The supported Ni co-catalyst surface of the thermocatalytic cracking (TCC) hybrid catalyst produces very active hydrogen species. Such species, once transferred (spilt-over) onto the surface of the main catalyst component (cracking sites), interact with the adsorbed reaction intermediates, resulting in a decreased formation of coke precursors (polynuclear aromatics) and the dearomatization/ring-opening of some heavy compounds of the feed. Simultaneously, there is a significant increase in the product yields of light olefins, particularly ethylene and propylene. Analysis of reaction products after 10 h of continuous reaction shows the very significant effects of these co-catalysts on heavy feedstocks such as vacuum gas oils, although the amounts of these (spilt-over) hydrogen species are very small, in comparison to the molecular hydrogen produced by the cracking reactions.

No abstract

The addition of some methanol to petroleum light naphtha used as feed in the Thermal Catalytic/Steam Cracking(TCSC) process significantly increases the product yield of C 2 -C 4 olefins, particularly that of ethylene ? propylene. However, over 20-25 wt% of methanol content in the naphtha feed, the beneficial effect is attenuated. At relatively high values of contact time, the (Zn-Pd) co-catalyst of the hybrid catalyst exerts noticeably its coke cleaning effect on the zeolite acid sites, particularly when methanol is present in the feed. The product weight ratio (propylene/ethylene) is not affected by such ''moderate'' addition of methanol and remains higher than 1.3.

Hybrid catalysts developed for the thermocatalytic cracking of liquid hydrocarbons were found to be capable of cracking C 4 ? olefins into light olefins with very high combined yields of product ethylene and propylene (more than 60 wt%) and C 2 -C 4 olefins (more than 80 wt%) at 610-640°C, and also with a propylene/ethylene weight ratio being much higher than 2.4. The olefins tested were heavier than butenes such as 1-hexene, C 10 ? linear alphaolefins (LAO) or a mixture of LAO. The hydrogen spillover effect promoted by the Ni bearing co-catalyst, contributed to significantly enhancing the product yield of light olefins and the on-stream stability of the hybrid catalyst.Keywords TCC-type hybrid catalysts Á Cracking of heavy olefins Á Effect of hydrogen spillover on product yields and coke deposition