(207c) Improved Pyrolysis Oil Properties Through Catalytic Deoxygenation

Pyrolysis oil prepared by conventional (non-catalytic) fast pyrolysis is not suitable for integrating into the current fuel infrastructure or into a petroleum refinery. Negative properties of conventional pyrolysis oil include: a) thermal instability and high fouling tendency, b) corrosiveness due to high carboxylic acid content (pH 2.2 – 2.4 typically), and c) immiscibility with refinery feedstocks.   Many of these properties are hypothesized to result from the high oxygen content (>38 wt%, dry basis) of the pyrolysis oil.  RTI is screening a wide variety of catalysts in multiple reactor systems to identify highly active and selective catalysts that reduce the oxygen content of the resulting bio-crude.

A bench-scale entrained flow biomass pyrolysis reactor with a downstream vapor phase upgrading reactor is utilized with a series of over 15 catalysts spanning a range of catalyst functions. Catalyst screening was performed with a nominal biomass feed rate of 100 g/hr and a white oak feedstock at temperatures between 350°C to 500°C, similar to pyrolysis temperatures.  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.  To address thermal instability, a residual testing methodology was developed and a variety of bio-oils and other hydrocarbons have been screened to determine the ability to re-vaporize the condensed bio-oils.  The quantity and characteristics of the residual material formed during the vaporization is compared with the bio-oil’s characteristics, primarily oxygen content but also acid content.

Selected catalysts are also tested in a bench-scale fluidized bed reactor where the biomass is injected directly into a fluidized bed of catalyst particles to determine product yields for catalytic biomass pyrolysis.  Comparisons between vapor phase upgrading and catalytic pyrolysis are made.  The most significant difference being lowered gas yields.  This screening is directed toward developing a catalytic process to produce a pyrolysis product that is more suitable for upgrading with traditional refining process technology.