Heterogeneous and homogeneous

Integrating ohemistry and ohemioal engineering of industrial prooesses, homogeneous and heterogeneous oatalysis. Somorjai G A 1994 Introduction to Surface Chemistry and Catalysis (New York Wiley)... 

Mitsui Toatsu Chemical, Inc. disclosed a similar process usiag Raney copper (74) shortiy after the discovery at Dow, and BASF came out with a variation of the copper catalyst ia 1974 (75). Siace 1971 several hundred patents have shown modifications and improvements to this technology, both homogeneous and heterogeneous, and reviews of these processes have been pubHshed (76). Nalco Chemical Company has patented a process based essentially on Raney copper catalyst (77) ia both slurry and fixed-bed reactors and produces acrylamide monomer mainly for internal uses. Other producers ia Europe, besides Dow and American Cyanamid, iaclude AUied CoUoids and Stockhausen, who are beheved to use processes similar to the Raney copper technology of Mitsui Toatsu, and all have captive uses. Acrylamide is also produced ia large quantities ia Japan. Mitsui Toatsu and Mitsubishi are the largest producers, and both are beheved to use Raney copper catalysts ia a fixed bed reactor and to sell iato the merchant market. 

Chromium compounds decompose primary and secondary hydroperoxides to the corresponding carbonyl compounds, both homogeneously and heterogeneously (187—191). The mechanism of chromium catalyst interaction with hydroperoxides may involve generation of hexavalent chromium in the form of an alkyl chromate, which decomposes heterolyticaHy to give ketone (192). The oxidation of alcohol intermediates may also proceed through chromate ester intermediates (193). Therefore, chromium catalysis tends to increase the ketone alcohol ratio in the product (194,195). 

Homogeneous and heterogenous catalysts which selectively or partially hydrogenate fatty amines have been developed (50). Selective hydrogenation of cis and trans isomers, and partial hydrogenation of polyunsaturated moieties, such as linoleic and linolenic to oleic, is possible. 

R. A. Sheldon and J. K. Kochi, Metal-Cataly d Oxidations of Organic Compounds, Academic Press, Inc., New York, 1981. Mechanistic principles and synthetic methodology for homogeneous and heterogeneous metal-containing oxidation catalysts, many of which are coordination compounds, are discussed. 

Both homogeneous and heterogeneous mechanisms requite relatively high supersaturation, and they exhibit a high order dependence on supersaturation. These factors often lead to production of excessive fines ia systems where primary aucleatioa mechanisms are important. The classical theoretical treatment of primary nucleation results ia the expressioa (5) ... 

Fig. 21. A selection of feasible residue curve maps for ternary heterogeneous mixtures where I represents homogeneous and heterogeneous...

Clearly, these groupings are not mutually exclusive. The chief distinctions are between homogeneous and heterogeneous reactions and between batch and flow reactions. These distinctions most influence the choice of equipment, operating conditions, and methods of design. 

If we compare eqns (7.11) and (7.3) we see that the expressions for the critical radius are identical for both homogeneous and heterogeneous nucleation. But the expressions for the volume of the critical nucleus are not volume is... 

The maximum statistical fluctuation of 10 atoms is the same in both homogeneous and heterogeneous nucleation. If Q is the volume occupied by one atom in the nucleus then we can easily see that... 

Nucleation of solids from liquids critical radius for homogeneous and heterogeneous nucleation... 

Homogeneous and heterogeneous catalytic activation (in the dark and in the light) of cyclic 1,2-diazenes 97SL1335. 

Biphasic catalysis in a liquid-liquid system is an ideal approach through which to combine the advantages of both homogeneous and heterogeneous catalysis. The reaction mixture consists of two immiscible solvents. Only one phase contains the catalyst, allowing easy product separation by simple decantation. The catalyst phase can be recycled without any further treatment. However, the right combination of catalyst, catalyst solvent, and product is crucial for the success of biphasic catalysis [22]. The catalyst solvent has to provide excellent solubility for the catalyst complex without competing with the reaction substrate for the free coordination sites at the catalytic center. 

However, research into transition metal catalysis in ionic liquids should not focus only on the question of how to make some specific products more economical or ecological by use of a new solvent and, presumably, a new multiphasic process. Since it bridges the gap between homogeneous and heterogeneous catalysis, in a novel and highly attractive manner, the application of ionic liquids in transition metal catalysis gives access to some much more fundamental and conceptual questions for basic research. 

In comparison with traditional biphasic catalysis using water, fluorous phases, or polar organic solvents, transition metal catalysis in ionic liquids represents a new and advanced way to combine the specific advantages of homogeneous and heterogeneous catalysis. In many applications, the use of a defined transition metal complex immobilized on a ionic liquid support has already shown its unique potential. Many more successful examples - mainly in fine chemical synthesis - can be expected in the future as our loiowledge of ionic liquids and their interactions with transition metal complexes increases. 

B. C. Childress, Properties of homogeneous and heterogeneous polyolefins Metallocene catalyzed versus Ziegler-Natta catalyzed resins, MetCon 94 Proceedings, USA, May 1994. 

Table 5 Properties of VLDPEs Prepared with Homogeneous and Heterogeneous Catalyst System [8]...

Pourbaix has classified the various equilibria that occur in aqueous solution into homogeneous and heterogeneous, and has subdivided them according to whether the equilibria involve electrons and/or hydrogen ions. The general equation for a half reaction is... 

Table 10. Thermodynamic parameters of the PNPV hydrolyses in the homogeneous and heterogeneous systems at 25 °C147 ...

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