Oxidative splitting of unsaturated hydrocarbons

In a process wherein an alkene hydrocarbon of the formula ##EQU4## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 each independently is hydrogen, an aryl group optionally substituted by at least one lower C.sub.1 -C.sub.4 alkyl radical,

• a straight-chain or branched alkyl radical with up to 18 C atoms, optionally phenyl substituted when lower alkyl, or
• the radicals R.sub.1 and R.sub.2 together, or R.sub.3 and R.sub.4 together, contain not more than 20 C atoms and each, independently of each other, form a carbocyclic ring, or
• the radicals R.sub.1 and R.sub.3 together with the C atoms of the C--C double bond are a carbocyclic ring with up to 24 C atoms and R.sub.2 and R.sub.4 each independently is hydrogen or a lower alkyl radical,
• is oxidatively split with both C atoms of the double bond being converted to aldehyde or ketone functions, the improvement which comprises contacting the hydrocarbon for a time sufficient to produce said aldehyde or ketone functions with a gas consisting essentially of oxygen at about 150.degree. to 650.degree.C in the presence of a catalyst consisting essentially of at least one oxide of a metal selected from the group consisting of vanadium, niobium, tantalum, chromium, molybdenum, tungsten, uranium, manganese, technetium and rehenium, oxygen being present in about 0.02 to 50 times the molar amount of the alkene.