Upgrading light hydrocarbons: A tandem catalytic system for alkane/alkene coupling

Abstract

Light hydrocarbons, with relatively low fuel value, are abundant from several sources, including mixed alkane/alkene refinery byproduct streams. A tandem system consisting of a compatible combination of a homogeneous alkane dehydrogenation catalyst (known to be kinetically efficient but thermodynamically disfavored at low temps.) with an olefin dimerization catalyst could effect the coupling of an alkane and alkene to produce a heavier, more valuable fuel mol. (CnH2n+2 + CnH2n = C2nH4n+2), a reaction that is thermodynamically favorable below 250 °C. We have demonstrated that a homogeneous soln. of the pincerligated iridium complex t-Bu4[PCP]IrH4 along with Cp*TaCl2(C2H4) couples 1-hexene/n-heptane to C13/C14 products, operating with up to 90% cooperativity. Combining the dehydrogenation catalyst with a heterogeneous dimerization catalyst offers a promising approach to a practical process; our progress towards that target will be reported.