Ethylene heterogeneous oxidation

Phillips (1) A process for polymerizing ethylene and other linear olefins and di-olefins to make linear polymers. This is a liquid-phase process, operated in a hydrocarbon solvent at an intermediate pressure, using a heterogeneous oxide catalyst such as chromia on silica/ alumina. Developed in the 1950s by the Phillips Petroleum Company, Bartlesville, OK, and first commercialized at its plant in Pasadena, TX. In 1991, 77 reaction fines were either operating or under construction worldwide, accounting for 34 percent of worldwide capacity for linear polyethylene. 

Heterogeneous oxidative processes operate at high temperatures (250-450 6C) and are useful for the synthesis of acrolein and acrylic acid from propylene over bismuth molybdate catalysts, the synthesis of maleic and phthalic anhydrides from the oxidation of benzene (or C4 compounds) and naphthalene (or o-xylene) respectively over vanadium oxide,101 arid the synthesis of ethylene oxide from ethylene over silver catalysts.102... 

For long time, Pd has been used mainly as a heterogeneous catalyst for the hydrogenation of unsaturated bonds. A revolution in Pd chemistry occurred with the development of homogeneous Pd catalysts. The first example was the invention of the Wacker process in 1959, by which ethylene is oxidized to acetaldehyde using PdCl2 and CuCl2 as catalysts in aqueous solution (eq. 1.10) [13]. 

Volpe, A. F., Weinberg, W. H., Woo, L., Zysk, J., Combinatorial heterogeneous catalysis oxidative dehydrogenation of ethane to ethylene, selective oxidation of ethane to acetic acid, and selective ammonoxidation of propane to acrylonitrile, Top. Catal. 2003, 23, 65-79. 

A rather interesting application of zeolite-based alkene oxidation catalysis has been demonstrated by Japanese workers (46, 47). In particular, a Pd2 +, Cu2 +Y zeolite was shown to be an active and stable heterogeneous oxidation catalyst which is analogous to the well-known homogeneous Wacker catalyst system containing PdCl2 and CuCl2 (48). Under Wacker conditions (i.e., alkene/02/H20) the zeolite Y catalyst was shown to convert ethylene to acetaldehyde and propylene to acetone with selectivities in excess of 90% with C02 as the major by-product. 

Poly(ethylene oxide) [25322-68-3] (PEO) is a water-soluble, thermoplastic polymer produced by the heterogeneous polymerization of ethylene oxide. The white, free-flowing resins are characterized by the following stmctural formula ... 

Heterogeneous Catalytic Polymerization. The preparation of polymers of ethylene oxide with molecular weights greater than 100,000 was first reported in 1933. The polymer was produced by placing ethylene oxide in contact with an alkaline-earth oxide for extended periods (61). In the 1950s, the low yield and low polymerization rates of the eady work were improved upon by the use of alkaline-earth carbonates as the catalysts (62). 

Some generalizations that pertain are (1) Terminal olefins are more rapidly reduced than internal olefins (2) conjugated olefins are not reduced at 1 atmosphere (3) ethylene is not hydrogenated. Rates of reduction compare favorably with those obtained by heterogeneous catalysts such as Raney nickel or platinim oxide. In fact, the hydrogenation of some olefins may be so rapid that the temperature of the solution (benzene) is raised to the boiling point. 

Ethylene oxide is produced by a heterogeneous catalyzed gas phase oxidation of ethylene with pure oxygen at temperatures of 240-290°C and 5-25 bar [63] ... 

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