62 results about "Paraldehyde" patented technology

The invention relates to the technical field of pesticide production, in particular to a synthesis method of 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole, which at least comprises the following steps: firstly, mixing trioxymethylene and 1-methyl-3-trifluoromethyl-5-difluoromethoxy-1-H-pyrazole to prepare a solution A; the solution A and chlorosulfonic acid are mixed and then subjected to a chloromethylation reaction, 1-methyl-3-trifluoromethyl-4-chloromethyl-5-difluoromethoxy-1-H-pyrazole is obtained through aftertreatment after sampling detection is qualified, and the method is high in product yield, high in purity, low in production cost, high in production efficiency, easy to operate, capable of meeting the green and environment-friendly requirements and suitable for industrial production. The industrial production is easy to realize.

The invention discloses an application of an ionic liquid in extraction of trioxymethylene, in the process of generating trioxymethylene by acid-catalyzed condensation of a formaldehyde aqueous solution, the ionic liquid is added as an extraction agent to extract and separate the trioxymethylene generated by reaction, and the ionic liquid is methyl tributyl phosphonium bis (trifluoromethanesulfonyl) imide salt; when the ionic liquid is used for extracting trioxymethylene, a ternary azeotropic system of trioxymethylene, water and methylene glycol can be broken, the ionic liquid and trioxymethylene are subjected to nonpolar Van der Waals' force interaction so as to realize extraction, and methylene glycol and water are left in a water phase through hydrogen-bond interaction, so that high-purity trioxymethylene with the purity of more than or equal to 99.5 wt.% is obtained.

The invention discloses piperonyl butoxide and a preparation method thereof. The preparation method comprises the following steps: carrying out mixing reaction on dihydrosassafras oil, acetyl chloride and trioxymethylene in the presence of concentrated hydrochloric acid; after the reaction is finished, chloromethyl material reaction liquid is obtained; mixing and reacting the chloromethyl material reaction liquid with sodium hydroxide and diethylene glycol monobutyl ether to obtain a product containing piperonyl butoxide. According to the preparation method of piperonyl butoxide, the dihydrosassafras oil, acetyl chloride and trioxymethylene are subjected to chloromethylation reaction in the presence of a small amount of concentrated hydrochloric acid, so that the use of a large amount of concentrated hydrochloric acid in the traditional process is avoided, and the problem of waste acid generated in the chloromethylation reaction process is solved; and meanwhile, the content of piperonyl butoxide in the product can be increased, and the content of piperonyl butoxide is ensured to be greater than 98%.

The invention provides a CO2 tall oil-resistant imidazoline Mannich base corrosion inhibitor, a preparation method thereof and a composite corrosion inhibitor. The imidazoline Mannich base corrosion inhibitor with a hydrophilic group and a hydrophobic group is obtained by synthesizing an imidazoline ring from tall oil mixed fatty acid and organic polyamine and then condensing arone and trioxymethylene with a terminal amino group of a side chain of the imidazoline ring. According to the CO2-resistant imidazoline corrosion inhibitor, the CO2-resistant performance of the imidazoline Mannich base corrosion inhibitor in CO2 can be improved by utilizing the synergistic adsorption and isolation effects of imidazole rings with different alkyl structures and Mannich base groups in an acid medium. The imidazoline Mannich base is compounded with the surfactant O-20 and the solubilizer PEG20000, so that the corrosion inhibition performance of the corrosion inhibitor can be further improved. The product meets the environmental protection requirements of enterprises and is beneficial to industrial popularization and application.

The invention relates to the technical field of formaldehyde copolymer production, and discloses a trioxymethylene static crystallization separation method which comprises the following steps: S1, cooling crystallization: the crystallization temperature is 25-30 DEG C, and the crystallization time is 3-4 hours; s2, discharging mother liquor; s3, sweating, wherein the sweating temperature is 50-55 DEG C, and the sweating time is 2-2.5 h; and S4, melting to obtain a high-purity product. According to the invention, the characteristic that the solubility of trioxymethylene is reduced along with temperature reduction is utilized, and separation and purification are realized through temperature gradient regulation and control. The content of trioxymethylene in the prepared finished product reaches 94-96% and is higher than that in the prior art by 90-92%, the formaldehyde content is only 0.1-0.2%, and the impurity content is lower.

