CN109651100B - Process for synthesizing polyformaldehyde dimethyl ether from methanol - Google Patents
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- CN109651100B CN109651100B CN201710940874.9A CN201710940874A CN109651100B CN 109651100 B CN109651100 B CN 109651100B CN 201710940874 A CN201710940874 A CN 201710940874A CN 109651100 B CN109651100 B CN 109651100B
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
- C07C41/48—Preparation of compounds having groups
- C07C41/50—Preparation of compounds having groups by reactions producing groups
- C07C41/56—Preparation of compounds having groups by reactions producing groups by condensation of aldehydes, paraformaldehyde, or ketones
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
- B01J31/06—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing polymers
- B01J31/08—Ion-exchange resins
- B01J31/10—Ion-exchange resins sulfonated
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/30—Ion-exchange
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
- B01J2231/40—Substitution reactions at carbon centres, e.g. C-C or C-X, i.e. carbon-hetero atom, cross-coupling, C-H activation or ring-opening reactions
- B01J2231/42—Catalytic cross-coupling, i.e. connection of previously not connected C-atoms or C- and X-atoms without rearrangement
- B01J2231/4277—C-X Cross-coupling, e.g. nucleophilic aromatic amination, alkoxylation or analogues
- B01J2231/4288—C-X Cross-coupling, e.g. nucleophilic aromatic amination, alkoxylation or analogues using O nucleophiles, e.g. alcohols, carboxylates, esters
Abstract
The invention relates to a process method for synthesizing polyformaldehyde dimethyl ether, which solves the problem of high synthesis cost and low yield of the polyformaldehyde dimethyl ether; the reaction zone comprises a methanol storage tank, a preheater, a fixed bed reactor and a bubbling reactor; the reaction zone comprises the steps that methanol is preheated and vaporized to be mixed with air and then enters a fixed bed reactor, formaldehyde is generated through catalytic oxidation of a formaldehyde synthesis catalyst and enters a bubbling reactor, and the mixture, the methanol and the recycled mixture in the bubbling reactor are catalyzed by a solid acid catalyst to generate polyoxymethylene dimethyl ether; the separation zone comprises an anion exchange resin bed layer, a rectification module and a product storage tank; the separation zone comprises the technical scheme that the discharge of the bubbling reactor is deacidified by anion exchange resin and then enters a rectification module for separation, the tri-polymer and the tetramer of the polyformaldehyde dimethyl ether enter a product storage tank, and other components circulate to the bubbling reactor, and the separation zone is used for producing the polyformaldehyde dimethyl ether.
Description
Technical Field
The invention relates to a process method for synthesizing polyformaldehyde dimethyl ether from methanol.
Background
In recent years, low carbon has become a social topic and has gained increasing attention. For example, how to reduce the high pollution exhaust gas emissions from the increasingly vigorous automobile manufacturing industry and improve the use efficiency of fuel oil has become the subject of many institutional studies.
It is now generally accepted that oxygenates are well suited as diesel blending components. Many companies and research institutes are currently investing in the search and screening of suitable oxygenates, including: acetals, alcohols, carbonates, esters, ethers, glycol derivatives, and the like. For diesel fuel, the oxygenate needs to have a high cetane number, a low auto-ignition point, and a fast ignition. In addition, the diesel oil has good miscibility with common diesel oil, low water resistance, easy biodegradation, low production cost, cheap and easily available raw materials and the like, and particularly, the toxicity problem is more concerned. Several promising diesel oxygenates have been developed by many companies in the industry in recent years, and have been used for blending and automotive evaluation, such as: dimethyl carbonate, dimethoxymethane, polyoxymethylene dimethyl ether, di-n-amyl ether, glycol ethers (glyme), and the like. The polyoxymethylene dimethyl ether is widely concerned as a diesel additive due to the excellent performance of the polyoxymethylene dimethyl ether.
