Process Superstructure Optimization for Resin and Aromatic Monomer Production from Kraft Lignin

Abstract

Kraft lignin conversion to value-added products is an alternative way to manage the main pulp and paper secondary stream thus contributing to reducing avoid greenhouse gas emissions compared to equivalent fossil-based processes. Process simulation and integration can help to identify the most promising pathways and increase the profitability of the process. This work presents results of a comparison between the process optimization of two different potential products that were modeled and analyzed. Aromatic monomers and phenol-formaldehyde resins were considered as possible products by means of alternative process pathways, including hydrothermal liquefaction, hydrodeoxygenation, pyrolysis, dissolution with deep eutectic solvents, hot water extraction, and resin synthesis. Mixed-integer nonlinear programming was applied to optimize the superstructure and obtain the maximum lignin cost. A sensitivity analysis in terms of the final products selling price was performed to consider the market variability. Minimum selling prices of aromatic monomers and phenol-formaldehyde resins for a feasible lignin process were calculated. Maximum lignin cost larger than 100 €/t resulted acceptable only for phenol-formaldehyde resins selling price larger than 0.6 €/kg or for AM selling price larger than 1.80 €/kg. Aromatic monomers turned out to be the optimal product if its selling price is larger 1.20 €/kg and the phenol-formaldehyde resins cost is lower than or equal to 0.6 €/kg. Higher phenol-formaldehyde resins selling prices make this product more convenient.