WO2016180085A1

WO2016180085A1 - Formaldehyde absorption process device and method in polyoxymethylene dimethyl ether synthesis

Info

Publication number: WO2016180085A1
Application number: PCT/CN2016/076961
Authority: WO
Inventors: 叶子茂; 向家勇
Original assignee: 江苏凯茂石化科技有限公司
Priority date: 2015-05-14
Filing date: 2016-03-22
Publication date: 2016-11-17
Also published as: CN104817440A; CN104817440B

Abstract

Disclosed are a formaldehyde absorption process device and method in polyoxymethylene dimethyl ether synthesis. In the process, higher-boiling-point intermediate component dimer PODE2 of polyoxymethylene dimethyl ether is used, and the amount of dissolved formaldehyde is much higher than that of methylal, so as to obtain a PODE2 solution of formaldehyde, so that operation pressures and temperatures in subsequent reactions are on lower levels, thereby avoiding the self-polymerization and disproportionation reaction of the formaldehyde, further, avoiding the pipeline blockage, lowering the acid content in the polyoxymethylene dimethyl ether product, and finally improving the yield of the product.

Description

Formaldehyde absorption process device and method for synthesizing polymethoxy dimethyl ether

Technical field

The invention belongs to the technical field of chemical production process and equipment, and mainly relates to a production process of polymethoxy dimethyl ether.

Background technique

Formaldehyde is one of the most important downstream products of methanol, and methanol is an important downstream product of coal. Therefore, formaldehyde has become an important development branch in the field of energy and chemical industry. Formaldehyde is a raw material for a variety of chemical products, and currently exists in the form of 37% formaldehyde aqueous solution on the market. The presence of large amounts of water not only affects the quality of certain chemical products, but also affects related reactions, causing a large number of unnecessary by-products or causing low conversion rates. At the same time, dehydration brings about high energy consumption, so the existence of a large amount of water limits the use of formaldehyde.

In the past, the formation of paraformaldehyde and paraformaldehyde was costly and the process was complicated. Both paraformaldehyde and paraformaldehyde are solid, and there is certain dust pollution in production and transportation, which is harmful to the environment and personnel. Even in the process of synthesizing polymethoxy dimethyl ether from formaldehyde and methylal, the reaction is a liquid phase reaction. Therefore, the formaldehyde gas is dissolved in the methylal/methanol/dimethyl ether providing the capping to react. The use of methylal as a blocking compound, due to the relatively low boiling point of methylal, formaldehyde solubility in the methylal is limited. If the solubility of formaldehyde in the methylal is exceeded, formaldehyde is present in a large amount in the gas phase, which will cause polymerization of formaldehyde.

The usual approach is to use high pressure to increase the boiling point of the methylal. Pressurization leads to an increase in equipment cost, and the increase in pressure corresponds to an increase in temperature. The high temperature of formaldehyde tends to cause disproportionation to form formic acid.

Summary of the invention

OBJECTS OF THE INVENTION: In view of the above problems and drawbacks, the present invention provides a formaldehyde absorption process apparatus and method for synthesizing polymethoxy dimethyl ether, which completely overcomes the low solubility of formaldehyde in methylal and is easily caused to be absorbed. The problem of formaldehyde polymerization or disproportionation reaction.

Technical Solution: In order to achieve the above object, the present invention adopts the following technical scheme: a formaldehyde absorption process device for polymethoxy dimethyl ether synthesis, comprising an absorption tower, a reactor, a flash tower and a de-light tower, the absorption The top of the tower is provided with a PODE2 feed port, and the bottom of the tower is provided with a formaldehyde gas feed pipe and an absorption liquid outlet, and the formaldehyde gas feed pipe is inserted below the liquid surface; the absorption liquid outlet of the bottom of the absorption tower is sequentially connected through the pipeline The reactor, the flash column and the de-lighting tower are connected; the absorption liquid outlet is further provided with a methylal compounding pipe; and the top of the de-lighting tower is further provided with a vacuuming device.

The bottom of the de-lighting tower is provided with a product outlet and is connected with a fine separation device.

