The components and methods for producing trioxane use the same material.

Abstract

DEPCT68 What has been designed is a method that can consistently produce high-yielding trioxanes. Compositions containing (A) 58.5 to 65.5% by mass of formaldehyde, (B) 0.7 to 4.5% by mass of methanesulfonic acid; and (C) less than 0.007% by mass of metal salts in which The total amount of formaldehyde (A) and methanesulfonic acid (B) was less than 68% by mass and Metal salts (C) contain at least one substance chosen from the group of nitrates, nitrites, etc. And persulfate;

Description

Composition and method for producing trioxane using the same

[0001] The present invention relates to a composition and a method for producing trioxane using the same.

[0002] Polyoxymethylene (POM) has excellent strength, elastic modulus, impact resistance, sliding properties, etc., and is therefore widely used in electronic devices, vehicles, etc. as fibers, films, gears, bearings, etc. Demand for polyoxymethylene (POM) is expanding due to its low cost and versatility.

[0003] Demand for trioxane (1,3,5-trioxane, TOX), which is used as a raw material for polyoxymethylene (POM), is also increasing, and therefore a method for producing trioxane (TOX) in high yield is required.

[0004] For example, Patent Document 1 describes an invention relating to a method for producing trioxane, which includes the steps of: 1) contacting formaldehyde with a catalyst containing at least methanesulfonic acid; 2) trimerizing the formaldehyde to trioxane; and 3) separating the trioxane from the reaction medium.

[0005] Patent Document 1 describes that the method for producing trioxane makes it possible to improve the trioxane yield and trioxane selectivity.

[0006] Japanese Patent Application Laid-Open No. 2017-523998

[0007] According to the method described in Patent Document 1, trioxane can be produced in high yield. However, it has been found that continuous production can be difficult because methanesulfonic acid is used.

[0008] Under these circumstances, there is a need for a means for continuously producing trioxane in high yield.

[0009] The present invention includes, for example, the following aspects.

[0010] [1] A composition comprising: (A) 58.5 to 65.5 mass% formaldehyde; (B) 0.7 to 4.5 mass% methanesulfonic acid; and (C) less than 0.007 mass% metal salt, wherein the total content of (A) formaldehyde and (B) methanesulfonic acid is less than 68 mass%, and the (C) metal salt comprises at least one selected from the group consisting of nitrates, nitrites, and persulfates. [2] The composition according to [1] above, wherein the content of (A) formaldehyde is 60 to 65.5 mass%. [3] The composition according to [1] or [2] above, wherein the content of (B) methanesulfonic acid is 0.7 to 3.5 mass%. [4] The composition according to any one of [1] to [3] above, wherein the content of (C) metal salt is 0.002 to 0.004 mass%. [5] A method for producing trioxane, comprising a step of reacting a solution containing (A) formaldehyde, (B) methanesulfonic acid, and (C) a metal salt to obtain trioxane, wherein a reaction solution at equilibrium in the step of obtaining trioxane is the composition according to any one of [1] to [4].

[0011] The present invention provides a means for continuously producing trioxane in high yield.

[0012] Hereinafter, embodiments of the present invention will be described in detail.

[0013] <Composition> The composition of the present invention contains (A) 58.5 to 65.5 mass% formaldehyde, (B) 0.7 to 4.5 mass% methanesulfonic acid, and (C) less than 0.007 mass% metal salt. The total content of (A) formaldehyde and (B) methanesulfonic acid is less than 68 mass%. The (C) metal salt contains at least one selected from the group consisting of nitrates, nitrites, and persulfates.

[0014] The composition allows for continuous production of trioxane in high yield.

[0015] Specifically, by using (B) methanesulfonic acid as the acid catalyst, trioxane can be produced in high yield.

