Enhancing p-xylene productivity for disproportionation of toluene in microstructured reactors

Microstructured monolith reactors washcoated with ZSM5 and La2O3-loaded ZSM5 (LaZSM5) were used for disproportionation of toluene for studying the effect of washcoat thickness on reactor productivity and yield of the commercially important p-xylene isomer. The toluene conversion and p-xylene yield in the ZSM5 washcoated monolith reactor was superior to that in a packed bed reactor using ZSM5 pellets. Modification of the surface properties of ZSM5 due to addition of La2O3 reduced the toluene conversion but resulted in a substantial enhancement in p-xylene yield. The decrease in catalytic activity and p-xylene yield with increase in washcoat thickness was attributed to the lengthening of the diffusional path length. The reactor productivity was highest with thin washcoats and low conversion on La2O3-loaded ZSM5 washcoated monoliths. The advantage of higher p-xylene productivity using monoliths is offset by the increase in the cost of recycling unreacted toluene. (C) 2012 Elsevier B.V. All rights reserved.