The power of plants

A new process for creating components for biofuels is paving the way for a new generation of green fuels.

A team for the University of Wisconsin-Madison have announced the first direct conversion of plant cellulose into gasoline components. This 'green gasoline' can be created from sustainable biomass sources like switch grass and poplar trees.

Professor James Dumesic and his team at UW-Madison have also announced an integrated process for creating chemical components of jet fuel using a green gasoline approach. While the group had previously demonstrated the production of jet-fuel components by combining separate catalytic steps, its current work shows that these steps can be integrated together and run sequentially, without complex separation and purification processes between reactors.

While it may be five to ten years before these green fuels arrive at the pump or power a jet, these breakthroughs have jumped significant hurdles to bringing biofuels to market.

'It is likely that the future consumer will not even know that they are putting biofuels into their car,' George Huber, University of Massachusetts Amherst Assistant Professor of Chemical engineering, says. 'Biofuels in the future will most likely be similar in chemical composition to gasoline and diesel fuel used today. The challenge for chemical engineers is to efficiently produce liquid fuels from biomass while fitting into the existing infrastructure today.'

For their new approach, the UMass researchers rapidly heated cellulose in the presence of solid catalysts, materials that speed up reactions without sacrificing themselves in the process, and then rapidly cooled the products to create a liquid that contains many of the compounds found in gasoline.

The entire process was completed in less than two minutes using relatively moderate amounts of heat. The compounds that formed in that single step, like naphthalene and toluene, make up one-fourth of the suite of chemicals found in gasoline. The liquid can be further treated to form the remaining fuel components or can be used as is for a highoctane gasoline blend.

'Green gasoline is an attractive alternative to bioethanol since it can be used in existing engines and does not incur the 30 per cent gas mileage penalty of ethanol-based flex fuel,' John Regalbuto, who directs the Catalysis and Biocatalysis Program at the National Science Foundation (NSF) and supported this research, says.

'In theory it requires much less energy to make than ethanol, giving it a smaller carbon footprint and making it cheaper to produce. making it from cellulose sources such as switchgrass or poplar trees grown as energy crops, or forest or agricultural residues such as wood chips or corn stover, solves the lifecycle greenhouse gas problem that has recently surfaced with corn ethanol and soy biodiesel,' Regalbuto adds.

Beyond academic laboratories, both small businesses and Fortune 500 petroleum refiners are pursuing green gasoline. Companies are designing ways to hybridize existing refineries to enable petroleum products including fuels, textiles, and plastics to be made from either crude oil or biomass and the military community has shown strong interest in making jet fuel and diesel from the same sources.

'Huber's new process for the direct conversion of cellulose to gasoline aromatics is at the leading edge of the new 'Green Gasoline' alternate energy paradigm that NSF, along with other federal agencies, is promoting,' Regalbuto says.

Not only is the method a compact way to treat a great deal of biomass in a short time, Regalbuto emphasised that the process, in principle, does not require any external energy. 'In fact, from the extra heat, you can generate electricity in addition to the biofuel,' he adds. 'There will not be just a small carbon footprint for the process; by recovering heat and generating electricity, there won't be any footprint.'

'We are currently working on understanding the chemistry of this process and designing new catalysts and reactors for this single step technique. This fundamental chemical understanding will allow us to design more efficient processes that will accelerate the commercialisation of green gasoline,' says Huber.

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