This disclosure relates to the field of chemical production technology, and in particular to a production apparatus and method for trioxymethylene. The trioxymethylene production apparatus includes: a reaction unit, a separation unit, a first formic acid absorption unit, and a product distillation unit. The outlet of the reaction unit is connected to the inlet of the separation unit; the gas phase outlet of the separation unit is connected to the inlet of the first formic acid absorption unit; the outlet of the first formic acid absorption unit is connected to the inlet of the product distillation unit; and the liquid phase outlet of the separation unit is connected to the inlet of the reaction unit. The reaction unit is used to convert formaldehyde into trioxymethylene under the action of a catalyst. The separation unit is used to separate the gas phase product from the reaction unit into a liquid stream containing recycled formaldehyde and a gas phase stream containing trioxymethylene. The trioxymethylene production apparatus and method provided by this disclosure are used to remove formic acid, a byproduct in the trioxymethylene production process, and reduce equipment corrosion.

The invention relates to a method for producing polyacetal. In a method for producing polyacetal using a cationic active catalyst, the cationic active catalyst is efficiently deactivated and washed, thereby producing polyacetal having excellent thermal stability. A method for producing a polyacetal, characterized by comprising: a polymerization step for polymerizing at least one cyclic ether and / or cyclic formal containing trioxymethylene in the presence of at least one cationic active catalyst; and a deactivating and washing step in which the crude polyacetal obtained in the polymerization step is brought into contact with a deactivating and washing solution obtained by dissolving or suspending a basic compound in an aliphatic hydrocarbon solvent, thereby deactivating and washing the cationic active catalyst in the same step.

The present invention provides a paraldehyde mother liquor depolymerization apparatus, and relates to the technical field of paraldehyde mother liquor depolymerization, the paraldehyde mother liquor depolymerization apparatus comprises: a kettle body, the side wall of the kettle body is respectively provided with a gas inlet pipe and a gas outlet pipe for conveying steam, and the top of the gas inlet pipe is provided with a mixing box for mixing paraldehyde mother liquor and a catalyst; the heating assembly comprises a hollow liquid distribution disc which is arranged on the upper side of the inner wall of the kettle body and is communicated with the feeding pipe, a second hollow disc which is arranged below the hollow liquid distribution disc and is communicated with the air inlet pipe is arranged on the inner wall of the kettle body, and a first hollow disc which is communicated with the air outlet pipe is arranged on the inner wall of the kettle body; a plurality of discharging pipes penetrating through the first hollow disc and the second hollow disc are arranged at the bottom of the hollow liquid distribution disc, and a plurality of heating air holes formed between the adjacent discharging pipes are formed in the side walls, close to each other, of the first hollow disc and the second hollow disc. The device is reasonable in structure, small in occupied area, large in heat exchange area, high in heat exchange efficiency and high in depolymerization efficiency.

The invention discloses a phosphate ionic liquid copolymer responding to temperature in a trioxymethylene aqueous solution and a preparation method of the phosphate ionic liquid copolymer. The preparation method comprises the following specific steps: regulating and controlling the mixing ratio of 1-alkenyl-3-alkyl imidazole dimethyl phosphate and N-isopropylacrylamide or acrylamide, controlling the reaction temperature at 60-100 DEG C, reacting for 10-48 hours, dialyzing in a dialysis bag, and drying in vacuum after dialyzing to obtain the temperature-responsive phosphate ionic liquid copolymer. The phosphate ionic liquid copolymer provided by the invention shows a reversible upper critical solution temperature in a trioxymethylene aqueous solution. The phosphate ionic liquid copolymer prepared by the method has a wide application prospect in the field of separation and stimuli-responsive materials.

