Scaling-Up Catalytic Depolymerisation of Lignin: Performance Criteria for Industrial Operation

Much scientific research has been carried to convert lignin into valuable biobased chemicals or fuels. Most of these studies had the objective to develop active and selective catalysts for effective lignin depolymerization; this with little regard for the parameters that are necessary for later commercialization of these technologies. In this work, we have chosen as a case study a process that has been extensively studied and reported on earlier by our group. This process converts (technical) lignin into mainly aromatic compounds, using supercritical ethanol and a Cu–Mg–Al mixed oxide catalyst. Here, we investigate the impact of scaling up this process from lab to bench scale. More specifically, we study the influence of higher lignin loadings than previously reported on, amongst other parameters, monomer yield, solvent losses and catalyst fouling; all of which being critical performance parameters for industrial operation. After we examined the technical feasibility of our process at 4 L scale, we further looked into the economic viability of this technology, by introducing two performance criteria, both of which being a function of lignin monomer yield. The ratios (g/g) of yield over total feed, and yield over ethanol losses are presented as qualitative indicators for capital expenditure (CAPEX) and operational expenditure (OPEX), respectively. This exercise sheds some much needed light on the trade-off between yield optimization and cost minimization.