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CN-122010734-A - Energy-saving rectification process of glyceryl triacetate

CN122010734ACN 122010734 ACN122010734 ACN 122010734ACN-122010734-A

Abstract

The application relates to the technical field of fine chemical engineering, and particularly discloses an energy-saving rectification process of glyceryl triacetate. The process comprises the steps of firstly carrying out nitrogen replacement and anaerobic airtight pretreatment of acetic acid gas phase secondary purging on a rectification whole system, then carrying out solid acid catalytic esterification on glycerol and glacial acetic acid to obtain crude ester liquid, carrying out two-stage precise filtration pretreatment, sequentially carrying out sectional decompression pre-stripping, pressure deacidification and concentration, and finishing refining and purification through decompression coupling rectification of component activity coefficients in an acetic acid regulation system, wherein neutralization water washing and drying steps are not arranged in the whole process, and meanwhile, a whole system material and heat energy closed loop circulation system is constructed. The process can be used for industrial continuous production of food-grade and tobacco-grade glyceryl triacetate, can effectively improve the purity and quality stability of the product, greatly reduce the comprehensive energy consumption in the rectification process, radically reduce the generation of high-salt organic wastewater, has good economical efficiency and environmental protection, and is suitable for the development requirements of low-carbonization clean production in the fine chemical industry.

Inventors

  • SHAO JIE
  • LI RONGQIANG
  • SUN DONGDONG

Assignees

  • 河南顺泓环保材料有限公司

Dates

Publication Date
20260512
Application Date
20260402

Claims (10)