The top of the de-lighting tower is provided with a production outlet, and a reflux tank is connected through the condensation pipeline, and a part of the production liquid circulating from the production outlet is pumped back to the light tower.

The invention also provides a polymethoxy dimethyl ether synthesis process based on the process device, comprising the following steps:

(1) using PODE2 and formaldehyde gas as reaction raw materials, the formaldehyde gas is bubbled into the PDDE2 liquid, and the PODE2 is sprayed from the top pump to absorb the formaldehyde gas to obtain a formaldehyde content of 10 to 50%. PODE2 absorption liquid;

(2) feeding the absorption liquid into the reactor to react PODE2 with formaldehyde in the liquid phase to synthesize polymethoxy dimethyl ether, and obtain a reaction liquid containing a large amount of methylal;

(3) The reaction liquid is sent to a flash column, and the methylal is obtained from the top of the column by flash removal, and recycled;

(4) The reaction liquid separated by methylal is sent to the de-lighting tower, and in a vacuum state, 90-120 ° C, formaldehyde is not vaporized, the PODE2 solution containing 5-10% of formaldehyde is separated from the top of the column. A mixture of polymethoxy dimethyl ether and formaldehyde was obtained from the bottom of the column.

Step (4) A mixture of polymethoxy dimethyl ether and formaldehyde is obtained and sent to a fine separation apparatus to obtain polymethoxy dimethyl ether.

The operating conditions in the absorption tower in the step (1) are 50 to 90 ° C, atmospheric pressure.

The operating pressure of the reactor in the step (2) is 0.1 to 0.5 MPa, and the reaction temperature is 50 to 120 ° C.

Advantageous Effects: Compared with the prior art, the present invention utilizes a higher boiling point polymethoxy dimethyl ether intermediate component dimer PODE2 to dissolve formaldehyde, and obtains a PODE2 solution of formaldehyde, so that the operating pressure and temperature of the subsequent reaction are at The lower level avoids the self-polymerization and disproportionation of formaldehyde, thereby avoiding clogging of the pipeline and reducing the acid content of the polymethoxy dimethyl ether product, ultimately increasing the yield of the product.

DRAWINGS

1 is a schematic structural view of an apparatus for absorbing and catalyzing a reaction of formaldehyde according to the present invention;

2 is a structural view of a process apparatus for flashing and de-lighting of a reaction liquid according to the present invention.

Among them, the absorption tower 1, the reactor 2, the flash tower 3, and the light removal tower 4.

detailed description

The invention will be further clarified with reference to the drawings and specific embodiments, which are to be construed as illustrative only and not to limit the scope of the invention. Modifications of equivalent forms are intended to fall within the scope defined by the appended claims.

The intermediate component dimer PODE2 of polymethoxy dimethyl ether with higher boiling point is selected in the process. PODE2 has a boiling point of 105 ° C, and the amount of dissolved formaldehyde is much higher than the amount of methylal dissolved. It can completely solve the problem that the formaldehyde gas phase is not absorbed and then polymerized. The chemical reaction process of the synthesis of formaldehyde and methylal to obtain polymethoxy dimethyl ether is as follows:

The formaldehyde absorption process for the synthesis of polymethoxy dimethyl ether according to the invention has the following characteristics:

1) The methyl acetal has a low boiling point. To achieve the reaction of formaldehyde and methylal in the liquid phase, it is necessary to avoid the possibility that the temperature caused by the pressure is high and the formaldehyde is disproportionated. The invention uses the polymethoxy dimethyl ether intermediate component PODE2 as an absorbent for formaldehyde. PODE2 has a boiling point of 105 ° C and can dissolve formaldehyde up to 60% under normal pressure without polymerization. At normal pressure, the amount of formaldehyde dissolved in methylal is only 10-20%.

2) The reaction in the formation of polymethoxy dimethyl ether is an equilibrium conversion reaction, and formaldehyde is inevitably contained in the reaction liquid. The separation of PODE2 without formaldehyde has become a difficult point. Usually, the reaction liquid is used to elute formaldehyde, and then the distillation method is used to obtain PODE2. This method consumes a large amount of formaldehyde and produces more waste. The invention adopts the method of vacuum distillation to obtain a low content of PODE2 as a solution for absorbing formaldehyde.

