CN107011491B

CN107011491B - Method for preparing polymethyleneoxy dimethyl ether

Info

Publication number: CN107011491B
Application number: CN201710291202.XA
Authority: CN
Inventors: 刘建兵; 刘强; 曹蕾; 许望津; 苏自来; 李自明
Original assignee: Hunan Changxin New Material Science And Technology Development Co Ltd; Hunan Normal University
Current assignee: Hunan Changxin New Material Science And Technology Development Co Ltd; Hunan Normal University
Priority date: 2017-04-28
Filing date: 2017-04-28
Publication date: 2020-02-07
Anticipated expiration: 2037-04-28
Also published as: CN107011491A

Abstract

A process for preparing polymethyleneoxy dimethyl ether, the process comprising the steps of: 1) adding raw materials: adding formaldehyde, methylal and ion exchange resin into a reactor, and sealing; 2) reaction: stirring and heating; 3) and (3) post-treatment: cooling, adding ammonia or organic amine, and adjusting pH; 4) separating to obtain an organic layer which is polymethyleneoxy dimethyl ether. The purity of the polymethyleneoxy dimethyl ether obtained by the method can reach 99 percent; the conversion rate of formaldehyde can reach more than 95 percent, the product selectivity is higher than 50 percent, no waste water is generated in the whole process, and the like, and the method is particularly suitable for industrial production.

Description

Method for preparing polymethyleneoxy dimethyl ether

Technical Field

The invention relates to a preparation method of ethers, in particular to a preparation method of petroleum additive polymethyleneoxy dimethyl ether, belonging to the field of organic material preparation.

Background

With the development of human civilization, a good ecological environment is an important condition for sustainable development of the economic society and is also an important foundation for human survival and development. The problems of energy exhaustion and environmental pollution caused by petroleum fuel consumption are increasingly prominent, such as greenhouse effect, frequently-occurring haze weather, high PM in air and the like. Meanwhile, the demand and the dependence of human beings on energy are further enhanced, so that the development of new energy is an urgent subject in the development of human beings, and energy science and technology workers always want to find a substitute fuel which is rich in resources, low in price and environment-friendly. In particular, in recent years, the demand for diesel oil has been increasing in international society, and limited diesel oil resources have been decreasing, and the diesel oil supply has been insufficient and the price has been increasing. In addition, as the paraffin molecular weight of the diesel oil component is larger, the combustion performance is not good enough when the internal combustion engine works, and the combustion rate is not high enough, so that the oil consumption is increased, the pollution of exhaust gas to air is deepened, and the serious influence is generated on the ecological environment, the human health and the economic development. Further reducing the oil consumption and pollution of diesel vehicles becomes a problem to be solved urgently at present, and scientists in various countries around the world take a lot of trouble in the field and provide various solutions. In various schemes, the development of efficient and energy-saving diesel additives is considered to be a convenient and effective measure, and the fuel is fully combusted by changing the properties of the fuel under the conditions of not changing the structures of vehicles and engines and not increasing equipment, so that the energy conservation and the emission purification are realized.

The polymethyleneoxy dimethyl ether is a general name of a polyether substance, DMM for short_nOr PODE_n(n is 3-8), has higher oxygen content (42-48%) and cetane number (not less than 78), and is a novel diesel additive. Adding DMM into diesel oil_3-8(w_DMM3-810% -20%) can obviously reduce smoke intensity and discharge of nitrogen oxide in tail gas, improve combustion property of diesel oil, reduce solidifying point of diesel oil and raise heat efficiency of diesel engine, so that DMM can obviously reduce smoke intensity and discharge of nitrogen oxide in tail gas, and can raise diesel engine heat efficiency_3-8Is a novel environment-friendly diesel oil blending component which is internationally recognized and can reduce oil consumption and smoke emission, and the research on the synthesis process is a hot spot in the research in recent years.

