Production of Liquid Biofuels in a Fluid Catalytic Cracking Pilot-Plant Unit Using Waxes Produced from a Biomass-to-Liquid (BTL) Process

The production of synthetic transportation fuels from lignocellulosic biomass feedstocks through a biomass-to-liquid (BTL) process based on Fischer-Tropsch (F-T) synthesis is today of increasingly importance. Depending on the operating conditions of the F-T process, heavy waxy hydrocarbons could be produced (waxes) with almost zero aromatics and sulfur. The purpose of this study is the investigation of a catalytic cracking process for the upgrading of these BTL waxes in order to produce high-quality biofuels. In this work, a F-T Wax with hydrocarbons up to C(40) was used, while the fluid catalytic cracking (FCC) experiments were carried out in an FCC pilot-plant unit operating in a full circulation mode with continuous catalyst regeneration. Three different catalysts, cofeeding options, and various operating conditions were investigated in the pilot plant. Our results showed that the F-T Wax is very crackable and conversions in the range of 70-90 wt % (on the feed) can be achieved with all catalysts tested. Catalyst type and cracking temperature also play an important role in improving the selectivity of specific FCC products. The process gives high gasoline yields with very low aromatics, low light cycle oil yields, and very low coke yields. The use of a ZSM-5 catalyst offers also significant advantages for the production of light olefins, while this catalyst strongly influences the gasoline composition.