JPH0733343B2 - Formaldehyde production method - Google Patents

Description

The present invention relates to a method for producing formaldehyde by dehydrogenating methanol in the gas phase in the presence of a catalyst. More specifically, the present invention relates to a method of using silica gel supporting metallic copper as a dehydrogenation catalyst, wherein methanol is dehydrogenated in the presence of a catalyst composed of copper-silica gel to produce formaldehyde in a high yield. Regarding the method.

[Conventional technology and problems]

As a method for industrially producing formaldehyde, a catalytic oxidation dehydrogenation method or a catalytic oxidation method of methanol is generally known. However, since these methods produce a large amount of water as a by-product, formaldehyde is obtained as an aqueous solution of about 40% by weight, which requires a purification step.

On the other hand, many methods have been proposed for the production of formaldehyde by so-called dehydrogenation of methanol.
For example, a method using a catalyst composed of copper, zinc and selenium (Japanese Patent Laid-Open No. 52-215), a method using synthetic mica (Japanese Patent Laid-Open No. 59-48429) and the like have been proposed. However, the former method has a drawback that the reaction temperature is high, and the latter method has a low conversion rate, and cannot be said to be a satisfactory method.

[Means for solving problems]

The inventors of the present invention have made diligent studies to improve the above-mentioned problems, to produce a catalyst having higher activity and higher selectivity without generating water, and various metals, carriers, preparation methods, and further As a result of repeated research on reaction conditions, the present invention has been completed.

That is, the present invention relates to a method for producing formaldehyde, which comprises dehydrogenating methanol in the presence of a metallic copper catalyst supported on silica gel.

The raw material of the catalyst in the present invention, copper acetate, copper oxalate, copper salts such as copper nitrate are used as a copper source, silica gel is represented by the general formula SiO ₂ · nH ₂ O, powder, granular It does not matter which of the above.

The method for preparing the catalyst in the present invention is such that silica gel is fired at a high temperature of about 600 to 900 ° C. in advance, an aqueous solution of a copper salt or an organic solvent solution is added thereto, and impregnated with 0.1 to 6.7% by weight of copper and prepared by thermal decomposition. To do.

The dehydrogenation reaction method of methanol in the present invention, for example, put the impregnated catalyst in a reaction vessel, 200 ~ 500 in an inert gas.
After decomposing the copper salt at ℃, the reaction temperature is set and methanol is introduced. Further, higher activity can be obtained by performing hydrogen reduction at the same temperature as the decomposition after the decomposition of the copper salt. The reaction temperature is
The temperature is 400 to 650 ° C, preferably 450 to 550 ° C. 400
At temperatures lower than ℃, the activity is low, and at temperatures higher than 650 ℃, the selectivity of formaldehyde decreases. The supply amount of methanol is preferably 0.005 to 0.40 mol / hour per 1 g of the catalyst.

The result of the reaction according to the present invention is that the conversion of methanol is 6-36.
%, The formaldehyde selectivity was 75 to 85%. Other by-products include carbon monoxide, carbon dioxide, and methane, and their selectivity is 7.4-9.5%, 0-1.8%, 5-14%, respectively.
Met. Further, the water content in the product was extremely low at 0.5 to 2% by weight.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
The invention is not limited to these examples.

Example 1 <Preparation of catalyst> Silica gel (manufactured by Kokusan Kagaku Co., Ltd., silica gel) in air was used.
It was baked at 0 ° C. The copper acetate solution was prepared by dissolving 6.2 g of copper acetate in 250 ml of water. 7 ml of a copper acetate solution was added to 10 g of silica gel and well stirred. After leaving it for 24 hours, it was dried in a hot water bath. Further, 6 ml of a copper acetate solution was added, the mixture was allowed to stand for 24 hours, dried repeatedly, and a total of 25 ml of a copper acetate solution was added to prepare the solution.
The amount of copper supported was 1.9% by weight.

<Reaction> 1 g of the above catalyst is charged into a reactor. Then this in He (30
Pretreatment for 2 hours at 300 ℃. Then the temperature is 500 ℃
And methanol was introduced at a flow rate of 0.12 mol / hour.
When the product after 6 hours was analyzed, the conversion of methanol was 21.3% and the selectivity of formaldehyde was 80%. In addition to formaldehyde, carbon monoxide, carbon dioxide,
Methane was produced with selectivity of 8.4%, 0.9% and 11.1%, respectively.

Example 2 The same catalyst as in Example 1 is used, and 1 g of this catalyst is charged into a reactor. Then, pre-treat this in He (30 ml / min) at 300 ℃ for 2 hours, and then flow a mixed gas of He and H ₂ (2: 1, 30 ml / min) at 300 ℃
Perform time reduction. After that, stop H ₂ and in He (30ml / min)
The temperature was raised to 500 ° C., and methanol was introduced at a flow rate of 0.12 mol / hour. Analysis of the product after 6 hours showed a methanol conversion of 33.2% and a formaldehyde selectivity of 77.
%Met. In addition to formaldehyde, carbon monoxide, carbon dioxide, and methane were produced with selectivity of 9.4%, 1.8%, and 11.8%, respectively.

Example 3 Using the same catalyst as in Example 1, the reaction was carried out under the same conditions as in Example 1, except that the flow rate of methanol was changed to 0.06 mol / hour. When the product after 6 hours was analyzed, the conversion of methanol was 27.4% and the selectivity of formaldehyde was 75.4%. In addition to this, carbon monoxide, carbon dioxide, and methane were produced at the selectivities of 9.5%, 1.3%, and 13.8%, respectively.

Example 4 <Preparation of catalyst> A catalyst having a copper loading of 0.3% by weight was prepared in the same manner as in Example 1.

<Reaction> As a result of reaction using the above catalyst under the same conditions as in Example 1, the conversion of methanol was 7.0% and the selectivity of formaldehyde was 83.2%.

In addition to this, carbon monoxide, carbon dioxide, and methane are 7.
It was generated with the selectivity of 8%, 0.2% and 8.7%.

Example 5 <Preparation of catalyst> Silica gel (manufactured by Kokusan Kagaku Co., Ltd., silica gel) in air was used.
It was baked at 0 ° C. The copper nitrate solution was prepared by dissolving 10 g of copper nitrate in 250 ml of water. 6 ml of a copper nitrate solution was added to 10 g of silica gel, stirred well, allowed to stand for 24 hours, and then dried on a hot water bath. This operation was repeated and a total of 18 ml of copper nitrate solution was added. The amount of copper supported was 1.9% by weight.

<Reaction> As a result of reaction using the above catalyst under the same conditions as in Example 1, the conversion of methanol was 16.8% and the selectivity of formaldehyde was 78.4%. In addition, carbon monoxide, carbon dioxide, methane, and diethyl ether were 8.1% and 1.1%, respectively.
%, 11.5%, and 1.0% were selected.

Claims (1)

[Claims] 1. A method for producing formaldehyde, which comprises dehydrogenating methanol in the presence of a metallic copper catalyst supported on silica gel.