CN102816139A - Purification process of tetrahydrofuran - Google Patents

Abstract

The invention discloses a tetrahydrofuran purification process, which is purified through three rectification towers, the front tower is a plate tower, the middle tower and the rear tower are packed towers. The invention has simple process, convenient operation, high purification efficiency and good working effect.

Description

Purification process of tetrahydrofuran

technical field

The invention relates to a purification process of tetrahydrofuran.

Background technique

The 60,000 tons/year PBT plant adopts German ZIMMER technology to obtain PBT products through three-pot reaction, which are esterification reaction, pre-condensation reaction and polycondensation reaction. Side reactions occur during the esterification process to produce tetrahydrofuran and water, and the crude tetrahydrofuran is purified through a recovery device. In addition to producing polytetrahydrofuran, tetrahydrofuran is also an important raw material for organic synthesis and a solvent with excellent performance. Polytetrahydrofuran (PolyTHF), also known as polytetramethylene ether glycol (PTMEG), is prepared from tetrahydrofuran (THF) through cationic ring-opening polymerization. PolyTHF (PTMEG) is an important raw material for the preparation of block polyurethane and polyether elastomer materials. Compared with other elastic materials, elastic materials made of PolyTHF have excellent hydrolytic stability, air permeability and wear resistance, and can also exhibit good elasticity, flexibility and impact resistance at low temperatures. It has unique and broad application prospects in textiles, pipes, chemicals, and medical equipment.

However, how to purify THF conveniently and efficiently has always been a subject of research in this field.

Contents of the invention

The purpose of the present invention is to provide a simple, convenient and efficient THF purification process.

Technical solution of the present invention is:

A purification process for tetrahydrofuran is characterized in that it comprises the following steps:

The crude tetrahydrofuran aqueous solution to be purified is stored in the crude tetrahydrofuran storage tank, and the tetrahydrofuran aqueous solution is pumped to the front tower feed preheater and the front tower tank liquid through the THF feed pump, and then enters the upper part of the tetrahydrofuran front tower; the tetrahydrofuran front tower is a plate type tower;

One stream of material in the front tower tank enters the front tower reboiler through the front tower bottom circulation pump, is heated by the middle tower top gas, and then flows back to the front tower tank after being heated by the heat exchanger, and the other stream is discharged through the front tower bottom The pump passes through the feed preheater of the front tower, and after being cooled by the feed stream, enters the waste water cooler at the bottom of the front tower, and is further cooled by circulating cooling water before being sent out of the boundary area for treatment;

The gas in the middle of the front tower flows into the side discharge tank after being condensed by the side discharge cooler of the front tower;

The gas at the top of the front tower is condensed and cooled by the circulating cooling water through the condenser at the top of the front tower, and then flows into the reflux tank of the front tower. The temperature of the top of the tower is controlled by the reflux flow of the front tower. The other stream is sent to the middle tower feed preheater through the middle tower feed pump connected to the front tower reflux tank, and then enters the middle tower after being heated by the liquid from the middle of the rectification section of the middle tower; the middle tower is a packed tower, and the middle tower The kettle liquid is heated by steam through the middle tower reboiler;

After the top liquid of the middle tower is cooled by the reboiler of the front tower, one stream is used as reflux, and the other stream is used as a side-drawing liquid to enter the discharge cooler at the top of the middle tower, and after being cooled by circulating cooling water, it flows into the side discharge tank;

The liquid from the middle part of the rectification section of the middle tower passes through the feed preheater of the middle tower and is cooled by the feed stream of the middle tower, and then enters the upper part of the front tower; The rear column reboiler is heated with steam;

The liquid in the rear tower bottom discharge cooler is cooled by circulating cooling water and then flows into the side line discharge tank;

After the top liquid of the rear tower passes through the condenser at the top of the rear tower and is condensed by the circulating cooling water, one stream flows to the top of the rear tower by itself as reflux, and the other stream passes through the cooler at the top of the rear tower and is further cooled by the circulating cooling water before flowing into the recovery inspection tank. Through the recovery pump, the analyzed tetrahydrofuran is sent out of the boundary area to the tank area, and the unqualified tetrahydrofuran is sent back to the crude tetrahydrofuran storage tank for rectification treatment;

The impurities of isopropanol, n-butanol and tributenol are removed by side mining, and the purity of THF is improved; the liquid in the side discharge tank is sent out of the boundary area to the heat medium station through the side discharge pump.