Polyoxymethylene dimethyl ethers (PODE) is a generic term for a class of substances, and can be represented by the general formula CH3O(CH2O)nCH3Having a higher cetane number (>40) And oxygen content (42-51%). When the value of n is 1, the polyformaldehyde dimethyl ether is methylal, and the methylal serving as the vehicle fuel additive component can improve the energy utilization efficiency and reduce the exhaust emission, but is still easy to cause air lock. When the value of n is 2-6, the physical property and the combustion performance of the additive are very close to those of diesel oil, and the defects of the conventional additive serving as a blending component of the diesel oil for vehicles are well overcome. Therefore, the polyoxymethylene dimethyl ether can be used as a novel clean diesel component, the addition amount in the diesel can reach more than 10 percent (v/v), the combustion condition of the diesel in an engine can be improved, the thermal efficiency is improved, and particulate matters and CO in tail gas are reducedxAnd NOxAnd (4) discharging. The optimal chain length of the polyoxymethylene dimethyl ethers mixed with diesel oil is n =3, 4. When n =2, the flash point of polyoxymethylene dimethyl ether is too low, and when n is too large, polyoxymethylene dimethyl ether may precipitate and clog at a low temperature. Reportedly, 5-30% CH is added3OCH2OCH3Can greatly reduce NOxAnd (5) discharging.
The middle of PODE is paraformaldehyde segment, and two ends are sealed by methyl. PODE is generally synthesized from a compound which provides paraformaldehyde (formaldehyde, trioxane, paraformaldehyde, etc.) and a compound which provides a blocked methyl group (methanol, dimethyl ether, methylal, etc.). PODE can be synthesized by dehydrating methanol and formaldehyde or paraformaldehyde and trioxymethylene under the catalysis of acid. The production of synthesis gas from coal gasification, methanol from synthesis gas, formaldehyde from methanol oxidation, and paraformaldehyde or trioxymethylene from formaldehyde have long been industrialized. The PODE synthesized by the coal-based methanol can replace part of diesel oil, improve the combustion efficiency of the diesel oil, reduce the harm of the combustion of the diesel oil to the environment, and has important strategic significance and good economic value. The resource pattern of China has the characteristics of rich coal, less oil and gas, and the development and synthesis of PODE can convert rich coal resources of China into liquid alternative fuels, reduce the import dependence of China on petroleum and further have great significance on national energy safety.
Polyoxymethylene dimethyl ethers in laboratories can be prepared by heating paraformaldehyde with low polymerization degree or reacting paraformaldehyde with methanol at 150-180 ℃ in the presence of trace amounts of sulfuric acid or hydrochloric acid. Since polyoxymethylene dimethyl ethers have great application values in the field of diesel additives, a large number of companies and research institutes have been researching feasible industrial production technologies for a long time.
EP2228359A1 describes a process for preparing polyoxymethylene dimethyl ethers from methanol as starting material. The method uses a molecular sieve modified by ammonium molybdate and ferric nitrate as a catalyst, and methanol and air (oxygen) are oxidized in one step at the temperature of more than 200 ℃ to obtain the polyoxymethylene dimethyl ether. The method has relatively low production cost, but the preparation process of the catalyst is complex, and the selectivity of the polyoxymethylene dimethyl ether is not ideal.
EP1070755 describes a process for preparing polyoxymethylene dimethyl ethers having 2 to 6 formaldehyde units per molecule by reacting methylal with paraformaldehyde in the presence of trifluorosulfonic acid. WO2006/045506A1 describes that a series of products with n = 1-10 are obtained by BASF company by using sulfuric acid and trifluoromethanesulfonic acid as catalysts and methylal, paraformaldehyde and trioxymethylene as raw materials. The above methods all adopt protonic acid as a catalyst, which is cheap and easy to obtain, but has the defects of strong corrosivity, difficult separation, large environmental pollution and high requirement on equipment.
