Catalytic cracking of supercritical n-dodecane over meso-HZSM-5@Al-MCM-41 zeolites

Abstract Meso-HZSM-5@Al-MCM-41 zeolite composites were prepared by sequential desilication and recrystallization of parent HZSM-5 treated with tetramethyl- and tetraethyl-ammonium hydroxide. The as-prepared composites were characterized with XRD, TEM and N2-adsorption-desorption, and found that Al-MCM-41 shell orientedly grows on the meso-HZSM-5 core with thicknesses of 58 nm and 27 nm. Catalytic cracking of supercritical n-dodecane (500 °C, 4 MPa) over the zeolite composites shows that meso-HZSM-5@Al-MCM-41 with core-shell structures exhibits the excellent catalytic performance with the highest catalytic activities up to 31% improvement and the lowest deactivation rate (only one fourth) compared with the parent HZSM-5 zeolite, and that the performance enhancement of meso-HZSM-5@Al-MCM-41 is ascribed to the precracking of n-dodecane over the Al-MCM-41 shell and the enhanced diffusion in the meso-HZSM-5 core as evidenced by the product distribution.