Influence of feed components on the activity and stability of cobalt molybdenum alumina metathesis catalyst

Alkene metathesis plays a vital role industrially in the upgrading of low value alkenes to higher value alkenes such as linear internal alkenes in the C-10-C-18 range. These in turn find application as feedstock for manufacturing of surfactants and detergents. Industrial alkene cuts contain component(s) that might be detrimental to the catalyst active sites during the metathesis reaction leading to catalyst deactivation. The focus of this study was to investigate the effect of some of the components present in typical low value feed streams on the activity and stability of a CoO/MoO3/Al2O3 catalyst. The results indicated that the feed composition does have a major influence on the metathesis reactivity of the catalyst. Pure 1-octene (98%), which was used as a reference feed was spiked with various components that had a concentration of 100 ppm. Results revealed a trend in terms of the severity of the component that deactivated the catalyst to be water > methylcyclopentadiene dimer > methylcyclopentane > toluene > 2-pentanone > 2-methyl-1,5-hexadiene > 2-methyl-1-hexene > butanol. A study was also undertaken to examine whether the component (methylcyclopentadiene dimer as an example) that deactivates the catalyst is a temporary or permanent poison. Results showed that methylcyclopentadiene dimer is a temporary poison. The carbonaceous deposits (oligomers) formed during the reaction seem to be the primary cause of catalyst deactivation. However, the catalyst deactivation mechanism in the presence of water in I-octene feed is mostly linked to the molecular structural change of the catalyst rather than accumulation of carbonaceous deposits on the surface of the catalyst. (C) 2004 Elsevier B.V. All rights reserved.