Method and process device for preparing 1, 3-propylene glycol from propylene

Abstract

The invention relates to the technical field of propylene glycol preparation methods and processes, and discloses a method and a process device for preparing 1, 3-propylene glycol from propylene, and the method for preparing 1, 3-propylene glycol from propylene comprises the following steps: oxidizing propylene to prepare gaseous acrolein, firstly absorbing by using pressurized water to remove heavy component waste gas, and then absorbing by using pressurized water to obtain an acrolein aqueous solution; the method comprises the following steps: carrying out hydration reaction treatment on an acrolein aqueous solution, and then carrying out hydrotreatment twice in sequence to prepare the 1, 3-propylene glycol. The 1, 3-propylene glycol is prepared by using propylene as a raw material, the acrolein aqueous solution is generated in the process, the high-purity acrolein can be obtained without rectification separation, the problems that the high-purity acrolein is easy to polymerize, difficult to store and transport, high in raw material cost and the like can be avoided, and the method has the characteristics of easily available raw materials, short process flow, high acrolein recovery rate, low energy consumption, good economic benefit and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of methods and processes for preparing propylene glycol, and in particular to a method and process device for preparing 1,3-propylene glycol from propylene. Background Art

[0002] 1,3-Propanediol (PDO) is a colorless, viscous, transparent liquid primarily used for polymerization with terephthalic acid to produce poly(trimethylene terephthalate), an excellent polyester material. It can also be used in the synthesis of plasticizers, detergents, preservatives, and emulsifiers. It can also be used as a monomer in polyesters and polyurethanes, replacing 1,4-butanediol and neopentyl glycol in the production of polyol polyesters, and as a carbon chain extender. Small amounts are also used in cosmetics and pharmaceuticals. Currently, common PDO synthesis processes include biological and chemical methods. Chemical methods primarily include the acrolein method (using acrolein as a raw material) and the EO method (using ethylene oxide (EO) as a raw material). The biological method suffers from low raw material conversion, poor selectivity, numerous byproducts, difficulty in separation and purification, large wastewater volumes, high production costs, and limited production scale. The EO method, among other chemical methods, suffers from high temperature and pressure, high equipment investment, and high production costs. The acrolein method also faces challenges with obtaining acrolein as a raw material. Therefore, developing a process for synthesizing 1,3-propanediol using propylene as a raw material is of great research significance.

[0003] Currently, there is relatively little technical research on the process technology of producing PDO directly using propylene as raw material. Summary of the Invention

[0004] To address the technical challenges of prior art processes for directly producing PDO using propylene as a raw material, the present invention provides a method and apparatus for preparing 1,3-propylene glycol from propylene. This method involves oxidizing the raw propylene to produce acrolein, then rapidly quenching and absorbing the raw propylene to remove heavy components such as acrylic acid and acetic acid, then absorbing the acrolein with pressurized water to produce an aqueous acrolein solution. This solution is then subjected to a hydration reaction and two hydrogenation reactions to directly synthesize 1,3-propylene glycol. This combination of rapid absorption and pressurized absorption reduces impurities in the acrolein solution and increases acrolein yield, thereby improving the purity and yield of the final 1,3-propylene glycol.

[0005] An object of the present invention is to provide a method for preparing 1,3-propylene glycol from propylene, comprising: oxidizing propylene to produce gaseous acrolein, first subjecting the gaseous acrolein to rapid cooling and absorption to remove heavy component waste gas, and then subjecting the gaseous acrolein to pressurized water absorption to obtain an aqueous acrolein solution; subjecting the aqueous acrolein solution to a hydration reaction and then to two hydrogenation treatments to produce 1,3-propylene glycol.

[0006] The present invention uses propylene as a raw material to prepare 1,3-propylene glycol, and generates an acrolein aqueous solution in the middle. High-purity acrolein can be obtained without distillation separation, thereby avoiding the problems of easy polymerization of high-purity acrolein, difficulty in storage and transportation, high raw material cost, etc. The present invention has the characteristics of easy availability of raw materials, short process flow, high acrolein recovery rate, low energy consumption, good economic benefits, etc.

[0007] According to a preferred embodiment of the present invention, the method for preparing 1,3-propylene glycol from propylene comprises the following steps:

[0008] S1, subjecting a mixed gas of propylene, air and water vapor to an oxidation reaction to obtain gaseous acrolein;

[0009] S2, gaseous acrolein is rapidly cooled and absorbed to remove heavy component waste gas, and the remaining light component gas is absorbed by pressurized water to obtain acrolein crude liquid;

[0010] S3, subjecting the crude acrolein solution to a second stripping treatment to obtain an acrolein aqueous solution;

[0011] S4, the acrolein aqueous solution is subjected to a hydration reaction, and the hydration product is subjected to two hydrogenation reactions;

[0012] S5. After the hydrogenation product is separated into gas and liquid, the liquid phase is sequentially subjected to light removal treatment, dehydration treatment and heavy removal treatment to obtain 1,3-propylene glycol.

