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TU Berlin

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Research for a more effective usage of energy

In near future, fossil fuels like coal and oil will be exhausted. Since our industrial prosperity is based on energy supply, securing of that will be the major challenge today. Simultaneously, ecological aspects have to be respected. For this purpose, two different possibilities are provided: On the one hand existing reactions can be made more energy efficient with other catalysts. This helps to save energy, reduces the pollution of the environment and makes the process sustainable. The second possibility is to find new ways of synthesis using cheap raw materials which are by-products of other processes and cannot be ulterior used. This way provides a gentler handling with our resources and helps to make the process cheaper.

As part of the first efforts, we work on an alternative way to provides hydrogen for fuel cells in mobile devices. Fuel cells seem to be a promising kind of securing our mobility without dependency of petroleum. Currently, these devices are driven with pure hydrogen / lower alcohols and oxygen. The storage and handling of pure hydrogen is difficult: Small amounts of hydrogen in air already form explosive mixtures and because of the small molecule size, hydrogen runs through most of the common materials which leads to a loss of gas during storing. The liquidation of hydrogen is also unfavorable, it is too energy consuming. A promising way to store hydrogen is the chemical storage. Therefore, hydrogen containing substances like methanol or ethanol are used as fuel which is, together with water, converted to hydrogen and carbon mono- and dioxides in-situ in steam reforming process. However there are two disadvantages: Carbon dioxides, a greenhouse gas, is produced and the produced carbon monoxide destroys the expensive platinum membrane of the fuel cell.
Ammonia represents another promising storage media, which is not offering these disadvantages. It provides one and a half of the hydrogen molecules per volume than pure hydrogen. The handling and storing are much easier and no greenhouse gases are generated during formation of hydrogen.
We investigate new catalysts for this reaction to find a way for decreasing the reaction temperature and make the process profitable. For this purpose, we work together with two other workgroups synthesizing and analyzing the catalyst samples. Investigation of the reaction, finding and describing the veritable reaction mechanism, optimizing the reaction parameters and taking these consolidated findings to give new impulses for the synthesis group - these are our responsibilities in this research network. For catalytic testing, a fully automated experimental setup is provided in which short catalyst screening as well as long-term runs can be performed. Hence, the process parameters - temperature and concentrations of products and educts - can be varied over a wide range to get the best possible base for analyzing and interpreting the data.

As part of the second efforts, we work together with Bayer Company and some universities in German or Spain to optimize the catalyst efficiency and to looking for new catalysts or catalysis systems which consume less energy for the chlorine production from hydrochloric acid, which is a byproduct of many industrial reactions.

The current recycling process of HCl to Cl2 is the electrochemical oxidation reaction with Ruthenium catalyst. This galvanic process spends much energy and Ruthenium is an expensive material. It makes economically and ecologically sense to optimize the efficiency of the practicing system in respect of the material usage and to compare the known processes to reoxidize hydrochlorid acid. One part of the research groups investigates the electrochemical reaction and other groups investigate the gas phase reaction. The gas phase reoxidation of hydrochloric acid (Deacon Reaction) seems to be an interesting alternative since the electricity tariff goes more and more expensive in the last years.

Ruthenium catalyst was chosen as the benchmark. A series of Ru catalyst was tested and the best one in respect of the activity and stability would be measured more detail. The characterization and the theoretical calculation are made by other research groups; our part is the kinetic study of the oxidation of HCl by O2 on Ru catalyst. A mechanistic reaction model is proposed and compared with other reaction model. The influence of product gases is also investigated due to validate the proposed reaction models.

The results of the investigation should give a better understanding of the reaction system and this should provide a basis for further improvement of the catalyst or respectively for the development of the screening strategy in order to find alternative catalysts which should achieve a high performance at milder reaction conditions.

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