Syngas derived mixed olefin oligomerization: A pathway towards sustainable aviation fuel

Near term decarbonization of aviation sector requires the development of low-risk technologies that are already tied to existing industrial process and feedstock, thereby, enhances the potential for successful commercialization. Utilizing syngas as feedstock is appealing due to the existing infrastructure for its production and utilization in petrochemical industry. Although syngas predominantly obtained from coal, it can be produced via gasification from any ecologically disadvantages feedstocks such as municipal solid waste (MSW) and residual biomass that offers significant reduction in carbon footprint.^{1, 2} Although, various syngas-based technologies are available to produce jet range products, they are suffered by either lower selectivity to desired products or requirement of significant downstream separation. On the other hand, conversion of syngas to methanol followed by methanol to olefins (MTO) are already commercialized with high process yield (99% and 92% respectively). Thus, developing single step oligomerization process utilizing the olefin feedstock generated by MTO process is critical to develop end-to-end commercial pathway for producing SAF from syngas.
Oligomerization of either C₂ (ethylene) or C₃₊ (propylene, butene, pentene) olefins over heterogeneous catalysts are demonstrated in literature. However, there is significant technological gap exists for the co-oligomerization of C₂ and C₃₊ olefins. The primary challenge lies in the difference in activity in reactivity and corresponding oligomerization pathways between C₂ and C₃₊ olefins. Current C₂ and C₃₊ based industrial processes use metal and acid catalyzed pathways respectively to achieve oligomerization. Herein we developed a catalyst system that integrates both these chemistries and efficiently co-oligomerize C₂ and different C₃₊ olefins. Tuning the different process parameters along with the catalyst composition allowed us to obtain >90% conversion of both C₂ and C₃₊ olefins and ~80% selectivity to jet range hydrocarbons. The efficiency of this process has also been demonstrated using olefin feedstock with different composition further suggests the technology developed herein could be adapted to various upstream process that produces olefins. The catalyst developed herein also demonstrated ~150 h stability on time on stream without any deactivation.