Ziegler alcohols production

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. 

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. 

In the late 1970s it became apparent that the existing Ziegler-alumina capacity would not be sufficient to serve the growing needs of the markets, in particular of the catalytic market. This led to the development of the so-called On-Purpose Alumina Process by CONDEA (figure 4), a process which basically copies the chemistry of the Ziegler-process related to the formation of boehmite alumina, but which has not linkage to alcohol production[5]. 

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. 

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. 

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). 

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). 

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... 

When ethylene reacts with triethyl- or tripropylaluminum, multiple carbometa-lation takes place, resulting in the formation of oligomers.509 Oxidation of the products followed by hydrolysis yields alcohols, whereas displacement reaction produces terminal alkenes that are of commercial importance.510 Transition-metal compounds promote the addition to form polymers (Ziegler-Natta polymerization see Section 13.2.4). 

Fundamental work on organoaluminum chemistry by Prof. Karl Ziegler and co-workers at the Max Planck Institute provided the basis for a commercial synthesis of even-carbon-numbered straight chain primary alcohols. These alcohols are identical with products derived from naturally occurring fats. In this process, ethylene is reacted with aluminum triethyl to form a higher aikylaluminum which then is oxidized and hydrolyzed to give the corresponding alcohols. 

Pour point, viscosity, cloud point, wetting power and foam properties, being important advantages of SAE, are presented here in comparison with other commercial products derived from primary alcohols (Ziegler and Oxo) or nonylphenol (branched chain). 

The remaining 30 percent of 1-butene is divided among several uses. About 10-15 percent of the 1-butene is polymerized in the presence of a Ziegler-type catalyst to produce polybutene-1 resin. The markets for this resin are pipe, specialty films, and polymer alloys. Approximately the same volume of 1-butene is reacted with synthesis gas in an oxo reaction to produce valeraldehydes. These C5 aldehydes are then hydrogenated to amyl alcohols or oxidized to valeric acid. Amyl alcohols are consumed in the production of lube oil additives and amyl acetate and in solvent uses. Valeric acid goes into lubricant base stocks and specialty chemicals. 

Fig. 36.21. Ziegler process for production of synthetic fatty alcohols.

DuPont and Dow use solution polymerization technology to produce LLDPE resins. The process is based on continuous polymerization of ethylene with 1-octene in cyclohexane at about 250°C and 1200 psi. The catalyst is again Ziegler type. Residence time is of the order of several minutes. The catalyst is deactivated by treatment with an alcohol or complexing agent such as acetyl-acetone, and adsorbed on a silaceous adsorbent before stripping the solvent. The Stamicarbon (Dutch State mines) process is similar to the DuPont process, and it uses a short-residence-time solution process for HDPE production. 

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