Heat-Sink Enhancement of Supercritical Methylcyclohexane Cracking over Lanthanum-Modified Beta Zeolite

摘要

A series of lanthanum/beta-zeolite catalysts was prepared via hydrothermal ion exchange, and characterized by inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and ammonia temperature-programmed desorption. The lanthanum-doping effect on beta-zeolite catalysts was investigated through catalytic cracking of supercritical methylcyclohexane under the system pressure of 4.0 MPa and the mass flow rate of 1.0 g/s. For lanthanum/beta catalyst of the Cat-2 type, the gas yield of 28.3% and heat sink of 3.35 MJ · kg~(-1) could be achieved at the temperature of 700℃, much higher than those for the pure beta zeolite without lanthanum modification and for the thermal pyrolysis. Correspondingly, Cat-2 has a better performance on coking inhibition with the reduction of 56.2 and 29.5 % at 700℃ compared to beta zeolite and thermal cracking. Therefore, it was indicated that beta zeolite with the suitable lanthanum content, still maintaining its high activity and stability of the zeolite framework at high temperature due to lanthanum doping, had a great contribution to high heat sink and coking inhibition at high temperature.