Optimal Flowsheet Design for Levulinic Acid Production from Lignocellulosic Biomass: a Superstructure-based Approach

Levulinic acid is one of the twelve sugar-based building blocks selected by the US Department of Energy as the most promising biobased chemicals. The highest potential is due to the market projection of its products, such as additive for fuels (methyl tetrahydrofuran and levulinate esters), biodegradable herbicide (delta-amino acid levulinic), resins and plasticizer (diphenolic acid). The levulinic acid can be produced from lignocellulosic biomass, the most abundant and renewable feedstock, that do not compete with food production and address sustainability for biorefineries. However, this transformation is not economically feasible yet. The search for feasibility resulted in a significant number of process alternatives, which makes the flowsheet design a complex and challenging task. The present study addresses this issue by defining a superstructure that gathers some of the most promising processes described in the literature. The alternatives were modeled and combined in a mixed-integer linear programming problem that maximize the economic objective function. The optimized process flowsheet resulted in the dilute acid pretreatment of the biomass, followed by direct conversion of cellulose into levulinic acid by HCl catalysis, the solid-liquid separation of humins, flash separation of HCl, and liquid-liquid extraction and distillation of the products. This process configuration resulted in a net present value of 818 million US$, and an internal rate of return of 36%.