(670f) Advanced Biofuels Development Through Catalytic Biomass Pyrolysis

RTI is developing an advanced biofuels technology that integrates a catalytic biomass pyrolysis step and a hydroprocessing step to produce infrastructure compatible biofuels. The focus of this development is  to optimize the catalytic biomass pyrolysis process to achieve high degree of deoxygenation, while maximizing the bio-crude production; improve bio-crude thermal stability; evaluate the impact of bio-crude quality in the hydroprocessing step; minimize hydrogen demand of the integrated process, and maximize biofuels yields.  RTI’s technology development process has spanned catalyst screening with model compounds to validation of catalyst performance with biomass in a bench-scale fluidized bed to design and fabrication of a 1 ton per day biomass feed pilot plant. 

A key goal of the catalyst screening was to optimize a catalyst formulation with high deoxygenation activity and minimal carbon loss to gas (CO and CO₂) and coke formation.  An automated microreactor system was developed to investigate deoxygenation chemistry in support of the catalyst development for direct biomass liquefaction pathways.  Guaiacol was  selected as one of the model compounds because it is a thermally-stable liquid that vaporizes at typical biomass pyrolysis temperatures (300°C - 500°C) and contains methoxy and hydroxyl functional groups that commonly occur in primary pyrolysis products. Rapidly catalyst screening was carried out at various temperatures (300°C - 500°C), pressures (up to 350 psig), hydrogen partial pressures, and space times. Long term catalyst performance can also be evaluated over 100’s of hours in extended reaction/regeneration catalyst tests at a single condition to simulate operation in a continuously circulating reactor. Catalysts with high activity for guaiacol deoxygenation with relatively low coke formation were identified for additional testing in catalytic fast pyrolysis systems.

Catalytic biomass pyrolysis was then carried out with Identified catalysts to explore their effectiveness for deoxygenation of biomass pyrolysis vapors.  Catalytic fast pyrolysis screening was performed in a 1 inch diameter bench-top fluidized bed with a catalyst loading of approximately 30g. This reactor produces sufficient oil yields for analysis and minimizes required catalyst synthesis. Comprehensive analysis of all product streams with high mass closure (>90%) aided the evaluation of catalytic activity. Over 70% reduction in the oxygen content of the catalytic fast pyrolysis bio-crude has been observed with selected catalysts compared to conventional bio-oil. Compositional analysis by GC/MS indicated compositional changes such as reduction in sugars and acids as a function of catalyst and process conditions.  Bench-scale testing based on conventional hydroprocessing technology was used to  upgrade 1L of  bio-crude into gasoline and diesel range hydrocarbons.

At the current stage of development, the catalytic biomass pyrolysis process is being scaled-up in a 1 ton-per-day pilot plant based on a transport reactor design, integrated with a hydroprocessing unit, and demonstrated over the long-term operation and performance of the integrated process. The chemistry of biomass pyrolysis is manipulated by the catalyst and by controlling the pyrolysis temperature, vapor residence time and biomass-to-catalyst ratio. RTI has discovered a novel catalyst that effectively deoxygenates biomass pyrolysis vapors in a catalytic biomass pyrolysis process. This produces a low oxygen-content, thermally stable bio-crude intermediate for upgrading into advanced biofuels.