An energy source that generates no carbon dioxide emissions, “CO2-free hydrogen” is drawing attention around the world from parts of the business sector promoting the green transition.

One major method of transporting CO2-free hydrogen efficiently involves the use of storage materials known as hydrogen carriers. Methylcyclohexane (MCH), a liquid produced by the chemical reaction of hydrogen with toluene, is an efficient hydrogen carrier due to its large hydrogen concentration capacity, which is over 500 times higher on a per-volume basis than that of hydrogen gas.

Takeru Ishimoto from the Hydrogen Business Department’s Domestic Hydrogen Supply Chain Group described the recent strategies for building hydrogen supply chains.

“It thus plays a key role in building hydrogen supply chains. The primary reason is related to similarities between hydrogen supply chain processes (MCH transport and hydrogen extraction) and those of petroleum products. This means that existing assets related to oil refineries, such as petroleum tanks and oil tankers, can be utilized as a measure to substantially cut initial investment costs. Also, MCH, a liquid that is stable at ordinary temperatures and pressures, is easy to handle and can be stored in large quantities, which provides it with a strong advantage in terms of energy security.”

Research and development efforts are currently being promoted around the world in pursuit of innovative hydrogen transport technology. Under this background, ENEOS is endeavoring to achieve more efficient MCH production processes with the aim of lowering hydrogen market prices. One of the latest achievements from this endeavor is Direct MCH®, an attention-grabbing and worldwide pioneering technology.

Kota Miyoshi, a member of Direct MCH® development team, Hydrogen Carrier R&D Group at the Central Technical Research Laboratory’s Innovation Technology Center, explained the technology as follows: “The conventional process of producing MCH using renewable energy consists of two steps: (1) electrolyze water using renewable energy to separate it into oxygen and hydrogen, which is then stored in high-pressure tanks; and (2) mix the stored hydrogen with toluene to induce a chemical reaction that produces MCH. In comparison, Direct MCH® aims to replace the conventional two-step process of water electrolysis and MCH production with a single-step process in which toluene is supplied directly into the water electrolyzer to induce an electrochemical reaction that produces MCH. This can eliminate the need for hydrogen gas tanks and MCH production plants, thus streamlining the production process and achieving a substantial cost reduction.”

Miyoshi started the related study based on a suggestion made by his then supervisor when he was in his third year with the company and engaged in fuel cell development. The supervisor suggested considering the possibility of producing MCH by feeding toluene directly into a fuel cell device to create an appropriate reaction.

”In those days,” Miyoshi recalled, “when the whole industry was seeking to create high-purity hydrogen gas by removing as many impurities as possible, the idea of adding other elements, including toluene, would have been rejected as being preposterous by many researchers. However, our team gave this unconventional approach a try, and it proved to be workable as a result of our experimentation. The full-scale project to pursue the theme was then launched at the Laboratory around 2011 to create a proprietary technology belonging to ENEOS.”

ENEOS is looking at Australia, a country with abundant sources of renewable energy, as a target for implementing Direct MCH® for real-world business development. In 2021, the technology was adopted for a demonstration project for the export of solar energy-based green MCH produced in Australia to Japan, where the extracted hydrogen was used to power a fuel cell vehicles (FCV). The result of a partnership among ENEOS, Chiyoda Corporation and Queensland University of Technology, the project was the first of its kind in the world to succeed.

In January 2023, ENEOS established a green MCH plant in Australia with a 150 kW electrolyzer offering an electrode surface area of three-square meters and a 250 kW solar power generator. In June of the same year, MCH produced by the plant was exported to Japan, and the related hydrogen was extracted at a hydrogen station to power a fuel cell bus to run on a public road. Based on this track record, the company will move forward to expand the real-world implementation scope, primarily by developing a megawatt-class large electrolyzer, a minimum requirement for commercial-scale operation, and related processes.

“In order to create a hydrogen-based economy, it is imperative to lower hydrogen prices to levels affordable to many users,” said Ishimoto. “Despite the technical challenges, we believe Direct MCH®, a large-capacity, stable, and efficient hydrogen carrier production technology, will play a key role in popularizing hydrogen so that many people can enjoy the benefits. I was previously engaged in petroleum production before being transferred to the Hydrogen Business Department, which was chiefly in response to the major shift toward carbon neutrality. Although this situation is posing a huge challenge to the oil production industry, we should look at it as a good opportunity to become a leading player in supplying carbon-neutral energy and materials. We are striving to develop our proprietary technology to facilitate the widespread use of hydrogen.”

Ishimoto and Miyoshi both emphasized the importance of promoting technical collaborations with other companies to achieve this goal, rather than pursuing independent efforts. ENEOS is building CO2-free hydrogen supply chains based on Direct MCH® to cover the production, transport, and use of products, with the objective of contributing to the achievement of a carbon-neutral society.

This demonstration was conducted as part of Green Innovation Fund Projects of Large-scale Hydrogen Supply Chain Establishment / Direct MCH electrosynthesis technology development commissioned by the New Energy and Industrial Technology Development Organization (NEDO).