Fat-hardening

Owing to the discoveries of M. Sabatier a new se has been found for hydrogen, and a vast and ever-rowing industry created, known as " fat hardening . 

In this note the use of hydrogen in the fat hardening industry has been described with particular reference to the conversion of the unsaturated oleic and linoleic fatty acids into stearic acid However, what has been said in regard to diis matter is equally applicable to the conversion of olein and linolein into stearin, cotton-seed and most fish oils being quite easily converted into solid fats. 

Thus, it is seen that the same iron is used continu-isly, and steam and blue water gas are the two regents consumed. Such is the chemical outline of the on Contact process however, in practice, the process somewhat more complex and very much less efficient lan either the Electrolytic process or the Badische ocess, both of which are described at a later stage, nor in the hydrogen produced be regarded as so satisfactory tr some industrial purposes, such as fat hardening, as lat made by the other two processes. 

The chemical composition of the catalyst appears to e somewhat variable, but, as in the case of the catalyst sed in the fat-hardening industry, its physical condition fifects the efficiency of the process. In the patents pro-jcting this process a variety of methods are described >r the preparation of the catalyst, but the following lay be given as representative.—... 

The reactions studied were the catalytic formation of methane from carbon monoxide and hydrogen (according to Sabatier (34), normal pressure), the catalytic hydrogenation of unsaturated hydrocarbons and also of unsaturated fatty acids ( fat hardening according to Normann (35)). Here again, a certain analogy was established between... 

The fatty oil industry has not yet made the same progress in the chemical processing of its products as is the case in the petroleum industry. After the initial success attained in the development of the fat-hardening technique, this industry has remained stationary for many years. However, the chemical modification of fatty oils is of vital importance and the development of modem processes in the fatty oil industry will depend to a large extent on the basic knowledge of its raw materials and the fundamental study of possible chemical transformations. 

There are cases where it is actually desirable to operate under conditions of mass-transport control this is so for example where it is an intermediate product that is wanted fat-hardening is a case in point. More usually, however, one wishes to work under conditions where conversion is as close as possible to 100% and here it is inevitable that mass-transport control will apply, at least at the end of the catalyst bed. The physical structure of the catalyst then becomes of great importance, and much thought and skill is exercised in maximising access of reactants to the active centres. The form of reactor and the appropriate physical form of the catalyst have to be chosen with care. 

Some chemical operations, however, demand a supply of pure hydrogen these include ammonia synthesis and fat-hardening, and so it became necessary to find a way of altering the composition of water-gas to achieve this. Its gaseous components can be brought into equilibrium by the water-gas shift... 

We noted in Chapter 7 the requirement of the chemical industry for large quantities of pure hydrogen for processes such as ammonia synthesis and fat hardening, and that the major route followed is the steam-reforming of alkanes, e.g. 

This catalyst [8a, 25-27] was formulated as a 25% Ni/Si02, typical of those used for fat-hardening and other large-scale hydrogenations. One of the major problems with catalysts of this type arises from the extensive interaction, amounting to compound formation, that occurs between the precursor components during the preparation, and the consequential difficulty of obtaining complete reduction of the nickel. This was a major focus of effort in the study of this catalyst. 

A direct application is the study and optimization of catalyst pretreatment. In industrial practice, catalysts are frequently pretreated using a temperature-programmed technique. Examples are reduction in the fat hardening catalysis and sulphiding in the hydrotreatment of oil fractions in the refinery. 

We focus on heterogeneous catalysis with single and multiple reactant phases, as these are the most common in practice. Examples include environmental catalysis, fat hardening, hydrodesulfurization of oil streams, hydrogenation of fine chemicals, and selective conversions catalyzed by immobilized enzymes or cells in biotechnology. The most popular reactors used in industry for multiphase applications are slurry bubble columns and trickle-bed reactors. They are shovm in Figure 1. 

Unsaturated fats. Hardening of oils. Drying oils... 

Catalysts in which a metal is the active component are, however, pyrophoric after thermal treatment of the metal precursor in a reducing gas flow. Grinding of a reduced catalyst in an inert atmosphere without intermediate exposure to atmospheric air has been performed with nickel fat-hardening catalysts. After the grinding procedure the small catalyst particles are taken up in hardened fat, which protects the nickel against oxidation. The procedure is, however, tedious and cannot be readily executed with the small batches of catalyst usually used in the fine-chemical industry. 

Figure 1 Photograph and Drawing of Norman s Hydrogenation Reactor from 1903 and of the Olwerke Germania Fat Hardening (Hydrogenation) Plant at Emmerich in 1912.

The foundation for the present industry was laid in 1897 when Sabatier and Senderens illustrated the catalytic effect of nickel in vapor-phase hydrogenation reactions. The earliest technical application, bf- hydrogenation was in the reduction of the double bonds between two carbon atoms for the purpose of converting liquid fats into solid fats, or as it is often called, fat hardening. This industry is now very large. 

These are naturally occurring esters of the triol glycerol (propan-1,2,3-triol). A fat is a substance that is solid at room temperature, whereas an oil is liquid. In vegetable oils, the hydrocarbon chains have many double bonds (they are polyunsaturated). Fats, however, tend to have very few, or no double bonds. Removal of most of the double bonds in a vegetable oil, by reaction with hydrogen (hardening), will convert it to a solid fat. Hardened corn oil, for example, is used to make margarine. 

The glyceride esters of the long-chain fatty acids are not strictly speaking hydrocarbons , and the catalytic chemistry and technology of fat hardening is therefore not treated in this work however, the alkyl side-chains behave exactly as... 

This may be an appropriate time to review the metal-catalysed reactions of hydrocarbons. The importance of several major industrial processes which depend on these reactions - petroleum reforming, fat hardening, removal of polyunsaturated molecules from alkene-rich gas streams - has generated a great body of applied and fundamental research, the intensity of which is declining as new challenges appear. This does not of course mean that we have a perfect understanding of hydrocarbon reactions this is not possible, but the decline in the publication rate provides a window of opportunity to review past achievements and the present status of the field. 

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