Surface areas palladium blacks

Unsupported palladium catalysts are often unstable in use at elevated temperatures and/or high hydrogen pressures. Yada et al. obtained a highly stable palladium black by precipitating palladium hydroxide from palladium chloride solution with an aqueous sodium aluminate instead of sodium hydroxide.177 The palladium catalyst obtained by reduction of the palladium hydroxide prepared with a 1M sodium aluminate solution at pH 10, in the same way as described above, kept a high surface area of 139 m2 g 1 even after the reduction at 200°C in a flow of hydrogen, compared to only 2.0 m2 g 1 with the catalyst prepared using a sodium hydroxide solution as precipitant. The thermally stable catalyst was found to contain 13 ppm of sodium and 1400 ppm (0.14%) of aluminum. 

The surface areas of a number of commercial palladium blacks were measured using the BET procedure as well as hydrogen chemisorption, electron microscopy and X-ray diffraction analysis. These data showed that these blacks had particle sizes ranging from about 7 to 140 nm and surface areas between 70 and 4 m2/g.20 Ruthenium blacks prepared by the reduction of different samples of ruthenium oxide and ruthenium chloride were found to have surface areas ranging from 3-20 m2/g.21... 

Work in this area is, of course, not limited to using Pt black as the electrocatalyst. Virtually any electroactive catalyst, such as gold, rhodium, or palladium, which can be prepared with a particle size small enough to provide the necessary surface area and RF penetration, can be investigated. 

Surface areas of palladium and palladium-silver alloys were not measured. They were assumed to be about 2 m.Vg., because it was previously found that a similar preparation of platinum black had a surface area of... 

Catalysis. Platinum and Pt alloys are preferably applied in heterogeneous catalysis as wire nets or powders with a high specific surface area ranging from 20 to 1000 m /g ( platinum black, palladium black ) on carbon or AI2O3 supports. The catalytic effec-tivity is structure-sensitive. Figure 3.1-300 show an example of the catalytic action of Pt for the reaction rate and the product selectivity on different crystal planes [1.218]. Pt—Pd—Rh alloys are the main active constituents of catalytic converters for automobile exhaust gas cleaning. 

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