Application of polymethyleneoxy dimethyl ether:

1. the cetane number of the diesel additive poly (methyleneoxy dimethyl ether) (PODME) is up to 76, the oxygen content is 47-50%, the diesel additive is produced by taking methanol as a raw material, no sulfur and aromatic hydrocarbon exist, 1O-20% is blended in the diesel, the condensation point of the diesel can be obviously reduced, the combustion characteristic of the diesel is improved, the thermal efficiency is improved, the smoke intensity can be reduced by 80% at most, the diesel additive has the advantages of a multifunctional compound additive, and the performance of the diesel can be comprehensively improved. The application range of the diesel oil is wide, the proportion of the diesel oil and the gasoline is basically maintained at about 2: 1 in recent years in places where a large amount of diesel oil is needed, such as agricultural machinery, mining machinery and the like, in the consumption of finished oil in China, only traffic diesel oil is added according to the proportion of 15%, the annual demand of PODE 3-5 is more than 3000 ten thousand tons at present.

2. The application research of alcohol, ether, ester and acetal diesel oil oxygen blending and blending components is carried out at home and abroad by the biodiesel additive. A large number of experiments and practices prove that the alcohol fuel has low solubility in diesel oil, has limiting factors such as corrosion and swelling action, has greatly different physical and chemical properties from diesel oil, an engine fuel supply system needs to be modified, and although methylal can be mutually dissolved with diesel oil, the methylal has low boiling point, does not change a fuel system and is difficult to directly apply. Some diesel oil cetane number improvers used at present also have the disadvantage that harmful substances such as sulfides, nitrides and the like are generated after combustion. Compared with dimethyl ether and methylal, the polymethyleneoxy dimethyl ether (PODME) has higher viscosity and boiling point, the cetane number is greater than 80, the physical property is similar to that of diesel oil, the polymethyleneoxy dimethyl ether (PODME) is good in intersolubility with the diesel oil, the polymethyleneoxy dimethyl ether (PODME) is blended into the diesel oil for use, an oil supply system of a vehicle engine is not required to be modified, the corrosion of alcohol fuel can be avoided, and the problems of. Those skilled in the art will appreciate that if the current gasoline blending component is said to represent Methyl Tertiary Butyl Ether (MTBE), then the future diesel blending component will represent PODME.

3. Paint auxiliary agent the paint auxiliary agent is an indispensable component of the paint, and can improve the production process, keep the storage stability, improve the construction condition, improve the product quality and endow special functions. According to the latest research report, polymethyleneoxy dimethyl ether (PODME) is a good paint auxiliary agent, and the polymethyleneoxy dimethyl ether (PODME) which is 0.1-1.0% is added into the paint production raw material as the auxiliary agent, so that the performance of the paint can be greatly improved.

4. Organic non-aromatic solvents traditional organic solvents are a large group of organic compounds widely used in life and production, which are present in paints, adhesives, lacquers and cleaners; the molecular weight is not large, and the product is liquid at normal temperature. The organic solvent includes various kinds of substances such as paraffin, olefin, alcohol, aldehyde, amine, ester, ether, ketone, aromatic hydrocarbon, hydrogenated hydrocarbon, terpene hydrocarbon, halogenated hydrocarbon, heterocyclic compound, nitrogen-containing compound, sulfur-containing compound, and the like, and most of them have low boiling points, are volatile, and have some toxicity to human body. The polymethyleneoxy dimethyl ether is an organic non-aromatic solvent, has high boiling point, is not easy to volatilize, has no toxicity, is a brand new environment-friendly solvent, and has wide application prospect.

In recent years, there have been many patent documents reporting polymethyleneoxydimethyl ether (DMM)_3-8) The method of (1). Such as ionic liquid processes, liquid acid catalytic processes, solid acid catalytic processes, and the like. These methods all have various disadvantages and are difficult to realize industrial production. At present, DMM_3-8The only method for realizing industrial production is to adopt strong acid ion exchange resin to catalyze the reaction of formaldehyde aqueous solution and methylal. Although the method is industrialized, the method has the defects of low formaldehyde conversion rate, poor product selectivity, large wastewater quantity and the like, the method for preparing the polymethyleneoxy dimethyl ether has an industrial problem through the post-treatment of reaction, and DMM (dimethyl methyl methacrylate)_3-8DMM which is difficult to separate from the reaction solution and is separated_3-8The purity is low, and other waste liquid has great pollution to the environment.