The unqualified liquid in the front tower, the middle tower and the back tower is put into the unqualified tetrahydrofuran tank, and the unqualified tetrahydrofuran pump is sent back to the crude tetrahydrofuran storage tank for rectification treatment.

The invention has simple process, convenient operation, high purification efficiency and good working effect.

Description of drawings

The present invention will be further described below in conjunction with drawings and embodiments.

Figure 1 is a flowchart of an embodiment of the present invention.

Detailed ways

The crude tetrahydrofuran aqueous solution to be purified (crude tetrahydrofuran is obtained from the side reaction of the PBT production device) is stored in the crude THF storage tank 101, and the crude THF contains 72.00% water, 27.23% THF, 0.01% n-butanol, 0.61% Tributenol and trace isopropanol etc.

The tetrahydrofuran aqueous solution is sent to the front tower feed preheater 103 by the THF feed pump 102 at a rate of 1650 kg/h, and then enters the upper part of the THF front tower 108 after exchanging heat with the bottom liquid of the front tower.

The THF front tower 108 is a tray tower with 35 theoretical stages. The operating temperature of the tower kettle is 102°C, and the operating pressure is 1 atmosphere.

One stream of material in the front tower tank passes through the front tower bottom circulation pump 107 at 23700kg/h and enters the front tower reboiler 114, is heated by the middle tower top gas, and then returns to the front tower tank after being heated by the heat exchanger 111; 1110kg/h passes through the front tower bottom discharge pump 106, passes through the front tower feed preheater 103, is cooled by the feed stream, enters the front tower bottom waste water cooler 104, is further cooled by circulating cooling water, and then sent out to the boundary area for sewage treatment field for biochemical treatment.

The gas in the middle of the front tower passes through the side discharge cooler 105 of the front tower at 100 kg/h, and then flows into the side discharge tank 118 after being condensed.

The gas at the top of the front tower flows into the reflux tank 110 of the front tower after being condensed and cooled by the circulating cooling water through the top of the front tower condenser 109 . The front tower controls the temperature at the top of the tower through the reflux flow. The top liquid containing 94.42% THF, 4.57% water and other impurities flows to the top of the front tower by itself as reflux, and the other passes through the intermediate tank 110 connected to the front tower reflux tank. The tower feed pump 112 sends the feed to the middle tower feed preheater 113 to be heated by the liquid from the middle part of the rectification section of the middle tower, and then enters the THF middle tower 115 .

The THF middle tower 115 is a packed tower, and the liquid in the middle tower is heated by 1.0Mpa (G) steam through the middle tower reboiler 116, the temperature of the tower bottom is 140°C, and the operating pressure is 0.62Mpa.

After the top liquid of the middle tower is cooled by the reboiler 114 of the front tower, one stream is used as 2420kg/h as reflux, and the other stream is used as side extraction liquid at 4kg/h to enter the middle tower top discharge cooler 117 and be cooled by circulating cooling water After that, it flows into the side discharge tank.

The liquid from the middle part of the rectifying section of the middle tower enters the upper part of the front tower at a rate of 2450 kg/h after being cooled by the feed stream of the middle tower through the middle tower feed preheater 113 . The middle tower bottom liquid is sent to the THF rear tower 122 at 435kg/h.

The THF rear tower 122 is a packed tower, and the tower bottom liquid passes through the rear tower reboiler 121 and is heated with 1.0 Mpa (G) steam. The temperature of the tower bottom is 70° C., and the operating pressure is 1 atmosphere.

The liquid in the rear tower bottom discharge cooler 119 is cooled by circulating cooling water at 15 kg/h, and then flows into the side discharge tank 118 .

