Microemulsion synthesis of Co nanoparticles supported on CNT: Effects of Nanoparticles Size on reducibility, activity and selectivity in FTS

摘要

The influence of cobalt particle size on catalyst performance in Fischer-Tropschsynthesis (FTS) has been investigated using inert carbon nanotube (CNT)-supported catalysts. The catalysts were produced by the core reverse micellereactions with cobalt particles of various sizes (3 to 10 nm). It has been shownthat particle size is proportional to the water-to-surfactant ratio (3 to 10) used forthe catalyst preparation. Very narrow particle size distributions have beenproduced by the microemulsion technique and at relatively high loading (Co 10wt %). Selectivity and activity were found to be dependant on cobalt particle size.The FTS rate increases from 0.36 to 0.44 gHC/gcat./h and the C5+ selectivityincreases from 89 to 92.5 wt% with increasing the average cobalt particle sizefrom 2-3 nm to 9-10nm, respectively. According to TEM analysis, small Coparticles (2-6nm) are mostly confined inside the CNTs where influence of itselectron deficiency in the inside surface has changed the commonly expectedcatalyst’s structure-sensitive results. Finally, the CNT-supported cobaltnanoparticles synthesized by the proposed microemulsion technique increasedthe CO conversion by 15% compared to those prepared by incipient wetnessimpregnation.