The present application provides a kind of recovery method and device of dilute aldehyde, the recovery method of dilute aldehyde includes the following steps: adding neutralizing agent to dilute aldehyde raw material liquid, the pH value of dilute aldehyde raw material liquid is 6.2-6.8, then rectification recovery treatment is carried out, obtains trioxymethylene material and heavy component material;Dehydration treatment is carried out to heavy component material, obtains dilute formaldehyde material and waste water material;It can recover the dilute aldehyde generated in trioxymethylene production, improve the recovery efficiency of trioxymethylene and formaldehyde in dilute aldehyde, reduce production cost.

The invention discloses a wastewater recovery system for trioxymethylene synthesis wastewater and polymerization wastewater, comprising: a wastewater recovery tower, wherein the wastewater recovery tower is sequentially provided with a tower top gas phase extraction system, a feed pipe, a first side extraction system, a second side extraction system and a tower bottom recovery system from top to bottom; the wastewater recovery tower can effectively recover recyclable components, and the recombinant components and salts that can cause catalyst deactivation are concentrated and then sent for incineration; through system control of an optimal recovery scheme, formaldehyde, benzene, trioxymethylene and the like can be effectively recovered, and the recombinant components, SS, salts and sulfuric acid can be concentrated in the bottom discharge of the wastewater recovery tower, thereby achieving the purpose of energy saving and emission reduction.

A method for producing a polyacetal copolymer, which comprises: a step for obtaining a crude polyacetal copolymer by copolymerizing trioxymethylene, which is a main monomer (a), and a compound that is copolymerizable with trioxymethylene, which is a co-monomer (b), using a protonic acid as a polymerization catalyst (c); a step in which a solution of the crude polyacetal copolymer and the basic compound (d) is introduced into a predetermined continuous mixing device and mixed to obtain a mixture; and a step in which the mixture is introduced into an extruder and melt-kneaded, the basic compound (d) being a carbonate, bicarbonate or the like of an alkali metal element or a group 2 element (excluding Be), and the solvent of the solution of the basic compound (d) being a solvent having active hydrogen.

The invention discloses a preparation method of a posaconazole key intermediate diol olefin compound, which comprises the following steps: dissolving a compound 1 in an organic solvent A, adding a mixed solution of an additive and an organic solvent B, alkali a and trioxymethylene, continuing to react, and treating to obtain a compound 2; dissolving the obtained compound 2 in an organic solvent C, adding a reducing agent, and performing heating reflux reaction to obtain a compound I; the synthesis route is as follows: the reaction process is simple, the raw materials are simple and easy to obtain, harsh reaction conditions are not needed, the route is simple and convenient, the reaction operation is simple, and the drug development potential is achieved.

The invention discloses a metaldehyde continuous synthesis process and a production unit, and belongs to the field of metaldehyde synthesis, the process comprises the following steps: S1, uniformly mixing paraldehyde and acetaldehyde as a reaction mother solution; s2, continuously dropwise adding acetaldehyde and a catalyst into the reaction mother liquor, controlling the reaction temperature to be below-5 DEG C, continuously discharging the synthesized metaldehyde crystals and reaction feed liquid, and carrying out solid-liquid separation; s3, carrying out heat exchange and cooling on one part of the reaction material liquid obtained by separation, refluxing to the step S2 as a reaction mother solution, and depolymerizing the other part of the reaction material liquid to obtain acetaldehyde as an acetaldehyde reactant continuously dropwise added in the step S2; and purifying the separated metaldehyde to obtain the product. And S4, the step S2 and the step S3 are cyclically carried out. According to the scheme, continuous synthesis of metaldehyde is realized, the composition and the temperature of a reaction system are controlled through arrangement of the reaction mother liquor and reflux of the reaction feed liquid, the production efficiency and the product yield are improved, meanwhile, the production energy consumption is reduced, the process is simple, and large-scale production is facilitated.

