Method for preparing propylene glycol from vinyl acetate and application of propylene glycol

Abstract

The invention provides a method for preparing propylene glycol from vinyl acetate and application of the propylene glycol. Vinyl acetate, synthesis gas and a first catalyst are subjected to a contact reaction in a hydroformylation reaction unit, part of hydroformylation reaction products are cooled and then returned to control the reaction temperature, and crude acetoxypropionaldehyde, the first catalyst and a solvent or a mixture thereof are separated from the other part of the reaction products under reduced pressure for recycling; the crude acetoxypropionaldehyde and hydrogen are subjected to a contact reaction on a second catalyst, a hydrogenation product is cooled, part of the product is recycled as a solvent, the other part of the product is subjected to a contact reaction with a third catalyst, an organic phase and the catalyst obtained after separation are recycled, and an obtained water phase is fed into a refining unit to sequentially separate 1, 2-propylene glycol, 1, 3-propylene glycol and acetic acid products. The method is safer in raw materials, simple in process, easy to operate, diversified in product composition and high in market adaptability.

Description

Technical Field

[0001] The invention belongs to the field of propylene glycol preparation, and specifically relates to a method for preparing propylene glycol from vinyl acetate and application thereof. Background Art

[0002] Polytrimethylene terephthalate (PTT) synthesized from 1,3-propylene glycol is a new polyester material that combines the high performance of polyethylene terephthalate (PET) and the easy processing of polybutylene terephthalate (PBT). The current mature industrial processes all have their own shortcomings. The raw material acrolein for the acrolein hydration hydrogenation process developed by Evonik (formerly Degussa) in Germany is highly toxic, flammable and explosive, difficult to store and transport, and difficult to obtain at a high price. The hydroformylation ethylene oxide (EO) process developed by Shell requires high-pressure equipment, high technical difficulty, complex catalytic system, harsh and unstable process, and difficult to control the reaction. The bio-enzyme catalysis method developed by Du Pont has low production efficiency and complex purification process. Therefore, the process of synthesizing propylene glycol and hydroxypropionic acid compounds with vinyl acetate hydroformylation as the key step has been widely studied in recent years, and the preparation technology of its catalyst has become increasingly mature. In this process, vinyl acetate is first hydroformylated to produce the intermediate product acetoxypropionaldehyde, which is then hydrogenated to produce acetoxypropanol, and then hydrolyzed to produce 1,3-propylene glycol and 1,2-propylene glycol, with acetic acid as a by-product.

[0003] Using vinyl acetate and synthesis gas as raw materials, a hydroformylation reaction is carried out under the action of a hydroformylation catalyst to obtain crude acetoxypropionaldehyde. Through a hydrogenation catalyst, hydrogen reacts with the acetoxypropionaldehyde therein to obtain acetoxypropanol, which is then hydrolyzed to obtain crude propylene glycol. Further refining obtains high-purity 1,2-propylene glycol and 1,3-propylene glycol products, and produces acetic acid as a by-product. This method has safer raw materials, simple processes, easy operation, diverse product compositions, and strong market adaptability. Summary of the invention

[0004] The invention provides a method for preparing propylene glycol by taking vinyl acetate as a raw material. The method has safer raw materials, simple process, easy operation, diverse product composition and strong market adaptability.

[0005] One of the objects of the present invention is to provide a method for preparing propylene glycol from vinyl acetate, comprising: subjecting vinyl acetate and synthesis gas to a hydroformylation reaction to separate crude acetoxypropionaldehyde, subjecting the obtained crude acetoxypropionaldehyde to a hydrogenation reaction with hydrogen and a hydrolysis reaction with water in sequence to separate water, 1,2-propylene glycol and 1,3-propylene glycol, wherein after the hydroformylation reaction, part of the hydroformylation product is cooled and returned to the hydroformylation reaction, and after the hydrogenation reaction, part of the hydrogenation reaction product is cooled and returned to the hydrogenation reaction.

[0006] According to the present invention, the method for preparing propylene glycol from vinyl acetate specifically comprises the following steps:

[0007] (1) contacting vinyl acetate and synthesis gas with a first catalyst solution C1 to carry out a hydroformylation reaction to obtain a gas phase component G1 and a liquid phase product P1, and the gas phase component G1 is discharged;

[0008] (2) dividing the liquid product P1 into two parts, wherein one part of the liquid product P1-1 is cooled and then returned to the hydroformylation reaction, and the remaining liquid product P1-2 is depressurized and separated to obtain the first catalyst and solvent or a mixture thereof and crude acetoxypropionaldehyde, and the first catalyst and solvent or a mixture thereof are returned to the hydroformylation reaction;

[0009] (3) contacting the crude acetoxypropanal obtained in step (2) with hydrogen and a second catalyst C2 for a hydrogenation reaction to obtain a gaseous component G2 and a liquid product P2 containing acetoxypropanol, wherein the gaseous component G2 is discharged;

[0010] (4) dividing the acetoxypropanol-containing liquid product P2 into two parts, cooling one part of the liquid product P2-1 and returning it to the hydrogenation reaction, and contacting the remaining liquid product P2-2 with water and the third catalyst solution C3 for hydrolysis reaction, and separating after the hydrolysis reaction to obtain the third catalyst and solvent or a mixture thereof, and the hydrolysis reaction product P3;

[0011] (5) The hydrolysis reaction product P3 is subjected to distillation treatment to obtain water, 1,2-propylene glycol, 1,3-propylene glycol and acetic acid.

