JPH01106879A - Production of trioxane - Google Patents

Abstract

PURPOSE:To obtain trioxane from formaldehyde in liquid phase, by using a catalyst having high activity and selectivity and resistant to lowering of activity and selected from zeolite beta, dealuminized zeolite ZSM-20 and dealuminized Y-type zeolite. CONSTITUTION:Trioxane is produced by reacting formaldehyde in liquid phase preferably at 90-130 deg.C in the presence of a catalyst consisting of at least one kind of zeolite selected from zeolite-beta (a zeolite having high silica/alumina ratio), dealuminized zeolite ZSM-20 and dealuminized Y-type zeolite. The process is advantageous from industrial viewpoint because trioxane is produced from formaldehyde in high yield and selectivity with little lowering of the catalytic activity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing trioxane, which is important as a raw material for polyacetal copolymers.

(Prior art and problems to be solved by the invention) Conventionally, trioxane has been produced using a formaldehyde aqueous solution as a raw material and a homogeneous acid such as sulfuric acid or heteropolyacid.
Although they have been produced by heating and distilling, these homogeneous acids have the problem of severe corrosion of equipment. To solve this problem, a heterogeneous reaction method using an ion exchange resin has been proposed.

However, in the case of sulfur exchange resins, there are problems with the mechanical strength and heat resistance of the resin, and in particular, one reaction is usually 90~
To be carried out in a temperature range of 130C.

The deterioration of the ion exchange resin is significant, making it unsatisfactory as an industrial catalyst.

On the other hand, the present inventors first proposed, as a method to solve these problems, a crystalline aluminosilicate (generally called zeolite) with a silica/alumina molar ratio of 10 or more as a catalyst! i-Method used (% 1986-20
3985 specification)). The zeolites shown in the examples of the invention are H-ZSM-5, H
-ZSM-11, H-ZSM-12 developed by Mopil Oil Co., Ltd. are Tomo zeolite and H-mordenite.

These zeolites have very high activity in the trioxane synthesis reaction, and also have extremely excellent heat resistance.

However, as a result of subsequent studies by the present inventors, it was found that even with these zeolites, when used as a catalyst for a long period of time, there is a slight decrease in activity and also a decrease in selectivity. I understand.

(Means for Solving the Problems) The inventors of the present invention have conducted intensive studies to solve all the problems mentioned above, and as a result of using zeolite beta as a catalyst, dealuminated zeolite ZSM-20, When at least one type of zeolite selected from dealuminated Y-type zeolites is used, high activity,
High selectivity and.

We have discovered that the decrease in activity is extremely small and have completed the present invention.

That is, the present invention uses zeolite beta (zeolite beta, dealuminated zeolite) ZSM-
20. A method for producing trioxane using at least one type of zeolite selected from dealuminated fcY type zeolites.

It is not clear why these zeolites have high activity, high selectivity, and little decrease in activity, but the following reasons can be considered.

In ZSM-5 and ZSM-11, the pore entrance in the zeolite structure is a 10-membered oxygen ring and is relatively small, so the pores are narrowed by the precipitation of high-boiling substances, resulting in a decrease in activity 1 selectivity. In addition, ZSM-12 and mordenite have a relatively large oxygen-12 negative ring at the pore entrance, but because the pore structure is a one-dimensional tunnel, activity is likely to decrease due to pore clogging. On the other hand, Y-type zeolite and Z
SM-20 belongs to a zeolite called faujasite, which has 12-membered three-dimensional pores, and zeolite beta is also said to have a pore structure similar to faujasite. The multidimensional pore structure of this 12-membered oxygen ring is
It is thought that this works advantageously against diffusion of the product trioxane and diffusion inhibition due to precipitation of high-boiling substances.

The zeolite beta used in the present invention is a zeolite with a high silica/alumina ratio developed by Mopil Oil (see USP 3.SOB, No. 069).

This zeolite beta is generally obtained by hydrothermal synthesis from a silica source, an alumina source, and an alkali metal source in the presence of tetraethylammonium ions. The silica/alumina molar ratio of zeolite beta is 1, usually 10 to 100.
However, dealumination with hydrochloric acid at high temperature.

Even higher silica/alumina molar ratios can be obtained by dealumination with chelating agents such as EDTA. Preferable silica/alumina molar ratio i-j of zeolite beta used in the present invention: 10 to 100
It is preferably in the range of 0 to 300, more preferably in the range of 20 to 300.

Zeolite Beta has the characteristic X-ray diffraction peaks shown in Table A.

Table A However, CuKa rays are used as the X-rays.