[0013] Step S2: pressurized water absorption is performed at 0.01-2.0 MPaG.

[0014] According to a preferred embodiment of the present invention, the reaction temperature of the oxidation reaction in step S1 is 200-300° C., and the pressure is 0.01 MPaG-0.9 MPaG (gauge pressure).

[0015] According to a preferred embodiment of the present invention, the rapid cooling absorption in step S2 is normal pressure absorption.

[0016] According to a preferred embodiment of the present invention, the quench absorption in step S2 includes water absorption in gas-liquid countercurrent contact; preferably, the gaseous acrolein and the desalted water flow in countercurrent, and the desalted water absorbs the heavy component waste gas in the gaseous acrolein at 5 to 60° C., preferably 8 to 40° C.; and / or,

[0017] The quench absorption is carried out at normal pressure with a gas-liquid ratio of 0.02-0.2:1, preferably 0.04-0.12:1; and / or,

[0018] The heavy component waste gas is subjected to a first stripping treatment, and the acrolein removed by quenching absorption is recovered; preferably, the acrolein recovered by the first stripping treatment is returned to the quenching absorption step; preferably, the pressure of the first stripping treatment is -0.03 MPaG to 0.9 MPaG; and / or,

[0019] The pressure of the pressurized water absorption is 0.01 MPaG to 2.0 MPaG, preferably 0.05 to 1.0 MPaG; and / or,

[0020] The liquid-gas ratio of the absorbed water to the light component gas in the pressurized water absorption is 0.25 to 2.7:1, preferably 0.5 to 1.6:1.

[0021] According to a preferred embodiment of the present invention, the second stripping treatment in step S3 is used to remove light waste gas; preferably, the light waste gas is returned to repeat the pressurized water absorption step; and / or,

[0022] The pressure of the second stripping treatment is 0.01 MPaG to 0.9 MPaG; and / or,

[0023] After the second stripping treatment, the acrolein concentration in the obtained acrolein aqueous solution is 5 to 35 wt %, preferably 8 to 20 wt %.

[0024] In a specific embodiment, the liquid-to-gas ratio in the pressurized water absorption step can be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 1.9, 2.1, 2.3, 2.5, or 2.7. The acrolein concentration after the second stripping treatment can be 5 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 25 wt%, 30 wt%, or 35 wt%. When the acrolein concentration is less than 5 wt%, the energy consumption is too high; when the acrolein concentration is greater than 35 wt%, agglomeration occurs. In a preferred embodiment, the acrolein concentration in the aqueous acrolein solution is 8-20 wt % when the liquid-to-gas ratio of absorbed water to light component gas during pressurized water absorption is 0.5-1.6. Exceeding this range can cause acrylic acid to polymerize, forming flocculent heavy components, or result in high energy consumption. This range reduces the likelihood of acrolein self-polymerization, resulting in low energy consumption and a high PDO yield.

[0025] The quench absorption process of the present invention is carried out under normal pressure. The quench absorption and pressurized water absorption constitute double absorption, while the first and second stripping processes constitute double stripping. The combination of double absorption and double stripping offers advantages such as low impurity content in the acrolein solution, controllable concentration, and high acrolein yield. The present invention employs a quench absorption tower (normal pressure water absorption) using a small amount of fresh desalted water to absorb a small amount of heavy components such as acrylic acid and acetic acid in the acrolein product gas, helping to reduce heavy component impurities in the subsequent acrolein solution. A first acrolein recovery tower (first stripping process) is then used to recover some of the acrolein, thereby improving the acrolein recovery rate. Under pressure (pressurized water absorption), fresh desalted water at a certain temperature is used to absorb acrolein to form a crude acrolein solution. By varying the absorption pressure and temperature, the concentration of the crude acrolein solution can be controlled. The stripping tower (second stripping process) is located after the pressurized water absorption and is used to remove light waste gases such as non-condensable gases from the crude acrolein solution, further removing impurities and improving the purity of the aqueous acrolein solution.

