GB2121787A

GB2121787A - Process for producing formaldehyde

Info

Publication number: GB2121787A
Application number: GB08309966A
Authority: GB
Inventors: Shinkichi Imayoshi; Naotaka Kobayashi
Original assignee: Mitsubishi Gas Chemical Co Inc
Current assignee: Mitsubishi Gas Chemical Co Inc
Priority date: 1982-06-11
Filing date: 1983-04-13
Publication date: 1984-01-04
Also published as: JPS6212775B2; KR860000871B1; KR840005064A; GB8309966D0; JPS58216137A; GB2121787B

Abstract

Formaldehyde is produced in high yield at a high conversion ratio by the catalytic oxidation-dehydrogenation of methanol with air in the presence of a silver-palladium catalyst.

Description

SPECIFICATION Process for producing formaldehyde The present invention relates to a process for the production of formaldehyde by the catalytic oxidation-dehydrogenation of methanol.

Those.conversant with the art to which the invention relates are familiar with commercial processes for producing formaldehyde involving the catalytic oxidation-dehydrogenation of a gaseous feedstock, in the presence of silver catalyst, comprising air and methanol, or a mixture of steam and other inert gases, waste gas, and the like with air and methanol. However, these processes leave room for improvement in the yield of formaldehyde, and do not give entirely satisfactory results in industrial production. Several attempts, including U. S. Patent 4,219,509, have been made to eliminate these disadvantages by adding other metals to the silver catalyst (normally electrolytic silver) heretofore used.These processes, however, fail to completely overcome the above drawbacks, and the development of a superior process capable of producing formaldehyde in high yield has continued to be awaited.

The object of the present invention is to provide a process for producing formaldehyde in high yield, and in particular a process that does so by the catalytic oxydation-dehydrogenation of methanol with air in the presence of a silver-palladium catalyst.

The silver-palladium catalyst used in the present invention is a silver catalyst containing from 10 ppm to 5% by weight, and preferably from 50 to 10,000 ppm by weight, of palladium. Such a catalyst can be prepared by a conventional alloy production process, and should be of granules having a particle size of from 0.1 to 2.0 mm. The catalyst may alternatively be prepared by dipping electrolytic or granular silver in an aqueous palladium chloride solution to form a surface deposit of metallic palladium. The catalyst thus prepared is activated prior to use by wet reduction in an alkaline formaldehyde solution or some other method.

Formaldehyde can be produced with the present catalyst in the same manner as formaldehyde production processes that use conventional catalysts. The chargestock may be a gas mixture consisting of methanol and air, or a mixture of steam, inert gases, waste gases generated during formaldehyde production, and the like with air and methanol.

According to the present invention, the dehydrogenation reaction may be carried out at a reaction temperature, given in terms of the catalyst bed temperature, of from 500 to 750"C, and preferably from 600 to 700"C, and at a methanol feed rate per cubic meter of catalyst of from 0.3 to 2.5 metric tons per hour, and preferably from 0.5 to 2.3 metric tons per hour. The mixing ratio of air to methanol is from 1.1 to 2.7 moles of air, and preferably from 1.5 to 2.3 moles of air, to 1 mole of methanol. When the reaction is carried out in the presence of steam, from 0.3 to 1.5 moles of steam, and preferably from 0.5 to 1.2 moles of steam, are used per mole of methanol.When the reaction is carried out in the presence of waste gases, from 0.8 to 2.5 moles, and preferably from 1 to 1.8 moles, of waste gas are used per mole of methanol.

The present invention provides the excellent advantage of a high yield of formaldehyde, as calculated based on the methanol feedstock, and also provides the further advantage that the methanol content in the formaldehyde solution obtained is exceedingly low.

In the examples presented below, the conversion ratios and yields were calculated as follows.

converted methanol (moles) Conversion ratio (%) converted methanol (moles) x 100 feed = methanol (moles) Yield it(%) formaldehyde product (moles) x 100 feed methanol (moles) Comparative example Electrolytic silver was filled to a height of 20 mm in an adiabatic reaction column having an inside diameter of 86 mm, and formaldehyde was prepared at a reaction temperature of 670"C by feeding 181.2 moles of methanol, 326.2 moles of air, and 181.2 moles of steam per hour into the column. The conversion ratio of the methanol feedstock was 96.0%, and the yield of formal-dehyde was 88.4%. The amount of unreacted methanol in the product was 2.3 parts per 37 parts of formaldehyde by weight.

Example 1 A reaction was conducted in the same reaction column as in Comparative Example, and under the same reaction conditions, but using a silver-palladium catalyst. The results are compared in Table 1 with those from Comparative Example.

TABLE 1 Pd content waterlmethanol airlmethanol (ppm by weight) (mole ratio) (mole ratio) 0 1.0 1.8 10 1.0 1.8 25 1.0 1.8 50 1.0 1.8 100 1.0 1.8 5000 1.0 1.8 10000 1.0 1.8 50000 1.0 1.8 TABLE 1 (cont'd) methanol in 37"/o formaldehyde Conversion ratio yield {% by weight) {mole %) (mole%) 2.3 96.0 88.4 1.0 98.3 91.0 1.0 98.9 92.1 0.9 99.2 93.2 1.0 99.1 92.4 1.2 99.1 92.2 1.0 98.7 92.3 1.1 97.9 91.1 Example 2 Table 2 gives the results obtained underthe same reaction conditions as in Comparative Example, but using a full-scale production reactor having a diameter of 2 meters.

TABLE 2 Pd content waterlmethanol airlmethanol (ppm by weight) (mole ratio) (mole ratio) 50 1.0 1.8 100 1.0 1.8 TABLE 2 (Cont'd) methanol in 370/c Conversion ratio yield formaldehyde (mole %) (mole /OJ {% by weight) 0.8 99.0 91.7 0.9 98.9 91.3

Claims

1. A process for producing formaldehyde which comprises catalytic oxidation-dehydrogenation of methanol with air in the presence of a silver-palladium catalyst.

2. The process according to Claim 1 wherein the silver-palladium catalyst contains from ppm to 5% by weight of palladium.

3. The process according to Claim 1 wherein the silver-palladium catalyst contains from 50 to 10,000 ppm by weight of palladium.

4. The process according to any one of claims 1 to 3 wherein the reaction is carried out at a reaction temperature of from 500 to 750"C, given in terms of the catalyst bed temperature, a methanol feed rate of from 0.3 metric tons/hour to 2.5 metric tons/hour per cubic meter of the catalyst, and a mixing ratio of air to methanol of 1.1 - 2.7:1 by mole.

5. The process according to any one of claims 1 to 4 wherein the reaction is carried out in the presence of steam in a mixing ratio of steam to methanol of 0.3 - 1.5:1 by mole.

6. The process according to any one of claims 1 to 5 wherein the reaction is carried out in the presence of a waste gas in a ratio of waste gas to methanol of 0.8 - 2.5:1 by mole.

7. A process according to claim 1 substantially as hereinbefore specifically described with particular reference to the Example.

8. Formaldehyde when produced by a process as claimed in any one of claims 1 to 7.