ZSM-20 used in the invention is a zeolite belonging to the faujasite family developed by Mopil Oil Co. (see % 80717/1983). This ZSM-2
0 is generally obtained by hydrothermal synthesis using a silica source, an alumina source, and an alkali metal source in the presence of tetraethylammonium ion, but the silica/alumina molar ratio of ZSM-20 after synthesis is 7 to 10. In this condition.

The activity of this reaction is extremely low. Therefore, it is necessary to increase the silica/alumina molar ratio of ZSM-20 used in the present invention by dealumination treatment. This method of dealumination is as follows.

For example, there is a method of combining steaming and hydrochloric acid treatment as shown in JP-A-58-2081'30.

The preferred silica/alumina molar ratio of dealuminated ZSM-20 in the present invention is 10 to 500. More preferably, it is in the range of 20 to 200.

ZSM-20 has characteristic X-ray diffraction peaks shown in Table 1B.

Table B However, XA61 uses CuKa radiation.

The Y-type zeolite used in the present invention is a zeolite belonging to the faujasite group. This Y-type zeolite can be obtained naturally or by hydrothermal synthesis, but its silica/alumina molar ratio is 3 to 6, and in this state it does not exhibit much activity in a single reaction. Therefore, it is necessary to increase the silica/alumina molar ratio of the YW zeolite used in the present invention by dealumination treatment. As a method for this dealumination, for example, JP-A-58-20
Examples include a method of combining steaming and hydrochloric acid treatment as shown in No. 8130, and a treatment method using silicon tetrachloride gas as shown in JP-A-58-36917. The preferred silica/alumina molar ratio of the dealuminated Y-type zeolite used in the present invention is 10 to 500.
More preferably, it is in the range of 20 to 200.

The zeolite used in the present invention is used in the form of cations, preferably protons, alkaline earth metals, transition metals, and rare earth metals, and 1% preferably protons.

The zeolite beta, dealuminated ZSM-20, and dealuminated Y-type zeolite used in the present invention may be used singly.

May be used in combination.

The trioxane synthesis reaction in the present invention can be carried out in an aqueous formaldehyde solution, an organic solvent, or in a coexistence system of an aqueous formaldehyde solution and an organic solvent.

When performing the reaction in an aqueous formaldehyde solution.

Concentration of formaldehyde aqueous solution used #'i10~a
sh, preferably 20 to 80 sh, more preferably 60
It ranges from 75 cm to 75 cm.

Organic solvents used when carrying out the reaction in an organic solvent include aromatic hydrocarbons such as benzene, toluene, and xylene, C6 to C8 aliphatic hydrocarbons, salts of himethylene, chloroform, chlorobenzene, dichlorobenzene, etc. Examples include halogenated hydrocarbons. When performing anti-Gt in these organic solvents.

For example, the reaction can be carried out using a solution in which paraformaldehyde is dissolved in an organic solvent, or a solution in which pure formaldehyde gas is absorbed.

Furthermore, the single reaction can also be carried out in the presence of an aqueous formaldehyde solution and an organic solvent.

The reaction temperature in the present invention is not particularly limited as long as it can maintain the reaction system in a liquid phase, but it is usually 50 to 200C, preferably 70 to 150C, particularly preferably 90 to 130C.
It is carried out in the temperature range of C.

The pressure in the present invention is not particularly limited as long as it can maintain one reaction system in a liquid phase, and may be reduced pressure, normal pressure, or increased pressure.

The reaction format in the present invention may be either a batch type or a continuous type, but a continuous type is preferred on an industrial scale. In this case, since the single reaction is an equilibrium reaction, a reactive distillation format in which the generated trioxane is continuously extracted from the system is preferred.

The catalyst used in the present invention may be molded and used in the form of a fixed bed, or may be used as a powder in the form of a slurry.

(Effects of the Invention) According to the method of the present invention, formaldehyde caratrioxane gold can be produced with good yield and selectivity, and with little reduction in catalyst activity. This is very advantageous for industrial implementation.

(Example) Next, one embodiment of the present invention will be explained using an example.

Example 1 Synthesis of Zeolite Beta
next.

Silica sol (50i amount% Sin, ) while stirring
415 g was added to obtain a homogeneous gel. This gel was placed in a stainless steel autoclave with an internal volume of 1 ton.

10 min at 150C with stirring at 50 rpm.
Crystallization was carried out for 0 hours. The resulting product is filtered, washed,
After drying at 120C for 5 hours, it was fired in air at 450C for 6 hours. This product was identified as schizeolite peta by X-ray diffraction analysis.

Further, this product i1N was ion-exchanged in hydrochloric acid at room temperature for 4 hours, filtered, washed, and dried at 120C for 5 hours, and the product was analyzed with fluorescent X-rays to give Sio2/AmO.