[0026] According to a preferred embodiment of the present invention, the reaction pressure of the hydration reaction treatment in step S4 is 0.0-2.0 MPaG, and the reaction temperature is 25-100° C.; and / or,

[0027] The two hydrotreatments include a first hydrotreatment and a second hydrotreatment; and / or,

[0028] The reaction pressure of the first hydrotreatment is 2-10 MPaG (reactor operating pressure), and the reaction temperature is 25-150° C.; and / or,

[0029] The reaction pressure of the second hydrotreatment is 2-10 MPaG (reactor operating pressure), and the reaction temperature is 50-200° C.; and / or,

[0030] Between the hydration treatment and the two hydrogenation treatments, a distillation separation step is performed to screen out unreacted acrolein and return it to the hydration reaction treatment step.

[0031] According to a preferred embodiment of the present invention, the separation pressure of the gas-liquid separation in step S5 is 2-10 MPaG, and the separation temperature is 50-200° C.; and / or,

[0032] The unreacted hydrogen separated by the gas-liquid separation is returned to the first hydroprocessing step; and / or,

[0033] The pressure of the light removal treatment is -0.10 to 0.5 MPaG; and / or,

[0034] The pressure of the dehydration treatment is -0.10 to 0.5 MPaG; and / or,

[0035] The pressure of the weight removal treatment is -0.10 to 0.5 MPaG; and / or,

[0036] After the weight removal treatment, the product is further subjected to a refining treatment.

[0037] According to a preferred embodiment of the present invention, the waste gas not absorbed by the pressurized water absorption and / or the waste gas from the lightness removal treatment and the waste gas from the refining treatment is subjected to tail gas treatment; preferably, part of the recycle gas generated by the tail gas treatment is used in the propylene oxidation step S1, and the remaining gas is discharged as purge gas; and / or,

[0038] The circulating absorption water obtained from the dehydration reaction is returned to the pressurized water absorption step as absorption water.

[0039] This invention utilizes an exhaust gas treatment and tail gas recycle system to centrally treat the entire system's process tail gases, primarily those from the acrolein absorber, the lightness removal tower, and the PDO refining tower. A portion of the treated tail gases is then recycled to the propylene oxidation system. This process technology not only achieves system tail gas treatment and compliance with emission standards, but also reduces fresh air consumption and air compression energy consumption within the propylene oxidation system.

[0040] The present invention adopts absorption water recycling technology, directly utilizing the water phase obtained from the dehydration tower in the PDO refining system as circulating absorption water for the acrolein absorption tower. This technology only requires one water cycle during the entire process to achieve water recycling, thus simplifying the water recycling process flow and reducing fresh absorption water consumption and wastewater discharge.

[0041] To solve the second object of the present invention: a process device for preparing 1,3-propylene glycol from propylene is provided, comprising a propylene oxidation reactor, a quench absorption tower, a first compressor, an acrolein absorption tower, an acrolein hydration reactor, a first hydrogenation reactor and a second hydrogenation reactor connected in sequence;

[0042] The propylene oxidation reactor is used to oxidize propylene to produce gaseous acrolein;

[0043] The quenching absorption tower is used for quenching and absorbing the heavy component waste gas;

[0044] The first compressor is used to pressurize the acrolein gas entering the acrolein absorption tower;

[0045] The acrolein absorption tower is used for pressurized water absorption to obtain an acrolein aqueous solution;

[0046] The acrolein hydration reactor is used to perform a hydration reaction on the acrolein aqueous solution;

[0047] The first hydrogenation reactor and the second hydrogenation reactor are used for two hydrogenation treatments in sequence.

[0048] According to a preferred embodiment of the present invention, the process device further comprises a first acrolein recovery tower connected to the quenching absorption tower, wherein the first acrolein recovery tower is used to recover acrolein removed by atmospheric pressure water absorption; preferably, the gas phase outlet of the first acrolein recovery tower is connected to the quenching absorption tower, and the liquid phase outlet is used to discharge waste liquid; and / or,

[0049] The system further comprises a stripping tower disposed between the acrolein absorption tower and the acrolein hydration reactor, wherein the stripping tower is used for performing a second stripping treatment. Preferably, the stripping tower inlet is connected to the acrolein absorption tower outlet, the gas phase outlet is connected to the acrolein absorption tower inlet pipeline, and the liquid phase outlet is connected to the acrolein hydration reactor; and / or,

[0050] The system further comprises a second acrolein recovery tower disposed between the acrolein hydration reactor and the first hydrogenation reactor, wherein the second acrolein recovery tower is used for rectifying, separating and screening out unreacted acrolein and returning the unreacted acrolein to the acrolein hydration reactor; and / or,

[0051] It also includes a gas-liquid separator connected to the outlet of the second hydrogenation reactor, the gas-liquid separator is used to separate unreacted hydrogen; preferably, a hydrogen transmission pipeline for returning unreacted hydrogen to the first hydrogenation reactor is provided between the top outlet of the gas-liquid separator and the first hydrogenation reactor;

[0052] It also includes a light removal tower, a dehydration tower and a heavy removal tower which are sequentially arranged after the gas-liquid separator; the light removal tower is used for light removal treatment; the dehydration tower is used for dehydration treatment; and the heavy removal tower is used for heavy removal treatment.