Disclosure of Invention

Aiming at the defects in the prior art, the invention adopts ion exchange resin as a catalyst and takes formaldehyde and methylal as raw materials to synthesize DMM_3-8And treating the solution after reaction by ammonia or organic amine. The purity of the polymethyleneoxy dimethyl ether obtained by the method can reach 99 percent; the conversion rate of formaldehyde can reach more than 95 percent, the product selectivity is higher than 50 percent, no waste water is generated in the whole process, and the like, and the method is particularly suitable for industrial production. When a strongly acidic ion exchange resin is used as a catalyst, difficulty is encountered in separating the product from unreacted starting materials, that is, a large amount of unreacted starting materials remains in the product. This technical problem has always plagued those skilled in the art.

According to a first embodiment of the present invention, there is provided a method for preparing polymethyleneoxy dimethyl ether.

A process for preparing polymethyleneoxy dimethyl ether, the process comprising the steps of:

1) adding raw materials: adding formaldehyde, methylal and ion exchange resin into a reactor, and sealing;

2) reaction: stirring and heating;

3) and (3) post-treatment: cooling, adding ammonia or organic amine, and adjusting pH;

4) separating to obtain an organic layer which is polymethyleneoxy dimethyl ether.

Preferably, the method further comprises:

5) and (3) purification: further purifying the polymethyleneoxy dimethyl ether obtained in the step 4) to obtain refined polymethyleneoxy dimethyl ether.

In the present invention, the formaldehyde in step 1) is polyoxymethylene, preferably one or more of trioxymethylene, paraformaldehyde (for example, having a degree of polymerization of 4 to 100, particularly 10 to 100), and paraformaldehyde (for example, having a degree of polymerization of not less than 101, for example, having a degree of polymerization of 101 to 300).

In the present invention, the formaldehyde starting material is solid formaldehyde (i.e., polyoxymethylene, such as trioxymethylene, paraformaldehyde, and/or paraformaldehyde as described above) and one or more of liquid formaldehyde and gaseous formaldehyde.

In the present invention, the ion exchange resin is an acidic ion exchange resin, more preferably a strongly acidic ion exchange resin, and preferably a strongly acidic cation exchange resin.

In the invention, the organic amine in the step 3) has the structure:

wherein: r¹＝R²＝H，R³＝CH₃(ii) a Or, R¹＝R²＝H，R³＝C₂H₅(ii) a Or, R¹＝R²＝CH₃，R³H; or, R¹＝R²＝C₂H₅，R³H; or, R¹＝R²＝R³＝CH₃(ii) a Or, R¹＝R²＝R³＝C₂H₅One or more of (a).

In the invention, the organic amine is one or more of an aqueous solution, a gas and a liquid corresponding to the substances.

In the present invention, the ammonia is liquid ammonia, gaseous ammonia or an aqueous solution of ammonia.

In the present invention, the mass ratio of formaldehyde to methylal in step 1) is 1:1 to 6, preferably 1:1.5 to 5, more preferably 1:2 to 4, and still more preferably 1:2.5 to 3.5.

In the present invention, the mass of the ion exchange resin is 1 to 500%, preferably 1.5 to 300%, more preferably 2 to 200%, more preferably 3 to 150%, preferably 3.2 to 30%, more preferably 3.5 to 15% of the total mass of formaldehyde and methylal.

In the present invention, when the ammonia or organic amine is an aqueous solution, the volume concentration of the ammonia or organic amine is 2 to 50%, preferably 3 to 45%, more preferably 4 to 40%, and still more preferably 5 to 30%.

