ZnO-ZrO2 coupling nitrogen-doped carbon nanotube bifunctional catalyst for co-production of diesel fuel and low carbon alcohol from syngas

Catalytic syngas conversion to liquid fuel is pivotal for biomass utilization, enhancing energy security, reducing carbon emissions and curbing reliance on petroleum imports. Herein, bifunctional catalysts comprising zinc-zirconium dioxide (ZnZrO2) dispersed on nitrogen-doped multi-walled carbon nanotubes (NCNT) (ZnZrO2/NCNT) were successfully designed, enabling the simultaneous production of both diesel fuels (C-9-C-16 hydrocarbon) and methanol through direct syngas conversion. Operating at 450 degrees C, 4.5 MPa, a gas hourly space velocity (GHSV) of 4800 mL h(-1)center dot g(cat)(-1), the ZnZrO2/NCNT catalyst, featuring 2.6% nitrogen doping, exhibited exceptional performance, achieving a 50.3% selectivity for C-9-C-16 hydrocarbons and a 26.4% selectivity for methanol, while maintaining a 52.5% single-pass CO conversion rate. The C9+ selectivity significantly surpasses the bottleneck predicted by the ASF distribution theory (C9+ selectivity <36%). This starkly contrasts that of ZnO/NCNT (1.7% C-9-C-16 and 6.3% methanol) and ZrO2/NCNT (32.5% C-9-C-16 and 25.4% methanol) catalysts. Moreover, the ZnZrO2/NCNT catalyst still retained C9+ 51.5% selectivity and 25% methanol selectivity after 100 h of continuous operation. The synergistic effects resulting from the amalgamation of highly active nanostructured units with a well-encapsulation structure efficiently hinder active component migration during catalysis. This significantly enhances both the catalyst's activity and stability. Furthermore, nitrogen introduction serves as a key electron donor to ZnZrO2, thereby catalyzing the activation of CO dissociation. This activation step emerges as a pivotal factor crucial for enhancing selectivity in liquid fuel production.