Influence of pressure on the performance of biomass based Fischer-Tropsch synthesis A. Sauciuc 1 , Z. Abosteif 2 , G. Weber 3 , A. Potetz 4 , R. Rauch 3 , H. Hofbauer 4 , G. Schaub 2 and L. Dumitrescu 1 1. Department of Renewable Energy Systems and Recycling, Transilvania University of Brasov, Department of Chemistry and Environment, Colina Universitatii 1, Brasov, 500068, Romania, phone/fax number: +40268472496, e-mail: anca.sauciuc@unitbv.ro 2. Engler-Bunte Institute, Karlsruhe Institute of Technology, Engler-Bunte-Ring 1, Karlsruhe, 76131, Germany 3. Bioenergy 2020+, Wienerstraße 49, Güssing, 7540, Austria 4. Institute of Chemical Engineering, Vienna University of Technology, Getreidemarkt 9/166, A-1600 Vienna, Austria Abstract The environmental concerns and the European liquid (bio)fuels regulations have determined a growing demand on biofuels. Fischer-Tropsch synthesis can provide clean synthetic fuels containing low concentrations of sulphur, nitrogen and aromatics. While Fischer-Tropsch synthesis using natural gas and coal is a well established and commercialized process for more than 70 years, the new technology of Fischer-Tropsch synthesis using biomass as feedstock is gaining more and more attention due to the possibilities of using renewable raw materials. In this work, in order to optimize the Fischer-Tropsch synthesis, the influence of pressure has been studied in a slurry reactor using a Co-based catalyst. Experiments were carried out with 24 bar, 20 bar and 16 bar keeping the other parameters (temperature 230 °C, gas flow 5-6 Nm 3 /h) constant. The effects of pressure on CO conversion, product distribution, C5+ selectivity, Par/Ole ratio and α value were investigated and the results were compared with data from literature. It was found that - increasing the reaction pressure - heavier hydrocarbons were formed and CO conversion increased from 44.2 % to 63.7%. A slight change has been observed in case of α value between 0.89 and 0.9, C5+ selectivity between 90.6% to 91.7% and Par/Ole ratio between 11.4 to 14.1. An important role for the results obtained was attributed to H2/CO ratio variation during the experiments. 1. Introduction The world dependence on fossil fuel reserves, correlated with the continuous depletion of the reserves and the growing concern about global warming and climate changes, makes renewable energy sources very attractive [1-3]. One of the promising routes to produce green fuels is the combination of biomass gasification and Fischer-Tropsch synthesis. This biomass-to-liquids (BtL) technology consists of the production of long chain hydrocarbons from synthesis gas, by three main steps: biomass gasification in order to produce syngas, FT synthesis and product upgrading by distillation and hydroprocessing [4,5]. Fischer-Tropsch synthesis offers the possibility of obtaining clean fuels and chemical feedstocks. The basic chemistry of the synthesis consists in the hydrogenation of CO molecules from syngas. The reactions involved in the FT process are extremely important for the industrial practice, FT design, scale-up, optimization and simulations [6]. A large number of species can be obtained in FT synthesis by the following equations [5,7,8]: (2n+1)H2 + nCO → CnH2n+2 + nH2O (Eq. 1)