467676 Hydrogen Production By Steam Reforming of Bio-Oil Derived Acetic Acid over Ni Based Zr-SBA-15 Type Mesoporous Catalysts
CH3COOH + 2H2O ↔ 4H2 + CO2 (R.1)
CO + H2O ↔ H2 + CO2 (R.2)
Synthesis of active, stable and selective catalysts for steam reforming of acetic acid is a hot research area for the development of new renewable energy processes. Nickel is one of the most active catalytic metals for reforming reactions. Type of support material is expected to have strong influence on the performance of Ni based catalysts in steam reforming of AcOH. Invention of silicate structured mesoporous materials, like MCM-41 and SBA-15, opened new avenues in catalysis research. These materials, with ordered pore structures, were reported to be less susceptible to deactivation due to coke formation than the conventional microporous catalyst supports. They also cause less resistance to diffusion of reactants to the active sites. However, some of the silicate structured mesoporous materials were known to have low hydrothermal stability in the presence of water vapor. Zirconia, with its high thermal and chemical stability attracted the attention of catalysis researchers in recent decades. Strong interaction of Ni clusters with zirconia and quite high water dissociation capacity of zirconia were reported as attractive properties of this material in steam reforming reactions. More recently, zirconia incorporated SBA-15 was reported as a highly stable catalyst support for steam reforming of ethanol . In the present study, zirconia incorporated SBA-15 type mesoporous materials with different Zr/Si ratios were synthesized following a one-pot hydrothermal route, characterized and used as the catalyst support materials for the synthesis of new Ni based catalysts to be used in steam reforming of AcOH. Some of these Ni based catalysts were modified by addition of tungsten, during the impregnation step. Catalytic performances of these materials were tested in steam reforming of AcOH at 750 oC. Synthesized Zr-SBA-15 type support materials were shown to have ordered mesopore structures with high surface area values. For instance, the material containing 25% zirconia in SBA-15 (25Zr-SBA-15) had a surface area of 608 m2/g, while some decrease of surface area was observed as a result of Ni and W impregnation. For instance, the catalysts containing 5% Ni (5Ni@25Zr-SBA-15) and 5% Nİ+10% W (5Ni-10W@25Zr-SBA-15) had surface area values of 561 m2/g and 151 m2/g, respectively. Catalytic activity tests proved that the performance of the Zr-SBA-15 supported Ni based catalysts were highly stable and they also showed very high activity in steam reforming of acetic acid, giving complete conversion at temperatures over 700 oC, at space time of 0.072 s.g.ml-1. Product distributions were shown to be strongly influenced by the composition of the catalyst. In the case of 5Ni@25Zr-SBA-15, syngas produced at 750 oC contained about 54 % H2, 22% CO, 20% CO2 and 4% CH4. These results indicated that thermal decomposition of AcOH to methane and CO2 was minimized over this catalyst. Results were considered to be highly promising from the point of view of production of hydrogen rich syngas. It was most interesting to observe that modification of this catalyst by the addition of tungsten caused significant changes in the product distribution. For instance, syngas produced over 5Ni-10W@25-SBA-15 at the same reaction conditions, contained equimolar quantities of H2 and CO (about 47.5 % each) with very small amounts of CO2 and CH4 (about 3% and 2%, respectively). Production of a syngas with such a composition was considered to be highly attractive from the point of view of a resource gas for DME and Fischer-Tropsch synthesis. Activity test results obtained with different catalyst compositions and at different reaction conditions, as well as the characterization results of the synthesized catalytic materials, will be reported in this presentation.
Acknowledgements: TUBITAK Project (214M578) and TUBA.
 Goicoechea S., Kraleva E., Sokolov S., Schneider M., Pohl M.M., Kockmann N., Ehrich H., Appl. Catal. A: Gen. 514 (2016) 182.
 Arslan A., Gunduz S., Dogu T., Int. J. Hydrogen Energy, 39 (2014) 18264.
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