Publisher Summary The properties of a surface are influenced by the surface groups and the knowledge of their existence and of their chemistry are important for many technological processes This chapter examines the surface compounds on carbon—microcrystalline carbon, graphite, and diamond—on silica, on titania, and on alumina and silica–alumina Most important and best known among the surface compounds of carbon are those with oxygen and with sulfur Thus, two kinds of surface oxides are known Basic surface oxides are formed always when a carbon surface is freed from all surface compounds by heating in a vacuum or in an inert atmosphere and comes into contact with oxygen only after cooling to low temperatures Acidic surface oxides are formed when carbon is treated with oxygen a temperatures near its ignition point Unambiguous identification of carboxyl groups has been achieved by two reactions of the acyl chlorides: Friedel–Crafts reaction and Schmidt rearrangement

Chemical Identification of Surface Groups

Publisher Summary This chapter focuses on the application of a temperature-programmed desorption method to obtain information on the active centers of catalysts. In principle, this method is similar to the flash-filament desorption method. However, modifications have been made to make the construction and operation of the apparatus easier and to adapt it to studies of materials other than metals—oxide catalysts. An additional important feature of the modified technique is that it permits simultaneous study of a chemisorption process and the surface reaction that accompanies it. The temperature-programmed desorption technique consists of the several steps: (1) catalyst pretreatment, (2) preadsorption of the adsorbate, (3) evacuation after preadsorption to remove the physically adsorbed gas, (4) programmed desorption of the residual chemisorbed gas into the stream of a carrier gas, (5) detection of the desorbed gas in the carrier, and (6) trapping and analysis of the desorbed gas to establish its identity.

Application of a Temperature-Programmed Desorption Technique to Catalyst Studies

Nickel-based solid catalysts for ethylene oligomerization – a review

Publisher Summary This chapter focuses on organic catalysis over crystalline alumiosilicates. Zeolites are crystalline aluminosilicates composed of SiO4 and AlO4 tetrahedra arranged in various geometric patterns. The chapter discusses reactions over a wide variety of crystalline aluminosilicates and emphasizes on catalysis over X- and Y-type faujasites. Unusual opportunities for organic catalysis were found to exist when these were base exchanged to substantially eliminate their alkali metal content. It is shown that catalytic activity in ion-exchanged faujasites is influenced by cation type, cation location in the lattice, zeolite Si/Al ratio, and the presence of proton donors. The existence of several crystallographically distinct cation locations provides the basis for a potential heterogeneity of sites in catalytic reactions. The Linde workers made calculations for the electrostatic field strengths of surface cations near SII and SIII in an X-type zeolite of Si/Al ratio 1.0 and in a Y-type zeolite of Si/Al ratio 2.0. In both cases, the fields has been significantly larger near SIII than SII at a distance of 2 Ǻ from the center of the cation for the univalent cation-exchanged systems, provided both sites are occupied.

Organic Catalysis over Crystalline Aluminosilicates

Although carbon is often considered as the dominant element in terms of covalent bond formation, phosphorus can undoubtedly be considered a s a serious competitor for this position [1]. Further, at least in principle, phosphorus is potentially capable of forming more compounds than carbon. For a variety of reasons, both academic and practical, interest in phosphorus compounds has increased markedly over the last decade. It is not unexpected, then, to find that the use of compounds of phosphorus as catalysts has also accelerated. Unfortunately, a s is often the case in science, the practice outruns the theory with such catalysts, but industrialists and academicians alike have recently displayed an enhanced interest in the mechanisms of catalytic activity on such catalysts.

Kazuko Kimura

Papers

The effective site on acid catalysts revealed in n-butene isomerization

Tracer study of ethylene dimerization over nickel oxide-silica catalyst