Composition for trioxymethylene and method for synthesizing trioxymethylene

Abstract

The invention relates to the technical field of trioxymethylene production, and discloses a composition for trioxymethylene and a method for synthesizing trioxymethylene. The composition contains a formaldehyde aqueous solution, an acid catalyst and a catalytic promoter, in the formaldehyde aqueous solution, the content of formaldehyde is 28-75wt%, the content of methanol is 0.5-3wt%, and the content of formic acid is 0.02-0.5 wt%; the acid catalyst is sulfuric acid of which the concentration is not lower than 90wt%; relative to 1kg of the formaldehyde aqueous solution, the content of the acid catalyst is 0.3 to 1.0 mol, and the content of the catalytic promoter is 0.3 to 2.0 mol. According to the scheme, the activity of water in the formaldehyde aqueous solution can be reduced, and the relative volatility of the product trioxymethylene and water can be improved, so that the generation of a byproduct formic acid is reduced, and the conversion rate of formaldehyde and the yield of trioxymethylene are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of trioxane production, in particular to a composition for trioxane and a method for synthesizing trioxane. BACKGROUND

[0002] Formaldehyde is an important Cl raw material (Cl synthons), but all reactions need to be replaced by trioxane or polyoxymethylene (water-free reactions can only use trioxane). At the same time, trioxane is a raw material for producing polyoxymethylene engineering plastics, polymethoxy dimethyl ether and dozens of bulk chemicals and fine chemicals. Producing series of bulk chemicals through trioxane is an important way to digest methanol capacity, extend C1 industrial chain, and obtain significant economic and environmental benefits.

[0003] At present, a synthesis method with low cost, high yield and good selectivity is the direction of effort. Among them, the liquid phase soluble acid synthesis method is the mainstream process technology route for synthesizing trioxane at present. The advantages of this process flow are mature and simple technology, stable and reliable operation of the reaction device. The disadvantages are that concentrated sulfuric acid as a catalyst seriously corrodes the equipment, the catalyst fails quickly and is difficult to separate and recover, which leads to the catalyst cannot be recycled, the conversion rate of trioxane synthesized by using this method is low, and there are many by-products.

[0004] CN106518837A discloses a method for synthesizing trioxane, which comprises using formaldehyde aqueous solution as a reaction raw material, and performing catalytic reaction under the action of an acid catalyst and a salt assistant to prepare trioxane. The acid catalyst comprises a combination of one or more of heteropoly acid, strong acid cation exchange resin, sulfonic acid and sulfuric acid, and the salt assistant is an amphoteric salt or a mixed salt composed of a salt formed by at least two of an organic anion, an organic cation, an inorganic anion and an inorganic cation and an amphoteric salt. The method can improve the activity of the catalyst in the reaction system, thereby improving the generation concentration of trioxane, improving the relative volatility of trioxane to water, and reducing the concentration of byproduct formic acid in the reaction solution. However, the technical solution has three defects. First, according to the reaction raw material and catalytic system, the highest yield of trioxane can only reach 67.76 mol%, which is difficult to further improve. Second, the highest concentration of formaldehyde aqueous solution in the scheme is only 70 wt%, and the scheme is only concerned with the trioxane synthesis results of the low-concentration formaldehyde solution combined with the catalyst and assistant system by experimental means, without studying the influence of high-concentration formaldehyde solution raw material combined with the catalyst system formula in the trioxane equilibrium reaction. Third, in industry, the reactor for the trioxane synthesis reaction liquid phase usually uses zirconium or enamel material with strong corrosion resistance because the reaction liquid phase contains sulfuric acid and formic acid, and the subsequent equipment usually selects stainless steel or duplex steel because the gas phase only contains formic acid. Therefore, the position of corrosion is usually the subsequent equipment connected with the gas phase of the reactor, and reducing the content of formic acid in the gas phase is the key to solving the corrosion problem. However, the scheme does not provide data of formic acid in the gas phase, and has no reference value for the solution of the gas phase corrosion problem. SUMMARY

[0005] The purpose of the present application is to provide a trioxane synthesis method capable of improving the selectivity and yield of trioxane and reducing the generation amount of byproduct formic acid.

[0006] To achieve the above-mentioned purpose, the first aspect of the present application provides a composition for trioxane, which comprises formaldehyde aqueous solution, acid catalyst and catalytic assistant. In the formaldehyde aqueous solution, the content of formaldehyde is 28-75 wt%, the content of methanol is 0.5-3 wt%, and the content of formic acid is 0.02-0.5 wt%. The acid catalyst is sulfuric acid with a concentration not less than 90 wt%. The content of the acid catalyst is 0.3-1.0 mol, and the content of the catalytic assistant is 0.3-2.0 mol relative to 1 kg of the formaldehyde aqueous solution.

