阅读说明：本技术 一种聚甲氧基二甲醚（DMMn）的制备方法 (Preparation method of polymethoxy dimethyl ether (DMMn) ) 是由 蔡依进 王兴路 蔡依超 郑吉振 孙华 李文强 陈海龙 徐胜凯 张月凤 于 2019-09-27 设计创作，主要内容包括：本发明属于能源及化工技术领域,提供了一种燃油添加剂和环保溶剂---聚甲氧基二甲醚(DMMNn,一般n=3～8)的制备方法,包括以下过程：甲醛水溶液和多元醇按照一定比例混合后,真空条件下加热脱水一步制得含较低水分的流动聚甲醛,含较低水分的流动聚甲醛再经过加热气化得到较纯的气态甲醛,再由获得的气态甲醛在催化剂存在下和甲缩醛、套用的上批次低沸物和大分子等混合,在一定温度下发生催化反应,反应达到平衡后,滤出催化剂并净化合成液,分别进行常压及减压蒸馏,分离得低沸物、大分子和DMMn成品,DMMn成品再经减压精馏,可得到各单组分。甲醛气化后残余的多元醇返回,套用于下批的甲醛浓缩,去制备含较低水分的流动聚甲醛。(The invention belongs to the technical field of energy and chemical industry, and provides a preparation method of fuel additive and environment-friendly solvent-polymethoxy dimethyl ether (DMMNn, general n = 3-8), which comprises the following steps: mixing a formaldehyde aqueous solution and polyhydric alcohol according to a certain proportion, heating and dehydrating under a vacuum condition to prepare flowing polyformaldehyde with lower moisture in one step, heating and gasifying the flowing polyformaldehyde with lower moisture to obtain purer gaseous formaldehyde, mixing the obtained gaseous formaldehyde with methylal, the applied low-boiling-point substances and macromolecules and the like in the presence of a catalyst, carrying out catalytic reaction at a certain temperature, filtering out the catalyst and purifying a synthetic solution after the reaction is balanced, respectively carrying out normal-pressure distillation and reduced-pressure distillation, separating to obtain 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. The residual polyol after the formaldehyde is gasified is returned and applied to the concentration of the formaldehyde in the next batch to prepare the flowing polyformaldehyde with lower water content.)

1. A preparation method of polymethoxy dimethyl ether (DMMNn, generally n = 3-8) comprises the following steps: mixing a formaldehyde aqueous solution and polyhydric alcohol according to a certain proportion, heating and dehydrating under a vacuum condition to prepare flowing polyformaldehyde with lower water content in one step, heating and gasifying the flowing polyformaldehyde with lower water content to obtain purer gaseous formaldehyde, mixing the obtained gaseous formaldehyde with methylal, applied low-boiling-point substances and macromolecules and the like in the presence of a catalyst, carrying out catalytic reaction at a certain temperature, filtering out the catalyst and purifying a synthetic solution after the reaction is balanced, respectively carrying out normal-pressure distillation and reduced-pressure distillation to separate out the low-boiling-point substances, the macromolecules and DMMn finished products, carrying out reduced-pressure rectification on the DMMn finished products to obtain single components, returning the residual polyhydric alcohol after the formaldehyde is gasified, applying the residual polyhydric alcohol to the formaldehyde concentration of the next batch, and preparing the flowing polyformaldehyde with lower water content.

2. The polyol as claimed in claim 1 comprises ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, diethylene glycol, glycerol, butanediol, neopentyl glycol, trimethylolpropane and a mixture of two or more thereof.

3. The aqueous formaldehyde solution as claimed in claim 1, comprising: aqueous formaldehyde, methanol in commercial form, is formed by catalytic dehydrogenation or oxidation to form gaseous formaldehyde containing water vapor, hydrogen, methanol.

4. The aqueous formaldehyde solutions as claimed in claims 1 and 3 have a formaldehyde content of from 10% to 85%, preferably from 30% to 70%.

5. The mixture of formaldehyde and polyol as claimed in claim 1 is dehydrated to a moisture content of less than 15%, preferably less than 1.0%.

6. The dehydration temperatures of the mixtures of formaldehyde and polyols as claimed in claims 1 and 5 are generally from 30 ℃ to 110 ℃ and preferably from 60 ℃ to 100 ℃.

7. The process of claim 1 wherein the fluidized polyoxymethylene produced is heated to a temperature of from about 110 ℃ to about 300 ℃, preferably from about 120 ℃ to about 180 ℃.

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

9. The solid acid catalyst as claimed in claims 1 and 8 comprising: 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.

10. The ratio of formaldehyde (purified) to polyol as claimed in claim 1 is from 1.0:0.02 to 20.0, preferably from 1:0.2 to 2.0.

