A solvent deasphalting dearomatization (SD-A2) process for heavy oil upgradation

A two stage solvent deasphalting dearomatization (SD-A(2)) process has been conceptualized for upgrading heavy oils. In the first stage, pentane, heptane and refinery untreated/treated naphtha streams (Light Naphtha (LN), Heavy Naphtha (HN) & Raffinate Naphtha (RN)) were investigated for deasphalting performance. To enhance the deasphalting, spent catalyst from Fluid Catalytic Cracking Unit (FCCU) is used in the first stage which showed increase deasphalted oil (DAO) and also pitch yields up to 2 wt%. In the second stage, six polar solvents viz. sulfolane, N-methylpyrrolidone (NMP), tri-ethylene glycol, tetra-ethylene glycol, furfural and N-formylmorpholine (NFM) have been analyzed for dearomatization. The phase equilibria behaviour of these six potential polar solvents was investigated, including the interaction behaviour of their components with heavy oil components using ternary phase diagrams at ambient conditions, before selecting the most suitable solvent for dearomatization. Based on the phase equilibria data, distribution coefficient, selectivity, and performance index (PI) of the solvents was also estimated. For the oils which have C-6-C-15 carbon range, the universal quasi-chemical UNIQAC model was used to predict the liquid-liquid equilibria (LLE) and solvent NMP gave highest performance index for the high carbon number feedstock. The effects of solvent types and solvent to feed ratio on the deasphalting performance was also investigated. Finally, the DAO obtained at each stage was fed to a fluid catalytic cracking (FCC) bench-scale unit and the results showed significant improvement in gasoline yields up to 5 wt% and the coke was also lowered to 2 wt%.

Automated summary

A two-stage solvent deasphalting dearomatization process was proposed for upgrading heavy oils, utilizing different solvents in each stage to improve deasphalting and dearomatization performance. By analyzing six polar solvents, the most suitable solvent for dearomatization was selected based on phase equilibria behavior, with NMP showing the highest performance index for high carbon number feedstock. The effects of solvent types and ratios on deasphalting performance were also investigated, leading to significant improvements in gasoline yields and coke reduction.