Techno-economic assessment of two-stage hydropyrolysis of lignin for BTX production using iron-based catalysts†

Abstract

The thermal degradation of the lignin contained in biomass, followed by catalytic upgrading of the resultant bio-oil, offers a promising renewable generation pathway for aromatic commodity chemicals, in particular benzene, toluene and xylene (collectively ‘BTX’). The primary barrier to widespread adoption of this technology is its economic unfavourability relative to petroleum-derived BTX production. Previous work has determined that iron-based zirconium oxide catalysts for the hydrodeoxygenation (HDO) upgrading step are able to selectively generate aromatic hydrocarbons (up to 12 wt%) and minimise catalyst coking. The techno-economic assessment (TEA) of a hypothetical industrial-scale biomass hydropyrolysis plant, converting 2000 tonnes per day of lignin waste into commodity chemicals using FeReO_x/ZrO₂ and Fe/ZrO₂ catalysed HDO respectively in scenario 1 (S1) and scenario 2 (S2), was investigated. The TEA was carried out by constructing a robust model that integrates both technical and economic aspects of the process. A Monte Carlo-type sensitivity analysis was then used to examine the sensitivity of the predicted earnings. With the yearly Cost of Manufacturing (COM) estimated to be 88/158 M£ per year and revenues predicted to be 116/171 M£ per year, the base-case processes were predicted to make a yearly gain of approximately 27.6 and 12.7 M£ per year respectively in scenarios 1 and 2, with the sensitivity analysis yielding gross earnings of approximately 65% (S1) and 95% (S2) of simulations. The variable to which the profitability was most sensitive was found to be the bio-oil yield, and maximisation of this yield is recommended as a focus of further research.