Value-added hydrogen

The search for the most optimal and green way of producing, distributing and storing hydrogen has been the focus of much research for several decades. In the past 10 years, this has been stepped up, particularly in the US. In July 2003, the US Department of Energy (DoE) issued, with the offer of research grants, a ‘Grand Challenge’ to the scientific community to discover new technologies, which would resolve the difficulties with hydrogen storage. Much of the funding went to groups working on chemical hydrogen storage technologies, such as boron chemistry and sorbents with high surface-area capacity like carbon nanotubes, aerogels and nanofibres.

Ammonia borane, for example, has been a subject of increased research because of its hydrogen storage capacity, which is close to 20% by weight. It is more hydrogen dense than liquid hydrogen. US scientists at Los Alamos National Laboratory, which is funded by the US Department of Energy (DoE), have demonstrated that vehicles fuelled by hydrogen extracted from ammonia borane can go a further 300 miles on the equivalent of a single tank, which is the benchmark for fuel efficiency set by the DoE.

The US government also tried to encourage researchers to look for ways of linking hydrogen production with the capture and sequestration of CO₂. In 2003, president George W. Bush announced plans for a coal-fuelled power plant, which would produce electricity and hydrogen while capturing and storing the CO₂ emissions underground. Four years later, Mattoon Township, Illinois, was chosen as the location of the project, and a public-private partnership, FutureGen Industrial Alliance, was established, which would use Integrated Gasification Combined Cycle (IGCC) as the chosen technology. 

In 2008, the $1.8bn project was cancelled after the DoE withdrew its support on the grounds of escalating construction and materials costs even before building work had begun. But in February 2013, the DoE announced a new deal with its private sector partners, enabling the project to continue but now based on the cheaper and more practical oxy-combustion technology. Carbon capture and storage (CCS) became the main priority of the project with hydrogen production pushed to the background.

Meanwhile, the focus of research in Europe, funded by the EU and national governments, remains hydrogen production with much lower or zero CO₂ emissions. One of the biggest spenders on R&D into hydrogen and fuels cells is Germany; the National Innovation Programme Hydrogen and Fuel Cell Technology, for example, was awarded €1.4bn by the German government for the period 2007 to 2016 to finance individual projects in this area.

There are several alternative sources of hydrogen being considered, all based on the use of renewable energy sources, such as solar, wind and biomass. Biomass can be converted by gasification into syngas, or into methane via anaerobic digestion, from which hydrogen can be obtained. Nuclear or hydropower could be used to thermally decompose methane.

Increasingly, though, research is focusing on the use of solar or wind power to make hydrogen via the electrolysis of water. Wind-powered electrolysis is a major objective of a €18m project, mostly funded by the German Ministry of Education and Research (BMPF) and led by Bayer Technology Services (BTS) and Bayer MaterialScience (BMS). The other members of the 13-strong partnership include the electricity generator RWE Power, the engineering conglomerate Siemens with expertise in electrolysis technology, and catalysts research units in the universities of RWTH Aachen and Rostock.

As part of this initiative, and to exploit catalyst expertise, the project CO2RRECT – CO₂-Reaction using Regenerative Energies and Catalytic Technologies – is looking to react the hydrogen produced with CO₂ emitted from a local coal-powered electricity generation plant to make hydrocarbons as a source of both fuels and chemical feedstocks. Professor Hans-Wilhelm Engels, BMS research director, says for Bayer the project is a means of ‘creating a new value chain by making use of waste CO₂ from power generation and hydrogen from cheap [wind] energy’.

BMS scientists working with researchers at RWTH Aachen, have already developed a catalytic process for converting CO₂ into polyols, which can then be reacted with isocyanates to give polyurethane foam products, polyurethane coatings and thermoplastic polyurethanes (TPU). In the main, polyols are produced from crude oil derivatives therefore the process offers a real advantage in conserving this depleting resource (C&I, 2013, 1, 15).

A longer term objective of this project is to use waste CO₂ and ‘green’ hydrogen to produce formic acid. Currently, the global demand for formic acid is around 1m t/year with the major uses being in the production of animal feed – as a promoter of the fermentation of silage – in the tanning of leather and in dyeing and finishing of textiles. Formic acid is usually made via reaction of methanol and carbon monoxide to produce methyl formate, which is then hydrolysed to formic acid. Alternatively, formic acid is a byproduct of acetic acid manufacture. If formic acid could be made via a cheaper route that uses ‘green’ hydrogen, waste CO₂ and inexpensive catalysts, then the demand for this chemical is likely to escalate. Indeed, the potential for plentiful supplies of formic acid is stimulating research into its use as a chemical feedstock.

BASF, the largest formic acid producer in the world, is keeping a watchful eye on these developments. With the opening of a new plant at Geismar in the US, the company will have a capacity of 300,000t of formic acid/year. It reckons that formic acid has the potential for a wide range of applications. ‘It’s a real all-rounder,’ says Tatjana Levy, innovation manager in BASF’s intermediates division.

Finland’s Kemira, the second largest producer of formic acid with a capacity of around 100,000t, is also interested in green hydrogen technology. Two years ago, the company signed a memorandum of understanding with Mantra Venture Group, Seattle, US, to exploit Mantra’s electroreduction technology. This uses electricity to separate hydrogen from oxygen in water and then reacts the hydrogen with captured CO₂ to make formic acid. Kemira wants to reuse CO₂ from local cement plants and refineries as well as from coal-fired power stations for formic acid production.

Another chemical that can be produced by combining recycled CO₂ with hydrogen is methanol. The Iceland-based Carbon Recycling International (CRI) has just started producing methanol made from recycled CO₂, and hydrogen and oxygen from the electrolysis of water, by using renewable electricity generated by geothermal energy from Icelandic volcanoes.

A lot of R&D activity is also focusing on producing hydrogen from biomass, again for use as both fuel and chemical feedstock.

At the Leuna chemicals complex in eastern Germany, for example, the industrial gases company Linde has a pilot plant for making hydrogen from glycerol, a byproduct of the manufacture of biodiesel from rapeseed. The glycerol is converted by pyrolysis into syngas by pressure swing adsorption (PSA) – gases are separated under high pressure through adsorption by materials like zeolites.

Since financial incentives for production of biodiesel from food crops is being limited by the EU, Linde is considering applying the technology instead to glycerol made from blue-green algae at the Leuna site. ‘We believe there is a big potential for industrial-scale green hydrogen at Leuna, both as a base chemical and as a fuel for hydrogen networks being created in Berlin and Hamburg,’ says Thomas Hagn, Linde’s technical communications manager.

Linde is also working with the Fraunhofer Centre for Chemical-Biotechnology Processes (CBP) at Leuna on the development of biomass-to-chemicals technologies that could be integrated into a biorefinery to make green hydrogen and other base chemicals.

Kemira, too, has the production of hydrogen from biomass for fuel and biochemicals as one of its priority R&D areas. It believes that organic acids, such as formic acid, acetic acid and propionic acids, in which hydrogen would be one of the feedstocks, could be produced from bio-sludge from water effluent treatment. The company is investigating anaerobic digestion, and gasification of the bio-sludge for hydrogen production.

The company’s target is to ‘make biomass-based chemical production sustainable and economically feasible’ from treated water by utilising side streams for the recovery of organic acids, according to Heidi Fagerholm, Kemira’s chief technology officer.

Laying the foundations for a hydrogen economy in the world’s leading developed countries is proving to be a long process, the success of which will come down to adding value to the hydrogen life-cycle.