Catalytic depolymerization of the hydrolyzed lignin over mesoporous catalysts

- Hydrolyzed lignin depolymerization was presented using mesoporous catalysts.
- Mesoporous SBA-15 played a positive role in reducing the char formation.
- The addition of Al and Ni could effectively promote the lignin depolymerization.
- Reaction conditions showed a great effect on lignin depolymerization.
- Ethanol was more effective in suppressing the repolymerization than other solvents.

In this work, the mesoporous SBA-15 and a series of modified catalysts based on it, such as Al-SBA-15 and Ni/Al-SBA-15, were synthesized and used for eliminating the char formation during the depolymerization of hydrolyzed lignin. The temperature, time and solvent effects on the lignin depolymerization were also investigated. Results showed that the repolymerization was effectively suppressed over SBA-15 due to its well-ordered pore structure and large pore size. The addition of Al and Ni elements in SBA-15 could improve the lignin depolymerization performance and saturate the instable intermediates. Ethanol was found to be more effective in suppressing repolymerization than other solvents. 81.4% liquefaction degree and 21.90 wt% monomer yield was achieved, and no obvious char was observed after the depolymerization of hydrolyzed lignin in ethanol solvent at 300 °C for 4 h over Ni/Al-SBA-15(20) catalyst.

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