Catalytic tar removal from bio syngas—Catalyst development and kinetic studies

Abstract

One of the most demanding areas of current energy research is related to the production, use and integration of fuels from renewable, i.e. CO 2 neutral, primary energy sources. The generation of biofuels of the second generation requires the gasification of biomass. Thereby considerable amounts of tar are formed in the crude gas. These impurities must be removed before further processing via Fischer–Tropsch or methanol synthesis [1]. For energy efficiency reasons of the whole process, the catalytic hot-gas-cleaning is a promising method. The operating temperature range from 450 to 700 °C results from the outlet temperature of the gasification process and the working temperature of the following synthesis steps. By means of selective, oxidative tar removal on Mo/V/W-mixed oxide catalysts tar compounds can be removed systematically, without converting the synthesis gas components hydrogen and carbon monoxide [2,3]. Therefore, stationary and transient kinetic experiments were performed with naphthalene as tar model compound on Mo/V/W-catalysts [4]. In the temperature range of interest Mo/V/W-mixed oxides show the required performance [5]. That way the total conversion of 2500 ppm naphthalene with an oxygen-feed of 3% (L L −1) is already obtained at 425 °C. At the same time no conversion of CO and H 2, and, therefore no disturbance of the synthesis gas yield takes place. It turned out that the selective oxidation of the tar ingredients in crude synthesis gas on mixed oxide catalysts is a promising alternative for the tar removal in the required temperature range.