PBT(polybutylene terephthalate) esterification reaction system

Abstract

The invention relates to a PBT (polybutylene terephthalate) esterification reaction system, which comprises a slurry finished product tank, a catalyst tank, an esterification reaction kettle, a pre-condensation reaction kettle and a final condensation reaction kettle, wherein a discharging opening of the slurry finished product tank is connected with a slurry inlet of an esterification kettle; a discharging opening of the esterification kettle is connected with a feeding opening of a pre-condensation kettle; a discharging opening of the pre-condensation kettle is connected with a feeding opening of the final condensation kettle; a catalyst inlet arranged at the bottom of the esterification reaction kettle is provided with a catalyst bottom injection valve; a barrel pump outlet built in a catalyst barrel is connected with a feeding opening of the catalyst tank through a barrel pump output pipe; an air inlet on the top of the catalyst tank is connected with a nitrogen pipe; a dischargingopening of the catalyst tank is connected with an inlet of a catalyst metering pump; an outlet of the catalyst metering pump is connected with a material inlet of a catalyst heater through a catalystfilter; a material outlet of the catalyst heater is connected with an inlet of the catalyst bottom injection valve through a catalyst bottom injection pipe. The catalyst of the system does not need to be mixed with BDO (1,4-butanediol) for preparation; hydrolysis or pipeline blockage is not liable to occur; the continuous production can be ensured.

Description

technical field [0001] The invention relates to a PBT production system, in particular to a PBT esterification reaction system, and belongs to the technical field of polyester production equipment. Background technique [0002] Polybutylene terephthalate, referred to as PBT, belongs to the series of polyesters. It is formed by reacting 1,4-butanediol (BDO) and terephthalic acid (PTA) in an esterification reactor to form terephthalic acid bis Hydroxybutyl ester (BHBT) and higher molecular oligomers and water and BDO are cyclized at high temperature to generate tetrahydrofuran (THF), and then enter the polycondensation reaction, which includes pre-condensation and final polycondensation. [0003] The catalyst for PBT polymerization production is tetrabutyl titanate, which is easily hydrolyzed when it encounters water, loses its activity, and at the same time generates titanium hydrate, which is easy to block the pipeline and affect the addition of the catalyst. Tetrabutyl tit...

AI Technical Summary

Problems solved by technology

The following problems exist in the pre-condensation reaction kettle: 1. The diameter of the upper and lower cylinders is the same, and the stirring takes up most of the space, which is not conducive to the release of small molecule products, so that the reaction can proceed in the positive direction

2. The gas phase space of the upper and lower chambers is independent, the gas phase port of the pre-shrinking kettle in the lower chamber is set in the upper chamber, and the stirring also passes through the upper chamber, occupying a lot of space in the upper chamber

3. The upper and lower chambers correspond to a set of scraper spraying systems respectively, with many supporting equipment, complex systems and large investment

[0008] The traditional vacuum system has the following defects: 1. Two independent vacuum systems occupy a large space, difficult to arrange equipment, numerous systems, frequent on-site operations, high operating intensity, and difficult operations for project operators

2. The water produced by the polycondensation reaction enters the vacuum system, and the spray system cannot capture it. The BDO steam jet pump requires a large amount of air, and a relatively large BDO steam jet pump is required, which occupies too much space and consumes high energy consumption.

3. The temperature of PBT polycondensation reaction is high. At this stage, BDO is prone to cyclization reaction to generate tetrahydrofuran. THF is a low boiling substance, which is difficult to capture and easy to accumulate in the liquid ring vacuum pump group. The power of the liquid ring pump group will increase. The more insufficient, the final vacuum degree of the whole system is not enough, the reaction pressure is too high, and the reaction products cannot meet the requirements

4. In order to ensure that the vacuum system meets the requirements, the liquid ring pump unit requires continuous replacement of the working fluid. The replaced working fluid cannot be reused for slurry preparation due to the high content of tetrahydrofuran and the characteristics of tetrahydrofuran. The working fluid basically becomes waste BDO, which not only wastes raw materials, but also increases the amount of waste liquid treatment, causing environmental pollution

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