4 new chemical technologies that could have an impact

Credit: Umicore

Researchers at Umicore's catalyst laboratory in Hanau, Germany.

Hydrogen is one of the fuels of the future. Fuel cell vehicles that run on hydrogen emit no carbon dioxide, only a tiny trace of water. Unlike electric cars, they can be refueled in minutes. And while H₂ created mostly from methane today, proponents see a future when green hydrogen is produced cheaply by electrolysis of water using energy from the wind and sun.

But hydrogen is also an extremely light molecule that must be compressed for shipping and storage. The infrastructure to transfer it to fuel cell vehicles or power plants exists in only a few places.

Umicore and Anglo American, two big players in precious metals, have formed an R&D venture to advance a new solution to the compression problem: the liquid organic hydrogen carrier, or LOHC.

The idea behind LOHC is to chemically bond hydrogen to a stable liquid carrier. This captured hydrogen can be loaded into a standard fuel tank just like a conventional liquid fuel, eliminating the need for compression, both in the fuel loading lines and in the vehicle itself.

In order for a hypothetical future vehicle to make use of hydrogen, the hydrogen-laden LOHC would pass through a reactor containing a dehydrogenation catalyst. Hydrogen will then be released and fed into the vehicle's fuel cell stack, be it a car, truck or train. The spent LOHC will be removed during the next refueling so that it can be recharged with more H₂.

Umicore and Anglo American formed their partnership in April, building on Anglo American's previous investment in Hydrogenious LOHC Technologies, a German LOHC start-up founded by Peter Wasserscheid, a chemist at Friedrich Alexander University Erlangen-Nuremberg. The focus of the partners is the dehydrogenation catalyst.

Some investors have embraced the LOHC concept. In September, Hydrogenious LOHC raised nearly $60 million from investors, including Chevron, to further develop LOHCs. The company is building a test facility in Dormagen, Germany, where it will store hydrogen in an LOHC and test shipping it to customers.

Hydrogenious LOHC and Umicore agree that the best current LOHC candidate is benzyltoluene, due to its combination of high heat capacity and storage density and low viscosity and surface tension. The molecule has long been an important heat transfer fluid. In July, Hydrogenious LOHC signed an agreement to buy benzyltoluene from Eastman Chemical, which manufactures it in Marl, Germany.

But Umicore and Anglo American say more work needs to be done on the catalyst that dehydrogenates LOHC. On April 26 online presentation to stock analysts to explain the research effort, An Steegen, Umicore's chief technology officer at the time, said that dehydrogenation with the current catalyst system requires too high pressures and temperatures to be practical for vehicle use.

Umicore's role in the collaboration is to develop a new heterogeneous catalyst—specifically, a precious metal attached to an inorganic support—that enables dehydration at lower pressures and temperatures. The company cautions that the project is still in the early stages of development and that it will take 5-10 years before an effective LOHC can be commercialized.

In the April 26 presentation, some analysts questioned the need for an alternative to compressed hydrogen for H₂ fuel systems. Alex Stewart of Barclays Investment Bank pointed out that “99% of the rest of the market is investing in an old technology, which transfers pure hydrogen to hydrogen fuel cells.”

And while the hydrogen vehicle market is nascent, it exists in places like California, which has 47 hydrogen fueling stations. Eric McFarland, chief technology officer of carbon-free start-up C-Zero, says he was once skeptical about filling a vehicle with compressed H₂. But McFarland drives the hydrogen Toyota Mirai in California and says he's comfortable with the fueling process, which isn't much different from a traditional gas fill-up.

Responding to Stewart, Steegen acknowledged that compressed hydrogen is the existing fuel cell vehicle fuel. But he noted that the safeguards needed to make hydrogen-powered vehicles safe — sensors, alarms, special seals in the event of a leak and a high-tech pressurized tank — add significantly to the cost of the vehicles.

Furthermore, aside from the California experiment, converting the world's existing fossil fuel transportation and storage infrastructure to hydrogen has yet to happen and would be a costly undertaking. Switching to a hydrogen-loaded LOHC will allow the existing infrastructure to remain mostly in place, Steegen said.

“That said,” he added, “LOHC is still in the early stages of development. We still need to work on the dehydrogenation catalyst to make it compatible with integrated dehydrogenation. Also, efficiency needs to be improved. However, it has the potential to be basically a very efficient hydrogen carrier into the future.”