Manufacturing processes Ziegler process

Ziegler-Natta catalysts play a dominant role in polyolefins manufacture. More than 50 million tonnes per annum of polyethylene and polypropylene are now produced by means of Ziegler-Natta catalysis. Since the first discoveries, more than 50 years ago, many breakthroughs and innovations have been made in catalyst and process chemistry and technology, leading to ever more efficient manufacturing processes, and also to increasing control over polymer structure and properties. 

Barriers to entry into the pseudocommodity business include all the barriers for commodities plus the all-important customer know-how. Lack of technical expertise and patent protection can be formidable barriers to potential producers of a pseudocommodity. Du Pont was the sole producer of nylon from 1939 to 1951. Barriers to entry were removed under threat of government antitrust action in 1951, with the licensing of Chemstrand, which later became part of Monsanto. Since then a number of companies have entered the nylon business. Technical know-how and patent protection played a major role in both high- and low-pressure polyethylene manufacture in the years shortly after World War II. ICI developed polyethylene, but Union Carbide had a superior high-pressure process. Ziegler, Du Pont, and Phillips Petroleum all developed low-pressure processes, which they subsequently licensed to other manufacturers. Many pseudocommodities eventually become commodities by the diffusion of technology, standardization of the product, and the entry of many firms into the business. 

The CONDEA group operates two different types of processes for the manufacture of alkoxide derived alumians and related products, the Ziegler-ALFOL process and CONDEA s On-Purpose Process. The Ziegler process is a co-production process of linear fatty alcohols and alumina, using aluminum organic compounds as intermediates, CONDEA s own On-Purpose technology is based on the formation of aluminum alkoxide from aluminum metal and alcohol. In both processes the formation of alumina is achieved by hydrolysis of aluminum alcoholates with water. 

Natta process /nat-a/ A method for the manufacture of isotactic polypropene using Ziegler catalysts. The process is named for the Italian chemist Giulio Natta (1903-79). See also addition polymerization Ziegler process. 

Phillips process A method for the manufacture of high-density polyethene using a catalyst of chromium(III) oxide on a promoter of silica and alumina. The reaction conditions are 150°C and 30 atm pressure. See also Ziegler process. 

Ziegler process /zee-gler/ A method for the manufacture of high-density poly-ethene using a catalyst of titanium(IV]] chloride and triethyl aluminum (A1(C2H5)3) under slight pressure. The mechanism involves formation of titanium alkyls... 

Future Developments. Current developments are mainly in the field of catalyst improvement, both of conventional Ziegler-Natta catalysts and of single-site catalyst. These developments will mainly influence the properties of the polymer product rather than the manufacturing process. 

In 1954 Hoechst was the first manufacturer of HDPE by Ziegler process, followed by Hiils, Riihrchemie, Montecatini, Shell, Mitsui, Dow, Esso, Gulf, Hercules, Koppers, Monsanto, and Union Carbide. In 1957, Hercules introduced... 

Most polyolefin manufacturing processes today utilize conventional heterogeneous Ziegler-Natta catalysts. Several types of these Ziegler-Natta catalysts are stereospecific, i.e. the insertion of asymmetric monomers into the growing polymer chain in a given orientation is favored over all other possible orientations, leading to the production of isotactic... 

Primary alcohols are the second most important class of detergent feedstocks after alkylbenzenes. They are produced either by the catalytic hydrogenation of methyl esters or fatty acids derived from oils and fats e.g. coconut oil or tallow, or from synthetic sources. Alcohols manufactured from Ziegler type processes produce even-numbered chain length primary alcohols. The basic process steps are synthesis of the triethylaluminium catalyst, chain growA from an ethylene precursor, oxidation and finally hydrolysis. 

As is well known, polyacetylene can be manufactured by various processes using dilTerent catalysts. The most common method is that of Shirakawa [16,17], in which polymerization of acetylene takes place on a Ziegler catalyst. It has been shown in a large number of polymerization tests that the quality of the catalyst depends strongly on the preparation conditions [11]. 

The melting temperature, extent of crystallinity, modulus, and mechanical behavior depend on the method of manufacture and the addition of comonomers, as well as overall molecular weight. Polyethylene is manufactured by several major processes (1,2) The high-pressure, free-radical polymerization, the Ziegler process, and the newer metallocene-catalyzed polymers and the metallocene-Ziegler processes see Table 14.2. 

General discussions on the preparation and properties of PVC will be found in such references as 1, 4, 5, and 22-24. The manufacture, processing, stabilization, and applications of PVC are also discussed in references 4 and 25-32. A review of the history of ionic and Ziegler catalysis polymerization of vinyl chloride is found in Feldman [33] and Yamazaki [34]... 

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