Analysis of the effect of temperature and reaction time on yields, compositions and oil quality in catalytic and non-catalytic lignin solvolysis in a formic acid/water media using experimental design

The catalytic solvolysis of Norway spruce (Picea abies L.) lignin in a formic acid/water media was explored at different temperatures and reaction times (283-397°C and 21-700min, respectively). Non-catalyzed experiments were compared with the effect of three different type of bifunctional catalysts (Pd/Al₂O₃, Rh/Al₂O₃ and Ru/Al₂O₃) and a solid Lewis acid (γ-Al₂O₃). We demonstrated that surface response methodology (RSM) and principal component analysis (PCA) were an adequate tool to: (i) evaluate the effect of the catalysts, temperature and reaction time in the oil yield, oil quality (H/C and O/C ratios, and M_w) and composition of the oil, (ii) establish the differences and/or similarities between the three bifunctional catalyst and (iii) to determine the role of the noble metal and the alumina support in the reaction system. In addition, the most active catalysts, Ru/Al₂O₃, and the optimum reaction conditions were determined (i.e. 340°C and 6h).