Experimental evidence for hydrogen spillover during hydrocracking in a membrane reactor

Abstract

The significance of hydrogen transport by spillover during diphenylmethane (DPM) hydrocracking in a ceramic membrane reactor has been investigated. In the first part of the study, hydrogen spillover across Al 2O 3 particles of a ceramic membrane was confirmed by the temperature-programmed hydrogenation (TPH) of coke deposited on SiO 2–Al 2O 3, and placed at the bottom of a layered bed of Co-SiO 2 catalyst and Al 2O 3 membrane particles. CH 4 production in the temperature range 430–450 °C was shown to be due to hydrogen activation on the catalyst, spillover across the Al 2O 3 membrane particles and subsequent reaction with the coked SiO 2–Al 2O 3. The second part of the study focused on the hydrocracking of DPM in a membrane reactor configured so that the catalyst and DPM were separated by a ceramic membrane. Conversion of DPM at temperatures <430 °C was indicative of the reaction between DPM and hydrogen, the latter activated on the catalyst and transferred across the membrane to react with the DPM. Experiments showed that despite the separation of reactant and catalyst, the presence of catalyst enhanced the yield of benzene and toluene compared to thermal cracking at the same reaction conditions. Although contact between liquid and catalyst could not be completely eliminated by the porous ceramic membrane, the yield of benzene and toluene could only be accounted for by the spillover of hydrogen from the catalyst to the membrane, followed by reaction with DPM on the shell-side of the reactor.