ABSTRACT
The Pennsylvania State University, University Park, Pennsylvania
I. Fundamental Issues A. Introduction B. Cradle-to-Grave Approach c. A More Fundamental Approach
II. Applications A. Carbon as a Support for Fine Chemicals Catalysts B. Carbon as a Support for Petroleum Refining Catalysts C. Carbon as a Support for Environmental Control
Catalysts D. Carbon Use as a Catalyst
III. Conclusions
References
243 243 246 252
312 313 323
325 326 334
Carbon materials have been used for decades in heterogeneous catalytic reactions. They help to increase the rate and control the selectivity of
many chemical reactions. They can satisfy most of the desirable requirements for a suitable support: chemical inertness, stability (especially in the absence of molecular oxygen), mechanical resistance, high surface area and optimum porosity. As early as 1963 [1], Hassler reviewed the uses of activated carbon as a catalyst primarily, but also as a catalyst support. Today activated carbon is a well-established, commercially available catalyst support [2]. It is used predominantly for precious metal catalysts (see, for example, Refs. [3,4]), which are widely used in the synthesis of high-value-added chemical products [5]. For example, the Catalytic Reaction Guide published by Johnson Matthey, one of world's leading suppliers of catalysts, has a list of 69 organic reactions catalyzed by precious metals, nine of which (e.g., hydrogenation of benzene, hydrogenation of aliphatic and aromatic nitro compounds) use carbon as the only support material. However, very few large-volume catalytic processes currently use carbon-supported catalysts, despite the steady research in some promising areas such as hydrodesulfurization (HDS) of petroleum fractions or hydrogenation of carbon monoxide. Consequently, a very small fraction of carbon production is destined for catalyst manufacturing. It has been estimated [6], for example, that catalytic applications represent less than 5% of the market value of activated carbons. Yet much research has been done and continues to be conducted in this field, as evidenced by the information summarized in Fig. 1 and from the voluminous literature cited in this review. This situation is a reflection of the fact that
carbon materials enjoy a mixed reputation in both industry and academia, especially as catalyst supports.
