Solid, high-surface-area

See also HIGH SURFACE-AREA SOLIDS, PETROLEUM COKE Alkali metals... 

See entry high surface-area solids See other pyrophoric metals Air, Oil... 

Figure 1.6 Top Low-temperature nitrogen adsorption ( ) and desorption (x) isotherms measured on a calcined SBA-15 mesoporous silica solid prepared using an EO20PO70EO20 block copolymer [54]. Bottom Pore size distribution derived from the adsorption isotherm reported at the top [54]. A high surface area (850 m2/g), a uniform distribution of cylindrical nanopores (diameter —90 A), and a large pore volume (1.17 cm3/g) were all estimated from these data. These properties make this material suitable for use as support in the preparation of high-surface-area solid catalysts. (Reproduced with permission from The American Chemical Society.)...

An important class of industrial catalysts consists of an active component dispersed in the form of very small particles over high surface area solids. As the field of industrial heterogeneous catalysis has developed, catalyst formulations have evolved such that state-of-the-art catalysts often contain two or more metals and/or main group elements. The additives may promote a desired reaction, prevent undesirable side reactions, or enhance catalyst longevity.Bimetallic nanoparticle catalysts in particular are widely... 

The reactivity of NO has also been investigated towards NiO/MgO high surface area solid solutions.25 The EPR spectrum of NiO/MgO powders recorded at 77 K under an NO atmosphere presents two clearly separated signals, assigned to monomeric NO adsorbed on low coordinated Mg2+ ions and to monomeric NO adsorbed on Ni2+ terrace faces. The nature of the NO bonding to Ni2+ ions has been analysed. The EPR spectra showed the presence of one unpaired electron localised on the Ni d shell. Using RO-B3LYP based calcula-... 

It must not, however, be forgotten that conventional techniques (e.g., 13C Fourier transform NMR) can be applied to certain solids of catalytic significance, such as sheet silicates since in many of these systems rapid motion of intercalated or otherwise sorbed organic species secures sharp absorption lines which provide much information about the individual atomic environments. Organic species attached to high surface area solids (such as zeolites, silica, alumina, magnesia, as well as other oxides and their mixtures) are specific examples (6). 

A special case of autoignition occurs for solids and liquids dispersed on high surface area solids exposed to air. Examples include used carbon beds, powdery solids and process fluids that have leaked on fibrous insulation. In all these cases, enough air can get to the solid to yield a significant rate of oxidation, but the heat loss provided through the bulk of the material is too low so that a thermal runaway occurs at temperatures lower than expected from the pure materials. 

See entry HIGH SURFACE-AREA SOLIDS See other pyrophoric metals... 

Relations between the Vibrational Spectra of Adsorbed Probes and the Surface Morphology of High-Surface-Area Solids... 

From Fig. 5, it can be inferred that even for this class of structurally simple solids, the surface of a real high-surface-area solid is so complex that IR spectra of the adsorbed species cannot be decoded straightforwardly. Fortunately, by the progressive sintering method, samples can be virtually... 

The final section in this chapter will discuss several areas of current research, which have attempted to use non-crystalline materials such as metallosilicates or supported oxidation catalysts on high surface area solids. The definition of non-crystalline employed here refers to the support system and not necessarily the active catalytic centre. 

In contrast to current interest in the use of high surface area solids such as zeolites for the physisorption of hydrogen under cryogenic conditions, the earliest work in the storage of hydrogen in zeolites was concerned with a completely different phenomenon. At room temperature and below hydrogen molecules do not enter certain zeolite cages, but at elevated temperatures... 

W. Conner, et al, "Measurement of the Morphology of High Surface Area Solids Inferring Pore Shape Characteristics", in The Characterization of Porous Solids, eds. Unger, Elsevier, Amsterdam, 1988, pp. 273. 

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