[0007] In some embodiments, the catalytic assistant is sodium benzenesulfonate and / or sodium methanesulfonate.

[0008] In some embodiments, the catalytic assistant is sodium benzenesulfonate and sodium methanesulfonate in a mass ratio of 1:0.3-3.85.

[0009] In some embodiments, the content of the acid catalyst is 0.6-0.8 mol relative to 1 kg of the formaldehyde aqueous solution.

[0010] In some embodiments, the content of the catalytic assistant is 0.5-1.0 mol relative to 1 kg of the formaldehyde aqueous solution.

[0011] In some embodiments, the catalytic assistant is provided in the form of a catalytic assistant aqueous solution, and the concentration of the catalytic assistant in the catalytic assistant aqueous solution is 25-30 wt%.

[0012] A second aspect of the present application provides a method for synthesizing trioxane, which is performed by using the composition for trioxane of the first aspect, and comprises: performing catalytic reaction of the components in the composition under catalytic conditions.

[0013] In some embodiments, the operation of performing catalytic reaction of the components in the composition under catalytic conditions comprises: adding a catalytic assistant to the formaldehyde aqueous solution under the presence of an acid catalyst to perform catalytic reaction.

[0014] In some embodiments, the adding rate of the catalytic assistant is 0.1-0.2 mol / min relative to 1 mol of the formaldehyde aqueous solution.

[0015] In some embodiments, the catalytic reaction is performed under reflux conditions.

[0016] In some embodiments, the volume reflux ratio of the reflux conditions is 1-5:1.

[0017] In some embodiments, the reaction temperature of the catalytic reaction is 96-107℃.

[0018] In some embodiments, the reaction pressure of the catalytic reaction is 0.1-0.3 MPa.

[0019] In some embodiments, the catalytic reaction is performed in a reaction kettle.

[0020] In some embodiments, the overhead temperature of the reaction kettle is 90-123℃.

[0021] By the above technical solutions, the present application has at least the following advantages over the prior art: The scheme provided by the present application can not only reduce the activity of water in the formaldehyde aqueous solution, but also improve the relative volatility of the product trioxane and water, thereby reducing the generation of byproduct formic acid. Based on this, the scheme of the present application can solve the problems of high dosage of sulfate, chlorate and ionic liquid type auxiliary, affecting the product quality and being easy to decompose.

[0022] More specifically, in the same catalytic reaction, the conversion rate of formaldehyde can reach 46 mol% or more, the selectivity of trioxane can reach 90 mol% or more, and the yield of trioxane can reach 44 mol% or more. The synthesis method has good stability, and the yield of trioxane can still be maintained at a high level after 72 hours of continuous reaction. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of a rectifying device for synthesizing trioxane by the method of the present application.

[0024] BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values claimed herein are not to be understood as limited to the exact values recited as implicitly split into a smaller increments. For values having an inherent degree of variability, such as the size of a cell, the degree of impurity, a time interval, and the like, the term "about" is used when the last named value is not exactly achieved to allow for some variability as would be understood by one of ordinary skill in the art.

[0026] As described previously, the first aspect of the present application provides a composition for trioxane, which contains a formaldehyde aqueous solution, an acid catalyst and a catalytic auxiliary; In the formaldehyde aqueous solution, the content of formaldehyde is 28-75 wt%, the content of methanol is 0.5-3 wt%, and the content of formic acid is 0.02-0.5 wt%. The acid catalyst is sulfuric acid with a concentration of not less than 90 wt%. The content of the acid catalyst is 0.3-1.0 mol, and the content of the catalytic auxiliary is 0.3-2.0 mol, relative to 1 kg of the formaldehyde aqueous solution.

[0027] According to a preferred embodiment, the catalytic auxiliary is sodium benzenesulfonate and / or sodium methanesulfonate. The inventors of the present application found in the research process that in this preferred case, the catalytic auxiliary has a larger polarity, can form intermolecular hydrogen bonds with water molecules, reduce the activity of water in the formaldehyde aqueous solution, and also improve the relative volatility of the product trioxane and water, thereby reducing the generation of byproduct formic acid.

[0028] According to a particularly preferred embodiment, the catalytic assistant is sodium benzenesulfonate and sodium methanesulfonate with a mass ratio of 1:0.3-3.85. In this preferred case, the technical solution provided by the present application can further improve the conversion rate of formaldehyde and the yield of trioxane.

[0029] According to a preferred embodiment, the content of the acid catalyst is 0.6-0.8 mol with respect to 1 kg of the formaldehyde aqueous solution. In this preferred case, the technical solution provided by the present application can further improve the conversion rate of formaldehyde and the yield of trioxane.

