Tungsten based catalysts for selective deoxygenation

Abstract

Over the past decades, impending oil shortages combined with petroleum market instability have prompted a search for a new source of both transportation fuels and bulk chemicals. Renewable bio-based feedstocks such as sugars, grains, and seeds are assumed to be capable of contributing to a significant extent as fuel and bulk chemical sources.[1] However, utilization of these new types of high-oxygen-content feeds as either fuels or bulk chemical precursors is not trivial. Triglyceride or fatty acid feeds have the potential to be used as fuel because of their structural resemblance to diesel-type hydrocarbons, but further processing is required to reduce their high-oxygen content and related acidity.[2] This goal is typically achieved by hydroprocessing, thus resulting in deoxygenation (DO) of the triglyceride/fatty acid feed and yielding either saturated hydrocarbons suitable for diesel fuel, or linear olefins suitable for bulk chemical precursors. Although extensive studies have been done on deoxygenation of biomass-related feeds,[2, 3] catalyst research has so far been limited to supported noble-metal catalysts known for their hydrogenation activity and standard hydrodesulfurization (HDS) catalysts. The use of HDS catalysts can be problematic since catalyst deactivation resulting from sulfur leaching will result in contamination of the product stream.[4] The major drawback of noble-metal catalysts is their limited availability. Herein we demonstrate the use of tungsten-based catalysts for the deoxygenation of triglyceride-based feedstocks. Changes in a (pre)treatment procedure are shown to control catalyst selectivity, thus allowing high yields of unsaturated products even in the presence of hydrogen.