Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1997-04-24
1999-10-05
Richter, Johann
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
549367, C07D32306, C07D32304
Patent
active
059627026
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for producing trioxane by cyclizing formaldehyde to convert it into a cyclic trimer. More particularly, the present invention relates to a process for producing trioxane by contacting an aqueous formaldehyde solution with an acidic catalyst, wherein the concentrations of methanol and formic acid present in the reaction system are each controlled and wherein the amounts of by-products formed are small.
BACKGROUND ART
Trioxane has been produced by cyclizing formaldehyde in its aqueous solution in the presence of an acidic catalyst such as sulfuric acid, cation exchange resin having a sulfonic acid group, zeolite or the like.
These conventional processes for trioxane production have not been satisfactory because of various problems such as corrosion of production equipment, precipitation of paraformaldehyde at high formaldehyde concentration, low trioxane selectivity and the like. For example, when a sulfuric acid catalyst is used, there is a problem of equipment corrosion by strong acid and it is necessary to use an expensive material(s) for equipment to prevent the problem. When a cation exchange resin having a sulfonic acid group is used as a catalyst, there are problems such as low trioxane selectivity, paraformaldehyde precipitation and consequent pressure loss of catalyst layer, and the like. Meanwhile, it is well known that increased methanol concentration in reaction system is effective for the prevention of paraformaldehyde precipitation in aqueous formaldehyde solution. Increased methanol concentration in reaction system, however, invites formation of larger amounts of by-products such as methyl formate, dioxymethylene dimethoxide, trioxymethylene dimethoxide and the like, which is undesirable. JP-A-59-134789 discloses that trioxane selectivity is higher when a macroreticular cation exchange resin having a sulfonic acid group is used and the concentration of formic acid is controlled at 0.025-15.0 wt. %. The concentration of formic acid in this literature, however, refers to a formic acid concentration in raw materials mixture fed into reactor, i.e. a formic acid concentration before start of reaction and is not a formic acid concentration in reaction system during reaction. Incidentally, too high a formic acid concentration causes equipment corrosion by formic acid.
DISCLOSURE OF INVENTION
The present invention is intended to provide a process for producing trioxane by contacting an aqueous formaldehyde solution with an acidic catalyst, wherein the corrosion of equipment material(s) is very low, the amounts of by-products formed are small, and trioxane can be produced efficiently.
In order to solve the above-mentioned problems of the prior art, the present inventors eagerly made a study. As a result, the present inventors surprisingly found out a process for production of trioxane wherein the equipment corrosion is prevented and the amounts of by-products formed, i.e. dioxymethylene dimethoxide and trioxymethylene dimethoxide are reduced by controlling the methanol concentration and formic acid concentration in the reaction system and the concentration ratio of methanol to formic acid in synthesis of trioxane in the presence of an acidic catalyst. The finding has led to the completion of the present invention.
The present invention provides a process for producing trioxane by contacting an aqueous formaldehyde solution with an acidic catalyst, wherein the concentrations of methanol and formic acid present in the reaction system are controlled each at 0.5-5 wt. % and the concentration of methanol in terms of wt. % is controlled so as not to exceed two times the concentration of formic acid in terms of wt. %.
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, an aqueous formaldehyde solution is used as a raw material. The formaldehyde concentration in said solution is generally 30-80 wt. %, preferably 60-75 wt. %. The aqueous formaldehyde solution as raw material may contain methanol, methylal, formic acid, methyl fo
REFERENCES:
patent: 4967014 (1990-10-01), Masamoto et al.
European Search Report for European Application No. EP 95934875.6, Dec. 1995, p. 1-2.
Chemical Abstracts, 1993, vol. 118, No.25, p. 892.
Chemical Abstracts, 1991, vol. 115, No. 28, p. 947
Asahi Kasei Kogyo Kabushiki Kaisha
Keating Dominic
Richter Johann
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