Comparison of the effects of dispersed noble metal (Pd) biomass supported catalysts with typical hydrogenation (Pd/C, Pd/Al2O3) and hydrotreatment catalysts (CoMo/Al2O3) for in-situ heavy oil upgrading with Toe-to-Heel Air Injection (THAI)

Abstract

Catalyst deactivation due to coke and metals deposition as a result of cracking presents a challenge in heavy oil recovery and upgrading. This is particularly pronounced for in situ upgrading techniques, in which pelleted catalyst is packed around the perimeter of the horizontal producer well of the Toe-to-Heel Air Injection (THAI) process. The fixed bed of catalyst is virtually impossible to regenerate in place, promoting investigation of alternative contacting via the dispersion of nanoparticles. The catalysts studied were finely crushed micro-particulates with average size of 2.6μm and also a catalyst prepared upon a bacterial support. The latter has advantages in terms of ease of preparation of catalysts from recycled metal sources. Heavy oil of API gravity 13.8° and viscosity 1091mPas was used as feed and upgrading was performed in a batch reactor at 425°C, with a catalyst-to-oil ratio of 0.02 (g/g), and at an initial pressure of 20bar. The activity of the Pd/biomass catalyst was evaluated against a number of other catalysts: Pd/Al2O3, Pd/C, Al2O3 and Co–Mo/Al2O3. By using the Pd/biomass catalyst, the produced oil gravity increased by 7.8° API, and its viscosity was reduced to 7mPas. This effect corresponded to an increase in the amount of low-boiling distillate (IBP – 200°C) from 34.6vol.% (original feedstock) to 53–62vol.%, potentially reducing the amount of diluent needed for pipeline transport of bitumen. The coke yields were (wt.%): 13.65 (Al2O3), 9.55 (Pd/Al2O3), 6.85 (Pd/C) and 3.87 (Pd/biomass). The Pd/biomass catalyst showed significantly reduced coke yield compared to thermal cracking and upgrading using Pd/C and Pd/Al2O3 catalysts, which could greatly enhance catalyst survivability in the field.