Vapor-Phase Transport Crystallization of Micro-HZSM-5 Zeolite Coatings

摘要

A novel structured catalyst of binderless micro-HZSM-5 zeolite coating was prepared on stainless-steeled tubes (i.d. 2 mm) through wash coating and vapor-phase transport (VPT) crystallization method. The subsequent crystallization of amorphous SiO_2 binders improved the coatings adhesion tremendously by more than 10 times with the least amount of binders (＜20% by weight), attributed to the remarkably enhanced interlock by the formed Mordenite Framework Inverted structure between zeoh'te particles. Catalytic cracking of supercritical n-dodecane (500℃, 4 MPa) was used to examine the catalytic performance of the coatings as prepared, indicating that MZC-V0.2 exhibited a catalytic activity improvement by 8% and a decreased deactivation rate by 48%. The improved catalytic performance may result from its high acid sites amount by incorporating extra-framework Al into HZSM-5 framework, and the possible depressing of pore-mouth deactivation through partial modification of surface acid sites during VPT treatment. This work provides a potential technique to prepare mechanically stable zeolite coatings with high catalytic activity but less binder usage.