Showing papers in "Catalysis Reviews-science and Engineering in 1974"
TL;DR: In this paper, the historical evolution of EB dehydrogenation processes has been summarized by Kearby [21 and others [3] and a detailed overview of EB catalysts can be found in Table 1.
Abstract: Catalyst research for ethylbenzene (EB) dehydrogenation has been interest to many chemical manufacturers because styrene monomer is such a large-volume chemical and a steady growth of styrene markets is predicted. EB is relatively easy to dehydrogenate and the reaction may be effected by a simple thermal gas-phase process as observed by Berthelot in 1869 [l]. However, a much higher selectivity to styrene is obtained by contact catalysts. The historical evolution of EB dehydrogenation processes has been summarized by Kearby [21 and others [3].
220 citations
TL;DR: The modern petrochemical industry relies on several hydrocarbon raw materials: methane, ethylene, propylene, butene, higher olefins, and the aromatics as discussed by the authors.
Abstract: The modern petrochemical industry relies on several hydrocarbon raw materials: methane, ethylene, propylene, butene, higher olefins, and the aromatics. Some of the most important processes that suc...
214 citations
TL;DR: The steady-state flow method has been widely used in the kinetic study of heterogeneous catalysis as mentioned in this paper, and it is a common practice for the investigator to postulate a number of suspected rate models and then to assess these models to verify a optimal one which best fits observed rate data.
Abstract: The steady-state flow method has been widely used in the kinetic study of heterogeneous catalysis. Under the conditions of steady state, all elementary steps in series are progressing at the same rate and hence the measured rates hardly tell the precise kinetic structure, or mechanism, of catalytic reactions which usually consist of several elementary steps including adsorption of reactants, surface reaction, and desorption of products. In the kinetic analyses of any given reactions, it is a common practice for the investigator to postulate a number of suspected rate models and then to assess these models to verify a optimal one which best fits observed rate data. Usually, however, there are quite a large number of plausible rate models even for a rather simple reaction, and it is not easy to determine the most adequate model among others even with the help of mathematical model indentification techniques with a electronic computer. This method is based on the assumption that there is a best mode...
176 citations
TL;DR: In this article, it was shown that many homogeneous catalysts can be converted into heterogeneous ones, retaining the advantages of great activity and selectivity inherent in homogeneity and, at the same time, assuming the ready recovery which is the great advantage of heterogen.
Abstract: For many years, it has been customary to classify catalysts as “homogeneous” or “heterogeneous.” The former commonly operate through the formation of “intermediate compounds,” and the latter, by adsorption of the reactants on the catalyst surface. The line between the two is a fine one, for the distinction between adsorption and compound formation is not at all clear, and seems to be becoming less and less clear as we learn more about adsorption. In recent years, several writers [l-7] have stressed the point that there is a good deal of overlap between homogeneous and heterogeneous catalysis. Experimental evidence supporting this point of view is accumulating, and while we are not prepared to say that there is no distinction, we can say with certainty that many homogeneous catalysts can be converted into heterogeneous ones, retaining the advantages of great activity and selectivity inherent in homogeneity and, at the same time, assuming the ready recovery which is the great advantage of heterogen...
146 citations
Esso1
TL;DR: In this paper, it is shown that the surface of a very small microcrystal is either more or less active than that of a larger crystal, depending on the size of the microcrystals.
Abstract: Supported metal catalysts are widely used because it is possible to prepare them in a highly dispersed form, consisting of very small microcrystals, which provide a maximum available surface area for the catalytic reaction [1]. Superficially, one might expect that the effectiveness of the material as a catalyst would be simply proportional to the surface area. In this case the specific catalytic activity would be independent of the size of the microcrystals. Size-independent specific activity is observed in a number of reactions, such as hydrogenation of benzene on alumina-supported platinum [2]. For other reactions, the specific catalytic activity is dependent on the size of the mircrocrystals. It is possible that the surface of a very small microcrystal is either more or less active than that of a larger crystal. Figure 1 shows the specific activity of the catalyst for deuteration of benzene and for hydrogen exchange with benzene on nickel catalysts [3]. Note that the smaller microcrystals are ...
117 citations
TL;DR: The interaction of methane with metal catalysts has received less attention than that of hydrocarbons containing two or more carbon atoms as mentioned in this paper, but it is interesting because its electronic structure resembles that of a rare gas and it possesses high symmetry and small reactivity.
