CN103333061A - Method for refining and purifying polyformaldehyde dialkyl ether - Google Patents

Abstract

The present invention finds out the reasons for the poor extraction rate of the extraction unit and the poor purity of the extraction product through in-depth research on the extraction unit process of polyoxymethylene dialkyl ether in the prior art, and further provides a method that can significantly improve the extraction rate and product purity. Purity refining extraction process, by adding an appropriate amount of sulfite to the equilibrium product of polyoxymethylene dialkyl ether to achieve the purpose of removing formaldehyde in the equilibrium system of polyoxymethylene dialkyl ether, the refining and purification of polyoxymethylene dialkyl ether The method belongs to the solid phase reaction, the generated α-hydroxysulfonate is insoluble in the product, the impurities are easy to separate after the reaction, and the process is simple; the method of adding sulfite in stages is beneficial to break the adsorption between sulfite and formaldehyde balance, so that the reaction proceeds in the positive direction, and fully reacts to remove methanol; since sulfite is input in a solid phase, there is no problem of methanol and other materials dissolving in aqueous solution, so the recovery rate of the product is high; these can effectively reduce production costs .

Description

A method for refining and purifying polyoxymethylene dialkyl ether

technical field

The invention belongs to the fields of coal-based energy chemical industry, clean energy and chemical process refining. It specifically relates to a refining and extraction process of polyoxymethylene dialkyl ether, a diesel additive.

Background technique

Surveys in recent years have shown that the apparent consumption of diesel in my country has reached about 167 million tons, resulting in frequent shortages of diesel supply (the domestic demand ratio of diesel and gasoline is about 2.5:1, while the current output ratio is about 2.3:1) . In addition to institutional reasons such as unreasonable pricing of different types of oil products and slow linkage between domestic refined oil prices and international crude oil prices, the fundamental reason is the constraints of resource shortages. Traditionally, oil is used as raw material for diesel production. China's relatively "rich in coal, poor in oil, and low in gas" resource endowment has made the contradiction between its sustained and rapid economic and social development and oil supply increasingly prominent. Since becoming a net importer of oil in 1993, the import volume has continued to grow rapidly. After 2011, the dependence on foreign countries has exceeded 56%, which seriously affects the country's energy strategic security.

In addition, due to the deteriorating quality of crude oil, the scale of catalytic processing of heavy oil in my country continues to expand, and the proportion of catalytic diesel continues to increase, resulting in a gradual decline in the cetane number (CN value) of finished diesel oil, and a significant increase in harmful substances emitted by combustion. The CN value of diesel oil is an urgent problem to be solved.

In addition to CO, CO ₂ and _NOx , the exhaust emitted by diesel engines also contains a large number of unburned HC compounds and particulate matter PM and other harmful substances, which is one of the main sources of PM2.5 pollution in urban air. In June 2012, the International Cancer Research Center (IARC) under the World Health Organization (WHO) announced that it decided to increase the carcinogenic hazard level of diesel engine exhaust from the "possibly carcinogenic" category classified in 1988 to the "confirmed carcinogenic" category. . With the advancement of scientific research, there is now enough evidence to prove that diesel engine exhaust is a cause of lung cancer in people. In addition, there is limited evidence linking diesel engine exhaust inhalation to bladder cancer. People are exposed to diesel engine exhaust through various channels in daily life and work. IARC hopes the reclassification will serve as a guide for governments and other policymakers to push for stricter emission standards for diesel engines. This important decision undoubtedly put forward more stringent requirements on the quality of diesel.

Reducing the content of harmful components such as sulfur, nitrogen, and aromatics in fuels through hydrofining and other petroleum refining processes is an effective technical route to improve fuel quality, but the requirements for hydrogenation catalysts and reaction processes are high, and the processing costs are relatively high. Many scientific research institutions in the world are developing gasoline and diesel oxygen-containing blending components, especially the research and development of production technology for high-oxygen and high-cetane diesel blending components. This has become a research field in the field of new energy technology in recent years. hotspot.

After research, in view of the characteristics of oxygen-containing fuel itself, if carbonyl, methanol and other oxygen-containing substances with high cetane number are added to the fuel as fuel additives, effective engine parameters can be achieved without changing the original parameters of the engine. Reduce HC, CO emissions, especially soot emissions, while not causing an increase in NO _x emissions.

