Colloidal Platinum and Palladium Catalysts by Paal

While Sabatier and Ipatieff were experimenting with nickel and copper catalysts others were developing the use of finely divided platinum and palladium catalysts. The main objective was to achieve a range of more practicable hydrogenation procedures at low pressure in either the gas or the liquid phase. 

Carl Ludwig Paal and others used colloidal platinum and palladium catalysts in liquid phase hydrogenation reactions at low temperatures. Aromatic and unsaturated aliphatic compounds such as aldehydes or ketones were easily hydrogenated by either platinum or palladium. Aladir Skita collaborated with Paal in publishing a patent that described some of this work. The colloidal metals could be stabilized by the use of albumen from egg whites, but they were not really practicable and it was difficult to separate them from products. An outline of an early colloidal catalyst preparation is given in Table 3.4. 

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