Abstract
Light cycle oil (LCO) is one of the major products in Fluid catalytic cracking (FCC) processes, and has drawbacks such as high aromatics, sulfur, and nitrogen contents, and low cetane number (CN). Hydro-upgrading is one of the most typical processes for LCO upgrading, and alumina-zeolite (AZ) is an effective hydrotreating catalyst support. This paper examined the effects of different bimetallic catalysts (CoMo/AZ, NiMo/AZ, and NiW/AZ) supported by AZ on hydro-upgrading of both model compounds and real LCO. CoMo/AZ preferred the direct desulfurization (DDS) route while the NiMo/AZ and NiW/AZ catalysts favored the desulfurization route through hydrogenation (HYD). The presence of nitrogen compounds in the feed introduced a competitive adsorption mechanism and reduced the number of available acid sites. Aromatics were partially hydrogenated into methyltetralines at first, and then further hydrogenated, cracked, and isomerized into methyldecalins, monocyclic, and methyltetralines isomers. CoMo/AZ is the best hydrodesulfurization (HDS) catalyst for the model compounds at low H2 pressure (550 psi) and for LCO at lower temperature (573 K), while NiMo/AZ performs the best for LCO at higher temperature (648 K). NiMo/AZ is the best hydrodenitrogenation (HDN) catalyst for LCO. The hydrodearomatization (HDA) performances of NiMo/AZ and NiW/AZ improved significantly and overwhelmingly higher than that of the CoMo/AZ when the H2 pressure was increased to 1100 psi.
Highlights
Heavy oil has to be upgraded before utilization because of high density and high boiling point
(especially polycyclic aromatic hydrocarbons (PAH), which account for 40% to 50%), sulfur and nitrogen contents up to 1.5 wt% and 0.3 wt%, and cetane number (CN) less than 35; Light cycle oil (LCO) cannot be directly used as diesel fractions [3,4]
The study aims to examine the effects of NiMo, NiW, and CoMo supported by AZ on the catalytic performance in the hydro-upgrading process
Summary
Heavy oil has to be upgraded before utilization because of high density and high boiling point. (especially polycyclic aromatic hydrocarbons (PAH), which account for 40% to 50%), sulfur and nitrogen contents up to 1.5 wt% and 0.3 wt%, and cetane number (CN) less than 35; LCO cannot be directly used as diesel fractions [3,4]. It is hard to remove the refractory aromatics and sulfur/nitrogen-containing compounds from LCO using the conventional hydrotreating catalysts and processes. The active amount of the traditional HDS catalyst has to increase fourfold to remove 90% of the sulfur in diesel fractions at 500 ppm [5]. Morphology, and textural properties were analyzed using X-ray diffraction (XRD), pyridine-Fourier transform infrared spectroscopy (FTIR), X-Ray Photoelectron Spectroscopy (XPS), and Transmission electron microscopy (TEM), whose purpose is to upgrade LCO by means of HDS, HDN, and HDA into a premium diesel blending component over a AZ supported bimetallic catalysts. The study aims to examine the effects of NiMo, NiW, and CoMo supported by AZ on the catalytic performance in the hydro-upgrading process
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