Nowadays, many studies have shown that polyoxymethylene dimethyl ether (also known as polyoxymethylene formal, English abbreviation DMM _n , n=2~8), its general formula is CH ₃ (OCH ₂ ) _n OCH ₃ , a A yellow liquid with a high boiling point, the average cetane number is above 63, and it increases greatly with the increase of the degree of polymerization, the average oxygen content is 47% to 50%, the flash point is about 65.5°C, and the boiling point is about 160 ~280℃, it is a clean, high cetane number diesel blending component, and it is also recognized as an environmentally friendly fuel component in the world. It can be blended with diesel oil without any modification to the engine fuel supply system of the vehicle in use, which can significantly improve the performance of diesel oil. However, in actual use, it will be found that the cetane number of polyoxymethylene dimethyl ether is greatly affected by its own degree of polymerization, and a higher degree of polymerization of polyoxymethylene dimethyl ether is required to have a better effect. However, in view of the difficulty of the polymerization reaction itself, both the equipment and the process conditions have higher requirements, which also increases the difficulty of its processing and extraction. Therefore, people gradually focus on the performance of polyoxymethylene dialkyl ether. Polyoxymethylene dialkyl ether (ATPOM _n ) is a low relative molecular weight acetal polymer with methyleneoxy as the main chain and capped with a lower carbon alkyl group. The general formula is mostly R(OCH ₂ ) _n OR, where R is Alkyl chain of C _n H _2n+1 . Since the molecular weight of the end group of polyoxymethylene dialkyl ether is slightly larger, it only needs a slightly lower degree of polymerization to achieve the performance of cetane number similar to that of polyoxymethylene dialkyl ether, and the difficulty in the preparation process Also correspondingly smaller. Polymethoxyl dialkyl ether has good environmental protection performance. It can be blended into diesel oil in a certain proportion to increase the oxygen content of oil, and greatly reduce SO _x , unburned HC compounds, PM particulate matter black smoke and CO in automobile exhaust. Pollutant emissions, and because polyoxymethylene dialkyl ether has a high cetane number and similar physical properties to diesel, it is also a diesel fuel additive with high application value.

The synthesis of polyoxymethylene dialkyl ether (including polyoxymethylene dimethyl ether) can be achieved through a series of steps such as methanol, formaldehyde, methylal, polyoxymethylene and dimethyl ether through synthesis gas. China is a well-known country with large coal reserves, and China's coal-to-methanol, natural gas-to-methanol, and coke-oven gas-to-methanol technologies are becoming more and more mature. In 2012, methanol production capacity has exceeded 50 million tons, but the operating rate of the plant is only about 50%. The problem of excess methanol It is already very prominent, and there is an urgent need to further extend the coal chemical industry chain. Therefore, the development of the technology of preparing polyoxymethylene dialkyl ether with coal-based methanol can not only provide a new technology for significantly improving the quality of finished diesel, but also improve the raw material structure of finished diesel production, making it more suitable for my country's fossil energy resources endowment to promote the strategic security of our country's engine liquid fuel supply.

The process for preparing polymethoxydialkyl ethers should include three main process units, one is a synthesis unit, which is a step polymerization reaction and a thermodynamic equilibrium reaction under the catalysis of an acidic catalyst; the other is a pretreatment unit, mainly in the and deacidification, drying and dehydration and other treatment steps; the third is the rectification separation unit of downstream products, trying to separate polymethoxydialkyl ether.

At present, domestic and foreign research on the preparation process of polyoxymethylene dialkyl ether (including polyoxymethylene dimethyl ether) is mainly focused on the selection of raw materials and condition optimization of the synthesis unit and the optimization of the catalyst system, and how to improve the yield of the target product. Distributing, improving the process technology of product yield. As far as the optimization of synthetic raw materials is concerned, there are mainly the following five processes: one is the process of synthesizing polyoxymethylene dimethyl ether with methanol, formaldehyde or formaldehyde aqueous solution or paraformaldehyde as raw materials. For details, see patent documents US6437195B2 and US2008/0207954A1 And EP1070755A1; the second is to synthesize polyoxymethylene dimethyl ether with formalin, paraformaldehyde or paraformaldehyde as raw materials, and the main process is detailed in patent documents US2007/0260094A1 and US2449469A; the third is to synthesize with methanol and dimethyl ether as raw materials Polyoxymethylene dimethyl ether, see patent document US6265528B1; the fourth is developed on the basis of the first three methods, using the alcohol-containing by-products of other processes in the prior art as raw materials to synthesize multiple degrees of polymerization and multiple end groups The mixed system of polyoxymethylene dialkyl ether is mainly represented by Chinese patents CN102173984A and CN102180778A, which use industrial brewing alcohol by-products or Fischer-Tropsch synthesis by-products as raw materials or use petroleum C ₄ , C ₅ as raw materials to synthesize a variety of polymers The process of polyoxymethylene dialkyl ether with high degree and various terminal groups.

