxide (CHP) was pumped into the reactor as an initiator using a horizontal flow pump. Air was simultaneously introduced into the reactor at a rate of 1 L / min. During the reaction, the oxygen content in the tail gas was detected to be less than 6 mol%. After 5 h of reaction, the conversion of cumene was 20.45%, the selectivity of CHP was 92.87%, and the selectivity of side reactions was 2.52%.

[0083] After the reaction is completed, a peroxidation reaction liquid is obtained; the peroxidation reaction liquid is subjected to a first-stage alkali wash (the alkali solution is a sodium hydroxide aqueous solution with a concentration of 32 wt%) and a two-stage water wash, and then the CHP stream is concentrated. After the CHP concentration reaches 35.87%, it enters the epoxidation reaction process;

[0084] The epoxidation reaction was carried out in a fixed-bed reactor containing 100 ml of a commercially available titanium silicalite catalyst. A 35.87% CHP solution mixed with propylene was introduced into the fixed-bed reactor. The molar ratio of propylene to CHP was 5. The CHP solution feed rate was 2.5 ml / min. The reaction temperature was 75° C., the reaction pressure was 5.8 MPaG, and an epoxidation reaction solution was obtained after the reaction. The selectivity of propylene oxide in the epoxidation reaction was 96.34%.

[0085] The epoxidation reaction liquid is subjected to a distillation separation process to separate propylene oxide, and the remainder is a cumene solution of α,α-dimethylbenzyl alcohol, wherein the α,α-dimethylbenzyl alcohol content is 30%. This material is fed into a hydrogenolysis reactor for hydrogenolysis reaction to obtain cumene;

[0086] The reactor used for the hydrogenolysis reaction is a fixed-bed reactor. 80 ml of a commercially available copper-zinc oxide catalyst is loaded in the reactor. A material containing α,α-dimethylbenzyl alcohol is mixed with hydrogen and then introduced into the reactor. The molar ratio of α,α-dimethylbenzyl alcohol to hydrogen is 1:8. The feed rate of the material containing α,α-dimethylbenzyl alcohol is 2 ml / min. The reaction temperature is 175° C., the reaction pressure is 2.5 MPaG, and the reaction obtains a hydrogenolysis reaction liquid.

[0087] The hydrogenolysis reaction liquid undergoes simple phase separation to obtain an oil phase, which enters a distillation de-weighting tower to remove heavy components. The de-weighting tower has four theoretical plates and operates at atmospheric pressure with a reflux ratio of 0.07. The recombinant fraction from the de-weighting tower kettle enters the waste oil system, while the fraction from the top of the de-weighting tower enters the feed of the distillation de-lighting tower.

[0088] The distillation lightness removal tower is operated under negative pressure, the pressure is 65KPaA, the theoretical plate number of the distillation lightness removal tower is 4, the reflux ratio is 0.08, the bottom temperature of the lightness removal tower is 141°C, and the bottom of the tower obtains the recycled isopropylbenzene after separation.

[0089] The recycled isopropyl benzene undergoes an alkaline washing process (the alkaline solution is a 32wt% sodium hydroxide aqueous solution), the oil-to-water mass ratio of the alkaline washing is 1:0.1, the alkaline washing temperature is 50°C, and the pH value of the alkaline washing aqueous phase is 13.5; the cyclohexanol content in the recycled isopropyl benzene after alkaline washing is 1345ppm, the phenol content is 15ppm, and the purity of the isopropyl benzene is 98.22%.

[0090] Propylene oxide was prepared under the same conditions as those for the aforementioned preparation of propylene oxide (the difference being that the amount of the starting raw material cumene was reduced to 582 g, the cyclohexanol content in the recycled cumene used was 1345 ppm, the phenol content was 15 ppm, and the purity of the cumene was 98.22%). The conversion rate of cumene in the peroxidation reaction was 19.93%, the selectivity of CHP was 90.05%, the side reaction selectivity was 4.02%, and the selectivity of propylene oxide in the epoxidation reaction was 93.23%.

[0091] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be considered within the scope of protection of the present invention.

Claims

1. A method for recycling cumene in the process of preparing propylene oxide by cumene co-oxidation, characterized in that: The cyclohexanol content in the recycled cumene is controlled to be 2-1000 ppm, and the mass ratio of cyclohexanol to phenol is (1-100):

2.

2. The method according to claim 1, characterized in that The cyclohexanol content in the recycled cumene is controlled to be 10-300 ppm, and the mass ratio of cyclohexanol to phenol is (2-50):

2.

3. A method for recycling cumene in the process of preparing propylene oxide by cumene co-oxidation, comprising: Cumene reacts with oxygen to produce cumene hydroperoxide, cumene hydroperoxide reacts with propylene to produce propylene oxide and α,α-dimethylbenzyl alcohol, α,α-dimethylbenzyl alcohol reacts with hydrogen in the presence of a hydrogenolysis catalyst to produce cumene, and then cumene in the hydrogenolysis reaction liquid is separated by distillation, and the separated cumene is then washed with alkali before being applied; The cyclohexanol content in the recycled cumene after alkali washing is controlled to be 2-1000 ppm, and the mass ratio of cyclohexanol to phenol is (1-100):

2.

4. The method according to claim 3, characterized in that: The cyclohexanol content in the recycled cumene after alkali washing is controlled to be 10-300 ppm, and the mass ratio of cyclohexanol to phenol is (2-50):

2.

5. The method according to claim 3 or 4, characterized in that: The pressure of the reaction of cumene and oxygen is 0-0.5 MPaG and the temperature is 90-110°C.

6. The method according to any one of claims 3 to 5, characterized in that: The pressure of the reaction of cumene hydroperoxide and propylene is 3.5-8 MPaG and the temperature is 40-120°C.

7. The method according to any one of claims 3 to 6, characterized in that: The pressure of the reaction of α,α-dimethylbenzyl alcohol and hydrogen is 1.5-3.0 MPaG, the temperature is 130-200°C, and the molar ratio of the two is 1:5-14.

8. The method according to any one of claims 3 to 7, characterized in that: The hydrogenolysis reaction liquid is first processed by a distillation and de-heavy tower, and the top stream of the de-heavy tower is then processed by a distillation and de-light tower, and the separated isopropylbenzene is obtained in the kettle of the de-light tower. The operating process conditions of the de-heavy tower include: operating at normal pressure, the number of theoretical plates of the distillation tower is 5 to 30, and the reflux ratio is 0.1 to 5; the operating process conditions of the de-light tower include: operating under negative pressure, the pressure is 20 to 60 KPaA, the number of theoretical plates of the distillation tower is 5 to 35, and the reflux ratio is 1 to 10.