# Targeted Substituted-Phenol Production by Strategic Hydrogenolysis of Sugar-Cane Lignin
## 3 Results and Discussion
### Sugar-Cane Lignin (SCL) Characterization
#### 3.2.10 Catalytic Products
Moreover, at this temperature and pressure, water can interact with organic molecules and the presence of OH- and H+ favours acid/base catalysed reactions [40]. Various approaches with lignin solvolysis have been proposed [12; 26; 43]. Kraft and organo-solv lignins were shown to depolymerise with supercritical acetone and alumina based catalysts [51] and [PERSON] and co-authors described that when a range of lignins were treated with \({}_{\text{sc}}\)methanol, \({}_{\text{sc}}\)ethanol and \({}_{\text{sc}}\)acetone, this last solvent was shown to be the best, giving higher oil yield; water was also shown to be more effective when mixed with another solvent promoting decomposition of lignin [52]. Although there are these effects from solvolysis, greater conversion of SCL was significantly dependent upon the catalysts used. The combination of solvent mixture along with appropriate catalyst resulted in higher overall yield (for Rh/Al2O3) and efficient target molecule generation, especially non-akylated monophcnols (for Ni/Al2O3). Differences between catalysts should be expected due to the number of different reactions (Scheme 1) often occurring on different active sites. For example, hydrogenolysis is highly structure sensitive, whereas aromatic hydrogenation is much less so and both will use different sites. However this gives the potential for more selective behaviour. Figure 5: Selectivity of compounds 4-ethylphenol (2A), 4-methyl-2,6-dimethoxyphenol (9), and 4-propyl-2,6-dimethoxyphenol (14) between the four alumina catalysts. Figure 6: TPO of spent \(\mathrm{Pt/Al_{2}O_{3}}\) catalysts after acetone/\(\mathrm{H_{2}O}\) reaction with the sugar-cane lignin. (**a**) weight loss and derivative weight loss as a function of temperature, (**b**) evolution of CO\({}_{2}\), as ev-idenced by the increase of m/z 44, as a function of temperature mapping on to the derivative weight loss. An ideal type of lignin and a physical, chemical or biocatalytic processes to generate fine chemicals is yet not established. For effective lignin hydrogenolysis, a combination of factors must be addressed, such as viability of the substrate (usually controlled by feedstock), the type of extraction process, depolymerisation-condensation balance, solvent and catalyst. In this work, it was decided to extend to SCL previous optimisation conditions found for ammonia-derived lignin [18]. Indeed, catalytic products from SCL could be successfully obtained at these conditions and the studied catalysts, giving overall yields up to \(\sim 3\) times higher than thermolysis, however, condensation could not be fully overcome. It was interesting to make this comparison because, in contrast to ammonia lignin [18] and SCL, tests with a Kraft lignin [26] using these same reaction conditions showed no significant effect of catalysts compared to solvolysis, which may be associated to its recalcitrant degree of condensation (C-C type of bonds), thus, reinforcing the applicability of lignin structure in hydrogenolysis strategies. Yet, despite of promising results, each lignin behaved as a unique system and SCL required its own optimisation to give it its full potential. Overall, this extracted raw substrate had appreciable activity for hydrogenolysis, providing specific monophenolics only in catalytic tests and according to the type of metal, giving selectivity up to 32% for 4-ethylphenol using Ni/Al2O3. Most importantly, the results indicated that control upon selectivity is possible by using an appropriate lignin, catalyst and solvent mixture.