In the above-mentioned scheme of research on the synthesis of polyoxymethylene dialkyl ether, the separation and extraction of the synthetic products are all carried out by conventional ordinary rectification, azeotropic rectification or extractive rectification in the prior art. The extraction unit has not been studied in more depth. However, in actual research, it is found that when the target product is extracted by the above-mentioned conventional seemingly feasible means, the extraction rate of the product is not high, and the purity of the proposed product is not ideal, and additional subsequent purification operations are required to meet the demand. , and no matter how the parameters and conditions of the entire extraction unit operation process are optimized, it is still impossible to break through the problem of extraction rate, and it is impossible to obtain a substantial improvement in extraction rate and product purification. However, in actual production, due to economic and many other considerations, no matter how amazing the efficiency of the previous synthesis unit is, the inability to obtain products that meet the needs through effective means has always become a difficult problem and bottleneck that inhibits the development of this process, and has also become a problem in this field. An urgent matter that needs to be addressed.

Contents of the invention

For this reason, the technical problem to be solved by the present invention is to find out the influence reasons of the extraction rate of the extraction unit and the poor purity of the extraction product through in-depth research on the extraction unit process of polyoxymethylene dialkyl ether in the prior art, and then provide A refined extraction process that can significantly improve the extraction rate and product purity to solve the problem of poor extraction efficiency.

In order to solve the above technical problems, the invention provides a method for refining and purifying polyoxymethylene dialkyl ether, comprising the steps of:

S1. Putting sulfite into the equilibrium product after the reaction of preparing polyoxymethylene dialkyl ether, and performing reflux condensation treatment;

S2, performing solid-liquid separation on the mixture obtained in step S1, and collecting liquid phase products;

S3. Purifying and refining the collected liquid phase product.

The sulfite is one or a combination of sodium sulfite, sodium bisulfite and sodium metabisulfite.

The added mass of the sulfite is 1%-30% of the mass of the equilibrium product.

The added mass of the sulfite is 5%-15% of the mass of the equilibrium product.

In the step S1, the control temperature of the reflux condensation treatment is 10-60°C.

The temperature is 25-50°C.

In the step S1, the step of adding the sulfite is carried out in one or multiple additions.

In the step S1, the processing time of the reflux condensation step is 0.5-2.5 hours.

The treatment time is 1-2h.

The purification step in step S3 is a combination of one or more of atmospheric distillation, vacuum distillation, flash distillation, rectification, phase separation, and filtration.

The purification step in step S3 includes, but is not limited to, one or more combinations of atmospheric distillation, vacuum distillation, flash distillation, and rectification.

In the step S3, the fraction before 40-110°C collected by atmospheric distillation is raw material methanol, methylal and a small amount of dimerization products, and the resulting fractions are dimerization and higher degree of polymerization products.

In the step S3, the vacuum degree of the vacuum distillation is 0-0.1 MPa, and the products with different polymerization degrees can be obtained by distillation by changing the vacuum degree during the distillation operation.

In the step S3, the pressure of the flash operation is 0.01-0.5 MPa, and the crude product can be roughly separated by changing the pressure, reducing the subsequent separation load.

In the step S3, the bottom temperature of the rectification operation is 100-200° C., and the reflux ratio is 1-5. More precisely, the temperature at the bottom of the tower is 100-150° C., and the reflux ratio is 1-2.

In the step S3, various operations may be combined according to the separation purpose. Flash distillation can roughly separate the products that need to be separated, and reduce the subsequent distillation operation load; atmospheric distillation can separate methanol, methylal and products with a polymerization degree of 2-5; vacuum distillation can obtain products with a polymerization degree of 5-8 Product with high degree of polymerization; rectification operation can obtain single component with higher purity.

The method described in the present invention is applicable to all processes for preparing polyoxymethylene dialkyl ether (including polyoxymethylene dimethyl ether) using formaldehyde substances (including formaldehyde, paraformaldehyde, methylal, etc.) as raw materials, and is especially suitable for The process for preparing polyoxymethylene dialkyl ether involved in Chinese patents CN102173984A and CN102180778A.

