Upgrading of Fischer-Tropsch Waxes by Fluid Catalytic Cracking

Synthesis gas originating from alternative feedstocks such as biomass, coal, or natural gas can become an important source of hydrocarbon-based automotive fuels in the future. Fischer-Tropsch synthesis (FTS) affords these hydrocarbons, but upgrading of the primary FTS products is unavoidable. One option is to use the fluid catalytic cracking (FCC) process to convert FTS waxes into a wide range of products. To investigate the impact of FTS wax addition to a conventional FCC feedstock on product yields and properties, microactivity test (MAT) experiments were performed. The tests were performed at 803 K and the catalyst to feed ratio (C/F) was varied in the range 2-4 m/m. The feed contained 0-100% of FTS wax. The addition of FTS wax resulted in increased conversion and yield of the middle distillate fraction (light cycle oil, LCO) and decreased yield of coke. Owing to the increased conversion, higher yields of propylene were obtained by catalytic cracking of feedstocks containing FTS wax. The detailed GC analysis of the products indicated enhanced properties of LCO due to the lowered content of aromatics.