Fluid catalytic cracking: Processing opportunities for Fischer-Tropsch waxes and vegetable oils to produce transportation fuels and light olefins

摘要

Fluid catalytic cracking (FCC) of Fischer-Tropsch (FT) waxes and vegetable oils could be an attractive option to produce transportation fuels and light olefins. For FT waxes, the catalytic cracking using commercial FCC catalysts revealed that a particular product slate (gasoline, diesel or light olefins) with high selectivity can be obtained by selecting an appropriate catalyst and operating conditions. FT wax is an outstanding feedstock in providing a high-value petrochemical feedstock, propene, with yields about 25 wt.% by employing pure ZSM-5 or ZSM-5/FCC catalyst (Y-zeolite-based) mixture. Similar amounts of butenes are also obtained. For the catalytic cracking of vegetable oils, the product distribution primarily depends on the degree of unsaturation (double bonds) of vegetable oils. For gasoline with high selectivity, saturated vegetable oils are more preferable. Irrespective of the degree of unsaturation, the aromatic content of the product fractions is relatively high compared to those from the conventional FCC feedstocks (VGO). Further modification of a FCC catalyst with a suitable metal (nickel) along with co-feeding H2 tremendously increases the gasoline and light olefins yields from a vegetable oil. Thus, development of a novel catalyst and/or tuning catalyst characteristics is still a promising research area to focus onto improve the cracking performance of vegetable oils. The cracking data of FT waxes/vegetable oils with VGO showed that co-processing of renewable feedstocks with the conventional FCC feedstocks is promising and no significant interactions exist between conventional and renewable feedstocks. Consequently, the prediction of the cracking performance at different blend ratios is straightforward.