Fuel, Vol.134, 180-188, 2014
Layer by layer fabrication of b-oriented HZSM-5 coatings for supercritical catalytic cracking of n-dodecane
A layer by layer fabrication of multilayer b-oriented HZSM-5 coating was performed with assistance of surface modification using titanium alkoxide solution. By adjusting the modification conditions, the high coverage of Ti-OH groups of 71.85% was achieved on b-oriented HZSM-5 layer, which is crucial for the inhibition of a-oriented twin crystals and thus the growth of another highly b-oriented HZSM-5 layer on it. Catalytic performance of the HZSM-5 coating was evaluated using catalytic cracking of n-dodecane at 4 MPa and 550 degrees C (supercritical conditions). It was found that the catalytic activity of bilayer coatings improves more than 60% and the deactivation rate sharply decreases from 17.3% to 2.3% when the F-b (a fraction index of b-oriented crystals) changes from 38.5% to 89.7% due to the enhanced diffusion rate in the b-axial channels. The n-dodecane conversion improves by more than 50% but catalytic reaction rate slightly dropped with increasing the number of b-oriented layers from one to three ascribed to the increased zeolite loadings and diffusion limitations in the zeolite channels. (C) 2014 Elsevier Ltd. All rights reserved.