[0016] On the other hand, the use of (B) methanesulfonic acid may make continuous production difficult. Specifically, (B) methanesulfonic acid is corrosive to metals and may corrode metal (e.g., stainless steel (SUS)) equipment (e.g., piping) used in continuous production (especially industrial production, large-scale production). As a result, continuous production may be hindered. Furthermore, since methanesulfonic acid is a strong acid, (A) formaldehyde may be polymerized in the presence of (B) methanesulfonic acid and converted to paraformaldehyde or the like. Paraformaldehyde or the like may adhere to and deposit on piping or the like, causing blockage, which may hinder continuous production.

[0017] However, the composition of the present invention enables continuous production of trioxane. Specifically, by using a predetermined (C) metal salt, a protective film is formed on the surface of metal equipment, preventing corrosion of the metal equipment. Furthermore, by controlling the contents of (A) formaldehyde, (B) methanesulfonic acid, and (C) metal salt in the composition within a predetermined range, the production of paraformaldehyde and the like can be suppressed. As a result, corrosion of metal equipment and clogging of piping and the like can be prevented during continuous production, allowing for favorable continuous production.

[0018] Trioxane is produced by the trimerization reaction of formaldehyde, which is an equilibrium reaction. The term "composition" as used herein refers to a reaction solution at equilibrium in the reaction. When the reaction solution at equilibrium has the composition of the composition of the present invention, trioxane can be continuously produced in high yields, and corrosion of metal equipment and clogging of piping, etc., can be prevented during continuous production.

[0019] As used herein, "at equilibrium" refers to the point at which no change in the composition of the reaction solution is observed after the conditions are fixed. For example, in the continuous production of trioxane, when (A) formaldehyde is added in one lump, the content of (A) formaldehyde in the reaction solution increases during the addition. In this case, the formaldehyde content gradually decreases as formaldehyde is converted to trioxane, and at a certain point, the formaldehyde content reaches a constant value. The point at which such equilibrium is reached is the equilibrium, and the reaction solution at this equilibrium is the composition of the present invention. Furthermore, for example, when a constant amount of trioxane is continuously distilled off, the trioxane produced is sequentially distilled off, and the trioxane content in the reaction solution gradually decreases, resulting in a transition to new equilibrium conditions that assume the continuous distillation of trioxane. In this case, at a certain point, the formaldehyde content reaches a constant value. The point at which equilibrium is reached under such new equilibrium conditions is the equilibrium, and the reaction solution at this equilibrium is the composition of the present invention. The composition of the composition (reaction solution) can be measured by the following method. That is, the content of (A) formaldehyde can be measured by neutralizing titration with an acid of sodium hydroxide produced by reacting with sodium sulfite, while the content of (B) methanesulfonic acid and the content of (C) metal salt can be measured by ion chromatography.

[0020] The composition of the composition according to the present invention (the composition of the reaction solution at equilibrium) can be adjusted, for example, by changing the reaction conditions, adding (A) formaldehyde, adding (B) methanesulfonic acid, adding (C) a metal salt, or by distilling off the trioxane that is produced.

[0021] [(A) Formaldehyde] Formaldehyde is trimerized by the action of an acid to form trioxane.

[0022] The formaldehyde content is 58.5 to 65.5% by mass, preferably 60 to 65.5% by mass, and from the viewpoint of achieving a higher yield of trioxane, more preferably 62 to 65.5% by mass, and even more preferably 62 to 65% by mass, based on the total mass of the composition. A formaldehyde content of 58.5% by mass or more is preferred because trioxane can be produced in high yield. On the other hand, a formaldehyde content of 65.5% by mass or less is preferred because clogging of piping and the like due to the generation of paraformaldehyde and the like can be prevented.

[0023] Since formaldehyde is a gas, raw materials used to produce the composition include an aqueous formaldehyde solution (formalin), paraformaldehyde (formaldehyde oligomer), polyoxymethylene (formaldehyde polymer), etc. As the composition is preferably a solution containing water and / or an organic solvent as described below, formaldehyde is present in the composition as a solution dissolved in water and / or an organic solvent.

[0024] (B) Methanesulfonic Acid Methanesulfonic acid promotes the conversion of formaldehyde to trioxane.

