ABSTRACT
Metal crystallites are the active phase in many catalysts, particularly those effective for reactions involving hydrogen or oxygen, and Table 3.1 contains a number of illustrative examples. Bulk metals can be fabricated into shapes suitable to go into a reactor, and although a low surface area of metal is provided, if reaction rates are high, as with operation at high temperature, then attractive conversions can be achieved. Diffusion effects are minimal, and with short contact times conditions are ideal for selective oxidations, but products are usually limited to species that are thermally stable. Typical catalysts are metal
granules and wire gauzes, with products species such as NO, HCN, HCHO, and CH3CHO. Less thermally stable molecules require reaction at lower temperatures with compensating higher active phase surface areas to achieve economic reaction rates.