[0012] According to the present invention, in step (1) of the method for preparing propylene glycol from vinyl acetate:

[0013] The synthesis gas may be any synthesis gas of various specifications commonly used in the art, for example, the synthesis gas contains hydrogen and carbon monoxide, preferably, the molar ratio of hydrogen to carbon monoxide is (0.5-5):1, preferably (0.5-2):1; in a continuous industrial production process, hydrogen may be optionally introduced into the hydroformylation reaction according to the gas composition of the synthesis gas, so as to adjust the ratio of hydrogen to carbon monoxide in the synthesis gas within the above range;

[0014] The first catalyst may be a hydroformylation catalyst commonly used in the art. For example, the first catalyst is selected from at least one of compounds containing metal rhodium and / or cobalt, and may be a compound and / or complex of rhodium and / or cobalt commonly used in the art. The catalyst may be used alone without a ligand and a co-catalyst, and without adding a reaction accelerator. Preferably, the first catalyst is at least one of octacarbonyl cobalt and L-coordinated tricarbonyl hydride rhodium (HRh(CO)3L);

[0015] The molar ratio of vinyl acetate to synthesis gas is 1:(1-20), preferably 1:(1-10), wherein the molar amount of synthesis gas S1 is calculated based on the total molar amount of hydrogen and carbon monoxide therein;

[0016] The amount of the first catalyst is within the commonly used amount range in the art and can be adjusted within a wide range. For example, the molar ratio of the vinyl acetate to the first catalyst solution C1 is (1-10):1, preferably (1-8):1, wherein the first catalyst solution C1 is calculated based on the total molar amount of the first catalyst and the solvent;

[0017] The content of the first catalyst in the first catalyst solution C1 can be adjusted within a wide range. For example, in the first catalyst solution C1, the content of the first catalyst is 1 to 20 wt %, preferably 10 to 20 wt %;

[0018] The solvent in the first catalyst solution C1 is an acyloxypropionaldehyde compound, preferably acetoxypropionaldehyde, such as 3-acetoxypropionaldehyde, or a mixture of 2-acetoxypropionaldehyde and 3-acetoxypropionaldehyde, wherein the mixture of 2-acetoxypropionaldehyde and 3-acetoxypropionaldehyde can be a crude product of a hydroformylation reaction; using the crude product of a hydroformylation reaction as a solvent can avoid the introduction of other substances, improve the separation efficiency of the product and the catalyst solution, and improve the recovery rate;

[0019] The hydroformylation reaction may be carried out using a reactor commonly used in the art. Preferably, the hydroformylation reaction may be carried out using at least one autoclave reactor. When multiple reactors are used, the reactors may be connected in series or in parallel.

[0020] The hydroformylation reaction can adopt the hydroformylation reaction conditions commonly used in the prior art. For example, the conditions of the hydroformylation reaction are: reaction temperature of 50-150° C., reaction pressure of 0.5-8 MPa, and reaction time of 30-180 min; preferably, the reaction temperature is 80-130° C., reaction pressure is 1-7.5 MPa, and reaction time is 30-120 min.

[0021] According to the present invention, in step (2) of the above method for preparing propylene glycol from vinyl acetate:

[0022] The proportion of the liquid phase returned to the hydroformylation reaction can be adjusted within a wide range. For example, the liquid phase product P1-1 returned to the hydroformylation reaction is 10 to 90% of the total amount of the liquid phase product P1, preferably 10 to 50%; the temperature of the liquid phase product P1-1 after cooling is 20 to 100° C., preferably 40 to 100° C., so as to serve as a coolant to control the temperature of the hydroformylation reaction;

[0023] The pressure reduction method of the liquid product P1-2 can be a commonly used pressure reduction method in the art, preferably a two-stage pressure reduction method, and the pressure of the liquid product P1-2 after pressure reduction is 0.5 to 2.5 MPa, preferably 0.5 to 2 MPa;

[0024] The separation operation after depressurization can adopt the separation operation process commonly used in the art, such as separation by flash evaporation, or the unreacted synthesis gas and liquid product can be separated by alternately performing depressurization and flash evaporation;

[0025] The first catalyst and the solvent or a mixture thereof can be returned to the hydroformylation reaction in the form of a mixture comprising the first catalyst and the solvent, or the first catalyst and the solvent can be separated and then returned to the hydroformylation reaction separately. For example, an oxygen-containing gas (such as air) is introduced into the mixture comprising the first catalyst and the solvent, and the catalyst and the liquid phase are separated by centrifugation. The liquid phase is separated by distillation and then circulated to the hydroformylation reaction as a solvent.