[0030] According to a preferred embodiment, the content of the catalytic assistant is 0.5-1.0 mol with respect to 1 kg of the formaldehyde aqueous solution. In this preferred case, the technical solution provided by the present application can further improve the conversion rate of formaldehyde and the yield of trioxane, while further reducing the content of formic acid.

[0031] It should be noted that, in the present application, the formaldehyde aqueous solution contains formaldehyde, methanol, formic acid, and the rest is water.

[0032] If the catalytic assistant is in a solid state, it needs to be directly added to the running device through a special sealed solid feeder, and a purging and air extraction and dust removal system also needs to be set up, which is very complicated. In some embodiments, the catalytic assistant is provided in the form of a catalytic assistant aqueous solution, and the concentration of the catalytic assistant in the catalytic assistant aqueous solution is 25-30 wt%. In this embodiment, it is beneficial to modify the existing industrial device, and only a container and a gravity flow pipeline are needed to add the catalytic assistant for use.

[0033] As described above, the second aspect of the present application provides a method for synthesizing trioxane, which applies the composition for trioxane of the first aspect, and includes: catalytically reacting the components in the composition under catalytic conditions.

[0034] In some embodiments, the operation of catalytically reacting the components in the composition under catalytic conditions includes: adding the catalytic assistant to the formaldehyde aqueous solution under the presence of the acid catalyst to perform catalytic reaction.

[0035] In some embodiments, the addition rate of the catalytic assistant is 0.1-0.2 mol / min with respect to 1 mol of the formaldehyde aqueous solution. In this embodiment, the technical solution provided by the present application can improve the conversion rate of formaldehyde and the yield of trioxane.

[0036] In order to avoid evaporation of formaldehyde and trioxane together, in some embodiments, the catalytic reaction is carried out under reflux conditions. In this embodiment, the unreacted formaldehyde can be returned to the reactor for continuous reaction, and the overhead trioxane can be concentrated for subsequent refining.

[0037] In some embodiments, the volume reflux ratio of the reflux conditions is 1-5:1. In this embodiment, a higher concentration of trioxane can be obtained, and the unreacted formaldehyde carried is returned to the reactor for continuous reaction.

[0038] It should be noted that in the present application, the volume reflux ratio refers to the ratio of the liquid flow returned to the top of the tower from the tower top condenser to the flow of the product (trioxane) taken from the top of the tower.

[0039] In some embodiments, the reaction temperature of the catalytic reaction is 96-107℃. The above reaction temperature is controlled by the temperature of the reaction kettle.

[0040] In some embodiments, the reaction pressure of the catalytic reaction is 0.1-0.3 MPa. It should be noted that the above pressure refers to absolute pressure.

[0041] In some embodiments, the residence time of the catalytic reaction is 3-15h under continuous feeding. In this embodiment, not only can the formaldehyde solution and the catalyst, the auxiliary agent be fully contacted to make the reaction proceed fully, but also the industrialization can be facilitated, and the equipment investment cost can be reduced.

[0042] In some embodiments, the catalytic reaction is carried out in a reaction kettle.

[0043] The reaction liquid is in a saturated boiling state under controlled pressure. Increasing the pressure means increasing the temperature, and high temperature improves the reaction rate, which is beneficial to improve the reaction conversion rate, but too high temperature will make the selectivity worse. In some embodiments, the reaction pressure of the catalytic reaction is 0.1-0.3 MPa.

[0044] The system pressure corresponds to the corresponding saturation temperature, and in some embodiments, the top temperature of the reaction kettle is 90-123℃.

[0045] In some embodiments, the catalytic reaction is carried out in a rectification device, which includes a rectification head, a glass rectification tower section, a reaction kettle, a raw material tank, a peristaltic pump, a temperature sensor, a product collection bottle, and a condensation warm water circulation system.

[0046] In the present application, the rectification head belongs to a combined custom device, which is provided with a condensation warm water jacket pipe and an electromagnetic relay switching valve, which is used to switch between full reflux and distillation of the overhead liquid phase by time.

[0047] In some embodiments, the inner diameter of the glass rectification tower section is 10-30 mm.

[0048] In some embodiments, the glass rectification tower section is internally filled with 316L stainless steel triangular spiral fillers with a particle size of 2.0 mm x 2.0 mm.

[0049] In some embodiments, the average height of the fillers is 0.25-0.5 m.

[0050] In some embodiments, the raw material tank is a three-necked flask.

