Experimental study on light volatile products from thermal decomposition of lignin monomer model compounds: effect of temperature, residence time and methoxyl group

In order to investigate the effects of temperature, residence time (RT) and methoxyl (OCH(3)) on the product distribution and vapor phase reactions during pyrolysis of complex solid fuels, three model phenolic representatives, phenol, guaiacol and syringol, were pyrolyzed at a residence time of 0.7 s, over a temperature range of 400 °C–950 °C, and at temperatures of 650 °C and 750 °C, in a RT region of 0.1 s–4.2 s. Increasing yields of CO and C(1)–C(5) light hydrocarbons (LHs) with RT at 650 °C and 750 °C indicated that ring-reduction/CO elimination of phenolic compounds happened at 650 °C, and dramatically at 750 °C. The addition of OCH(3) affects the product distribution and ring-reduction pathways: C(5) LHs from phenol, C(2) LHs, C(4) LHs and C(5) LHs from guaiacol, and C(1)–C(2) LHs from syringol. CO(2) yields increase with the addition of OCH(3). CO(2) was formed via benzoyl and a four-membered ring, which would compete with the CO formation. The addition of OCH(3) promotes the formation of coke and tar. The decomposition pathways are discussed, based on the experimental data, focusing on ring-reduction reactions and the formation of CO/CO(2) and C(1)–C(5) LHs.