[0025] The content of methanesulfonic acid is 0.7 to 4.5% by mass, preferably 0.7 to 3.5% by mass, based on the total mass of the composition, from the viewpoint of achieving a higher yield of trioxane, and more preferably 0.7 to 2.5% by mass, from the viewpoint of preventing clogging of piping and the like due to the generation of paraformaldehyde and the like. A methanesulfonic acid content of 0.7% by mass or more is preferred because trioxane can be produced in high yield. On the other hand, a methanesulfonic acid content of 4.5% by mass or less is preferred because clogging of piping and the like due to the generation of paraformaldehyde and the like can be prevented.

[0026] The total content of (A) formaldehyde and (B) methanesulfonic acid is less than 68% by mass, preferably 50% by mass or more but less than 68% by mass, more preferably 58 to 67.5% by mass, and even more preferably 60 to 66.5% by mass, based on the total mass of the composition. A total content of less than 68% by mass is preferred because it can prevent clogging of piping and the like due to the generation of paraformaldehyde and the like.

[0027] The mass ratio (A / (A+B)) of the content of (A) formaldehyde to the total content of (A) formaldehyde and (B) methanesulfonic acid is preferably 0.900 to 0.995, more preferably 0.930 to 0.995, even more preferably 0.950 to 0.990, still more preferably 0.955 to 0.990, and even more preferably 0.970 to 0.985. A mass ratio within the above range is preferable because trioxane can be produced in high yield and clogging of piping and the like due to the generation of paraformaldehyde and the like can be prevented.

[0028] [Other Acids] The composition according to the present invention may contain other acids. Here, "other acids" refers to acids other than (B) methanesulfonic acid.

[0029] The other acid is not particularly limited, but examples thereof include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, 1,5-naphthalenedisulfonic acid, etc. These other acids may be used alone or in combination of two or more.

[0030] The content of the other acid is preferably 0.1 to 10% by mass, more preferably 0.1 to 3% by mass, and even more preferably 0.3 to 1% by mass, relative to the total mass of the composition. When two or more types of other acids are contained, the total content thereof is preferably within the above range.

[0031] [(C) Metal Salt] The metal salt forms a protective film on the metal surface of the pipe, etc., and prevents metal corrosion caused by methanesulfonic acid. In this specification, "metal" means iron, steel, and non-ferrous metals, preferably stainless steel (SUS) and carbon steel, and more preferably stainless steel (SUS).

[0032] The metal salt includes at least one selected from the group consisting of nitrates, nitrites, and persulfates.

[0033] The nitrate is not particularly limited, but examples thereof include sodium nitrate, potassium nitrate, magnesium nitrate, cerium nitrate, ammonium cerium nitrate, iron nitrate, molybdenum nitrate, and vanadium nitrate.

[0034] The nitrite is not particularly limited, but examples thereof include sodium nitrite, potassium nitrite, magnesium nitrite, cerium nitrite, ammonium cerium nitrite, iron nitrite, molybdenum nitrite, and vanadium nitrite.

[0035] The persulfate is not particularly limited, but examples thereof include sodium persulfate, potassium persulfate, magnesium persulfate, cerium persulfate, ammonium cerium persulfate, iron persulfate, molybdenum persulfate, and vanadium persulfate.

[0036] Among these, the metal salt preferably contains at least one selected from the group consisting of nitrates and nitrites, more preferably contains a nitrate, further preferably contains at least one selected from the group consisting of sodium nitrate, potassium nitrate, magnesium nitrate, cerium nitrate, and ammonium cerium nitrate, and particularly preferably contains sodium nitrate and / or potassium nitrate. The above-mentioned metal salts may be used alone or in combination of two or more.

[0037] The content of the metal salt is less than 0.007% by mass, preferably 0.0001 to 0.0065% by mass, more preferably 0.001 to 0.006% by mass, and even more preferably 0.002 to 0.004% by mass, relative to the total mass of the composition, from the viewpoint of preventing clogging of pipes, etc. due to the generation of paraformaldehyde, etc. A metal salt content of less than 0.007% by mass is preferred because clogging of pipes, etc. due to the generation of paraformaldehyde, etc. can be prevented.