[0051] In the present application, the rectification device can further include auxiliary equipment such as a heating jacket, which is used to provide heat. For example, a reaction kettle heating jacket is used to heat or insulate the reaction kettle, and a raw material tank heating jacket is used to heat or insulate the raw material tank. This will not be described here again, and those skilled in the art should not understand it as a limitation on the present application.

[0052] In some embodiments, the temperature sensor is a Pt100 model.

[0053] In some embodiments, the reaction kettle is a four-necked flask with a volume of 0.5-1.5 L.

[0054] In some embodiments, the raw material tank is a three-necked flask with a volume of 0.5-1.5 L.

[0055] In some embodiments, the peristaltic pump is connected to the reaction kettle and the raw material tank, and is used for continuous feeding.

[0056] In some embodiments, in the catalytic reaction, the conditions are controlled so that the liquid level in the reaction kettle remains constant.

[0057] The following is combined Figure 1 A specific embodiment is provided to illustrate the process flow of the present application for synthesizing trioxane: First, turn on the condensation warm water circulation system 10, preheat the water temperature to about 60-70℃, establish a water circulation cooling system; the raw material tank heating jacket 6 maintains the formaldehyde aqueous solution in the three-necked flask 5 at not less than 70℃.

[0058] The formaldehyde aqueous solution is added from the three-necked flask 5 to the four-necked flask 3, the temperature of the four-necked flask 3 is controlled to be 96-105 DEG C by the reaction kettle heating jacket 4, the acid catalyst is added to the four-necked flask 3; then the catalytic aid is added to the four-necked flask 3, the catalytic reaction is carried out, the reaction generates the gas phase which enters the glass rectification tower section 2, the temperature sensor 8 can display the temperature of the top of the four-necked flask 3, the three-necked flask 5 and the glass rectification tower section 2; after refluxing for 0.5-1.5 h, the volume reflux ratio of the rectification head 1 at the top of the tower is adjusted to be 1-5:1; the catalytic product obtained through the catalytic reaction is distilled out from the top of the tower, is condensed into liquid at the rectification head 1 at the top of the tower, part of which is refluxed back into the tower, and part of which is collected into the product collecting bottle 9. Then the formaldehyde aqueous solution is continuously added into the four-necked flask 3 by the peristaltic pump 7 so that the liquid level in the reaction kettle is kept constant. After long-period operation, residues will appear in the kettle, and with the increase of the formaldehyde concentration of the feed, the residues will appear in the kettle more quickly, at this time, the liquid containing residues at the bottom of the kettle is drawn out by using one of the mouths of the four-necked flask 3, so that the residue generation at the bottom of the kettle is effectively controlled, and the stable operation of the system is maintained.

[0059] The application will be described in detail below by examples. In the following examples, if no special description is given, the instruments, reagents, materials and the like involved are conventional instruments, reagents, materials and the like, which can be obtained through conventional commercial channels. Among them, without the contrary description, the reagents used are commercially available analytical pure products.

[0060] Formaldehyde aqueous solution-1: formaldehyde raw material from an industrial methanol oxidation formaldehyde device; wherein the content of formaldehyde is 50wt%, the content of methanol is 1wt%, the content of formic acid is 0.04wt%, and the rest is water.

[0061] Formaldehyde aqueous solution-2: formaldehyde raw material from a formaldehyde vacuum concentration device; wherein the content of formaldehyde is 60wt%, the content of methanol is 1.7wt%, the content of formic acid is 0.06wt%, and the rest is water.

[0062] Formaldehyde aqueous solution-3: formaldehyde raw material from a formaldehyde pressurized concentration device; wherein the content of formaldehyde is 37.14wt%, the content of methanol is 1.89wt%, the content of formic acid is 0.08wt%, and the rest is water.

[0063] Formaldehyde aqueous solution-4: formaldehyde raw material from a formaldehyde vacuum concentration device; wherein the content of formaldehyde is 70wt%, the content of methanol is 1.8wt%, the content of formic acid is 0.07wt%, and the rest is water.

[0064] Formaldehyde aqueous solution-5: formaldehyde raw material from a formaldehyde vacuum concentration device; wherein the content of formaldehyde is 75wt%, the content of methanol is 1.9wt%, the content of formic acid is 0.08wt%, and the rest is water.

[0065] Sodium benzenesulfonate: purchased from Macklin Chemical Reagent Co., Ltd.

[0066] Sodium methanesulfonate: purchased from Merck Life Science Co., Ltd.

[0067] In the following examples, the concentration of sulfuric acid used is 98wt%.

