Potassium catalyzed CO2 gasification of petroleum coke at elevated pressures

• Higher pressures and higher potassium loadings increased the gasification rates.
• At higher pressures, less K vaporization during reaction resulted in higher rates.
• Catalyst was less effective when loaded onto the char than onto raw petcoke.
• Gasification activation energies of K added char & petcoke were 254 & 133 kJ/mol.

The rate of gasification can be increased by the addition of an alkali metal catalyst such as potassium. The effectiveness of potassium, however, depends on the characteristics of the feed material and the operating conditions. In this study, the effect of total pressure and partial CO2 pressure on the gasification rate of K-impregnated petroleum coke was studied. Both raw petroleum coke and the produced char were impregnated with potassium carbonate at different loadings (0.03, 0.06, 0.10, 0.16 K/C molar ratio). The CO2 gasification experiments were performed in a high-pressure thermogravimetric analyzer at different temperatures (998 to 1098 K) and pressures (0.1 to 2.1 MPa), while the samples were characterized with Fourier transform infrared spectroscopy and inductively coupled plasma analysis. The rate increased with increasing pressure because of decreased catalyst volatilization and increased catalyst distribution. The determined activation energies at 0.1 MPa were 254 ± 21 kJ/mol and 133 ± 17 kJ/mol, for K-impregnated char and petroleum coke, respectively. The impregnation of potassium was more effective on raw petroleum coke because petroleum coke had more surface functional groups and a less ordered crystal structure than char.