阅读说明：本技术 一种环氧丙烷的精制工艺 (Refining process of propylene oxide ) 是由 夏苗 秦凤祥 黄晶晶 朱忆宁 王佳兵 胡猛 于 2020-06-12 设计创作，主要内容包括：本发明公开一种环氧丙烷的精制工艺,包括预分离、丙烯汽提、环氧丙烷精制、溶剂回收以及硫酸钠蒸发结晶。本发明针对目前过氧化氢直接氧化法生产的环氧丙烷分离工艺复杂、碱性废水得不到合理利用等问题,开发了新的精制工艺,尤其是将碱性废水通过加入硫酸得到硫酸钠副产品,合理利用了资源,提高了经济效益,也大大减少了碱性废液排放。(The invention discloses a refining process of propylene oxide, which comprises pre-separation, propylene stripping, propylene oxide refining, solvent recovery and sodium sulfate evaporation crystallization. The invention develops a new refining process aiming at the problems that the separation process of the propylene oxide produced by the direct oxidation method of the hydrogen peroxide is complex, the alkaline waste water can not be reasonably utilized and the like, and particularly, the sodium sulfate byproduct is obtained by adding the sulfuric acid into the alkaline waste water, so that the resources are reasonably utilized, the economic benefit is improved, and the discharge of the alkaline waste liquid is greatly reduced.)

1. A process for refining propylene oxide, comprising the steps of:

s1, mixing hydrogen peroxide, a solvent and propylene, and then carrying out epoxidation reaction, and recovering the obtained reaction liquid through propylene to obtain a liquid-phase product;

s2, feeding the liquid-phase product into a pre-separation tower, obtaining crude propylene oxide at the tower top, and feeding the tower bottom material flow into a solvent recovery system;

s3, feeding the crude propylene oxide into a propylene stripping tower, refluxing one part of the liquid phase at the top of the tower into the pre-separation tower, separating propylene from the other part of the liquid phase through a propylene separating tank, and compressing the propylene to enter a propylene circulating system; mixing the crude propylene oxide flowing out of the tower bottom with an alkaline solution in a crude propylene oxide buffer tank;

s4, feeding the crude epoxypropane mixed by the alkali liquor into an epoxypropane refining tower for extractive distillation, discharging oxygen-containing gas from a tower top material flow to obtain an epoxypropane product, re-purifying a tower bottom material flow by a re-separation tower, returning the tower top material flow from the re-separation tower to the epoxypropane refining tower, and feeding a crude solvent of the tower bottom material flow of the re-separation tower into a solvent recovery tower;

s5, the solvent separated by the solvent recovery tower enters a solvent circulation system from the tower top, the alkaline waste water of the tower bottom material flow of the solvent recovery tower is added with sulfuric acid for neutralization, and the neutralized sodium sulfate solution enters an evaporation kettle for evaporation and crystallization to obtain a byproduct sodium sulfate.

2. The process of claim 1, wherein in S1, the solvent is methanol.

3. The process as claimed in claim 1, wherein in S2, the top pressure of the pre-separation tower is 0.05-0.5MPa, the temperature of the bottom of the tower is 90-120 ℃, and the temperature of the top of the tower is 60-90 ℃.

4. The process of claim 1, wherein in S3, the top pressure of the propylene stripping tower is 0.05-0.5MPa, the temperature of the bottom of the tower is 60-150 ℃, and the temperature of the top of the tower is 60-120 ℃.

5. The process of claim 1, wherein in S4, the top pressure of the propylene oxide refining tower is 0.05-0.5MPa, the temperature of the tower bottom is 60-150 ℃, and the temperature of the top extraction of the tower is 30-90 ℃.

6. The process of claim 1, wherein in S4, the top pressure of the re-separation column is 0.05 to 0.5MPa, the bottom temperature of the column is 60 to 150 ℃, and the top temperature of the column is 30 to 90 ℃.

7. The process as claimed in claim 1, wherein in S4, the top pressure of the solvent recovery column is 0.05-0.5MPa, the temperature in the bottom of the column is 120-180 ℃, and the temperature at the top of the column is 90-150 ℃.

8. The process as claimed in claim 1, wherein in S5, the temperature of the evaporation kettle is 120-200 ℃.

9. The process of claim 1, wherein in S3, the alkaline solution is sodium hydroxide solution or sodium bicarbonate solution.

