James Dumesic and George Huber are now both at the University of Wisconsin-Madison leading a team of researchers demonstrating how C5 sugars derived from hemicellulose can be converted into a high-quality petroleum refinery feedstock via a four-step catalytic process. Go Badgers! What a team!
They’re not making crude oil as such, rather they’ve built up a substitute petroleum product consisting of normal, branched and cyclic alkanes up to 31 carbons in length and is similar in composition to feedstocks produced in a petroleum refinery today from crude oil. Of great interest is the process can be tuned to adjust the size of the liquid alkanes.
In the first step furfural – a highly promising feedstock for biofuel production – is produced from the acid-catalyzed dehydration of hemicellulose-derived sugar streams in a biphasic reactor. The second step is the aldol condensation of furfural with acetone in a THF solvent and using a NaOH catalyst to produce highly conjugated C13 compounds along with some oligomeric adducts formed through Michael addition reactions.
Next, the conjugated compounds are hydrogenated with a Ru/Al2O3 catalyst forming both the fully hydrogenated form of the C13 oligomers and also forming larger oligomers by Diels–Alder reactions. The extent of Diels–Alder reactions can be tuned by changing the temperature and feed concentration, thereby adjusting the distribution of liquid alkanes that can be produced.
In the last step, a bi-functional catalyst Pt/SiO2–Al2O3 is used for hydrodeoxygenation to produce the liquid alkanes or more specifically, fluid catalytic cracker cycle oil substitutes, having carbon numbers up to C31.
The result from a simple biorefinery model shows that about 55% of a furfural–acetone mixture (in a 10:3 weight ratio) can be converted into cycle oils while also producing other refinery products such as gasoline and natural gas.
The research was done using homogeneous catalysts, or catalysts of one chemistry and one reaction. The authors expect that new generations of solid heterogeneous (multiple chemistries and reactions) catalysts might more efficiently convert biomass resources into these targeted products. In the paper the team suggests new catalysts will likely be developed by understanding the fundamental chemical reactions, developing new synthesis techniques, using modern computational tools, and using in situ spectroscopy techniques.
It looks like they’re on their way as the last step in the report is a bi-catalyst.
The research is worthy news on more than one front. Dumesic and Huber are at the same university for one. They’ve launched into multiple reaction catalysts for two. They have lab product in hand for three. The process chemistry for building biofuels may well be very far ahead of the feedstock issues very soon.
There in lies the problem. Coming up with the sugar streams made from hemicellulose is still a major chemical, logistical and economic problem. Getting the farming, transport, precursor chemistry and treatment in a market situation is a huge task needing very attractive incentive for long terms.
The research is so new that no estimates of costs or operating expenses are known. Yet the basic nature of the work is very encouraging.
Two of the cleverest guys in biofuels are on the same campus. There is certainly more, much more, to come.