[0026] According to the present invention, in step (3) of the above method for preparing propylene glycol from vinyl acetate:

[0027] The molar ratio of the crude acetoxypropionaldehyde to hydrogen is 1:(1-20), preferably 1:(1-10), wherein the crude acetoxypropionaldehyde is calculated based on the molar amount of acetoxypropionaldehyde in the crude acetoxypropionaldehyde, and the acetoxypropionaldehyde includes 2-acetoxypropionaldehyde and 3-acetoxypropionaldehyde;

[0028] The hydrogenation reaction may be carried out using a hydrogenation reactor commonly used in the art, for example, the reactor for the hydrogenation reaction may be a fixed bed reactor or a tank reactor;

[0029] The second catalyst comprises a carrier and a loaded metal active component. Preferably, the carrier is selected from at least one of alumina and carbon powder, and the metal active component is a component containing at least one of platinum, palladium, ruthenium, rhodium, lanthanum, rhenium and nickel. When the hydrogenation reaction reactor is a fixed bed reactor, the second catalyst is a catalyst with γ-alumina as a carrier and loaded with at least one active component of platinum, palladium, ruthenium, rhodium, lanthanum and rhenium. The material space velocity of the fixed bed reactor is 0.05 to 15 h -1 , preferably 0.05~10h -1When the reactor for the hydrogenation reaction is a tank reactor, the second catalyst is a powder catalyst with γ-alumina or carbon powder as a carrier and loaded with an active component containing at least one of platinum, palladium, ruthenium, rhodium and nickel, or a Raney nickel catalyst composed of fine nickel-aluminum alloy grains with a porous structure, and the molar amount of the second catalyst is 0.5-10% of the molar amount of acetoxypropionaldehyde in the crude acetoxypropionaldehyde, preferably 0.5-5%, and the acetoxypropionaldehyde includes 2-acetoxypropionaldehyde and 3-acetoxypropionaldehyde;

[0030] The hydrogenation reaction can adopt the hydrogenation reaction conditions disclosed in the art. For example, the conditions of the hydrogenation reaction are: reaction temperature of 60-110° C., reaction pressure of 2-10 MPa, and reaction time of 30-180 min; preferably, the reaction temperature is 60-100° C., reaction pressure is 2-8 MPa, and reaction time is 30-120 min.

[0031] According to the present invention, in step (4) of the above method for preparing propylene glycol from vinyl acetate:

[0032] The proportion of the liquid phase returned to the hydrogenation reaction can be adjusted within a wide range. For example, the liquid phase product P2-1 returned to the hydrogenation reaction is 10 to 90% of the total weight of the liquid phase product P2, preferably 10 to 50%; the temperature of the liquid phase product P2-1 after cooling is 20 to 100° C., preferably 40 to 100° C., so as to serve as a coolant to control the temperature of the hydrogenation reaction;

[0033] The third catalyst is selected from at least one of an acidic cation exchange resin and a chelated ion exchange resin, wherein the acidic cation exchange resin and the chelated ion exchange resin are not particularly limited, and the acidic cation exchange resin and the chelated ion exchange resin commonly used in the prior art can be used. Preferably, the third catalyst is selected from at least one of an acidic cation exchange resin, for example, a sulfonic acid type ion exchange resin;

[0034] The solvent in the third catalyst solution C3 is a mixed solvent of water and an organic solvent; wherein the organic solvent is selected from at least one of benzene and toluene, preferably toluene; the ratio of water to organic solvent in the mixed solvent is not particularly limited and can be adjusted within a wide range, for example, in the third catalyst solution C3, water accounts for 10 to 90 wt % of the total weight of the solvent, preferably 30 to 70 wt %;

[0035] The mass ratio of the liquid product P2-2 to the solvent in the third catalyst solution C3 is 1:(0.5-50), preferably 1:(0.5-30);

[0036] The mass ratio of acetoxypropanol in the liquid product P2-2 to the third catalyst in the third catalyst solution C3 is 1:(0.005-0.2), preferably 1:(0.005-0.15);

[0037] The hydrolysis reaction can adopt the hydrolysis process conditions commonly used in the prior art, for example, the conditions of the hydrolysis reaction are: temperature of 50-120° C., pressure of 0-1 MPa, and reaction time of 5-120 min; preferably, the temperature is 50-100° C., pressure of 0.1-0.5 MPa, and reaction time of 5-30 min;

[0038] The separation method after the hydrolysis reaction can adopt the separation treatment process commonly used in the art, for example, it can be at least one of distillation separation, membrane separation, and phase separation, preferably phase separation; the separated third catalyst and solvent or their mixture is returned to the hydrolysis reaction for recycling.

