Real-time evolved gas analysis by FTIR method: an experimental study of cellulose pyrolysis

A two heating zone pyrolysis system capable of a heating rate of 40°C/s and a flow rate of 70 ml/s was coupled to a rapid scanning Fourier transform infrared (FTIR) spectrometer. This fast evolved gas analysis system was applied to the study of the simultaneous evolution of low molecular weight gas phase products, such as CO, CO2, H2O, CH4, C2H4, and CH2O during the pyrolysis of cellulose. Different pyrolytic conditions, including heating rate, gas flow rate, and residence time, were tested to study their effects on the formation of gaseous compounds during cellulose pyrolysis. Formaldehyde and carbon monoxide formations were observed to have a strong heating rate dependence, whereas carbon dioxide formation showed little dependence with the heating rate. Efforts were made to achieve a well-controlled heating environment and sample temperature measurement. The pyrolysis of levoglucosan, a major component of tar and a primary pyrolysis product of cellulose, was also studied. Comparison of the pyrolysis products from cellulose and levoglucosan showed great similarities and provided insight into the precursors and formation mechanisms of gas phase products. This experimental method provides a technique to analyze evolved gases in real time, information on reaction mechanisms, and a method to distinguish and control primary and secondary reactions.