Vanillin production from lignin: Rigorous process simulation results for ethyl acetate versus aliphatic-alcohol-specific process designs

Abstract

Energy hotspots for the production of vanillin from Kraft lignin are identified and process improvements are proposed and rigorously simulated. The hotspots identified and addressed are related to the flowrate of methanol used as solvent and recycled in the process. Several alternative process designs containing fewer distillation columns and able to reduce the overall energy consumption are proposed. Recycling aqueous methanol, a distillation column is not required and the overall energy consumption is halved compared to the available literature (i.e. 42 %). In addition, based on a literature review and the screening of suitable solvents used for the liquid-liquid extraction of vanillin from the main product stream, the use of aliphatic alcohols such as hexanol is proposed as an optimal and underexplored solution. Their physicochemical properties allow for the elimination of the acidification step that takes place during the feed preparation stage at the beginning of the process. In this way, the process design can be simplified further. Two distillation columns are not required and the overall energy consumption of the process is reduced to 23% compared to previous studies. The proposed Kraft-lignin-based vanillin production process improvements contribute to the development and competitiveness enhancement of biomass-based vanillin production processes, which are currently in need of further refinement compared to the more mature petrochemical-based processes, but at the same time have the potential to be more sustainable, cleaner and energetically efficient.