Compared with the above technical solution of the present invention, the prior art has the following advantages:

1. Through in-depth research on the synthesis process of polyoxymethylene dialkyl ether, the applicant found that whether formaldehyde, paraformaldehyde or methylal is used as the reaction raw material, since the entire reaction system is a balanced and reversible reaction, there are low Carbon alcohol (or methanol) cannot be completely reacted, so no matter how the reaction conditions are improved, there will be about 3.5%wt of formaldehyde in the product system that cannot be completely reacted (or monomers depolymerized by paraformaldehyde and methylal) , and the reason why the polyoxymethylene product is difficult to extract and the product purity is not high is mainly because the formaldehyde in the system has an unexpected negative impact, and the complexation between formaldehyde and polyoxymethylene dialkyl ethers of various degrees of polymerization reaction, formaldehyde connects the polymerization products like a chain to form a huge complex system, which makes the whole product system unable to refine and purify the product through conventional distillation and other processes, which not only brings great difficulties to the separation and treatment of the product At the same time, it seriously affects the yield and economy of the product; therefore, before extracting the target product, it is necessary to remove a small amount of formaldehyde contained in the equilibrium system in a targeted manner, in order to release the required products, and to be able to use other feasible means Obtain products that meet the needs;

2. The applicant was also pleasantly surprised to find that the water content in the equilibrium system after the synthesis of the product has a great impact on the extraction efficiency and purity of the product while conducting research on the reasons that affect the extraction efficiency. Therefore, when choosing to remove formaldehyde In the refining process, it is necessary to select a reasonable method to maximize the extraction efficiency and purity of the product;

3. In the extraction process described in the present invention, through careful research by the applicant, the creative discovery affects the important factors that affect the extraction efficiency of polyoxymethylene dialkyl ether in the prior art, and through targeted analysis of the above-mentioned factors that have not caused any technical problems in the art The improvement of the factors that personnel care and think about has realized the efficient and high-purity extraction of polyoxymethylene dialkyl ether products with various degrees of polymerization;

4. The method for refining and purifying polyoxymethylene dialkyl ether provided by the present invention is to achieve the purpose of removing formaldehyde in the equilibrium system by adding sulfite in the equilibrium product of polyoxymethylene dialkyl ether. The reaction formula is as follows:

HCHO+HSO ₃ ^- =HO-CH ₂ -SO ₃ ^-

2HCHO+SO ₃ 2 ^- +H ₂ O=HO-CH ₂ -SO ₃ ^- +OH ^-

2HCHO+S ₂ O ₅ 2 ^- +H ₂ O=2HO-CH ₂ -SO ₃ ^- ;

This reaction is a solid-phase reaction, the generated α-hydroxysulfonate is insoluble in the product, the impurities are easy to separate after the reaction, the process is simple, and the conventional extraction can be directly realized without additional drying steps; Input, there is no problem of methanol and other materials dissolving in aqueous solution, so the recovery rate of materials is high; these can effectively reduce production costs;

5. By adding sulfite in stages, it is beneficial to break the adsorption balance between sulfite and formaldehyde, so that the reaction proceeds in the positive direction, and the formaldehyde can be fully reacted to remove;

6. The α-hydroxysulfonate produced in the method for refining and purifying polyoxymethylene dialkyl ether provided by the present invention is insoluble in the product, and can be filtered out together with unreacted sulfite and can be used as a chemical raw material for producing water scale inhibitors ;

7. The refining method of the present invention uses solid-phase sulfite for refining. Compared with the water-containing refining method, the product with a low degree of polymerization has a significant leap-forward improvement, and unexpected technical effects have been achieved;

8. The method for refining and purifying polyoxymethylene dialkyl ether provided by the present invention has mild reaction conditions and high operational safety.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the implementation manners of the present invention will be further described in detail below.

The weight percentage and product purity of each component described in each following embodiment and comparative example are calculated by following formula:

Extraction percentage of components (wt%) = mass of separated components/sum of mass of separated components × 100%;

Product purity (wt%) = isolated PODE _n≥2 weight and/sum of mass of isolated components × 100%.

