Ethanol dehydrogenation over (K)(Co)MoS2catalysts supported on activated carbon: Effect of active phase composition

Abstract

The conversion of ethanol to synthesize various oxygenated hydrocarbons was studied over monometallic-, bimetallic-, and trimetallic-(K)(Co)MoS2-based catalysts supported on activated carbon. The catalysts were synthesized using the incipient wetness impregnation method and sulfidized with H2S. The catalysts were characterized by the following techniques: N2 adsorption-desorption, UV spectroscopy of pyridine-adsorption; scanning electron microscopy (SEM); SEM energy dispersive X-ray (EDX). SEM/EDX results revealed that the active metals formed a uniform phase. Synthesized catalysts were tested in a fixed-bed tubular reactor. It was established that the addition of K and Co significantly altered the physical-chemical properties, activity and selectivity of sulfide catalysts. The addition of K decreased the catalytic activity (i.e., over KMoS2/C and KCoMoS2/C) relative to the reference MoS2/C and CoMoS2/C samples. The incorporation of a promoter atom, Co, and an alkali metal, K, inhibited ethanol dehydration (into ethene) and intermolecular dehydration (into diethyl ether). K incorporation led to the formation of active sites for higher alcohol synthesis (HAS) and other oxygenates, namely (aldol-) condensation and coupling processes, and increased the ratio of liquids to hydrocarbons. Ethanol was transformed into ethyl acetate, ethyl acetoacetate, acetaldehyde, butonal-1, propanol-1, and short-chain hydrocarbons. The acidity of the catalysts did not have a direct influence on conversion. The obtained results led us to conclude that product yields are highly dependent on the active phase composition, with ethyl acetate being the most preferred product.

Keywords

• Ethanol dehydrogenation
• MoS2 catalysts
• Promoter atom
• Activated carbon
• Alkali metal
• Ethyl acetate