A continuous catalytic extraction process for the production of polymethoxy dimethyl ether

Abstract

The application discloses a continuous catalytic extraction method for preparing polyoxymethylene dimethyl ethers from methanol and formaldehyde aqueous solution, which comprises the following steps: a) introducing material A containing formaldehyde and material B containing recycled reaction polyoxymethylene dimethyl ethers into a pre-reactor for pre-reaction to obtain pre-reaction material I; b) introducing the pre-reaction material I obtained in step a) and raw material C containing methanol into a catalytic extraction tower or a multi-stage catalytic extraction reactor, and contacting with an extractant in countercurrent to carry out catalytic reaction and extraction, so as to obtain extraction phase material II and raffinate phase material III; wherein the raw material C containing methanol is fed from the middle of the catalytic extraction tower or the middle of a certain stage of the multi-stage catalytic extraction reactor. The method can improve the concentration of polyoxymethylene dimethyl ethers in the extraction phase obtained from the catalytic extraction tower or the multi-stage catalytic extraction reactor, and has the advantages of low raw material cost and easy product separation.

Description

TECHNICAL FIELD

[0001] The present application relates to a continuous catalytic extraction process for the production of polyoxymethylene dimethyl ethers with more than dimerization from methanol and aqueous formaldehyde solution. BACKGROUND

[0002] Polyoxymethylene dimethyl ethers, also known as polyoxymethylene methylal, polyformal dimethyl ether, PODE for short n (polyoxymethylene dimethyl ethers).

[0003] PODE1, also known as dimethyl ether, is a colorless, non-toxic and environmentally friendly chemical raw material, which is usually prepared by alcohol aldehyde condensation reaction of methanol and formaldehyde solution. Due to the presence of a large amount of water (including water brought in by formaldehyde solution and water generated by reaction) in the reaction process, the reaction is limited by chemical equilibrium, and at present, catalytic rectification technology is generally used to break the limitation of chemical equilibrium.

[0004] PODE 3-4 PODE has the characteristics of high cetane number and high oxygen content, and can be mutually soluble with diesel oil, and its various performance indicators are close to diesel oil, and is considered to be an ideal diesel oil additive. Although PODE with higher polymerization degree has potential low temperature condensation risk, the content of PODE 5-8 in the general synthesis of polyoxymethylene dimethyl ether product is very low and is not enough to cause fuel low temperature condensation, so some people also think that PODE 3-5 or PODE 3-8 with a small amount of high polymerization degree component is also a suitable diesel oil additive component.

[0005] PODE 3+ is generally synthesized by a compound providing oligomeric formaldehyde (formaldehyde solution, trioxymethylene or polyoxymethylene, etc.) and a compound providing blocking methyl (methanol, dimethyl ether or methylal, etc.) in the presence of an acid catalyst, while a large amount of PODE 1-2 is generated. PODE2 is also a potential chemical raw material with certain market prospect.

[0006] Japan Asahi Kasei Corporation discloses a catalytic rectification method for producing methylal from formaldehyde solution and methanol in Chinese patent CN 1020450 C, which adopts a form of a side reactor arranged outside the catalytic rectification tower, and uses a macroporous or gel type cation exchange resin as a catalyst.

[0007] Chinese patent CN 102351666 A discloses a catalytic rectification method for continuously producing high-concentration methylal from formaldehyde solution and methanol, which also adopts a form of a side reactor.

[0008] Chinese patent authorization announcement number CN 100344596 C discloses a method for preparing high purity methylal by combining continuous reaction rectification and liquid-liquid extraction, the mixture of methylal, methanol and water obtained after reaction rectification is extracted in a liquid-liquid extraction tower to obtain high purity methylal, and the extractant is glycerol or dimethanol amine.

[0009] Chinese patent CN 102070417 A discloses a catalytic rectification process and production equipment for producing methylal from formaldehyde solution and methanol, in which cation exchange resin is used as catalyst, and a catalytic rectification tower filled with catalyst bunched package is used.

[0010] Chinese patent CN 101182367 discloses a method for preparing polyoxymethylene dimethyl ethers by using methanol and trioxymethylene as reactants and ionic liquid as catalyst, which has the characteristics of mild reaction condition, high catalyst activity, high conversion rate, simple reaction process, easy operation and good reaction product distribution.

[0011] Chinese patent CN 101665414 discloses a method for preparing polyoxymethylene dimethyl ethers by using methylal and trioxymethylene as reactants and functionalized acidic ionic liquid as catalyst, which has the characteristics of mild reaction condition, high catalyst activity, high conversion rate, simple reaction process, easy operation and good reaction product distribution.

[0012] Chinese patent CN 101768057 discloses a method for preparing polyoxymethylene dimethyl ethers by using methanol and trioxymethylene as reaction raw materials, in which solid superacid catalyst is used, the reaction temperature is 70-200℃, and the reaction pressure is 0.5-6 MPa.

[0013] Chinese patent CN 102040488 discloses a method for preparing polyoxymethylene dimethyl ethers by using methanol, methylal and trioxymethylene as reaction raw materials, in which molecular sieve catalyst is used, the reaction temperature is 50-200℃, and the reaction pressure is 0.1-10 MPa.

[0014] Chinese patent CN 102040490 discloses a method for preparing polyoxymethylene dimethyl ethers by using methanol, methyl al and polyoxymethylene as reaction raw materials, in which solid superacid catalyst is used, the reaction

[0015] Chinese patents CN 102372611 and 102372612 respectively disclose a method for preparing polyoxymethylene dimethyl ethers by using methylal and trioxymethane as reaction raw materials in a catalytic rectification tower.

[0016] The above patents for preparing PODE 3-8 use trioxymethylene or polyoxymethylene as raw material for providing oligomeric formaldehyde, and the reaction system does not contain water or contains very low amount of water, and PODE nhigh, and the selectivity of PODE 3-8 is also high, but the price of trioxane or polyoxymethylene is high, so the production cost is high.

[0017] One of the main problems in producing polyoxymethylene dimethyl ethers from cheap methanol and formaldehyde aqueous solution is that the reaction system contains a large amount of water, including the water brought in by the formaldehyde aqueous solution and the water generated by the reaction. Due to the large amount of water, the equilibrium conversion of methanol and formaldehyde to PODE n is greatly reduced, and the generated PODE n product is mainly PODE 1-2 , and the selectivity of PODE 3-8 is very low.

[0018] Another problem is that in the presence of liquid water and methanol, only a small part of formaldehyde exists in the form of formaldehyde monomer molecules, and most of the formaldehyde reacts with water to generate methyl glycol and its polymer polyoxymethylene glycol, or reacts with methanol to generate hemiacetals with different polymerization degrees; these reactions are reversible and can occur without catalyst, and can be easily converted in the distillation separation process, making it difficult to completely separate the target product PODE n from these substances by general distillation methods.