In step 3) of the process of the invention, ammonia or an organic amine is added in such an amount that the pH of the solution in the reactor is adjusted to 6.5 to 9.5, more preferably 7 to 9, more preferably 7.5 to 8.5, for example around pH 8.

In the invention, the step 1) is specifically as follows:

a fixed bed type reactor or a high-pressure reaction kettle is used as a reactor, polyformaldehyde, methylal and strong-acid cation exchange resin are sequentially added into the reactor, the reactor is sealed, and nitrogen is introduced.

In the invention, the step 2) is specifically as follows:

starting a circulating pump, gradually heating to 60-120 ℃, reacting for 1-8 h under the pressure of 0.1-2.0 MPa; preferably, the temperature is gradually increased to 65-115 ℃, the pressure is 0.15-1.5 MPa, and the reaction lasts for 2-7 h; more preferably, the temperature is gradually increased to 70-110 ℃, the pressure is 0.2-1.0 MPa, and the reaction is carried out for 3-6 h.

In the present invention, the cooling to room temperature in step 3) is carried out. The cooling is natural cooling, or cooling by adopting condensed water, air or liquid nitrogen.

In the invention, the separation in the step 4) is filtration, suction filtration or liquid separation.

In the present invention, the purification in step 5) is distillation or rectification. Collecting the component with the distillation or rectification temperature higher than 108 deg.C as polymethyleneOxydimethyl ether DMM_3-8And (3) mixing.

In the present invention, the DMM is filtered_3-8Mixing, collecting solid as urotropin, and collecting liquid as refined DMM_3-8. The distilled or rectified front cut (collecting the components in the temperature range lower than 108 ℃) is used for the next reaction and is added into the reactor in the step 1). Introducing ammonia gas or liquid ammonia into the lower-layer aqueous solution until the pH value of the solution is more than 11, filtering to separate out urotropine, and using the residual solution for treating next reaction solution in the step 3).

In the present invention, the fraction before 108 ℃ is DMM₁And DMM₂The remainder being DMM_3-8And urotropine, i.e. DMM distilled off₂The DMM remains behind_3-8And urotropin, and filtering the solid urotropin to obtain the product.

In the invention, the specific operation of the rectification is as follows:

rectifying the dried polymethyleneoxy dimethyl ether by using a fractionating column, firstly slowly heating the dried polymethyleneoxy dimethyl ether to 60-70 ℃ in an oil bath, and distilling off methylal and formaldehyde low-boiling-point substances; then raising the temperature to 120-130 ℃, and distilling out the DMM₂Fraction, the DMM obtained by distillation₂Collecting the front fractions of methylal together to be recycled as raw materials; the residual part is polymethyleneoxy dimethyl ether.

In the invention, under the condition that acidic ion exchange resin is used as a catalyst, ammonia or organic amine is used as post-treatment to process the reaction liquid for preparing the polymethyleneoxy dimethyl ether, and the product and the unreacted raw materials are better separated through the actions of physics (hydrogen bond and molecular association) and chemistry, and the subsequent polymerization of the unreacted raw materials can be prevented, thereby blocking a material conveying pipeline. Post-treatment process of treatment reaction liquid and recycling of waste liquid: after the reaction liquid is treated by the reagent, liquid separation or suction filtration separation is carried out, and the waste liquid can be continuously added into the reagent for recycling. In addition, the organic amine or the inorganic ammonia is used for treating the unreacted formaldehyde, so that the problem that the pipeline is blocked by formaldehyde polymerization in the product distillation process is solved.

