Heterogeneous Catalysis: Some Recent Developments

Abstract

In recent years major progress has been made in the area of heterogeneous catalysis by metals. Much has been learned about the nature of metal catalysts and of catalytic phenomena on metals. Characteristic patterns of catalytic behavior among the metallic elements have been established for certain classes of reactions, and these patterns provide a first step toward a more comprehensive understanding of catalytic specificity. Studies on metal alloys and related bimetallic catalysts have revived interest in a geometric factor in surface catalysis to complement the traditional electronic factor. Closely related to this geometric factor is the discovery that selectivity, rather than activity alone, is a major factor in reactions on bimetallic catalysts. Concurrent with progress in understanding how catalysts work, advances are also being made in the development of new catalyst systems, examples of which are the bimetallic (or polymetallic) cluster catalysts. Research in this area provides an example of how advances in catalyst technology can be realized within a framework of fundamental research on catalytic phenomena (38).

<b>THE INFLUENCE OF TRANSITION METALS ON THE PERFORMANCE OF Pt Rh Pd/&gamma;-AL₂O₃ THREE WAY CATALYSTS FOR PURIFICATION OF AUTOMOTIVE EXHAUST GAS</b>

“…Percentage d-character is an empirical indicator of the electronic structure of the metal [14]. As the name implies, percentage d-character refers to the contribution of the d-electrons to the spd hybrid orbitals assumed in Pauling's resonance valence band theory [15,16]. Figure 2 (drawn with the aid of Deng's data [17]) shows the correlation of the performance of the Pt Rh Pd-TM/γ-Al 2 O 3 catalysts with the percentage of the d character (d%) of TM.…”

Synthesis and characterization of composites of mixed oxides of iron and neodymium in polymer matrix of aniline-formaldehyde

“…In the past few years, nanocomposite materials have become one of the most extensively studied materials all over the world as they have shown several applications such as in quantum electronic devices, magnetic recording materials, sensors, etc (Anderson et al 1994;Sinfelt 1977).…”

Formation and Functioning of Bimetallic Nanocatalysts: The Power of X‐ray Probes

“…[1][2][3][4] When initially introduced by Sinfelt et al,N i-Cu, Ru-Cu, and Os-Cu were found to reduce undesired CÀCa ctivation for hydrogenolysis compared to monometallic Ni, Ru, and Os,w hile maintaining their CÀH activation abilities for dehydrogenation. [6][7][8][9] Today,bimetallic NPs possess recognized abilities to promote reforming,hydrogenolysis,(de)hydrogenation, and oxidation reactions. [6][7][8][9] Today,bimetallic NPs possess recognized abilities to promote reforming,hydrogenolysis,(de)hydrogenation, and oxidation reactions.…”

“…[5] This early discovery triggered the exploration and widespread use of bimetallic nanocatalysts,i ncluding Pt-Pd, Pt-Ru, Pt-Ir,P t-Re alloys,t o induce selectivity shifts towards desired reaction products. [6][7][8][9] Today,bimetallic NPs possess recognized abilities to promote reforming,hydrogenolysis,(de)hydrogenation, and oxidation reactions. [10] Recently,a ttention has been invested in the development of bimetallic catalysts for upgrading biomass to fuels and chemicals, [10,11] the production of hydrogen, [12] as well as in the use of earth-abundant transition (bi)metallic nanocatalysts.…”