GB655557A - Improvements in or relating to the production of aldehydes and to catalysts for use in oxidative processes - Google Patents

Abstract

Aldehydes are prepared from aliphatic alcohols having up to four carbon atoms by reacting the alcohols and oxygen in vapour phase in the presence of a catalytic body comprising molybdenum trioxide and a lesser amount by weight of cerium oxide or samarium oxide prepared by mixing an aqueous solution of a molybdenum salt and a cerium or samarium salt with a carbonaceous binder or support and calcining the resultant mixture. The preferred catalyst contains 90 to 99 parts molybdenum trioxide and 1 to 10 parts of cerium oxide. Three preparations of a molybdenum trioxide/cerium oxide catalyst are described in detail (see Group III), an aqueous solution of ammonium molybdate or other molybdenum salt is mixed with an aqueous solution of cerium chloride or other cerium salt to form a complex colloidal dispersion to which is added a carbonaceous material supporting agent, e.g. soluble starch, activated charcoal, ammonium alginate, methyl cellulose or polyvinyl alcohol; water is evaporated off to leave a paste which is pelleted or extruded into cylindrical pieces or the paste is dried and then pelleted; finally the particles are calcined. The product normally contains some carbon. A summary is given of a number of conversions of methanol to form aldehyde employing molybdenum trioxide-cerium oxide catalysts in which the oxide ratios are 90 : 10 or 99 : 1 and the supporting agent is carbonized starch or activated charcoal. The general procedure consists of passing metered air through methanol and then directing the air-methanol mixture through a heated chamber, e.g. an aluminium tube, containing the catalyst; the effluent gases are passed through a bubble cap absorption tower countercurrently to water which dissolves out the formaldehyde. The methanol and air or oxygen are preferably anhydrous, and oxidation temperatures within the range of 300 DEG to 500 DEG C. are employed, with a contact time of about 0.3 to 2.0 seconds. Other alcohols mentioned are ethanol, propanol and butanols. The Specification as open to inspection under Sect. 91 relates to the production of aldehydes in general by reacting an alcohol with oxygen at elevated temperature in the presence of a catalytic body comprising molybdenum oxide and a lesser amount of a rare earth metal oxide. Reference is made to inert supporting agents generally for use with the catalysts, e.g. pumice and activated alumina. This subject-matter does not appear in the Specification as accepted.ALSO:Catalytic agents for use in the oxidation to aldehydes of aliphatic alcohols containing up to 4 carbon atoms comprise molybdenum trioxide and a lesser amount by weight of cerium oxide or samarium oxide prepared by mixing an aqueous solution of a molybdenum salt and a cerium or samarium salt with a carbonaceous binder or support and calcining the resultant mixture. In a typical preparation, a solution of ammonium molybdate is mixed with a solution of cerium chloride (obtained by reacting cerium hydrate with concentrated hydrochloric acid), the pH is adjusted to about 5 by addition of ammonium hydroxide and a solution of soluble starch is added to the resulting complex colloidal dispersion. The mixture is concentrated to a thick paste, pelleted, dried and then calcined, yielding a catalyst comprising 99 parts molybdenum trioxide, 1 part cerium oxide and a small proportion of carbonized starch. In place of the starch there may be used activated cocoanut charcoal, ammonium alginate, methyl cellulose or polyvinyl ether. Another catalytic composition described contains 90 parts molybdenum trioxide, 10 parts cerium oxide and about 6 parts of carbon. A summary is given of conversions of methanol to formaldehyde by vapour phase oxidation with air at about 300-500 DEG C. (see Group IV (b). Other alcohols mentioned are ethanol, propanol and butanols. The Specification as open to inspection under Sect. 91 relates to catalytic agents comprising molybdenum oxide and a lesser amount of a rare earth metal oxide for use in the oxidation to aldehydes of alcohols in general. Pumice, activated alumina and other inert supports for the catalysts may be used. This subject-matter does not appear in the Specification as accepted.