Pd based Inorganic Hollow Fibre Membranes for H2 Permeation and Methylcyclohexane Dehydrogenation

The availability of inorganic membranes which can withstand high temperatures and harsh chemical environments has resulted in a wide range of opportunities for the application of membranes in chemical reactions and separations. In particular, the combination of membrane separation and catalytic reaction into a single operating unit is an attractive way to increase conversions, improve yields and more efficient use of natural resources in many reactions. In this study, asymmetric alumina hollow fibres with different macrostructures consisting of finger-like macrovoids and a sponge-like packed pore structure in varying ratios have been prepared by a combined phase inversion/sintering technique. The asymmetric membranes in hollow fibre geometry possess superior surface area to volume ratios with less gas permeation resistance in comparison to commercial symmetric membranes in tubular and disk configurations. Such asymmetric hollow fibres are used as substrates onto which a Pd membrane is directly deposited by an electroless plating (ELP) technique without any pre-treatment of the substrate surface. A systematic study of the electroless plating of Pd and Ag onto an asymmetric alumina hollow fibre substrate has been carried out by direct measurement of one of the gaseous products, i.e. N2, using gas chromatography (GC). In addition, the influences of the substrate macrostructure on hydrogen permeation through the Pd/Al2O3 composite membranes have been investigated both experimentally and theoretically. Furthermore, a multifunctional Pd/alumina hollow fibre membrane reactor (HFMR) has been developed and employed for the catalytic dehydrogenation of methylcyclohexane (MCH) to toluene (TOL). The developed HFMR consists of a thin and defect-free Pd membrane coated directly onto the outer surface of an asymmetric alumina hollow fibre substrate. 50 wt% Ni/Al2O3 nano-sized catalysts were directly impregnated into the substrate. The performance of HFMR has also been compared with several different reactor configurations