[0019] Chinese patent CN 106542977 discloses a method for preparing polyoxymethylene dimethyl ethers, which introduces an extractant into the reaction system, and the reaction and extraction are combined under the catalysis of an acidic catalyst. After the reaction is completed, the organic phase and the aqueous phase are separated, and the organic phase is refined to obtain polyoxymethylene dimethyl ethers. By introducing an extractant, the reaction raw materials are extracted into the extraction phase for reaction, which effectively avoids the side reaction of the reaction products with water, and can effectively improve the conversion rate of the raw materials and the selectivity and yield of the products. However, formaldehyde cannot be completely reacted, which still causes great difficulty in subsequent separation, including the separation of water in the reaction mixture and the recovery of formaldehyde. SUMMARY

[0020] The purpose of the present application is to provide a continuous catalytic extraction method for preparing polyoxymethylene dimethyl ethers (PODE 2+ ) from methanol and formaldehyde aqueous solution, which has the advantages of low raw material cost and easy product separation. This method can produce one of the two products, PODE2, diesel additive component (PODE 3-4 , PODE 3-5 or PODE 3-8 ), or can simultaneously produce the two products in any ratio.

[0021] As an embodiment, the method for preparing polyoxymethylene dimethyl ethers from methanol and formaldehyde aqueous solution is characterized in that it comprises the following steps:

[0022] a) introducing a formaldehyde-containing material A and a material B containing polyoxymethylene dimethyl ethers from a cyclic reaction into a pre-reactor for pre-reaction to obtain a pre-reaction material I;

[0023] b) introducing the pre-reaction material I obtained in step a) and a methanol-containing material C into a catalytic extraction column or a multi-stage catalytic extraction reactor for catalytic reaction and extraction with an extractant countercurrently to obtain an extract phase material II and a raffinate phase material III;

[0024] The methanol-containing material C is fed from the middle of the catalytic extraction column or from the middle of a certain stage of the multi-stage catalytic extraction reactor.

[0025] As another embodiment, the method for preparing polyoxymethylene dimethyl ethers from methanol and an aqueous formaldehyde solution is characterized in that the catalytic extraction column is alternatively provided with a catalyst bed and a separation member, and the separation member comprises a separation tray and / or a packing;

[0026] The formaldehyde-containing material A and the material B containing polyoxymethylene dimethyl ethers from a cyclic reaction are introduced into the catalytic extraction column together, first into one of the catalyst beds for catalytic reaction, then extracted with an extractant countercurrently, and the catalytic reaction and extraction processes are alternately carried out to obtain an extract phase material II and a raffinate phase material III;

[0027] The methanol-containing material C is fed from the middle of the catalytic extraction column.

[0028] In all the above embodiments,

[0029] Optionally, the catalytic extraction column is an extraction column containing at least one catalyst bed. The catalytic reaction process and the extraction process can be carried out simultaneously or alternately multiple times in the column.

[0030] Optionally, the multi-stage catalytic extraction reactor is a multi-stage extraction device containing at least one catalyst bed.

[0031] Optionally, the catalyst bed is arranged in the water phase channel and / or the two-phase mixing area of the catalytic extraction column or the multi-stage catalytic extraction reactor.

[0032] The extract phase material II mainly contains an extractant, methylal and polyoxymethylene dimethyl ethers.

[0033] Optionally, the formaldehyde-containing material A is an aqueous formaldehyde solution.

[0034] Optionally, the methanol-containing material C is methanol.

[0035] The polyoxymethylene dimethyl ether in material B containing the polyoxymethylene dimethyl ether of the cyclic reaction comes from the isolate of the extract phase material II and / or freshly added methylal.

[0036] Optionally, all the polyoxymethylene dimethyl ether in material B is derived from the isolates of the extraction phase material II.

[0037] Optionally, the weight ratio of the extractant feed rate to the feed rate of (formaldehyde-containing material A + methanol-containing material C) is 0.3 to 12:1. A larger extractant feed rate requires fewer theoretical stages in the catalytic extraction tower or multi-stage catalytic extraction reactor, but increases the energy consumption for extractant recovery.

[0038] Optionally, the extractant is selected from at least one of halogenated hydrocarbons, aromatic hydrocarbons, alkanes, and cycloalkanes.

[0039] Optionally, the haloalkane is selected from at least one of dichloroethane, dichloropropane, chlorobenzene, and bromobenzene.

[0040] Optionally, the aromatic hydrocarbon is selected from at least one of benzene, toluene, ethylbenzene, xylene, n-propylbenzene, isopropylbenzene, methyl ethylbenzene, and butylbenzene.

[0041] Optionally, the alkane is selected from at least one of n-alkanes having 5 to 10 carbon atoms and isoalkanes having 5 to 10 carbon atoms.

[0042] Optionally, the cycloalkane is selected from at least one of cyclohexane, methylcyclopentane, methylcyclohexane, and ethylcyclohexane.

[0043] Optionally, the extractant is xylene.

[0044] Optionally, the extractant is cumene.

[0045] Optionally, the extractant is a mixture of toluene and ethylbenzene.

[0046] Optionally, the extractant is a mixture of 1,2-dichloroethane and 1,2-dichloropropane.

[0047] Optionally, the extractant is benzene.

[0048] Optionally, the extractant is a mixture of chlorobenzene and bromobenzene.

[0049] Optionally, the extractant is a mixture of n-hexane, n-heptane, isoheptane, n-octane, and isooctane.

[0050] Optionally, the extractant is a mixture of n-propylbenzene, ethylbenzene, and butylbenzene.

[0051] Optionally, the extractant is a mixture of cyclohexane, methylcyclopentane, methylcyclohexane, and ethylcyclohexane.

[0052] The catalyst for the catalytic reaction is selected from at least one of solid acid catalysts.

[0053] Optionally, the solid acid catalyst is selected from strongly acidic cation exchange resins and / or hydrogen molecular sieve catalysts.

[0054] Optionally, the hydrogen-type molecular sieve catalyst contains HZSM-5 molecular sieve and / or Hβ molecular sieve.

[0055] The catalysts packed in the pre-reactor and the catalytic extraction tower or multi-stage catalytic extraction reactor can be the same or different.

[0056] Optionally, the reaction temperature of the pre-reactor is 40–140°C.

[0057] Optionally, the upper limit of the reaction temperature of the pre-reaction is selected from 80℃, 90℃, 100℃, 110℃, 120℃, 130℃ or 140℃; the lower limit is selected from 40℃, 50℃, 60℃ or 70℃.

[0058] Optionally, the reaction temperature in the catalytic extraction tower or multi-stage catalytic extraction reactor is 40–140°C.

[0059] Optionally, the upper limit of the reaction temperature in the catalytic extraction tower or multi-stage catalytic extraction reactor is selected from 80°C, 90°C, 100°C, 110°C, 120°C, 130°C or 140°C; the lower limit is selected from 40°C, 50°C, 60°C or 70°C.

