# Targeted Substituted-Phenol Production by Strategic Hydrogenolysis of Sugar-Cane Lignin
## 5 Conclusions  
In this work, a waste-derived lignin with abundant uncondensed linkages, using accessible solvents (acetone/water mixture) and low-cost catalysts showed successful depolymerization with the generation of the target molecules 4-ethylphenol, 4-propyl-2,6-dimethoxyophenol and 4-propyl-2-methoxyphenol. Lignin was extracted from sugar cane bagasse and depolymerized in the presence of a series of catalysts at 573 K, 20 bang H\({}_{2}\), with solvent, acetone/water 50:50 _v/v_. The molecular weight of the lignin was reduced by half by the catalytic reaction and the polydispersity also decreased showing the presence of less complex and branched molecules compared to the initial lignin. Specific metals directed product distribution and yield, with Rh/Al\({}_{2}\)O\({}_{3}\) having the greatest overall yield, but with Ni/Al\({}_{2}\)O\({}_{3}\) showing the highest selectivity to a given product (\(\sim\)32% to 4-ethylphenol). Mechanistic routes were proposed either from lignin fragments or from the main polymer. Catalysts showed evidence of carbon laydown that was specific to the lignin rather than the catalyst.  
**Supplementary Materials:** The following are available online at [[https://www.mdpi.com/article/10.3390/biomass1010002/s1](https://www.mdpi.com/article/10.3390/biomass1010002/s1)]([https://www.mdpi.com/article/10.3390/biomass1010002/s1](https://www.mdpi.com/article/10.3390/biomass1010002/s1)), Figure S1 TPO plot (left) and derivative weight loss (right) with CO\({}_{2}\) m/z 44 evolution of spent Al\({}_{2}\)O\({}_{3}\) catalyst after acetone/H\({}_{2}\)O reaction with the sugar-cane lignin, Figure S2 TPO plot (left) and derivative weight loss (right) with CO\({}_{2}\) m/z 44 evolution of spent Ni/Al\({}_{2}\)O catalyst after acetone/H\({}_{2}\)O reaction with the sugar-cane lignin, Table S1 Elemental analysis of spent alumina catalysts in SCL depolymerisation, Raman spectrum of spent Al\({}_{2}\)O\({}_{3}\) support, Pt/Al\({}_{2}\)O\({}_{3}\) and Ni/Al\({}_{2}\)O\({}_{3}\), Table S2 BET analysis of spent Al\({}_{2}\)O\({}_{3}\), Pt/Al\({}_{2}\)O\({}_{3}\) and Ni/Al\({}_{2}\)O\({}_{3}\).  
**Author Contributions:** D.M.d.A.F.: Funding acquisition, Validation, Formal analysis, Investigation, Writing--original draft, Writing--review & editing. H.F.G. Investigation, Formal analysis. A.E.G.S.: Investigation, Formal analysis. S.D.J.: Supervision, Project administration, Writing--review & editing. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico--Cnpq, Program Ciencia sem Fronteiras--Doutorado Pleno no Exterior (GDE).  
Data Availability Statement: The data presented in this study are openly available in University of Glasgow library at [[http://theses.gla.ac.uk/](http://theses.gla.ac.uk/)]([http://theses.gla.ac.uk/](http://theses.gla.ac.uk/)) (accessed on 14 June 2021). For further information please contact D.M.d.A.F., A.E.G.S., or S.D.J.  
Conflicts of Interest: The authors declare no conflict of interest.