Preparation and performance of hierarchical HZSM-5 coatings on stainless-steeled microchannels for catalytic cracking of hydrocarbons

A series of hierarchical HZSM-5 coatings (HZCs) were prepared on stainless-steeled tubes (I.D. 2 mm) using mesoporous HZSM-5 zeolites (through controllable desilication with alkali-treatment). Catalytic cracking of n-dodecane was used as a model reaction to examine the catalytic performances of HZCs. It was found that the cracking conversion of n-dodecane in the presence of HZC-0.50 (the number after HZC representing the concentration of alkali solution) increased by 40% compared with the parent HZSM-5 coatings (PZC), while the deactivation rate was only 1/7 of PZC ascribed to the enhanced diffusion rates of reactants in the pores (ca. 2.35 times using n-octane as a probing molecule) due to the introduced mesopores in HZCs. And it is also demonstrated that the high catalytic activities are the mutual results from both acid amount and its accessibility.