Technical Field

The invention relates to the technical field of preparation of propylene oxide, and particularly relates to a refining process of propylene oxide.

Background

Propylene oxide is a very important chemical raw material, and the production technology mainly comprises a chlorohydrin method, a co-oxidation method and a hydrogen peroxide direct oxidation method (HPPO), wherein the most promising HPPO process is mainly due to high atom utilization rate and environmental friendliness, and conforms to the concept of green chemistry.

The separation and purification of products in the HPPO process is one of the key technologies. GB/T14491-2015 industrial propylene oxide makes a clear requirement on the quality of propylene oxide: qualified epoxypropane product has purity of 99.80 omega%, water content less than or equal to 500ppm, and aldehyde impurities less than or equal to 200 ppm; the high-quality product of the propylene oxide has the purity of 99.95 omega percent, the water content is less than or equal to 200ppm, and the aldehyde impurities are less than or equal to 500 ppm; few high-end applications even require less than 10ppm of aldehyde impurities. The propylene oxide reaction liquid contains propylene oxide, propylene, a solvent, water, propylene glycol and other byproducts, and in industrial production, aldehyde and ketone impurities in the HPPO reaction liquid are often as high as 100-2000 ppm, separation and purification are difficult, and the product quality can be ensured only by effectively removing the impurities in the reaction liquid. Methyl formate can be effectively removed by reacting with alkaline substances to generate salts and methanol, and aldehyde ketone impurities can be removed by reacting hydrazine or hydrazine hydrate and other substances to generate insoluble substances.

Chinese patent CN200810053897.9 discloses a method for purifying propylene oxide, wherein an extractant is added above the feeding point of crude propylene oxide on a rectifying tower, and the extractant is an alkaline solution containing ammonia or ammonium salt. The patent does not mention alkaline wastewater treatment.

Chinese patent CN201110434173.0 discloses a method for refining and purifying propylene oxide, wherein crude propylene oxide enters a reactor filled with basic ion exchange resin for reaction, methyl formate and acetaldehyde in the crude propylene oxide are removed, and then the crude propylene oxide is further rectified to obtain high-purity propylene oxide. This method uses a reactor packed with a basic ion exchange resin, and is higher in cost and increased in reactor equipment investment compared with a basic solution.

Chinese patent CN201510468132.1 discloses a method for purifying propylene oxide, in which crude propylene oxide is mixed with alkaline solution, methyl formate as an impurity reacts to produce methanol and sodium formate, the reacted solution is mixed with hydrazine solution, and acetaldehyde, acetone, etc. are reduced to hydrazone heavy components and water. The patent does not mention the problem of wastewater treatment.

The above patents all utilize alkaline substances to purify propylene oxide, the alkaline ion exchange resin reactor has high cost, and the alkaline solution does not consider the problem of wastewater treatment and utilization.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a propylene oxide refining process aiming at the defects of the prior art, so as to achieve the purposes of optimizing the propylene oxide refining process, reasonably utilizing the resources of wastewater, reducing the wastewater discharge and ensuring that the process is more environment-friendly.

The technical scheme is as follows: the invention relates to a refining process of propylene oxide, which comprises the following steps:

s1, mixing hydrogen peroxide, a solvent and propylene, and then carrying out epoxidation reaction, and recovering the obtained reaction liquid through propylene to obtain a liquid-phase product;

s2, feeding the liquid-phase product into a pre-separation tower, obtaining crude propylene oxide at the tower top, and feeding the tower bottom material flow into a solvent recovery system;

s3, feeding the crude propylene oxide into a propylene stripping tower, refluxing one part of the liquid phase at the top of the tower into the pre-separation tower, separating propylene from the other part of the liquid phase through a propylene separating tank, and compressing the propylene to enter a propylene circulating system; mixing the crude propylene oxide flowing out of the tower bottom with an alkaline solution in a crude propylene oxide buffer tank;

s4, feeding the crude epoxypropane mixed by the alkali liquor into an epoxypropane refining tower for extraction rectification, wherein an extracting agent is water, hydrazine hydrate is added into the tower to react with aldehyde ketone impurities to generate insoluble substances, the insoluble substances are precipitated on a filler, an oxygen-containing gas is discharged from a tower top stream to obtain an epoxypropane product, a tower bottom stream is purified again by a re-separation tower and then returned to the epoxypropane refining tower from the tower top of the re-separation tower, and the crude solvent of the tower bottom stream of the re-separation tower is fed into a solvent recovery tower;

s5, the solvent separated by the solvent recovery tower enters a solvent circulation system from the tower top, the alkaline waste water of the tower bottom material flow of the solvent recovery tower is added with sulfuric acid for neutralization, and the neutralized sodium sulfate solution enters an evaporation kettle for evaporation and crystallization to obtain a byproduct sodium sulfate.

