Hydrogenation of fats and oils

SOURCE From Patterson, Hydrogenation of Fats and Oils, Applied Science Pubbsbers, 1983. 

In the industrial scale of hydrogenation of fats and oils, the most frequently used catalysts are Ni based. The 20-30% Ni is supported on silica. When partial hydrogenation is needed, the temperature applied is between 140 and 200 °C and the pressure between 4 and 10 bar. The total hydrogenation requires higher temperature and pressure (200 °C, 20 bar). Nickel is not a perfect catalyst due to its relative low activity and also due to the formation of Ni-soaps. Recently, a colloidal Pd catalyst was applied successfully in a two-phase system for this type of hydrogenation, at room temperature and atmospheric pressure. The complete conversion of multiunsaturated compounds could be achieved during 15-45 minutes. In dimethylformamide as the second phase solvent, 92% monoene yield with a 70/30 cis/trans ratio could be produced48. 

Table 3.3 gives the total uses of hydrogen. Ammonia production is by far the most important application, followed by methanol manufacture. Hydrogenations in petroleum refineries are an important use. Many other industries utilize hydrogen. Miscellaneous uses include hydrogenation of fats and oils in the food industry, reduction of the oxides of metals to the free metals, pure hydrogen chloride manufacture, and liquid hydrogen as rocket fuel. 

The final element of the hydrophobe which can be manipulated is the cis/trans ratio of the unsaturated hydrocarbon fragments. Natural tallow has a cis/trans ratio of about 8-20 [39]. Metal catalyzed hydrogenation of fats and oils results in the reduction of the cis/trans ratio and an increase in the melting point of the oil when compared to a material of similar iodine value and a higher cis/trans ratio [40]. For concentrated fabric softeners, high cis/trans ratios are preferred to reduce the likelihood of gel formation in the final product or during processing [24, 40-42]. 

Poisoning is not always bad. There are situations where a catalyst is intentionally poisoned to decrease activity towards an undesirable reaction. In the hydro-desulfurization and -demetallization of a petroleum feedstock the catalyst is presulfided prior to introducing the feed to decrease its activity and minimize cracking reactions that will produce unwanted gases. Another is the use of ammonia to slightly poison a Pt catalyst used in the hydrogenation of fats and oils to decrease undesirable oversaturation. 

The hydrogenation of fats and oils is a very old technology. It was invented in... 

Hydrogenation of Fats and Oils at Supercritical Conditions Magnus Harroda and PoulMellerb... 

Ever since W. Normann in the beginning of the century invented his process for hydrogenation of fats and oils, it has mainly been performed in the original way, i.e. in a batch reactor where the oil, hydrogen and the catalyst as a slurry are mixed intensively. Alternatively, the loop reactor by Buss AG and some continuous systems have been in operation. 

H.B. W. Patterson. Hydrogenation of Fats and Oils. Applied Science Publishers, London, 1983. R.T. Donald. In M.V. Twigg (ed.), The Catalyst Handbook. Manson, London, 1996, pp. 490-503. 

Sudah, O.S. Chester, A.W. Kowalski, J.A. Beeckman, J.W Muzzio, F.J. Quantitative characterization of mixing processes in rotary cal-ciners. Powder Technol. 2002, 126 (2), 166-173. Delmon, B. Formation of final catalyst. In Handbook of Heterogeneous Catalysis Ertl, G., Knozinger, H., Weitkamp, J., Eds. Wiley-VCH Weinheim, Germany, 1997 Vol. 1, 264-286. Patterson, H.B.W. Hydrogenation of Fats and Oils Theory and Practice AOCS Press Champaign, IL, 1994. 

Hydrogenation of fats and oils in the food industry, use of hydrogen in glass manufacture, and in cutting and welding further illustrate the broad spectrum of applications. 

Formation of the high-melting unsaturated fats or isomerization accompanies hydrogenation and appears to be in proportion to the selectivity of the reaction. Therefore, compromises must be made between selectivity and isomer formation when determining the best hydrogenation conditions for the various basestocks. Control of the operating variables that affect the hydrogenation of fats and oils is necessary to produce the desired product functionality (Calsicat, 1992). 

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