Catechol production from lignin by Al-doped mesoporous silica catalytic cracking

- Lignin is transformed to valuable fine chemical by catalytic pyrolysis.
- High catechol selectivity is obtained by using a small amount of Al-MCM-41.
- Al-MCM-41 is a good catalyst for lignin pyrolysis at a low temperature (300 °C).
- Post-synthesis incorporation of Al is a good method for MCM-41 acidification.
- The catechol production pathway from lignin acidic cracking is proposed.

Two synthesized mesoporous aluminosilicate catalysts were tested for their performance in the lignin hydrothermal cracking to benzenediol derivatives, and especially to catechol (1,2-benzenediol), compared to non-catalytic cracking. In this study, Al-doped MCM-41 catalysts were synthesized by direct and post-synthesis methods while Al-doped SBA-15 was prepared by post-synthesis method. The catalytic performance of these synthesized mesoporous aluminosilicate catalysts was compared with microporous HZSM-5 in terms of their selectivity for catechol production. All the tested catalysts gave markedly higher catechol selectivity than the non-catalytic reaction. The acidity and porosity of the catalyst played an important role in the selectivity for catechol. The highest selectivity for catechol (35.5%) was achieved from lignin hydrothermal cracking at a low temperature (300 °C) for 30 min with the Al-MCM-41 catalyst prepared by post-synthesis method, and at a catalyst to lignin weight ratio of 0.75.

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