CN101481298A - Production process for refining dichlorohydrin by glycerol reaction distillation - Google Patents

Abstract

The invention provides a production process for preparing dichloropropanol by reactive distillation of glycerol. After heat exchange, the raw material glycerol containing homogeneous catalyst enters from the top of the reactive distillation tower, and the hydrogen chloride gas enters from the lower part of the rectifying section of the tube-and-tube reactive distillation tower. Under 0.001～0.1MPa (absolute pressure), absorb chlorination reaction and rectify; the monochloropropanediol, glycerin and glycerin oligomers at the bottom of the tubular reactive distillation tower are sent to the heavy component separation tower to recover monochloropropanediol and glycerin under reduced pressure Send back to the raw material glycerin; the product gas at the top of the tubular reactive distillation tower is cooled by a heat exchanger to obtain dichloropropanol and sent to the cyclization process, and the tail gas is further washed with alkali water and then discharged with a vacuum pump.

Description

A kind of production technology of dichloropropanol prepared by reactive distillation of glycerin

1. Technical field

The invention provides a production process for preparing dichloropropanol by reactive distillation of glycerin, which belongs to the field of fine chemical industry.

2. Background technology

At present, there are two main production processes for epichlorohydrin and its precursor dichloropropanol: propylene high temperature chlorination method, allyl alcohol method and glycerin chlorination method. Propylene high-temperature chlorination method is the main production method of epichlorohydrin and its precursor dichloropropanol in the world so far. The production process is flexible, the process is mature, and the operation is stable. However, there are low conversion rates, many by-products, high energy consumption, Defects such as serious corrosion of equipment, large amounts of waste water and slag, and increasingly high prices of propylene raw materials. The allyl alcohol method has mild reaction conditions, high yield, less by-products, and less sewage, but has many reaction steps, short catalyst life, stainless steel must be used to prevent acetic acid corrosion, and the investment is relatively high. The glycerin chlorination method produces dichloropropanol and epichlorohydrin through one-step reaction of hydrogen chloride, without the use of chlorine gas, with mild reaction conditions, high yield, less by-products, and less sewage. Wider and lower cost, has received widespread attention.

The process of glycerin chlorination to produce dichloropropanol and epichlorohydrin developed by Jiangsu University of Technology is a batch method, which is prepared by using hydrogen chloride gas in a tank reactor. The investment is only a quarter of that of the propylene method, the cost is low, and the operating conditions are mild. , Safe and reliable, the waste water is only one-tenth of that of the propylene method, but the conversion rate is relatively low, the consumption of raw materials is large, the by-products are high, and the scale is difficult to expand. The published patents CN1882522A and CN1845888A are both produced by continuous method, and are all single or multi-stage series fully mixed bed reactors. The final reaction product is separated under normal pressure or reduced pressure, and the conversion rate, selectivity and yield are high, but the consumption of raw materials is relatively low. Large, high by-products, difficult to scale up.

3. Contents of the invention

The purpose of the present invention is exactly to provide a kind of production technology of dichloropropanol by reactive distillation of glycerol in order to overcome the deficiency that prior art exists. The technical process is simple and reasonable, the reaction conditions are warm, the system temperature is easy to control, the reaction conversion rate, yield and selectivity are high, and it is easy for large-scale industrial production.

Technical scheme of the present invention:

The invention provides a production process for preparing dichloropropanol by reactive distillation of glycerin. After heat exchange, the raw material glycerin containing homogeneous catalyst enters from the top of the reactive distillation tower, and the hydrogen chloride gas enters from the lower part of the packing section of the tube-and-tube reactive distillation tower through the gas distributor, and the raw material glycerin and hydrogen chloride gas pass through the packing layer in countercurrent at 90 ~ 120°C, 0.001-0.1MPa (absolute pressure) under the absorption chlorination reaction rectification; the reaction heat is removed through the cooling water between the tubes to maintain the reaction temperature; the monochloropropanediol, glycerin and Glycerol oligomers are sent to the heavy component separation tower to recover monochloropropanediol and glycerin under reduced pressure and sent back to the raw glycerin; the product gas at the top of the tubular reactive distillation tower is cooled by a heat exchanger to obtain dichloropropanol and sent to the cyclization process. The tail gas is further washed with alkaline water and then discharged with a vacuum pump.

The tubular reactive distillation column can be a single stage, or a two-stage or multi-stage series reactive distillation column in which the bottom material of the upper stage tower is used as the top feed of the lower stage tower.

The structure of the tube-and-tube reactive distillation tower is that the rectifying section of the tower is a tube-and-tube heat exchanger structure, the tubes are filled with fillers, and the cooling water is used between the tubes.

The tube-and-tube reactive distillation tower, heat exchanger, vapor-liquid separation tank and heavy component separation tower are all made of acid-resistant alloy steel, lined with enamel, polyvinyl chloride, polypropylene, polytetrafluoroethylene or resin-coated carbon steel.

The homogeneous catalyst is one or more of carboxylic acid, carboxylic acid anhydride, carboxylic acid amide, carboxylate or carboxylate with a normal pressure boiling point of 180 DEG C, and the dosage is 2-10% of glycerol.

Hydrogen chloride gas is produced by extraction and rectification of hydrochloric acid solution, and the extractant is one or more of sulfuric acid, sodium chloride, calcium chloride, calcium sulfate, sodium sulfate, etc. with a molar concentration of 25-32.3%.

