Renewable Fuel Production via Methanol-Assisted Biomass Liquefaction Process
Jiajia Meng1, Kevin McCabe1, Kelly Mastro1, Eric Larson2 and Santosh Gangwal1
1. Southern Research, 5201 International Dr, Durham, NC 27712
2. Princeton Environmental Institute, Princeton University, NJ 08544
firstname.lastname@example.org; (919) 282-1050
Biomass hydrothermal liquefaction (HTL) using compressed hot water requires severe reaction temperature (~350 °C) and pressure (~3000 psi) to deconstruct biomass constituents; it is therefore energy intensive, capital intensive and difficult to scale up. To advance the technology, this project aims to develop a low-severity methanol assisted hydrothermal liquefaction process to convert woody biomass into stabilized bio-oils. The bio-oil is targeted to be co-processed with petroleum streams using existing refinery infrastructure for the production of drop-in transportation fuel, leveraging existing refinery capital for bio-fuel production. The liquefaction conditions were optimized using a Parr reactor according to statistically designed experiments to achieve high biomass conversion, high bio-oil yield and relatively low oxygen content in the bio-oil. Under optimized conditions, the process achieved ~90% biomass conversion and ~50% bio-oil yield. Based on these experiments, a preliminary commercial embodiment of the liquefaction process was developed. The bio-oils were found to contain ~22% oxygen with low moisture (~1 wt.%) and acid content (total acid number 1-5 mg KOH/g dry oil). The molecular weight of the bio-oil did not vary significantly over a six-month room-temperature storage indicating their stable nature. Furthermore, at anticipated commercial conditions, the bio-oil produced were easily flowing liquid at 40oC. For refinery insertion purposes, these bio-oils were hydro-deoxygenated using a proprietary catalyst in a continuous ½’’ trickle-bed reactor for oxygen removal. The upgrading experiments showed that the bio-oil oxygen content could be reduced from 22 wt % to 1.5 wt % with low hydrogen consumption (<0.03 g/g dry bio-oil) under mild conditions. Characterization of the upgraded oil showed that it was essentially free of water and acid, and contained diesel-range hydrocarbons based on simulated distillation results. Also, the upgraded oil was miscible with a petroleum-based diesel, therefore enabling co-processing in the refinery. These results were applied to develop mass and energy balances of a commercial process for economic production of biofuel from biomass. A techno-economic evaluation and lifecycle assessment of the process was carried out.