KR860000871B1 - Process for producing formaldehyde - Google Patents

Abstract

Formaldehyde was produced by the catalytic oxidn. and dehydrogenation of MeOH by air in the presence of Ag-Pd catalyst. Ag-Pd catalyst contained 10 ppm - 5 wt.% or 50 - 10,000 ppm of Pd. The rxn. was performed at a supply rate of 0.3 - 2.5 MT/hr of MeOH per 1 m3 of catalyst and at an air mixing raio of 1.1 - 2.7 mole to one mole of MeOH at 500 - 750≰C. The mixing ratio of vapour is 0.3 - 1.5:1 by mole to MeOH.

Description

Formaldehyde Production Method

The present invention relates to a method for producing formaldehyde by catalytic oxidation-dehydrogenation reaction of methanol.

Techniques related to the present invention include the formation of formaldehyde, including catalytic catalytic oxidation-dehydrogenation of gaseous feedstocks, including a mixture of air and methanol in the presence of a silver catalyst or a mixture of air and methanol with steam and other inert gases, waste gases, and the like. It relates to commercial manufacturing methods.

However, these methods have room to improve the yield of formaldehyde and do not achieve completely satisfactory results in industrial production. Several attempts have been made, including US Pat. Nos. 4, 519, 509, to eliminate this drawback by adding other metals to previously used silver catalysts (usually electrolytic silver). However, since these methods do not completely overcome the above drawbacks, there is a need for development of excellent methods for producing formaldehyde in high yield.

It is an object of the present invention to provide a process for producing high yields of formaldehyde and in particular for the process of premature oxidation-dehydrogenation of methanol by air in the presence of a silver-filadium catalyst.

The silver-palladium catalyst used in the present invention is a silver catalyst containing 10 ppm by weight to 5% by weight and preferably 50 to 10,000 ppm by weight of palladium. Such a catalyst may be prepared by a known alloy production method and is granular with a particle size of 0.1 to 2.0 mm. The catalyst can also be prepared by attaching metal palladium to a surface by immersing electrolytic or granular silver in an aqueous solution of palladium chloride. After activating the catalyst thus prepared, it is used by another method by wet reduction in an alkali formaldehyde solution.

Formaldehyde may be produced by the catalyst of the present invention in the same manner as the method for producing formaldehyde using a conventional catalyst. Chargestock may be a gas mixture containing methanol and air, or a mixture of steam, an inert gas, and wastes generated during the manufacture of formaldehyde with air and methanol.

According to the invention the de-hydrogenation reaction is carried out at a reaction temperature of 500-750 ° C., preferably 600-700 ° C., given by the catalyst bed temperature, 0.3-2.5 metric tons / hour, preferably 0.5-2.3 per cubic meter of catalyst. It can be carried out at a methanol introduction rate of metric ton / hour. The mixing ratio of air to methanol is 1.1 to 2.7 moles of air, preferably 1.5 to 2.3 moles of air, relative to 1 mole of methanol. When the reaction is carried out in the presence of steam an increase of 1.3 to 1.5 moles of steam, preferably 0.5 to 1.2 moles, is used per mole of methanol. When the reaction is carried out in the presence of waste, 0.8-2.5 moles, preferably 1-1.8 moles of waste are used per mole of methanol.

The present invention provides the excellent advantage of obtaining formaldehyde with high yields calculated on the basis of methanol feedstock, and also provides the advantage that the methanol content in the obtained formaldehyde solution is considerably lower.

In the examples to be described below the conversion ratios and yields are calculated as follows.

[Comparative Example]

Electrolyzed silver was filled in an adiabatic reaction column having an internal diameter of 86 mm to a height of 20 mm, and formaldehyde was prepared at a reaction temperature of 670 ° C. by supplying 181.2 mol of methane of 1 part and 326.2 mol of air and 181.2 mol of steam.

The conversion of methanol feed is 96.0% and the yield of formaldehyde is 88.4%. The amount of unreacted methanol in the product is 2.3 parts per 37 parts by weight of formaldehyde.

Example 1

The reaction is carried out in the same reaction vessel as used in the comparative example under the same reaction conditions, and the catalyst uses a silver-palladium catalyst. The results are compared with the results of the comparative example in Table 1.

TABLE 1

Example 2

Table 2 shows the results obtained using a full-size manufacturing reactor with a diameter of 2m under the same reaction conditions as in the comparative example.

TABLE 2

Claims (6)

A process for producing formaldehyde characterized by the catalytic oxidation-dehydrogenation reaction of methanol with air in the presence of a silver-palladium catalyst. The process of claim 1 wherein the silver-palladium catalyst contains from 10 weight percent to 5 weight percent palladium. The process of claim 1 wherein the silver-palladium catalyst contains 50 to 10,000 ppm by weight of palladium. The mixing ratio of air to methanol at a methanol feed rate of 0.3 metric tonnes / hour to 2.5 metric tonnes per hour of catalyst per meter of catalyst at a reaction temperature of 500 to 750 ° C. given by the catalyst bed temperature. A process characterized by the reaction being carried out at 2.7: 1. The process according to claim 1, wherein the reaction is carried out in the presence of steam having a mixing ratio of steam to methanol of 0.3 to 1.5: 1 per mole. The process according to claim 1, wherein the reaction is carried out in the presence of wastes having a ratio of wastes to methanol of 0.8 to 2.5: 1 per mole.