Esterification of Pyrolysis Liquids as Stabilizing Upgrade Step
Liquid condensates from flash pyrolysis of biomass are not easy to use even in simple combustion applications due to its disadvantageous properties like high water content, low heating value, high viscosity and especially high content of carboxylic acids. Furthermore, the condensates from straw pyrolysis disintegrate into a two-phase liquid, which is even less applicable. To convert these liquids in a form applicable for standard equipment, the properties must be changed. A potential treatment is the esterification with an alcohol not miscible with water. The reaction masks the carboxylic acids and water can be removed from the product. The resulting mixture shows much better quality for the application in standard equipment. The total acid number could be reduced by one order of magnitude and the water content could be reduced from 26 to below 2 % in the best case. The reaction of pyrolysis liquid with an alcohol is extremely promising especially for straw as feedstock, because it converts a nasty, two-phase sludge into a mildly viscous, single-phase liquid with acceptable higher heating value (30.2 MJ/kg).