(592f) Low-Oxygen Bio-Crude From Hydropyrolysis in a Pressurized Fluid-Bed Reactor

Pyrolysis oil prepared by conventional (non-catalytic) fast pyrolysis is not suitable for integrating into the current fuel infrastructure or into a petroleum refinery because it is : a) thermally unstable with a  high fouling tendency, b) corrosive due to high carboxylic acid content (pH 2.2 – 2.4 typically), and c) not miscible with refinery feedstocks.   Fast pyrolysis bio-oil tends to have high oxygen content similar to the solid biomass feedstock used as the starting material.  The thermal instability and high water content require specialized hydroprocessing to lower the oxygen content of the bio-oil before use.  Hydropyrolysis is a biomass thermal liquefaction process option that combines biomass, hydrogen, and a catalyst to integrate pyrolysis and a degree of hydroprocessing into a single unit operation.

The National Advanced Biofuels Consortium (NABC) is working to develop sustainable, cost-effective processes to produce advanced “drop-in” biofuels that are compatible with today’s transportation infrastructure.  As part of the NABC, the hydropyrolysis of loblolly pine has been explored to produce low-oxygen content bio-crude.  A pressurized fluid-bed reactor was designed and fabricated to test catalysts and reaction conditions (T, P, and pH₂).  Testing was performed with a nominal loblolly pine feed rate of 200 g/hr at temperatures between 350°C to 500°C and pressure  up to 300 psig with varying hydrogen concentrations.  Full mass closures are obtained by measuring all liquid, solid, and gas products.  Bio-crudes are characterized by ultimate analyses, Karl-Fischer titration, total acid number (TAN), pH, and GC/MS.    In addition to parametric testing, several catalysts were screened and performance with a corn stover was evaluated.

A selected catalyst was tested over an extended trial of 32h on stream with over 8kg of biomass. Consistent activity was observed based on product yields and composition when catalyst regeneration occurred after conversion of 1 kg of biomass.  The liquid product separated into an aqueous layer that was 97wt% water and a bio-oil that was less than 1wt% water and had an oxygen content of 2.5wt%. The bio-crude had high levels of aliphatic and aromatic compounds with reduced concentrations of acids, sugars, and ketones in comparison with conventional fast pyrolysis bio-oil.  Hydropyrolysis has the potential to produce bio-oils with improved properties and suitability for integration into refinery processes.