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Researchers Report Advances in Direct Production of Liquid Hydrocarbon Fuels from Biomass

7 April 2008

Huber3
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
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.

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April 7, 2008 in Biomass, Fuels | Permalink | Comments (14) | TrackBack (0)

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Comments

All sorts of synthetic fuel production processes coming out of the woodwork. Which one will win? Will any of them even be able to compete, for that matter?

Is the "for jet fuel" angle a boondoggle to get DARPA funds, or something? The highest value liquid fuel is put to is for jet engines, and the need for predictable performance the greatest, so that would be the last thing that would be replaced by biosources. If great research comes out of it, that's surely a better use of defense budget than Iraq, but I'm just wondering if anyone else can check my thinking on that.

Transparent biofuel compounds, i.e. those that do not affect the properties of the resulting fuel blend, are preferable to alcohols and fatty acid methyl esters, respectively.

However, requiring high heating rates and high catalyst-to-feedstock ratios represents something of a barrier to scaling this up. Note that the Mobil methanol to gasoline (MTG) process that was implemented in New Zealand also relies on zeolites; pore coking was reported to be a problem there.

As for the catalytic HMF processing, that will be useful if the fructose feedstock can be separated from the glucose after enzymatic splitting of cellulose. Glucose can be converted to alcohols fairly easily.

@ Healthy Breeze -

the focus on kerosene may be due to educts of the HMF processing. Purity will be an issue, but the Air Force is more likely to test non-conventional fuels before civilian operators do. At least, that was the case with GTL.

Well, think about it.

Everything besides aircraft/military and cargo-ships can go electric.

So obviously the focus is going to be on Kerosene, and Bunker Fuel.

GreyFlcn,

I think within twenty years the average personal automobile will be either battery electric (BEV) or plug-in hybrid electric (PHEV) types, thanks to the switch to supercapacitor battery packs made with nanotechnology. We're talking potentially one liter/100 kilometer fuel efficiency! :-)

Bleeh ! Aromatic compounds ...

Ok, it's a simplified version of the Mobil MTG process with the methanol step removed. Same ZSM-5 catalyst, by the way.

http://chemelab.ucsd.edu/methanol/introduction/introduction.html

I'd be curious to see what's the catalyst lifetime is. Even in the relatively controlled MTG process, it has to be regenerated very often because of cocking. So, with a raw pyrolysis gas, in the presence of fine fly-ashes from actual mineral-bearing lignocellulose (not lab cellulose aka clean toilet paper), it's going to be fun...

In any case, MTG gasoline is disgusting stuff. It sure burns, it even has high octane but it's full of aromatic compounds and that's a big problem: toxic, carcinogenic with very poor biodegradability, very long persistence in the environment in case of spills. An ecological nightmare. The agenda is to remove that stuff from retail gasoline, not to add more to it...

Everything besides aircraft/military and cargo-ships can go electric.

I wonder if it could be at all practical to fuel ships using liquid sodium, oxidized in some kind of fuel cell.

I agree that we would like to keep the best properties of a fuel and get rid of the bad ones. We do not need to duplicate problems that we are trying to get rid of.

Yes it is weird that Choren FT process (Sundiesel) boasts that it avoids aromatics while this new process promotes them. I take it that they are nowhere near a pilot plant yet.

Yes it is weird that Choren FT process (Sundiesel) boasts that it avoids aromatics while this new process promotes them.

Don't aromatics promote soot formation in diesel engines, but raise the octane rating of gasoline for spark ignition engines?

Aromatics have high antiknock ratings, but are notorious smog-formers. We must remember that one reason for using ethanol, is to provide combined oxygen to reduce smog formation as well as improve antiknock properties.

Paul Dietz has it right. Aromatics have very high octane numbers (IIRC typically 120-130) and are necessary to bring the gasoline blend octane number up. They also have low cetane numbers and make for low-quality additives to diesel (they do have some lubricative properties which were useful a decade or two ago.) So Choren avoids aromatics as it makes diesel -- it is easier for them to get alkanes anyway, and xTL diesel can have CNs of 70 or more; "green gasoline" (whatever the hell that is) OTOH needs aromatics.

These two studies are simply "proof of concept." Nowhere near a pilot plant. The processes will be tweaked over the next several years to optimize output products to whatever environmental regime is in place by that time.

At the rate the US Congress is outlawing energy sources, biofuels may be outlawed by then.

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