Pyrolysis of biomass is thermal depolymerization and decomposition of biomass (TDP) in the absence of air/ oxygen. The temperature generally used is in the range of 623—973K (Goyal et al., 2008). The products, charcoal or biochar, gaseous and liquid chemicals, depend on the biomass composition, the heating rate and the tempera­ture. According to the heating rate, pyrolysis is classified as slow pyrolysis, fast pyrolysis and flash pyrolysis.

Slow pyrolysis of biomass is conducted at slow heating rates (0.1—1 °C/s). In the relatively low temperatures of 573—673K, charcoal is the main product; when the tem­perature is are increased to >673K, the oil yield is increased (Putun et al., 2001; Ozbay et al., 2001; Onay and Kockar, 2004). By contrast, fast pyrolysis is conducted at higher heating rates (about 10—200 ° C/s) and intended to produce liquid bio-oil (Bridgwater, 2003). Flash pyroly­sis is conducted at heating rates >1000 °C/s within
reaction time of only several seconds or even less (Demi — rbas and Arin, 2002). Among these, fast pyrolysis is of most commercial interest for production of chemicals and liquid fuels (Zhou et al., 2011).

Fast pyrolysis is mainly intended to maximize the bio­oil yield as well as to increase the contents of the target compounds in it. To this end, there are needs to use a finely ground particle biomass feed of typically less than 3 mm, selective catalysts, a well-controlled pyrolysis temperature of around 773K, short hot vapor residence time of typically less than 2 s and rapid removal and cool­ing of the products (Bridgwater, 2012).