阅读说明：本技术 一种丙烯氧化制取丙烯酸的工艺方法 (Process for preparing acrylic acid by propylene oxidation ) 是由 李响 王宝杰 祝涛 张凤涛 安英爱 于 2019-09-05 设计创作，主要内容包括：本发明涉及一种丙烯氧化制取丙烯酸的工艺方法,包括：S1.包括含氧气氛、丙烯和水蒸气的原料气送至第一氧化反应器生成含丙烯醛的第一物流；S2.所述第一物流与含氧气氛再次混合后送至第二氧化反应器生成含丙烯酸的第二物流；S3.所述第二物流送至吸收塔获取含丙烯酸且呈液相的第三物流,以及呈气相的第四物流；S4.所述第三物流送至丙烯酸精制单元精制,所述第四物流送至焚烧单元处理生成含水蒸气的尾气,并将一部分所述尾气与所述原料气混合。循环尾气中含有一定量的水蒸气,因此适当控制循环尾气与加入水蒸气的比例,调节适宜的水与丙烯比例,有助于增强反应选择性,同时为装置降低能耗、降低生产成本有利。(The invention relates to a process method for preparing acrylic acid by propylene oxidation, which comprises the following steps: s1, feeding raw material gas comprising oxygen-containing atmosphere, propylene and water vapor to a first oxidation reactor to generate a first material flow containing acrolein; s2, mixing the first material flow with an oxygen-containing atmosphere again, and sending the mixture to a second oxidation reactor to generate a second material flow containing acrylic acid; s3, sending the second material flow to an absorption tower to obtain a third material flow containing acrylic acid and in a liquid phase and a fourth material flow in a gas phase; and S4, sending the third material flow to an acrylic acid refining unit for refining, sending the fourth material flow to an incineration unit for treatment to generate tail gas containing water vapor, and mixing a part of the tail gas with the raw material gas. The circulating tail gas contains a certain amount of water vapor, so that the proportion of the circulating tail gas and the added water vapor is properly controlled, the proper proportion of water and propylene is adjusted, the reaction selectivity is favorably enhanced, and meanwhile, the energy consumption and the production cost of the device are favorably reduced.)

1. A process for preparing acrylic acid by oxidizing propylene comprises the following steps:

s1, feeding raw material gas comprising oxygen-containing atmosphere, propylene and water vapor to a first oxidation reactor to generate a first material flow containing acrolein;

s2, mixing the first material flow with an oxygen-containing atmosphere again, and sending the mixture to a second oxidation reactor to generate a second material flow containing acrylic acid;

s3, sending the second material flow to an absorption tower to obtain a third material flow containing acrylic acid and in a liquid phase and a fourth material flow in a gas phase;

and S4, sending the third material flow to an acrylic acid refining unit for refining, sending the fourth material flow to an incineration unit for treatment to generate tail gas containing water vapor, and mixing a part of the tail gas with the raw material gas.

2. The process for preparing acrylic acid by oxidizing propylene according to claim 1, wherein in step S4, the temperature of the tail gas mixed with the raw material gas is 100-200 ℃.

3. The process for preparing acrylic acid by oxidizing propylene according to claim 2, wherein in step S4, the content of water vapor in the tail gas mixed with the raw material gas is 8-40% of the total amount of water vapor participating in the reaction in the first oxidation reactor.

4. The process for preparing acrylic acid by oxidizing propylene according to claim 3, wherein in step S1, the ratio of water vapor to propylene in the feed gas is 0.8-2.0.

5. The process for preparing acrylic acid by oxidizing propylene according to claim 4, wherein the steam in said first oxidation reactor is 5% to 20% of the total gas.

6. The process for preparing acrylic acid by oxidizing propylene according to claim 5, wherein said oxygen-containing atmosphere is oxygen or air.

7. The process for preparing acrylic acid by oxidizing propylene according to claim 6, wherein the exothermic heat of reaction in said first reactor is carried out of the reactor by a molten salt comprising sodium nitrite and potassium nitrate.

8. The process for the oxidation of propylene to acrylic acid as claimed in claim 7, wherein in step S2, the first stream is cooled and then mixed again with an oxygen-containing atmosphere.

Technical Field

The invention relates to the field of chemical industry, in particular to a process method for preparing acrylic acid by oxidizing propylene.

Background

Acrylic acid is a very important chemical raw material, and can be used for producing acrylic esters, high-performance water-absorbent resins, daily chemical additives and the like. The industrial production of acrylic acid has gone through a number of stages, and early production methods include a chlorohydrin method, a cyanoethanol method, a high-pressure Reppe method, a ketene method, a modified Reppe method, a formaldehyde-acetic acid method, a propylene hydrolysis method, an ethylene method, and the like, and the currently mainstream production method is a propylene oxidation method. The oxidation of propylene to produce acrylic acid is divided into a one-step oxidation process and a two-step oxidation process.

