Techniques for creating catalysts with superior thermal properties

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The rates of most industrial catalytic reactions are limited by heat transport and the thermal properties of the catalysts. Internal temperature gradients (“hot spots”) in reactors are undesirable and should be minimized. Catalysts with high thermal and hydrothermal stability, high thermal conductivity, low (near zero) coefficient of thermal expansion, high thermal shock resistance, and low thermal mass are usually most valuable. The relative importance of each property depends on the type of catalyst and the application. Thermal properties of catalysts can be significantly improved by means of surface modification, bulk modification, and material replacement. Thus, coating the catalyst particles with a CVD diamond layer up to 50 μm thick can reduce the axial and radial temperature gradients in the reactor and improve overall reactor performance. Incorporating silicon carbide particles can significantly increase the thermal conductivity and thermal shock resistance of an alumina catalyst. Replacement of alumina with aluminum nitride, which has a higher thermal conductivity and a lower coefficient of thermal expansion, would reduce the stress in catalyst pellets, resulting in less damage and a longer useful life. Use of catalysts with better thermal properties would enhance the safety and the economic and environmental performance of many important industrial processes. More comprehensive and accurate data are needed on the thermal properties of materials over a wide temperature range. Practical, cost-effective techniques for modifying existing materials and synthesizing new materials to create catalysts with superior thermal properties need to be developed and implemented. Theoretical methods, mathematical models, and computer software are needed for estimating thermal properties, designing catalytic materials with superior thermal properties, relating catalyst properties to reactor performance and process economics, and optimizing catalyst properties for specific applications.