US6160174 and US6265528 describe that the BP company obtains polyoxymethylene dimethyl ether by a gas-solid reaction using methanol, formaldehyde, dimethyl ether and methylal as raw materials and cation exchange resin as a catalyst. However, this method has the advantages of easy separation of catalyst, easy circulation, low conversion rate, low yield and complex process.
CN 200910056819.9 takes methanol and trioxymethylene as raw materials and takes solid superacid as a catalyst to catalyze and synthesize polyoxymethylene dimethyl ether, although a good raw material conversion rate is obtained, due to the strong acidity of the solid superacid and the irregular pore structure, the selectivity of a byproduct methylal in a product is 20-50%, the flash point of a diesel oil mixture is reduced due to the large amount of methylal, the quality of the diesel oil mixture is damaged, and the product is not suitable for being used as an additive of diesel oil. CN 101048357A introduces a synthesis process for synthesizing polyoxymethylene dimethyl ethers by taking methylal and trioxymethylene as raw materials. We also developed a solid acid catalyst (molecular sieve CN 200910056820.1, solid super acid CN 200910056819.9) to prepare polyoxymethylene dimethyl ether from methanol and trioxymethylene.
CN 101182367A discloses a process method for synthesizing trioxymethylene from formaldehyde and then synthesizing polyoxymethylene dimethyl ether from trioxymethylene and methanol by using acidic ionic liquid as a catalyst. Although the method has high one-way yield, the used ionic liquid catalyst is expensive and difficult to separate, and the operation difficulty is higher. US5,959,156 describes a process for the synthesis of polyoxymethylene dimethyl ethers starting from dimethyl ether and methanol using a novel heterogeneous promoted condensation catalyst. Although the process is low in cost, the product yield is not ideal.
However, the reaction raw materials adopted by the processes comprise methanol, dimethyl ether, methylal, trioxymethylene and the like. According to market research, the market price of the methanol is the lowest, namely 3000 yuan/ton, and people can easily find that the production cost can be greatly reduced and higher selectivity and yield can be obtained by only using the methanol as the raw material to produce the polyoxymethylene dimethyl ether by reasonably optimizing the production process.
Disclosure of Invention
The invention aims to solve the technical problem of high product cost and low yield of the polyformaldehyde dimethyl ether synthesis process, and provides a novel process method for synthesizing polyformaldehyde dimethyl ether, which has the characteristics of low product cost and high yield.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the technological process of synthesizing polyoxymethylene dimethyl ether from methanol includes reaction zone and separation zone; the reaction zone comprises a methanol storage tank, a preheater, a fixed bed reactor and a bubbling reactor; the process steps of the reaction zone are that methanol is preheated and vaporized to be mixed with air and then enters a fixed bed reactor, formaldehyde is generated through catalytic oxidation of a formaldehyde synthesis catalyst and enters a bubbling reactor, and the mixture, the methanol and the recycled mixture are catalyzed by a solid acid catalyst in the bubbling reactor to generate polyoxymethylene dimethyl ether; the separation zone comprises an anion exchange resin bed layer, a rectification module and a product storage tank; the separation zone comprises the steps that the discharge of the bubbling reactor enters a rectification module for separation after being deacidified by anion exchange resin, the tri-polymer and the tetramer of the polyformaldehyde dimethyl ether enter a product storage tank, and other components circulate to the bubbling reactor.
In the technical scheme, the reaction temperature in the fixed bed reactor is preferably 280-700 ℃, and the air volume space velocity in the fixed bed reactor is preferably 4000-8000 h-1. The reaction pressure in the fixed bed reactor is preferably 0.01-30 MPa. The mass ratio of methanol to formaldehyde in the feed of the bubbling reactor is preferably 0.02-50: 1. The reaction temperature in the bubbling reactor is preferably 80-240 ℃. The reaction pressure in the bubbling reactor is preferably 0.01 to 15.0 MPa, and more preferably 0 to 10 MPa.
