by Jim Lane
News has emerged from Gevo (GEVO) in Colorado and New Mexico’s Los Alamos National Lab that the two will collaborate to improve the energy density of Gevo hydrocarbon products to meet product specifications for tactical fuels for specialized military applications such as RJ-4, RJ-6 and JP-10, which are currently purchased by the US Department of Defense (DoD).
High energy-density fuels are currently used in air and sea-launched cruise missiles used by the US military forces. If this project is successful in scaling the fuels cost-effectively, there may be an even broader application in the general aviation sector, enabling higher energy density jet fuel that would provide superior mileage to traditional aviation fuels.
Gevo and LANL are looking to develop a low-cost, catalytic technology that would be bolted-on to Gevo’s existing isobutanol-to-hydrocarbons process to produce high energy density fuels). With the successful scale-up of this technology, it is believed that Gevo’s HEDFs could be produced at a lower cost than the petroleum-based equivalent, even at current oil prices.
ChemCatBio, a consortium within the US Department of Energy, awarded funding to LANL in support of the project.
The JP-10 backstory
Back in 2012, researchers at the Naval Air Warfare Center, Weapons Division reported that they had synthesized a fuel that had JP-10esque properties — including fuel density ranges from 137,000 to 142,000 BTUs per gallon — from a blend of biobased terpenese, including pinene, limonene and turpentine. They used Nafion, Nafion SAC-13, and Montmorillonite K-10 as catalysts and achieved 90 percent yields from selected feedstocks.
At the time, we reported that the military has been paying as much as $25 per gallon for for certain types of advanced, high performance fuel used in limited quantities, including JP-10. It costs so much to make by conventional means that its use is typically restricted to air-to-air and air-to-surface missiles.
The JP-10 conundrum
What makes JP-10 attractive? Specifically, it has 11 percent higher density than conventional JP-8 (Jet A) fuel – clocking in at 142,000 BTUs per gallon compared to 125,000 for jet fuel (gasoline, by the way, has 115,000 BTUs).
What makes it unattractive? Well consider the problem that Raytheon faced, when it saw JP-10 prices soar from $13.09 per gallon to $25 per gallon between 2006 and 2010.
Now, what military officials will assure you is that it costs so much because they’re not buying much – entirely true.
The whole problem of JP-10 is that, irrespective of volume, it is going to cost one heck of a lot if made from petroleum because refining the molecule in question, exo-tetrahydrodicyclopentadiene, from crude oil is like processing diamonds out of dirt.
The allure of terpenes
Back in 2014, a team of researchers from the Naval Air Warfare Center at China Lake and NIST, headed by Dr. Ben Harvey, observed in a journal article:
“Renewable fuels with densities that exceed those of conventional jet fuels by up to 13% can be generated from multicyclic sesquiterpenes. This advance has the potential to improve the range of aircraft, ships, and ground vehicles without altering engine configurations. In addition, as strategies to efficiently convert lignocellulosic biomass into sugars improve and organisms are developed that can utilize these sugar mixtures and convert them to sesquiterpenes, these fuels can be produced on a scale that would help supplant significant quantities of petroleum.”
The far, far frontier of hyper-dense fuels
It’s a relatively thin line between explosives and fuels — after all, the burning of fuel is a controlled exercise in explosion — and the current darling in explosives research, CL-20 (for purists, that’s 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane — try pronouncing that at the end of a long day at the office), was originally developed by the Navy as a rocket fuel. It has a 5% improvement in detonation pressure than HMX, and HMX in turn has more than twice the detonation pressure of TNT. In short, these are nasty explosives.
Out there on the horizon — at almost a 30% increase in detonation pressure (and significantly more dense, too), are the nitrocarbons, and specifically octanitrocubane, known as ONC. As an explosive, it has a predicted detonation pressure more than 25% greater than HMX. It’s as nasty as they come.
One man’s explosive is another man’s fuel
But ONC has some interesting properties as a fuel. First of all, it’s dense — you can pack quite a bit of it into a missile. It’s high heat of combustion makes it possible for missiles to travel farther or carry more explosive power, without changing missile design.
But here’s the most interesting aspect. As it has no hydrogen, there isn’t any water produced when it burns, and you don’t see that tell-tale vapor stream behind a rocket or jet that uses it. Making the rockets or jets harder to track — it’s a threat-multiplier, and improves stealth.
All of which reminds us that a renaissance in fuel development — for military or aviation purposes — may well be upon us. The arrival of synthetic biology, a new generation of catalysts, improved lab skill and the availability of cellulosic sources for fuels — this potent mix of new materials and strategies is being employed in some of the US’s leading labs to explore the new opportunities for high-performance fuels.
Let’s look at some of the molecules that deliver at the 140,000 range of JP-10, and beyond.