By adopting the method, the byproduct urotropin can be obtained, and the urotropin is hexamethylenetetramine or hexamethylenetetramine. The application of the urotropine is as follows: 1. hexamethylenetetramine is mainly used as a curing agent for resin and plastics, a catalyst and a foaming agent for aminoplasts, an accelerator (accelerator H) for rubber vulcanization, a shrink-proof agent for textiles and the like; 2. hexamethylenetetramine is a raw material for organic synthesis and is used for producing chloramphenicol in the pharmaceutical industry; 3. hexamethylenetetramine is used as a disinfectant for urinary systems, has no antibacterial effect and is effective against gram-negative bacteria. The 20% solution can be used for treating bromhidrosis, sweaty feet, tinea corporis, etc. It can be mixed with sodium hydroxide and sodium phenolate to be used as phosgene absorbent in gas masks; 4. is used for manufacturing pesticide. The hexamine and fuming nitric acid act to prepare cyclone explosive with strong explosiveness, which is called RDX for short; 5. the hexamethylenetetramine can also be used as a reagent for measuring bismuth, indium, manganese, cobalt, thorium, platinum, magnesium, lithium, copper, uranium, beryllium, tellurium, bromide, iodide and the like, a chromatographic analysis reagent and the like; 6. military fuels are commonly used.

In the present invention, one or more kinds of strong acidic exchange resins such as D001, D002, D006, DL08, DL10, and DL16 can be used as the ion exchange resin.

Preferably, the reaction in step 2) is carried out in a batch, semi-continuous or continuous manner.

When step 2) is carried out in a batch mode in a single reactor, the ion exchange resin is added in step 1), and the weight ratio of the total mass of formaldehyde and methylal to the ion exchange resin is 1: 0.001-0.4, preferably 1: 0.005-0.3, more preferably 1: 0.01 to 0.2, more preferably 1: 0.015-0.1. When step 2) is carried out in a continuous or semi-continuous manner, the ion exchange resin can be arranged in a reactor in a continuous or semi-continuous manner, such as a plurality of reactors in series, in the form of a fixed catalyst bed. In this case, the ion exchange resin is used in a larger amount. In an ion exchange resin bed layer, the weight ratio of the total mass of formaldehyde and methylal to the ion exchange resin is 1: 0.3 to 5, preferably 1: 0.5 to 3, more preferably 1: 0.8 to 2, more preferably 1: 1-1.5.

Reagents not described herein are those commonly used in the chemical arts, and process conditions or operations not described are those well known to those skilled in the art.

Compared with the prior art, the method has the following beneficial technical effects:

1. the invention adopts ammonia or organic amine to treat reaction liquid, adjusts the pH value to better separate the product from the unreacted raw materials, and obtains the DMM through the processes of separation, distillation or rectification and the like_3-8The purity of the product can reach more than 99%. And the subsequent polymerization of unreacted raw materials can be prevented, so that the material conveying pipeline is blocked.

2. According to the invention, the reaction solution is treated by ammonia or organic amine, so that the waste liquid can be recycled, the discharge of waste water is reduced, the cost is saved, and the pollution to the environment is reduced;

3. in the prior art, the polymethyleneoxy dimethyl ether is prepared, and when a product is purified by distillation or rectification, a large amount of white solids can be generated on the wall of a condensation pipe;

4. the conversion rate of polyformaldehyde can reach more than 95 percent by calculation of polyformaldehyde; product DMM_3-8The selectivity can reach 50 percent;

5. the process route of the invention adopts methylal which is one of the raw materials, has already realized industrialization, reduces the cost, and simultaneously obtains breakthrough in the aspect of environmental protection.

Drawings

FIG. 1 is a process flow diagram for preparing polymethyleneoxy dimethyl ether according to the present invention.

Detailed Description

Comparative example 1

Adopting a fixed bed reactor, sequentially adding 1250g of paraformaldehyde, 3500g of methylal and 200g of strong acid ion exchange resin into an 8L high-pressure reaction kettle, sealing, introducing nitrogen, starting a circulating pump, gradually heating (controlled by a reaction kettle controller) to 90 ℃, and reacting for 4 hours under the pressure of 0.4 MPa. After the reaction, the reaction mixture was cooled to room temperature. Separating to obtain organic layer and gasThe content of the phase chromatogram is as follows: methyl ether 0.43%, MeOH 4.78%, methyl formate 0.89%, DMM 48.39%, CH₂O 0.61％，DMM₂26.41％，DMM₃12.05％，DMM₄4.42％，DMM₅1.35％，DMM₆0.52％，DMM₇0.11％，DMM₈The conversion of 0.04% paraformaldehyde was 94.8%, with a selectivity of 57.6%. Distilling the organic layer to obtain DMM_3-8903 g.