[0068] In the following examples, the method for synthesizing trioxane provided is carried out in a rectification device, which includes a rectification head, a glass rectification tower section, a reaction kettle, a raw material tank, a peristaltic pump, a temperature sensor, a product collection bottle, a condensation warm water circulation system; wherein the rectification head belongs to a combined custom equipment, with a condensation warm water jacket pipe and an electromagnetic relay switching valve, through time switching full reflux and distillation overhead liquid phase operation; the glass rectification tower section has an inner diameter of 20 mm, and is internally provided with 2.0 mm×2.0 mm 316L type stainless steel triangular spiral fillers, with a filler height of 0.45 m; the reaction kettle is a 1 L four-necked flask, and the raw material tank is a 1 L three-necked flask, the reaction kettle is heated or kept warm by using a reaction kettle heating jacket, and the raw material tank is heated or kept warm by using a raw material tank heating jacket; the temperature sensor is of Pt100 type; the peristaltic pump is connected with the reaction kettle and the raw material tank, and continuous feeding is carried out through the peristaltic pump.

[0069] The following examples are used to illustrate the method for synthesizing trioxane provided by the present application Example 1 Turn on the condensation warm water circulation system, preheat the water temperature to about 65℃, and establish a water circulation cooling system; Add 600 g of formaldehyde aqueous solution-1 to the reaction kettle (four-necked flask), control the reaction kettle temperature to be 100.17℃, the reaction pressure to be 0.1 MPa, and the tower top temperature to be 100℃; Add the acid catalyst (sulfuric acid) to the four-necked flask 3; Dissolve the catalytic aid in water to obtain a catalytic aid aqueous solution; After sufficient reflux for 1 h, adjust the volume reflux ratio to be 2.0:1, at this time the catalytic product is evaporated from the tower top, then continuously add formaldehyde aqueous solution-1 to the reaction kettle through the peristaltic pump to keep the liquid level in the reaction kettle constant. After continuous reaction for 5 h, stop the reaction; The catalytic aid is sodium benzenesulfonate and sodium methanesulfonate with a mass ratio of 1:0.31; The amount of the acid catalyst is 0.6 mol, and the amount of the catalytic aid is 0.5 mol, relative to 1 kg of formaldehyde aqueous solution; The concentration of the catalytic aid in the catalytic aid aqueous solution is 26.9wt%; The addition rate of the catalytic aid is 0.12 mol / min.

[0070] Example 2 Open the condensation warm water circulation system, preheat the water temperature to about 65℃, and establish a water circulation cooling system; 600g of formaldehyde aqueous solution-2 was added to the reaction kettle (four-necked flask), the temperature of the reaction kettle was controlled at 104.75℃, the reaction pressure was 0.3MPa, and the overhead temperature was 105℃; The acid catalyst (sulfuric acid) was added to the four-necked flask 3; The catalytic aid was dissolved in water to obtain a catalytic aid aqueous solution; After refluxing for 1h, the volume reflux ratio was adjusted to 2.0:1, at which time the catalytic product was distilled from the overhead, and then formaldehyde aqueous solution-2 was continuously added to the reaction kettle through a peristaltic pump to keep the liquid level in the reaction kettle constant. After continuous reaction for 72h, the reaction was stopped; The catalytic aid was sodium benzenesulfonate and sodium methanesulfonate in a mass ratio of 1:3.85; The amount of acid catalyst was 0.8mol and the amount of catalytic aid was 0.5mol relative to 1kg of formaldehyde aqueous solution; The concentration of catalytic aid in the catalytic aid aqueous solution was 26.9wt%; The addition rate of catalytic aid was 0.12mol / min.

[0071] Example 3 Open the condensation warm water circulation system, preheat the water temperature to about 65℃, and establish a water circulation cooling system; 600g of formaldehyde aqueous solution-3 was added to the reaction kettle (four-necked flask), the temperature of the reaction kettle was controlled at 96℃, the reaction pressure was 0.1MPa, and the overhead temperature was 101℃; The acid catalyst (sulfuric acid) was added to the four-necked flask 3; The catalytic aid was dissolved in water to obtain a catalytic aid aqueous solution; After refluxing for 1h, the volume reflux ratio was adjusted to 2.0:1, at which time the catalytic product was distilled from the overhead, and then formaldehyde aqueous solution-3 was continuously added to the reaction kettle through a peristaltic pump to keep the liquid level in the reaction kettle constant. After continuous reaction for 5h, the reaction was stopped; The catalytic aid was sodium benzenesulfonate and sodium methanesulfonate in a mass ratio of 1:2; The amount of acid catalyst was 0.6mol and the amount of catalytic aid was 1.0mol relative to 1kg of formaldehyde aqueous solution; The concentration of catalytic aid in the catalytic aid aqueous solution was 26.9wt%; The addition rate of catalytic aid was 0.12mol / min.