Abstract: The interaction of methane with metal catalysts has received less attention than that of hydrocarbons containing two or more carbon atoms [1]. Yet methane is interesting because its electronic structure resembles that of a rare gas and it possesses high symmetry and small reactivity. Also, it is the most stable of the alkanes and one of the few thermodynamically stable at room temperature. The temperature at which methane should spontaneously decompose (δG° = 0) is 570°C [2] and its reactions may give valuable information [4].
115 citations
TL;DR: In this article, it is shown that the kinetic rate parameters of a chemical reaction can be predicted from available correlations and the design of equipment is often carried out from first principles, however, there is no method available by which the kinetic rates of a reaction can accurately predict the reaction parameters.
Abstract: A basic requirement in the analysis of catalytic reactors is a rate expression for the reaction concerned In the design of any equipment the equations to be used contain certain basic physical-chemical coefficients whose values must be known In the case of physical operations, these coefficients can usually be predicted from available correlations and the design of equipment is often carried out from first principles But there is no method available by which the kinetic rate parameters of a chemical reaction can be predicted; thus experimental determination of these parameters is unavoidable
86 citations
TL;DR: In this article, the authors focus on one broad type of catalyst deactivation which also happens to be the most common type of deactivation found in practice and propose a review of the literature on this type.
Abstract: Perhaps the most difficult practical problem in the study of catalysis is presented by the loss of catalyst activity during reaction. This very complicated phenomenon is made even more confusing by the wide variety of deactivation phenomena and the lack of systematization in this field of research. Consequently little fundamental work has been done on systems in which the catalyst is subject to deactivation. This review proposes to focus on one broad type of catalyst deactivation which also happens to be the most common type of deactivation found in practice.
80 citations
TL;DR: In this paper, the orthogonal collocation method is used to obtain approximate solutions to the differential equations modeling chemical reactors, which is very often useful in engineering work, where valid approximations are accepted.
Abstract: The orthogonal collocation method is used to obtain approximate solutions to the differential equations modeling chemical reactors. There are two ways to view applications of the orthogonal collocation method. In one view it is a numerical method for which the convergence to the exact answer can be seen as the approximation is refined in successive calculations by using more collocation points, which are similar to grid points in a finite difference method. Another viewpoint considers only the first approximation, which can often be found analytically, and which gives valuable insight to the qualitative behavior of the solution. The answers, however, are of uncertain accuracy, so that the calculation must be refined to obtain useful numbers. However, with experience and appropriate caution, the first approximation is often sufficient and is easy to obtain. Thus it is very often useful in engineering work, where valid approximations are accepted. We present both viewpoints here: we use the first a...
73 citations
TL;DR: A survey of graphite inclusion compounds is given in Table 1 as mentioned in this paper, where the authors define the concentration stage as the ratio of the number of carbon layers to that of reactant layers, and show that a compound of Stage 1 is always the most concentrated in a range of intercalation compounds of the same reactant.
Abstract: Graphite reacts with a large number of substances to give lamellar compounds in which the reactant is present in the form of monolayers separated by one or more carbon layers. The compositions of some of the compounds can differ in the repeat frequency of the reactant layer, and occasionally also in the arrangement of atoms within the reactant layer. The “concentration stage” of a compound is defined as the ratio of the number of carbon layers to that of reactant layers. Thus a compound of Stage 1 is always the most concentrated one in a range of intercalation compounds of the same reactant. A survey of some graphite inclusion compounds is given in Table 1.
59 citations
Esso1
TL;DR: The second Paul H. Emmett Award in Fundamental Catalysis was presented by as mentioned in this paper, with the focus on catalysis by metals, a subject to which the late Professor has contributed extensively.
Abstract: It is a pleasure to receive the second Paul H. Emmett Award in Fundamental Catalysis and to have the opportunity to present this address. The subject, catalysis by metals, is one in which Professor Emmett himself has contributed extensively. His long-standing interest in the iron catalysts for ammonia synthesis, and also his later interest in metal alloy catalysts, are well known.
TL;DR: It is generally accepted nowadays that catalysis occurring at the surface of a metal compound, such as an oxide or a sulfide, can be described in terms of the properties of the metal ions as mentioned in this paper.
