CN112521255A

CN112521255A - Preparation method of polyoxymethylene dimethyl ether and mixture thereof

Info

Publication number: CN112521255A
Application number: CN201910884450.4A
Authority: CN
Inventors: 蔡依进; 王兴路; 蔡依超; 郑吉振; 孙华; 李文强; 张月凤
Original assignee: Shandong Chenxin New Energy Co ltd
Current assignee: Shandong Chenxin New Energy Co ltd
Priority date: 2019-09-19
Filing date: 2019-09-19
Publication date: 2021-03-19
Anticipated expiration: 2039-09-19
Also published as: CN112521255B

Abstract

The invention belongs to the technical field of energy and chemical industry, and provides a preparation method of a fuel additive and an environment-friendly solvent, namely polyoxymethylene dimethyl ether (DMMn, general n = 2-8) and a mixture thereof, which comprises the following steps: mixing a formaldehyde water solution, polyhydric alcohol and the macromolecule used in the previous batch according to a certain proportion, heating under a vacuum condition to remove moisture to obtain anhydrous flowable polyformaldehyde etherate, carrying out catalytic reaction on the anhydrous etherate with methylal, the low-boiling-point substance used in the previous batch, the macromolecule and the like at a certain temperature in the presence of a catalyst, filtering out the catalyst after the reaction is balanced, respectively carrying out normal-pressure and reduced-pressure distillation, separating out the low-boiling-point substance, the macromolecule and a DMMn finished product, and carrying out reduced-pressure rectification on the DMMn finished product to obtain single components. Returning the low-boiling-point substance and the macromolecule obtained by separation, and applying the low-boiling-point substance and the macromolecule to the synthesis of the next batch.

Description

Preparation method of polyoxymethylene dimethyl ether and mixture thereof

Technical Field

The invention belongs to the technical field of energy and chemical industry, and particularly designs a preparation method of polyoxymethylene dimethyl ethers and a mixture thereof. .

Background

Polyoxymethylene dimethyl ether is also called polyoxymethylene dimethyl ether, and English name: polyoxymethylene dimethyl ethers, PODE or DMMn for short, are low molecular weight acetal polymers with dimethoxymethane as the matrix and methyleneoxy as the main chain, and the general formula is shown as follows: CH3O (CH2O) nCH 3. The polymethoxy dimethyl ether with the polymerization degree of 2-8, DMMn (n = 2-8) for short, is used for cleaning diesel blending components, has physical properties similar to those of diesel, and is used in blending the diesel without modifying an oil supply system of a vehicle engine. The cetane number of the diesel oil reaches 76, the oxygen content is 47-50%, the diesel oil is free of sulfur and aromatic hydrocarbon, the diesel oil can be blended in the diesel oil by 10-20%, the cold filter plugging point of the diesel oil can be obviously reduced, the combustion quality of the diesel oil in an engine can be improved, and the thermal efficiency is improved. Meanwhile, DMM2, DMM3, DMM4 and DMM5 are solvents with extremely high dissolving capacity, and are applied to paint, coating, printing ink, adhesive, cleaning agent, electrolyte solvent and the like.

Polyoxymethylene dimethyl ethers (DMM 2-8) are typically prepared by reacting methanol or methylal with trioxymethylene or paraformaldehyde in the presence of an acidic catalyst, the basic equation for the reaction being as follows:

however, trioxymethylene is synthesized by using sulfuric acid as a catalyst, a large amount of backflow is performed in the production process under the condition of water, the vaporization heat of water is large, the energy consumption is high, solvent extraction and dehydration are also needed, the synthesis cost is high, the melting point of trioxymethylene is high (61 ℃), the trioxymethylene is easy to sublimate, and the pipeline is easy to block;

the paraformaldehyde is in a solid form prepared by the procedures of vacuum dehydration, polymerization, granulation or crushing, drying and the like of an aqueous solution of formaldehyde, although the manufacturing cost is reduced, the paraformaldehyde is further used as a reactant, has low reaction activity due to the insolubility and infusibility, is inconvenient to feed from synthesis to application in the continuous production process, has large formaldehyde odor and high toxicity, and is harmful to the health of workers. .

