Optimization of Lignin Degradation to Vanillin over Cu/Al2O3 Catalyst

Abstract

Optimizing for lignin degradation into vanillin over Cu/Al₂O₃ catalysts was carried out using an experimental design (Box-Behnken Design) in conjunction with Response Surface Methodology (RSM). The effects of all four factors: temperature (80-140 °C), sodium hydroxide loading (1-2 g), reaction time (30-90 min), and catalyst loading (0-1 g) were investigated. The vanillin concentration produced was used as the response variable. The results obtained have been used to generate a regression equation with acceptable accuracy (R²=78.81%). It was shown that an increase of sodium hydroxide increased the vanillin content. It may be due to the treatment of alkalinity during the reaction reducing the lignin precipitation. However, the longer reaction time resulted in lower vanillin yield, possibly due to vanillin breakdown. The best conditions to break down lignin to obtain vanillin were expected to occur at 80°C, reaction time of 48 min, sodium hydroxide of 1.38 g, and catalyst amount of 0.98 g, resulting in the mean vanillin yield at 5.65 ± 0.04 %.