Effect of Rh promoter on MWCNT-supported alkali-modified MoS 2 catalysts for higher alcohols synthesis from CO hydrogenation

Abstract

The promotional effects of Rh (0 to 2 wt%) on Mo-K/MWCNT catalysts for higher alcohol synthesis from synthesis gas (molar ratio of H 2 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 MoS 2 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 H 2 and CO is equal to 1) using gas hourly space velocity (GHSV) of 3.6 m 3 (STP)/h/(kg of catalyst) are determined as 330 °C and 9.65 MPa (1400 psig).