China Lake Researchers Develop Potential Biobutanol Pathway for Synthetic Jet Fuel
29 July 2008
Researchers at the Naval Air Warfare Center Weapons Division (NAWCWD) at China Lake, California have developed an efficient batch catalysis process for the conversion of 1-butene (C4H8)—easily derived from butanol (C4H10O)—to a new class of potential synthetic jet fuel blends, with a specific focus on the requirements for the Navy’s JP-5. JP-5 has a significantly higher flash point (60°C) in comparison to the Air Force JP-8 and commercial jet fuel (~38°C).
The resulting product developed by the team of Michael Wright, Benjamin Harvey, and Roxanne Quintana is 100% iso-paraffinic, meets flash point and cold-flow requirements, and has a calculated power density (per volume) higher than similar fuels made by the GTL Fischer-Tropsch process. They report on their work in an ASAP paper published online 29 July 2008 in the journal Energy & Fuels.
The ultimate goal of our research program here at China Lake is to create a full-performance JP-5/tactical biojet fuel that can be derived from a fully renewable and sustainable source of reduced carbon. Given recent advances in the conversion of starch and cellulosic biomass to biobutanol, we have initiated a program to explore using the C4 alcohol as a pivotal and versatile starting point for the creation of new fuels. Because both butyl ether and 1-butene can be easily derived from 1-butanol, we are investigating use of these chemicals as precursors to biojet fuels that will meet the required energy content and key performance specifications of JP-5 jet fuel. In this paper, we present methods for converting 1-butene into a variety of useful saturated hydrocarbon fuels using a highly efficient batch-catalysis process.
The new approach affords a product that is composed of 100% iso-paraffins, retains good fuel density, possesses attractive cold-flow properties, and, critical to Naval applications, can be easily tailored to have a high flash point.—Wright et al. (2008)
The process entailed condensing the 1-butene onto CaH2 and then transferring it over the course of 3 hours to a chilled (dry ice bath) pressure reaction vessel containing activated catalyst—bis(cyclopentadienyl)zirconium dichloride in the presence of methylaluminoxane (MAO). The reaction vessel is sealed and allowed to react with stirring at ambient temperature for 16 hours. The result is the consumption of the 1-butene and the production of dimers and oligomers.
The produced product makes incremental jumps in 4-carbon units—i.e., C8 (dimer), C12, C16, C20, C24, C28, and C32. The dimer—about 25 wt.% of the product mixture—is removed for separate conversion to C16 compounds for reblending with the end product. Hydrogenation (~0.08 wt% PtO2/H2, 2 psig) of the remaining oligomers yields a fuel that has a flash point of 59°C, viscosity of 103 cSt, and a lubricity value of 0.45 mm. By changing the catalyst preparation, they produced a significant change in oligomer distribution, while still maintaining full conversion of 1-butene to oligomers.
In summary, we have developed a highly efficient batch catalysis methodology for conversion of 1-butene to a new class of potential jet fuel blends. By tuning the catalyst and then using the dimer produced, we can bring the carbon use to ~95% or greater. This latter point will be particularly important in the future, where the source of raw materials (i.e., biomass/biofeedstock) is limited. Also noteworthy, the batch catalysis approach herein requires a minimal input of energy and hydrogen to make fuels that possess useful flash points, coldflow properties, and solution density/energy content. This new process affords a saturated hydrocarbon fuel that has a high solution density and thus possesses a higher calculated power density (per volume) than similar fuels made by the GTL Fischer-Tropsch processes.—Wright et al. (2008)
Michael E. Wright, Benjamin G. Harvey, and Roxanne L. Quintana (2008) Highly Efficient Zirconium-Catalyzed Batch Conversion of 1-Butene: A New Route to Jet Fuels. Energy & Fuels ASAP Article 29 July 2008 doi: 10.1021/ef800380b
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