The invention discloses a synthesis method of 5-ethyl-2-pyridylethanol, and belongs to the technical field of organic synthesis. The invention provides a synthesis method of 5-ethyl-2-pyridylethanol, which takes a special solid acid catalyst as a catalyst, takes paraldehyde and ammonia gas as raw materials, and adjusts the dosage, vaporization temperature, reaction temperature and reaction pressure of the raw materials and the catalyst, so that the final yield of 2-methyl-5-ethylpyridine reaches up to 86.5%. By adjusting reaction conditions, the obtained 2-methyl-5-ethylpyridine reacts with a 37% methanol aqueous solution, and the total yield of the final product 5-ethyl-2-pyridineethanol is up to 81.2%.

The application provides a spherical lignin-phenolic resin and a preparation method and application thereof in adsorbing N-containing organic dyes, and belongs to the technical field of adsorbing materials. The lignin-phenolic resin with regular spherical morphology is prepared by one-step condensation polymerization reaction through the reverse suspension polymerization method under acid catalysis, wherein lignin, hydroquinone and trioxane are used as raw materials. The lignin belongs to renewable resources, has the characteristics of low cost and environmental friendliness, can replace phenol as the main phenol source, and the replacement rate can reach 75%. The yield of the synthesized phenolic resin is as high as 60-80%. In addition, the monomer type can be selected to introduce rich phenolic hydroxyl groups, sulfonic acid groups and other oxygen-containing groups in the resin, the monomer ratio is controlled to change the crosslinking structure of the resin, the adsorption capacity of the resin for N-containing organic dyes is effectively improved, and efficient adsorption of rhodamine B and methylene blue can be realized.

The invention discloses a three-dimensional cross-linked polymer electrolyte based on a TOX monomer, and a preparation method and application thereof. The preparation method of the polymer electrolyte is an in-situ polymerization method, and the electrolyte of the in-situ polymerization method comprises the following raw materials: trioxymethylene and a derivative monomer thereof, a cross-linking agent, a lithium salt, an organic additive and an initiator. Wherein the trioxymethylene and the derivative monomer thereof have a structural formula as shown in a formula (1): # imgabs0 #, wherein R1, R2, R3 and R4 are respectively and independently phenyl, halogen, alkyl of C1-C10, alkenyl of C1-C10, alkynyl of C1-C10, halogenated alkyl of C1-C10, halogenated alkenyl of C1-C10, halogenated alkynyl of C1-C10, cyanoalkyl of C1-C10, cyanoalkenyl of C1-C10 or cyanoalkynyl of C1-C10. The safety of the electrolyte prepared by the method is improved, and the battery prepared from the electrolyte has excellent performance, good interfacial compatibility and the like.

The invention discloses a full-temperature-range liquid phase temperature swing adsorption process for deep dehydration and impurity removal of trioxymethylene, which mainly comprises the following steps: raw material flow, temperature swing adsorption purification, temperature swing adsorption desorption and rectification concentration. The method comprises the following steps: purifying trioxymethylene which is obtained or purchased in a trioxymethylene production process and has the purity of 99.9%, the water content of 500-1000ppm, the content of micromolecular impurity components such as formaldehyde / methanol of 100-300ppm and the content of macromolecular impurity components such as hemiacetal and paraformaldehyde of more than or equal to 50ppm until the purity of the trioxymethylene is more than or equal to 99.999%, the water content of the trioxymethylene is less than or equal to 20-50ppm, and the water content of the trioxymethylene is less than or equal to 20-50ppm; the content of micromolecular impurity components such as formaldehyde and methanol is smaller than or equal to 20-50 ppm, the content of macromolecular impurity components such as methylal and paraformaldehyde is smaller than 20-50 ppm, the problems that the purity of products obtained through existing methods such as special rectification and membrane separation does not reach the standard, and production energy consumption and cost are high are solved, the process is simple, import is replaced, and the method is suitable for industrial production. And the quality requirement of polymer-grade trioxymethylene required by polyformaldehyde production is met.

