Morphology effect of beta-zeolite supports for Ni2P catalysts on the hydrocracking of polycyclic aromatic hydrocarbons to benzene, toluene, and xylene

摘要

Ni2P catalysts supported on nano-sized beta(beta-N) or micrometer-sized beta (beta-M) zeolites were prepared by temperature-programmed reduction, and their structural and chemical properties were analyzed by N-2 physisorption, transmission electron microscopy, X-ray diffraction, extended X-ray absorption fine structure, NH3 temperature-programmed desorption, and CO uptake. The catalytic activity was tested at 653 K and 6.0 MPa in a fixed bed reactor for the hydrocracking of 1-methylnaphthalene (1-MN) into benzene, toluene, and xylene (BTX). In the hydrocracking, Ni2P/b-N showed better activity and stability for hydrocracking of 1-MN than Ni2P/beta-M, with BTX yields of 42.3% and 30.5% for Ni2P/beta-N and Ni2P/beta-M, respectively. In addition, Ni2P/beta-N maintained the stability in terms of catalytic activity and local structure, while Ni2P/beta-M suffered from coke formation, particularly in the presence of heavy aromatics such as phenanthrene in the feed. The characterization results demonstrated that the beta-N has abundant intercrystalline mesopores to provide better dispersion for Ni2P catalysts and accessibility toward acid sites, offering the proximity of the hydrogenation active center and the cracking sites. Kinetic analysis for the hydrocracking of 1-MN over the catalysts revealed that the Ni2P/beta-N catalyst shows superior activity for both hydrogenation and cracking over the Ni2P/beta-M catalyst. (C) 2017 Elsevier Inc. All rights reserved.