Hydrogenation processes, fatty alcohol production

The first commercial production of fatty alcohol ia the 1930s employed the sodium reduction process usiug a methyl ester feedstock. The process was used ia plants constmcted up to about 1950, but it was expensive, hazardous, and complex. By about 1960 most of the sodium reduction plants had been replaced by those employing the catalytic hydrogenolysis process. Catalytic hydrogenation processes were investigated as early as the 1930s by a number of workers one of these is described ia reference 26. 

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. 

Since FAS can be produced either from vegetable oil based or petrochemical-based fatty alcohol (Fig. 4.9), both types have been evaluated in a life-cycle analysis with a positive overall result for the natural based product. With vegetable-based fatty alcohol sulfate, the analysis starts with the harvesting of the oil fruits (palm kernels or coconuts) and their processing to isolate the desired plant oil. Subsequent transesterification and hydrogenation of the methyl ester intermediates lead to the fatty alcohols, which are finally sulfated to produce the desired product. Based on this analysis the environmental impact of vegetable oil based fatty alcohol sulfate compared with the petrochemical based product is as follows ... 

The first commercial production of fatty alcohols in the 1930 s employed a sodium reduction process (Bouveault-Blanc) (2). However, the high usage (4 mol/mol alcohol) of expensive sodium soon led to replacement of this method of reduction by catalytic hydrogenation. 

Sodium Reduction Process. In 1909, Beauvault and Blanc discovered the sodium reduction process of manufacturing fatty alcohols from coconut esters. Fatty alcohol plants established in the 1930s used this process. Although the basic process is relatively simple, actual plant operations in handling the reactants and products are much more complex. The hazards of handling metallic sodium is an additional factor that caused this process to gradually lose out to the catalytic hydrogenation process. 

The initial step of the process is the formation of aluminum triethyl from aluminum metal, ethylene and hydrogen. In a second step ethylene is added to the aluminum triethyl causing the carbon chains to grow in increments of two carbon atoms. After the chain growth reaction the aluminum alkyl is oxidized to an aluminum alkoxide. The alkoxide is then hydrolyzed with water, forming fatty alcohols and alumina slurry. The alcohols and the alumina slurry can be separated from each other and processed into the final products. After drying of the slurry the alumina is obtained in the form of a high purity aluminum oxide monohydrate of boehmite or pseudoboehmite structure. 

Fatty alcohols and their derivatives are important in many industrial processes where thQ are used as raw materials for surfactants and lubricants. A fot alcohol is, in general defined as a monohydric aliphatic alcohol with six or more caibon atoms. The annual production of fotty alcohols is over 1 million metric tons. Commercially fotty alcohols are produced by one of three processes the Ziegler process, the Oxo process or ly a high pressure hydrogenation of fot acids or esters. The latter process is the only one process that uses renewable natural fots/oils whereas the two first processes utilize petrochemical... 

Only a few natural sources of fatty alcohols were known at this time. Production on a technical scale could be first realized by the reduction of methyl or butyl esters of fatty acids with metallic sodium after the Bouveault-Blanc process. Nearly simultaneously, the high-pressure hydrogenation of fatty acids to the resulting alcohols was developed by Schrauth. Hence, fatty alcohols were soon available on the market in a price range that made it possible to produce fatty alcohol sulfates for use in detergents. 

Today, natural detergent alcohols are prodnced using processes such as that developed by Davy Process Technology, depicted in Hgnie 1.9, which convert fatty acids into nonacidic intermediate methyl esters and hydrogenates these to alcohols, then separates C12-C14 and C16-C18 product streams. This vapor phase process has been licensed around the world in ten ester hydrogenation plants with a total installed capacity of 350,000 t/year of alcohols. These plants have virtnally no effluents small by-product streams are recycled and consumed within the process, thus they have minimal environmental impact... 

The reduction proceeds selectively without the production of hydrocarbons and isomerization or hydrogenation of double bonds. Extensive safety measures are required due to the large quantity of metallic sodium used. The process was used until the 1950s to produce unsaturated fatty alcohols, especially oleyl alcohol from sperm oil. These alcohols can now be produced by selective catalytic hydrogenation processes using cheap raw materials, and the sodium reduction process is of interest only in special cases. 

The first large-scale hydrogenation plant (Henkel) went into operation in the late 1950s. Previously, unsaturated fatty alcohols could be obtained only by hydrolysis of whale oil. The hydrogenation processes Section 26.7.2.1.2.2 are suitable for the large-scale production of unsaturated fatty alcohols. 

The chemical industry employs hydrogenation to produce a variety of industrial chemicals such as cyclohexane, cyclohexanol, cyclohexanone, fatty alcohols, sorbitol or monomers such as hexa-methyldiamine or 1,6 hexanediol. A number of new hydrogenation processes, such as coal liquefaction and synthetic crude production from bitumen are now undergoing pilot and even demonstration scale developments ... 

The Philippines, a major producer of coconut oil, established its first oleochemical plant of limited capacity in 1967. The plant produced only 3,000 t/yr of coco fatty alcohols. Recent data for the Philippines listed a capacity of 25,0001 of alcohol products from coconut oil by the fatty acid hydrogenation process. Philippinas Kao produced 30,0001 of alcohol products from coconut oil using the methyl ester hydrogenation process. 

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