(13c) Hydropyrolysis of Loblolly Pine to Produce a Low-Oxygen Pyrolysis Oil

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 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 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-oil.  An entrained flow reactor is utilized to test catalysts and reaction conditions (T, P, and pH₂).  Testing was performed with a nominal loblolly pine feed rate of 100 g/hr at temperatures between 350°C to 500°C and pressure  up to 350 psig.  Full mass closures are obtained by measuring all liquid, solid, and gas products.  Bio-oils are characterized by ultimate analyses, Karl-Fischer titration, total acid number (TAN), pH, and GC/MS. 

A selected catalyst was tested over an extended trial of 21h on stream with over 2kg of biomass. Initial high activity led to lower liquid yields early in the trial, however liquid yield increased with time on stream. The product distribution and composition was consistent over the latter half of the trial.  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 4wt%.  Hydropyrolysis has the potential to produce bio-oils with improved properties and suitability for integration into refinery processes.