Synthesis of higher alcohols from synthesis gas over Co-promoted alkali-modified MoS2 catalysts supported on MWCNTs

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 H2 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 H2 and CO is equal to 1) using gas hourly space velocity of 3.6 m3 (STP)/h/kg of catalyst are determined as 330 °C and 9.65 MPa.

Figure optionsDownload high-quality image (24 K)Download as PowerPoint slideResearch highlights▶ Mo and Co, metal species were uniformly distributed inside and outside of the tubes, with particle sizes in the range of 3–4 nm. ▶ Metal dispersion of 39% was observed on the MWCNT-supported 15 wt% Mo and 9 wt% K catalysts that are promoted with 4.5 wt% Co. ▶ The molar ratio of higher alcohols to methanol increased significantly with increases in temperature and pressure over the investigate range of 300–340 °C and 5.52–9.65 MPa, respectively.