Abstract: It is generally accepted nowadays that catalysis occurring at the surface of a metal compound, such as an oxide or a sulfide, can be described in terms of the properties of the. metal ions, surroun...
TL;DR: A large amount of research has recently been devoted to oxidative conversions of hydrocarbons, and many laboratories in various countries are concerned with this problem as discussed by the authors, and many schemes for the catalytic oxidation of olefins and aromatics have been proposed.
Abstract: A large amount of research has recently been devoted to oxidative conversions of hydrocarbons, and many laboratories in various countries are concerned with this problem. This field of catalysis has been extensively studied. The new, particularly spectroscopic, experimental methods provide additional information on the structures of surface compounds formed by interactions of various reactants with the catalyst. The very sensitive chromatographic technique has made possible the detection of multiple oxygen compounds yielded by oxidation of hydrocarbons of various structure so that the possibility of various conversion paths has become evident. Many schemes for the catalytic oxidation of hydrocarbons, particularly of olefins and aromatics, have been proposed. Considerably less extensive was the research on the oxidation of alkanes.
TL;DR: Most heterogeneous catalysts are either supported on some kind of porous material or the catalyst itself is porous as discussed by the authors, and very often the overall chemical reaction rates within these catalyst pellets are determined by a complicated interaction of internal and external transport effects with the intrinsic kinetic rate at the active surface.
Abstract: Most heterogeneous catalysts are either supported on some kind of porous material or the catalyst itself is porous. To satisfy practical constraints such as pressure drop, handling, and separation from products, these catalysts are generally pelletized. Very often the overall chemical reaction rates within these catalyst pellets are determined by a complicated interaction of internal and external transport effects with the intrinsic kinetic rate at the active surface.
TL;DR: In this paper, the electron paramagnetic resonance (EPR) method was used for the study of catalytic processes and free radical intermediates are postulated in catalytic mechanisms.
Abstract: Since many free radical intermediates are postulated in catalytic mechanisms [l] and since many of the commercially important catalysts are supported transition metal compounds [2], the method of electron paramagnetic resonance (EPR) should be a useful tool for the study of catalytic processes.
TL;DR: In this article, it is shown that mass transfer both within and external to the catalyst particles and the analogous effects of heat transport may play an important and even dominant role in the overall conversion scheme.
Abstract: It is well known that in the practical employment of catalysts in commercial reactors, physical processes may play an important and even dominant role in the overall conversion scheme. Such physical processes may include mass transfer both within and external to the catalyst particles and the analogous effects of heat transport. In addition, for packed beds, dispersion of mass and heat in both the axial and radial directions may be important. The intra-particle effects arise because of the significant size of the catalyst particles which in turn is dictated by the requirement that the pressure drop within the reactor shall not be excessive. In practice, catalyst pellets up to about 1 cm in diameter are often employed.
TL;DR: A status report on catalytic reaction engineering can be found in this article, where the authors set forth a more modest and manageable commentary on key areas of the subject to indicate the level of progress, or the lack of it, in areas complementing the catalytic sciences.
Abstract: With the advent of Catalysis Reviews-Science and Engineering, it would seem appropriate that a status report on catalytic reaction engineering be fashioned at this time Rather than present a comprehensive review of the diverse aspects of the general subject, we choose to set forth a more modest and manageable commentary on key areas of the subject to indicate the level of progress, or the lack of it, in areas complementing the catalytic sciences As such, literature citations are merely illustrative, not comprehensive Hopefully our limited comments will inspire experts in each of the various subdisciplines of catalytic reaction engineering to create more profound commentaries for this Journal
TL;DR: Study of the reaction mechanism of the pentose phosphate pathway in rabbit and rat liver cells has re-emphasized the possible usefulness of isotope exchange reactions in understanding the mechanism of action of nature's catalyst.
Abstract: Recent studies from this laboratory [l, 2] on the reaction mechanism of the pentose phosphate pathway in rabbit and rat liver cells have accentuated the role of enzyme-catalyzed exchange reactions as a means by which tracer carbon is relocated in the absence of a net metabolic flux. While this is an intrinsic property of the group transferring enzymes of the pathway and is seen as a deleterious property of 14C for the mapping and quantitation of metabolic pathways, it has re-emphasized the possible usefulness of isotope exchange reactions in understanding the mechanism of action of nature's catalyst.