  1. 1. The energy-saving rectification process of the glyceryl triacetate is characterized by comprising the following steps of: S1, performing anaerobic sealing treatment, namely performing nitrogen replacement on the whole rectification system before starting, performing gas phase secondary purging by high-temperature acetic acid, and isolating air by using an acetic acid liquid seal sealing point; s2, filtering pretreatment, namely performing two-stage precise filtration on crude ester liquid obtained by catalytic esterification of glycerol and glacial acetic acid through solid acid, removing a solid acid catalyst, and removing neutralization, washing and drying in a whole process to obtain clear crude ester liquid; S3, pre-stripping separation, namely sending the clarified crude ester liquid into a sectional type decompression pre-stripping tower, taking a high Wen Ningshui discharged from the tower bottom of the deacidification tower with pressure as a heat source to remove acetic acid and water, sending acetic acid-water gas phase extracted from the tower top into the deacidification tower with pressure, and sending crude glyceryl triacetate liquid extracted from the tower bottom into a decompression coupling rectifying tower; S4, deacidifying and coupling a heat source, namely rectifying and separating the acetic acid-water gas phase in a deacidification tower with pressure, obtaining a high-temperature acetic acid gas phase at the tower top, directly introducing the high-temperature acetic acid gas phase into a main reboiler of a decompression coupling rectifying tower to serve as a main heat source, condensing to obtain acetic acid condensate, and conveying high-temperature condensate at the tower bottom to a pre-stripping tower for heating; S5, coupling rectification regulation and control, namely mixing crude triacetin liquid with acetic acid condensate, delivering the mixture to a decompression coupling rectification tower, arranging a main reboiler and an auxiliary reboiler at the tower bottom, stabilizing the concentration of acetic acid in the tower within a preset range by adjusting the addition amount of the acetic acid condensate, extracting light components containing acetic acid and monoacetin from the tower top in the rectification process, extracting a triacetin finished product from the side line of a stripping section, and discharging heavy components from the tower bottom; S6, recycling the whole system, namely, returning all acetic acid condensate obtained by the pressure deacidification tower to the front-end esterification reaction unit except for reflux and adding the acetic acid condensate into the pressure-reducing coupling rectification tower, condensing light components at the top of the pressure-reducing coupling rectification tower and returning the condensed light components to the feed end of the pre-stripping tower, and transferring high-temperature condensate at the bottom of the pressure deacidification tower to the front-end esterification reaction unit to preheat raw materials after heat exchange of the pre-stripping tower.
  2. 2. The energy-saving rectification process of glyceryl triacetate according to claim 1, wherein in the step S1, the temperature of the high-temperature acetic acid gas phase is 145-158 ℃, the oxygen content in the whole system is controlled below 50ppm, and in the continuous operation process of the whole system, a small amount of acetic acid gas phase is continuously introduced into the tower bottom of the decompression coupling rectification tower as inert protective gas, and the oxygen partial pressure in the tower is controlled to be not higher than 10ppm.
  3. 3. The process according to claim 1, wherein in step S2, the two-stage fine filtration is performed with a filtration accuracy of 0.1 μm to 0.3 μm and a filtration operation pressure of 0.2MPa to 0.6MPa.
  4. 4. The energy-saving rectification process of glyceryl triacetate as claimed in claim 1, wherein in the step S3, the operation absolute pressure of the pre-stripping tower is controlled to be 10kPa to 30kPa, and the temperature of a tower bottom is controlled to be 105 ℃ to 130 ℃.
  5. 5. The energy-saving rectification process of glyceryl triacetate according to claim 1, wherein in the step S4, the operation absolute pressure of the deacidification tower with pressure is controlled to be 250kPa to 350kPa, the temperature of a tower bottom is controlled to be 165 ℃ to 180 ℃, and the gas-phase mass concentration of high-temperature acetic acid extracted from the tower top is not less than 98%.
  6. 6. The energy-saving rectification process of the glyceryl triacetate as claimed in claim 1, wherein in the step S5, the operation absolute pressure of the decompression coupling rectification column is controlled to be 1-5 kPa, the temperature of a column bottom is controlled to be 130-150 ℃, the adding amount of acetic acid condensate is 1-6% of the feeding mass of the crude glyceryl triacetate liquid, and the acetic acid mass concentration in the column is stabilized to be 1-4%.
  7. 7. The energy-saving rectification process of the glyceryl triacetate, as set forth in claim 1, wherein in the step S3, the sectional type decompression pre-stripping tower adopts an upper and lower integrated structure, the lower section is a stripping section, the upper section is a rectifying section, clarified crude ester liquid enters from the top of the lower section, gas phase at the top of the stripping section enters the upper section rectifying section, 1% to 3% of the total mass of the light component condensed at the top of the decompression coupling rectifying tower is split to be used as reflux liquid of the upper section rectifying section, and liquid phase at the bottom of the upper section rectifying section is refluxed to the lower section stripping section.
  8. 8. The energy-saving rectification process of glyceryl triacetate as claimed in claim 1, wherein in the step S4, the reflux amount of the acetic acid condensate obtained after the high-temperature acetic acid gas phase extracted from the top of the deacidification tower with pressure is controlled to be 1.0 to 2.0 times of the mass of the feeding gas phase, and the temperature of the top of the tower is controlled to be 145 to 158 ℃.
  9. 9. The process for energy-saving rectification of glyceryl triacetate as claimed in claim 1, wherein the decompression coupling rectification column is provided with 32 to 38 theoretical plates, the feeding position is 18 to 22 theoretical plates, the side-draw outlet is positioned at 6 to 8 theoretical plates of the stripping section, and the reflux ratio of the top of the column is 2 to 4.
  10. 10. The energy-saving rectification process of triacetin according to claim 1, wherein interlocking control is adopted between the pressure deacidification tower and the pressure reduction coupling rectification tower, the operating pressure and the heating load of the pressure deacidification tower are adjusted according to the temperature difference between the top of the pressure deacidification tower and the bottom of the pressure reduction coupling rectification tower, the heat transfer temperature difference is maintained at 12-18 ℃, meanwhile, the feeding amount of acetic acid condensate, the reflux ratio of the top of the tower and the reflux ratio of the acetic acid condensate are synchronously adjusted according to the concentration of acetic acid in the pressure reduction coupling rectification tower and the acidity of a side-draw finished product, the feeding amount of the acetic acid condensate is increased when the concentration of acetic acid in the tower is lower than 1%, the reflux ratio is reduced when the concentration of acetic acid in the tower is higher than 4%, the feeding amount of the acetic acid condensate is increased when the acidity of the finished product exceeds 0.008%.