[0039] According to the present invention, in step (5) of the above method for preparing propylene glycol from vinyl acetate:

[0040] The distillation can adopt the distillation treatment process commonly used in the art, such as atmospheric distillation, vacuum distillation, pressure swing distillation, extractive distillation, azeotropic distillation or a combination of the above methods. The distillation conditions adopted can also be the process conditions commonly used in the art. For example, the operating conditions of the distillation are: pressure of 5 to 201 kPa, number of plates of 5 to 60, and reflux ratio of 0.1 to 20; preferably, the pressure is 5 to 151 kPa, the number of plates is 5 to 50, and the reflux ratio is 0.1 to 10; the water obtained from the distillation treatment is returned to the hydrolysis reaction for recycling. Specifically, the hydrolysis reaction product P3 is first separated in a primary separation tower, and a stream rich in water and acetic acid is obtained at the top of the tower, and a stream rich in propylene glycol is obtained at the bottom of the tower. After the propylene glycol-rich stream is sent to a propylene glycol tower for separation, a 1,2-propylene glycol product is obtained at the top of the tower, and a 1,3-propylene glycol product is obtained at the bottom of the tower; a stream rich in water and acetic acid is sent to an extractive distillation tower together with an extractant, and the water obtained at the top of the tower is circulated back to the hydrolysis reaction unit. The solvent-rich and acetic acid stream in the bottom of the tower is sent to an extractant recovery tower for further separation, the extractant obtained in the bottom of the tower is circulated back to the extractive distillation tower, and the acetic acid product is obtained at the top of the tower.

[0041] A second object of the present invention is to provide an application of the method for preparing propylene glycol using vinyl acetate as a raw material in the preparation of propylene glycol.

[0042] The method for preparing propylene glycol from vinyl acetate as a raw material of the present invention can obtain high-purity 1,2-propylene glycol and 1,3-propylene glycol products through hydroformylation reaction, hydrogenation reaction, hydrolysis reaction and refining process in sequence, and produce acetic acid as a by-product. The raw materials of the method are safer, the process is simple, easy to operate, and the product composition is diverse and has strong market adaptability. Each unit of the method mainly uses the intermediate product as a solvent to avoid the introduction of new substances and simplify the subsequent separation steps; water is used as a product of the hydrolysis unit and also as a solvent, which can form a cycle between the hydrolysis unit and the refining unit to reduce material consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The process flow chart of an embodiment of the present invention.

[0044] Description of reference numerals:

[0045] 1-hydroformylation reaction unit; 2-gas-liquid separation unit; 3-hydrogenation reaction unit; 4-hydrolysis reaction unit; 5-refining unit; 6-synthesis gas; 7-vinyl acetate (including catalyst and solvent); 8-hydrogen; 9-third catalyst solution; 10-water; 11-non-condensable gas G1; 12-non-condensable gas G2; 13-first catalyst and solvent or a mixture thereof; 14-reaction product P1-1 circulation; 15-1,2-propylene glycol; 16-1,3-propylene glycol; 17-acetic acid; 18-third catalyst and solvent or a mixture thereof circulation; 19-water circulation; 20-hydrogenation reaction product P2-1 circulation. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with specific embodiments and drawings. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0047] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0048] Example 1

[0049] use Figure 1 The process flow chart in the figure is used to explain the process operations in the continuous production process.

[0050] Vinyl acetate 7, synthesis gas 6 and a first catalyst and solvent mixture 13 (the solvent is 3-acetoxypropionaldehyde, and the amount of rhodium compound in the solution is 15.10% in terms of L-coordinated tricarbonyl hydride rhodium (HRh(CO)3L)) are fed into a hydroformylation reaction unit, wherein the introduction rate of vinyl acetate is 2829 kg / h, the introduction rate of the first catalyst and solvent mixture is 756.9 kg / h, the introduction rate of synthesis gas is 823.25 kg / h (the molar ratio of hydrogen to carbon monoxide in the synthesis gas is 1.23:1), the feed molar ratio of synthesis gas to vinyl acetate in the reactor is maintained at about 1.83:1, the hydroformylation reaction temperature is 120°C, the reaction pressure is 6.5 MPa, the reaction time is 80 min, the proportion of the hydroformylation reaction product P1-1 recycled to the total produced liquid phase P1 is 0.10, and the reaction product P1-1 is cooled to 45°C and then circulated to the hydroformylation reaction unit.

[0051] The liquid phase P1-2 of the hydroformylation reaction product enters the gas-liquid separation unit 2, where it is reduced in pressure to 3.5 MPa and 1.0 MPa in turn through two-stage pressure reduction, and is separated by a separation tower. The separation tower has 23 plates, an operating pressure of 20 KPa, a reflux ratio of 1, and 3644.5 kg of crude acetoxypropionaldehyde product is taken from the top of the tower. 841 kg of a mixture of the first catalyst and the solvent is separated from the bottom of the tower and recycled to the hydroformylation reaction unit 1, wherein the content of the first catalyst is 15.1%.

