Gold catalysts commercial applications

Most of the published methods for preparing gold catalysts in small research quantities are unlikely to prove suitable for commercial applications.1 Complete removal of precious metal from the liquid phase is desirable when using solution methods deposition-precipitation (DP) techniques, whilst producing highly active catalysts, also consume large quantities of water and the cost of treatment of wastewater is an expensive additional process. Other preparation methods such as appropriate modifications of impregnation via incipient wetness techniques are more likely to be suitable for commercial production if they lead to reproducible, stable... 

This process is conducted under vacuum and deposition is line-of-sight. It is expensive and best suited to planar surfaces having relatively small areas. Impediments to commercial applications are aids to fundamental research. Catalysts can be prepared, studied, and tested under UHV conditions and in the absence of chemical contaminants. Most of our detailed understanding of gold nanoparticle catalysts comes from work on sputter-coated model catalysts. 

Our overall conclusion is that the potential of gold catalysts for stimulating research is considerable and the results will lead to more practical, commercial applications, the full extent of which has still to be envisaged. 

The low temperature water-gas shift (LTWGS) catalysts commercially used for hydrogen and ammonia syntheses processes are based on Cu-Zn0-Al203. These catalysts work at 185-275°C. Non-pyrophoric and very active LTWGS catalysts, as needed for fuel cell applications, are based on supported noble metals, like Pt/Ce02-Al203, in monolytic structures. Catalysts based on gold, such as... 

The potential of gold catalysts for commercial applications has been reviewed [17,93,95,110,149]. The principle advances include catalysis of a number of reactions of commercial interest and demonstration of stability in the liquid and gas phase for use in the following fields of application ... 

Au/TiOj and Au/CeOj can also catalyze WGS. For instance, Sakurai and coworkers found that Au/TiO prepared by deposition-precipitation showed higher WGS activity than Au/TiOj, Au e203, AU/AI3O3, and Au/ZnO prepared by coprecipitation [41]. The activity of the optiinal Au/TiO catalyst was comparable to that of a commercial Cu/ZnO/Al Oj catalyst. In another work, Andreeva and cowoikers demonstrated the application of Au/CeO in WGS and studied the influence of gold loading, contact time, H3O/CO ratio on catalytic activity [42]. 

The parallelism between the two reactions is somehow supported by the similarity of the catalysts, which are active at low temperature in the two reactions. The preferential oxidation (PROX) of CO in the presence of hydrogen represents an important step in the synthesis of pure hydrogen for application in low temperature fuel cells. Noble metals are active for this reaction at very low temperature (100-200°C). Commercial catalysts are typically based on Pt/y-Al203. Supported gold was quite recently discovered to act as an excellent catalyst for PROX as well as for the low temperature (200 K) CO oxidation in waste gases.Copper-based catalysts are also reported to be excellent for the PROX reaction. ... 

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