Effect of Rh promoter on MWCNT-supported alkali-modified MoS2 catalysts for higher alcohols synthesis from CO hydrogenation Original Research Article

The promotional effects of Rh (0 to 2 wt%) on Mo-K/MWCNT catalysts for higher alcohol synthesis from synthesis gas (molar ratio of H2 to Co is equal to 1) were examined. Diffraction peaks representing the characteristic K-Mo-S phase were observed in the X-ray diffraction (XRD) patterns of the sulfided form of the Rh-promoted Mo-K/MWCNT catalysts. When 1 wt% Rh was introduced on the multi-walled carbon nanotube (MWCNT)-supported 15 wt% Mo and 9 wt% K catalysts, the reduction temperature of Mo(VI) to Mo(IV) was significantly decreased to 394 °C. Metal dispersions were increased from 30% to 42%, with an increase in Rh content from 0 to 2 wt%. The existence of promoted and un-promoted MoS2 sites was confirmed by a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study of adsorbed CO over sulfided catalysts. The maximum total alcohol yield of 0.211 g/(g of cat./h), ethanol selectivity of 16%, and higher alcohols selectivity of 25% were observed on the catalyst with 1.5 wt% Rh at 320 °C and 8.3 MPa. The best conditions for producing higher alcohols from synthesis gas (mole ratio of H2 and CO is equal to 1) using gas hourly space velocity (GHSV) of 3.6 m3 (STP)/h/(kg of catalyst) are determined as 330 °C and 9.65 MPa (1400 psig).