In the above technical solution, the mixture preferably comprises a first fraction containing methylal, a third fraction containing polyoxymethylene dimethyl ether dimers, and a fifth fraction containing polyoxymethylene dimethyl ether having a higher degree of polymerization (n >4), which are separated by the rectification module; the rectification module also preferably separates a second fraction containing methanol and a fourth fraction containing tri-and tetramers of polyoxymethylene dimethyl ether.
In the technical scheme, the reaction discharge material of the bubble reactor preferably enters the rectification module after being deacidified by the anion exchange resin bed layer. The rectification module preferably consists of 4 rectification columns. The first fraction is preferably taken off at the top of the first rectification column, the second fraction is preferably taken off at the top of the second rectification column, the third fraction is preferably taken off at the top of the third rectification column, the fourth fraction is preferably taken off at the top of the fourth rectification column, and the fifth fraction is preferably taken off at the bottom of the fourth rectification column. The first, third, and fifth fractions are preferably recycled to the liquid phase tank reactor after being dewatered by a dehydrator. The second fraction is preferably recycled to the methanol storage tank after being dewatered by a dehydrator.
The operating pressure of the first rectifying tower is preferably 0.2-2 MPa, the operating pressure of the second rectifying tower is preferably 0.1-1.5 MPa, the operating pressure of the third rectifying tower is preferably 0.05-1.2MPa, and the operating pressure of the fourth rectifying tower is preferably 0.001-0.6 MPa. The theoretical plate number of the first rectifying tower is preferably 15-40, the theoretical plate number of the second rectifying tower is preferably 15-30, the theoretical plate number of the third rectifying tower is preferably 15-35, and the theoretical plate number of the fourth rectifying tower is preferably 15-35.
The formaldehyde synthesis catalyst in the above technical scheme preferably comprises one or more of the following components: molybdenum oxide, iron oxide, silicon oxide, aluminum oxide and metallic silver.
In the above technical scheme, the solid acid catalyst is selected from one or more of the following catalysts: sulfonic acid type polystyrene cation exchange resin, metal modified sulfonic acid type polystyrene cation exchange resin, molecular sieve, dinitrobenzoic acid, ethylene diamine tetraacetic acid, alumina, titanium dioxide, more preferably metal modified sulfonic acid type polystyrene cation exchange resin.
In the technical scheme, the sulfonic acid type polystyrene cation exchange resin comprises a crosslinked polystyrene skeleton and sulfonic acid groups; the modifying metal includes Cu.
In the above technical solution, preferably, the modified metal further includes an auxiliary metal selected from Mn, Cu and an auxiliary metal having a synergistic effect in improving selectivity to PODE with n =2 to 10. The ratio between Cu and the auxiliary metal is not particularly limited as long as Cu and the auxiliary metal are simultaneously present in the catalyst to achieve a comparable synergistic effect.
The mass ratio of Cu to the auxiliary metal is, by way of non-limiting example, 0.01 to 100, and further non-limiting examples within this range include 0.1, 0.5, 0.8, 1, 1.5, 2, 3,4, 5,6, 7, 8, 9, 10, and the like.
In the above-mentioned technical solution, the content of the modified metal in the catalyst is not particularly limited, but is not limited to, for example, more than 0 and not more than 10 w%.
In the technical scheme, the total exchange capacity of the resin is 3.0-6.0 mmol/g.
In the above technical solution, the resin may be of a gel type or a macroporous type.
In order to solve the second technical problem, the technical scheme of the invention is as follows:
in the above technical solution, the preparation method of the catalyst comprises contacting the sulfonic acid type polystyrene cation exchange resin with a suspension containing the modified metal oxide and/or hydroxide in the presence of a catalytic amount of acid to perform ion exchange.
In the above technical scheme, the acid is not particularly limited as long as the salt obtained by the reaction with the modified metal oxide and/or hydroxide can be dissolved in the solvent used for the suspension, and the acid is, for example, but not limited to, at least one of hydrochloric acid, nitric acid, and C2-C10 carboxylic acid.