The equilibrium products of polyoxymethylene dialkyl ethers used in the following Examples 1-5 and Comparative Example 1 were all prepared by the following method: in a batch-type high-pressure reactor, petroleum C ₅ , formaldehyde were sequentially added in a molar ratio of 2:4 Industrial formaldehyde with a content of 37%, water contained in industrial formaldehyde can be used as an initiator to participate in the reaction, and p-toluenesulfonic acid, which accounts for 2% of the total weight of the reactants, is selected as a catalyst and put into the reaction kettle together, and filled into the nitrogen replacement reaction kettle control the initial pressure in the reactor to 0.2Mpa, and keep a constant temperature of 70-90°C under stirring at 100rpm for 10 hours until the components are balanced to obtain a balanced product of polyoxymethylene dialkyl ether. The polyoxymethylene dialkyl ether The content of formaldehyde in the ether equilibrium product is 3.1wt%.

As an alternative embodiment of the present invention, the polyoxymethylene dialkyl ether equilibrium products produced with aldehydes as raw materials can be purified using the process for purifying polyoxymethylene dialkyl ether with sulfite described in the present invention.

Example 1

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium sulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium sulfite is 10% of the mass of the equilibrium product, heat to 40°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, and distill out the fraction before 60°C. The initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is divided into two Polymerization product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Example 2

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 40°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. The liquid phase product is rectified at atmospheric pressure, the temperature at the bottom of the tower is 100° C., and the reflux ratio is 1. The production liquid at the top of the tower consists of methanol, methylal and a small amount of dimerization products; Then carry out fractional atmospheric pressure distillation on the polymer products with a degree of polymerization of 2-8, the fraction collected at ~110°C is the dimerization product (PODE ₂ ), and the fraction collected at ~160°C is the trimerization product (PODE ₃ ), The fraction collected at ~200°C is tetrameric product (PODE ₄ ); the fraction collected at ~250°C is pentameric product (PODE ₅ ); the fraction collected at ~280°C is hexamerized product (PODE ₆ ); the fraction collected at ~320°C is The fraction is the heptamer product (PODE ₇ ); the fraction collected at ~350°C is the octamer product (PODE ₈ ).

Example 3

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium metabisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium metabisulfite is 10% of the mass of the equilibrium product, heat to 40°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, distill out the fraction before 60°C, the initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is dimerization Product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Comparative example 1

The extraction process described in this comparative example omits the above-mentioned refining steps (i.e. steps S1 and S2), and directly enters the synthesized balanced system as a whole into the extraction unit (i.e. step S3), and uses the same extraction method as in Example 1 above. Extraction of products of each degree of polymerization.

The distribution of each product obtained in the above-mentioned Examples 1-3 and Comparative Example 1 is shown in the table below.

From the test results in the above table, it can be seen that the purity of the product (PDOE _n ) is greatly improved after sulfite treatment, which shows that sulfite can effectively remove formaldehyde in the equilibrium product of polyoxymethylene dialkyl ether, and destroy the balance The product azeotropic system improves the purity of the separated product, and the steps are simple and easy to operate; among them, the purification effect of sodium bisulfite is the best, and the purification effect of sodium sulfite and sodium metabisulfite is relatively close.

The following examples 4-9 and comparative example 2 adopt the method disclosed in Example 1 in the Chinese patent document CN101898943A (application number 201010191075.4) "A Method for Synthesizing Polyoxymethylene Dimethyl Ether" to prepare a Equilibrium system of methyl ether product.

Example 4

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 1% of the mass of the equilibrium product, heat to 40°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Perform a flash operation on the liquid phase product, the feed temperature is 80° C., and the feed pressure is 0.05 MPa. The flash steam condensate is composed of methanol, formaldehyde, and methylal; the flash liquid is composed of polymer products with a degree of polymerization of 2 to 8; the polymer products with a degree of polymerization of 2 to 8 are subjected to fractional atmospheric distillation to collect The fraction at ~110°C is the dimerization product (PODE ₂ ), the fraction at ~160°C is the trimerization product (PODE ₃ ), the fraction at ~200°C is the tetramerization product (PODE ₄ ); The fraction is pentameric product (PODE ₅ ); the fraction collected at ~280°C is hexamerized product (PODE ₆ ); the fraction collected at ~320°C is heptamerized product (PODE ₇ ); the fraction collected at ~350°C is octamerized product (PODE ₈ ).

