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978-3-8439-2935-6, Reihe Technische Chemie
Darstellung von 1,3-Butadien auf Basis von Ethanol in einem zweistufigen Verfahren
172 Seiten, Dissertation Rheinisch-Westfälische Technische Hochschule Aachen (2016), Softcover, A5
The formation of 1,3-butadiene from ethanol in a continuous two-step process has been investigated. In the ﬁrst step, copper and silver catalysts, supported on SiO2, were used to partially dehydrogenate ethanol to acetaldehyde. In particular, Cu\SiO2 proved due to its increased selectivity and improved lifetime as a suitable catalyst. This is mainly attributable to mild reaction temperatures of 195 °C. Therefore, Cu\SiO2 has been used in further experiments.
In the second step the conversion of the ethanol\acetaldehyde mixture has been examined. Here, two material parameters have been in focus. First, the ratio of acidic to basic centres has been varied, by doping and ion exchange of three commercial zeolites with diﬀerent modules. As a result, a series of catalysts with diﬀerent acidic-basic properties has been obtained. At the same time it was possible to keep other parameters, such as the speciﬁc surface area and the pore volume, constant. Besides a high 1,3-butadiene selectivity up to 72 %, a direct correlation could be drawn between the eﬀective acidity and the selectivity towards 1,3-butadiene and the dehydration products ethylene and diethyl ether, respectively, as well as the ethanol conversion.
The second part dealt with the attempt of introducing mesopores through desiliﬁcation of diﬀerent BEA and MFI zeolites. Especially silicon rich BEA structures emphasized as too unstable. Desiliﬁcation often led to a distinct dissolution of the zeolitic structure and therefore the variation of several material parameters and a total collapse of the catalytic performance. MFI type zeolites and BEA with a lower module suited better. Although the formation of deﬁned mesopores was not possible, selectivities up to 80 % have been reached. Finally, mesoporous LTA type zeolites have been synthesized through templating. The resultant materials showed varying mean pore widths, which had a direct impact on the catalytic activity. The ethanol conversion increased signiﬁcantly with the pore width.