Pyrolysis and oxidation reactions involving four types of tobacco (a flue-cured Virginia, an air-cured Burley, a fire-cured Kentucky, and Oriental) and a tobacco reference (3R4F), which is a US blended tobacco of burley, virginia and oriental, are studied in a thermogravimetric analyser coupled to a Fourier-transform infrared (TG-FTIR) spectrometer, under inert and oxidising atmospheres. We also assess the effect of the addition of SBA-15 on the thermal degradation of tobacco in both atmospheres. All tobacco samples exhibit similar decomposition patterns resulting from the pyrolysis of their components, mainly hemicellulose, cellulose and lignin. Virginia type tobacco undergoes a marked volatilisation/decomposition process at low temperatures (125-250 degrees C). Oriental and Burley type tobaccos, on the other hand, undergo this same process at high temperatures. 3R4F reference tobacco exhibits the largest peak intensity for the decomposition of hemicellulose, pectin and cellulose. IR data allow a better interpretation of the reactions as they occur. The presence of catalyst produces a decrease in the evolution of CO at high temperatures. More residue is obtained in the presence of catalyst, and it is also less reactive. Under oxidising conditions, the catalyst produces marked differences in the oxidation reactions of the residue resulting from the decomposition of hemicellulose, pectin and cellulose, by limiting the evolution of methane and inhibiting CO formation reactions at high temperature.