Prevention of deactivation of HZSM-5 by mixing with NaZSM-5 in catalytic reaction of methylcyclohexane.

• Acidity of HZSM-5 is controlled by mixing HZSM-5 and Na-modified HZSM-5. • Na-modification of HZSM-5 change only acidity without change textural properties. • Mixing HZSM-5 and Na-modified HZSM-5 decreases strong acid sites of catalyst with minimizing reduction of weak acid sites. • Catalyst prepared with 50 wt% HZSM-5 and 50 wt% Na-modified HZSM-5 has higher catalytic activity than conventional HZSM-5. In this study, Zeolite Socony Mobil–5 (ZSM-5) was modified by ion exchange with sodium ion to control the strong acid sites of catalyst, and the specific control of strong acid sites was carried out by mixing HZSM-5 and NaZSM-5. The characteristics of the catalyst were analyzed using X-ray diffraction, NH 3 -temperature programmed desorption, pyridine adsorption Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption analysis. The catalysts were used for the catalytic reaction with methylcyclohexane under supercritical condition (500 °C and 5.0 MPa). After reaction, the liquid product was analyzed using gas chromatography-mass spectrometry, and the spent catalyst was analyzed using thermogravimetric analysis to measure coke formation. In the catalytic reaction, conventional HZSM-5 was deactivated quickly with time (59.6 % of deactivation rate), but the mixed catalyst with NaZSM-5 was deactivated more slowly than HZSM-5. In addition, the mixed catalyst having the same mass ratio for HZSM-5 and NaZSM-5 showed the lowest deactivation rate of 37.4 % after 60 min. The mixed catalyst produced 10.1 wt% coke and it was lower than HZSM-5 (12.5 wt%). The catalytic robustness of HZSM-5 could be enhanced by mixing with NaZSM-5. [ABSTRACT FROM AUTHOR]