(35c) Multistage Torrefaction of Biomass and in Situ Catalytic Upgrading to Hydrocarbon Biofuels and Specialty Biochemicals

Thermochemical conversion of lignocellulosic biomass via pyrolysis and catalytic upgrading of bio-oil is touted as an environmental panacea, capable of producing fuel, energy, and value-added bio-based chemicals with an improved environmental profile compared to conventional fossil routes. However, bio-oil contains a host of compounds with myriad chemical functionalities, making selective catalytic upgrading to fuel and/or chemicals challenging and a major technical bottleneck. This work explores an innovative design strategy, in which the primary constituents of lignocellulosic biomass (i.e. hemicellulose, cellulose, lignin) are selectively decomposed via a series of torrefaction and pyrolysis reactors. Staged thermal decomposition produces several fractionated bio-oil streams comprised primarily of light oxygenates, furan derivatives, and phenolic species respectively. The purposed multistage design permits tailored catalytic upgrading of the fractionated bio-oil streams to hydrocarbon fuels and/or specialty bio-based chemicals, and thus holds promise for improved environmental and economic performance over the current state of the art (i.e. fast pyrolysis and hydroprocessing fuel platforms).

This work performs a prospective life cycle assessment to determine the environmental profile of concurrent hydrocarbon biofuel and specialty biochemical production via a multistage torrefaction and in situ catalytic upgrading platform. Several multistage design strategies consisting of different catalytic strategies and targeted platform chemicals (i.e. 2-methylfuran, tetrahydrofuran, and cyclopentanone) are considered. Detailed material and energy balances for multistage systems are developed using a combination of experimental data and ASPEN process simulations. Several critical sustainability metrics including life cycle greenhouse gas (GHG) emissions and Energy Return on Investment (EROI) are used to compare the environmental performance of multistage systems, and benchmark against a base-case fast pyrolysis and hydroprocessing platform. Preliminary results reveal that multistage systems have the capacity of achieving over 75% GHG reductions relative to petroleum diesel, and produce high quality hydrocarbon transportation fuels and specialty bio-chemicals. The influence of different LCA allocation schemes and coproduct scenarios for the produced biochar on the environmental profile of hydrocarbon biofuels and biochemicals will be discussed.