Fischer-Tropsch Synthesis – investigation of Co catalyst by exposure to aerosol particles of potassium salts
Ljubiša Gavrilovića*, Edd A. Blekkana, Anders Holmena, Hilde J. Venvika, Jan Brandinb
aNorwegian University of Science and Technology, Department of Chemical Engineering, Sem Sælands vei 4, 7491 Trondheim, Norway.
*ljubisa.gavrilovic@ntnu.no
bLinnæus University,Department of Built Environment and Energy Technology, 351 95 Växjö, Sweden.
It is believed that the world’s population is approaching steady-state, but future energy supplies will be insufficient to satisfy population demand1. Looking at the fossil fuel consumption in the world, large and significant part is used in the transport sector which holds one quarter of overall usage of fossil fuels2. One alternative option for production of transportation fuels is by Fischer-Tropsch synthesis. Although fuel production via Fischer Tropsch synthesis from natural gas is well established, a lot of unsolved issues are related to the same procedure but using biomass as feedstock. The purpose of this work is better understanding of the alkali influence on Co-based F-T catalyst, especially potassium species which will be present in the syngas derived from biomass gasification3. From previous work it has been shown that alkali species act as poisons, thus deactivating catalysts4. The idea is to develop a technique to transfer potassium species in vapor phase to the catalyst surface.
Using aerosol technology for potassium deposition will in great extent simulate real industrial process. Experiments can be performed in situ, which describe more realistic picture of the effect of potassium. Previous similar work on Ni catalyst in the SCR reaction, has proven a loss in metallic surface area, decreasing of metal dispersion and severe reduction in catalytic activity using aerosol technology as a method of deposition5. In this work 20%Co/0.5%Re/γAl2O3 catalysts were exposed to the 4 different potassium salts (KCl, K2SO4, KNO3, K2CO3) in the form of aerosols. The amount of potassium deposited is directly related to the time of exposure, and target (estimated) amounts of 200 ppm, 800 ppm and 4000 ppm were deposited. Poisoned catalysts were characterized using elemental analysis, H2 chemisorption, N2 adsorption, and temperature programmed reduction. Fischer-Tropsch synthesis were performed at the in house build set up6 at 210°C, 20 bar and at H2:CO ratio of 2.1. Results were compared to the same catalyst without any poison and with the catalyst which was used incipient wetness impregnation as a method for potassium deposition7.
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