The utility model discloses a generation device of a formaldehyde bottled gas standard substance. The generation device comprises a sublimation device, a catalytic cracking device, a gas storage bottle and a gas carrying system, according to the utility model, the formaldehyde bottled gas standard substance is prepared by a static cracking method, solid powdery trioxymethylene is adopted as a raw material, and a new way of preparing the gas standard substance from solid to gas is realized by regulating parameters such as cracking temperature, reaction time and the like. The device is simple in overall structure composition, small in size, convenient to disassemble and assemble and flexible to use, and the prepared formaldehyde gas standard substance is stored by adopting a gas cylinder, is convenient to carry and transport and can be flexibly applied to field measurement outside a specific laboratory. In addition, passivation coatings are arranged in the formaldehyde gas storage bottle and the formaldehyde conveying pipeline, so that the formaldehyde gas is prevented from being easily adsorbed, reacted and the like in the pipeline in the preparation process and the storage process in the gas bottle, the stable storage of the gas standard substance in the formaldehyde bottle is realized, and the accurate quantity value of the gas standard substance is ensured.

The invention discloses a preparation process of an antioxidant AO3353, and belongs to the technical field of organic synthesis, the key point of the technical scheme is that the preparation process comprises the following steps: step 1.1, mixing 2, 4-di-tert-pentylphenol and an organic solvent, then adding a catalyst, and uniformly stirring; step 1.2, dropwise adding a toluene solution containing paraldehyde into the solution obtained in the step 1.1 at the temperature of 80-100 DEG C, and then reacting for 3-6 hours; 2.1, after the reaction in the step 1.2 is finished, raising the temperature to 115-120 DEG C, distilling out the organic solvent, then reducing the reaction temperature to 25-35 DEG C, then adding triethylamine, and stirring; and step 2.2, preparing a mixed solution of acryloyl chloride and an organic solvent, dropwise adding the mixed solution into the step 2.1, reacting for 2-4 hours at the temperature of 30-60 DEG C, then adding water to recover triethylamine, carrying out reduced pressure distillation to remove the solvent, crystallizing and filtering to obtain the antioxidant AO3353, thereby achieving the effect of reducing the use cost of the antioxidant AO3353.

The invention discloses a polyformaldehyde wastewater treatment method and application, and belongs to the technical field of wastewater treatment. The method comprises the following steps: firstly, in an anaerobic environment, adding hexadecyl trimethyl ammonium bromide and ethanol into wastewater to form micelles to wrap trioxymethylene, and degrading formaldehyde and macromolecular organic matters by using anaerobic flora; secondly, introducing anaerobic effluent into a facultative environment, triggering micelles to disintegrate and release trioxymethylene in stages by continuously and linearly reducing pH, and meanwhile, adding domestication flora in stages according to pH change so as to dynamically degrade released formaldehyde; and finally, thorough mineralization is realized through two-stage biological oxidation in an aerobic environment. According to the invention, random depolymerization of trioxymethylene is blocked by space wrapping, and the release rate is controlled by time sequence acidification, so that formaldehyde generation and biodegradation are dynamically balanced, inhibition of toxicity peak on microorganisms is effectively avoided, and the removal efficiency of formaldehyde and organic pollutants and the operation stability of the system are remarkably improved.

The application discloses a system and an energy-saving process for producing trioxymethylene by means of a heat pump assisted reaction rectification coupled variable pressure rectification, and the process comprises the following steps: feeding a formaldehyde aqueous solution into a pre-rectification tower to enrich, feeding the dilute formaldehyde collected from the top of the tower into a heat pump unit C1 to increase the pressure and temperature, and then taking the dilute formaldehyde as a tower bottom heat source of a high-pressure rectification tower; feeding the concentrated formaldehyde collected from the bottom of the pre-rectification tower into a reaction rectification tower, and converting the concentrated formaldehyde into trioxymethylene under the catalysis of a catalyst; taking the azeotrope of formaldehyde, water and trioxymethylene from the top of the reaction rectification tower as a tower bottom heat source of the pre-rectification tower, feeding the azeotrope into a low-pressure rectification tower after heat exchange and condensation, taking the azeotrope vapor from the top of the low-pressure rectification tower as a heat source of the tower bottom of the reaction rectification tower after increasing the pressure and temperature by means of a heat pump unit C2, feeding the azeotrope into the high-pressure rectification tower after heat exchange and condensation, feeding the dilute formaldehyde collected from the bottom of the low-pressure rectification tower back to the pre-rectification tower to enrich, and collecting the trioxymethylene product from the bottom of the high-pressure rectification tower. The application can improve the single-pass conversion rate of trioxymethylene, simplify the operation, and reduce the operation cost and energy consumption.

