Ziegler alcohols

Oleochemical alcohols are primary, even carbon-numbered structures with a high linearity (>95%), while the petrochemical derivatives can be even or odd numbered, and depending on the process, their linearity can be as high as the oleochemicals (Ziegler alcohols) or can exhibit variable branching (30% modified 0X0-60% standard OXO). 

A detailed discussion on surfactants from secondary alcohols which are relatively little known in the U.S. is included, together with a review of linear alcohol processes (Oxo and Ziegler) and detergent applications of the Ziegler alcohols. Also covered is a discussion of the revolutionary rhodium oxo process which has already resulted in a number of new plants—announced, under construction, or in operation, worldwide—for the manufacture of n-butanol and 2-ethylhexanol. Applications of these alcohols are also discussed. 

Synthetic fatty alcohols fall into three broad categories and are manufactured from two basic raw materials—ethylene and n-paraffins. One group is secondary alcohols which are prepared by oxidation of n-paraffins in the presence of boric acid. A second group consists of oxo alcohols manufactured by hydroformylation of linear olefins which are derived from either n-paraffins or ethylene. Both of these alcohol types are discussed in separate chapters. The last group is Ziegler alcohols which are prepared from ethylene and are the primary subject of this chapter. 

Secondary alcohols are much different chemically than primary alcohols, such as natural alcohols. In addition, commercial secondary alcohols are prepared from both even and odd carbon-numbered n-paraffins and thus contain both even and odd carbon-numbered alcohols. Oxo alcohols are primary alcohols, as are natural alcohols. However, oxo alcohols contain from twenty to sixty percent branched chain alcohols and also contain both even and odd carbon-numbered homologs. Ziegler alcohols are very similar to natural alcohols. They are primary alcohols and are a mixture of only even carbon-numbered homologs. The major differences between Ziegler and natural alcohols are trace impurities present and the range of synthetic products, C -C30, available. 

There are four basic parts of a Ziegler alcohol process. 

Synthesis of triethylaluminum from aluminum, hydrogen, and ethylene is the first segment of a Ziegler alcohol process. It can be carried out in a single step, but normally is accomplished on a commercial scale in two stages with recycle of two-thirds of the trialkylaluminum product. 

Ethyl s version of the Ziegler alcohol process has been modified in order to control the product alcohol distribution. Whereas the Conoco ALFOL alcohol process affords the full range of alcohols, C2-C3o, in a Poisson distribution, Ethyl s product distribution can be modified, for example, as shown in Figure 3 to give carbon number distributions to fit the needs of the market. 

Oleochemical feedstocks and Ziegler alcohols are linear. Shell s SHOP process produces alcohols with approximately 20% predominantly methyl-branching, while other OXO-type alcohols contain approximately 40-50% predominantly methyl-branching. Alkylphe-nols and alcohols based on oligomerized alkylenes are generally highly branched. 

Ziegler Alcohol Processes. Two processes for the production of synthetic fatty alcohols are based on the work of Ziegler on organic aluminum compounds the Alfol process, developed by Conoco and Ethyl Corporation s Epal process. Fatty alcohols synthesized by these processes are structurally similar to natural fatty alcohols and are thus ideal substitutes for natural products. 

Especially in the range of Cg-Ci3 the 0x0 route holds the dominating position since the other routes, like the aldol route starting from acetaldehyde, the hydrogenation of fatty acid esters or the Ziegler alcohol route, can hardly compete pricewise [342, 899]. 

With respect to their biodegradability and their toxicity values, the Oxo alcohols or their ethoxylates, as well as the Ziegler alcohol derivatives, meet the legislation in force in the Federal Republic of Germany and in the countries of the EEC. 

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. 

Eig. 1. Ziegler ethylene chain growth. Theoretical (Poisson) distribution of primary alcohols at ( ) 2.5, (- -... 

Fig. 2. Estimated primary alcohol distributions for (H) Ethyl Corporation-modified Ziegler and (+) Vista Corporation Ziegler, at 4.0 moles ethylene per...

Environmental Considerations. Environmental problems in Ziegler chemistry alcohol processes are not severe. A small quantity of aluminum alkyl wastes is usually produced and represents the most significant disposal problem. It can be handled by controlled hydrolysis and separate disposal of the aqueous and organic streams. Organic by-products produced in chain growth and hydrolysis can be cleanly burned. Wastewater streams must be monitored for dissolved carbon, such as short-chain alcohols, and treated conventionally when necessary. 

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). 

The principal iadustrial production route used to prepare fatty amines is the hydrogenation of nitriles, a route which has been used since the 1940s. Commercial preparation of fatty amines from fatty alcohols is a fairly new process, created around 1970, which utilizes petrochemical technology, Ziegler or Oxo processes, and feedstock. 

Although the Ziegler reaction provides a more direct method for produciag primary alcohols, aluminum alkyl chemistry requires special handling and is fairly cosdy. The by-product aluminum salts usuaUy require some treatment for disposal (115). 

Alternatively, the intermediate acetaldehyde (qv) for this process was obtained from ethylene by the Wacker process (9). A small amount of -butyl alcohol is produced in the United States by the Ziegler-Natta chain growth reaction from ethylene [74-85-1] (10). 

Factors affecting laboratory polymerisation of the monomer have been discussed" and these indicate that a Ziegler-Natta catalyst system of violet TiCl3 and diethyl aluminium chloride should be used to react the monomer in a hydrocarbon diluent at atmospheric pressure and at 30-60°C. One of the aims is to get a relatively coarse slurry from which may be washed foreign material such as catalyst residues, using for example methyl alcohol. For commercial materials these washed polymers are then dried and compounded with an antioxidant and if required other additives such as pigments. 

Linear alcohols used for the production of ethoxylates are produced by the oligomerization of ethylene using Ziegler catalysts or by the Oxo reaction using alpha olefins. 

Oligomerization of ethylene using a Ziegler catalyst produces unbranched alpha olefins in the C12-C16 range by an insertion mechanism. A similar reaction using triethylaluminum produces linear alcohols for the production of biodegradable detergents. 

Linear alcohols (C12-C26) are important chemicals for producing various compounds such as plasticizers, detergents, and solvents. The production of linear alcohols by the hydroformylation (Oxo reaction) of alpha olefins followed by hydrogenation is discussed in Chapter 5. They are also produced by the oligomerization of ethylene using aluminum alkyls (Ziegler catalysts). 

Olefin polymerization by catalysts based on transition metal halogenides is usually designated as coordinated anionic, after Natta (194). It is believed that the active metal-carbon bond in Ziegler-Natta catalysts is polarized following the type M+ - C. The polarization of the active metal-carbon bond should influence the route of its decomposition by some compounds ( polar-type inhibitors), e.g. by alcohols. When studying polymerization by Ziegler-Natta catalysts tritiated alcohols were used in many works to determine the number of metal-polymer bonds. However, as it was noted above (see Section IV), in two-component systems the polarization of the active bond cannot be judged by the results of the treatment of the system by alcohol, as the radioactivity of the polymer thus obtained results mainly from the decomposition of the aluminum-polymer bonds. 

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