Example 5

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 3% of the mass of the equilibrium product, heat to 40°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Perform a flash operation on the liquid phase product, the feed temperature is 80° C., and the feed pressure is 0.05 MPa. The flash steam condensate is composed of methanol, formaldehyde, and methylal; the flash liquid is composed of polymer products with a degree of polymerization of 2 to 8; the polymer products with a degree of polymerization of 2 to 8 are subjected to fractional atmospheric distillation to collect The fraction at ~110°C is the dimerization product (PODE ₂ ), the fraction at ~160°C is the trimerization product (PODE ₃ ), the fraction at ~200°C is the tetramerization product (PODE ₄ ); The fraction is pentameric product (PODE ₅ ); the fraction collected at ~280°C is hexamerized product (PODE ₆ ); the fraction collected at ~320°C is heptamerized product (PODE ₇ ); the fraction collected at ~350°C is octamerized product (PODE ₈ ).

Example 6

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite and sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite and sodium bisulfite is 5% of the mass of the equilibrium product, and heat to 40°C for reaction. 1 hour processing;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Perform a flash operation on the liquid phase product, the feed temperature is 80° C., and the feed pressure is 0.05 MPa. The flash steam condensate is composed of methanol, formaldehyde, and methylal; the flash liquid is composed of polymer products with a degree of polymerization of 2 to 8; the polymer products with a degree of polymerization of 2 to 8 are subjected to fractional atmospheric distillation to collect The fraction at ~110°C is the dimerization product (PODE ₂ ), the fraction at ~160°C is the trimerization product (PODE ₃ ), the fraction at ~200°C is the tetramerization product (PODE ₄ ); The fraction is pentameric product (PODE ₅ ); the fraction collected at ~280°C is hexamerized product (PODE ₆ ); the fraction collected at ~320°C is heptamerized product (PODE ₇ ); the fraction collected at ~350°C is octamerized product (PODE ₈ ).

Example 7

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite and sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite and sodium bisulfite is 10% of the mass of the equilibrium product, and heat to 40°C for reaction. 1 hour processing;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Perform a flash operation on the liquid phase product, the feed temperature is 80° C., and the feed pressure is 0.05 MPa. The flash steam condensate is composed of methanol, formaldehyde, and methylal; the flash liquid is composed of polymer products with a degree of polymerization of 2 to 8; the polymer products with a degree of polymerization of 2 to 8 are subjected to fractional atmospheric distillation to collect The fraction at ~110°C is the dimerization product (PODE ₂ ), the fraction at ~160°C is the trimerization product (PODE ₃ ), the fraction at ~200°C is the tetramerization product (PODE ₄ ); The fraction is pentameric product (PODE ₅ ); the fraction collected at ~280°C is hexamerized product (PODE ₆ ); the fraction collected at ~320°C is heptamerized product (PODE ₇ ); the fraction collected at ~350°C is octamerized product (PODE ₈ ).

Example 8

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 15% of the mass of the equilibrium product, heat to 40°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Perform a flash operation on the liquid phase product, the feed temperature is 80° C., and the feed pressure is 0.05 MPa. The flash steam condensate is composed of methanol, formaldehyde, and methylal; the flash liquid is composed of polymer products with a degree of polymerization of 2 to 8; the polymer products with a degree of polymerization of 2 to 8 are subjected to fractional atmospheric distillation to collect The fraction at ~110°C is the dimerization product (PODE ₂ ), the fraction at ~160°C is the trimerization product (PODE ₃ ), the fraction at ~200°C is the tetramerization product (PODE ₄ ); The fraction is pentameric product (PODE ₅ ); the fraction collected at ~280°C is hexamerized product (PODE ₆ ); the fraction collected at ~320°C is heptamerized product (PODE ₇ ); the fraction collected at ~350°C is octamerized product (PODE ₈ ).

Example 9

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 30% of the mass of the equilibrium product, heat to 40°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Perform a flash operation on the liquid phase product, the feed temperature is 80° C., and the feed pressure is 0.05 MPa. The flash steam condensate is composed of methanol, formaldehyde, and methylal; the flash liquid is composed of polymer products with a degree of polymerization of 2 to 8; the polymer products with a degree of polymerization of 2 to 8 are subjected to fractional atmospheric distillation to collect The fraction at ~110°C is the dimerization product (PODE ₂ ), the fraction at ~160°C is the trimerization product (PODE ₃ ), the fraction at ~200°C is the tetramerization product (PODE ₄ ); The fraction is pentameric product (PODE ₅ ); the fraction collected at ~280°C is hexamerized product (PODE ₆ ); the fraction collected at ~320°C is heptamerized product (PODE ₇ ); the fraction collected at ~350°C is octamerized product (PODE ₈ ).

Comparative example 2

The extraction process described in this comparative example omits the aforementioned refining steps (i.e. steps S1 and S2), and directly puts the synthesized equilibrium system as a whole into the extraction unit (i.e. step S3), and uses the same extraction method as the above-mentioned example to carry out each step. Extraction of degree of polymerization products.

