|Huber’s catalytic fast pyrolysis process yields aromatic components for gasoline. Click to enlarge.|
Researchers at the University of Massachusetts-Amherst reported the first production of high-quality aromatic fuel additives for gasoline directly from solid biomass feedstocks by catalytic fast pyrolysis in a single catalytic reactor at short residence times. The work by Professor George Huber and graduate students Torren Carlson and Tushar Vispute is the cover article in the 7 April issue of Chemistry & Sustainability, Energy & Materials (ChemSusChem).
In the same issue, Professor James Dumesic and colleagues from the University of Wisconsin-Madison announced an integrated, four-step process for creating higher weight alkanes—such as C8-C15 for jet fuel applications—directly from biomass. While Prof. Dumesic’s group had previously demonstrated the production of these liquid alkanes components using separate steps, their current work shows that the steps can be integrated and run sequentially, without complex separation and purification processes between reactors.
It is likely that the future consumer will not even know that they are putting biofuels into their car. 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.—George Huber
For their new approach, the UMass researchers rapidly pyrolized biomass in the presence of a zeolite (ZSM-5) catalyst. High heating rates and catalyst-to-feed ratios are needed to ensure that pyrolized biomass compounds enter the pores of the ZSM-5 catalyst and that thermal decomposition is avoided.
Product selectivity is a function of the active site and pore structure of the catalyst. They then rapidly cooled the products to create a liquid that contains many of the compounds found in gasoline.
The entire process was completed in under 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 high octane gasoline blend.
Green gasoline is an attractive alternative to bioethanol since it can be used in existing engines and does not incur the 30 percent gas mileage penalty of ethanol-based flex fuel. 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.—John Regalbuto, director of the Catalysis and Biocatalysis Program at NSF
Huber’s process has the potential for zeroing out its carbon footprint by recovering heat from the process and generating electricity, according to Regalbuto.
|Dumesic’s integrated process delivers higher-weight alkanes suitable for use as a jet fuel. Click to enlarge.|
Dumesic—co-founder of Virent, a company which is commercializing the aqueous phase reforming technology he developed—and his researchers have been working for some time on a process to make a chemical intermediate called HMF (hydroxymethylfurfural) from fructose from biomass. HMF can be converted into plastics or hydrocarbon fuels.
Here, we show that the yields of various processing steps can be improved through choice of the proper catalyst and operation and specific reaction conditions. With these improvements, we demonstrate that the overall carbon yield from fructose to C7-C15 alkanes is 58-69% for HMF-acetone systems, while the overall carbon yield from various furfurals to C7-C15 alkanes is 79-94%.—Dumesic et. al.
Dumesic and his team produced alkanes of higher targeted molecular weight by first converting sugars into furfural compounds through dehydration reactions and by producing ketones and aldehydes through carbonyl formation reactions.
These oxygenated intermediates form carbon-carbon bonds. Subsequent dehydration reactions lead to the removal of oxygen by production of water, and reduction reactions lead to the hydrogenation of the double bonds formed by dehydration. Hydrogen required for the reactions is produced from the sugar and water by evolution of CO2.
Torren R. Carlson, Tushar P. Vispute, George W. Huber; Green Gasoline by Catalytic Fast Pyrolysis of Solid Biomass Derived Compounds; ChemSusChem DOI: 10.1002/cssc.200800018
Ryan M. West, Zhen Y. Liu, Maximilian Peter, James A. Dumesic; Liquid Alkanes with Targeted Molecular Weights from Biomass-Derived Carbohydrates; ChemSusChem DOI: 10.1002/cssc.200800001
NSF (2008) Breaking the Chemical and Engineering Barriers to Lignocellulosic Biofuels: Next Generation Hydrocarbon Biorefineries. Ed. George W. Huber, University of Massachusetts Amherst. National Science Foundation. Chemical, Bioengineering, Environmental, and Transport Systems Division. Washington DC