[0053] The invention also comprises a PDO refining tower connected to the deweighting tower, and the PDO refining tower is used for refining the product after the deweighting treatment.

[0054] According to a preferred embodiment of the present invention, a second compressor is provided on the hydrogen transmission pipeline.

[0055] According to a preferred embodiment of the present invention, the process further comprises a tail gas treatment system connected to the acrolein absorption tower, the lightness removal tower, and the PDO refining tower for receiving and treating tail gas; preferably, a circulating gas pipeline for delivering the treated tail gas to the propylene oxidation reactor is connected between the tail gas treatment system and the propylene oxidation reactor; and / or,

[0056] A circulating absorption water delivery pipeline is connected between the dehydration tower and the acrolein absorption tower for delivering water removed from the dehydration tower to the acrolein absorption tower for reuse.

[0057] The present invention provides the following beneficial effects: The method for preparing 1,3-propylene glycol from propylene oxidizes the raw material propylene to produce acrolein, then rapidly cools and absorbs the raw material under normal pressure to remove heavy components such as acrylic acid and acetic acid, absorbs the acrolein under pressurized water to produce an acrolein aqueous solution, and then directly synthesizes 1,3-propylene glycol through a hydration reaction and two hydrogenation reactions. The combination of normal pressure water absorption and pressurized absorption reduces impurities in the acrolein solution and increases the acrolein yield, thereby improving the purity and yield of 1,3-propylene glycol. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 Diagram of the process unit for producing 1,3-propylene glycol from propylene;

[0059] 1-propylene oxidation reactor, 2-quench absorption tower, 3-first acrolein recovery tower, 4-first compressor, 5-acrolein absorption tower, 6-stripping tower, 7-acrolein hydration reactor, 8-second acrolein recovery tower, 9-first hydrogenation reactor, 10-second hydrogenation reactor, 11-gas-liquid separator, 12-second compressor, 13-light removal tower, 14-dehydration tower, 15-heavy removal tower, 16-PDO refining tower, 17-tail gas treatment system. DETAILED DESCRIPTION

[0060] The present invention will be further described below with reference to specific examples, but they do not constitute any limitation to the present invention.

[0061] The liquid-to-gas ratio of the circulating absorption water in the acrolein absorption tower 5 to the bottom gas phase is recorded as the liquid-to-gas ratio; the acrolein yield is the ratio of the acrolein content in the acrolein aqueous solution after the second stripping treatment in the stripping tower 6 to the acrolein content in the acrolein product gas (gaseous acrolein) obtained after oxidation in the propylene oxidation reactor 1.

[0062] Absorption of atmospheric pressure water is carried out in the quench absorption tower 2.

