(An) experimental study of multiple steady states in a porous catalyst due to phase transition

Abstract

Up to four multiple steady states were experimentally observed by hydrogenating cyclohexene on Pt/$Al_2O_3$ catalyst having bimodal pore size distribution. The catalyst, in the form of 3/16 inch by 3/16 inch cylindrical pellet containing 5.6 wt \% platinum of -alumina support, was imbedded in a bed of inert -alumina pellets of similar size to isolate the effect of individual catalyst pellet. The reaction condition was varied by means of hydrogen partial pressure in the reactant mixture. The reaction was run at four different temperature, i.e. 15, 22, 30, and 40$^\circ$C. From experimental evidences and numerical calculations, these multiple steady states were interpreted as the rates of vapor-filled catalyst, liquid-filled catalyst, and catalysts wherein liquid is filled in all of its micropores and in part of its micropores. The transition of phase was apparent from a sharp increase in observed reaction rate as a results of differences in intrinsic kinetics and mass transfer rate in the catalyst pellet. An explanatory scheme on the intriguing behavioral chatacteristics of the reaction rates was proposed.