Vacuum residue (VR) upgrading was conducted in the environment of supercritical water (SCW) without oxygen addition in an attempt to yield a maximum of light oil. Simulated distillation of the liquid products from a set of orthogonal experiments shows that temperature should not be too high to restrict coke formation, and the most beneficial condition is found at (1) 420 °C for the temperature, (2) 0.15 g/cm3 for the water density, (3) 2 g/g for the H2O/oil ratio, and (4) 1 h for the reaction time. A simultaneous increase of the water density and H2O/oil would significantly improve the cracking behavior and the yield in light oil. Scattered coke particles between 10 and 100 μm were generated from VR cracking, which suggests the dispersion effect of SCW. The infrared spectrum analysis has indicated an increase in the H/C atomic ratio in the liquid product, which implies that hydrogen is generated from the condensation reactions rather than from water because no oxygen-containing group was detected.
Vacuum residuum (VR) upgrading through pyrolysis in supercritical water was investigated in a bomb
reactor and a batch autoclave. The experiments were carried out in the temperature range of 380−460 °C at
25.0 MPa for 5−120 min with a water/VR ratio of 0.78:1−4:1 by weight. The upgrading leads to a reduction
of 30.9% in resins and asphaltenes, a reduction of 22.8% in aromatics, and an increase of 98.6% in saturates.
The viscosity of the product was reduced from 116 mPa s of the feedback to 6.2 mPa s, which is approximately
179 times. Besides, the average molecular weight was reduced from 1860 to 646 g mol-1, and S, N, Ni, and
V contents were reduced by 32, 15, 83, and 85%, respectively. The upgrading mechanism was proposed as
ionic and radical reactions in parallel.
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