[0060] The reaction temperature of the pre-reaction can be the same as or different from the reaction temperature in the catalytic extraction tower or multi-stage catalytic extraction reactor. The reaction temperature of the pre-reaction can be higher than, equal to or lower than the reaction temperature in the catalytic extraction tower or multi-stage catalytic extraction reactor, all within the above-mentioned reaction temperature range.

[0061] Optionally, formaldehyde can be back-extracted from the extraction phase material II using water or methanol to obtain an aqueous solution or a methanol solution containing formaldehyde; the aqueous solution or methanol solution containing formaldehyde can then be returned to the catalytic extraction tower or multi-stage catalytic extraction reactor for further reaction.

[0062] Optionally, at least a portion of the extractant-free material II can be refluxed back to the catalytic extraction tower or multi-stage catalytic extraction reactor. This can increase the concentration of polyoxymethylene dimethyl ether in the extractant phase.

[0063] Specifically, when a catalytic extraction tower is used, in the case where the aqueous phase is the heavy phase and the extractant is the light phase, the material I or materials A and B flowing out of the pre-reactor are fed from the top of the catalytic extraction tower, and the extractant is fed from the bottom of the catalytic extraction tower. The extract phase material, mainly composed of extractant and polyoxymethylene dimethyl ether, is obtained from the top of the tower, and the raffinate material, mainly composed of water, is obtained from the bottom of the tower.

[0064] In the method described above, when the aqueous phase is the light phase and the extractant is the heavy phase, the material I or materials A and B flowing out of the pre-reactor are fed from the bottom of the catalytic extraction tower, and the extractant is fed from the top of the catalytic extraction tower. The extract phase material, mainly composed of extractant and polyoxymethylene dimethyl ether, is obtained from the bottom of the tower, and the raffinate material, mainly composed of water, is obtained from the top of the tower.

[0065] Methanol and formaldehyde can undergo a condensation reaction in aqueous solution under suitable catalysts to produce polyoxymethylene dimethyl ethers (PODEs) with varying degrees of polymerization. This reaction is reversible, and the conversion rate is greatly limited by chemical equilibrium. Furthermore, the higher the degree of polymerization of the product, the lower the selectivity. Therefore, PODEs are suitable as diesel fuel additives. 3-8 The yield is relatively low. Water has a significant impact on this reaction; the higher the water content in the reaction system, the lower the conversion rate of formaldehyde and methanol, and the more concentrated the reaction products are in low-polymerization products such as methylal. Conversely, the higher the methanol-to-formaldehyde ratio, the higher the formaldehyde conversion rate and the lower the methanol conversion rate, while the reaction products are more concentrated in low-polymerization products such as methylal.

[0066] In the technical solution of this invention, in the presence of a suitable water-immiscible extractant, methanol and formaldehyde mainly exist in the aqueous phase, while the reaction product polyoxymethylene dimethyl ether is enriched in the extract phase. The catalyst is packed into the raffinate (aqueous phase) channel, allowing only the aqueous phase material to contact the catalyst and diffuse into its particle interior to react and generate polyoxymethylene dimethyl ether. Simultaneously, the extract phase does not contact the catalyst and therefore does not enter its particle interior to contact its surface active centers; that is, the polyoxymethylene dimethyl ether in the extract phase will not decompose under the action of the catalyst. Thus, although the condensation reaction in the aqueous phase is still limited by chemical equilibrium, no catalytic reaction occurs in the extract phase, and the content of polyoxymethylene dimethyl ether is not limited by chemical equilibrium. Therefore, the conversion rate of methanol and formaldehyde can greatly exceed the equilibrium conversion rate. Alternatively, the catalyst can be packed into the two-phase mixing region. Due to the catalyst's strong hydrophilicity, only the aqueous phase material can enter the catalyst particle interior to undergo a catalytic reaction, while the extract phase material cannot enter the catalyst particle interior and therefore will not undergo a catalytic reaction, achieving the same effect.

[0067] In a first embodiment of the present invention, an aqueous formaldehyde solution and PODE from a circulating reaction are first introduced into a pre-reactor for a complete reaction, resulting in water, formaldehyde, methanol, and PODE of various degrees of polymerization.n A mixture (n = 1, 2, 3, etc.) with a composition close to chemical equilibrium is used. Methanol is derived from the hydrolysis of PODE in a circulating reaction. This reaction consumes a certain amount of water, while the conversion of PODE to other degrees of polymerization does not produce water. This reduces the water content in the reaction system, shifting the chemical equilibrium towards formaldehyde conversion and the formation of higher-degree-of-polymerization PODEs, thus increasing the formaldehyde conversion rate and the concentration of the target product (PODE2 or PODEs suitable as diesel additives). The reaction mixture is then introduced into a catalytic extraction tower or multi-stage catalytic extraction reactor for countercurrent contact with the extractant. This maximizes the concentration of the target product in the extract phase obtained from the catalytic extraction tower or multi-stage catalytic extraction reactor, thereby improving production efficiency.

[0068] If the formaldehyde aqueous solution and the PODE from the circulating reaction directly enter the catalytic extraction tower or multi-stage catalytic extraction reactor and come into contact with the extraction phase, since the aqueous phase is essentially free of the target product, a portion of the target product in the extraction phase will enter the aqueous phase, resulting in a decrease in the concentration of the target product in the extraction phase obtained from the catalytic extraction tower or multi-stage catalytic extraction reactor. The method of setting up a pre-reactor as described in the first embodiment above can avoid this adverse situation.

[0069] In the second embodiment, when the formaldehyde aqueous solution and the PODE from the circulating reaction are introduced into the catalytic extraction tower, they first enter the catalyst bed for reaction, and then come into contact with the extraction phase for extraction, which can also achieve similar effects to those described above.

[0070] In a catalytic extraction tower or multi-stage catalytic extraction reactor, the aqueous phase (methanol and formaldehyde aqueous solution) and the extractant phase are in countercurrent contact, undergoing catalytic reaction and extraction processes simultaneously or alternately. Near the inlet of the aqueous phase, the water concentration is low, while the formaldehyde concentration is high, resulting in a high concentration of polyoxymethylene dimethyl ether (POD) (less constrained by chemical equilibrium). The extractant phase, carrying POD extracted from the downstream aqueous phase (at a lower concentration), contacts it for further extraction, achieving an even higher concentration of POD. Near the outlet of the aqueous phase, the formaldehyde concentration is already low. After contact with fresh extractant and extraction of POD, the condensation reaction between formaldehyde and methanol is promoted. With excess methanol, the formaldehyde in the aqueous phase can be almost completely converted, thus avoiding the difficulty of separating formaldehyde.

[0071] The basic requirement for selecting an extractant is that PODE... n The distribution ratio (PODE in the extract phase) n Concentration of PODE in aqueous phase nThe ratio of their concentrations must be greater than the distribution ratio of methanol and formaldehyde (the ratio of their concentrations in the extract phase to those in the aqueous phase). Meeting this requirement breaks the chemical equilibrium constraint; the greater the difference, the more pronounced the effect. (PODE) n The larger the distribution ratio of methanol and formaldehyde, the better the enrichment of the reaction product polyoxymethylene dimethyl ether in the extraction phase, the less extractant is needed, the lower the energy consumption required for extractant recovery, and the lower the production cost. The smaller the distribution ratio of methanol and formaldehyde, the higher the concentration of methanol and formaldehyde in the aqueous phase, the easier the reaction proceeds, the lower the concentration of methanol and formaldehyde in the extraction phase, and the easier the recovery.

