Oil dispersed nickel-based catalyst for catalytic upgrading of heavy oil using supercritical water

Upgrading of heavy oil using supercritical water (SCW) has attracted a lot of attention recently due to the unique properties of SCW to act as hydrogen donor source and good solvent for organic matters. In this study, nickel-based oil-dispersed catalyst was used to intensify heavy oil upgrading in SCW. Its catalytic activity on upgrading performance and its influence on environment (from the point of the contamination of wastewater obtained after SCW treatments) weYre assessed. The result revealed that Ni-based catalysts increased the yield of upgraded oil to 89.73% from 81.99%, while reduced the yield of gases and coke to 8% and 2.27% from 14.92% and 3.09%, respectively. With catalysts, the heavy oil (API gravity 14 degrees and viscosity 2073 mPa.s) was upgraded to light oil (API gravity 26.10 degrees and viscosity 19.8 mPa.s) with a higher H/C ratio and lower content of S, N, and metals. Moreover, an obvious change in the composition and structure of upgraded oil was found, including a significant decrease in resins and asphaltenes content with an increase in saturate content; an increase in C-7-C-20 alkanes content with a decrease in C-21-C-30 alkanes; a significant conversion of poly-aromatics into di-aromatics; a decrease in the mean chain length (MCL), aromaticity factor (F-CA), aromatic (C-ar carbons), and secondary + quaternary group (C-sq) with an increase in primary group (-CH3, C-p) and tertiary group (C-t) in the structure of resins and asphaltenes, etc., proved by SARA analysis, elemental analysis, FTIR spectra, GC, GC-MS, and C-13 NMR spectroscopy. In addition, we found that waste water was less contaminated by oil and paramagnetic ions, confirmed by visual observation, scanning optical microscope, and low-field NMR measurements. All these significant improvements in upgrading performance resulted from the in-situ transformation of oil-dispersed Ni-based catalysts into Ni3S2; Ni9S8; NiS; NiO; and Ni[OH](2) in oil environment. These in-situ formed active phases of Ni acted as electro-catalysts for water splitting reactions to promote the participation of water in upgrading process as hydrogen source, and simultaneously accelerated isomerization, hydrogenation, alkylation, and opening ring reactions, which consequently results in a higher yield of upgraded oil with a better quality as well as less contaminated waste water.

Automated summary

Using a nickel-based oil-dispersed catalyst can enhance the upgrading of heavy oil in supercritical water, increasing the yield of upgraded oil, reducing the yield of gases and coke, and improving the quality of the upgraded oil as well as reducing the pollution in the wastewater.