[0063] like Figure 1As shown, propylene is mixed with air, water vapor, and recycle gas before entering propylene oxidation reactor 1. The resulting acrolein product gas, after heat recovery, is then fed to a quench absorption tower 2. A small amount of fresh desalted water is then added to the top of quench absorption tower 2. After gas-liquid countercurrent contact, heavy components in the acrolein product gas, such as acrylic acid and acetic acid, are rapidly absorbed. The absorbed liquid obtained in the bottom of the tower enters a first acrolein recovery tower 3. In this recovery tower, light components such as non-condensable gases and acrolein are stripped from the bottom of the quench absorption tower 2 through distillation and stripping, and the resulting liquid is returned to the quench absorption tower 2, thereby increasing the yield of the acrolein product. The acid-containing waste liquid obtained in the bottom of the tower is then fed to a subsequent waste liquid treatment system. The acrolein product gas from the top of quench absorption tower 2 is pressurized by a first compressor 4 and then fed to an acrolein absorption tower 5. After absorption, a crude acrolein-containing liquid is obtained in the bottom of the tower and fed to a stripping tower 6. After passing through the stripping tower 6, the non-condensable gases and a small amount of acrolein at the top of the tower are returned to the inlet of the first compressor 4. The acrolein aqueous solution obtained in the bottom of the tower is fed to the acrolein hydration reactor 7 for acrolein hydration. The resulting mixture enters the second acrolein recovery tower 8 for distillation separation. The unreacted acrolein obtained at the top of the tower is returned to the acrolein hydration reactor 7. The crude liquid obtained in the bottom of the second acrolein recovery tower 8 enters the first hydrogenation reactor 9 and then the second hydrogenation reactor 10 for a two-stage hydrogenation reaction with hydrogen. The hydrogenated material is then fed to the gas-liquid separator 11 for gas-liquid separation. The majority of the unreacted hydrogen is pressurized by the second compressor 12 and then recycled to the inlet of the first hydrogenation reactor 9. The PDO reaction liquid obtained at the bottom of the gas-liquid separator 11 first enters the lightness removal tower 13 to separate the majority of non-condensable gases, aldehydes, and alcohols that are lighter than water. The bottom liquid is then fed to the dehydration tower 14 for dehydration and separation. After dehydration and separation, the water obtained at the top of the tower is cooled, mixed with fresh desalted water, and returned to the acrolein absorption tower 5, achieving water recycling. The bottom liquid of the dehydration tower 14 is sent to the de-heavy tower 15 to remove heavy components. The crude PDO at the top of the tower enters the PDO refining tower 16 for distillation and separation, resulting in 1,3-propylene glycol (PDO) product at the bottom of the tower. The impurity gas at the top of the tower, along with the light component gas from the de-light tower and the tail gas from the acrolein absorption tower, is sent to the exhaust gas treatment system 17 for waste gas treatment. Part of the treated tail gas is discharged as purge gas, and part is returned to the propylene oxidation reactor 1 as recycle gas.

[0064] By controlling the flow rate of the circulating absorption water entering the acrolein absorption tower 5, the aqueous solution concentration of the crude acrolein solution is controlled within a range of 5 wt% to 35 wt%, preferably 8 wt% to 20 wt%, thereby reducing the possibility of acrolein self-polymerization, reducing energy consumption, and achieving a higher PDO yield.

[0065] The use of this process technology can achieve an acrolein yield of more than 98%, and the purity of the final PDO product is more than 99.7%.

[0066] [Example 1]

[0067] This example uses a 100,000-ton / year propylene-to-1,3-propylene glycol production process as the design and calculation. 12,200 kg / h of fresh propylene feedstock is mixed with 59,250 kg / h of fresh air, 4,100 kg / h of steam, and 24,000 kg / h of recycle gas. The mixed gas enters propylene oxidation reactor 1 at 149°C and 0.2 MPaG. After oxidation at 245°C and 0.16 MPaG, the resulting acrolein product gas is heat recovered and fed to quench absorption tower 2. At atmospheric pressure, fresh desalted water is added to the top of quench absorption tower 2 at a rate of 5,750 kg / h. Through gas-liquid countercurrent contact, heavy components in the acrolein product gas, such as acrylic acid and acetic acid, are rapidly absorbed. The absorption liquid obtained in the bottom of the tower enters the first acrolein recovery tower 3. In the first acrolein recovery tower 3, light non-condensable gases and acrolein from the bottom liquid of the quench absorption tower 2 are stripped by distillation and returned to the quench absorption tower 2, achieving an acrolein product yield of 98.7%. The acidic waste liquid obtained in the bottom liquid of the first acrolein recovery tower 3 is sent to a subsequent waste liquid treatment system. Acrolein product gas from the top of the quench absorption tower 2 is pressurized to 0.25 MPaG via the first compressor 4 at a rate of 89,750 kg / h before entering the acrolein absorption tower 5. After absorption, the crude acrolein-containing liquid in the bottom liquid is fed to the stripping tower 6. After passing through the stripping tower 6, the non-condensable gases and a small amount of acrolein in the top liquid are returned to the first compressor 4. The acrolein aqueous solution obtained in the bottom liquid liquid is fed to the acrolein hydration reactor 7 at a rate of 117,484 kg / h for acrolein hydration. The resulting mixture enters the second acrolein recovery tower 8 for distillation and separation. The unreacted acrolein is obtained from the top liquid and returned to the acrolein hydration reactor 7. The crude liquid from the bottom of the second acrolein recovery tower 8 is fed to the first hydrogenation reactor 9 and then the second hydrogenation reactor 10 at a rate of 160,088 kg / h, followed by a two-stage hydrogenation reaction with 2,450 kg / h of hydrogen. The resulting hydrogenation reaction material is then fed to a gas-liquid separator 11 for gas-liquid separation. Most of the unreacted hydrogen is pressurized to 5.1 MPaG by a second compressor 12 and then recycled to the inlet of the first hydrogenation reactor 9. The PDO reaction liquid from the bottom of the gas-liquid separator 11 is first fed to a lightness removal tower 13 at a rate of 160,451 kg / h to separate the majority of non-condensable gases, aldehydes, and alcohols that are lighter than water. The bottom liquid is then fed to a dehydration tower 14 for dehydration. After dehydration, the water collected at the top of the tower is cooled, mixed with fresh desalted water, and returned to the acrolein absorption tower 5, achieving water recycling. The bottom liquid from dehydration tower 14 is fed to de-heavy column 15 to remove heavy components. The crude PDO at the top of the tower enters PDO refining tower 16 for distillation and separation. At the bottom of the tower, 12,500 kg / h of PDO product with a purity of 99.7% is obtained. The impurity gas at the top of the tower, along with the light component gas from the top of light component removal tower 13 and the tail gas from acrolein absorption tower 5, is fed to exhaust gas treatment system 17 for waste gas treatment. Half of the treated tail gas is discharged as purge gas, and the remaining half is returned to the propylene oxidation system as recycle gas.