The domestic report of preparing polyoxymethylene dimethyl ether (DMM 3-8) by reacting formaldehyde aqueous solution with higher concentration with methanol or methylal also has the advantages of smooth process and convenient operation in theory, but the process is immature and difficult to realize industrialization due to the existence of a large amount of water, low equilibrium conversion rate, large amount of residual formaldehyde and difficult separation.

Disclosure of Invention

(1) The purpose of the invention is as follows: the invention aims to solve a series of problems in the existing synthesis of polyoxymethylene dimethyl ether by using paraformaldehyde, trioxymethylene or formaldehyde aqueous solution, and provides a new synthesis technical route and a new process.

(2) The technical scheme is as follows: the invention relates to a method for preparing polyoxymethylene dimethyl ether and a mixture thereof, which comprises the steps of mixing a formaldehyde aqueous solution, polyhydric alcohol and a previous batch of macromolecules applied mechanically according to a certain proportion, heating under a vacuum condition to remove moisture to obtain an almost anhydrous flowable polyformaldehyde etherate with low polymerization degree, carrying out catalytic reaction on the anhydrous etherate with methylal, the previous batch of low-boiling-point substances applied mechanically, the macromolecules and the like under the presence of a catalyst at a certain temperature, filtering out the catalyst after the reaction is balanced, carrying out normal pressure and reduced pressure distillation respectively, separating out the low-boiling-point substances, the macromolecules and DMMn finished products, and carrying out reduced pressure rectification on the DMMn finished products to obtain single components. Returning the low-boiling-point substance and the macromolecule obtained by separation, and applying the low-boiling-point substance and the macromolecule to the synthesis of the next batch.

The basic reaction scheme is as follows:

(3) the technical effects are as follows: the preparation method of the polyoxymethylene dimethyl ethers and the mixtures thereof has the advantages of easily available raw materials, simplicity, effectiveness, convenience for realizing continuity and automation, higher yield, lower cost, small wastewater pollution, safety, environmental protection and suitability for industrial production.

The concrete aspects are as follows:

1. the invention adopts the formaldehyde aqueous solution (or the gaseous formaldehyde synthesis gas) as the raw material of the formaldehyde source, so that the production is simpler and the product cost is lower.

2. The formaldehyde of the invention is still liquid which is easy to flow after the water is simply removed, thus being convenient for realizing continuous production and automatic control.

3. The reaction process of the invention is properly controlled, and the yield is higher.

4. The capacity of a single set of continuous device can be larger.

5. The invention can use solid acid catalyst, which has good catalytic effect, safety and environmental protection.

The specific implementation mode of the invention is as follows:

example 1:

mixing 800g of 37% formaldehyde water solution and 60g of ethylene glycol, removing moisture at the temperature of below 95 ℃ under a vacuum condition to obtain 326.4g of anhydrous flowable polyformaldehyde etherate, transferring the flowable polyformaldehyde etherate into a mixture containing 10g of acidic sulfonic acid resin and 560g of methylal, carrying out catalytic reaction at the temperature of 50-80 ℃, filtering out a catalyst after the reaction reaches equilibrium to obtain 866.4g of reaction liquid, distilling 583.4g of DMM1, DMM2 and the like under normal pressure, distilling 161g of DMM3-8 at-0.098 MP, and using 97g of residual macromolecules for batch synthesis.

Example 2:

mixing 800g of 37% formaldehyde water solution and 120g of ethylene glycol, removing moisture at the temperature of below 95 ℃ under a vacuum condition to obtain 391.5g of anhydrous flowable polyformaldehyde etherate, transferring the flowable polyformaldehyde etherate into a mixture containing 10g of acidic sulfonic acid resin and 800g of methylal, carrying out catalytic reaction at the temperature of 50-80 ℃, filtering out a catalyst after the reaction reaches equilibrium to obtain 1152.5g of reaction liquid, distilling out 644.5g of DMM1, DMM2 and the like under normal pressure, distilling 328g of DMM3-8 at-0.098 MP, and using 158g of residual macromolecules for batch synthesis.

