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

Abstract

A two stage solvent deasphalting dearomatization (SD-A2) 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 C6–C15 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%.