[0068] The liquid-to-gas ratio of the circulating absorption water in the acrolein absorption tower 5 to the bottom gas phase is recorded as the liquid-to-gas ratio; the acrolein yield is the ratio of the acrolein content in the acrolein aqueous solution after the second stripping treatment in the stripping tower 6 to the acrolein content in the acrolein product gas (gaseous acrolein) obtained after oxidation in the propylene oxidation reactor 1.

[0069] In this embodiment, the amount of water circulated and absorbed at the top of the acrolein absorption tower 5 is 93798 kg / h, and the liquid-to-gas ratio of the circulating absorption water to the gas phase at the bottom of the tower is 1.045. The concentration of the acrolein solution obtained after the pressurized water absorption in the acrolein absorption tower 5 is 10.2 wt %. At this concentration, acrolein is not easily self-polymerized.

[0070] After adopting this process technology, the acrolein yield can reach 98.7%, and the purity of the final PDO product is 99.7%.

[0071] [Example 2]

[0072] The difference from Example 1 is that the circulating absorption water flow rate entering the acrolein absorption tower 5 is regulated to 54942 kg / h, the liquid-gas ratio of the circulating absorption water to the bottom gas phase is 0.612, and the concentration of the acrolein solution obtained after pressurized water absorption in the acrolein absorption tower 5 is 18.0 wt%.

[0073] After adopting this process technology, the acrolein yield can reach 98.0%, and the purity of the final PDO product is 99.7%.

[0074] Compared with Example 1, this embodiment reduces the absorption water flow of circulating water, reduces the energy consumption of the device by more than 20%, and increases the possibility of acrolein self-polymerization during the hydration process.

[0075] [Example 3]

[0076] The difference from Example 1 is that the circulating absorption water flow rate entering the acrolein absorption tower 5 is regulated to 140009 kg / h, the liquid-gas ratio of the circulating absorption water to the bottom gas phase is 1.56, and the concentration of the obtained acrolein crude liquid is 5.0 wt% to ensure that acrolein does not self-polymerize as much as possible.

[0077] After adopting this process technology, the acrolein yield can reach 99.0%, and the purity of the final PDO product is 99.7%.

[0078] Compared with Example 1, the circulating absorption water flow rate is increased, and the energy consumption of the device is increased by more than 30%.

[0079] [Example 4]

[0080] The difference from Example 1 is that the first acrolein recovery tower 3 is not included, that is, there is no step of subjecting the heavy component exhaust gas to the first stripping treatment and recovering the atmospheric pressure water to absorb the removed acrolein; the absorption liquid containing heavy components such as acrylic acid and acetic acid obtained by quenching the bottom of the absorption tower 2 is directly used as the acid-containing waste liquid and enters the subsequent waste liquid treatment system.

[0081] After adopting this process technology, the acrolein yield can reach 96.4%, and the purity of the final PDO product is 99.7%.

[0082] The energy consumption of the device is the same as that of Example 1.

[0083] [Example 5]

[0084] The difference from Example 1 is that only atmospheric water absorption in the quench absorption tower 2 and pressurized water absorption in the acrolein absorption tower 5 are performed. The first stripping treatment in the first acrolein recovery tower 3 and the second stripping treatment in the stripping tower 6 are omitted. In other words, the crude acrolein liquid after pressurized absorption directly enters the acrolein hydration reactor 7 for hydration. Light component exhaust gas is not removed, and there is no step of recovering the acrolein removed by the atmospheric water absorption in the first stripping treatment.