After the top liquid of the rear tower passes through the rear tower top condenser 123 and is condensed by circulating cooling water, one stream of 6300 kg/h flows to the top of the rear tower by itself as reflux, and the other 420 kg/h passes through the rear tower top cooler 124 and is circulated cooling water After further cooling, it flows into the recovered THF test tank 125, and the analyzed THF is sent out of the boundary area to the tank area through the recovered THF pump 127, and the unqualified THF is sent back to the crude THF storage tank 101 for rectification treatment.

The impurities such as isopropanol, n-butanol and tributenol are removed by side mining to improve the purity of THF. The side sampling liquid is 29.49% water, 28.52% THF, 0.40% isopropanol, 11.32% n-butanol, and 30.56% tributenol. The liquid in the side line discharge tank 118 is sent out of the boundary area to the heat medium station through the side line discharge pump 120, and is burned in the heat medium furnace to generate carbon dioxide and water to reduce environmental pollution.

The unqualified liquid in the THF front tower, middle tower and rear tower tank is put into the unqualified THF tank 126, and is sent back to the crude THF storage tank 101 by the unqualified THF pump 128 for rectification again.

The purity of tetrahydrofuran recovered in this example was 99.9852%, and the recovery rate was 93.46%.

Claims (2)

1. the purifying technique of a THF is characterized in that: comprise the following steps:

Thick tetrahydrofuran aqueous solution to be purified is stored in the thick THF basin (101); Before delivering to through THF fresh feed pump (102), tetrahydrofuran aqueous solution after tower feed preheater (103) and the preceding tower bottoms heat exchange, gets into preceding tower (108) top of THF; Tower (108) is a tray column before the THF;

One gets into preceding tower reboiler (114) through recycle pump (107) at the bottom of the preceding tower preceding Tata still material; Be back to preceding tower still after passing through interchanger (111) heating after the overhead gas heating again in the quilt; Another strand is through discharging pump (106) process preceding tower feed preheater (103) at the bottom of the preceding Tata; After the feed stream cooling, gaseous effluent cooler (104) at the bottom of the tower is seen the battery limit (BL) off and is handled before getting into after recirculated cooling water further cools off;

Before the tower central gas through preceding tower side line discharging water cooler (105) condensation after, the inflow side line discharge tank (118);

Preceding overhead gas is after preceding overhead condenser (109) is recycled the condensed cooling; Flow in the preceding tower return tank (110); Preceding tower is through quantity of reflux control tower top temperature; Before column overhead liquid one as the tower feed preheater (113) that refluxes in flow to preceding cat head, another strand sent into through the middle tower fresh feed pump (112) that is connected with preceding tower return tank (110) by from tower (115) in the entering after the liquid heat at middle tower rectifying section middle part; Middle tower (115) is a packing tower, and middle tower tower bottoms is used steam heating through middle tower reboiler (116);

In column overhead liquid after preceding tower reboiler (114) cooling, one is as backflow, after cat head discharging water cooler (117) was recycled water quench during another strand adopted that liquid is logical and got into as side, flows into side line discharge tank (118);

Liquid from middle tower rectifying section middle part gets into Qian Ta top through tower feed stream cooling back in middle tower feed preheater (113) quilt; Middle tower tower bottoms is sent into back tower (122), and back tower (122) is a packing tower, and tower bottoms is used steam heating through back tower reboiler (121);

Back Tata still liquid through after flow into side line discharge tank (118) after discharging water cooler (119) is recycled water quench at the bottom of the tower;

After back column overhead liquid is recycled condensed through back overhead condenser (123); One is as refluxing from flowing to the back column overhead; Another strand is recycled water coolant through back cat head water cooler (124) and further cools off back inflow recovery prover tank (125); To analyze qualified THF through recovery pump (127) and see the battery limit (BL) off to the tank field, underproof THF is sent thick THF basin (101) rectification process again back to;

Adopt removal Virahol, propyl carbinol and three butenol impurity through side, improve THF purity; The interior liquid of side line discharge tank (118) is seen the battery limit (BL) off to the heating agent station through side line discharging pump (120).

2. the purifying technique of THF according to claim 1; It is characterized in that: Qian Ta, Zhong Ta and the underproof liquid of back Tata still are all put into defective THF jar (126), send thick THF basin (101) rectification process again back to by defective THF pump (128).

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