The utility model discloses a system for producing polyformaldehyde, and belongs to the technical field of polymer production. According to the continuous flow synthesis device disclosed by the utility model, formaldehyde, trioxymethylene, dioxopenta (penta) ring and polyformaldehyde are prepared into a continuous flow synthesis device through a plurality of different synthesis units, materials in each stage can be conveyed to the next stage through simple operation in the production process, and meanwhile, unreacted or waste materials in a system can be recycled; and the recycled materials enter the previous stage to be continuously utilized, so that the waste of the materials is avoided, and the energy consumption during subsequent waste treatment is also saved.

The utility model discloses a trioxymethylene light component removal tower feeding alkali adding system, which belongs to the technical field of trioxymethylene production and comprises an intermediate storage tank, a static tank, a trioxymethylene light component removal tower body and an alkali tank. The device has the beneficial effects that the dosage of put alkali liquor is adjusted by arranging the alkali inlet adjusting valve, the dosage of desalted water is controlled by arranging the desalted water inlet adjusting valve according to the dosage of the put alkali liquor, and the dosage of the desalted water is controlled by arranging the check valve. By arranging the first pipeline and the second pipeline, a dilute alkali solution obtained by mixing alkali liquor and desalted water can smoothly enter the first pipeline to be mixed with materials conveniently, the materials are prevented from reversely entering the alkali inlet pipeline and the desalted water pipeline, and the materials and the dilute alkali solution can be fully mixed conveniently by arranging the mixer and the static tank; and the dilute alkali solution is fully reacted with acidic substances such as formic acid and formaldehyde carried by the material, and meanwhile, the depolymerization of trioxymethylene is further prevented, so that the purity of trioxymethylene fed into the light component removal tower is greatly improved, and the rectification quality is improved.

The preparation method comprises the following steps: adding a soluble polyester hot melt adhesive into trioxymethylene and trichloromethane, stirring and dissolving, then adding trimethylchlorosilane, placing in an ice-water bath, stirring, then adding a tin tetrachloride-trichloromethane solution, stirring for 0.5 h, then adding a sodium hydroxide solution, stirring for 0.5 h, then adding a sodium hydroxide solution, stirring for 0.5 h, adding a sodium hydroxide solution, stirring for 0.5 h, adding a sodium hydroxide solution, and stirring for 0.5 h to obtain the special water-based slurry polymer for the polyester fiber. Heating to 30-50 DEG C, continuously reacting for 1-2 hours, finally adding a small amount of methanol / water mixed solution, and carrying out vacuum concentration and room-temperature vacuum drying for 24 hours to obtain the chloromethylated soluble polyester hot melt adhesive. And dissolving the chloromethylated soluble polyester hot melt adhesive and an amine compound in a first solvent, reacting at 40-80 DEG C for 6-12 hours, precipitating with diethyl ether, and drying in vacuum for 12 hours to obtain the water-based slurry polymer. Compared with a traditional sizing agent, the obtained water-based sizing agent polymer has the advantages of excellent bonding force, wear resistance and the like, and can be applied to sizing agents for polyester fibers.