In the above technical scheme, the carboxylic acid may be a hydroxy-substituted carboxylic acid, such as but not limited to glycolic acid, lactic acid, tartaric acid, citric acid, and the like.
In the above technical scheme, the carboxylic acid may be a C2-C10 monobasic acid, such as but not limited to acetic acid and the like.
In the above technical solution, the drying agent used in the drying tube and the dehydrator is preferably selected from at least one of the following drying agents: ion exchange resin, molecular sieve and silica gel.
In the above technical scheme, the rectifying tower is preferably a packed tower, and the packing is preferably stainless steel or ceramic with a regular structure.
The invention has the following advantages: firstly, the yield and the selectivity are high, and the sum of n =3 and n =4 products accounts for the sum of n = 2-5 products; secondly, the production cost is low; thirdly, recycling the by-products by adopting a rectification method; and a better technical effect is achieved.
Drawings
The invention will be described in further detail with reference to fig. 1.
Methanol (material flow 2) output from the methanol storage tank 1 is heated and vaporized by a heater 3,4 and air (material flow 29) are mixed and then enter a fixed bed reactor 5, formaldehyde is prepared by catalytic oxidation in the fixed bed reactor 5, a discharge material flow 6 (mainly formaldehyde and methanol) of the reactor 5 is fed into a bubbling reactor 7, a material flow 8 (mainly liquid-phase alcohol) output from the methanol storage tank 1 is also fed into the bubbling reactor 7, and a material flow 16 (mainly dimer of polyoxymethylene dimethyl ether and polyoxymethylene dimethyl ether with higher polymerization degree (n > 4)) output from a dehydrator 15 after water removal. The material 9 discharged from the bubble reactor 7 is deacidified by an anion exchange resin bed layer 10 to obtain a material flow 11, and the material flow 11 enters a rectifying tower 12 for separation. Unreacted methylal is discharged from the top of the rectifying tower 12 (stream 14), and is subjected to water removal by a water remover 15 and then is introduced into the bubble reactor 7 again by a water removal device 16. The bottom discharge 13 of the rectifying tower 12 enters a rectifying tower 17 for next separation. Unreacted methanol is discharged from the top of the rectifying tower 17 (material flow 19), and is subjected to water removal by a water remover 20 and then is introduced into the methanol storage tank 1 again at 21. The bottom discharge (stream 18) of the rectification column 17 enters a rectification column 22 for further separation. Discharging 24 the dimer of the polyoxymethylene dimethyl ether from the top of the rectifying tower 22, removing water by a dehydrator 15, and then introducing into the bubbling reactor 7 again. The bottom discharge 23 of the rectification column 22 enters a rectification column 25. The trimer and tetramer of polyoxymethylene dimethyl ether are discharged from the top of the rectifying tower 25 (stream 27) and enter a product storage tank 28. Polyoxymethylene dimethyl ether with higher polymerization degree (n is more than 4) is discharged from the bottom of the rectifying tower 25 (material flow 26), is dehydrated by a dehydrator 15 and then is introduced into the bubbling reactor 7 again.
The invention is further illustrated by the following examples.
Detailed Description
[ example 1 ]
1. Preparation of the catalyst
Washing the sodium sulfonate type polystyrene cation exchange resin 7320 with deionized water until clear water flows out, soaking for four times with 4w% hydrochloric acid, soaking for 4h each time with 4w% hydrochloric acid which is 10 times of the dry weight of the sodium sulfonate type polystyrene cation exchange resin 7320, washing with deionized water until the eluate has no chloride ions, and drying at 60 ℃ to obtain the sulfonic type polystyrene cation exchange resin with the full exchange capacity of 4.10 mmol/g. 98 g of sulfonic acid type polystyrene cation exchange resin corresponding to the dry resin was taken in combination with 300ml of Cu (OH) containing 2 g of Cu2Mixing the water suspension, adding 1 drop of glacial acetic acid, mixing, standing at room temperature for 24 hours, and drying in a vacuum drying oven to constant weight to obtain the catalyst with the Cu content of 2 w%.
