Catalysts chemistry

Catalytic Cracking Catalysts, Chemistry, and Kinetics, Bohdan W. 

The diversity of catalyst chemistry and of process type makes it impossible to generalize as to what constitues a better catalyst, except to say that it is one which leads to products that are cheaper or better, or both. In many cases this is likely to be a result of greater selectivity rather than activity, but in single pathway reactions activity, and also the pattern of its change with time, becomes all important. The better catalyst can only therefore be defined in terms of the detailed context of the process for which an improvement is sought. 

T. H. Tsai, J. W. Lane, and C. S. Lin Temperature-Programmed Reduction for Solid Materials Characterization, Alan Jones and Brian McNichol Catalytic Cracking Catalysts, Chemistry, and Kinetics,... 

The refinery will evolve to meet the market (and so, the environmental) needs. Some characteristics are easy to foresee versatility, integration from resources to final user ( well-to-wheels), intensive incorporation of computing tools (integrated and predictive modeling at all levels feedstock-process-product), large dynamic incorporation of new catalysts, chemistry driven , fast incorporation of emerging knowledge and last, but most important, environmental preservation and safe operation. 

The past several years have seen renewed interest in the catalyst chemistry of the water gas shift reaction (WGSR, Eq. 1). 

Wojciechowski, B.W., and Corma, A., Catalytic Cracking—Catalysts, Chemistry, and Kinetics. Marcel Dekker, New York, 1986, p. 5. 

Catalysts The major problem with obtaining rate expressions is that most interesting processes employ catalysts to attain high rates and selectivities, and catalytic kinetics depend sensitively on the details of the catalyst chemistry. Aspects such as promoters, poisons, activation, and deactivation play crucial roles in deterrriining catalyst performance. With catalytic processes we expect complex rate expressions and fractional orders of reaction. This was the subject of Chapter 7. 

Lewis bound form with a strong band at 1440 cm together with a weak 1490cm band. This implies that the Bronsted acidity is associated with the strongly bound water and as this water is removed the pyridine becomes coordinated to a Lewis bound site either nearby or at the undercoordinated A1 site produced by the removal of surface bound water. This transformation of Bronsted to Lewis acid centres is well established in catalyst chemistry as the sample... 

Except for the modification of (58) in reactions (51) and (52), the scheme of (49)—(54) appears to apply to catalytic systems containing Ru(CO)5 in carboxylic acids and a variety of other polar and nonpolar solvents. As described in the next section, introduction of ionic promoters brings about significant changes in the catalyst chemistry. 

In little more than half of the 25 years covered by this symposium, catalytic cracking has been developed from its first acceptance to a major industrial process. It has served to increase the amount and octane rating of gasoline and the amounts of valuable C3 and C gas components obtainable from petroleum feed stocks over those from thermal cracking alone. It is therefore of interest to seek an explanation of the nature of the products obtained in catalytic cracking in terms of the hydrocarbon and catalyst chemistry which has been developed within the past 25 years. 

The main benefits of metallocene catalysts in comparison to the conventional Ziegler-Natta catalysts are well-defined microstructures, high activity, narrow molar mass distribution and the possibility of tailor-made polyolefins. The advantages in metallocene catalyst chemistry offer a promising novel... 

C to form the dinuclear (butadienyl)zirconium system 120. Treatment with B(C6F5)3 leads to the formation of a mono-addition product (121), even in the presence of excess borane. Complex 121 (Scheme 40) shows only a marginal ethene polymerization activity. This led to the notion that such formation of dimeric zirconium complexes might represent desactivation pathways in homogeneous Ziegler-Natta catalyst chemistry.125... 

In this lecture, the development of the MTG process will be reviewed. First, the unique aspects of MTG — the catalyst, chemistry, and its special reactor design aspects — will be discussed. Next, the choices for the conversion system will be presented along with the dual-pronged strategy for development of both the fixed- and fluid bed processes. Finally, our future development plans for this general area of technology will be highlighted. 

Wojciechowski B.W.and Corma A., Catalytic Cracking Catalysts, Chemistry and Kinetics, Chemical Industries/25, Marcel Dekker, Inc. (1986)... 

This process produces a wide melt index range by applying innovative catalyst chemistry combined with a sophisticated polymerization process. An all-round catalyst and simple polymerization operation provide easy product changeover that reduces transition time and yields negligible off-spec product from the transition. Mitsui has also developed new catalyst that contributes better morphology of the polymer powder and ethylene consumption. 

Description The CX process offers products having bimodal molecular-weight distribution, where width is freely and easily controlled by adjusting the reactor arrangement without changing the catalyst system. This process produces a wide melt index range. Innovative catalyst chemistry is combined with a sophisticated polymerization process. The control system allows the plant to operate very stably,... 

Y. Uemichi, Y. Kashiwaya, A. Ayame and H. Kanoh. Formation of aromatic hydrocarbons in degradation of polyethylene over activated carbon catalyst, Chemistry Letters, 41-44 (1984). 

In order to solve these problems, interdisciplinary contribution and cooperation of scientists in the fields covering catalyst chemistry, organic chemistry, polymer science, and materials science are indispensable. 

A simple example illustrates the setup An engineer needs to add 3 gal of an organic liquid to a 10-gal reactor over 90 min (0.0333 gpm). The organic is saturated with hydrochloric acid and contains a significant amount of a partially dissolved Lewis-acid catalyst [chemistry buffs will remember that, in 1923, G. N. Lewis introduced the useful concept that any acceptor of an electron pair is an acid, and an electron donor is a base]. 

Tomoaki Minowa, Tomoko Ogi, Shin-ya Yokoyama. (1995), Hydrogen Production from Wet Cellulose by Low Temperature Gasification Using a Reduced Nickel Catalyst. Chemistry Letters, 937-938... 

Alvaro, M., Cardin, D.F., Colqhoun, H.M., Garcia, H., Gilbert, A., Lay, A.K., and Thorpe, J.H. 2005. Complete filling of zeolite frameworks with polyalkynes formed in situ by transition-metal ion catalysts. Chemistry of Materials 17, 2546-2551. 

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