11. The catalytic reaction temperature as claimed in claim 1 is generally from 30 ℃ to 200 ℃, preferably from 50 ℃ to 120 ℃.

Technical Field

The invention belongs to the technical field of energy and chemical industry, and particularly designs a preparation method of polymethoxy dimethyl ether (DMMn, generally n = 3-8).

Background

Polyoxymethylene dimethyl ether, also known as paraformaldehyde dimethyl ether, 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 polyoxymethylene dimethyl ethers with the polymerization degree of 3-8, DMM3-8 for short, is used for cleaning diesel blending components, has physical properties similar to diesel, and is used for blending into 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, DMM3, DMM4, DMM5 and DMM3-8 are solvents with extremely strong dissolving capacity, and are applied to paint, coating, printing ink, adhesive, cleaning agent, electrolyte solvent and the like.

Polyoxymethylene dimethyl ethers are generally prepared by reacting methanol or methylal with trioxymethylene or paraformaldehyde in the presence of an acidic catalyst, and the basic equation is as follows:

the process of synthesizing polymethoxy dimethyl ether catalyzed by an acid catalyst is an equilibrium reaction, the existence of a small amount of water promotes the equilibrium to move reversely, so that a large amount of formaldehyde, methanol, hemiacetal and the like are remained in a reaction liquid, the content of finished components is low, and the difficulty is caused for purifying and preparing the polymethoxy dimethyl ether at low cost, so that people think of using formaldehyde with no water or low water content, and think of using trioxymethylene, paraformaldehyde, synthesizing anhydrous or low-moisture gaseous formaldehyde, or think of using a stronger formaldehyde aqueous solution to synthesize and remove water of a system in the synthesis process.

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, pipeline blockage is easy to occur, dangerous accidents occur and the like, and once strong acid substances are mixed into trioxymethylene in the storage and transportation processes, high polymer can be polymerized, and equipment is scrapped.

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 has the problems of difficult re-dehydration of synthetic liquid, low conversion rate, more residual formaldehyde, difficult separation and the like, immature process and difficult realization of industrialization.

In Chinese patents 201510128377.X and 201610147992.X, catalytic reaction is carried out on formaldehyde and methylal in the presence of a catalyst to prepare DMMn synthetic solution, and DMM3-8 is obtained after treatment and separation, but in the preparation method of the gaseous formaldehyde, monohydric alcohols such as isobutanol and the like are used as carrier auxiliary agents, so that the atom utilization rate is low; the auxiliary agent has low boiling point, is easy to enter synthetic liquid and finished products along with formaldehyde, has high price, is not beneficial to industrialization, and more importantly, after the auxiliary agent forms hemiacetal, the water solubility of the auxiliary agent is enhanced, like the patent description, the auxiliary agent is difficult to form a layer with water, or special separation equipment is needed, and during the subsequent distillation and dehydration processes, the reformed auxiliary additive can be evaporated and mixed into dilute formaldehyde solution due to the influence of balance.

In chinese patent 201610076437.2, it is mentioned that methanol or methylal is oxidized in an oxidation reactor by air to produce formaldehyde gas; the fact proves that the formaldehyde gas formed by oxidizing methanol contains about 30% of generated moisture, and is easy to form formaldehyde hydrate to liquefy or solidify by polymerization when the temperature is reduced to 20-99 ℃, which is not beneficial to realizing industrialization.

Other conventional methods for preparing anhydrous gaseous formaldehyde are: 1. the paraformaldehyde is heated and depolymerized to prepare gaseous formaldehyde, but the bound water of the paraformaldehyde is about 4%, so that the yield of DMMn synthesis and further recycling of intermediate products are greatly influenced, the preparation of the solid polyformaldehyde is complex, further feeding and conveying are not beneficial to large-scale and continuous large-scale production, and greater potential safety hazard exists. 2. Trioxymethylene is heated, decomposed and gasified under the action of an acid catalyst, so that trioxymethylene which cannot be decomposed in time is gasified with gaseous formaldehyde, a conveying pipeline is easy to be blocked, and the trioxymethylene is high in cost and not beneficial to realizing industrialization.

Disclosure of Invention

(1) The purpose of the invention is as follows: the invention aims to overcome the practical problems of the known preparation method of the gas formaldehyde and provide a new synthesis technical route and a new synthesis technical process of the gas formaldehyde and DMMn, wherein the whole process is operated in a liquid state or a gaseous state.

