Manganese and Zinc Supported on Zeolite (SiO ₂ /Al ₂ O ₃ = 5.1) Catalysts for Microwave-Driven Dehydration of Ethanol to Ethylene

This study explores the conversion of ethanol to ethylene (EtE) using a microwave-heated fixed-bed reactor, where dielectric heating selectively heats the catalyst bed, thus bypassing conventional conduction and convection limitations. Y-zeolite with an SAR of 5.1 was modified with manganese and zinc to tune the acidity, making it suitable for dehydrating ethanol, forming ethylene as a major product. Special emphasis was placed on studying the Brønsted acid sites (BAS) and Lewis acid sites (LAS), which are the prominent sites for the dehydration of ethanol. Pyridine-DRIFTS and NH3-TPD were used to study the BAS and LAS distribution among the catalysts. The high ethanol dehydration and ethylene selectivity was associated with the higher density of stronger acid sites determined using NH3-TPD. XRD and BET were used to study the surface properties of the catalysts. TGA was used to determine the amount of carbonaceous deposits over the spent catalysts. The reaction was conducted at temperatures of 250, 300, and 350 °C, while liquid ethanol was directly fed to the catalyst bed in the reactor at a flow rate of 0.1 mL/min. The findings reveal that the formulation with 8Mn-2Zn over the HY support at 300 °C is the most effective, with a selectivity for ethylene of over 99%.