(5a) Hydrocarbons from Biogas Via Biogas Reforming, Syngas Cleaning and Catalytic Conversion

This research work focused on taking advantage of biogas as a cleaner, sustainable and renewable feedstock to produce liquid hydrocarbons. In this approach, biogas is first reformed to high quality synthesis gas (H₂ + CO) followed by Fischer-Tropsch synthesis (FTS). The Sustainable Energy Research Center (SERC) at Mississippi State University has developed and tested a continuous process over a pilot plant system to demonstrate the technology of biomass to liquid (BTL) fuels. The process includes biomass gasification, syngas conditioning and cleaning, and FTS steps. Currently, the typical gaseous product components from the gasifier are 20% H₂, 19% CO, 12% CO₂, and 47% N₂ if using wood chips as the feedstock. The N₂ and CO₂ contents are too high, the total syngas (H₂ + CO) content is only about 40%, and H₂/CO ratio of the bio-syngas is less than 1. The biomass-derived product gas is not ideal for the hydrocarbon synthesis. Exceptional product gas is produced from biogas (Table 1), it contains high concentrated syngas (CO+ H₂ > 90%), low impurities and CO₂, as well as N₂,H₂/CO ratio is between 1 and 2 which makes it perfect production of liquid hydrocarbon by FTS. The liquid products generated by FTS can be readily upgraded to transportation fuels since they are primarily composed of hydrocarbons initially.

Table 1 Product gas composition for simultaneous dry and partial oxidation (using air) of biogas.