The Studies On Hydrogenation Of Cottonseed Oil And Crystallization Of Hydrogenated Cottonseed Oil

Cottonseed oil, oil with well plasticity and gas retention, was an excellent base oil ofplastic fat after hydrogenation, however, amounts of trans acids were produced duringhydrogenation. The aim of this study was to get hydrogenated cottonseed oil with lowertrans acids through optimizing cultural technology. Study on crystallization behavior ofhydrogenated cottonseed oil was helpful to improve quality of plastic fat.Hydrogenation reaction was conducted with raw material of refined cottonseed oil,catalyst of nickel. Four factors affecting on iodine of hydrogenated oil was studied in a fixedstirring rate. Adopting single-factor experiments, orthogonal experiments, the suitableconditions to produce plastic fat were as follows: hydrogen pressure0.3Mpa, catalystconcentration1%, reaction time75min, temperature170℃, stirring rate300r/min. In thiscondition, iodine value and trans acids of hydrogenated oil was73.57and23.73%,respectively.Fourteen samples were prepared for studying crystallization behavior of hydrogenatedoil. Iodine value decreased and melting point rised after hydrogenation. Duringhydrogenation, oleic acid and linolelaidic acid decreased after a period of rising, steric acidand elaidic acid increased straightly. The gross of trans acids didn’t nearly changed whenreaction proceeded after ninety minutes’ increasing. The trans acid for the firsthydrogenation was a little more than the other, but no significant differences between them.The percentages of PLL, LLL, etc were greater, decreasing during hydrogenation. The rationof EEE and PEP increased, and POP minished after a period of increase.Crystallization of hydrogenated cottonseed oil was studied by pNMR, DSC, and XRD.The isothermal and non-isothermal crystallization of hydrogenated oil coming from twohydrogenations under6℃,15℃,20℃,25℃,30℃, and at cooling rates of1℃/min,5℃/min,10℃/min,20℃/min, respectively; and their kinetics were analysed using Avramiand Ozawa model, respectively. Isothermal crystallization curve have two kinds ofhyperbolic curves and sigmoidal curves. Induction time was longer when saturating andsupercooling higher, whereas induction time shorter. Non-isothermal crystallization curvesdemonstrated that temperature range were greater as cooling rate got bigger.Avrami model demonstrated that crystallization constant K value was strongly relatedto temperature. Crystallization constant K and isothermal crystallization constant nincreased when supercooling and saturation got bigger, whereas decreased. Ozawa model demonstrated that Crystallization constant k(T) and non-isothermal crystallization constantm have a trend of increase when temperature rised. Comparing to crystallization constant n,non-isothermal crystallization constant m was bigger, at the range of2to8which explainthat crystallization in non-isothermal condition probably nucleated heterogeneously.The form of crystal of hydrogenated cottonseed oil crystallized at15℃wasβ′, andthese forms didn’t change even after45days’ storage, which explain that hydrogenatedcottonseed oil was a excellent base oil of plastic fat because of their fine crystallizationfeatures.