[0072] PODE of partial extractant n The distribution ratio increases with increasing n, which is beneficial for increasing the PODE content in the product. 3-8 The proportion.

[0073] Feeding methanol from the middle of the catalytic extraction tower or an intermediate stage of a multi-stage catalytic extraction reactor can improve the yield of the reaction product PODE from the catalytic extraction tower or multi-stage catalytic extraction reactor. n The proportion of high-polymerization-degree PODEs is increased, and the amount of PODEs recycled in the circulating reaction is reduced. In this methanol-feed method, downstream of the catalytic extraction tower or multi-stage catalytic extraction reactor (in the direction of aqueous phase material flow), excess methanol ensures complete formaldehyde reaction, with the main reaction product being methylal. Upstream (in the direction of aqueous phase material flow), a high ratio of formaldehyde groups to terminally capped methyl groups is maintained, while reducing the water generated during the condensation reaction of methanol and formaldehyde, which is conducive to generating more high-polymerization-degree PODEs. Methylal generated in the downstream aqueous phase enters the extraction phase and returns to the upstream of the aqueous phase; some enters the aqueous phase to react with formaldehyde to generate high-polymerization-degree PODEs.

[0074] The main components of the obtained extract phase are the extractant and polyoxymethylene dimethyl ether, with very low levels of formaldehyde, methanol, and water. Formaldehyde mainly exists in the form of methyl glycol, polyoxymethylene glycol, and hemiacetal, and easily decomposes into monomeric formaldehyde, water, and methanol. Common distillation methods are difficult to use effectively to remove it. Therefore, it can be back-extracted with water or methanol to remove the small amount of formaldehyde before separating the other components. The formaldehyde-containing back-extraction solution can be returned to the catalytic extraction tower or multi-stage catalytic extraction reactor for further reaction. The feed location is in the middle of the catalytic extraction tower or in one of the middle stages of the multi-stage catalytic extraction reactor.

[0075] The extractant obtained after phase separation can be recycled, while the product, polyoxymethylene dimethyl ether, can be divided into dimethyl acetal (DMM), dioxymethylene dimethyl ether (PODE2), and diesel additive component (PODE). 3-4 PODE 3-5 or PODE 3-8 ), heavy components (PODE with a higher degree of polymerization than diesel additive components), and other components.

[0076] PODE2 and diesel additive components can both be used as final products. Either product can be produced individually, or both can be produced simultaneously in any proportion. The remaining PODE... n (i.e., the PODE (circulating reaction) then returns to the catalytic extraction reaction system for recycling or enters another reactor for reaction, transforming it into the desired final product.

[0077] The cyclic reaction PODE includes DMM and heavy components; when PODE2 is the main final product, it also includes diesel additive components; when diesel additive components are the main final product, it also includes PODE2.

[0078] Heavy components can react with methanol or PODE under the action of a catalyst. 1-2 The compound that provides the terminal methyl group reacts to convert PODE to a lower degree of polymerization. Two reaction methods can be employed: one is to return the PODE as part of a recycling reaction to the catalytic extraction tower or multi-stage catalytic extraction reactor for further recycling; the other is to react it with an appropriate amount of methanol or DMM and / or PODE2 in a separate reactor.

[0079] The formaldehyde aqueous solution used as the reaction raw material can be an aqueous solution with a formaldehyde concentration of 10-80 wt%, which may contain a small amount of methanol. The higher the formaldehyde concentration, the smaller the recycling volume of the PODE reaction, and the higher the production efficiency. n The selectivity (based on carbon number) can reach 96-99.5%, with trioxymethylene being the main byproduct and other byproducts having a selectivity of <1%. Trioxymethylene can be separated as a product, recycled back into the catalytic extraction reaction system, or reacted in a separate reactor with methanol or DMM and / or PODE2 to produce PODE2. n .

[0080] The following is a technical solution of the present invention for producing PODE using ethylbenzene as an extractant. 3-8 The specific implementation plan.

[0081] As attached Figure 1 As shown, formaldehyde aqueous solution (S1) reacts with PODE in a cyclic reaction. 1-2 (S11), PODE 9+(S16) After mixing in mixer (M1) (S4), the mixture enters pre-reactor (R1) containing a strong acid cation exchange resin catalyst. After sufficient reaction (S5), it is fed from the top of catalytic extraction tower or multi-stage catalytic extraction reactor (T1) containing the strong acid cation exchange resin catalyst. Methanol (S2) is fed from the middle of the tower, and ethylbenzene (S3) is fed from the bottom of the tower. The raffinate (S6), i.e., the aqueous phase, is collected from the bottom of the catalytic extraction tower or multi-stage catalytic extraction reactor (T1). It is basically free of formaldehyde and other organic matter and can be directly... As part of wastewater treatment, the extract phase (S7), i.e., the organic phase, collected from the top of the tower, is fed into the bottom of the back-extraction tower (T2). Formaldehyde and methanol are back-extracted from it by water (S8), which is fed from the top of the tower, and then collected from the top of the tower (back-extracted organic phase S10). The aqueous solution of formaldehyde and methanol collected from the bottom of the tower (back-extracted aqueous phase S9) is returned to the catalytic extraction tower or multi-stage catalytic extraction reactor (T1) for further reaction. Due to its high water content, it is fed from the middle of the tower. The back-extracted organic phase (S10) enters the light component removal tower (T3) for distillation separation, and the light component PODE is obtained at the top of the tower. 1-2 (S11), the bottom liquid (S12) enters the ethylbenzene recovery tower (T4) to recover the extractant ethylbenzene; the recovered ethylbenzene (S13) obtained from the top of the ethylbenzene recovery tower (T4) is returned to the catalytic extraction tower or the multi-stage catalytic extraction reactor (T1) for recycling (i.e., S3). If necessary, some fresh ethylbenzene can be added. The bottom liquid (S14) enters the PODE tower (T5) for rectification and separation; the product PODE is obtained from the top of the PODE tower (T5). 3-8 (S15), PODE obtained at the bottom of the tower 9+ (S16) and formaldehyde aqueous solution (S1), PODE of the cyclic reaction 1-2 (S11) After being mixed in the mixer (M1), it enters the pre-reactor (R1).

[0082] In this application, "polymethoxydimethyl ether" refers to the target product of the technical solution of this application, which is PODE2, a diesel additive component (PODE2). 3-4 PODE 3-5 or PODE 3-8 One of the two products can be produced simultaneously in any proportion.