Example 3:

744.5g of DMM1, DMM2 and the like obtained in the previous batch are subjected to special separation under normal pressure to obtain 404.5g of DMM1 and the like (which can be applied to the synthesis of the next batch); 25g of methanol water and the like (can be used for synthesizing methylal) are obtained; DMM2, etc. 308.5g (applicable for next batch synthesis).

Example 4:

mixing 800g of 37% formaldehyde water solution, 70 g of ethylene glycol and 134g of macromolecules in the previous batch, removing moisture at the temperature of below 95 ℃ under a vacuum condition to obtain 443.8g of anhydrous flowable polyformaldehyde etherate, transferring the flowable polyformaldehyde etherate into a mixture of 10g of acidic sulfonic acid resin, 920g of methylal and 279g of recovered DMM2 and the like, carrying out catalytic reaction at the temperature of 50-80 ℃, filtering out a catalyst after the reaction reaches equilibrium to obtain 1621.8g of reaction liquid, and distilling 647.4g of DMM1 and the like at normal pressure; 496.3g of DMM2 was added, and 323.5g of DMM3-8 and 119.6g of residual macromolecule were distilled off at-0.098 MP and used for the next batch of synthesis.

Example 5:

mixing 800g of 37% formaldehyde aqueous solution and 60g of glycerol, removing water at the temperature of below 95 ℃ under a vacuum condition to obtain 328.1g of anhydrous flowable polyformaldehyde etherate, transferring the flowable polyformaldehyde etherate into a mixture containing 10g of acidic sulfonic acid resin and 800g of methylal, carrying out catalytic reaction at the temperature of 50-80 ℃, filtering out a catalyst after the reaction reaches equilibrium to obtain 1113g of reaction liquid, distilling off 742.5g of DMM1, DMM2 and the like under normal pressure, steaming out 236.5g of DMM3-8 at-0.098 MP, and using the residual macromolecules 112g for batch synthesis.

Example 6:

mixing 800g of 37% formaldehyde aqueous solution and 60g of diethylene glycol, removing moisture at the temperature of below 95 ℃ under a vacuum condition to obtain 325.4g of anhydrous flowable polyformaldehyde etherate, transferring the flowable polyformaldehyde etherate into a mixture containing 10g of acidic sulfonic acid resin and 800g of methylal, carrying out catalytic reaction at the temperature of 50-80 ℃, filtering out a catalyst after the reaction reaches equilibrium to obtain 1106.4g of reaction liquid, distilling out 744.9g of DMM1, DMM2 and the like under normal pressure, steaming out 235.5g of DMM3-8 at-0.098 MP, and using 106g of residual macromolecules for batch synthesis.

Example 7:

mixing 800g of 37% formaldehyde aqueous solution and 60g of 1, 2-propylene glycol, removing moisture at the temperature of below 95 ℃ under vacuum to obtain 327 g of anhydrous flowable polyformaldehyde etherate, transferring the flowable polyformaldehyde etherate into a mixture of 10g of acidic sulfonic acid resin and 800g of methylal, carrying out catalytic reaction at the temperature of 50-80 ℃, filtering out a catalyst after the reaction reaches equilibrium to obtain 1110g of reaction liquid, distilling out 759g of DMM1, DMM2 and the like under normal pressure, distilling out 230g of DMM3-8 at-0.098 MP, and using residual macromolecules 102 for batch synthesis.

Example 8: (comparative example) 800g of an aqueous 37% formaldehyde solution was dewatered under vacuum at 95 ℃ or less to give 252 g of anhydrous, non-flowable paraformaldehyde particles, which was transferred to a mixture of 10g of an acidic sulfonic acid resin and 800g of methylal and subjected to a catalytic reaction at 50 to 80 ℃ for 24 hours, and still contained a large amount of paraformaldehyde particles, and the catalyst could not be isolated and further products could be obtained.

