Clean hydrogen from renewable raw materials
In the game about the energy supply of the future, the cards are being reshuffled. Vegetable oils as a regenerative energy source could make an important contribution - if they didn't tend to form soot and annoying deposits. The detour via the energy carrier hydrogen offers a solution with suitable catalysts. Advertising is only too happy to forget the subtle difference. In her spots, she loudly praises hydrogen as the clean energy source of the future. As a source, mind you, without wasting a thought on where this source gets its bubbling energy from. If the creative minds in the agencies had followed the flow back towards the origins, they would have been amazed to come across completely different sources. The sun, for example, whose energy splits water. Or incinerators that use the chemically stored energy of different substances with catalyzed reactions. The hydrogen comes from their drives, which therefore plays the role of a promising energy carrier – not an energy source.
Getting the hydrogen is therefore an important goal of a sustainable energy strategy. And at this point there is still a lot to do for the present. For example, when extracting the gas from important regenerative raw materials such as vegetable oils or liquefied biomass. It is true that there are already several methods for using the mixtures of hydrocarbon compounds directly. However, they struggle with an annoying obstacle: part of the carbon settles on the necessary catalysts and clogs their reactive pores.
The solution to the problem could be to first split the oils into hydrogen and carbon oxides. But here, too, similar difficulties stand in the way of a continuous process, because the required heat of reaction is difficult to transport sufficiently quickly into the material. A hurdle that scientists led by James Richard Salge from the University of Minnesota may have now overcome.
The researchers built a reactor in whose chamber an injection nozzle shot fine droplets of soybean oil or biodiesel with a diameter of less than half a millimeter. There, a ceramic foam is waiting for the material, which contains small particles of rhodium-cerium. A good flow of air supplies the whole thing with oxygen. Once the catalyst had reached a starting temperature of around 1000 degrees Celsius with the help of a methane flame, the actually desired conversion processes took place solely with the heat of reaction released in the process. Within milliseconds, the vegetable oils broke down into hydrogen, carbon monoxide, and other small molecules, none of which clogged the catalyst.
So far, Salge and his colleagues have only demonstrated the basic feasibility of the method in their experiments. However, they suspect that because of the high temperature of the catalyst, a wide range of oils and fats would be suitable as starting materials, including even used cooking oil. Any impurities would simply evaporate. And perhaps even pulverized solids could be converted in this way. Although hydrogen would still not be a source of energy, its chances as an energy source in the new millennium would have increased considerably.