2. Synthesis of polyformaldehyde dimethyl ether
150g of silver-silicon-aluminum catalyst (consisting of silver, silicon oxide and aluminum oxide according to the mass fraction ratio of 18:75: 7) is filled in the fixed bed reactor 5, 150g of solid acid catalyst is filled in the bubbling reactor 7, a nitrogen purging device is used, liquid-phase methanol is heated and vaporized and mixed with air to be fed into the fixed bed reactor, and the air volume space velocity is 4500h-1The methanol feeding speed is 93.75g/h, the operating temperature of the fixed bed reactor is 600 ℃, and the pressure is 1 MPa; simultaneously, a mixed solution of the recycled anhydrous methanol and the polyoxymethylene dimethyl ethers (n =1,2,5, 6) is added into the bubbling reactor 9, and the feeding speeds are respectively 62.5g/h and 109 g/h. The operating conditions of the bubble reactor 7 were a reaction temperature of 150 ℃ and a reaction pressure of 3.0 MPa. The reaction discharge enters an anion exchange resin bed layer.
The discharged material 9 of the bubbling reactor 7 enters a rectifying tower 12 for separation after being deacidified by an anion exchange resin bed 10, the operating pressure is 0.2-2 MPa, and the theoretical plate number is 20. Unreacted methylal is discharged from the top of the rectifying tower 12 (material flow 14), and is introduced into the bubbling reactor 7 again after being dewatered by a dehydrator 15. And the bottom material discharged from the rectifying tower 12 enters a rectifying tower 17 for next separation, the operating pressure is 0.1-1.5 MPa, and the theoretical plate number is 20. Unreacted methanol is discharged from the top of the rectifying tower 17 (material flow 19), and is subjected to water removal by a water remover 15 and then is introduced into the methanol storage tank 1 again. The bottom material (material flow 18) of the rectifying tower 17 enters a rectifying tower 22 for next separation, the operation pressure is 0.05-1.2MPa, and the theoretical plate number is 20. Discharging the dimer of the polyoxymethylene dimethyl ether from the top of the rectifying tower 22, removing water by a dehydrator 15, and introducing into the bubbling reactor 7 again. Discharging the trimer and the tetramer of the polyformaldehyde dimethyl ether (material flow 27) from the top of the rectifying tower 25 at the operating pressure of 0.001-0.6MPa and the theoretical plate number of 20, and feeding the trimer and the tetramer into a product storage tank 28. Polyoxymethylene dimethyl ether with higher polymerization degree (n is more than 4) is discharged from the bottom of the rectifying tower 25 (material flow 26), is dehydrated by a dehydrator 15 and then is introduced into the bubbling reactor 7 again. The reaction was continued for 80h and the product was sampled on-line and analyzed by gas chromatography and the results are given in Table 1.
[ example 2 ]
1. Preparation of the catalyst
Washing the sodium sulfonate type polystyrene cation exchange resin 7320 with deionized water until clear water flows out, soaking for four times with 4w% hydrochloric acid, soaking for 4h each time with 4w% hydrochloric acid which is 10 times of the dry weight of the sodium sulfonate type polystyrene cation exchange resin 7320, washing with deionized water until the eluate has no chloride ions, and drying at 60 ℃ to obtain the sulfonic type polystyrene cation exchange resin with the full exchange capacity of 4.10 mmol/g. 98 g of sulfonic acid type polystyrene cation exchange resin corresponding to the dry resin was taken in combination with 300ml of Cu (OH) containing 2 g of Cu2Mixing the water suspension, adding 1 drop of glacial acetic acid, mixing, standing at room temperature for 24 hours, and drying in a vacuum drying oven to constant weight to obtain the catalyst with the Cu content of 2 w%.
