The reaction pathway of coconut shell fast pyrolysis was studied by analysis of the transient evolution product profiles as a function of temperature, measured directly in the sample bed. Fast pyrolysis of coconut shell produced (i) pyrolysis liquid containing C-H, C=O, and C-O-C bands, (ii) char with the absence of C-OH and C=O suggesting that ether and carbonyl compounds were decomposed below 600 degrees C, and (iii) gaseous product majorly consisting of CO2. Increase the heating rate has a greater effect on increasing the yield of aliphatic and carbonyl compounds compared to that of aromatic compounds. The selectivity of the fast pyrolysis liquid was shifted from vinyl species to carbonyl species at temperatures between 500 and 615 degrees C. In situ IR study suggests that CO and CO2 were mainly produced from cracking of C-H and C=O bonds. Fast pyrolysis of D2O-saturated coconut shell showed that moisture in the biomass does not increase the H-2 yield at high temperature and H-2 is mainly produced from breaking of C-H bonds. (C) 2012 Elsevier Ltd. All rights reserved.