GB298142A - Catalytic process for oxidation of organic and inorganic substances - Google Patents

Abstract

298,142. Imray, O. Y., (Monsanto Chemical Works). May 25, 1927. Formaldehyde, acetaldehyde, benzaldehyde, and salicylic aldehyde; benzoic and salicylic acids.- Catalysts suitable for the oxidation in the vapour phase of organic substances other than naphthalene, such as toluene to produce benzaldehyde and benzoic acid, cresol to produce salicylic aldehyde and salicylic acid, and methyl or ethyl alcohol to produce formaldehyde or acetaldehyde, are prepared by forming by a wet process a complex silicate containing vanadium in non-exchangeable form of which at least part is less than pentavalent, with or without other chemical groups such as boric, phosphoric, tungstic, molybdic and other weak acids, stannic and plumbic acids and zinc, aluminium, chromium and other amphoteric hydrates, and subjecting the solid complex silicate to the action of an acid and an oxidizing agent so that the vanadium is converted into vanadium pentoxide, and pyrovanadates embedded in the rigid framework of the silicate. The catalysts may be diluted with various substances, which need not be finely divided, such as silica, silicates, titanates, and stannates, siliceous materials known as " Carrara silica," tripoli and pumice being mentioned. These diluents may be impregnated with chemicals to limit the activity of the catalyst in organic oxidations. Various metals may be introduced into the complex silicates in the form of compounds which will be decomposed by the acid or heat treatment, complex compounds of copper-ammonia, zinc-ammonia and silver cyanide being mentioned. The catalysts are not sensitive to contact poisons, but in organic oxidations iron-containing dust should be removed. In an example for producing a catalyst suitable for making benzaldehyde and benzoic acid, potassium vanadate solution is treated with sulphur dioxide, and caustic potash, potassium silicate and potassium borate are added, after which sulphuric acid is added to produce a gel, the solution remaining weakly alkaline or neutral. The gel is washed, and dried at 100‹ C. and then treated with dilute sulphuric acid and hydrogen peroxide, washed, and dried at 300‹ C.; or the drying may be effected with burner gases, sulphur trioxide and air, or hydrochloric acid and air at 400-500‹ C. The catalyst may be diluted by adding to the original solution or to the gel, kieselguhr or finely divided natural silicates which should be free from iron. The mineral diluents may be used in granules which are mixed with the gel and dried. When the catalysts have baseexchanging properties they may be treated with a solution of, for instance, copper or silver sulphate. In another example for producing a similar catalyst, vanadic acid is suspended in dilute sulphuric acid and treated with. sulphur dioxide, the solution being added to a mixture of waterglass and potassium vanadite until a gel is formed which, if the solution is kept alkaline, is a vanadyl zeolite. After washing and drying it is treated with hydrogen peroxide and dilute sulphuric acid and dried at 300‹ C. Instead of using the acid in liquid form, the granules may be heated in sulphur dioxide and air at 450‹ C. Siliceous diluents, which may contain calcium or aluminium, may be added. In another example, potassium vanadate or a mixture of potassium vanadite and vanadate is dissolved in a thick suspension of a gel produced from waterglass and potassium alum, the gel being washed, dried, and treated with boiling water, washed with cold water and dried at 80‹ C., and then treated with hydrogen peroxide and dilute sulphuric acid and dried again. In a modification, the material after the first drying is treated with a solution of silver nitrate, copper sulphate, or zinc acetate. the subsequent treatment being as described above. Specifications 8462/14 and 266,007, [both in Class 1 (i), Chemical processes &c.], are referred to.