[0072] Example 4 Open the condensation warm water circulation system, preheat the water temperature to about 65℃, to establish the water circulation cooling system; 600g formaldehyde aqueous solution-4 is added to the reaction kettle (four-necked flask), the temperature of the reaction kettle is controlled at 101.69℃, the reaction pressure is 0.1MPa, and the overhead temperature is 98℃; The acid catalyst (sulfuric acid) is added to the four-necked flask 3; The catalytic aid is dissolved in water to obtain a catalytic aid aqueous solution; After refluxing for 1h, the volume reflux ratio is adjusted to 2.0:1, at this time the catalytic product is evaporated from the top of the column, then formaldehyde aqueous solution-4 is continuously added to the reaction kettle through a peristaltic pump to keep the liquid level in the reaction kettle constant. After continuous reaction for 5h, the reaction is stopped; The catalytic aid is sodium benzenesulfonate and sodium methanesulfonate in a mass ratio of 1:0.31; The amount of the acid catalyst is 0.6mol and the amount of the catalytic aid is 0.5mol relative to 1kg of formaldehyde aqueous solution; The concentration of the catalytic aid in the catalytic aid aqueous solution is 26.9wt%; The addition rate of the catalytic aid is 0.12mol / min.

[0073] Example 5 Open the condensation warm water circulation system, preheat the water temperature to about 65℃, to establish the water circulation cooling system; 600g formaldehyde aqueous solution-5 is added to the reaction kettle (four-necked flask), the temperature of the reaction kettle is controlled at 101.75℃, the reaction pressure is 0.1MPa, and the overhead temperature is 97.8℃; The acid catalyst (sulfuric acid) is added to the four-necked flask 3; The catalytic aid is dissolved in water to obtain a catalytic aid aqueous solution; After refluxing for 1h, the volume reflux ratio is adjusted to 2.0:1, at this time the catalytic product is evaporated from the top of the column, then formaldehyde aqueous solution-5 is continuously added to the reaction kettle through a peristaltic pump to keep the liquid level in the reaction kettle constant. After continuous reaction for 5h, the reaction is stopped; The catalytic aid is sodium benzenesulfonate and sodium methanesulfonate in a mass ratio of 1:0.31; The amount of the acid catalyst is 0.6mol and the amount of the catalytic aid is 0.5mol relative to 1kg of formaldehyde aqueous solution; The concentration of the catalytic aid in the catalytic aid aqueous solution is 26.9wt%; The addition rate of the catalytic aid is 0.12mol / min.

[0074] Example 6 The method for synthesizing trioxane in this embodiment is as follows:

[0075] The method for synthesizing trioxane in this embodiment is as follows: The condensation water circulation system was opened, and the water temperature was preheated to about 65°C to establish the water circulation cooling system. 600g of formaldehyde aqueous solution-5 was added to the reaction kettle (four-necked flask), the temperature of the reaction kettle was controlled at 106.35°C, the reaction pressure was 0.3MPa, and the overhead temperature was 102°C. The acid catalyst (sulfuric acid) was added to the four-necked flask 3. The catalytic aid was dissolved in water to obtain a catalytic aid aqueous solution. After refluxing for 1h, the volume reflux ratio was adjusted to 2.0:1, at which time the catalytic product was evaporated from the top of the column, and then the formaldehyde aqueous solution-5 was continuously added to the reaction kettle through a peristaltic pump to keep the liquid level in the reaction kettle constant. After continuous reaction for 5h, the reaction was stopped. The catalytic aid was sodium benzenesulfonate and sodium methanesulfonate with a mass ratio of 1:0.31. The amount of the acid catalyst was 0.6mol, and the amount of the catalytic aid was 0.5mol, relative to 1kg of formaldehyde aqueous solution. The concentration of the catalytic aid in the catalytic aid aqueous solution was 30wt%. The addition rate of the catalytic aid was 0.12mol / min.

[0076] Example 7 The method for synthesizing trioxane in this embodiment is as follows:

[0077] The method for synthesizing trioxane in this embodiment is as follows: The condensation water circulation system was opened, and the water temperature was preheated to about 65°C to establish the water circulation cooling system. 600g of formaldehyde aqueous solution-5 was added to the reaction kettle (four-necked flask), the temperature of the reaction kettle was controlled at 106.35°C, the reaction pressure was 0.3MPa, and the overhead temperature was 102°C. The acid catalyst (sulfuric acid) was added to the four-necked flask 3. The catalytic aid was dissolved in water to obtain a catalytic aid aqueous solution. After refluxing for 1h, the volume reflux ratio was adjusted to 2.0:1, at which time the catalytic product was evaporated from the top of the column, and then the formaldehyde aqueous solution-5 was continuously added to the reaction kettle through a peristaltic pump to keep the liquid level in the reaction kettle constant. After continuous reaction for 5h, the reaction was stopped. The catalytic aid is sodium benzenesulfonate and sodium methanesulfonate with a mass ratio of 1:4.0; The amount of the acid catalyst is 0.6 mol and the amount of the catalytic aid is 0.5 mol relative to 1 kg of the formaldehyde aqueous solution; The concentration of the catalytic aid in the catalytic aid aqueous solution is 26.9 wt%; The adding rate of the catalytic aid is 0.12 mol / min.