The invention discloses a preparation method of modified polyformaldehyde with conductive and wear-resistant functions. The preparation method is characterized by comprising the following steps: putting 2-4 parts by weight of carbon nanotubes into 100 parts by weight of an oxidizing agent formed by mixing concentrated HNO3 and concentrated H2SO4, and reacting to obtain a modified carbon nanomaterial; dissolving 2-5 parts by weight of a coupling agent into 100 parts by weight of absolute ethyl alcohol, and reacting to obtain a silane coupling agent solution; soaking 8-10 parts by weight of MoS2 powder in 1-3 parts by weight of a silane coupling agent solution for reaction to obtain modified MoS2; the preparation method comprises the following steps: adding 1-3 parts by weight of a modified carbon nanomaterial and 1-3 parts by weight of modified MoS2 into 100 parts by weight of trioxymethylene, then adding 4-8 parts by weight of a boron trifluoride diethyl etherate complex catalyst, carrying out a polymerization reaction, and carrying out underwater granulation to obtain the modified polyformaldehyde particles, which have the advantages of low friction coefficient, high wear resistance and high conductivity.

The present invention discloses a method for synthesizing 5-ethyl-2-pyridineethanol, belonging to the technical field of organic synthesis. The present invention provides a method for synthesizing 5-ethyl-2-pyridineethanol. The method uses a specially prepared solid acid catalyst as a catalyst, paraldehyde and ammonia as raw materials, and adjusts the amounts of the raw materials and catalyst, vaporization temperature, reaction temperature, and reaction pressure. The yield of 2-methyl-5-ethylpyridine is as high as 86.5%. The obtained 2-methyl-5-ethylpyridine is reacted with a 37% methanol aqueous solution by adjusting the reaction conditions. The total yield of the final product, 5-ethyl-2-pyridineethanol, is as high as 81.2%.

The application belongs to the field of catalytic synthesis of trioxane, and particularly relates to a catalytic synthesis process and device of trioxane. The process comprises the following steps: step one, a mixture of methylal and methanol is mixed with oxygen-containing gas as raw material, and reacts to generate formaldehyde under the action of a first catalyst; step two, formaldehyde is dissolved and absorbed by water to obtain concentrated formaldehyde; step three, the concentrated formaldehyde is subjected to catalytic synthesis reaction under the action of a second catalyst to generate trioxane. The device comprises, in sequence in the feeding direction, an oxidation reactor, a heat exchanger, a formaldehyde absorption tower, a fixed bed reactor and a catalytic distillation tower; compared with pure methanol or pure methylal, the raw material of the application is easier to obtain and has lower production cost; the application obtains higher formaldehyde concentration through improved catalyst, and does not need to prepare high-concentration formaldehyde again by negative pressure concentration, so that the single-pass utilization rate of formaldehyde is improved, and various technical problems in the prior art are properly optimized.

The invention relates to a method for producing polyacetal. The present invention addresses the problem of providing a method with which it is possible to produce a polyacetal having good thermal stability even when a boron trifluoride ether complex is diluted and then used, and to produce such a polyacetal with good yield and stability. A method for producing a polyacetal, said method comprising a polymerization step in which (a) at least one cyclic ether and / or cyclic formal containing trioxymethylene and optionally a non-cyclic low-molecular-weight acetal compound are supplied; (b) a polymerization catalyst comprising boron trifluoride or a boron trifluoride complex; and (c) an organic solvent having an ester structure represented by formula (1), the water content of (a) being 0.01-30 ppm by mass, and the water content of (c) being 1-50 ppm by mass. # imgabs0 # (1) (In formula (1), R1 and R2 each independently represent a monovalent hydrocarbon group having 1-5 carbon atoms).

The invention relates to a preparation method of diphenylmethane series diamine and polyamine, which comprises the following steps: reacting formaldehyde and aniline in the presence of an acid catalyst to prepare diphenylmethane series diamine and polyamine, sequentially neutralizing and washing the polyamine, and removing excessive aniline by adopting a vacuum distillation mode to prepare a qualified product. The trioxymethylene in the recycled aniline is removed by treating the recycled aniline, so that polycyclic high-polymer blockages, N-heterocyclic polyamine and N-methylaniline impurities in the reaction process can be greatly reduced, and the operation stability and the quality of an MDI product are improved.