Corrosivity and composition of raw and treated pyrolysis oils

Fast pyrolysis offers a relatively low cost method of processing biomass to produce a liquid product that has the potential for conversion to several types of liquid fuels. The liquid product of fast pyrolysis, known as pyrolysis oil or bio-oil, contains a high oxygen content primarily in the form of water, carboxylic acids, phenols, ketones and aldehydes. These oils are typically very acidic with a Total Acid Number that is often in the range of 50 to 100, and previous studies have shown this material to be quite corrosive to common structural materials. Removal of at least some of the oxygen and conversion of this oil to a more useful product that is considerably less corrosive can be accomplished through a hydrogenation process. The product of such a treatment is considered to have the potential for blending with crude oil for processing in petroleum refineries. Corrosion studies and chemical analyses have been conducted using as-produced bio-oil samples as well as samples that have been subjected to different levels of oxygen removal. Chemical analyses show treatment affected the concentrations of carboxylic acids contained in the oil, and corrosion studies showed a positive benefit of the oxygen removal. Results of these studies will be presented in this paper.