Synthesis of Pd Composite Tubes by Electroless Plating for Isobutane Dehydrogenation

Isobutene is used as a raw material in the production of ethers for increasing the octane rating and reducing exhaust emissions in gasoline. Dehydrogenation of isobutane is an endothermic equilibrium-limited reaction. Recent studies have focused on overcoming equilibrium limitations by removing the product hydrogen through a membrane. In this study, alumina-modified porous glass supports were plated with Pd using electroless plating (ELP). Plating studies were carried out at 35°C and pH 10-11 in a hydrazine-based plating bath. The thickness of the Pd layer was approximately 100-130 μm. The synthesized composite tube was tested in an isobutane dehydrogenation process over a pure Cr2O3 catalyst in a fluidized bed reactor. The reaction tests were performed at 450oC at slightly greater than atmospheric pressure. The fractional conversion of i-C4H10 to i-C4H8 was approximately 40% at the beginning of the first reaction trial. This value decreased to 5% after 60 minutes. High conversion values were observed in the first trial despite loss of isobutane through the Pd membrane. It was thought that this was due to Pd catalysis of an isobutane hydrogenation reaction using ambient hydrogen, and that this side reaction helped shift the reaction equilibrium to the product side. The conversion decreased as the catalytic activity was reduced by carbon deposits from rapid cracking of methane at the high temperatures resulting from the hydrogenation reaction.