As a result of measuring the molar ratio, it was 65.

Example 2 Synthesis of dealuminated ZSM-2o 50wt% tetraethylammonium hydroxide 124% NaOH 1,7
f was dissolved and 100r of ethyl silicate was added to obtain a homogeneous gel. Furthermore, Al4(S04')s・
16H and 07S' were dissolved and added to the aqueous solution with stirring to obtain a raw material gel. This gel was placed in a 500cc stainless steel autoclave and heated at 100C for 200 hours.
The crystals were heated while stirring at 200 rpm. Filter the resulting product.

After washing, dry at 120C for 4 hours, and then dry.

Calcined in air at 450C for 4 hours. This product is
It was identified by line diffraction analysis as 928M-20. Briefly, the product was ion-exchanged with a 1N aqueous NH4C4 solution for 24 hours at room temperature, filtered, and washed.

After drying, it was steamed for 2 hours at 400C with water pressure of 20% Hg.

It was treated with 0.5N hydrochloric acid at 80C for 1 hour. After total filtration, purification and drying of this product, the SiO,/Am08 molar ratio determined by fluorescent X-ray analysis was 75.

Example 3 On commercially available Yfi zeolite (Linde 5K-40).

N containing 5 volumes of SiC, gas 1sV = 1000
hr-'.

Dealumination was carried out by flowing at 450C for 2 hours.

The obtained product was ion-exchanged with a 1N aqueous NH4C6 solution for 24 hours at room temperature, filtered, washed, dried at 120C for 4 hours, and then calcined at 400 G in air for 4 hours. Determined from fluorescent X-ray analysis of the desired product fc 5iO1/
Ago, %/l/ratio is 35 and ivy.

Example 4 Using the zeolite beta obtained in Example 1, the dealuminated ZSM-20° obtained in Example 2 and the dealuminated Y-type zeolite obtained in Example 3 as catalysts, The trioxane synthesis reaction from an aqueous formaldehyde solution was carried out under the following conditions.

Residence time = 20 minutes Temperature: 102C A pressure crab normal pressure reaction type two continuous reaction distillation type reactor is shown in the drawing. In the drawing, 1 is an oil bath, 2 is a bonder, 5 is a pipe, 4 is a mantle heater, 5
6 is a three-way flask, 6 is a vacuum jacket provided on flask 5, 7 is a thermometer, 8 is a rotor, and 9 is a magnetic stirrer.

10 is a cooler, 11 is a receiver, and 12 is formalin.

13 is a reactor, 14 is a product, and 15 is a liquid level sensor.

2 to 3 hours, 100 to 101 hours after the start of the reaction.

Table 1 shows the eluate compositions for 300 to 301 hours and 700 to 701 hours.

Table 1 Comparative Example 1 ZSM-5 synthesized according to USP 5,702,886 was calcined in air at 500C for 5 hours, and then ion-exchanged in IN hydrochloric acid for 4 hours at room temperature.
H-ZSM-5i was obtained. The fc Si Ot / A40s molar ratio determined by fluorescent X-ray analysis of C0H-Z 5M-5 was 60.

Using this H-zsa-st-, a reaction was carried out under the same conditions as in Example 3.

The results are shown in Table 2.

Table 2 Comparative Example 2 High silica mordenai manufactured by Toyo Soda Co., Ltd. (TSZ680)
, Sin, /A! 40s molar ratio = 55),
The reaction was carried out under the same conditions as in Example 3.

The results are shown in Table 3.

Table 3 Example 5 Using the zeolite beta obtained in Example 1 as a catalyst,
A trioxane synthesis reaction from an aqueous formaldehyde solution in the coexistence of benzene was carried out under the following conditions.

Raw material formalin concentration: 5% by weight Formalin supply rate: 200C/hr Hensen supply rate: 140 CC;/hr Reaction catalyst concentration: 1. ON'jk% Reaction temperature: 120'C Residence time: 20 minutes Stirring rotation speed: 6oorpm Reaction format: Liquid phase flow reaction (completely mixed type) The catalyst was separated by a filter at the outlet of the reaction tank, and the results are shown in Table 4.

Table 4

[Brief explanation of the drawing]

The drawing is an explanatory diagram of a reaction apparatus used in the trioxane synthesis reaction of Example 4.

Claims (1)

[Claims] When producing trioxane from formaldehyde in a liquid phase, at least one zeolite selected from zeolite beta, dealuminated zeolite ZSM-20, and dealuminated Y-type zeolite is used as a catalyst. A method for producing trioxane.