Boot and his colleagues discussed the potential role of cyclic oxygenates in a 2008 paper published in the ACS journal Energy & Fuels. Boot and his colleagues proposed that low cetane number (CN) oxygenates—specifically cyclohexanone—should hold an advantage over their high CN counterparts via enhanced mixing as a result of both the extended ignition delay and longer FLOL (flame lift-off length).

Delaying the start of combustion, and giving the mixture of air and diesel fuel more time to mix thoroughly results in a cleaner combustion process. In addition, this fuel meets the planned EU standard which specifies that fuels must have 10% biofuel content in 2020.

As well as CyclOx, the university’s wood waste—such as pallets and wood packaging—will also produce other fuels, including ethanol. This will be offered at the university pump in a 10:90 mixture with gasoline.

In the first phase of the project the university will install fuel pumps, in 2012. At this filling station the diesel/CyclOx mixture will initially be available for a selected test group. In exchange for free fuel these users will contribute to the research project into the short- and long-term effects of using this fuel. In this phase the CyclOx will still be produced by an external party from mineral oil.

In their 2008 paper, Boot et al. noted that:

Cyclic paraffins are the most abundant (30-60 wt %) chemical compounds in crude oil. Rings with 6 carbon atoms (e.g., cyclohexane) are the most dominant species by far. Partial oxidation of cyclohexane to X1 is quite straightforward, which might explain why cyclohexanone (X1) could be purchased at less than a fourth of the price of TP and DB. What is more, distillates such as diesel, jet fuel, and heating oil, contain at least about 20 vol %, generally from about 20 to about 40 vol %, of six-membered cyclic paraffins. In other words, an economically viable feedstock for X1 is available at any neighborhood gas station. Even on-site and/or on-board refining is within the realm of possibilities.

Even more ambitious is the production of cyclic oxygenates (e.g., X1) from a biological feedstock, more specifically, from lignocellulosic biomass (also known as plant waste/residue). Principal components of such biomass include cellulose (35-50%), hemicellulose (25-30%), and lignin (15-30%)...all of which are five- and six-membered cyclic oxygenates. Unfortunately, these compounds are large polymers with molecular weights 2-4 orders of magnitude higher than conventional fuels. The production of liquid cyclic oxygenates from such heavy molecules is not straightforward...The design of a commercially viable production process of these species is a current subject of investigation.

—Boot et al. (2008)

At the same time researchers at TU/e in the group led by prof. Emiel Hensen MSc PhD (chair of Inorganic Materials Chemistry) are working on a demonstration reactor to convert wood waste. The plant is scheduled to be operational by mid-2015, supplying all TU/e’s generating sets and vehicles. The production output is expected to exceed the fuel needs of the university itself, so TU/e staff will later also be able to fill up their cars at the pump.

Project leader Boot expects fuel from the TU/e pump to be no more expensive than at other filling stations because of the use of wood waste. This waste currently has a negative value as the university has to pay for its disposal. Using this wood waste will therefore reduce the price of the final fuels.

The university intends with this project to show that it is possible for organizations to produce environment-friendly fuels themselves at a competitive cost.

I hope other universities and organizations will follow our example at TU/e. It’s also high time for industry to become enthusiastic about this pilot project. But we can’t expect industry to embrace our technology if we don’t first do the same ourselves.

—Michael Boot

Resources

• Michael Boot, Peter Frijters, Carlo Luijten, Bart Somers, Rik Baert, Arjan Donkerbroek, Robert J. H. Klein-Douwel, and Nico Dam (2008) Cyclic Oxygenates: A New Class of Second-Generation Biofuels for Diesel Engines? ASAP Energy Fuels, doi: 10.1021/ef8003637