The two-step oxidation process is currently used industrially. The two-step oxidation process comprises: the first step is that propylene is oxidized to generate acrolein under the action of air and a catalyst, and the second step is that the acrolein is further oxidized to generate acrylic acid under the action of air and a catalyst. The mixed gas entering the first reactor should contain a certain amount of water vapor, and the water vapor is also indispensable for playing the role. Because the water vapor has larger specific heat capacity, the reaction heat can be effectively removed and taken out of the reactor; and flammable gases such as propylene and the like can be diluted, so that the reaction is prevented from being carried out in an explosion area. In the traditional production process, water vapor is supplied from the outside, the use amount is large, the storage is not easy, and the production cost of acrylic acid is increased.

Disclosure of Invention

The invention aims to provide a process method for preparing acrylic acid by oxidizing propylene, which reduces the production cost of the acrylic acid.

In order to achieve the above object, the present invention provides a process for preparing acrylic acid by oxidizing propylene, comprising:

s1, feeding raw material gas comprising oxygen-containing atmosphere, propylene and water vapor to a first oxidation reactor to generate a first material flow containing acrolein;

s2, mixing the first material flow with an oxygen-containing atmosphere again, and sending the mixture to a second oxidation reactor to generate a second material flow containing acrylic acid;

s3, sending the second material flow to an absorption tower to obtain a third material flow containing acrylic acid and in a liquid phase and a fourth material flow in a gas phase;

and S4, sending the third material flow to an acrylic acid refining unit for refining, sending the fourth material flow to an incineration unit for treatment to generate tail gas containing water vapor, and mixing a part of the tail gas with the raw material gas.

According to an aspect of the present invention, in the step S4, the temperature of the tail gas mixed with the raw material gas is 100 to 200 ℃.

According to one aspect of the invention, in the step S4, the content of water vapor in the tail gas mixed with the raw material gas is 8-40% of the total amount of water vapor participating in the reaction in the first oxidation reactor.

According to an aspect of the present invention, in step S1, the ratio of the water vapor to the propylene content in the feed gas is 0.8 to 2.0.

According to one aspect of the invention, the proportion of water vapour in the first oxidation reactor is between 5% and 20% of all gases.

According to one aspect of the invention, the oxygen-containing atmosphere is oxygen or air.

According to one aspect of the invention, the exothermic heat of reaction in the first reactor is carried out of the reactor by a molten salt consisting of sodium nitrite and potassium nitrate.

According to one aspect of the invention, in step S2, the first stream is cooled and then mixed again with an oxygen containing atmosphere.

According to one scheme of the invention, the content of the water vapor in the initial reaction process is set to be in the range, so that the normal operation of the reaction can be effectively ensured. In addition, through the arrangement, the desorption of the reaction product at the active site of the catalyst by the water vapor can be effectively ensured, so that the reaction process is accelerated, and the reaction selectivity is improved. Therefore, it is advantageous to properly control the water vapor content so that the ratio of water to propylene is as described above to enhance the reaction selectivity and to reduce the energy consumption of the apparatus.

According to one scheme of the invention, the temperature of the tail gas is controlled within the range, so that the moderate temperature of the water vapor in the tail gas is effectively ensured, particularly when the tail gas is added into the first reactor, the temperature of the water vapor is ensured to be favorable for ensuring the normal reaction, and the influence on reaction products due to the over-low or over-high temperature of the water vapor is avoided. In addition, the tail gas is controlled within the temperature range, so that the tail gas is prevented from being heated, the energy is saved, and the energy consumption and the production cost are reduced.

According to one embodiment of the invention, part of the offgas is recycled to the reactor as part of the feed gas composition. The circulating tail gas contains a certain amount of water vapor, so that the proportion of the circulating tail gas and the added water vapor is properly controlled, the proper proportion of water and propylene is adjusted, the reaction selectivity is favorably enhanced, and meanwhile, the energy consumption, the waste water discharge and the production cost of the device are reduced. Therefore, the water-olefin ratio is optimized to control the water vapor content in the circulating tail gas, and further the redundant water vapor content in the feed gas is controlled, so that energy conservation and emission reduction are necessary.

Drawings

FIG. 1 is a schematic flow diagram of a process for the oxidation of propylene to acrylic acid according to one embodiment of the present invention.

Detailed Description

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship that is based on the orientation or positional relationship shown in the associated drawings, which is for convenience and simplicity of description only, and does not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus, the above-described terms should not be construed as limiting the present invention.

The present invention is described in detail below with reference to the drawings and the specific embodiments, which are not repeated herein, but the embodiments of the present invention are not limited to the following embodiments.

As shown in FIG. 1, according to one embodiment of the present invention, a process for producing acrylic acid by oxidizing propylene comprises:

s1, feeding raw material gas comprising oxygen-containing atmosphere, propylene and water vapor to a first oxidation reactor to generate a first material flow containing acrolein;

s2, mixing the first material flow with an oxygen-containing atmosphere again, and sending the mixture to a second oxidation reactor to generate a second material flow containing acrylic acid;

s3, sending the second material flow to an absorption tower to obtain a third material flow containing acrylic acid and in a liquid phase and a fourth material flow in a gas phase;

and S4, sending the third material flow to an acrylic acid refining unit for refining, sending the fourth material flow to an incineration unit for treatment to generate tail gas containing water vapor, and mixing part of the tail gas with the raw material gas.