The invention solves the problems that the solid paraformaldehyde is difficult to prepare, transport and has low activity in the prior art which takes the paraformaldehyde as a raw material; the problems of high cost, serious equipment corrosion and risk of pipeline blockage when trioxymethylene is used as a raw material; and when the aqueous solution of formaldehyde is taken as the raw material, the equilibrium conversion rate is low, the contents of formaldehyde and hemiacetal are high, the finished product is difficult to separate, and the water accumulation can not be recycled; the invention is a technical achievement obtained by careful research and experimental verification under the condition that the company can not complete the low-cost synthesis of DMMn after largely researching various synthesis routes and synthesis technologies of DMMn, and finally, the invention has the advantages of easily obtained raw materials, simple and effective process, lower cost, simple and smooth process, higher synthesis conversion rate and easy separation. The invention has the advantages of low investment cost, low production and driving risk and rich operating profit.

Finally, it is to be noted that: although the present invention has been described in detail with reference to the foregoing examples, those skilled in the art may still modify the technical solutions described in the foregoing examples, or equivalently replace some technical features of the embodiments, or simply change the technical solutions of the present invention into continuous engineering. 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.

Claims

1. A process for the preparation of polyoxymethylene dimethyl ethers (DMMn, typically n = 2-8) and mixtures thereof comprises the following steps: mixing a formaldehyde water solution, polyhydric alcohol and the macromolecule of the previous batch for application according to a certain proportion, heating under a vacuum condition to remove moisture to obtain an anhydrous flowable polyformaldehyde etherate, carrying out catalytic reaction on the anhydrous polyformaldehyde etherate and methylal, the low-boiling-point substance of the previous batch for application, the macromolecule and the like at a certain temperature in the presence of an acid catalyst, filtering out the catalyst after the reaction reaches equilibrium, respectively carrying out normal-pressure distillation and reduced-pressure distillation to separate out the low-boiling-point substance, the macromolecule and a DMMn finished product, carrying out reduced-pressure rectification on the DMMn finished product to obtain single components, and returning the low-boiling-point substance and the macromolecule obtained by separation for application to the synthesis of the next batch.

2. The raw material as claimed in claim 1, wherein the polyhydric alcohol includes ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, diethylene glycol, glycerin, butylene glycol, pentaerythritol, neopentyl glycol, trimethylolpropane, etc.

3. The starting material as claimed in claim 1, which comprises, as aqueous formaldehyde solution: the formaldehyde solution in the commercial form and methanol are subjected to catalytic dehydrogenation and oxidation to form gaseous formaldehyde containing water vapor.

4. The starting materials as claimed in claims 1 and 3, the aqueous formaldehyde solution, has a formaldehyde content of from 5% to 85%, preferably from 30% to 70%.

5. The acid catalyst as claimed in claim 1 comprising: liquid acid catalyst, solid acid catalyst, gaseous acid catalyst.

6. The solid acid catalysts claimed in claims 1 and 5 include, but are not limited to: titanium silicalite, mordenite, sodium bisulfate, aluminum sulfate, ferric chloride, sulfonic acid resin, fluorosulfonic acid resin, silica gel particles having sulfuric acid and phosphoric acid adsorbed thereon, and mixtures thereof.

7. Formaldehyde as claimed in claim 1 is dehydrated with polyols and macromolecules to a moisture content of less than 10%, preferably less than 1.0%.

8. The ratio of formaldehyde (purified) to the polyhydric alcohol and the macromolecule as claimed in claim 1 is 1.0:0.1 to 10.0, preferably 1:0.2 to 1.8.

9. The catalytic reaction temperature as claimed in claim 1 is controlled at 30 ℃ to 180 ℃, preferably 50 ℃ to 80 ℃.

10. The macromolecules as claimed in claim 1 are used in the concentration of formaldehyde for the next synthesis or directly in the synthesis reaction.