[0052] The crude acetoxypropionaldehyde product and hydrogen 8 are fed into the hydrogenation reaction unit 3, and reacted on the second catalyst Ni / γ-Al2O3 (nickel content is 23%). The reactor used for the hydrogenation reaction is a fixed bed reactor. The hydrogen volume is 75 kg / h, the hydrogenation reaction temperature is 110°C, the reaction pressure is 6.5 MPa, and the reaction space velocity is 2 h -1 , a part of the product P2-2 in the hydrogenation product P2 is sent to the hydrolysis reaction unit 4, and the proportion of the hydrogenation reaction product P2-1 circulation to the total produced liquid phase P2 is 0.10.

[0053] The hydrogenation product P2-2, water 9, water circulation 19 and the mixture circulation 18 of the third catalyst and the solvent are sent to the hydrolysis reaction unit for hydrolysis reaction, the water supplement amount is 530kg / h, the water circulation amount is 1470kg / h, the circulation amount of the mixture of the third catalyst and the solvent is 2000kg / h, and the third catalyst strong acid styrene cation exchange resin is contained 300kg. The hydrolysis reaction temperature is 80°C, the reaction pressure is 0.3MPa, and the reaction time is 20min. After the hydrolysis product is phase separated, the organic phase (containing the third catalyst) 18 is circulated back to the hydrolysis reaction unit 4, and the aqueous phase (containing the hydrolysis reaction product) P3 is sent to the refining unit 5.

[0054] The aqueous phase P3 obtained by the hydrolysis reaction unit 4 is sent to the refining unit 5 for separation. First, it is separated by the primary separation tower, with an operating pressure of 50kPa, a plate number of 20, and a reflux ratio of 2. A stream rich in water and acetic acid is obtained at the top of the tower, and a stream rich in propylene glycol is obtained in the bottom of the tower. The propylene glycol-rich stream is sent to the propylene glycol tower for separation, with an operating pressure of 50kPa, a plate number of 30, and a reflux ratio of 7. The 1,2-propylene glycol product is obtained at the top of the tower, and the 1,3-propylene glycol product is obtained in the bottom of the tower. The stream rich in water and acetic acid is sent to the extractive distillation tower together with the circulating extractant ε-caprolactam, with an operating pressure of 0.1MPa, a plate number of 40, a reflux ratio of 3, and water 19 is obtained at the top of the tower and circulated back to the hydrolysis reaction unit. The rich solvent and acetic acid stream in the bottom of the tower are sent to the extractant recovery tower, with an operating pressure of 50kPa, a plate number of 8, and a reflux ratio of 2.1. The extractant obtained in the bottom of the tower is circulated back to the extractive distillation tower, and the acetic acid product is obtained at the top of the tower. The refining unit obtains 1124kg / h of 1,2-propylene glycol product, 1086kg / h of 1,3-propylene glycol product, and 1750kg / h of acetic acid product, and the product quality purity reaches 99.5%.

[0055] Example 2

[0056] The process of Example 1 was followed, except that:

[0057] Vinyl acetate 7, synthesis gas 6 and a first catalyst and solvent mixture 13 (the solvent is 3-acetoxypropionaldehyde, and the amount of cobalt compounds in the solution is 13.05% in terms of cobalt octacarbonyl) are fed into a hydroformylation reaction unit, wherein the introduction rate of vinyl acetate is 3200 kg / h, the introduction rate of the first catalyst and solvent mixture is 698.03 kg / h, the feed molar ratio of synthesis gas to vinyl acetate in the reactor is maintained at about 1.86:1, the hydroformylation reaction temperature is 110°C, the reaction pressure is 7.0 MPa, and the proportion of the hydroformylation reaction product P1-1 circulation to the total produced liquid phase P1 is 0.25.

[0058] The liquid phase P1-2 of the hydroformylation reaction product enters the gas-liquid separation unit 2, where it is depressurized to 3.5Mpa and 1.0Mpa in turn through two-stage depressurization. After each depressurization, gas-liquid separation is performed through a flash tank. 300kg / h of air is introduced into the obtained liquid phase component, and the catalyst and liquid phase components are separated by centrifugation. The catalyst is circulated back to the first and second reaction units at 91.08kg / h and 18.66kg / h, respectively. The liquid phase is separated by a rectification tower to obtain 734.22kg of the bottom material of the tower as a solvent, which is circulated back to the first reaction unit at 609.91kg / h and the second reaction unit at 124.31kg / h. The top temperature is 97.6℃, the bottom temperature is 122.0℃, the pressure is 30kPa, the number of plates is 23, and the top reflux ratio is 1. 4127.87 kg of crude acetoxypropionaldehyde product was taken from the top of the tower. After the separation tower had 18 plates, an operating pressure of 25 kPa, and a reflux ratio of 10, 217.79 kg / h of light components and unreacted products were separated from the top of the distillation tower, and 3908.33 kg / h of acetoxypropionaldehyde product was obtained in the bottom of the tower.

