Phillips catalysis

Krauss, H. I. and Xing, Q., Organochromium Species in Phillips Catalysis , in Proc. 2nd International School on Molecular Catalysis Organometallics and Catalysis , Poznan-Kiekrz, Poland, 1995, Abstracts, p. L-9. 

Contrary to the afore mentioned Authors, Chien considering various polyethylene and polypropylene catalytic systems, on the basis of the Thiele modulus criteria (Q 5 for a > 5 and Q 1 for a 1) recently concluded that Ziegler-Natta catalysis is not controlled by diffusion phenomena while Phillips catalysis is. 

Niegisch has made similar observations for a Davison 952 silica gel used in a Phillips catalysis. He found the smallest units of 10—50 nm, which again form clusters of 200—500 nm. 

Spitz R, Florin B, Guyot A Ethylene-hexene-1 copolymers through modified Phillips catalysis, Eur Polym J 15(5) 441—444, 1979. 

These siUca-supported catalysts demonstrate the close connections between catalysis in solutions and catalysis on surfaces, but they are not industrial catalysts. However, siUca is used as a support for chromium complexes, formed either from chromocene or chromium salts, that are industrial catalysts for polymerization of a-olefins (64,65). Supported chromium complex catalysts are used on an enormous scale in the manufacture of linear polyethylene in the Unipol and Phillips processes (see Olefin polymers). The exact stmctures of the surface species are still not known, but it is evident that there is a close analogy linking soluble and supported metal complex catalysts for olefin polymerization. 

Hen egg-white lysozyme catalyzes the hydrolysis of various oligosaccharides, especially those of bacterial cell walls. The elucidation of the X-ray structure of this enzyme by David Phillips and co-workers (Ref. 1) provided the first glimpse of the structure of an enzyme-active site. The determination of the structure of this enzyme with trisaccharide competitive inhibitors and biochemical studies led to a detailed model for lysozyme and its hexa N-acetyl glucoseamine (hexa-NAG) substrate (Fig. 6.1). These studies identified the C-O bond between the D and E residues of the substrate as the bond which is being specifically cleaved by the enzyme and located the residues Glu 37 and Asp 52 as the major catalytic residues. The initial structural studies led to various proposals of how catalysis might take place. Here we consider these proposals and show how to examine their validity by computer modeling approaches. 

Wihnot CM, J Hajdu, MJ Me Pherson, PF Knowles, SEV Phillips (1999) Visualization of dioxygen bound to copper during enzyme catalysis. Science 286 1724-1728. 

L. Guczi, in M. J. Phillips, M. Ternan (eds.) Proceedings of 9th International Congress on Catalysis, Chemical Institute of Canada, Ottawa, 1989, 114. 

Phillips, J. Dumesic, J. A. Review - accepted for publication in Applied Catalysis. 

P. (1988) Proceedings 9th International Congress on Catalysis, Vol. 3 (eds M.). Phillips and M. Ternan), Chemical Instiurte of Canada, Ottawa, ON,... 

The contact process was invented by Phillips in England in 1831 but was not used commercially until many years later. Today 99% of all sulfuric acid is manufactured by this method. It was developed mainly because of the demand for stronger acid. All new contact plants use interpass absorption, also known as double absorption or double catalysis. This process will be described in detail in Fig. 2.3. 

Infrared spectroscopic studies show that hdpe produced by Ziegler-Natta catalysis has about 10 to 14 ethyl groups per 1000 repeating units. However, hope produced by the use of the Phillips catalyst has less branching and fewer ethyl groups. Most of the commercial hope used in the United States is produced by use of the Phillips catalyst. 

ESR Studies of Surface Species. ESR has been applied widely in heterogeneous catalysis as a technique for examining the nature and concentration of possible catalytic sites when a material is activated either chemically or thermally (64, 65, 66). ESR studies on the Phillips polyethylene catalyst, Cr03/Si02, are a classical example of this application (67). The interpretation of such ESR studies is questionable since the chemical changes during activation are not well understood, and the nature of the surface species may have to be assumed. 

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