摘要:

The most frequently discussed question in the kinetics of heterogeneous catalytic reactions is whether, in deriving rate equations, the active centers of a catalyst should be regarded as uniform or nonuniform. The literature (cf. Refs. 1–3) shows that the kinetics of heterogeneous catalytic reactions is most frequently described by some tape of Langmuir-Hinshelwood rate equations (LHRE) which are based on the assumption of uniformity of active centers (the so-called ideal surface). In most cases these equations fit the experimental data very well. This, however, cannot be considered to prove their theoretical validity, since the agreement may result from the ability of the equations to successfully approximate more complex kinetics. The objection against the use of LHRE stems from the fact that for a majority of catalytically active solid substances, the nonideality of the surface, i.e. the nonuniformity of adsorption sites, has been established by adsorption measurements. On the other hand (cf. Refs. 2 and 4)it is assumed that of a variety of adsorptionally active sites, only a small fraction, representing quasi-ideal surfaces, might be active in a given reaction. As with most catalysts, we have no possibility of verifying whether catalytically (not adsorptionally) active sites are equivalent or not, and thus the controversy remains unresolved.

ISSN:0161-4940    

DOI:10.1080/03602457708079633

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Some techniques are considered to be of prime importance in the study of adsorption phenomena and of heterogeneous catalysis, and they are employed in all research laboratories active in these fields. Volumetry, gravimetry, and reactors of different types, associated or not with gas chromatographs, belong to this category. When a laboratory is regularly involved in studies of gas-surface interactions, the techniques of IR spectroscopy, mass spectrometry, x-ray diffraction, and electrical and magnetic measurements will also be developed. If the laboratory receives good financial support, it will probably invest in EPR, electron microscopes, or in some of the more recent techniques, such as ESCA, LEED, and Auger spectroscopy.

ISSN:0161-4940    

DOI:10.1080/03602457708079634

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The rare earth (lanthanide) oxides, although constituting a closely related group of compounds, exhibit a rich variety of characteristic behaviors and solid-state properties, including several features that make them interesting subjects for Catalytic studies. Abundances and costs of these materials parallel those of the rare earth metals themselves, and range from common and fairly inexpensive (e.g. La2O3and CeO2) to scarce and relatively costly (e.g., Tm2O3and Lu2O3). All are quite refractory and nonvolatile, having melting points in excess of 2000° C, and some display a complex array of nonstoichiometric compositions. Most of the oxides are paramagnetic, with stable cationic electron configurations containing as many as seven unpaired 4f-electrons, and, as escheated from their periodic location, all are quite strongly basic. However, although the catalytic and surface properties of alkali, alkaline-earth, and other basic oxides have been extensively studied and documented [1], equivalent information about the series of basic rare earth oxides has only begun accumulating during the last 10 to 15 years. The increased attention that is currently being focused on these substances has paralleled both a developing realization of some of their unique catalytic properties and their increasing availabilities in purities high enough to warrant fundamental investigations.

ISSN:0161-4940    

DOI:10.1080/03602457708079635

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

As a result of the considerable publicity that has been given to localized shortages of crude oil and of natural gas, attention has been focused on the conversion of energy-producing feedstocks from a less to a more desirable form. This may involve catalytic processes, such as coal gasification [1] or steam reforming [2], or noncatalytic processes, such as steam cracking [3] or hydrogasification [4].

ISSN:0161-4940    

DOI:10.1080/03602457708079636

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Why very small metal clusters? From a practical standpoint, industry often wants its metallic catalysts in a finely divided form so as to maximize the surface area available for a given mass of metal. Obviously, stability toward agglomeration and reactant accessibility are also necessary prerequisites for the successful performance of highly dispersed metal particle catalysts. Solid supported catalysts usually achieve this end. Moreover, such catalysts offer the advantage of convenient handling in a process system; however, technical metallic catalysts are usually ill defined and poorly understood, and better defined systems are necessary for fundamental experimental work.

ISSN:0161-4940    

DOI:10.1080/03602457708079637

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

World oil consumption has tended to increase even since the era of high prices begin following the oil crisis of 1972. Social concern regarding environmental problems has mounted daily. Controls have been placed on emission of pollutants into the ambient air in connection with production activities, not only for the concentration of pollutants, but also, as in Japan for example, for the total amount of pollutant emitted. In particular, steam power plants consuming large amounts of fossil fuels have taken countermeasures to prevent air pollution by using low sulfur fuel or by performing desulfurization of stack gases.

ISSN:0161-4940    

DOI:10.1080/03602457708079638

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0161-4940    

DOI:10.1080/03602457708079632

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor