Hydrothermal Cracking of Residual Oil.

Abstract

Hydrothermal cracking process of residual oil has been developed by our group for many years to upgrade heavy oil feedstock into valuable middle distillate products. It is a tailor-made combined process of thermal cracking and catalytic hydrogenation. This process can suppress gas and toluene insoluble coke yields and promote middle distillate yield comparing with thermal cracking process at the same conversion level. Hydrothermal cracking process was operated at high reaction temperature (693-733K) and medium hydrogen partial pressure (3.0-8.0MPa). Experiments were conducted in batch autoclave reactors and semi-batch reaction systems respectively. Series of catalysts were prepared from different supports (MgO, active carbon, SiO2 and Al2O3) and active metals (Ni, Mo, Co and W, etc.). Feedstock such as bitumen, AR (atmospheric resid) and VR (vacuum resid) were tested. The structure of feedstock and products were characterized by 1H-NMR. The reuse ability and regeneration of catalysts were studied as well. Alumina-supported catalysts showed better performance and regeneration ability. The reaction mechanism of hydrothermal cracking was also studied by model compound and proposed as one consisting of thermal cracking of hydrocarbon molecules via free radical chain reactions and catalytic quench of free radicals by hydrogen.