Organic Solvent System May Improve Recycling of Catalysts

Thursday, November 11 2010

Noble metals such as platinum and palladium are becoming increasingly important because of growth in environmentally friendly applications such as fuel cells and pollution control catalysts. Because the world has limited quantities of these materials, manufacturers will have to rely on efficient recycling processes to help meet the demand.

Existing recycling processes use a combination of two inorganic acids known as “aqua regia” to dissolve noble metals, a class of materials that includes platinum, palladium, gold and silver. But because the metals are often dissolved together, impurities introduced in the recycling process may harm the efficiency of catalysts produced from the recycled materials.

Researchers at the Georgia Institute of Technology have developed a new organic solvent process that may help address the problem – and open up new possibilities for using these metals in cancer therapeutics, microelectronics, and other applications.

The new solvent system uses a combination of two chemicals – thionyl chloride and a variety of organic reagents such as pyridine, N,N-dimethylformamide (DMF), pyrimidine, or imidazole. The concentrations can be adjusted to preferentially dissolve gold or palladium, and more importantly, no combination of the organic chemicals dissolves platinum. This ability to preferentially dissolve noble metals creates a customized system that provides a high level of control over the process.