As shown in Figures 1 and 2, the formaldehyde gas enters the bubble absorption from the bottom of the absorption tower, and the PODE2 is added from the top of the tower, absorbed by the pump spray, and reaches a certain formaldehyde concentration (controlling the formaldehyde content 10-50%). In the process, the absorption of formaldehyde is firstly carried out by bubbling method, and the spray of the PODE2 is added from top to bottom to maximize the avoidance of self-polymerization of the unabsorbed formaldehyde monomer, especially the polymerization of the inner wall of formaldehyde to form a deeper scale. Polymerization of formaldehyde. And the appropriate ratio of reaction with methylal is pumped into the reactor for reaction. In the above process, the operating pressure of the absorption tower is atmospheric pressure operation, the temperature is 50-90 ° C; the reactor operating pressure is 0.1-0.5 Mpa, and the reaction temperature is 50-120 ° C.

The resulting reaction solution contained a large amount of methylal, which was recycled by flash distillation. Pumped into the de-lighting tower, under vacuum, at a temperature of 90-120 ° C, under the condition that formaldehyde is not vaporized, PODE2 is taken out from the top of the de-lighting tower to obtain a mixed gas containing about 5-10% of formaldehyde and PODE2. After the condensed part is refluxed, the remaining part is recycled to the absorption tower for additional addition; the bottom of the column is a mixture of the product and formaldehyde, and further separated by a fine separation device to obtain a higher purity polymethoxy dimethyl ether according to the product requirements. product.

Claims

A formaldehyde absorption process device for synthesizing polymethoxy dimethyl ether, comprising: an absorption tower, a reactor, a flash tower and a de-lighting tower, wherein the top of the absorption tower is provided with a PODE2 feed port, and the bottom of the tower Forming a formaldehyde gas feed pipe and an absorption liquid outlet, the formaldehyde gas feed pipe is inserted below the liquid surface; the absorption liquid outlet of the bottom of the absorption tower is sequentially connected to the reactor, the flash tower and the de-light tower through a pipeline; The absorption liquid outlet is further provided with a methylal compounding pipe; the top of the de-lighting tower is further provided with a vacuuming device.
The process apparatus according to claim 1, wherein the bottom of the de-lighting tower is provided with a product outlet and is connected with a fine separation device.
The process device according to claim 1, wherein the top of the de-lighting tower is provided with a production outlet, and a reflux tank is connected through the condensation pipeline, and a part of the production liquid circulating from the production outlet is pumped back to the light tower. .
A polymethoxy dimethyl ether synthesis process according to any one of claims 1 to 3, characterized in that it comprises the following steps:

(1) using PODE2 and formaldehyde gas as reaction raw materials, the formaldehyde gas is bubbled into the PDDE2 liquid, and the PODE2 is sprayed from the top pump to absorb the formaldehyde gas to obtain a formaldehyde content of 10 to 50%. PODE2 absorption liquid;

(2) feeding the absorption liquid into the reactor to react PODE2 with formaldehyde in the liquid phase to synthesize polymethoxy dimethyl ether, and obtain a reaction liquid containing a large amount of methylal;

(3) The reaction liquid is sent to a flash column, and the methylal is obtained from the top of the column by flash removal, and recycled;

(4) The reaction liquid separated by methylal is sent to the de-lighting tower, and in a vacuum state, 90-120 ° C, formaldehyde is not vaporized, the PODE2 solution containing 5-10% of formaldehyde is separated from the top of the column. A mixture of polymethoxy dimethyl ether and formaldehyde was obtained from the bottom of the column.
The process according to claim 4, wherein the step (4) comprises obtaining a mixture of polymethoxy dimethyl ether and formaldehyde and feeding the mixture into a fine separation device to obtain polymethoxy dimethyl ether.
The process according to claim 4, characterized in that the operating condition in the absorption column in the step (1) is 50 to 90 ° C, atmospheric pressure.
The process according to claim 4, wherein the operating pressure of the reactor in the step (2) is 0.1 to 0.5 MPa, and the reaction temperature is 50 to 120 °C.