Formation of 1,3-butadiene from ethanol in a two-step process using modified zeolite-β catalysts

• Cu\SiO2 presents an active and long term stable catalyst for dehydrogenation of ethanol to acetaldehyde.
• Selectivity towards 1,3-butadiene increases with increasing effective acidity.
• Selectivity towards the dehydration products ethylene and diethyl ether and ethanol conversion decreases with rising acidity.

Catalysts for the selective formation of 1,3-butadiene out of ethanol in a continuous two-stage gas-phase fixed bed reactor setup were developed. In the first stage, 20% acetaldehyde yield was aspired. This mixture was directly fed into the second stage facilitating enhanced selectivity to 1,3-butadiene. In the first stage, Ag\SiO2 and Cu\SiO2 were studied. Especially the copper based catalyst proved to be a selective and long-term stable system. In the second stage we tested different zeolite-β based catalyst systems which were modified in terms of their acidic and basic behaviour. We were able to reach 1,3-butadiene selectivities up to 72% at rather low temperatures of 573 K. Furthermore we could draw a direct correlation between the catalyst’s acidic and basic properties and their catalytic performance. The physical properties were analysed via X-ray diffraction, nitrogen physisorption, TGA–DSC and HRTEM. The chemical composition was determined by ICP-AES and SEM–EDX measurements. The investigation of the acidic and basic properties was realized by pyridine adsorption infrared spectroscopy and temperature programmed desorption with ammonia and carbon dioxide, respectively.

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