Synthesis of higher alcohols from synthesis gas over Co-promoted alkali-modified MoS 2 catalysts supported on MWCNTs

Abstract

A series of Co (0–6 wt%)-promoted 15 wt% Mo and 9 wt% K catalysts was prepared using multi-walled carbon nanotubes (MWCNTs) as support. These catalysts were extensively characterized in oxide and sulfide phases and tested for higher alcohol synthesis reaction from CO hydrogenation (molar ratio of H 2 to CO is equal to 1). The diffraction peaks that represent the characteristic K–Mo–S phase were observed in the X-ray diffraction (XRD) patterns of sulfided Co-promoted Mo-K/MWCNTs catalysts. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of adsorbed CO revealed that Co addition to Mo-K/MWCNTs catalyst not only increases the number of surface Mo sites, but also promotes the reducibility of Mo. The total alcohol space time yield (STY) reached a maximum at 0.207 g/(g of catalyst)/h on the catalyst promoted with 6 wt% Co, whereas the catalyst with 4.5 wt% Co exhibited selectivities of 14% and 23% towards ethyl alcohol and higher alcohols, respectively, at 320 °C and 8.27 MPa. The best conditions for producing higher alcohols from synthesis gas (mole ratio of H 2 and CO is equal to 1) using gas hourly space velocity of 3.6 m 3 (STP)/h/kg of catalyst are determined as 330 °C and 9.65 MPa.