[0059] The acetoxypropionaldehyde product and hydrogen 8 are sent to the hydrogenation unit 3, and contacted and reacted on the second catalyst Ni / γ-Al2O3 (nickel content is 28%). The reactor used for the hydrogenation reaction is a fixed bed reactor. The hydrogen amount is 85kg / h, the hydrogenation reaction temperature is 95°C, and the reaction pressure is 6.0MPa. Part of the hydrogenation product P2-2 is sent to the hydrolysis reaction unit 4, and the proportion of the hydrogenation reaction product P2-1 circulation to the total produced liquid phase P2 is 0.10.

[0060] The hydrogenation product P2-2, water 9, water circulation 19 and the mixture circulation 18 of the third catalyst and the solvent are sent to the hydrolysis reaction unit for hydrolysis reaction, the water supplement amount is 710kg / h, the water circulation amount is 1490kg / h, the circulation amount of the mixture of the third catalyst and the solvent is 2500kg / h, the internal catalyst is 350kg, the hydrolysis reaction temperature is 85°C, the reaction pressure is 0.3MPa, and the hydrolysis product is phase separated to obtain an organic phase containing the third catalyst and an aqueous phase containing the hydrolysis reaction product, wherein the organic phase (containing the third catalyst) 18 is circulated back to the hydrolysis reaction unit 4, and the obtained aqueous phase (containing the hydrolysis reaction product) P3 is sent to the refining unit 5.

[0061] The aqueous phase P3 obtained by the hydrolysis reaction unit 4 is sent to the refining unit 5 for separation. First, it is separated by the primary separation tower, with an operating pressure of 50kPa, a plate number of 20, and a reflux ratio of 2. A stream rich in water and acetic acid is obtained at the top of the tower, and a stream rich in propylene glycol is obtained in the bottom of the tower. The propylene glycol-rich stream is sent to the propylene glycol tower for separation, with an operating pressure of 50kPa, a plate number of 30, a reflux ratio of 7, and a 1,2-propylene glycol product is obtained at the top of the tower, and a 1,3-propylene glycol product is obtained in the bottom of the tower. The stream rich in water and acetic acid is sent to the extractive distillation tower together with the circulating extractant, with an operating pressure of 0.1MPa, a plate number of 40, a reflux ratio of 3, and water 19 is obtained at the top of the tower and circulated back to the hydrolysis reaction unit. The rich solvent and acetic acid stream in the bottom of the tower are sent to the extractant recovery tower, with an operating pressure of 50kPa, a plate number of 8, a reflux ratio of 2, and the extractant obtained in the bottom of the tower is circulated back to the extractive distillation tower, and the acetic acid product is obtained at the top of the tower. The refining unit produces 1270kg / h of 1,2-propylene glycol, 1230kg / h of 1,3-propylene glycol and 1974kg / h of acetic acid, with a product quality purity of 99.5%.

[0062] Example 3

[0063] The process of Example 2 is followed, except that:

[0064] Vinyl acetate 7, synthesis gas 6 and a first catalyst and solvent mixture 13 (the solvent is 3-acetoxypropionaldehyde, and the amount of rhodium compound in the solution is 10.03% in terms of L-coordinated tricarbonyl hydride rhodium (HRh(CO)3L)) are fed into a hydroformylation reaction unit, wherein the introduction rate of vinyl acetate is 3200 kg / h, the introduction rate of the first catalyst and solvent mixture is 681.21 kg / h, the introduction rate of synthesis gas is 1010.15 kg / h (the molar ratio of hydrogen to carbon monoxide in the synthesis gas is 1.13:1), the feed molar ratio of synthesis gas to vinyl acetate in the reactor is maintained at about 1.91:1, the hydroformylation reaction temperature is 115°C, the reaction pressure is 6.0 MPa, the reaction time is 70 min, and the proportion of the hydroformylation reaction product P1-1 circulation to the total produced liquid phase P1 is 0.45.

[0065] The liquid phase P1-2 of the hydroformylation reaction product enters the gas-liquid separation unit 2, where it is reduced in pressure to 3.5 MPa and 1.0 MPa in turn through two-stage pressure reduction, and is separated by a separation tower with 23 plates, an operating pressure of 20 kPa, and a reflux ratio of 1. 3873.6 kg of crude acetoxypropionaldehyde product is taken from the top of the tower, and 841 kg of a mixture of the first catalyst and the solvent is separated from the bottom of the tower and recycled to the hydroformylation reaction unit 1, wherein the content of the first catalyst is 10.03%.

[0066] The crude acetoxypropionaldehyde product and hydrogen 8 are sent to the hydrogenation unit 3 for contact reaction on the second catalyst. The hydrogen amount is 85 kg / h, the hydrogenation reaction temperature is 107 ° C, the reaction pressure is 6.0 MPa, and the hydrogenation product is sent to the hydrolysis reaction unit 4. The ratio of the hydrogenation reaction product P2-1 circulation to the total produced liquid phase P2 is 0.40.

