Abstract
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 4MPa and 550°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 Fb (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.
Published Version
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