Scientists have developed a hydrogen-making catalyst that uses cheaper materials and yields much fewer contaminants than do the current processes, while extracting the element from common renewable plant sources. Further, the new catalyst lies at the heart of a chemical process the authors say is a significant advance in producing alternate fuels from domestic sources.
In the journal Science, James Dumesic, John Shabaker and George Huber, of the University of Wisconsin at Madison, report developing the catalyst from nickel, tin and aluminium and using it in a process called aqueous-phase reforming (APR), which converts plant by-products to hydrogen. The process performs as well as current methods that use precious metals such as platinum, yet runs at lower temperatures and is much cleaner.
‘The APR process can be used on the small scale to produce fuel for portable devices, such as cars, batteries, and military equipment,’ said Dumesic. ‘But it could also be scaled up as a hydrogen source for industrial applications, such as the production of fertilizers or the removal of sulphur from petroleum products.’
Hydrogen is a ‘clean’ fuel because when it burns, it combines with oxygen to form water; no toxic by-products or greenhouse gases are produced in the process. The APR process extracts hydrogen from a variety of biological sources, especially simple carbohydrates and sugars generated by common plants.
Platinum is known to be an excellent catalyst in a number of chemical reactions. It is one component in a car’s catalytic converter, for example, that helps remove toxins from automobile exhaust. Catalytic platinum (Pt) and nickel (Ni) are preferred over other metals because they process reaction molecules much faster. But pure nickel, unlike platinum, re-combines the hydrogen product with carbon atoms to make methane, a common greenhouse gas.
Using a specially designed reactor, the team found a match in a modified version of what researchers call a Raney-nickel catalyst. Raney-nickel is a highly porous catalyst made of about 90 per cent nickel (Ni) and
10 per cent Aluminium (Al).
While Raney-nickel proved somewhat effective at separating hydrogen from biomass-derived molecules, the researchers improved the material’s effectiveness by adding more tin (Sn), which stops the production of methane and instead generates more hydrogen. Relative to the other catalysts, the new Raney-NiSn can perform for very long time periods (at least for about 48 hours) and at much lower temperatures (roughly
225 degrees Celsius).
Which, according to the passage, is one of the reasons why pure nickel may not be a preferred catalyst?