Novel single pass biogas-to-diesel process using a Fischer–Tropsch catalyst designed for high conversion

The decentralized production of low carbon fuels using the Fischer–Tropsch synthesis requires a less complex and more cost-effective process design. This can be achieved by operating the Fischer–Tropsch process in single pass mode (i.e., without recycle), which allows for omission of the air separation unit, CO2 removal step and the energy-intensive recompression. However, single pass mode necessitates operating the Fischer–Tropsch synthesis at a higher CO conversion than typically seen in industry (resulting in high H2O and low CO and H2 partial pressures). These harsh conditions cause a significant decrease in the C5+ yield as a consequence of the increase in the selectivity for the formation of CH4 and CO2. Modification of an industrial Pt–Co/Al2O3 catalyst with manganese resulted in increased fuel production of up to 14 C-% under high conversion conditions. Here, we present a technical analysis of a novel single pass biogas-to-diesel process that can operate off-grid in remote regions, focusing on counteracting the loss of yield under single pass operation by adjusting the Fischer–Tropsch conversion (XCO = 60–90%), catalyst characteristics (Pt–Co/Al2O3vs. Mn–Pt–Co/Al2O3) and refining configuration (with and without a hydrocracker). The optimal case, XCO = 80% using a Mn–Co/Al2O3 catalyst results in a production rate of 246 bbl per day of on-spec distillate from 400 kmol h−1 biogas together with the net power generation of 1.8 MW.