Ziegler processes

Ziegler process) and telomerization of alkenes to medium chain derivatives for detergents and fats. Both processes operate by insertion of an alkene into AIR bonds. 

The Ziegler process, based on reactions discovered in the 1950s, produces predorninandy linear, primary alcohols having an even number of carbon atoms. The process was commercialized by Continental Oil Company in the United States in 1962, by Condea Petrochemie in West Germany (a joint venture of Continental Oil Company and Deutsche Erdid, A.G.) in 1964, by Ethyl Corporation in the United States in 1965, and by the USSR in 1983. 

Eatty alcohols, prepared from fatty acids or via petrochemical processes, aldol or hydroformylation reactions, or the Ziegler process, react with ammonia or a primary or secondary amine in the presence of a catalyst to form amines (10—12). 

In the mid-1950s a number of new thermoplastics with some very valuable properties beeame available. High-density polyethylenes produced by the Phillips process and the Ziegler process were marketed and these were shortly followed by the discovery and rapid exploitation of polypropylene. These polyolefins soon became large tonnage thermoplastics. Somewhat more specialised materials were the acetal resins, first introduced by Du Pont, and the polycarbonates, developed simultaneously but independently in the United States and Germany. Further developments in high-impact polystyrenes led to the development of ABS polymers. 

Very high molecular weight polyethylenes (A/ in the range 1-6 X 10 ) prepared by the Ziegler process have also become available. As might be expected from consideration of Figure 3.1 these polymers cannot be processed easily in the molten state without decomposition and it is therefore often necessary to process in the rubbery phase. 

The oligomerization of the ethylene proceeds as a ligand reaction in the coordination sphere of the catalyst complex, as the following reaction scheme shows. The reaction course corresponds with the Ziegler process for ethylene polymerization. 

The Ziegler process produces linear alcohols with an even number of carbon atoms and is based on the polymerization of ethylene under catalytic conditions, generally with triethylaluminum as in the Alfol and the Ethyl processes. The distribution of alkyl chains depends on the version of the process employed but the alcohols obtained after fractionation can be equivalent to those obtained from fats and oils or have purpose-made distributions depending on the fractionation conditions. 

The basic process steps in the Ziegler process are the synthesis of the tri-ethylaluminum catalyst, chain growth from an ethylene precursor, oxidation, and finally hydrolysis. 

Ziegler processes are based on co-ordination reactions catalysed by metal alkyl systems. Such reactions were discovered by Karl Ziegler in Germany and developed by G. Natta at Milan in the early 1950s. 

The mechanism of hydrosilation can be rationalized as described by Chalk and Harrod (1 l-lId). In this view, all the chemical changes take place within the coordination sphere of a transition metal. Other reactions of unsaturated molecules are explained in much the same way. Hydrogenation, the oxo-process, and the Ziegler process are important examples. 

CP [Continuous polymerization] A continuous process for making high-density polyethylene, based on the Ziegler process but using a much more active catalyst so that de-ashing (catalyst removal) is not required. Developed by Mitsui Petrochemical Industries and upgraded into its CX process, which was first licensed in 1976. 

One-part solvent-releasing butyl sealant formulation, 22 43t One-part urethane sealants, 22 36-37 One-pass clarifier, 22 61 One-photon absorption, 77 455 One-pot oxidation polymerization, 23 713 One-stage separation plants, 75 840 One-step cameras/processors, 79 276-278 One-step Ziegler process, 77 715-718 One-way memory, of shape-memory alloys, 22 341, 345-346... 

The various steps introduced in the production of alcohols from ethylene are represented in Fig. 1.11. Similar to the production of a-olefins, in the production of alcohols using the Ziegler process, the final product is a mix showing a typical Poisson distribution with alcohols from C4 up to C2s- Alcohols are also obtained from n-paraffin... 

Flexing the operating conditions of the versatile Ziegler process allows the distribution of the plasticizer alcohols (Cg-Ci-o) versus the detergent alcohols (Ci2—Cis) to vary from as low as 15% to as high as 85%. 

This process seems much simpler than the Ziegler process, and you may wonder why it has not crowded Ziegler out. The problem is the olefin feed. Where do you get a ready supply of olefins the right size to feed to the process The answer is you have to malce them, and therein lies the rub. Normal paraffins from petroleum waxes or other chemical processes provide the feedstock to a two-step process, chlorination and dehydrochlorination, which produces an olefin corresponding to the paraffin. 

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