[0078] Example 8 The amount of the acid catalyst is 0.6 mol and the amount of the catalytic aid is 0.5 mol relative to 1 kg of the formaldehyde aqueous solution;

[0079] That is, the method for synthesizing trioxane in the embodiment is as follows: The condensation water circulation system is opened, and the water temperature is preheated to about 65℃ to establish the water circulation cooling system; 600 g of the formaldehyde aqueous solution-5 is added into the reaction kettle (a four-necked flask), the temperature of the reaction kettle is controlled to be 101.75℃, the reaction pressure is 0.1 MPa, and the top temperature is 98℃; The acid catalyst (sulfuric acid) is added into the four-necked flask 3; The catalytic aid is dissolved in water to obtain a catalytic aid aqueous solution; After sufficient reflux for 1 h, the volume reflux ratio is adjusted to be 2.0:1, at this time, the catalytic product is evaporated from the top, and then the formaldehyde aqueous solution-5 is continuously added into the reaction kettle through the peristaltic pump to keep the liquid level in the reaction kettle constant. After continuous reaction for 5 h, the reaction is stopped; The catalytic aid is sodium benzenesulfonate and sodium methanesulfonate with a mass ratio of 1:0.31; The amount of the acid catalyst is 1.0 mol and the amount of the catalytic aid is 0.5 mol relative to 1 kg of the formaldehyde aqueous solution; The concentration of the catalytic aid in the catalytic aid aqueous solution is 26.9 wt%; The adding rate of the catalytic aid is 0.12 mol / min.

[0080] Example 9 The amount of the acid catalyst is 0.6 mol and the amount of the catalytic aid is 0.5 mol relative to 1 kg of the formaldehyde aqueous solution;

[0081] That is, the method for synthesizing trioxane in the embodiment is as follows: The condensation water circulation system is opened, and the water temperature is preheated to about 65℃ to establish the water circulation cooling system; 600 g of formaldehyde aqueous solution-5 was added into the reaction kettle (four-necked flask), the temperature of the reaction kettle was controlled at 101.75 ℃, the reaction pressure was 0.1 MPa, and the overhead temperature was 97.8 ℃; The acid catalyst (sulfuric acid) was added into the four-necked flask 3; The catalytic aid was dissolved in water to obtain a catalytic aid aqueous solution; After refluxing for 1 h, the volume reflux ratio was adjusted to 2.0:1, at this time the catalytic product was evaporated from the overhead, and then formaldehyde aqueous solution-5 was continuously added into the reaction kettle through a peristaltic pump to keep the liquid level in the reaction kettle constant. After continuous reaction for 5 h, the reaction was stopped; The catalytic aid was sodium benzenesulfonate and sodium methanesulfonate with a mass ratio of 1:0.31; The amount of the acid catalyst was 0.6 mol and the amount of the catalytic aid was 1.5 mol with respect to 1 kg of formaldehyde aqueous solution; The concentration of the catalytic aid in the catalytic aid aqueous solution was 26.9 wt%; The addition rate of the catalytic aid was 0.12 mol / min.

[0082] Comparative Example 1 According to the similar method of Example 5, except that the amount of formaldehyde aqueous solution-5 was kept unchanged, the amount of the acid catalyst was adjusted to 0.1 mol with respect to 1 kg of formaldehyde aqueous solution, and the rest were the same.

[0083] Comparative Example 2 According to the similar method of Example 6, except that the amount of formaldehyde aqueous solution-5 was kept unchanged, the amount of the catalytic aid was adjusted to 0.1 mol with respect to 1 kg of formaldehyde aqueous solution, and the rest were the same.

[0084] Test Example The contents of trioxane, formaldehyde and formic acid in the catalytic product obtained in the example were determined, and the conversion rate of formaldehyde, the selectivity and yield of trioxane were calculated, and the results are shown in Table 1 and Table 2, respectively.

[0085] The test methods involved are as follows: The contents of trioxane and formaldehyde: according to the gas chromatography method, 1 microliter syringe was used to extract the product into the gas chromatograph 7890B equipped with FID monitor, workstation and Wax chromatographic column to test.

