Higher Alcohol Synthesis Using K-Doped CoRhMoS₂/MWCNT Catalysts: Influence of Pelletization, Particle Size and Incorporation of Binders

In this study, alkalinized MWCNT supported MoS₂ catalysts have been doubly-promoted with Co and Rh. Catalysts were prepared by the conventional co-impregnation method and stabilized under argon atmosphere. Characterization of the oxidic samples by BET revealed that the mesoporosity of the pristine MWCNT support was not compromised after loading a combined total of 30 wt% metals (9 wt% K, 4.5 wt% Co, 1.5 wt% Rh, and 15 wt% Mo) on the support; however, a significant decrease in specific surface area was observed. Broad angle XRD analysis confirmed the homogenous dispersion of catalyst metals on the support. Two catalyst grain sizes were first investigated to elucidate the effect of particle size: a finely ground powder (88 μm) and a pelletized form (1,780 μm). Despite the total alcohol yield of 0.261 g/(g_cat h) observed by conducting higher alcohol synthesis reaction at T = 330 °C, P = 8.3 MPa, H₂/CO = 1.25, and GHSV = 3.6 m _STP ³ /(kg_cat h) for the fine powdered sample, the relatively higher pressure drop could be minimized by using the pelletized form of the catalyst. Finally, a systematic study of variety of selected binders was conducted to gain insight of catalyst’s applicability for industrial purposes. Three selected binders namely: bentonite clay, coal tar, and humic acid were thus investigated; taking into consideration significant factors such as melting point and binder requirement per catalyst support. The CO conversions evaluated for the two binder-free catalysts (88 and 1,700 μm) showed that the catalyst with fine particle sizes (88 μm) performed better than that in the pelletized form (binder-free, 1,700 μm); yielding a maximum ethanol selectivity of 38.5 % at steady-state reaction conditions.