[0083] The polyoxymethylene dimethyl ether in the cyclic reaction refers to methyl acetal other than the target product. For example, when the target product is PODE2, the polyoxymethylene dimethyl ether in the cyclic reaction is PODE1, PODE2, etc. 3-4 PODE 3-5 PODE 3-8 etc.; for example, when the target product is PODE 3-4 PODE 3-5 or PODE 3-8At that time, the polyoxymethylene dimethyl ethers in the cyclic reaction are PODE1, PODE2, etc.

[0084] In this application, the use of strongly acidic cation exchange resins is common knowledge to those skilled in the art and will not be described in detail here.

[0085] The beneficial effects of this invention include: the ability to produce PODE2 and / or diesel additive components at low cost and high efficiency using inexpensive formaldehyde aqueous solution as raw material. Attached Figure Description

[0086] Figure 1 This application uses ethylbenzene as an extractant to produce PODE. 3-8 A simplified process flow diagram.

[0087] Components and reference numerals:

[0088] S1: Formaldehyde aqueous solution, S2: Methanol, S3: Ethylbenzene, S4: R1 feed.

[0089] S5: R1 discharge, S6: Raffinate phase, S7: Extract phase, S8: Water, S9: Back-extraction aqueous phase, S10: Back-extraction organic phase, S11: PODE 1-2 S12: T3 tower bottom liquid, S13: Recovered ethylbenzene, S14: T4 tower bottom liquid, S15: PODE 3-8 S16: PODE 9+

[0090] M1: Mixer, R1: Pre-reactor, T1: Catalytic extraction column, T2: Back-extraction column

[0091] T3: Light benzene removal tower; T4: Ethylbenzene recovery tower; T5: PODE tower. Detailed Implementation

[0092] The present invention is described in detail below through embodiments, but the present invention is not limited to these embodiments.

[0093] In the following examples and comparative examples, the methanol, formaldehyde aqueous solution, paraformaldehyde, and methylal used were all analytical grade reagents; the formaldehyde aqueous solution contained 38 wt% formaldehyde and 3 wt% methanol. Dimeric polyoxymethylene dimethyl ether (PODE) 2+ It was recovered from the reaction solution with a purity of 99 wt%.

[0094] The strong acidic cation exchange resin catalyst used in the examples was a D006 resin catalyst, purchased from Hebei Kairui Chemical Co., Ltd.

[0095] The molecular sieves HZSM-5 and Hβ used in the examples were purchased from the catalyst factory of Nankai University.

[0096] Example 1

[0097] The pre-reactor is a stainless steel fixed-bed reactor with an inner diameter of 14 mm and a height of 0.3 m, and is filled with 40 ml of strong acid cation exchange resin catalyst. The outlet of the pre-reactor is connected to the heavy phase feed pipe of the catalytic extraction reactor.

[0098] A stainless steel catalytic extraction reactor with an inner diameter of 20 mm and a height of 1.3 m is filled with 160 ml of uniformly mixed strong acid cation exchange resin catalyst and 200 ml of Φ3×3 mm stainless steel θ mesh rings, with a filling height of 1.2 m, leaving an empty tube 10 cm above. A heavy phase feed pipe is installed at the top of the reactor, at the top of the catalyst and θ mesh ring bed. A light phase discharge pipe is installed at the top of the reactor and connected to a back pressure valve to control the reaction pressure. A light phase feed pipe is installed at the bottom of the reactor. A temperature- and pressure-resistant glass tube is connected to the bottom of the reactor for observing the two-phase stratification and is also connected to the heavy phase discharge pipe.

[0099] 38wt% formaldehyde aqueous solution (containing 3wt% methanol) and PODE 1-2 (DMM accounts for 60 wt%) After mixing, it enters the pre-reactor at feed rates of 11.7 ml / min and 8.2 ml / min respectively; methanol is fed from a height of 0.3 m in the catalytic extraction reactor at a feed rate of 3.1 ml / min; mixed xylene is used as the extractant and is fed from the bottom of the reactor at a feed rate of 56 ml / min; the reaction temperature of the pre-reactor is 60 ℃, the reaction temperature of the catalytic extraction reactor is 60 ℃, and the reaction pressure is 0.3 MPa.

[0100] The light phase discharge rate from the top of the reactor was 63.6 g / min, containing 2.7 wt% formaldehyde, 1 wt% methanol, 0.2 wt% water, 6.4 wt% DMM, 4.6 wt% PODE2, and PODE4. 3+ 7 wt%, the remainder being mixed xylenes and trace byproducts.

[0101] The bottom heavy phase discharge rate of the reactor is 7.8 g / min, which includes 3.1 wt% methanol, 0.01 wt% formaldehyde, 0.4 wt% mixed xylene, and the remainder is water.

[0102] Example 2

[0103] The same pre-reactor, catalytic extraction reactor, catalyst, catalyst loading method and loading amount as in Example 1 were used.

[0104] 38wt% formaldehyde aqueous solution (containing 3wt% methanol) and PODE 1-2(DMM accounts for 60 wt%) After mixing, it enters the pre-reactor at a feed rate of 7 ml / min and 6 ml / min respectively; methanol is fed from a height of 0.5 m in the catalytic extraction reactor at a feed rate of 2 ml / min; cumene is used as the extractant and is fed from the bottom of the reactor at a feed rate of 37 ml / min; the reaction temperature of the pre-reactor is 60 ℃, the reaction temperature of the catalytic extraction reactor is 50 ℃, and the reaction pressure is 0.3 MPa.

[0105] The light phase discharge rate from the top of the reactor was 41.2 g / min, containing 1.8 wt% formaldehyde, 0.74 wt% methanol, 0.16 wt% water, 7.2 wt% DMM, 5.1 wt% PODE2, and PODE4. 3+ 7.5 wt%, the remainder being cumene and trace byproducts.

[0106] The bottom heavy phase discharge rate of the reactor is 4.9 g / min, which includes 2.8 wt% methanol, 0.01 wt% formaldehyde, 0.24 wt% cumene, and the remainder is water.

[0107] Example 3

[0108] The same pre-reactor, catalytic extraction reactor, and catalyst loading method as in Example 1 were used. The difference was that the pre-reactor was filled with 40 mL of Φ2×3-5 mm strip-shaped HZSM-5 molecular sieve catalyst (containing 20 wt% alumina binder, with a silica-alumina molecular ratio of 38), and the catalytic extraction reactor was filled with 160 mL of uniformly mixed Φ2×3-5 mm strip-shaped Hβ molecular sieve catalyst (containing 20 wt% alumina binder, with a silica-alumina molecular ratio of 60) and 200 mL of Φ3×3 mm stainless steel θ mesh rings.