In this comparative example, the separation and purification of the product was poor and the purity of the product was low. Particularly, the blockage phenomenon of a product conveying pipeline is serious, and the pipeline blockage phenomenon is serious after the operation for only 4 days.

Example 1

Adopting a fixed bed reactor, sequentially adding 1250g of paraformaldehyde, 3500g of methylal and 200g of strong acid ion exchange resin into an 8L high-pressure reaction kettle, sealing, introducing nitrogen, starting a circulating pump, gradually heating (controlled by a reaction kettle controller) to 90 ℃, and reacting for 4 hours under the pressure of 0.4 MPa. After the reaction, the reaction mixture was cooled to room temperature. Adding aqueous solution of triethylamine with volume fraction of 5% to adjust the pH value of the solution to 8, separating the solution to obtain an organic layer, wherein the content of the gas chromatography is as follows: methyl ether 0.53%, MeOH 4.88%, methyl formate 1.17%, DMM 48.35%, CH₂O 0.57％，DMM₂26.49％，DMM₃11.35％，DMM₄4.50％，DMM₅1.55％，DMM₆0.44％，DMM₇0.12％,DMM₈0.05 percent. The conversion of paraformaldehyde was 95% with a selectivity of 58%. Distilling the organic layer to obtain DMM_3-8913 g; DMM_3-8The purity of (2) was 99.2%.

Example 2

Adopting a fixed bed reactor, sequentially adding 1250g of paraformaldehyde, 3500g of methylal and 200g of strong acid ion exchange resin into an 8L high-pressure reaction kettle, sealing, introducing nitrogen, starting a circulating pump, gradually heating (controlled by a reaction kettle controller) to 90 ℃, and reacting for 4 hours under the pressure of 0.4 MPa. After the reaction, the reaction mixture was cooled to room temperature. Adding an aqueous solution of ethylenediamine with the volume fraction of 15% to adjust the pH of the solution to 8, and separating the solution to obtain an organic layer, wherein the content of the gas chromatography is as follows: methyl ether 1.22%, MeOH 4.63%, A2.16% of methyl formate, DMM 48.27%, CH₂O 0.75％，DMM₂26.86％，DMM₃10.40％，DMM₄3.87％，DMM₅1.30％，DMM₆0.38％，DMM₇0.13％，DMM₈0.03 percent. The conversion of paraformaldehyde was 96% with a selectivity of 58%. Distilling the organic layer to obtain DMM_3-8914 g; DMM_3-8The purity of (2) was 99.1%.

Example 3

Adopting a fixed bed reactor, sequentially adding 1250g of paraformaldehyde, 3500g of methylal and 200g of strong acid ion exchange resin into an 8L high-pressure reaction kettle, sealing, introducing nitrogen, starting a circulating pump, gradually heating (controlled by a reaction kettle controller) to 90 ℃, and reacting for 4 hours under the pressure of 0.4 MPa. After the reaction, the reaction mixture was cooled to room temperature. Adding an ammonia water solution with the volume fraction of 25% to adjust the pH value of the solution to 8, separating the solution to obtain an organic layer, wherein the content of the gas chromatography is as follows: methyl ether 1.05%, MeOH 4.84%, methyl formate 1.85%, DMM 47.59%, CH₂O 0.49％，DMM₂26.87％，DMM₃10.95％，DMM₄4.3％，DMM₅1.53％，DMM₆0.37％，DMM₇0.12％，DMM₈0.04 percent. The conversion of paraformaldehyde was 95% with a selectivity of 54%. Distilling the organic layer to obtain DMM_3-8898 g, and 52 g of urotropin, wherein the front cut fraction can be directly used for the next reaction. Introducing ammonia (or liquid ammonia) into the lower aqueous solution until the pH value is 12, filtering and separating out 11 g of urotropine, wherein the aqueous solution is used for treating next reaction liquid; DMM_3-8The purity of (2) was 99.2%.

