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

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Hybrid catalysts that contain Zn−Pd-based cocatalyst show a higher and more positive sensitivity to ethanol than catalysts that contain supported Ni−Ru cocatalyst. In fact, with the former catalysts, the use of “gas oil−ethanol” blends significantly increases the product yields of light olefins and particularly ethylene. This appears to be actually a good approach for the partial replacement of petroleum feedstocks by bioderived chemicals (particularly, bioethanol). Another advantage of the CSC process is that it can make use of simply concentrated ethanol in aqueous solution as obtained by enzymatic conversion of biomass. This is maybe the first example of the beneficial effect of bioethanol on the performance of the CSC catalysts, suggesting that the integration of a small “biorefinery” to a petrochemical production plant is now possible. On the other hand, over our hybrid catalysts methanol used as coreactant behaves very differently from ethanol. In fact, while ethanol undergoes predominantly dehydration into ethylene, methanol predominantly intervenes directly in the hydrocarbon pool, keeping the product propylene-to-ethylene ratio almost constant and higher than 1.5.

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