The distribution of each product obtained in the above-mentioned Examples 4-9 and Comparative Example 2 is shown in the table below.

As can be seen from the data in the above table, as the amount of sulfite increases, the purity of the separated product increases gradually. When the amount of sulfite increases to 5%, the purity of the product can reach 95%. As the dosage increases, the purity of the product will basically not increase, and the processing cost will increase. Considering the purity of the first product and the processing cost, the optimal amount of sulfite is selected as 5-15% of the total formaldehyde weight of the reactants.

The following examples 10-15 and comparative example 3 adopt the method disclosed in Example 1 in the Chinese patent document CN102180778A (application number 201110067354.4) "Method and Application of Low-carbon Mixed Alcohols to Prepare Polyoxymethylene Dialkyl Ether with Low Polymerization Degree", respectively An equilibrium system containing polymethoxydiethyl ether products, polymethoxydipropyl ether products, polymethoxydibutyl ether products, and polymethoxydiamyl ether products was prepared.

Example 10

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 10°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, distill out the fraction before 60°C, the initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is dimerization Product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Example 11

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 25°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, distill out the fraction before 60°C, the initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is dimerization Product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Example 12

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 30°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, distill out the fraction before 60°C, the initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is dimerization Product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Example 13

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 40°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, distill out the fraction before 60°C, the initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is dimerization Product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Example 14

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 50°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, distill out the fraction before 60°C, the initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is dimerization Product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Example 15

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 60°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, distill out the fraction before 60°C, the initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is dimerization Product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Comparative example 3

The extraction process described in this comparative example omits the aforementioned refining steps (i.e. steps S1 and S2), and directly puts the synthesized equilibrium system as a whole into the extraction unit (i.e. step S3), and uses the same extraction method as the above-mentioned example to carry out each step. Extraction of degree of polymerization products.

The distribution of each product obtained in the above-mentioned Examples 10-15 and Comparative Example 3 is shown in the table below.

As can be seen from the data in the above table, when the treatment temperature is 30°C, the purity of the separated product can reach 97%, when the temperature is low, the reaction cannot proceed, the treatment effect is poor, and the product purity is not high; and when the temperature is high At this time, sodium bisulfite is not stable enough, which will also affect the purification effect, so the optimal purification temperature is 25-50 °C.

The equilibrium products of polyoxymethylene dialkyl ethers used in the following examples 16-21 were all prepared by the following method: in a batch-type high-pressure reactor, petroleum C ₅ and formaldehyde content of 37% were sequentially added in a molar ratio of 2:4 Industrial formaldehyde, the water contained in industrial formaldehyde can be used as initiator to participate in the reaction, select p-toluenesulfonic acid accounting for 2% of the total weight of the reactant as a catalyst and put it into the reactor together, fill the air in the reactor with nitrogen replacement, control The initial pressure in the reaction kettle is 0.2Mpa, and the constant temperature is kept at 70-90°C under stirring at 100rpm for 10 hours until the components are balanced to obtain a balanced product of polyoxymethylene dialkyl ether. The balanced product of polyoxymethylene dialkyl ether is The content of formaldehyde was 3.1 wt%.

Example 16

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 30°C for reaction, and treat for 0.5 hours;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, and distill out the fraction before 60°C. The initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is divided into two Polymerization product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Example 17

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 30°C for reaction, and treat for 1 hour;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, and distill out the fraction before 60°C. The initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is divided into two Polymerization product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Example 18

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 30°C for reaction, and treat for 1.5 hours;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, and distill out the fraction before 60°C. The initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is divided into two Polymerization product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Example 19

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 30°C for reaction, and treat for 2 hours;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, and distill out the fraction before 60°C. The initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is divided into two Polymerization product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

Example 20

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, heat to 30°C for reaction, and treat for 2.5 hours;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, and distill out the fraction before 60°C. The initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is divided into two Polymerization product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

The distribution of each product obtained in the above-mentioned Examples 16-20 and Comparative Example 1 is shown in the table below.

It can be seen from the data in the above table that when the processing time is 1 hour, the purity of the separated product has reached 97.0%, and the purity of the product will basically not increase after the reaction time is continued. Therefore, the optimal purification time should be set to 1 hour.

