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Study of a nickel-based and a nickel-ruthenium based catalyst supported on the SBA-15 material in dry reforming of methane to produce synthesis gas

Papachristou Georgios

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Summary

In the present diploma thesis, two catalysts, one nickel-based and one nickel-ruthenium-based, both supported on the SBA-15 mesoporous silica in the dry reforming of methane are examined, in order to determine which one exhibits the best catalytic behavior. The dry reforming of methane is an endothermic chemical reaction that converts two greenhouse gases, namely methane and carbon dioxide, into synthesis gas, namely hydrogen and carbon monoxide. The aggravation of the greenhouse effect but also the continuous exhaustion of conventional forms of energy sources, add scientific interest to this reaction, since hydrogen, which is pure fuel and can be used in fuel cells, could be isolated from the synthesis gas produced. Also, the use of synthesis gas directly in fuel cells is continuously studied. The dry reforming of methane is consistent with heterogeneous catalysis, that is, the use of certain substances called catalysts (which are in a different phase from the reaction substances), in order to increase the rate of the reaction. In recent years, nickel monometallic catalysts as well as bimetallic ones such as nickel-ruthenium have been widely used in this process, since noble metals such as ruthenium appear to function effectively as promoters. Also, the SBA-15 mesoporous silica, according to the references, is really effective as a support. The two catalysts examined here had a composition of 5,87%wt Ni/SBA-15 and 3,0%wt Ru-4,13%wt Ni/SBA-15 respectively and were constructed at the laboratory. Experiments were performed to characterize the catalysts using the BET (Brunauer Emmet Teller), hydrogen chemisorption and hydrogen TPR methods. Stability experiments were also performed to test the catalytic performance of the two catalysts, under both reducing and oxidizing conditions. The basic efficiency of the catalysts was examined through kinetic experiments (light off), i.e. through the study of the dependence of each conversion percentage (of reactants) and yield percentage (of products) on temperature. After execution of the experiments and processing of the results, it was found that the nickel monometallic catalyst supported on SBA-15 showed greater stability than the nickel-ruthenium bimetallic catalyst supported on SBA-15. The specific one also showed greater activation after oxidation. The promotional effect of ruthenium appears only in the first hours of the stability experiments.

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