[0086] The content of formic acid: according to the titration method, 0.1 mol / L NaOH solution was used to titrate to the end point color under the bromothymol blue indicator to test.

[0087] The calculation formula involved is as follows: Conversion rate of formaldehyde (mol%) = (initial formaldehyde added - residual formaldehyde after reaction) / initial formaldehyde added; Selectivity of trioxane (mol%) = generated trioxane / (initial formaldehyde added - residual formaldehyde after reaction) x 3; Yield of trioxane (mol%) = generated trioxane / initial formaldehyde added.

[0088] Table 1

[0089] Note: "ppm" refers to mass concentration.

[0090] Table 2

[0091] From the above results, it can be seen that in Examples 1 to 9, in the same catalytic reaction, the conversion rate of formaldehyde reaches more than 46 mol%, the selectivity of trioxane reaches more than 90 mol%, and the yield of trioxane reaches more than 44 mol%. This shows that the composition for synthesizing trioxane provided by the present application, when applied to the synthesis of trioxane, not only can improve the conversion rate of formaldehyde, but also can improve the selectivity of trioxane, and the effect is significantly improved compared with the prior art; at the same time, the method for synthesizing trioxane provided by the present application greatly reduces the content of formic acid.

[0092] In particular, from the experimental data of the examples, it can be seen that after a longer reaction time, the effect of the catalytic aid still exists, which shows that the composition for synthesizing trioxane provided by the present application will not decompose at the reaction temperature, nor will it volatilize into the gas phase product. Therefore, the composition for synthesizing trioxane provided by the present application can be operated for a long period of time, and always has a good effect, and the reaction time is not limited to 72 h.

[0093] The above describes the preferred embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application, and fall within the protection scope of the present application.

Claims

1. A composition for use in the trimerization of formaldehyde, characterized in that, The composition comprises an aqueous formaldehyde solution, an acid catalyst and a catalytic auxiliary agent; In the aqueous formaldehyde solution, the content of formaldehyde is 28-75 wt%, the content of methanol is 0.5-3 wt%, and the content of formic acid is 0.02-0.5 wt%. The acid catalyst is sulfuric acid with a concentration of not less than 90 wt%. The content of the acid catalyst is 0.3-1.0 mol and the content of the catalytic auxiliary agent is 0.3-2.0 mol per 1 kg of the aqueous formaldehyde solution.

2. The composition of claim 1, wherein, The catalytic auxiliary agent is sodium benzenesulfonate and / or sodium methanesulfonate.

3. The composition of claim 2, wherein, The catalytic auxiliary agent is sodium benzenesulfonate and sodium methanesulfonate with a mass ratio of 1:0.3-3.

85.

4. The composition according to any one of claims 1 to 3, characterized in that, The content of the acid catalyst is 0.6-0.8 mol per 1 kg of the aqueous formaldehyde solution.

5. The composition according to any one of claims 1 to 3, wherein The content of the catalytic auxiliary agent is 0.5-1.0 mol per 1 kg of the aqueous formaldehyde solution.

6. The composition according to any one of claims 1 to 3, wherein The catalytic auxiliary agent is provided in the form of an aqueous catalytic auxiliary agent solution, and the concentration of the catalytic auxiliary agent in the aqueous catalytic auxiliary agent solution is 25-30 wt%.

7. A process for the synthesis of parformaldehyde, characterized in that, The method is performed using the composition for trimerization of formaldehyde according to any one of claims 1-6, and comprises: performing catalytic reaction of the components in the composition under catalytic conditions.

8. The method of claim 7, wherein, The operation of performing catalytic reaction of the components in the composition under catalytic conditions comprises: adding the catalytic auxiliary agent to the aqueous formaldehyde solution in the presence of the acid catalyst to perform catalytic reaction.

9. The method of claim 8, wherein, The addition rate of the catalytic auxiliary agent is 0.1-0.2 mol / min per 1 mol of the aqueous formaldehyde solution.

10. The method of claim 7, wherein, The catalytic reaction is performed under reflux conditions.

11. The method of claim 10, wherein, The volume reflux ratio of the reflux conditions is 1-5:

1.

12. The method according to any one of claims 7-11, characterized in that, The reaction temperature of the catalytic reaction is 96-107℃.

13. The method according to any one of claims 7-11, characterized in that, The reaction pressure of the catalytic reaction is 0.1-0.3 MPa.

14. The method according to any one of claims 7-11, characterized in that, The catalytic reaction is performed in a reaction kettle.

15. The method of claim 14, wherein, The overhead temperature of the reaction kettle is 90-123℃.

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