[0038] [Water] The composition according to the present invention preferably contains water. When the composition contains water, (A) formaldehyde can be dissolved. This makes it possible to prevent clogging of pipes and the like due to the production of paraformaldehyde and the like. Furthermore, when the composition contains water, trioxane and water form an azeotropic mixture (trioxane:water=70:30 (mass ratio), azeotropic point: 91.3°C), and trioxane can be distilled off from the reaction system. This makes it possible to shift the equilibrium reaction converting formaldehyde to trioxane toward the production of trioxane.

[0039] The water content is preferably 20 to 40% by mass, more preferably 30 to 40% by mass, and even more preferably 35 to 40% by mass, based on the total mass of the composition. A water content of 20% by mass or more is preferred because it allows formaldehyde to be suitably dissolved and prevents clogging of piping and the like due to the generation of paraformaldehyde and the like. On the other hand, a water content of 40% by mass or less is preferred because it allows trioxane to be produced in high yield.

[0040] [Organic Solvent] The composition of the present invention may contain an organic solvent. The organic solvent can suitably dissolve formaldehyde, thereby preventing the production of paraformaldehyde and the like.

[0041] [Trioxane] The composition according to the present invention is a reaction liquid at equilibrium, and therefore usually contains trioxane.

[0042] The content of trioxane is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total mass of the composition.

[0043] [Additives] The composition according to the present invention may contain additives. Examples of such additives include, but are not limited to, antifoaming agents, surfactants, stabilizers, etc. These additives may be used alone or in combination of two or more.

[0044] [Combination of Contents] The preferred contents of (A) formaldehyde, (B) methanesulfonic acid, and (C) metal salt contained in the composition are as described above, and they can be combined as appropriate.

[0045] In one embodiment, from the viewpoint of suitably obtaining the effects of high-yield trioxane production, prevention of clogging of piping and the like due to the generation of paraformaldehyde and the like, and prevention of metal corrosion, a preferred combination of the contents of (A), (B), and (C) in the composition is preferably 59 to 65 mass%, (A) 0.5 to 2.5 mass%, and (C) 0.002 to 0.004 mass%, with the total content of (A) formaldehyde and (B) methanesulfonic acid being 60 to 66 mass%, and more preferably 60 to 64 mass%, (B) 1 to 2 mass%, and (C) 0.002 to 0.004 mass%, with the total content of (A) formaldehyde and (B) methanesulfonic acid being 61 to 66 mass%. In another embodiment, from the viewpoint of suitably obtaining a high yield of trioxane, a preferred combination of the contents of (A) to (C) in the composition is preferably 62 to 65 mass% of (A), 0.5 to 3.5 mass% of (B), and 0.002 to 0.004 mass% of (C), with the total content of (A) formaldehyde and (B) methanesulfonic acid being 64 to 67 mass%, and more preferably 63.5 to 65 mass% of (A), 1 to 3 mass% of (B), and 0.002 to 0.004 mass% of (C), with the total content of (A) formaldehyde and (B) methanesulfonic acid being 65 to 67 mass%.

[0046] <Method for Producing Trioxane> According to one embodiment of the present invention, there is provided a method for producing trioxane. The method for producing trioxane includes a step of reacting a solution containing (A) formaldehyde, (B) methanesulfonic acid, and (C) a metal salt to obtain trioxane. In this case, the reaction solution at equilibrium in the step of obtaining trioxane is the composition described above. The method for producing trioxane may further include a trioxane purification step.

[0047] [Trioxane Production Step] The trioxane production step is a step of obtaining trioxane by reacting a solution containing (A) formaldehyde, (B) methanesulfonic acid, and (C) a metal salt.

[0048] (Solution) The solution contains (A) formaldehyde, (B) methanesulfonic acid, and (C) a metal salt, and may further contain other acids, water, organic solvents, additives, etc.