Preferably, in S1, the solvent is methanol.

Preferably, in S2, the top pressure of the pre-separation tower is 0.05-0.5MPa, the temperature of the tower bottom is 90-120 ℃, and the extraction temperature at the tower top is 60-90 ℃.

Preferably, in S3, the top pressure of the propylene stripping tower is 0.05-0.5MPa, the temperature of the tower bottom is 60-150 ℃, and the extraction temperature at the tower top is 60-120 ℃.

Preferably, in S4, the top pressure of the propylene oxide refining tower is 0.05-0.5MPa, the temperature of the tower bottom is 60-150 ℃, and the extraction temperature at the tower top is 30-90 ℃.

Preferably, in S4, the top pressure of the re-separation tower is 0.05-0.5MPa, the temperature of the tower bottom is 60-150 ℃, and the extraction temperature at the tower top is 30-90 ℃.

Preferably, in S4, the top pressure of the solvent recovery tower is 0.05-0.5MPa, the temperature of the tower bottom is 120-180 ℃, and the extraction temperature at the tower top is 90-150 ℃.

Preferably, in S5, the temperature of the evaporation kettle is 120-200 ℃.

Preferably, in S3, the alkaline solution is sodium hydroxide solution or sodium bicarbonate solution

Compared with the prior art, the invention has the beneficial effects that: the invention effectively removes ester impurities by using the alkaline solution to improve the product purity, simultaneously treats and utilizes the alkaline wastewater to obtain a sodium sulfate byproduct, reduces the discharge of the alkaline wastewater, and generates economic and social benefits.

Drawings

FIG. 1 is a process flow diagram of an embodiment of the present invention.

In the attached figure, 1-a pre-separation tower, 2-a propylene stripping tower, 3-a circulating propylene compressor, 4-a propylene oxide refining tower, 5-a re-separation tower, 6-a solvent recovery tower and 7-an evaporation kettle.

Detailed Description

Referring to fig. 1, the present invention provides a process for refining propylene oxide, the process comprising the steps of:

s1, mixing hydrogen peroxide, a solvent and propylene, and then carrying out epoxidation reaction, and recovering the obtained reaction liquid through propylene to obtain a liquid-phase product;

s2, feeding the liquid-phase product into a pre-separation tower, obtaining crude propylene oxide at the tower top, and feeding the tower bottom material flow into a solvent recovery system;

s3, feeding the crude propylene oxide into a propylene stripping tower, refluxing one part of the liquid phase at the top of the tower into the pre-separation tower, separating propylene from the other part of the liquid phase through a propylene separating tank, and compressing the propylene to enter a propylene circulating system; mixing the crude propylene oxide flowing out of the tower bottom with an alkaline solution in a crude propylene oxide buffer tank;

s4, feeding the crude epoxypropane mixed by the alkali liquor into an epoxypropane refining tower for extraction rectification, wherein an extracting agent is water, hydrazine hydrate is added into the tower to react with aldehyde ketone impurities to generate insoluble substances, the insoluble substances are precipitated on a filler, an oxygen-containing gas is discharged from a tower top stream to obtain an epoxypropane product, a tower bottom stream is purified again by a re-separation tower and then returned to the epoxypropane refining tower from the tower top of the re-separation tower, and the crude solvent of the tower bottom stream of the re-separation tower is fed into a solvent recovery tower;

s5, the solvent separated by the solvent recovery tower enters a solvent circulation system from the tower top, the alkaline waste water of the tower bottom material flow of the solvent recovery tower is added with sulfuric acid for neutralization, and the neutralized sodium sulfate solution enters an evaporation kettle for evaporation and crystallization to obtain a byproduct sodium sulfate.

The technical solution of the present invention is described in detail below with reference to specific examples and drawings, but the scope of the present invention is not limited to the examples.