Example 4

Adopting a fixed bed reactor, sequentially adding 1250g of paraformaldehyde, 3500g of methylal and 200g of strong acid ion exchange resin into an 8L high-pressure reaction kettle, sealing, introducing nitrogen, starting a circulating pump, gradually heating (controlled by a reaction kettle controller) to 90 ℃, and reacting for 4 hours under the pressure of 0.4 MPa. After the reaction, the reaction mixture was cooled to room temperature. Adding 300g of water, adjusting the pH value of the solution to 8 by introducing liquid ammonia, and separating the solution to obtain an organic layer, wherein the content of a gas chromatography is as follows: methyl ether 0.63%, MeOH 4.54%, methyl formate 1.51%, DMM 48.76%, CH₂O 1.00％，DMM₂27.39％，DMM₃10.08％，DMM₄4.23％，DMM₅1.37％，DMM₆0.39％，DMM₇0.10 percent. The conversion of paraformaldehyde was 97% with a selectivity of 57%. Distilling the organic layer to obtain DMM_3-8950 g of urotropin and 58 g of urotropin, and the front cut fraction can be directly used for the next reaction. Introducing ammonia (or liquid ammonia) into the lower aqueous solution until the pH value is 12, filtering and separating out 11 g of urotropine, wherein the aqueous solution is used for treating next reaction liquid; DMM_3-8The purity of (2) was 99.5%.

Example 5

Example 3 was repeated except that 1250g of solid trioxymethylene, 2500g of methylal and 150g of strongly acidic ion exchange resin were charged in the autoclave. The conversion of paraformaldehyde was 95% with a selectivity of 54%. Distilling the organic layer to obtain DMM_3-8936 grams; DMM_3-8The purity of (2) was 99.3%.

Example 6

Example 3 was repeated except that 35% by volume of an aqueous solution of ethylamine was added to adjust the pH of the solution to 10. The conversion of paraformaldehyde was 95% with a selectivity of 54%. Distilling the organic layer to obtain DMM_3-8915 g; DMM_3-8The purity of (2) was 99.6%.

Example 7

Example 4 was repeated, except that the temperature was gradually raised to 70 ℃ and the pressure was 1.0MPa, and the reaction was carried out for 2 hours. The conversion of paraformaldehyde was 97% with a selectivity of 57%. Distilling the organic layer to obtain DMM_3-8949 g; DMM_3-8The purity of (2) was 98.3%.

Claims

1. A process for preparing polymethyleneoxy dimethyl ether, the process comprising the steps of:

1) adding raw materials: adding a formaldehyde raw material, methylal and ion exchange resin into a reactor, and sealing;

2) reaction: stirring and heating;

3) and (3) post-treatment: cooling to room temperature, adding ammonia or organic amine, and adjusting pH;

4) separating, wherein the obtained organic layer is polymethyleneoxy dimethyl ether;

wherein: the ion exchange resin is acidic ion exchange resin;

the organic amine has the structure:

wherein: r¹＝R²＝H，R³＝CH₃(ii) a Or, R¹＝R²＝H，R³＝C₂H₅(ii) a Or, R¹＝R²＝CH₃，R³H; or, R¹＝R²＝C₂H₅，R³H; or, R¹＝R²＝R³＝CH₃(ii) a Or, R¹＝R²＝R³＝C₂H₅One or more of; the ammonia is liquid ammonia.

2. The method of claim 1, wherein: the method further comprises the following steps:

3. The method according to claim 1 or 2, characterized in that: the formaldehyde raw material in the step 1) is paraformaldehyde; and/or

The ion exchange resin is a strong acid ion exchange resin.