Example 21

This embodiment provides a method for refining and purifying polyoxymethylene dialkyl ether, specifically:

S1. Add sodium bisulfite to the equilibrium product of polyoxymethylene dialkyl ether, heat to 30°C for reaction, the input amount of sodium bisulfite is 10% of the mass of the equilibrium product, add in two times, the first time Add 5% and heat for 30 minutes, then add 5% for the second time and heat for 30 minutes;

S2, performing solid-liquid separation on the reaction liquid obtained in step S1, and collecting liquid phase products;

S3. Carry out fractional atmospheric pressure distillation on the liquid phase product, and distill out the fraction before 60°C. The initial boiling point ~60°C is the unreacted raw material (formaldehyde, methanol and methylal), and the fraction collected at ~110°C is divided into two Polymerization product (PODE ₂ ), the fraction collected at ~160°C is trimerization product (PODE ₃ ), the fraction collected at ~200°C is tetramerization product (PODE ₄ ); the fraction collected at ~250°C is pentamerization product (PODE ₅ ); the fraction collected at ~280°C was the hexamer product (PODE ₆ ); the fraction collected at ~320°C was the heptamer product (PODE ₇ ); the fraction collected at ~350°C was the octamer product (PODE ₈ ).

The distribution of each product obtained in the above-mentioned Example 17 and Example 21 is shown in the table below.

It can be seen from the data in the above table that when the treatment method is changed to two additions, the product purity can reach 99%. The method of adding sulfite in stages is beneficial to break the adsorption balance between sulfite and formaldehyde, making the reaction Proceed in the positive direction, fully react to remove formaldehyde, and ultimately facilitate product separation and obtain higher purity products.

It can be seen from the data of the above examples that after the product of the equilibrium system of the synthesis unit is subjected to sulfite refining, the extraction rate of the product of each degree of polymerization is significantly improved compared with the system that directly enters the extraction unit. It can be seen that the removal of unreacted formaldehyde in the equilibrium system has become a key factor limiting the extraction of the product of the extraction unit; and the whole process is a solid-phase reaction, which does not produce water that has a greater impact on products with a low degree of polymerization, and does not require additional drying steps, and The separation of products and impurities is simple and has great significance for the extraction of products in polyoxymethylene dialkyl ether systems.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. However, the obvious changes or changes derived therefrom still fall within the scope of protection of the present invention.

Claims (10)

1. a refining method that reaches the purification polyoxymethylene dialkyl ether is characterized in that, comprises the steps:

S1, in preparation polyoxymethylene dialkyl ether reacted equilibrium products, drop into sulphite, carry out reflux condensation mode and handle;

S2, the mixture that step S1 processing is obtained carry out solid-liquid separation, collect liquid product;

S3, the liquid product that collection is obtained carry out follow-up extraction operation steps.

2. the method for refining and purification polyoxymethylene dialkyl ether according to claim 1 is characterized in that, described sulphite is one or more the combination in S-WAT, sodium bisulfite and the Sodium Metabisulfite.

3. the refining method that reaches the purification polyoxymethylene dialkyl ether according to claim 1 and 2 is characterized in that the adding quality of described sulphite is 1%～30% of described equilibrium products quality.

4. the refining method that reaches the purification polyoxymethylene dialkyl ether according to claim 3 is characterized in that the adding quality of described sulphite is 5%～15% of described equilibrium products quality.

5. according to the arbitrary described refining method that reaches the purification polyoxymethylene dialkyl ether of claim 1～4, it is characterized in that among the described step S1, the control temperature that described reflux condensation mode is handled is 10～60 ℃.

6. the refining method that reaches the purification polyoxymethylene dialkyl ether according to claim 5 is characterized in that described temperature is 25～50 ℃.

7. according to the arbitrary described refining method that reaches the purification polyoxymethylene dialkyl ether of claim 1～6, it is characterized in that among the described step S1, the step of the described sulphite of described adding is divided once input or repeatedly dropped into and carry out.

8. according to the arbitrary described refining method that reaches the purification polyoxymethylene dialkyl ether of claim 1～7, it is characterized in that among the described step S1, the treatment time of described reflux condensation mode step is 0.5-2.5h.

9. the refining method that reaches the purification polyoxymethylene dialkyl ether according to claim 8 is characterized in that the described treatment time is 1-2h.

10. according to the arbitrary described refining method that reaches the purification polyoxymethylene dialkyl ether of claim 1-9, it is characterized in that purification step described in the described step S3 is air distillation, underpressure distillation, flash distillation, rectifying, one or more the combination in being separated, filtering.