2. Synthesis of polyformaldehyde dimethyl ether
150g of ferromolybdenum catalyst (consisting of molybdenum oxide and iron oxide in a molar ratio of 2: 1) is filled in a fixed bed reactor 5, 150g of solid acid catalyst is filled in a bubbling reactor 7, a nitrogen purging device is used, liquid-phase methanol is heated, vaporized and mixed with air and then fed into the fixed bed reactor, and the air volume space velocity is 4500h-1The methanol feeding speed is 93.75g/h, the operating temperature of the fixed bed reactor is 380 ℃, and the pressure is 1 MPa; simultaneously, the recycled anhydrous methanol and the polyformaldehyde are added into the bubbling reactor 9The feed rates of the mixed liquid of dimethyl ether (n =1,2,5, 6) were 93.75g/h and 85.5g/h, respectively. The operating conditions of the bubble reactor 7 were a reaction temperature of 110 ℃ and a reaction pressure of 1.0 MPa. The reaction discharge enters an anion exchange resin bed layer.
Otherwise, the reaction was continued for 80 hours as in example 1, and the product was sampled on-line and analyzed by gas chromatography, and the results of the experiment are shown in Table 1.
[ example 3 ]
1. Preparation of the catalyst
Washing the sodium sulfonate type polystyrene cation exchange resin 7320 with deionized water until clear water flows out, soaking for four times with 4w% hydrochloric acid, soaking for 4h each time with 4w% hydrochloric acid which is 10 times of the dry weight of the sodium sulfonate type polystyrene cation exchange resin 7320, washing with deionized water until the eluate has no chloride ions, and drying at 60 ℃ to obtain the sulfonic type polystyrene cation exchange resin with the full exchange capacity of 4.10 mmol/g. 98 g of sulfonic acid polystyrene cation exchange resin corresponding to the dry resin was mixed with 300ml of Mn (OH) 2 g of Mn under nitrogen protection2Mixing the water suspension, adding 1 drop of glacial acetic acid, mixing, standing at room temperature for 24 hours, and drying in a vacuum drying oven to constant weight to obtain the catalyst with the Mn content of 2 w%.
2. Synthesis of polyformaldehyde dimethyl ether
Otherwise, the reaction was continued for 80 hours as in example 1, and the product was sampled on-line and analyzed by gas chromatography, and the results of the experiment are shown in Table 1.
[ example 4 ]
1. Preparation of the catalyst
Washing the sodium sulfonate type polystyrene cation exchange resin 7320 with deionized water until clear water flows out, soaking for four times with 4w% hydrochloric acid, soaking for 4h each time with 4w% hydrochloric acid which is 10 times of the dry weight of the sodium sulfonate type polystyrene cation exchange resin 7320, washing with deionized water until the eluate has no chloride ions, and drying at 60 ℃ to obtain the sulfonic type polystyrene cation exchange resin with the full exchange capacity of 4.10 mmol/g. A sulfonic acid type polystyrene cation exchange resin equivalent to 98 g of a dry resin was taken,under nitrogen protection with 300ml of Cu (OH) containing 1 g of Cu and 1 g of Mn2And Mn (OH)2Mixing the mixed aqueous suspension, adding 1 drop of glacial acetic acid, mixing, standing at room temperature for 24 hours, and drying in a vacuum drying oven to constant weight to obtain the catalyst with the Cu content of 1w% and the Mn content of 1 w%.
2. Synthesis of polyformaldehyde dimethyl ether
Otherwise, the reaction was continued for 80 hours as in example 1, and the product was sampled on-line and analyzed by gas chromatography, and the results of the experiment are shown in Table 1.
