Lignocellulos biomass can be converted to bio-oil containing aliphatic hydrocarbons via catalytic pyrolysis at 500 degrees C in the presence of Cs modified amorphous silica alumina ( Cs/ASA). The reaction routes for the formation of aliphatic hydrocarbons was studied using biomass constituent, viz, cellulose, hemicellulose, lignin, and single model components in a pyrolyzer system in conjunction with GC/MS. The pyrolysis behaviour of each biomass constituent was also studied using TGA. The results showed that in the presence of Cs/ASA catalyst aliphatic hydrocarbons can be formed from all the three constituents but mainly from lignin (35% of total peak area compared to 10% for cellulose) resulting in high quality bio-oil with 40 Mj kg(-1) heating value. On the other hand, the pyrolysis of single model compounds did not result in the aliphatic hydrocarbons. However, pyrolysis of mixture of the model compounds yielded in aliphatic hydrocarbons indicating effect of intermolecular interactions such as hydrogen transfer over Cs+ ions. (C) 2016 Elsevier B.V. All rights reserved.