Theoretical study on gasification of β-1 type lignin dimer with high temperature steam

The density functional theory B3LYP/6-31G(d,p) was used to study the reaction mechanism of β-1 type lignin dimer gasification with high temperature steam based on quantum chemistry. The results show that the enthalpies of R4 and R5 in the beginning of reaction of lignin model compound with high temperature steam, are 243.9 kJ/mol and 323.2 kJ/mol, respectively. These values mean that C_α-C_β bond and C_β-C₁ bond are easy to break. By the calculation, R4-1 and R5-1 reaction barriers are 4.4 kJ/mol and 24.0 kJ/mol, respectively. Thus it is of priority to choose the R4-1 and R5-1 paths in the gasification process. Products via the reaction path calculation include ethanol, methanol, phenol hydroxy toluene and p-hydroxybenzaldehyde, which agree with the experimental results.