TABLE 1
n is polymerization degree, and the product is CH3O(CH2O)nCH3。
Claims (13)
1. The technological process of synthesizing polyoxymethylene dimethyl ether from methanol includes reaction zone and separation zone; the reaction zone comprises a methanol storage tank, a preheater, a fixed bed reactor and a bubbling reactor; the process steps of the reaction zone are that methanol is preheated and vaporized to be mixed with air and then enters a fixed bed reactor, formaldehyde is generated through catalytic oxidation of a formaldehyde synthesis catalyst and enters a bubbling reactor, and the mixture, the methanol and the recycled mixture are catalyzed by a solid acid catalyst in the bubbling reactor to generate polyoxymethylene dimethyl ether; the separation zone comprises an anion exchange resin bed layer, a rectification module and a product storage tank; the separation zone comprises the steps that the discharge of the bubbling reactor enters a rectification module for separation after being deacidified by anion exchange resin, the tri-polymer and the tetramer of the polyformaldehyde dimethyl ether enter a product storage tank, and other components circulate to the bubbling reactor;
the solid acid catalyst is metal modified sulfonic acid type polystyrene cation exchange resin, and the metal is the combination of Cu and Mn.
2. A process according to claim 1, wherein the reaction temperature in the fixed bed reactor is preferably 2%80-700 ℃; the air volume airspeed in the fixed bed reactor is 4000-8000 h-1。
3. The process for synthesizing polyoxymethylene dimethyl ethers from methanol according to claim 1, wherein the reaction pressure in the fixed bed reactor is 0.01 to 30 MPa.
4. The process for synthesizing polyoxymethylene dimethyl ethers from methanol as claimed in claim 1, wherein the mass ratio of methanol to formaldehyde in the feed to the bubble reactor is 0.02-50: 1.
5. The process for synthesizing polyoxymethylene dimethyl ethers from methanol according to claim 1, wherein the reaction temperature in the bubble reactor is 80 to 240 ℃.
6. The process for synthesizing polyoxymethylene dimethyl ethers from methanol according to claim 1, wherein the reaction pressure in the bubble reactor is 0.01 to 15.0 MPa.
7. A process for the synthesis of polyoxymethylene dimethyl ethers from methanol according to claim 1, characterized in that the mixture comprises a first fraction containing methylal, a third fraction containing polyoxymethylene dimethyl ether dimers and a fifth fraction containing polyoxymethylene dimethyl ethers of higher degree of polymerization n >4 separated by a rectification module; the rectification module also separates a second fraction containing methanol and a fourth fraction containing tri-and tetramers of polyoxymethylene dimethyl ether.
8. The process for synthesizing polyoxymethylene dimethyl ethers from methanol as claimed in claim 1, wherein the reaction discharge from the bubble reactor is deacidified by an anion exchange resin bed and then enters a rectification module.
9. The process for synthesizing polyoxymethylene dimethyl ethers from methanol as claimed in claim 7, wherein the first fraction is taken from the top of the first rectifying tower, the second fraction is taken from the top of the second rectifying tower, the third fraction is taken from the top of the third rectifying tower, the fourth fraction is taken from the top of the fourth rectifying tower, and the fifth fraction is taken from the bottom of the fourth rectifying tower.
10. The process for synthesizing polyoxymethylene dimethyl ethers from methanol according to claim 1, wherein said formaldehyde synthesis catalyst comprises one or more of the following components: molybdenum oxide, iron oxide, silicon oxide, aluminum oxide, and metallic silver; the solid acid catalyst is selected from at least one of the following components: acidic cation exchange resin, molecular sieve, dinitrobenzoic acid, ethylene diamine tetraacetic acid, alumina and titanium dioxide.
11. The process method for synthesizing polyoxymethylene dimethyl ethers from methanol according to claim 1, wherein the mass ratio of Cu to Mn is 0.01 to 100.
12. The process for synthesizing polyoxymethylene dimethyl ethers from methanol according to claim 1, wherein the content of the metal is more than 0 and 10w% or less.
13. The process for synthesizing polyoxymethylene dimethyl ethers from methanol according to claim 1, wherein the total exchange capacity of the resin is 3.0 to 6.0 mmol/g.
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