By using the mass spectrometry technique, the catalytic effect of ferric sulfate on the evolved gases of the pyrolysis of residues from the cassava starch industry was studied.There were identified 31 m/e ratios in the evolved gases with enough signal to noise ratio.The presence (or absence) of m/e signals in the pyrolysis evolved gases with (or without) catalyst suggest a change in the product distribution 3600 Alberto R. Albis A. et al. caused by the catalytic activity of the ferric sulfate.These signals were fitted with the DAEM using the kinetic parameters calculated from previous thermogravimetry data.As result, 90% of the m/e ratios presented a good fit.The poor description of the model for the rest of the signals could be attributed to secondary reactions in the gas phase.