EFFECTS OF PARTICLE SIZE ON THE CATALYTIC PERFORMANCE OF MWCNTS SUPPORTED ALKALIZED MoS2 CATALYSTS PROMOTED BY Ni AND Co IN HIGHER ALCOHOLS SYNTHESIS

摘要

A series of nano-sized alkalized MoS2 catalysts promoted by Ni and Co supported on multi-walled carbon nanotubes (MWCNTs) were prepared via the reverse microemulsion technique with water to surfactant (W/S) molar ratios (mol(water) . mol(surfactant)(-1)) of 1-12. All prepared catalysts were extensively characterized by ICP, BET, CO chemisorption, XRD, TPR, and TEM techniques. They were assessed in a fixed-bed micro-reactor to find their performance in higher alcohol synthesis from syngas. The results were compared with those of the catalyst prepared by the incipient wetness impregnation method with similar elemental composition. The results showed the relationship of catalyst physicochemical properties and performances to preparation method and average metal particle sizes. Calculated average particle sizes for prepared catalysts via microemulsion showed a decreasing trend with a decrease in W/S ratio. It decreased from 17.4 to 5.26 nm for W/S ratios of 12 to 1, respectively. Similarly, the average particle size for prepared catalysts with the impregnation method was 18.78 nm. The nano-catalyst prepared via microemulsion with W/S of 1 showed the best performance for CO conversion and higher alcohol selectivity of 66.83 and 37.76, respectively. It was concluded that decreased particle sizes increased the active surface area of the Ni and Co promoted alkalized MoS2/MWCNTs catalysts and increased the fraction of metal particles located inside the CNTs, which in turn improved the catalyst performance.