(2) The technical scheme is as follows: the invention relates to a method for preparing polymethoxy dimethyl ether (DMMn general n = 3-8), which comprises the steps of mixing formaldehyde aqueous solution and polyhydric alcohol according to a certain proportion, heating and dehydrating under vacuum condition, obtaining flowing polyformaldehyde containing lower water through the step, heating and gasifying the flowing polyformaldehyde containing lower water to obtain purer gaseous formaldehyde, mixing the obtained gaseous formaldehyde with methylal, applied low-boiling-point substances and macromolecules and the like under the existence of a catalyst, carrying out catalytic reaction at a certain temperature, filtering out the catalyst and purifying synthetic liquid after the reaction is balanced, respectively carrying out normal pressure and reduced pressure distillation, separating out the low-boiling-point substances, macromolecules and DMMn finished products, and carrying out reduced pressure rectification on the DMMn finished products to obtain single components. The residual polyol after the formaldehyde is gasified is returned and applied to the concentration of the formaldehyde in the next batch to prepare the flowing polyformaldehyde with lower water content. And the recovered low-boiling-point substances are returned to the system after a small amount of accumulated moisture is separated, so that the cyclic production of DMMn is realized.

The basic process is shown in the attached drawing (figure 1)

The main reaction formulae in which the flowing polyoxymethylene and gaseous formaldehyde are obtained are exemplified below:

(3) the technical effects are as follows: the preparation method of the polymethoxy dimethyl ether (DMM 3-8) has the advantages of easily obtained raw materials, liquid and gaseous state in the whole process, convenience for realizing continuity and automation, higher yield, higher product purity, 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 method adopts the polyhydric alcohol as the carrier adjuvant to prepare the hemiacetal etherate, and has the advantages of low cost, high efficiency, easy operation and no pollution to subsequent materials.

3. The invention solves the problem that the polyformaldehyde itself forms an insoluble and infusible solid state with low activity and difficult transportation when being dehydrated to an anhydrous state.

4. The continuous process of the invention is convenient for realizing automatic control.

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

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

7. 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 400g of formaldehyde aqueous solution (37%) and 60g of ethylene glycol, vacuumizing, heating to remove water to obtain 193.2g of anhydrous flowing polyformaldehyde, gradually heating the anhydrous flowing polyformaldehyde to 160 ℃, gradually gasifying the formaldehyde to obtain gaseous formaldehyde, introducing the dried anhydrous gaseous formaldehyde into a mixture containing 10g of catalyst and 280g of methylal, carrying out catalytic reaction at a certain temperature, filtering out the catalyst after the reaction reaches equilibrium to obtain 356.7g of reaction equilibrium liquid and 91.7g of residual ethylene glycol (loss of 24.8 g), respectively carrying out normal-pressure and reduced-pressure distillation on 356.7g of the reaction equilibrium liquid to separate 250.8g of low-boiling-point substances, 15.5g of macromolecules and 72.4g of DMMn finished products (loss of 18.0 g), and carrying out reduced-pressure rectification on the DMMn finished products to obtain single components. The residual ethylene glycol after the formaldehyde is gasified is returned and applied to the concentration of the formaldehyde in the next batch to prepare the anhydrous flowing polyformaldehyde.

Example 2: mixing 400g of formaldehyde aqueous solution (37%) with 91g of ethylene glycol recovered from the previous batch, vacuumizing, heating to remove water to obtain 222.5g of anhydrous flowing polyformaldehyde, gradually heating the anhydrous flowing polyformaldehyde to 160 ℃, gradually gasifying the formaldehyde to obtain gaseous formaldehyde, introducing the dried anhydrous gaseous formaldehyde into a mixture containing 10g of catalyst and 280g of methylal, carrying out catalytic reaction at a certain temperature, filtering out the catalyst after the reaction is balanced to obtain 384.7g of reaction equilibrium liquid and 93.5g of residual ethylene glycol (loss of 24.3 g), distilling 384.7g of the reaction equilibrium liquid under normal pressure and reduced pressure respectively to separate 264.0g of low-boiling-point substance, 22.9g of macromolecules and 77.3g of DMMn finished product (loss of 20.5 g), and carrying out reduced pressure rectification on the DMMn finished product to obtain single components. The residual ethylene glycol after the formaldehyde is gasified is returned and applied to the concentration of the formaldehyde in the next batch to prepare the anhydrous flowing polyformaldehyde.

Example 3: mixing 400g of formaldehyde aqueous solution (37%) with 93.5g of ethylene glycol recovered from the previous batch, vacuumizing, heating to remove water to obtain 226.7g of anhydrous flowing polyformaldehyde, gradually heating the anhydrous flowing polyformaldehyde to 160 ℃, gradually gasifying the formaldehyde to obtain gaseous formaldehyde, introducing the dried anhydrous gaseous formaldehyde into a mixture containing 10g of catalyst, 264.0g of recovered low-boiling-point substance and 22.9g of macromolecule supplemented with 196g of methylal, carrying out catalytic reaction at a certain temperature, filtering out the catalyst after the reaction reaches equilibrium to obtain 593.6g of reaction equilibrium liquid and 90.0g of residual ethylene glycol (loss of 26 g), respectively carrying out normal-pressure and reduced-pressure distillation on the reaction equilibrium liquid 593.6g to separate low-boiling-point substance 397.3g, macromolecule 35.5g and DMMn finished product 128.8g (loss of 32.0 g), and carrying out reduced-pressure rectification on the DMMn finished product to obtain single components. The residual ethylene glycol after the formaldehyde is gasified is returned and applied to the concentration of the formaldehyde in the next batch to prepare the anhydrous flowing polyformaldehyde.