Exo-THDCP. Now, we’re in the range of the fuel spec known as JP-10. It’s also known, somewhat less euphonically, as exo-tetrahydrodicyclopentadiene, or exo-THDCP. Generally, this is rocket fuel, used in very small quantities because, made from petroleum it costs $25 per gallon.
Neoclavane. One candidate molecule is neoclovane. Harvey and colleagues noted “a fuel composed of only neoclovane would beexpected to have a density of B0.92 g mL1, with a calculated volumetric NHOC of nearly 141 000 Btu gal.” That’s definitely in the JP-10 range, and this research is based on the afore-mentioned real-world fuels development at Allylix.
But what about the world beyond the 140,000 BTU range and JP-10. That brings us to the mysterious and high-powered RJ-5 military fuel spec, which calls for a net heat of combustion of 161,000 BTUs.
Perhydroinorbornadiene. Generally, RJ-5 is missile fuel, and is composed of perhydroinorbornadiene, a norbornadiene dimer. Norbornadiene is difficult and expensive to make — but what a fantastic target for synthetic biology and advanced catalysis. Not only do you have a ready market as high as $25 per gallon — the kind of pricing structure (that is, $25+ per gallon in the early days, reaching for mass markets later, at scale) is well-suited to technology development — not dissimilar to the structure for, say, iPhones and iPads.
But you not only have a great cost opportunity, there’s a good performance opportunity. It doesn’t only have to do with payload or mission range — technology delivered via flat-top carriers come into range sooner. 500 miles in additional missile range means that a 35-knot carrier, steaming into a hot spot, can project air power 12 hours sooner than a carrier carrying conventionally-fueled missiles.
Dr. Harvey and colleagues at China Lake have been investigating the potential to convert b-pinene into fuels that meet the RJ-5 spec. They reported:
Pinene dimers synthesized with these heterogeneous catalysts have a density and net heat of combustion comparable to JP-10. High density fuel candidates have been synthesized in up to 90% yield from β-pinene, a renewable strained bicyclic compound, which can be derived from wood and plant sources. These novel syntheses are based on heterogeneous acidic catalysts (also referred to as heteropolyacidic catalysts) including Montmorillonite-K10 and Nafion NR-50 which promote selective isomerization and dimerization of pinenes under moderate conditions (e.g., 80- 120°C, such as about 100 °C, and about atmospheric pressure).
Pinene is pretty abundant, all in all — given that it’s found in, er, pine trees. That pine-tree smell? That’s pinene.
Beta-pinene, used in Harvey’s work, can be found in parks all over the world via Maritime pine (pinus pinaster), which is native to North Africa and is currently grown in Hawaii and North Carolina, which is good news for the carriers out of Pearl or Norfolk.
Beyond 160,000 BTUs
Octanonitrocubane. Here, we move beyond the “work in some lab somewhere” level and into the world of “it’s possible, but no one’s yet working on it” . And right back to ONC, or octanonitrocubane. It’s been described as “the most powerful nonnuclear explosive known.”
Until the 1960s, it was not even believed that cubanes, which had previously been known strictly as a theoretical molecule, could be synthesized at all; then, a team led by Eaton and Cole at the University of Chicago managed to synthesize it in 1964. Cubane (C8H8) looks like a cube — with each of eight corners occupied by a carbon atom, to which is attached a protruding hydrogen atom. Cubanes are possessed of a level of “angle strain” that make them highly reactive, and highly explosive. Perfect for our purposes.
How explosive? As noted above, ONC is reported to have a 30% higher explosive presure than CL-20 explosives — it’s nasty. We haven’t seen NHOC figures for the molecules, used as fuel — but you can bet they are going to generate a tremendous amount of energy, and well above 160,000 BTUs.
DNH and HNHAH. Well, consider DNH and HNHAH, known amongst their friends as dodecanitrohexaprismane (DNH) and hexanitrohexaazaprismane (HNHAH) have higher energy than ONC. Their part of a class of molecules known as “cage explosives” and you can read about them in Strategic Technologies for the Army of the 21st Century.
At one stage, a team from the Institute for Computation in Molecular and Materials Science at Nanjing University reported “new strategies to design two novel and super-high energy cage explosives: dodecanitrohexaprismane (DNH) and hexanitrohexaazaprismane (HNHAH)…results indicate that DNH has much higher energetic properties than ONC…although HNHAH has lower energetic properties than DNH, it has higher energetic properties than ONC slightly.”
Reaction from the stakeholders
“High energy density fuels have the potential to increase the range of an aircraft or increase the payload that could be carried,” said Dr. Andrew Sutton of Los Alamos National Laboratory. “That gives an obvious tactical advantage, but if this could eventually be scaled for wider use then translating these benefits to commercial airlines would have an even greater global impact.”
“Currently, certain HEDFs are supplied by limited suppliers, so the DoD is interested in supporting alternative sources of these fuels, and potentially at a lower cost,” said Gevo CEO Dr. Patrick Gruber. “The added benefit that this would be a renewable fuel that helps reduce greenhouse gas emissions