4. The method of claim 3, wherein: the formaldehyde raw material in the step 1) is trioxymethylene; and/or

The ion exchange resin is a strong acid cation exchange resin.

5. The method according to claim 1 or 2, characterized in that: the formaldehyde raw material in the step 1) is one or more of a solid formaldehyde raw material, a liquid formaldehyde raw material and a gas formaldehyde raw material.

6. The method according to any one of claims 1-2, 4, wherein: adjusting the pH value to 6.5-9.5 in the step 3).

7. The method of claim 6, wherein: adjusting the pH value to 7-9 in the step 3).

8. The method of claim 7, wherein: adjusting the pH value to 7.5-8.5 in the step 3).

9. The method of any one of claims 1-2, 4, 7-8, wherein: in the step 1), the mass ratio of the formaldehyde raw material to the methylal is 1: 1-6; and/or

The mass of the ion exchange resin is 1-500% of the total mass of the formaldehyde raw material and the methylal.

10. The method of claim 3, wherein: in the step 1), the mass ratio of the formaldehyde raw material to the methylal is 1: 1-6; and/or

11. The method of claim 5, wherein: in the step 1), the mass ratio of the formaldehyde raw material to the methylal is 1: 1-6; and/or

12. The method of claim 9, wherein: in the step 1), the mass ratio of the formaldehyde raw material to the methylal is 1: 1.5-5; and/or

The mass of the ion exchange resin is 1.5-300% of the total mass of the formaldehyde raw material and the methylal.

13. The method according to claim 10 or 11, characterized in that: in the step 1), the mass ratio of the formaldehyde raw material to the methylal is 1: 1.5-5; and/or

14. The method of claim 12, wherein: in the step 1), the mass ratio of the formaldehyde raw material to the methylal is 1: 2-4; and/or

The mass of the ion exchange resin is 2-200% of the total mass of the formaldehyde raw material and the methylal.

15. The method of claim 13, wherein: in the step 1), the mass ratio of the formaldehyde raw material to the methylal is 1: 2-4; and/or

16. The method of any one of claims 1-2, 4, 7-8, 10-12, 14-15, wherein: when the organic amine is an aqueous solution, the volume concentration of the organic amine is 2-50%.

17. The method of claim 16, wherein: the volume concentration of the organic amine is 3-45%.

18. The method of claim 17, wherein: the volume concentration of the organic amine is 4-40%.

19. The method of any one of claims 1-2, 4, 7-8, 10-12, 14-15, 17-18, wherein: the step 1) is specifically as follows:

a fixed bed type reactor or a high-pressure reaction kettle is used as a reactor, a formaldehyde raw material, methylal and strong-acid cation exchange resin are sequentially added into the reactor, the reactor is sealed, and nitrogen is introduced; and/or

The step 2) is specifically as follows:

starting a circulating pump, gradually heating to 60-120 ℃, reacting for 1-8 hours under the pressure of 0.1-2.0 MPa.

20. The method of claim 19, wherein: the step 2) is specifically as follows: starting a circulating pump, reacting for 2-7 h at 65-115 ℃ and 0.15-1.5 MPa.

21. The method of claim 20, wherein: the step 2) is specifically as follows: starting a circulating pump, gradually heating to 70-110 ℃, reacting for 3-6 h under the pressure of 0.2-1.0 MPa.

22. The method of claim 2, wherein: the purification in the step 5) is distillation or rectification; collecting DMM (polymethyleneoxy dimethyl ether) as the component with the distillation or rectification temperature higher than 108 DEG C_3-8And (3) mixing.

23. The method of claim 22, wherein: filtering the DMM_3-8Mixing, collecting solid as urotropin, and collecting liquid as refined DMM_3-8(ii) a The distilled or rectified front fraction is used for the next reaction and is added into the reactor in the step 1); introducing ammonia gas or liquid ammonia into the lower-layer aqueous solution until the pH value of the solution is more than 11, filtering to separate out urotropine, and using the residual solution for treating next reaction solution in the step 3).