Example 4: mixing 400g of formaldehyde aqueous solution (37%) and 60g of glycerol, vacuumizing, heating to remove water to obtain 191.1g of anhydrous flowing polyformaldehyde, gradually heating the anhydrous flowing polyformaldehyde to 160 ℃, gradually gasifying the formaldehyde to obtain gaseous formaldehyde, introducing the dried anhydrous gaseous formaldehyde into a mixture containing 10g of catalyst and 280g of methylal, carrying out catalytic reaction at a certain temperature, filtering out the catalyst after the reaction reaches equilibrium, obtaining 360.7g of reaction equilibrium liquid and 92.0g of residual glycerol (loss is 18.4 g), respectively carrying out normal-pressure and reduced-pressure distillation on 360.7g of the reaction equilibrium liquid, separating 246.8g of low-boiling-point substance, 17.2g of macromolecules and 74.4g of DMMn finished product (loss is 22.3 g), and carrying out reduced-pressure rectification on the DMMn finished product to obtain single components. The residual glycerol after the formaldehyde is gasified is returned and applied to the concentration of the formaldehyde in the next batch to prepare the anhydrous flowing polyformaldehyde.

Example 5: mixing 400g of formaldehyde aqueous solution (37 percent), 30g of diethylene glycol and 30g of trimethylolpropane, vacuumizing, heating to remove water to obtain 193.1g of anhydrous flowing polyformaldehyde, gradually heating the anhydrous flowing polyformaldehyde to 160 ℃, gradually gasifying the formaldehyde to obtain gaseous formaldehyde, introducing the dried anhydrous gaseous formaldehyde into a mixture containing 10g of catalyst and 280g of methylal, carrying out catalytic reaction at a certain temperature, filtering out the catalyst after the reaction reaches equilibrium, obtaining 357.7g of reaction equilibrium liquid, 94.5g (20.9 g of total loss) of residual diethylene glycol and trimethylolpropane mixture, respectively carrying out normal pressure and reduced pressure distillation on 357.7g of the reaction equilibrium liquid, separating 250.0g of low-boiling-point substances, 20.5g of macromolecules and 73.4g (13.8 g of loss) of DMMn finished products, and carrying out reduced pressure distillation on the DMMn finished products to obtain single components. And returning the mixture of the residual diglycol and the trimethylolpropane after the formaldehyde is gasified, and applying the mixture to the concentration of the formaldehyde in the next batch to prepare the anhydrous flowing polyformaldehyde.

Example 6: (comparative example) 400g formaldehyde aqueous solution (37%) is vacuumized and heated under the same conditions to remove moisture, 130.4g anhydrous non-flowable polyformaldehyde is obtained, the non-flowable polyformaldehyde is gradually heated to 160 ℃, formaldehyde is gradually gasified to obtain gaseous formaldehyde, the gaseous formaldehyde is introduced into a mixture containing 10g of catalyst and 280g of methylal, catalytic reaction is carried out at a certain temperature, after the reaction reaches equilibrium, the catalyst is filtered out, 387.8g of reaction equilibrium liquid is obtained, 0.6g of residual solid residue (total loss is 22 g), 387.8g of the reaction equilibrium liquid is subjected to normal pressure and reduced pressure distillation respectively, 295.9g of low-boiling-point substance, 15.2g of macromolecule and 50.4g of DMMn finished product (loss is 26.3 g) are separated, and DMMn finished product is subjected to reduced pressure rectification to obtain single components. However, the formaldehyde is solid after polymerization in the process, is difficult to convey and transfer, and can be intermittently prepared to have higher moisture content of 3.5 percent on a small test, so that the equilibrium conversion rate of the synthetic liquid is influenced, and the yield is lower.

Example 7: (comparative example) after mixing 400g of aqueous formaldehyde (37%) and 60g of isobutanol, the mixture was dissolved without delamination, and vacuum-pumping and heating were carried out to remove moisture, so as to obtain 161.5g of solid polyoxymethylene, which had a formaldehyde content of 79.8 and a moisture of 2.32%, a loss of 31.2g of isobutanol, and which was not suitable for transportation and other operations.