[0049] The (A) formaldehyde, (B) methanesulfonic acid, (C) metal salt, other acid, water, organic solvent, additives, etc., are those described above.

[0050] The contents of (A) formaldehyde, (B) methanesulfonic acid, and (C) metal salt in the solution are preferably amounts that will result in the reaction solution at equilibrium having the above-mentioned composition, taking into consideration the production conditions set in the trioxane production process. The amounts of other acids, water, organic solvents, additives, etc., added may also be appropriately determined.

[0051] (Reaction) (A) Formaldehyde is trimerized in the presence of (B) methanesulfonic acid to produce trioxane. At this time, the trimerization is an equilibrium reaction.

[0052] In addition, by side reactions, formic acid, glycolic acid (CH ２ In this reaction, trioxane (OHCOOH), methanol, and carbon dioxide may be produced. These by-products may react to form further by-products. However, when the reaction solution at equilibrium is adjusted to have the composition of the present invention, the trimerization of formaldehyde can occur more selectively, allowing trioxane to be produced in high yield.

[0053] The reaction method is not particularly limited, and known methods can be used, for example, a method of heating the solution.

[0054] The reaction temperature is not particularly limited, but is preferably 70 to 150° C., more preferably 80 to 120° C., and particularly preferably 90 to 120° C. By adjusting the reaction temperature, the produced trioxane can be distilled out of the reaction system, and trioxane can be obtained in a higher yield.

[0055] The reaction pressure is not particularly limited, but is preferably 0.1 × 10 ５ ~10 x 10 ５ Pa, and preferably 1×10 ５ ~5 x 10 ５ Pa is more preferable, and 1×10 ５ ~2 x 10 ５ It is more preferable that the reaction pressure is 0.05 Pa. By adjusting the reaction pressure, the produced trioxane can be distilled out of the reaction system, and trioxane can be obtained in a higher yield.

[0056] The reaction time is not particularly limited, but is preferably 0.1 to 10 hours, more preferably 0.3 to 5 hours, and even more preferably 0.5 to 4 hours. By adjusting the reaction time, trioxane can be produced efficiently.

[0057] Since the trimerization of formaldehyde is an equilibrium reaction, it is preferable to distill off the product trioxane from the reaction system during the reaction process. For example, when the composition contains water, trioxane forms an azeotropic mixture with water and is distilled off from the reaction system under predetermined reaction conditions.

[0058] The trioxane distilled off (for example, an azeotropic mixture of trioxane and water) is preferably purified as it is in the trioxane purification step described below.

[0059] In the case of continuous production of trioxane, an aqueous formaldehyde solution is successively added to a reaction system containing methanesulfonic acid and a metal salt, and the resulting trioxane is successively distilled off from the reaction system. In this case, the aqueous formaldehyde solution is preferably added in an amount such that the reaction solution at equilibrium has the composition of the composition according to the present invention, taking into consideration the reaction conditions, the amount of trioxane distilled off from the reaction system, and the like.

[0060] [Trioxane Purification Step] The trioxane purification step is a step of purifying the trioxane obtained in the trioxane production step. In this case, the "obtained trioxane" includes trioxane distilled out of the reaction system during the reaction (preferably an azeotropic mixture of trioxane and water) and the reaction solution after the reaction. In this case, the "obtained trioxane" includes, in addition to trioxane, formaldehyde, water, organic solvents, additives, by-products (formic acid, glycolic acid (CH ２ These may include components derived from droplets generated in the reaction system, components derived from piping, etc.

[0061] The purification method is not particularly limited, but examples thereof include distillation, crystallization, filtration, extraction, etc. Among these, the purification method preferably includes distillation and / or extraction, and more preferably includes distillation. Furthermore, the purification method may be any known method as appropriate.

[0062] It is preferable that at least one of the impurities other than trioxane separated in the purification step, such as formaldehyde, water, an organic solvent, etc., is reused in the trioxane production step.