[0067] The hydrogenation product P2-2, water 9, water circulation 19 and the mixture circulation 18 of the third catalyst and the solvent are sent to the hydrolysis reaction unit for hydrolysis reaction, the water supplement amount is 530kg / h, the water circulation amount is 1470kg / h, the circulation amount of the mixture of the third catalyst and the solvent is 2000kg / h, the internal catalyst is 350kg, the hydrolysis reaction temperature is 80°C, the reaction pressure is 0.3MPa, the reaction time is 15min, and after the hydrolysis product is phase separated, the organic phase (containing the third catalyst) 18 is circulated back to the hydrolysis reaction unit 4, and the water phase (containing the hydrolysis reaction product) P3 is sent to the refining unit 5.

[0068] The aqueous phase P3 obtained by the hydrolysis reaction unit 4 is sent to the refining unit 5 for separation. First, it is separated by the primary separation tower, with an operating pressure of 50kPa, a plate number of 20, and a reflux ratio of 2. A stream rich in water and acetic acid is obtained at the top of the tower, and a stream rich in propylene glycol is obtained in the bottom of the tower. The propylene glycol-rich stream is sent to the propylene glycol tower for separation, with an operating pressure of 50kPa, a plate number of 30, and a reflux ratio of 7. The 1,2-propylene glycol product is obtained at the top of the tower, and the 1,3-propylene glycol product is obtained in the bottom of the tower. The stream rich in water and acetic acid is sent to the extractive distillation tower together with the circulating extractant, with an operating pressure of 0.1MPa, a plate number of 40, and a reflux ratio of 3. The water 19 obtained at the top of the tower is circulated back to the hydrolysis reaction unit, and the rich solvent and acetic acid stream in the bottom of the tower are sent to the extractant recovery tower, with an operating pressure of 50kPa, a plate number of 8, and a reflux ratio of 2.1. The extractant obtained in the bottom of the tower is circulated back to the extractive distillation tower, and the acetic acid product is obtained at the top of the tower. The refining unit obtains 1273kg / h of 1,2-propylene glycol product, 1232kg / h of 1,3-propylene glycol product, and 1980kg / h of acetic acid product, and the product quality purity reaches 99.5%.

[0069] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for preparing propylene glycol from vinyl acetate, comprising: Vinyl acetate and synthesis gas are subjected to hydroformylation reaction to separate crude acetoxypropionaldehyde, and the obtained crude acetoxypropionaldehyde is subjected to hydrogenation reaction with hydrogen and hydrolysis reaction with water in sequence to separate water, 1,2-propylene glycol and 1,3-propylene glycol, wherein after the hydroformylation reaction, part of the hydroformylation product is cooled and returned to the hydroformylation reaction, and after the hydrogenation reaction, part of the hydrogenation reaction product is cooled and returned to the hydrogenation reaction.

2. The method according to claim 1, characterized in that The method specifically comprises the following steps: (1) contacting vinyl acetate and synthesis gas with a first catalyst solution C1 to carry out a hydroformylation reaction to obtain a gas phase component G1 and a liquid phase product P1, and the gas phase component G1 is discharged; (2) dividing the liquid product P1 into two parts, wherein one part of the liquid product P1-1 is cooled and then returned to the hydroformylation reaction, and the remaining liquid product P1-2 is depressurized and separated to obtain the first catalyst and solvent or a mixture thereof and crude acetoxypropionaldehyde, and the first catalyst and solvent or a mixture thereof are returned to the hydroformylation reaction; (3) contacting the crude acetoxypropanal obtained in step (2) with hydrogen and a second catalyst C2 for a hydrogenation reaction to obtain a gaseous component G2 and a liquid product P2 containing acetoxypropanol, wherein the gaseous component G2 is discharged; (4) dividing the acetoxypropanol-containing liquid product P2 into two parts, cooling one part of the liquid product P2-1 and returning it to the hydrogenation reaction, and contacting the remaining liquid product P2-2 with water and the third catalyst solution C3 for hydrolysis reaction, and separating after the hydrolysis reaction to obtain the third catalyst and solvent or a mixture thereof, and the hydrolysis reaction product P3; (5) The hydrolysis reaction product P3 is subjected to distillation treatment to obtain water, 1,2-propylene glycol, 1,3-propylene glycol and acetic acid.

3. The method according to claim 2, characterized in that In the step (1): The synthesis gas contains hydrogen and carbon monoxide. Preferably, the molar ratio of hydrogen to carbon monoxide in the synthesis gas is (0.5-5):1; and / or, The first catalyst is selected from at least one compound containing metal rhodium and / or cobalt, preferably at least one of octacarbonyl cobalt and L-coordinated tricarbonyl rhodium hydride; and / or, The molar ratio of vinyl acetate to synthesis gas is 1:(1-20), preferably 1:(1-10); and / or, The molar ratio of vinyl acetate to the first catalyst solution C1 is (1-10):1, preferably (1-8):1, wherein the first catalyst solution C1 is calculated based on the total molar amount of the first catalyst and the solvent; and / or, In the first catalyst solution C1, the content of the first catalyst is 1 to 20 wt%, preferably 10 to 20 wt%; and / or, The solvent in the first catalyst solution C1 is an acyloxypropionaldehyde compound, preferably acetoxypropionaldehyde; and / or, The hydroformylation reaction uses at least one autoclave reactor; and / or, The conditions of the hydroformylation reaction are: reaction temperature of 50-150° C., and / or reaction pressure of 0.5-8 MPa, and / or reaction time of 30-180 min; preferably, the reaction temperature is 80-130° C., and / or reaction pressure is 1-7.5 MPa, and / or reaction time of 30-120 min.

