Abstract
In this study, Cs-exchanged phosphotungstic acids (CsxH3-xPW12O40, x = 1-3) were examined as a catalyst for the hydrocracking of extra-heavy oil (vacuum residue, API gravity = 2.3 degrees). CsxH3-xPW12O40 showed a higher activity than the commercially available, NiMo/Al2O3-based catalyst in the hydrocracking of extra-heavy oil; the former catalyst produced a larger quantity of liquid oils than the commercial catalyst. The liquid oils produced by the phosphotungstic acids were slightly heavier than those produced by the commercial catalyst. They also showed comparable activities to the commercial catalyst in terms of the hydrogenative removal of metals (nickel, vanadium) and sulfur from the extra-heavy oil. It was found that the hydrocracking performance was primarily dependent on the surface acid density of heteropolyacids. The best performance of the CsxH3-xPW12O40 catalysts was obtained at a Cs loading of x = 2.2, where the surface acid density was highest. To assess the physical and chemical properties of the catalysts, various characterization techniques were used, including inductively coupled plasma-mass spectrometry, X-ray diffraction, thermogravimetric analysis, Fourier transform-infrared spectroscopy, Brunauer-Emmett-Teller analysis, and ammonia-temperature programmed desorption analysis. (C) 2014 Elsevier Ltd. All rights reserved.