[0085] After adopting this method, the acrolein yield is only 96.4%, and the acrolein aqueous solution will increase 2.6wt% of light component impurities, affecting the subsequent PDO reaction.

[0086] [Comparative Example 1]

[0087] The difference from Example 1 is that the acrolein solution is not subjected to the pressurized water absorption treatment in the acrolein absorption tower 5 , that is, the acrolein solution after the atmospheric pressure water absorption in the quench absorption tower 2 is directly sent to the stripping tower 6 for the second stripping treatment.

[0088] After adopting this method, the acrolein yield is only 80%, the acrolein loss in the light component gas is large, and the raw material propylene consumption of PDO products increases by more than 1.2 times.

[0089] Any numerical value mentioned in the present invention includes all values ​​that increase by one unit each time from the lowest value to the highest value if there is only a gap of two units between any minimum value and any maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is stated to be 50-90, it is meant in this specification to specifically list values ​​such as 51-89, 52-88... and 69-71 and 70-71. For non-integer values, it is appropriate to consider units of 0.1, 0.01, 0.001 or 0.0001. These are just some special examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed lowest value and the listed highest value are considered to have been disclosed.

[0090] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing 1,3-propylene glycol from propylene, characterized in that: include: Propylene is oxidized to produce gaseous acrolein, which is first subjected to rapid cooling and absorption to remove heavy component waste gas, and then absorbed with pressurized water to obtain an acrolein aqueous solution; the acrolein aqueous solution is subjected to a hydration reaction and then subjected to two hydrogenation treatments to produce 1,3-propylene glycol.

2. The method for preparing 1,3-propylene glycol from propylene according to claim 1, characterized in that The following steps are involved: S1, subjecting a mixed gas of propylene, air and water vapor to an oxidation reaction to obtain gaseous acrolein; S2, gaseous acrolein is rapidly cooled and absorbed to remove heavy component waste gas, and the remaining light component gas is absorbed by pressurized water to obtain acrolein crude liquid; S3, subjecting the crude acrolein solution to a second stripping treatment to obtain an acrolein aqueous solution; S4, the acrolein aqueous solution is subjected to a hydration reaction, and the hydration product is subjected to two hydrogenation reactions; S5. After the hydrogenation product is separated into gas and liquid, the liquid phase is sequentially subjected to light removal treatment, dehydration treatment and heavy removal treatment to obtain 1,3-propylene glycol.

3. The method for preparing 1,3-propylene glycol from propylene according to claim 1 or 2, characterized in that: The quench absorption in step S2 includes water absorption in gas-liquid countercurrent contact; preferably, the gaseous acrolein and desalted water flow in countercurrent, and the desalted water absorbs the heavy component waste gas in the gaseous acrolein at 5-60°C, preferably 8-40°C; and / or, The gas-liquid ratio of the quench absorption is 0.02-0.2:1, preferably 0.04-0.12:1; and / or, The heavy component waste gas is subjected to a first stripping treatment, and the acrolein removed by quenching absorption is recovered; preferably, the acrolein recovered by the first stripping treatment is returned to the quenching absorption step; preferably, the pressure of the first stripping treatment is -0.03 MPaG to 0.9 MPaG; and / or, The pressure of the pressurized water absorption is 0.01 MPaG to 2.0 MPaG, preferably 0.05 to 1.0 MPaG; and / or, The liquid-gas ratio of the absorbed water to the light component gas in the pressurized water absorption is 0.25 to 2.7:1, preferably 0.5 to 1.6:

1.

4. The method for preparing 1,3-propylene glycol from propylene according to any one of claims 1 to 3, characterized in that: The reaction temperature of the oxidation reaction in step S1 is 200-300° C., and the pressure is 0.01 MPaG-0.9 MPaG.

5. The method for preparing 1,3-propylene glycol from propylene according to any one of claims 1 to 4, characterized in that: Step S3: The second stripping treatment is used to remove light waste gas; preferably, the light waste gas is returned to repeat the pressurized water absorption step; and / or, The pressure of the second stripping treatment is 0.01 MPaG to 0.9 MPaG; and / or, After the second stripping treatment, the acrolein concentration in the obtained acrolein aqueous solution is 5 to 35 wt %, preferably 8 to 20 wt %.

6. The method for preparing 1,3-propylene glycol from propylene according to any one of claims 1 to 5, characterized in that: The reaction pressure of the hydration reaction treatment in step S4 is 0.0-2.0 MPaG, and the reaction temperature is 25-100° C.; and / or, The two hydrotreatments include a first hydrotreatment and a second hydrotreatment; and / or, The reaction pressure of the first hydrotreatment is 2-10 MPaG, and the reaction temperature is 25-150° C.; and / or, The reaction pressure of the second hydrotreatment is 2-10 MPaG, and the reaction temperature is 50-200° C.; and / or, Between the hydration treatment and the two hydrogenation treatments, a distillation separation step is performed to screen out unreacted acrolein and return it to the hydration reaction treatment step.

