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New materials in catalysis
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now been elucidated by EXAFS (N. Toshima, M. Harada, T. Yonezawa, K. Kushihashi and K. Asakura, J. Phys. Chem., 95 (1991) 7448). The most active and selective Catalyst has clusters with a Pd/Pt ratio of 4/l and the EXAFS analysis of this catalyst has been interpreted as a Pt core structure, with 42 Pd atoms on the surface and a core of 13 Pt atoms. It is notable that a pure Pd catalyst is less effective, so it appears that the sub-surface Pt atoms modify the catalytic properties of the surface Pd atoms. Another less active catalyst, with a Pd/Pt ratio of l/l, was also examined. These clusters were found to have a modified P&core structure, with 28 Pt atoms connected directly with each other in the core and on the surface and 17 Pd atoms distributed in three islands on the surface of the cluster. Catalysts consisting of glassy or amorphous metals have been studied extensively in recent years. The various techniques available for extremely rapid cooling necessary to prevent crystallisation usually produce materials of low surface area, but a new sonochemical synthesis of amorphous iron has been developed (K.S. Suslick, S.-B. Choe, A.A. Cichowias and M.W. Grinstaff, Nature, 353 (1991) 414) to produce very small amorphous panicles of iron of high purii. Cavitation by ultrasound gives heating and cooling rates that are greater than 2 x 10’ K s-’ and may be as large as 1013 K s-l. Suslick et al. have used this technique for iron pentacarbonyl both as a solid and in solution in decane. Element analysis showed the solid product to be metallic iron with 3% C and 1% 0, probably from carbon monoxide decomposition. (It i$ noteworthy that all previous ironcontaining metallic glasses contained typically more than 20% of other components). Various techniques showed the iron to be amorphous, e.g. no peaks were seen by
applied catalysis A: general
X-ray diffraction analysis, but on heating to 350°C under nitrogen the peaks for a-iron appeared. The catalytic potential of the iron was examined in the Fischer-Tropsch reaction at 2OO’Cand the hydrogenolysis/dehydrogenation of cyclohexane at 250°C. The observed catalytic activities were an order of magnitude higher than those found with a catalyst of crystalline iron powder. New Materials in Catalysis New materials always open up the possibility of qualitative advances in catalytic properties, in contrast to the incremental but still valuable improvements obtained by optimising existing catalysts. Too often though, the promised advance turns out to be illusory or too ephemeral to be of industrial use. Nevertheless enthusiasm for trying the new needs to be kept up, even in the most cynical of us, and this should be stirred by a recent review (B. Delmon and P. Grange, Erdol Erdgas Kohle, 107 (1991) 376). The authors look at the prospects coming from research which could lead to the development of new catalysts and describe work on layered and pillared materials, hybrid (two-phase) and other catalysts. Sachtler Wins Petroleum Chemistry Award It has been announced in the ACS Division of Petroleum Newsletter that Prof. Wolfgang Sachtler of Northwestern University has won the 1992 ACS Award in Petroleum Chemistry sponsored by the Amoco Foundation. An Award Symposium in honour of Prof. Sachtler, sponsored by the Division of Petroleum Chemistry, is being organized for the April San Francisco Meeting. The Award recognizes Prof. Sachtler’s significant contributions to the technology Volume 82 No. 2 -
16 March 1992
now been elucidated by EXAFS (N. Toshima, M. Harada, T. Yonezawa, K. Kushihashi and K. Asakura, J. Phys. Chem., 95 (1991) 7448). The most active and selective Catalyst has clusters with a Pd/Pt ratio of 4/l and the EXAFS analysis of this catalyst has been interpreted as a Pt core structure, with 42 Pd atoms on the surface and a core of 13 Pt atoms. It is notable that a pure Pd catalyst is less effective, so it appears that the sub-surface Pt atoms modify the catalytic properties of the surface Pd atoms. Another less active catalyst, with a Pd/Pt ratio of l/l, was also examined. These clusters were found to have a modified P&core structure, with 28 Pt atoms connected directly with each other in the core and on the surface and 17 Pd atoms distributed in three islands on the surface of the cluster. Catalysts consisting of glassy or amorphous metals have been studied extensively in recent years. The various techniques available for extremely rapid cooling necessary to prevent crystallisation usually produce materials of low surface area, but a new sonochemical synthesis of amorphous iron has been developed (K.S. Suslick, S.-B. Choe, A.A. Cichowias and M.W. Grinstaff, Nature, 353 (1991) 414) to produce very small amorphous panicles of iron of high purii. Cavitation by ultrasound gives heating and cooling rates that are greater than 2 x 10’ K s-’ and may be as large as 1013 K s-l. Suslick et al. have used this technique for iron pentacarbonyl both as a solid and in solution in decane. Element analysis showed the solid product to be metallic iron with 3% C and 1% 0, probably from carbon monoxide decomposition. (It i$ noteworthy that all previous ironcontaining metallic glasses contained typically more than 20% of other components). Various techniques showed the iron to be amorphous, e.g. no peaks were seen by
applied catalysis A: general
X-ray diffraction analysis, but on heating to 350°C under nitrogen the peaks for a-iron appeared. The catalytic potential of the iron was examined in the Fischer-Tropsch reaction at 2OO’Cand the hydrogenolysis/dehydrogenation of cyclohexane at 250°C. The observed catalytic activities were an order of magnitude higher than those found with a catalyst of crystalline iron powder. New Materials in Catalysis New materials always open up the possibility of qualitative advances in catalytic properties, in contrast to the incremental but still valuable improvements obtained by optimising existing catalysts. Too often though, the promised advance turns out to be illusory or too ephemeral to be of industrial use. Nevertheless enthusiasm for trying the new needs to be kept up, even in the most cynical of us, and this should be stirred by a recent review (B. Delmon and P. Grange, Erdol Erdgas Kohle, 107 (1991) 376). The authors look at the prospects coming from research which could lead to the development of new catalysts and describe work on layered and pillared materials, hybrid (two-phase) and other catalysts. Sachtler Wins Petroleum Chemistry Award It has been announced in the ACS Division of Petroleum Newsletter that Prof. Wolfgang Sachtler of Northwestern University has won the 1992 ACS Award in Petroleum Chemistry sponsored by the Amoco Foundation. An Award Symposium in honour of Prof. Sachtler, sponsored by the Division of Petroleum Chemistry, is being organized for the April San Francisco Meeting. The Award recognizes Prof. Sachtler’s significant contributions to the technology Volume 82 No. 2 -
16 March 1992