4. The method according to claim 2, characterized in that: In the step (2): The liquid product P1-1 returned to the hydroformylation reaction is 10 to 90% of the total amount of the liquid product P1, preferably 10 to 50%; and / or, The temperature of the liquid product P1-1 after cooling is 20 to 100° C., preferably 40 to 100° C.; and / or, The pressure of the liquid product P1-2 after decompression is 0.5 to 2.5 MPa, preferably 0.5 to 2 MPa.

5. The method according to claim 2, characterized in that: In the step (3): The molar ratio of the crude acetoxypropionaldehyde to hydrogen is 1:(1-20), preferably 1:(1-10), wherein the crude acetoxypropionaldehyde is calculated based on the molar amount of acetoxypropionaldehyde therein; and / or, The second catalyst comprises a carrier and a supported metal active component, preferably, the carrier is selected from at least one of alumina and carbon powder; and / or, the metal active component is a component containing at least one of platinum, palladium, ruthenium, rhodium, lanthanum, rhenium and nickel; and / or, The reactor for the hydrogenation reaction is a fixed bed reactor or a tank reactor; and / or, The conditions for the hydrogenation reaction are: a reaction temperature of 60 to 110° C., and / or a reaction pressure of 2 to 10 MPa; preferably, the reaction temperature is 60 to 100° C., and / or the reaction pressure is 2 to 8 MPa.

6. The method according to claim 5, characterized in that When the reactor for the hydrogenation reaction is a fixed bed reactor, the second catalyst is a catalyst with γ-alumina as a carrier and loaded with at least one metal active component selected from platinum, palladium, ruthenium, rhodium, lanthanum and rhenium; and / or the material space velocity of the fixed bed reactor is 0.05 to 15 h -1 , preferably 0.05~10h -1 ;or, When the reactor for the hydrogenation reaction is a kettle reactor, the second catalyst is a catalyst with γ-alumina or carbon powder as a carrier and loaded with a metal active component containing at least one of platinum, palladium, ruthenium, rhodium and nickel, or a Raney nickel catalyst composed of fine nickel-aluminum alloy grains with a porous structure; and / or the molar amount of the second catalyst is 0.5 to 10% of the molar amount of acetoxypropionaldehyde in the crude acetoxypropionaldehyde, preferably 0.5 to 5%.

7. The method according to claim 2, characterized in that: In the step (4): The liquid product P2-1 returned to the hydrogenation reaction is 10 to 90% of the total weight of the liquid product P2, preferably 10 to 50%; and / or, The temperature of the liquid product P2-1 after cooling is 20 to 100° C., preferably 40 to 100° C.; and / or, The third catalyst is selected from at least one of an acidic cation exchange resin and a chelated ion exchange resin, preferably at least one of an acidic cation exchange resin; and / or, The solvent in the third catalyst solution C3 is a mixed solvent of water and an organic solvent; and / or, The mass ratio of the liquid product P2-2 to the solvent in the third catalyst solution C3 is 1:(0.5-50), preferably 1:(0.5-30); and / or, The mass ratio of acetoxypropanol in the liquid product P2-2 to the third catalyst in the third catalyst solution C3 is 1:(0.005-0.2), preferably 1:(0.005-0.15); and / or, The conditions of the hydrolysis reaction are: temperature of 50-120°C, and / or pressure of 0-1 MPa, and / or reaction time of 5-120 min; preferably, temperature of 50-100°C, and / or pressure of 0.1-0.5 MPa, and / or reaction time of 5-30 min; and / or, The separation after the hydrolysis reaction is at least one of distillation separation, membrane separation, and phase separation, preferably phase separation; and / or, The separated third catalyst and solvent or a mixture thereof are returned to the hydrolysis reaction for recycling.

8. The method according to claim 7, characterized in that In the third catalyst solution C3, the organic solvent is selected from at least one of benzene and toluene, preferably toluene; and / or, In the third catalyst solution C3, water accounts for 10 to 90 wt %, preferably 30 to 70 wt %, of the total weight of the solvent.

9. The method according to claim 2, characterized in that: In the step (5): The operating conditions of the distillation are: pressure of 5-201 kPa, and / or, the number of plates is 5-60, and / or, the reflux ratio is 0.1-20; preferably, the pressure is 5-151 kPa, and / or, the number of plates is 5-50, and / or, the reflux ratio is 0.1-10; and / or, The water obtained from the distillation treatment is returned to the hydrolysis reaction for recycling.

10. Use of the method for preparing propylene glycol using vinyl acetate as raw material as claimed in any one of claims 1 to 9 in the preparation of propylene glycol.

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