[0063] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0064] Example 1 (Production of Trioxane) A solution containing (A) formaldehyde, (B) methanesulfonic acid, (C) sodium nitrate, and water was introduced into a reactor (having a configuration of reactor - piping (distillation line) - Allen condenser - distillate storage flask - piping (return line) - reactor) connected to two pipes (a distillation line and a return line), and trioxane was produced by heating at a heat medium temperature of 130°C for 3 hours. The content of (A) formaldehyde in the reaction liquid (composition) at equilibrium after 3 hours was measured by neutralizing the methanesulfonic acid and by-product acid components (such as formic acid) in the composition with dilute hydrochloric acid, and then reacting the resulting sodium hydroxide with sodium sulfite, followed by neutralization titration with acid. The contents of (B) methanesulfonic acid and (C) metal salt in the reaction solution (composition) at equilibrium were measured by ion chromatography (instrument name: Dionex ICS-2100, columns: Dionex IonPac AS11-HC and Dionex IonPac AG11-HC). As a result, the contents of (A) were 60% by mass, (B) were 1% by mass, and (C) were 0.003% by mass, relative to the total mass of the composition.

[0065] During this reaction, the trioxane produced in the reaction formed an azeotropic mixture with water and was distilled off from the reaction system. This shifted the equilibrium reaction of trioxane production from formaldehyde toward trioxane production. The azeotropic mixture of trioxane and water was liquefied by cooling in an Allen condenser through a pipe (distillation line) connected to the reactor, and stored as a trioxane distillate in a distillate storage flask connected to the Allen condenser. When the amount of trioxane distillate stored in the distillate storage flask exceeded the capacity of the distillate storage flask, the trioxane distillate in the distillate storage flask was returned to the reactor through a pipe (return line).

[0066] Example 2 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 64 mass %.

[0067] [Example 3] A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 64 mass % and the content of (B) was adjusted to 2 mass %.

[0068] Example 4 A composition was produced in the same manner as in Example 1, except that the content of (B) in the reaction liquid (composition) at equilibrium was adjusted to 3 mass %.

[0069] Example 5 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 64 mass % and the content of (B) was adjusted to 3 mass %.

[0070] Example 6 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 63 mass % and the content of (B) was adjusted to 4 mass %.

[0071] [Example 7] A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 64 mass%, the content of (B) was adjusted to 2 mass%, and the content of (C) was adjusted to 0.005 mass%.

[0072] Example 8 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 63 mass %, the content of (B) was adjusted to 4 mass %, and the content of (C) was adjusted to 0.005 mass %.

[0073] Example 9 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 64 mass%, the content of (B) was adjusted to 2 mass%, and the content of (C) was adjusted to 0.001 mass%.

[0074] Comparative Example 1 A composition was produced in the same manner as in Example 1, except that the content of (B) in the reaction liquid (composition) at equilibrium was adjusted to 0.5% by mass.

[0075] Comparative Example 2 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 64 mass % and the content of (B) was adjusted to 0.5 mass %.

[0076] Comparative Example 3 A composition was produced in the same manner as in Example 1, except that the content of (B) in the reaction liquid (composition) at equilibrium was adjusted to 5% by mass.

[0077] Comparative Example 4 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 66 mass %.

[0078] Comparative Example 5 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 64 mass % and the content of (B) was adjusted to 4 mass %.

[0079] Comparative Example 6 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 58 mass % and the content of (B) was adjusted to 2 mass %.

[0080] Comparative Example 7 A composition was produced in the same manner as in Example 1, except that the content of (B) in the reaction liquid (composition) at equilibrium was adjusted to 2 mass % and the content of (C) was adjusted to 0.01 mass %.

[0081] Comparative Example 8 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 64 mass%, the content of (B) was adjusted to 2 mass%, and the content of (C) was adjusted to 0.01 mass%.

[0082] Comparative Example 9 A composition was produced in the same manner as in Example 1, except that the content of (B) in the reaction liquid (composition) at equilibrium was adjusted to 4 mass % and the content of (C) was adjusted to 0.01 mass %.

