Pilot‐Scale Study of Ethylene Synthesis by Ethanol Dehydration on Acid‐Modified Alumina Catalysts
Bioethanol coming from lignocellulosic biomass could play an important role in the future as a primary feedstock in the chain of possible organic chemicals based on renewable materials. As a key intermediate, bioethylene produced from bioethanol can secure the downstream synthesis of a number of valuable products such as PE, PVC, glycols, ethylene oxide, etc. Ethanol can be converted into ethylene by catalytic dehydration using a variety of catalysts, preferably alumina ones [1, 2]. The present work was focused on the experimental study of ethylene synthesis by ethanol dehydration: started from the search for the catalysts, ended by the pilotscale process study. The proprietary technique of hydrargillite (or gibbsite) centrifugal thermal activation (CTA) in TSEFLAR™ apparatus  is considered as environmentally friendly and economically attractive. Preliminary, a set of aluminabased catalysts prepared after СTA technology has been studied on the laboratory setup at 0.27-0.6 s and 375-400 °C. Of them, the HNO3-modified Al2O3 was selected as the most active and stable catalyst. The acid-modified alumina catalysts in the form of 4 mm cylinders and 1.6 mm trilobes were used for ethylene synthesis in the pilot-scale setup with U-tube fixed-bed reactor, ID = 28 mm, L = 2800 mm. Process conditions were varied within: ethanol feed 1.5-2.5 kg/h, thermostat temperature 390-450 °C, catalyst bed height 0.65-1.2 m. The best results were obtained at the residence time 2.4-3.0 s and the thermostat temperature 405-420 °C, the ethylene selectivity was as high as 97.6-98.6 % mol, and the consumption index of ethanol to ethylene was as low as 1.64-1.73 kg/kg.