Thermogravimetry coupled to Fourier Transform Infrared Spectroscopy (TGA-FTIR) was used to study the effect of nickel ions on heavy oil combustion. Mainly, the low temperature oxidation (LTO) process was studied by conducting isothermal alpha(0) experiments at three different temperatures: 200, 250 and 300 degrees C. The kinetics of the reactions was analyzed using the TG results. Nickel ions decreased the activation energy of the process from 16.9 kJ/mol to 10.9 kJ/mol. The FTIR spectra of the evolved gases were helpful in understanding the effect of nickel ions on the quality of LTO products. TGA-FTIR analysis revealed a production of different oxygenated compounds, such as phenols, carboxylic acids, sulfones and side products such as sulfur dioxide, during LTO. According to this analysis, using nickel ions decreased the concentration of oxygenated compounds in the evolved gases, and increased the concentration of carbon dioxide and water. It also decreased the concentration of sulfur dioxide. This effect was more promising at higher temperatures. This effect of nickel ions on LTO reactions can be of great interest in improving the efficiency of the in situ combustion technique used for heavy-oil recovery. (C) 2012 Elsevier Ltd. All rights reserved.