[0083] Comparative Example 10 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 64 mass%, the content of (B) was adjusted to 2 mass%, and (C) was not added.

[0084] Comparative Example 11 A composition was produced in the same manner as in Example 1, except that the content of (A) in the reaction liquid (composition) at equilibrium was adjusted to 63 mass %, the content of (B) was adjusted to 4 mass %, and (C) was not added.

[0085] The compositions of Examples 1 to 9 and Comparative Examples 1 to 11 are shown in Table 1 below.

[0086]

[0087] [Evaluation] Various evaluations were carried out on the compositions of Examples 1 to 9 and Comparative Examples 1 to 11 and the trioxane distillates in the distillate storage flasks.

[0088] (Trioxane Content) After the reaction equilibrium was reached (3 hours later), the trioxane distillate was collected from the distillate storage flask, and the trioxane content in the trioxane distillate was measured by gas chromatography. The trioxane content (TOX content) relative to the total mass of the trioxane distillate was calculated. The gas chromatography measurement was performed using a Nexis GC-2030 (Shimadzu Corporation) as the apparatus and a DB-WAX (Agilent Technology) as the column. A high TOX content indicates that trioxane was produced in high yield. The results are shown in Table 2 below.

[0089] (Appearance of Reaction Liquid) After the reaction equilibrium was reached (3 hours later), the reaction liquid (composition) in the reactor was visually observed and the appearance of the reaction liquid was evaluated according to the following criteria. A high evaluation result for the appearance of the reaction liquid indicates that no paraformaldehyde or the like was produced from formaldehyde during the trioxane production process. Therefore, when trioxane is produced using the composition, clogging of piping and the like is unlikely to occur, making it suitable for continuous production. The results obtained are shown in Table 2 below.

[0090] ○: Colorless and transparent △: Slightly cloudy ×: Significantly cloudy

[0091] (Stainless Steel (SUS) Corrosion) After the reaction equilibrium was reached (3 hours later), a SUS316L test piece (length 60 mm, width 20 mm, thickness 2 mm, equipped with weld lines made of the same material on both sides and a φ4 mm drilled through hole) was immersed in 100 g of the reaction solution (composition) in the reactor and left to stand for 1 day at 90° C. The mass loss rate (mass) of the test piece after immersion was calculated using the following formula.

[0092]

[0093] The SUS corrosiveness was evaluated according to the following criteria. A high evaluation result for SUS corrosiveness indicates that the composition is less likely to corrode SUS equipment. The results are shown in Table 2 below.

[0094] ○: Mass reduction rate is less than 0.2 mass% ×: Mass reduction rate is 0.2 mass% or more

[0095]

[0096] The results in Table 2 show that the compositions of Examples 1 to 9 were capable of producing trioxane in high yield, prevented the production of by-products such as paraformaldehyde, and prevented corrosion of SUS. Therefore, the compositions of Examples 1 to 9 were capable of producing trioxane in high yield and were suitable for continuous production.

Claims

DEPCT681. Composition consisting of: (A) 58.5 to 65.5% by mass of formaldehyde; (B) 0.7 to 4.5% by mass of methanesulfonic acid; and (C) less than 0.007% by mass of metal salts, in which the total amount of formaldehyde (A) and methanesulfonic acid (B) is less than 68% by mass and the metal salts (C) contain at least one of which is selected from the group of nitrates, nitrites and persulfates.

2. Composition according to claim 1 in which the amount of formaldehyde (A) is 60 to 65.5% by mass.

3. Composition according to claim 1 or 2.

4. Any of the components in Reputations 1 through 3 in which the amount of metal salt (C) is 0.002 to 0.004% by mass; 5. A method for the production of trioxanes consisting of a trioxane acquisition step by causing a reaction of a solution containing formaldehyde (A), methanesulfonic acid (B), and a metal salt (C) in which the reaction liquid at the time of equilibrium in the trioxane acquisition step is any of the components in Reputations 1 through 4;