[0109] A 30 wt% formaldehyde aqueous solution (diluted from a 38 wt% formaldehyde aqueous solution, containing 2.4 wt% methanol) and PODE 1-2 (DMM accounts for 55 wt%) After mixing, it enters the pre-reactor at feed rates of 8.3 ml / min and 5 ml / min respectively; methanol is fed from a height of 0.3 m in the catalytic extraction reactor at a feed rate of 2.4 ml / min; a mixture of toluene and ethylbenzene (weight ratio 1:1) is used as the extractant and fed from the bottom of the reactor at a feed rate of 37.2 ml / min; the reaction temperature of the pre-reactor is 110℃, the reaction temperature of the catalytic extraction reactor is 120℃, and the reaction pressure is 1.2 MPa.

[0110] The light phase discharge rate from the top of the reactor is 41.6 g / min, containing 2.2 wt% formaldehyde, 1 wt% methanol, 0.2 wt% water, 6.2 wt% DMM, 4.6 wt% PODE2, and PODE4. 3+ 6.7 wt%, the remainder being toluene, ethylbenzene and trace byproducts.

[0111] The bottom heavy phase discharge rate of the reactor is 6.7 g / min, which includes 2.6 wt% methanol, 0.01 wt% formaldehyde, 0.3 wt% toluene and ethylbenzene, and the remainder is water.

[0112] Example 4

[0113] The same pre-reactor, catalytic extraction reactor, catalyst, catalyst loading method, and loading amount as in Example 1 were used. The difference was that the outlet of the pre-reactor was connected to the light phase feed pipe of the catalytic extraction reactor.

[0114] Paraformaldehyde reagent was mixed with an appropriate amount of water and heated to dissolve, resulting in a formaldehyde aqueous solution with a formaldehyde content of 50 wt%. This solution was then combined with PODE. n (DMM accounts for 50 wt%, PODE2 accounts for 40 wt%, PODE 5+ The mixture (10 wt%) was fed into the pre-reactor at feed rates of 8.4 ml / min and 11.4 ml / min, respectively; methanol was fed from a height of 0.9 m at a feed rate of 3.9 ml / min; a mixture of 1,2-dichloroethane and 1,2-dichloropropane (weight ratio 1:1) was used as the extractant and fed from a heavy phase feed pipe at a height of 1.2 m at a feed rate of 12.4 ml / min; the reaction temperature in the pre-reactor was 55 °C, the reaction temperature in the catalytic extraction reactor was 40 °C, and the reaction pressure was 0.3 MPa.

[0115] The heavy phase discharge rate at the bottom of the reactor is 32 g / min, containing 5.8 wt% formaldehyde, 3.2 wt% methanol, 0.6 wt% water, 13.9 wt% DMM, 11.6 wt% PODE2, and PODE4. 3+ 18.2 wt%, trioxymethylene 0.2 wt%, the remainder being 1,2-dichloroethane and 1,2-dichloropropane and trace byproducts.

[0116] The light phase discharge rate at the top of the reactor is 5.4 g / min, which includes 1.6 wt% methanol, 0.01 wt% formaldehyde, 3 wt% 1,2-dichloroethane and 1,2-dichloropropane, and the remainder is water.

[0117] Example 5

[0118] The same pre-reactor, catalytic extraction reactor, catalyst, catalyst loading method and loading amount as in Example 1 were used.

[0119] Paraformaldehyde reagent was mixed with an appropriate amount of water and heated to dissolve, resulting in a formaldehyde aqueous solution with a formaldehyde content of 60 wt%. This solution was then combined with PODE. 1-2(DMM accounts for 50 wt%) After mixing, it enters the pre-reactor at feed rates of 10.4 ml / min and 8.4 ml / min respectively; methanol is fed from a height of 0.3 m at a feed rate of 5.7 ml / min; benzene is used as the extractant and is fed from the bottom of the reactor at a feed rate of 10 ml / min; the reaction temperature of the pre-reactor is 80℃, the reaction temperature of the catalytic extraction reactor is 60℃, and the reaction pressure is 0.5 MPa.

[0120] The light phase discharge rate from the top of the reactor is 26.5 g / min, containing 3.8 wt% formaldehyde, 3 wt% methanol, 0.1 wt% water, 13.6 wt% DMM, 13.1 wt% PODE2, and PODE4. 3+ 32.6 wt%, trioxymethylene 0.5 wt%, the remainder being benzene and trace byproducts.

[0121] The bottom heavy phase discharge rate of the reactor is 6.2 g / min, which contains 1.8 wt% methanol, 0.01 wt% formaldehyde, 0.1 wt% benzene, and the remainder is water.

[0122] Example 6

[0123] The same pre-reactor, catalytic extraction reactor, catalyst, catalyst loading method, and loading amount as in Example 1 were used. The difference was that the outlet of the pre-reactor was connected to the light phase feed pipe of the catalytic extraction reactor.

[0124] 38wt% formaldehyde aqueous solution (containing 3wt% methanol) and PODE 1-2 The mixture (60 wt% DMM) was fed into the pre-reactor at feed rates of 8.2 ml / min and 6 ml / min, respectively. Methanol was fed from a height of 0.9 m at a feed rate of 2.6 ml / min. A mixture of chlorobenzene and bromobenzene (weight ratio 9:1) was used as the extractant and fed from a heavy phase feed pipe at a height of 1.2 m at a feed rate of 30 ml / min. The reaction temperature in the pre-reactor was 80 °C, the reaction temperature in the catalytic extraction reactor was 80 °C, and the reaction pressure was 0.5 MPa.

[0125] The heavy phase discharge rate at the bottom of the reactor is 43.8 g / min, containing 2 wt% formaldehyde, 0.6 wt% methanol, 0.16 wt% water, 6.7 wt% DMM, 5.3 wt% PODE2, and PODE4. 3+ 8.2 wt%, the remainder being chlorobenzene, bromobenzene and trace byproducts.

[0126] The light phase discharge rate at the top of the reactor is 5.7 g / min, which includes 1.8 wt% methanol, 0.01 wt% formaldehyde, 1 wt% chlorobenzene and bromobenzene, and the remainder is water.

[0127] Example 7

[0128] The same pre-reactor, catalytic extraction reactor, and catalyst loading method as in Example 1 were used. The pre-reactor was also loaded with 40 mL of strongly acidic cation exchange resin catalyst. The difference was that the catalytic extraction reactor was loaded with 160 mL of uniformly mixed Φ2×3-5 mm strip-shaped HMCM-22 molecular sieve catalyst (containing 30 wt% alumina binder, and the silica-alumina molecular ratio of the molecular sieve was 28) and 200 mL of Φ3×3 mm stainless steel θ mesh rings.

[0129] 38wt% formaldehyde aqueous solution (containing 3wt% methanol) and PODE 1-2 The mixture (60 wt% DMM) was fed into the pre-reactor at feed rates of 6 ml / min and 8.5 ml / min, respectively. Methanol was fed from a height of 0.3 m at a feed rate of 2 ml / min. An alkane mixture (20 wt% each of n-hexane, n-heptane, isoheptane, n-octane, and isooctane) was used as the extractant and fed from the bottom of the reactor at a feed rate of 108 ml / min. The reaction temperature in the pre-reactor was 80 °C, and the reaction temperature in the catalytic extraction reactor was 120 °C. The reaction pressure was 1.2 MPa.

