Butadiene from ethanol employing doped t-ZrO2

The synthesis of 1,3-butadiene (BD) from ethanol is a complex reaction system in which several steps are involved. The use of zirconia-based catalysts as well as physical mixtures containing Cu/ZnO/Al2O3 (CZA) and t-ZrO2 were evaluated in order to better understand this reaction. The catalysts employed were characterized by the following techniques: TPSR-IR, NH3-TPD, CO2-TPD, XRD, SEM/EDS and BET. Moreover, the isopropanol conversion and the acetone and ethanol reaction (Meerwein-Ponndorf-Verley mechanism (MPV)) were used as model reactions to describe the catalysts behavior. It was verified that doping oxides with metals is a very simple procedure in order to change the properties of the catalysts so as to reach the requirements of the butadiene synthesis. Doped t-ZrO2-based catalysts are promising systems for the BD generation from ethanol. The addition of Na and Ag to t-ZrO2 promotes the selectivity towards BD and decreases the selectivity to ethylene. The catalyst with Ag is more active than the one with Na. It was observed that employing physical mixtures, the dehydrogenation rate of ethanol should be consistent with the activity of the catalyst toward the aldol condensation and the MPV step. The physical mixture with low concentration of CZA generates high BD yield. The ZrO2 catalytic behavior in the MPV step, and also in the BD synthesis changes according to the crystalline structure of this oxide.