Process for producing alkadienes

Abstract

This invention provides an improved process for producing alkadienes which comprises (1) contacting butadiene or isoprene with a catalyst such as platinum or palladium or a compound of one of said metals in a sulfolane solution, in the presence of a tertiary lower alkylamine formate and at least one phosphine compound of the formula: ##STR1## wherein R.sup.1 is a substituted or unsubstituted C.sub.1-10 hydrocarbon group; R.sup.2 is H, a saturated aliphatic C.sub.1-5 hydrocarbon group, nitro or halogen; m is 1, 2 or 3; n is 0 or 1; x is 0, 1 or 2; y and z each is 0, 1, 2 or 3 (provided that y and z are not zero concurrently and x+y+z=3); A is --SO.sub.3 M wherein M is a cation selected from among H, alkali metals, alkaline earth metals and NH.sub.4 or the formate or an inorganic acid salt of ##STR2## wherein R.sup.3 and R.sup.4 each means a saturated aliphatic C.sub.1-4 hydrocarbon group in an amount of 4 to 200 moles per gram atom of the metal constituting the catalyst to form dimeric alkadienes; (2) separating the reaction mixture into an alkadiene-containing layer and a catalyst-containing layer; and (3) recycling the catalyst-containing layer to the alkadiene production process. The improved process makes it possible to maintain the catalytic activity over a prolonged period of time and to facilitate separation and reuse of the catalyst.