Non-oxidative coupling of methane catalysed by supported tungsten hydride onto alumina and silica-alumina in classical and H2 permeable membrane fixed-bed reactors.

Non-oxidative coupling of methane with high selectivity into ethane (>99% among hydrocarbon) in a classical fixed-bed reactor catalysed by SiO(2)-Al(2)O(3) or gamma-Al(2)O(3) supported tungsten hydride is presented. Continuous hydrogen separation, using a Pd-Ag membrane in a fixed-bed reactor, led to methane coupling far beyond the thermodynamic equilibrium conversion.

Metathesis of Alkanes Catalyzed by Silica-Supported Transition Metal Hydrides

The silica-supported transition metal hydrides (=Si-O-Si=)(=Si-O-)2Ta-H and (=Si-O-)xM-H (M, chromium or tungsten) catalyze the metathesis reaction of linear or branched alkanes into the next higher and lower alkanes at moderate temperature (25degrees to 200degreesC). With (=Si-O-Si=)(=Si-O-)2Ta-H, ethane was transformed at room temperature into an equimolar mixture of propane and methane. Higher and lower homologs were obtained from propane, butane, and pentane as well as from branched alkanes such as isobutane and isopentane. The mechanism of the step leading to carbon-carbon bond cleavage and formation likely involves a four-centered transition state between a tantalum-alkyl intermediate and a carbon-carbon final sigma-bond of a second molecule of alkane.