[0130] The light phase discharge rate from the top of the reactor is 84.4 g / min, containing 0.4 wt% formaldehyde, 0.3 wt% methanol, 0.1 wt% water, 5.1 wt% DMM, 3.5 wt% PODE2, and PODE4. 3+ 3.7 wt%, the remainder being a mixture of alkanes and trace byproducts.

[0131] The heavy phase discharge rate at the bottom of the reactor is 4.3 g / min, which includes 1.2 wt% methanol, 0.01 wt% formaldehyde, 0.1 wt% alkane mixture, and the remainder is water.

[0132] Example 8

[0133] The same pre-reactor, catalytic extraction reactor, catalyst, catalyst loading method and loading amount as in Example 1 were used.

[0134] 38wt% formaldehyde aqueous solution (containing 3wt% methanol) and PODE 1-2 The mixture (55 wt% DMM) was fed into the pre-reactor at feed rates of 7.4 ml / min and 6 ml / min, respectively. Methanol was fed from a height of 0.3 m into the catalytic extraction reactor at a feed rate of 2.4 ml / min. An aromatic mixture (40 wt% n-propylbenzene, 30 wt% ethylbenzene, and 30 wt% butadiene) was used as the extractant and fed from the bottom of the reactor at a feed rate of 37 ml / min. The reaction temperature in the pre-reactor was 60 °C, the reaction temperature in the catalytic extraction reactor was 50 °C, and the reaction pressure was 0.3 MPa.

[0135] The light phase discharge flow rate at the top of the reactor is 41.3 g / min, containing 1 wt% formaldehyde, 0.8 wt% methanol, 0.1 wt% water, 7.2 wt% DMM, 5.6 wt% PODE2, and PODE4. 3+ 9.3 wt%, the remainder being mixed aromatics and trace byproducts.

[0136] The bottom heavy phase discharge rate of the reactor is 5.4 g / min, which includes 1.8 wt% methanol, 0.01 wt% formaldehyde, 0.1 wt% mixed aromatics, and the remainder is water.

[0137] Example 9

[0138] The same pre-reactor, catalytic extraction reactor, catalyst, catalyst loading method and loading amount as in Example 1 were used.

[0139] Paraformaldehyde reagent is mixed with an appropriate amount of water and heated to dissolve, thus preparing a formaldehyde aqueous solution with a formaldehyde content of 80 wt% and PODE. 1-2 The mixture (50 wt% DMM) was fed into the pre-reactor at feed rates of 10.3 ml / min and 10.6 ml / min, respectively. Methanol was fed from a height of 0.3 m at a feed rate of 7.5 ml / min. A cycloalkane mixture (25 wt% each of cyclohexane, methylcyclopentane, methylcyclohexane, and ethylcyclohexane) was used as the extractant and fed from the bottom of the reactor at a feed rate of 14.5 ml / min. The reaction temperature in the pre-reactor was 80 °C, and the reaction temperature in the catalytic extraction reactor was 60 °C. The reaction pressure was 0.5 MPa.

[0140] The light phase discharge rate from the top of the reactor is 36 g / min, containing 0.8 wt% formaldehyde, 0.9 wt% methanol, 0.1 wt% water, 13.1 wt% DMM, 12 wt% PODE2, and PODE4. 3+ 37.3 wt%, trioxymethylene 0.3 wt%, the remainder being cycloalkanes and trace byproducts.

[0141] The heavy phase discharge rate at the bottom of the reactor is 4.5 g / min, which includes 1.5 wt% methanol, 0.01 wt% formaldehyde, 0.06 wt% cycloalkanes, and the remainder is water.

[0142] Example 10

[0143] A Φ2×2mm stainless steel θ mesh ring is filled into a glass tube with an inner diameter of 15mm and a height of 1.2m to serve as an extraction tower. The filling height is 1 meter, with 10cm of empty pipe left at the top and bottom. Heavy phase and light phase feed ports are set at the top and bottom ends of the θ mesh ring bed, respectively, and light phase and heavy phase discharge ports are set at the top and bottom ends of the glass tube, respectively.

[0144] The extract obtained in Example 2 (composition: formaldehyde 1.8 wt%, methanol 0.74 wt%, water 0.16 wt%, DMM 7.2 wt%, PODE2 5.1 wt%, PODE) was used. 3+ 7.5 wt%, the remainder being cumene and trace byproducts) are fed from the light phase inlet at a rate of 15 ml / min; water (heavy phase) is fed from the heavy phase inlet as the back-extraction agent at a rate of 0.6 ml / min; the back-extraction temperature is 26℃ and the operating pressure is atmospheric pressure.

[0145] The top light phase (organic phase) discharge rate of the back-extraction tower is 12.7 g / min, containing formaldehyde <0.005 wt%, methanol <0.005 wt%, water 0.5 wt%, DMM 7.2 wt%, PODE2 5.1 wt%, and PODE... 3+ 7.6 wt%, the remainder being cumene and trace byproducts.

[0146] The bottom heavy phase (aqueous phase) discharge rate of the back-extraction tower is 0.9 g / min, containing 10.6 wt% methanol, 25.7 wt% formaldehyde, 2.3 wt% DMM, 1.6 wt% PODE2, and PODE4. 3+ 1.4 wt%, 0.3 wt% cumene, the remainder being water.

[0147] Example 11

[0148] The same back-extraction experimental apparatus as in Example 10 was used.

[0149] The extract obtained in Example 4 (composition: formaldehyde 5.8 wt%, methanol 3.2 wt%, water 0.6 wt%, DMM 13.9 wt%, PODE2 11.6 wt%, PODE) was used. 3+ 18.2 wt% of trioxymethylene (0.2 wt%), with the remainder being 1,2-dichloroethane, 1,2-dichloropropane, and trace byproducts, were fed from the heavy phase inlet at a rate of 15 ml / min; methanol (light phase) was fed from the light phase inlet as the back-extraction agent at a rate of 4.4 ml / min; the back-extraction temperature was 26 °C, and the operating pressure was atmospheric pressure.

[0150] The bottom heavy phase discharge rate of the back-extraction tower is 17.6 g / min, containing formaldehyde <0.005 wt%, water <0.005 wt%, methanol 12.2 wt%, DMM 13.1 wt%, PODE2 11 wt%, and PODE... 3+ 17.5 wt%, trioxymethylene 0.19 wt%, the remainder being 1,2-dichloroethane and 1,2-dichloropropane and trace byproducts.

[0151] The light phase discharge rate from the top of the stripping tower is 3.2 g / min, containing 3.3 wt% water, 31.4 wt% formaldehyde, 3.4 wt% DMM, 2.3 wt% PODE2, and PODE4. 3+ 2.6 wt%, trioxymethylene 0.06 wt%, 1,2-dichloroethane and 1,2-dichloropropane 2.8 wt%, the remainder being methanol.