4. Description of drawings

Accompanying drawing is process flow chart of the present invention. Fig. 1 is the technological process of single stage reaction, Fig. 2 is the technological process of tertiary reaction

Among them: 1-tube reactive distillation column, 2-packing, 3-liquid distributor, 4-tube, 5-heat exchanger, 6-vapor-liquid separation tank, 7-heavy component separation tower, 8-alkali Wash tank, 9-vacuum pump 10-gas distributor

5. Specific implementation

Below in conjunction with accompanying drawing, the present invention is described in detail:

Embodiment 1: After the heat exchange, the raw material glycerin containing the homogeneous catalyst enters from the top of the tubular reactive distillation tower 1, and the hydrogen chloride gas enters from the lower part of the filler 2 section of the tubular reactive distillation tower 1 through the gas distributor 10, The raw material glycerin and hydrogen chloride gas coming down from the liquid distributor 3 countercurrently pass through the packing layer 2 at 90-120°C and 0.001-0.1MPa (absolute pressure) to undergo absorption chlorination reaction rectification; the reaction heat passes through the cooling water between the tubes 4 Remove and keep the reaction temperature; the monochloropropanediol, glycerol and glycerol oligomers at the bottom of the tubular reactive distillation tower 1 are sent to the heavy component separation tower 7 to recover monochloropropanediol and glycerin under reduced pressure and send them back to the raw material glycerin; The product gas at the top of the reactive distillation tower 1 passes through the heat exchanger 5 to recover heat for cooling, and obtains dichloropropanol in the vapor-liquid separation tank 6 and sends it to the cyclization process.

Embodiment 2: After heat exchange, the raw material glycerin containing homogeneous catalyst enters from the top of the first-stage tubular reactive distillation tower 1, and the hydrogen chloride gas passes through the gas distributor 10 from the lower part of the filler 2 section of the tubular reactive distillation tower 1 Enter, the raw material glycerin and hydrogen chloride gas coming down from the liquid distributor 3 countercurrently pass through the 2 layers of packing at 90-120°C and 0.001-0.1MPa (absolute pressure) to undergo absorption chlorination reaction rectification; The cooling water is removed to keep the reaction temperature; the liquid at the bottom of the first-stage tubular reactive distillation tower 1 is sent to the top of the second-stage tubular reactive distillation tower 1 as a feed; the liquid at the bottom of the second-stage tubular reactive distillation tower 1 is The liquid is sent to the top of the three-stage tubular reactive distillation tower 1 as a feed; the monochloropropanediol, glycerin and glycerol oligomers at the bottom of the three-stage tubular reactive rectification tower 1 are sent to the heavy component separation tower 7 to recover monochlorine under reduced pressure Propylene glycol and glycerin are sent back to the raw material glycerin; the product gas at the top of the tubular reactive distillation tower 1 is cooled by the heat exchanger 5, and dichloropropanol is obtained in the vapor-liquid separation tank 6 and sent to the cyclization process, and the tail gas After being further washed with alkaline water in the alkali washing tank 8, it is discharged with a vacuum pump 9.

80% of glycerin is applied to this production process, the conversion rate per pass is about 99%, the selectivity of dichloropropanol is about 95%, the consumption of caustic soda is greatly reduced, the amount of waste water and the cost of dichloropropanol are reduced.

Claims (6)

1. The present invention provides a kind of production technology of dichloropropanol by reactive distillation of glycerin, and its technical feature is that the raw material glycerin that contains homogeneous catalyst enters from the top of reactive distillation tower after heat exchange, and hydrogen chloride gas is fed from the tube-and-tube reaction refinery. The lower part of the packing section of the distillation tower enters, and the raw material glycerin and hydrogen chloride gas pass through the packing layer in countercurrent at 90-120°C and 0.001-0.1MPa (absolute pressure) to undergo absorption chlorination reaction rectification; the reaction heat is removed through the cooling water between the tubes , keep the reaction temperature; the monochloropropanediol, glycerol and glycerol oligomers at the bottom of the tubular reactive distillation tower are sent to the heavy component separation tower to recover monochloropropanediol and glycerin under reduced pressure and send them back to the raw material glycerin; the tubular reactive distillation The product gas at the top of the tower is cooled by a heat exchanger to obtain dichloropropanol and sent to the cyclization process, and the tail gas is further washed with alkali water and then discharged with a vacuum pump. 2. according to the production technology of a kind of glycerol reactive distillation system dichloropropanol provided by claim 1, it is characterized in that the structure of shell and tube reactive distillation tower is that the rectifying section of tower is shell and tube heat exchanger structure, Packing is installed in the tubes, and cooling water is used between the tubes. 3. according to the production technology of a kind of glycerol reactive distillation dichloropropanol that provides according to claim 1, it is characterized in that the materials of tube-and-tube reactive distillation tower, static mixer and hydrolysis tower are acid-resistant alloy steel or internal Enamel lined, PVC, polypropylene or PTFE material or resin coated carbon steel. 4. according to the production technology of a kind of glycerin reactive distillation dichloropropanol that provides according to claim 1, it is characterized in that shell and tube reactive distillation column can be single-stage, also can be the material at the bottom of the upper tower as the lower tower top Feed two or multi-stage reactive distillation columns in series. 5. A kind of production technology of glycerin reactive distillation dichloropropanol provided according to claim 1 is characterized in that the homogeneous catalyst is carboxylic acid, carboxylic anhydride, carboxylic acid amide, carboxylate having a boiling point of 180° C. Or one or more of carboxylic acid esters, the dosage is 2-10% of glycerol. 6. According to the production process of a kind of glycerol reactive distillation dichloropropanol provided by claim 1, it is characterized in that hydrogen chloride gas is produced by extractive distillation of hydrochloric acid solution, and the extractant is 25-32.3% molar concentration One or more of sulfuric acid, sodium chloride, calcium chloride, calcium sulfate, sodium sulfate, etc.

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