A process for converting alcohol from industrial waste gases into jet or diesel fuel is being scaled up at the US Department of Energy.
Two key technologies power the energy-efficient fuel production units, with a new catalyst and microchannel reactors improving efficiency and costs.
A one-step chemical conversion streamlines what is currently a multi-step process. The new PNNL-patented catalyst directly converts biofuel (ethanol) into a versatile ‘platform’ chemical called n-butene. A microchannel reactor design further reduces costs and provides a scalable modular processing system.
The new process would provide a more efficient route for converting renewable and waste-derived ethanol into useful chemicals. Currently, n-butene is produced from fossil raw materials using the energy-intensive cracking – or breaking down – of large molecules. The new technology reduces carbon dioxide emissions by using renewable or recycled carbon feedstocks. Using sustainably sourced n-butene as a starting point, existing processes can further refine the chemical for multiple commercial applications, including diesel and aviation fuels and industrial lubricants.
“Biomass is a challenging source of renewable energy due to its high cost. In addition, the scale of biomass is driving the need for smaller, distributed processing plants,” said Vanessa Dagle, co-principal investigator of the first research study, published in the journal ACS Catalysis.
“We have reduced the complexity of the process and improved efficiency, while at the same time reducing the cost of capital. Once modular, scaled processing has been demonstrated, this approach will provide a realistic option for localized, distributed energy production.”
In a leap towards commercialization, PNNL is partnering with longtime employees at Oregon State University to integrate the proprietary chemical conversion process into microchannel reactors built using newly developed 3D printing technology. Also called additive manufacturing, 3D printing allows the research team to create a pleated honeycomb of mini-reactors that significantly increase the effective surface-to-volume ratio available for the reaction.
“The ability to use new multi-material additive manufacturing technologies to combine the production of microchannels with large surface area catalyst supports in a single process step has the potential to significantly reduce the cost of these reactors,” said OSU principal investigator Brian Paul. “We are excited to be partners with PNNL and LanzaTech in this endeavor.”
Robert Dagle, co-principal investigator of the study, added: “Due to recent advances in microchannel manufacturing methods and associated cost reductions, we believe the time is right to adapt this technology to new commercial bioconversion applications.”
The microchannel technology would make it possible to build commercial scale bioreactors near agricultural centers where most of the biomass is produced. One of the biggest barriers to using biomass as a fuel is the need to transport it over long distances to large, centralized production facilities.
“The modular design reduces the amount of time and risk it takes to deploy a reactor,” says Robert Dagle. “Modules can be added over time as demand grows. We call this scaling up by numbering.”
The fourth commercial-scale test reactor will be produced by 3D printing using methods developed in conjunction with OSU and will be operated at PNNL’s Richland, Wash. campus.
Once the test reactor is complete, PNNL’s commercial partner, LanzaTech, will supply ethanol to feed the process. LanzaTech’s proprietary process converts carbon-rich waste and residues produced by industries such as steelmaking, oil refining and chemical manufacturing, as well as gases generated by gasification of forest and agricultural residues and municipal waste, into ethanol.
The test reactor will consume ethanol equivalent to a maximum of half a dry tonne of biomass per day. LanzaTech has already scaled up the first generation PNNL technology for the production of jet fuel from ethanol and established a new company, LanzaJet, to commercialize LanzaJet™ Alcohol-to-Jet. The current project represents the next step in streamlining that process and providing additional product streams from n-butene.
“PNNL has been a strong partner in the development of ethanol-to-jet technology using LanzaTech’s spin-off company, LanzaJet, across multiple plants under development,” said Jennifer Holmgren, CEO of LanzaTech. “Ethanol can come from various sustainable sources and as such is an increasingly important raw material for sustainable aviation fuel. This project holds great promise for alternative reactor technology that could benefit this important path to decarbonisation of the aviation sector.”
Since their early experiments, the team has continued to perfect the process. When ethanol is passed over a solid silver-zirconia-based catalyst supported on a silica, it carries out the essential chemical reactions that convert ethanol to n-butene or, with some adjustments to the reaction conditions, butadiene.
More importantly, after long-term studies, the catalyst remains stable. In a follow-up study, the research team showed that if the catalyst loses activity, it can be regenerated through a simple procedure to remove coke — a hard, carbon-based coating that can build up over time. For scale-up, an even more efficient, updated catalyst formulation will be used.
“We discovered the concept for this catalyzed system that is highly active, selective and stable,” says Vanessa Dagle. “By adjusting pressure and other variables, we can also tune the system to generate butadiene, a building block for synthetic plastic or rubber, or an n-butene, which is suitable for making jet fuels or products such as synthetic lubricant. . Since our initial discovery, other research institutions have also begun to explore this new process.”