In-situ hydrogenation of lignin depolymerization model compounds to cyclohexanol

The integrated process of aqueous phase reforming of methanol for hydrogen and hydrogenation of phenol and guaiacol, two lignin model compounds, was conducted with Raney Ni catalyst in this work. The effects of pressure, temperature, reaction time and mixture ratio of reactants on the performance of in-situ hydrogenation of lignin depolymerization model compounds were investigated. The mechanism was also discussed. Results showed that the guaiacol conversion and cyclohexanol selectivity reached 99.00% and 93.74% with time-on-stream of 7 h, while the phenol conversion and cyclohexanol selectivity were 90.50% and 99.29% with time-on-stream of 12 h under the optimal conditions of 220°C, initial pressure of 0 MPa (gauge pressure) and mole ratio of water/methanol/feedstock=20/5/0.8. The in-situ hydrogenation of phenolic compounds was also proved to be superior to the hydrogenation system of phenols with external hydrogen supply. This work provides a new alternative for production of chemicals from the depolymerization products of lignin.