Efficient evolution of hydrogen from liquid cycloalkanes over Pt-containing catalysts supported on active carbons under "wet-dry multiphase conditions"

Highly efficient evolution of hydrogen is achieved in the dehydrogenation of cycloalkanes such as cyclohexane, methylcyclohexane, and decalin over Pt catalyst supported on active carbon (AC) under "wet-dry multiphase conditions". Formation rate of hydrogen is largely dependent on reaction conditions such as reactant/catalyst ratio, temperature, and support, The highest initial rate of formation of hydrogen, k = 8.0 x 10(-3) mol min(-1), was obtained in the dehydrogenation of cyclohexane over Pt/AC at 623 K and the reactant/catalyst ratio = 3.3 ml g(-1). The addition of second metals such as Mo, W, Re, Rh, Ir, and Pd on the carbon-supported Pt catalysts enhances the dehydrogenation rate due to the promotion of C-H bond cleavage and/or desorption of aromatic products. A physical mixture of Pt/AC and Pd/AC catalysts exhibits higher activities than the monometallic PUAC catalyst owing to the synergistic effects of spillover, migration, and recombination of hydrogen over Pt and Pd catalysts. (C) 2002 Elsevier Science B.V. All rights reserved.