[0152] Comparative Example 1

[0153] A stainless steel catalytic extraction reactor with an inner diameter of 20 mm and a height of 1.3 m is filled with 160 ml of uniformly mixed strong acid cation exchange resin catalyst and 200 ml of Φ3×3 mm stainless steel θ mesh rings, with a filling height of 1.2 m, leaving an empty tube 10 cm above. A heavy phase feed pipe is installed at the top of the reactor, at the top of the catalyst and θ mesh ring bed. A light phase discharge pipe is installed at the top of the reactor and connected to a back pressure valve to control the reaction pressure. A light phase feed pipe is installed at the bottom of the reactor. A temperature- and pressure-resistant glass tube is connected to the bottom of the reactor for observing the two-phase stratification and is also connected to the heavy phase discharge pipe.

[0154] Without a pre-reactor, a 38wt% formaldehyde aqueous solution (containing 3wt% methanol) is fed into the catalytic extraction reactor from a heavy phase feed pipe at a height of 1.2m, at a feed rate of 10.7ml / min; PODE 1-2 (DMM accounts for 60 wt%) is fed from a height of 0.9 m in the catalytic extraction reactor at a feed rate of 8.2 ml / min; methanol is fed from a height of 0.3 m in the catalytic extraction reactor at a feed rate of 2.6 ml / min; mixed xylene is used as the extractant and is fed from the bottom of the reactor at a feed rate of 62 ml / min; the reaction temperature is 60℃ and the reaction pressure is 0.3 MPa.

[0155] The light phase discharge rate from the top of the reactor is 67.6 g / min, containing 3.2 wt% formaldehyde, 0.8 wt% methanol, 0.2 wt% water, 6.2 wt% DMM, 4.2 wt% PODE2, and PODE4. 3+ 4.8 wt%, the remainder being mixed xylenes and trace byproducts.

[0156] The bottom heavy phase discharge rate of the reactor is 7.8 g / min, which includes 3.1 wt% methanol, 0.03 wt% formaldehyde, 0.4 wt% mixed xylene, and the remainder is water.

[0157] Comparing Comparative Example 1 with Example 1, it is shown that without a pre-reactor, under otherwise similar conditions, the concentration of PODE in the extract phase material is significantly reduced, and the concentration of PODE in the extract phase material is also reduced. 3+ The proportion has decreased significantly.

[0158] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing polymethoxydimethyl ether from methanol and formaldehyde aqueous solution, characterized in that, Includes the following steps: a) Material A containing formaldehyde and material B containing polyoxymethylene dimethyl ether in a recycling reaction are introduced into a pre-reactor for pre-reaction to obtain pre-reacted material I; b) Introduce the pre-reacted material I obtained in step a) and the methanol-containing material C into a catalytic extraction tower or a multi-stage catalytic extraction reactor, and contact them countercurrently with the extractant to carry out catalytic reaction and extraction, so as to obtain the extract phase material II and the raffinate phase material III. The methanol-containing material C is fed from the middle of the catalytic extraction tower or from an intermediate stage of a multi-stage catalytic extraction reactor.

2. A method for preparing polymethoxydimethyl ether from methanol and formaldehyde aqueous solution, characterized in that, A catalyst bed and a separation component are alternately arranged in a catalytic extraction column, the separation component including a separation tray and / or packing; Material A containing formaldehyde and material B containing polyoxymethylene dimethyl ether in a circulating reaction are introduced together into a catalytic extraction tower. They first enter one of the catalyst beds for catalytic reaction, and then are extracted by countercurrent contact with the extractant. The catalytic reaction and extraction processes are carried out alternately to obtain extract phase material II and raffinate phase material III. Material C, containing methanol, is fed from the middle of the catalytic extraction tower.

3. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The polyoxymethylene dimethyl ether in material B containing the polyoxymethylene dimethyl ether of the cyclic reaction comes from the separator of the extraction phase material II and / or freshly added polyoxymethylene dimethyl ether.

4. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The weight ratio of the feed amount of the extractant to the feed amount of (material A containing formaldehyde + material C containing methanol) is 0.3 to 12:

1.

5. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The extractant is selected from at least one of halogenated hydrocarbons, aromatic hydrocarbons, alkanes, and cycloalkanes.

6. The method for preparing polymethoxydimethyl ether according to claim 5, characterized in that, The halogenated hydrocarbon is selected from at least one of dichloroethane, dichloropropane, chlorobenzene, and bromobenzene.

7. The method for preparing polymethoxydimethyl ether according to claim 5, characterized in that, The aromatic hydrocarbon is selected from at least one of benzene, toluene, ethylbenzene, xylene, n-propylbenzene, isopropylbenzene, methyl ethylbenzene, and butylbenzene.

8. The method for preparing polymethoxydimethyl ether according to claim 5, characterized in that, The alkane is selected from at least one of the following: n-alkanes having 5-10 carbon atoms and isoalkanes having 5-10 carbon atoms.

9. The method for preparing polymethoxydimethyl ether according to claim 5, characterized in that, The cycloalkane is selected from at least one of cyclohexane, methylcyclopentane, methylcyclohexane, and ethylcyclohexane.

10. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The extractant is xylene.

11. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The extractant is cumene.

12. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The extractant is a mixture of toluene and ethylbenzene.

13. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The extractant is a mixture of 1,2-dichloroethane and 1,2-dichloropropane.

14. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The extractant is benzene.

15. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The extractant is a mixture of chlorobenzene and bromobenzene.

16. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The extractant is a mixture of n-hexane, n-heptane, isoheptane, n-octane, and isooctane.

17. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The extractant is a mixture of n-propylbenzene, ethylbenzene, and butylbenzene.

18. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The extractant is a mixture of cyclohexane, methylcyclopentane, methylcyclohexane, and ethylcyclohexane.

19. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The catalyst for the catalytic reaction is selected from at least one of solid acid catalysts.

20. The method for preparing polymethoxydimethyl ether according to claim 19, characterized in that, The solid acid catalyst is selected from strong acid cation exchange resins and / or hydrogen-type molecular sieve catalysts.

21. The method for preparing polymethoxydimethyl ether according to claim 20, characterized in that, The hydrogen-type molecular sieve catalyst contains HZSM-5 molecular sieve and / or Hβ molecular sieve.

22. The method for preparing polymethoxydimethyl ether according to claim 1, characterized in that, The reaction temperature of the pre-reactor is 40–140℃.

23. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, The reaction temperature in the catalytic extraction tower or multi-stage catalytic extraction reactor is 40–140℃.

24. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, Formaldehyde is back-extracted from extraction phase II using water or methanol to obtain an aqueous solution or a methanol solution containing formaldehyde; the aqueous solution or methanol solution containing formaldehyde is then returned to the catalytic extraction tower or multi-stage catalytic extraction reactor for further reaction.

25. The method for preparing polymethoxydimethyl ether according to claim 1 or 2, characterized in that, At least a portion of the extractant-free material II is returned as reflux to the catalytic extraction tower or multi-stage catalytic extraction reactor.

Images