Description

Energy-saving rectification process of glyceryl triacetate Technical Field The application relates to the technical field of fine chemical engineering, in particular to an energy-saving rectification process of glyceryl triacetate. Background The glyceryl triacetate is a nontoxic environment-friendly polyol ester compound with excellent performance, has wide application in the fields of tobacco processing, food additives, medical intermediates, environment-friendly coating additives and the like by virtue of good plasticity, chemical stability and biocompatibility, and is an important product with a certain capacity scale in the domestic fine chemical industry. The main preparation route of the industrial glyceryl triacetate is the catalytic esterification reaction of glycerol and glacial acetic acid, the crude product obtained by the reaction is required to be refined and purified through a rectification link, the operation efficiency of the rectification link obviously influences the production cost of the product and the low carbonization level of the production process, and along with the continuous promotion of a domestic double-carbon target, the energy-saving optimization of the glyceryl triacetate rectification process has become a technical direction of great attention in the industry. The common glyceryl triacetate decompression rectification process in the industry is limited by the strong heat sensitivity of the glyceryl triacetate, the boiling point of the system is reduced by adopting high-vacuum decompression operation to reduce the thermal decomposition side reaction at high temperature, and the condensation latent heat of the gas phase at the top of the tower belongs to low-grade heat energy under the high-vacuum working condition, so that the high-efficiency recovery and utilization are difficult to realize by the conventional energy-saving means, and the heat energy is discharged after being condensed by circulating cooling water in most cases, so that the invalid loss of the heat energy is caused. Meanwhile, the monoacetin/diacetin and triacetin in crude products are near-boiling substances, the relative volatility of the monoacetin/diacetin and triacetin is further reduced in a high-vacuum environment, a higher reflux ratio is needed to meet the separation precision requirement, the heat load of a rectification system is further increased, and conventional multi-effect rectification, heat pump rectification and other energy-saving means are limited by the suitability of working conditions, so that the industrial commonality problem that the comprehensive energy consumption of a rectification link is high is difficult to radically relieve. Disclosure of Invention The application provides an energy-saving distillation process of glyceryl triacetate, which aims to solve the problems that the comprehensive energy consumption is high, the low-grade heat energy is difficult to be efficiently utilized and the reflux ratio required by separation is large in the glyceryl triacetate decompression distillation process in the prior art. An energy-saving rectification process of glyceryl triacetate comprises the following steps: S1, performing anaerobic sealing treatment, namely performing nitrogen replacement on the whole rectification system before starting, performing gas phase secondary purging by high-temperature acetic acid, and isolating air by using an acetic acid liquid seal sealing point; s2, filtering pretreatment, namely performing two-stage precise filtration on crude ester liquid obtained by catalytic esterification of glycerol and glacial acetic acid through solid acid, removing a solid acid catalyst, and removing neutralization, washing and drying in a whole process to obtain clear crude ester liquid; S3, pre-stripping separation, namely sending the clarified crude ester liquid into a sectional type decompression pre-stripping tower, taking a high Wen Ningshui discharged from the tower bottom of the deacidification tower with pressure as a heat source to remove acetic acid and water, sending acetic acid-water gas phase extracted from the tower top into the deacidification tower with pressure, and sending crude glyceryl triacetate liquid extracted from the tower bottom into a decompression coupling rectifying tower; S4, deacidifying and coupling a heat source, namely rectifying and separating the acetic acid-water gas phase in a deacidification tower with pressure, obtaining a high-temperature acetic acid gas phase at the tower top, directly introducing the high-temperature acetic acid gas phase into a main reboiler of a decompression coupling rectifying tower to serve as a main heat source, condensing to obtain acetic acid condensate, and conveying high-temperature condensate at the tower bottom to a pre-stripping tower for heating; S5, coupling rectification regulation and control, namely mixing crude triacetin liquid with acetic acid condensate, delivering the mixture to a decompre