GB348604A - Improvements in the catalytic vapour-phase oxidation of aromatic organic compounds - Google Patents

Abstract

The catalytic vapour-phase oxidation of aromatic compounds is effected in the presence of hydrogen or the vapour of an organic compound that is more readily oxidized than, and is not homologous or isomeric with, the compound which it is desired to oxidize. Aliphatic alcohols, gasoline, petroleum ether, and readily oxidized alicyclic compounds are suitable additions. The preparation of suitable catalysts is described in the examples. In example 1, the catalyst may be vanadium pentoxide, or other metal oxide of the fifth or sixth periodic group, deposited on aluminium, or a salt of aluminium, titanium, iron, cobalt, zirconium or copper with a metal acid of the fifth or sixth periodic group. In example 2, the catalyst used is a silver vanadyl vanadate, prepared by melting vanadium pentoxide with silver nitrate, or a similarly prepared alkali vanadyl vanadate in which part of the alkali is replaced by base-exchange by aluminium, copper or iron. The catalyst may be used alone or diluted or supported on carriers, a number of which are specified; in the last event cementing agents, e.g. potassium sulphate or nitrate may be included. Stabilizer promoters (cf. Specification 291,419, [Class 1 (i), Chemical processes &c.]), e.g. oxides of aluminium, titanium, and thorium, may also be present. In example 3, the catalyst is prepared by spraying a suspension of ferric vanadate in a solution of potassium sulphate, nitrate, or nitrite on to heated pumice; ferric salts of other metal acids of the fifth or sixth periodic group may be used instead of ferric vanadate, and salts of manganese, aluminium, or cobalt may be used instead of ferric salts; precipitated metal oxides, e.g. ferric oxide, may be included in the mixture. The Specification as open to inspection under Sect. 91 (3) (a) states that the process may be effected in the presence of carbon monoxide and may be applied to the purification of coal-tar ammonia. This subject-matter does not appear in the Specification as accepted.ALSO:In the catalytic vapour-phase oxidation of aromatic compounds, excessive oxidation is hindered or avoided by adding to the reaction mixture hydrogen or the vapour of an organic compound that is more readily oxidized than, and is not homologous or isomeric with, the compound which it is desired to oxidize. The catalysts may be those described in Specifications 281,307, 291,419, 295,270, 296,071, and 315,854, [all in Class 2 (iii), Dyes &c.], and the processes may be circulatory. In example 1, maleic and mesotartaric acids are prepared by vapour-phase oxidation of benzene, phenol, tar phenols, or phthalic anhydride with air in the presence of hydrogen or gasoline, methyl alcohol, or gases containing methane; formaldehyde is obtained also when methyl alcohol or methane is used. The catalyst may be vanadium pentoxide, or other metal oxide of the fifth or sixth periodic group, deposited on aluminium, or a salt of aluminium, titanium, iron, cobalt, zirconium or copper with a metal acid of the fifth or sixth periodic group. In example 2, benzoic acid and benzaldehyde are prepared by vapour-phase oxidation of toluene with air in the presence of methyl alcohol or gasoline; formaldehyde or a small amount of aliphatic acid may also be obtained. The catalyst used is a silver vanadyl vanadate, prepared by melting vanadium pentoxide with silver nitrate, or a similarly prepared alkali vanadyl vanadate in which part of the alkali is replaced by base-exchange by aluminium, copper or iron. The catalyst may be used alone or diluted or supported on carriers, a number of which are specified; in the last event cementing agents, e.g. potassium sulphate or nitrate, may be included. Stabilizer promoters (cf. Specification 291,419), e.g. oxides of aluminium, titanium, and thorium, may also be present. These catalysts may also be used in preparing, as described above, salicyl aldehyde and salicylic acid from cresol; halogen- or nitrobenzoic acids and -benzaldehydes from the correspondingly substituted toluenes; acids and aldehydes from xylene, pseudocumene, mesitylene, p-cymene and other homologues of benzene; a -naphthoquinone from naphthalene; naphthalic anhydride from acenaphthene; and fluorenone from fluorene. In example 3, naphthalic anhydride is obtained by vapour-phase oxidation of acenaphthene with air in the presence of gasoline. The catalyst is prepared by spraying a suspension of ferric vanadate in a solution of potassium sulphate, nitrate, or nitrite on to heated pumice; ferric salts of other metal acids of the fifth or sixth periodic group may be used instead of ferric vanadate, and salts of manganese, aluminium, or cobalt may be used instead of ferric salts; precipitated metal oxides, e.g. ferric oxide, may be included in the mixture. If the reaction is effected with an oxidizing gas containing less oxygen than air, naphthaldehydic acid, acenaphtha quinone, and acenaphthylene are obtained. Reference is made also to the production of phthalic anhydride and maleic acid from naphthalene; anthraquinone from anthracene; acenaphthaquinone, bisacenaphthylidenedione, naphthaldehydic acid, naphthalic anhydride, and hemimellitic acid from acenaphthylene; vanillin and vanillic acid from eugenol and isoeugenol; fumaric acid from benzene, toluene, phenol, or phthalic anhydride; and phenanthraquinone, diphenic acid, phthalic anhydride and maleic acid from phenanthrene. Aliphatic alcohols in general, petroleum ether, unsaturated aliphatic compounds, and readily oxidized alicyclic compounds are also mentioned as substances suitable for preventing excessive oxidation. The Specification as open to inspection under Sect. 91 (3) (a) refers to the use of carbon monoxide as an agent for preventing excessive oxidation, and states that the process may be applied to (1) the production of formaldehyde from methyl alcohol or methane, acetic acid from ethyl alcohol, and chloracetic acid from ethylene chlorhydrin; (2) to the production of fumaric, maleic, or mesotartaric acid from furfural; (3) to the purification of coaltar ammonia and of organic compounds such as anthracene and naphthalene, by total combustion of the impurities; and (4) to the partial oxidation of an impure organic compound with simultaneous total combustion of the impurities; in this last connection reference is made to the oxidation of crude anthracene and phenanthrene to anthraquinone, phenanthraquinone, diphenic acid, and phthalic anhydride, and to the oxidation of crude tar acids to maleic and fumaric acids. This subject-matter does not appear in the Specification as accepted.