Polyaromatic hydrocarbon compounds (PAH) such as naphthalene, anthracene, phenanthrene, and their derivatives, commonly found in the light cycle oil or pyrolysis fuel oil, are highly required to upgrade into lighter oil fractions such as benzene, toluene and xylene (BTX). Catalytic hydrocracking is the most effective option to break up the PAHs into BTX over bifunctional catalysts via hydrogenation and cracking. A new hydroprocessing catalyst group of transition metal phosphides has recently been introduced. Among the transition metal phosphide catalysts, Ni2P catalyst is known to show the best activity in hydrotreating. Moreover, the Ni2P catalysts have shown superior hydrogenation activity, even under the presence of nitrogen compounds.
We prepared Ni2P catalysts supported on two types of zeolite Beta, having different crystal sizes, i.e. nano-sized and micron-sized zeolite Beta (Beta-N vs. Beta-M). Supported Ni2P catalysts were prepared by temperature-programmed reduction (TPR)method and were applied for the hydrocracking of 1-methylnaphthalene (1-MN) at 6.0 MPa and 653 K in a three-phase fixed bed reactor. The catalysts were characterized by BET, CO uptake, isopropylamine(IPA)-TPD, TEM, X-ray diffraction (XRD), and extended X-ray absorption fine structure (EXAFS). The Ni2P/Beta-N showed high activity and stability for hydrocracking of 1-MN compared to the Ni2P/Beta-M, with exhibiting high BTX yield (55% vs. 43%). Nano-sized Beta was found to retain inter-crystalline mesopores, leading to better accessibility toward the acid sites and high dispersion of Ni2P, which were ascribed to the better activity of Ni2P/Beta–N in HCK than Ni2P/Beta-M.
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