7. The method for preparing 1,3-propylene glycol from propylene according to any one of claims 1 to 6, characterized in that: The gas-liquid separation in step S5 is performed at a pressure of 2 to 10 MPaG and a temperature of 50 to 200° C.; and / or The unreacted hydrogen separated by the gas-liquid separation is returned to the first hydroprocessing step; and / or, The pressure of the light removal treatment is -0.10 to 0.5 MPaG; and / or, The pressure of the dehydration treatment is -0.10 to 0.5 MPaG; preferably, the circulating absorption water obtained from the dehydration reaction is returned to the pressurized water absorption step as absorption water; and / or, The pressure of the weight removal treatment is -0.10 to 0.5 MPaG; and / or, After the weight removal treatment, the product is further subjected to a refining treatment; and / or The waste gas not absorbed by the pressurized water absorption and / or the waste gas treated by light removal and / or the waste gas treated by purification is subjected to tail gas treatment; preferably, part of the circulating gas generated by the tail gas treatment participates in the oxidation reaction of step S1.

8. A process device for preparing 1,3-propylene glycol from propylene according to any one of claims 1 to 7, characterized in that: It includes a propylene oxidation reactor, a quench absorption tower, a first compressor, an acrolein absorption tower, an acrolein hydration reactor, a first hydrogenation reactor and a second hydrogenation reactor connected in sequence; The propylene oxidation reactor is used to oxidize propylene to produce gaseous acrolein; The quenching absorption tower is used for quenching and absorbing the heavy component waste gas; The first compressor is used to pressurize the acrolein gas entering the acrolein absorption tower; The acrolein absorption tower is used for pressurized water absorption to obtain an acrolein aqueous solution; The acrolein hydration reactor is used to perform a hydration reaction on the acrolein aqueous solution; The first hydrogenation reactor and the second hydrogenation reactor are used for two hydrogenation treatments in sequence.

9. The process device according to claim 8, characterized in that: It also includes a first acrolein recovery tower connected to the quenching absorption tower, wherein the first acrolein recovery tower is used to recover the acrolein removed by the quenching absorption; preferably, the gas phase outlet of the first acrolein recovery tower is connected to the quenching absorption tower, and the liquid phase outlet is used to discharge waste liquid; and / or, The system further comprises a stripping tower disposed between the acrolein absorption tower and the acrolein hydration reactor, wherein the stripping tower is used for performing a second stripping treatment. Preferably, the stripping tower inlet is connected to the acrolein absorption tower outlet, the gas phase outlet is connected to the acrolein absorption tower inlet pipeline, and the liquid phase outlet is connected to the acrolein hydration reactor; and / or, The system further comprises a second acrolein recovery tower disposed between the acrolein hydration reactor and the first hydrogenation reactor, wherein the second acrolein recovery tower is used for rectifying, separating and screening out unreacted acrolein and returning the unreacted acrolein to the acrolein hydration reactor; and / or, The system further comprises a gas-liquid separator connected to the outlet of the second hydrogenation reactor, the gas-liquid separator being used to separate unreacted hydrogen; preferably, a hydrogen transmission pipeline for returning unreacted hydrogen to the first hydrogenation reactor is provided between the top outlet of the gas-liquid separator and the first hydrogenation reactor; more preferably, a second compressor is provided on the hydrogen transmission pipeline; It also includes a light removal tower, a dehydration tower and a heavy removal tower which are sequentially arranged after the gas-liquid separator; the light removal tower is used for light removal processing; the dehydration tower is used for dehydration processing; the heavy removal tower is used for heavy removal processing; The invention also comprises a PDO refining tower connected to the deweighting tower, and the PDO refining tower is used for refining the product after the deweighting treatment.

10. The process device according to claim 8 or 9, characterized in that: The process further comprises a tail gas treatment system connected to the acrolein absorption tower, the lightness removal tower, and the PDO refining tower for receiving and treating tail gas; preferably, a circulating gas pipeline is connected between the tail gas treatment system and the propylene oxidation reactor for delivering the treated tail gas to the propylene oxidation reactor; and / or, A circulating absorption water delivery pipeline is connected between the dehydration tower and the acrolein absorption tower, and is used to deliver the water removed from the dehydration tower to the acrolein absorption tower for reuse.

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