According to one embodiment of the invention, the molecular oxygen-containing atmosphere is compressed by an air compressor and fed into a feed mixer, where it is thoroughly mixed with a feed gas comprising superheated propylene and preheated water and fed into a first oxidation reactor, where propylene and oxygen are reacted under the action of a ring catalyst to form a first stream comprising acrolein. The heat released by the reaction is carried out of the reactor by the molten salt consisting of sodium nitrite and potassium nitrate. The first stream is in gaseous form and is cooled to a certain temperature in an outlet cooler of the first oxidation reactor before leaving the reactor. Then mixing the mixture with the atmosphere containing molecular oxygen again in the second mixer, and then feeding the mixture into a second oxidation reactor, and continuously carrying out selective oxidation reaction under the action of a two-stage spherical catalyst to generate a second stream containing acrylic acid. And cooling the product by a cooler, then feeding the product into an absorption tower, absorbing the second stream in the absorption tower to form a solution, sending the solution to an acrylic acid refining unit through the tower bottom, and directly carrying out catalytic incineration treatment on all the fourth stream which is not absorbed at the tower top. In the present embodiment, the content ratio of water vapor to propylene in the raw material gas is 0.8 to 2.0. In this embodiment, the ratio of the water vapor to the propylene in the raw material gas is controlled in the range of 0.8 to 2.0, and the conversion of propylene and the yield of intermediate products are remarkably improved, as shown in table 1 below.

TABLE 1

As can be seen from the above table, the ratio of the water vapor to the propylene in the feed gas was controlled in the range of 0.8 to 2.0, and the conversion of propylene and the yield of the intermediate product were maintained at high levels. Through the setting, the content of the water vapor in the initial reaction process is set to be within the range, and the normal operation of the reaction can be effectively ensured. In addition, through the arrangement, the desorption of the reaction product at the active site of the catalyst by the water vapor can be effectively ensured, so that the reaction process is accelerated, and the reaction selectivity is improved. Therefore, it is advantageous to properly control the water vapor content so that the ratio of water to propylene is as described above to enhance the reaction selectivity and to reduce the energy consumption of the apparatus.

According to one embodiment of the invention, after the fourth stream is incinerated into carbon dioxide, water and the like which reach the standard, one part is discharged to the atmosphere, the other part controls the content of water vapor, one part of tail gas with stable water vapor content is recycled to the mixer in front of the first reactor after being controlled to a certain temperature, and the water vapor in the tail gas enters the first reactor to be mixed with the raw material gas after being controlled to the optimal ratio, so that the cyclic utilization of the water vapor in the tail gas is realized. In the present embodiment, the temperature of the exhaust gas mixed with the raw material gas is 100 to 200 ℃. Through the arrangement, the temperature of the tail gas is controlled within the range, the moderate temperature of the water vapor in the tail gas is effectively ensured, particularly when the tail gas is added into a first reactor, the temperature of the water vapor is ensured to be favorable for ensuring the normal reaction, and the influence on reaction products caused by the over-low or over-high temperature of the water vapor is avoided. In addition, the tail gas is controlled within the temperature range, so that the tail gas is prevented from being heated, the energy is saved, and the energy consumption and the production cost are reduced.

According to one embodiment of the invention, the content of water vapor in the tail gas mixed with the raw material gas is 8-40% of the total amount of water vapor participating in the reaction in the first oxidation reactor. By the arrangement, part of tail gas is recycled to the reactor to be used as one part of the composition of the raw material gas. The circulating tail gas contains a certain amount of water vapor, so that the proportion of the circulating tail gas and the added water vapor is properly controlled, the proper proportion of water and propylene is adjusted, the reaction selectivity is favorably enhanced, and meanwhile, the energy consumption of the device is reduced, and the wastewater discharge is favorably reduced. Therefore, the water-olefin ratio is optimized to control the water vapor content in the circulating tail gas, and further the redundant water vapor content in the feed gas is controlled, so that energy conservation and emission reduction are necessary.

According to one embodiment of the invention, the proportion of water vapour in the first oxidation reactor is between 5% and 20% of the total gas. The content of the water vapor is set to be within the range, so that the normal reaction can be effectively ensured. In addition, through the arrangement, the desorption of the reaction product at the active site of the catalyst by the water vapor can be effectively ensured, so that the reaction process is accelerated, and the reaction selectivity is improved. Therefore, it is advantageous to properly control the water vapor content so that the ratio of water to propylene is as described above to enhance the reaction selectivity and to reduce the energy consumption of the apparatus.

According to one embodiment of the invention, the oxygen-containing atmosphere is oxygen or air. By using oxygen or air, it is convenient to obtain, has low cost, and is beneficial to the large-scale production of the process of the invention.

The foregoing is merely exemplary of particular aspects of the present invention and devices and structures not specifically described herein are understood to be those of ordinary skill in the art and are intended to be implemented in such conventional ways.

The above description is only one embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.