Study On Process And Mechanism Of Oil Bleaching

Oil bleaching system is very complicated. The process of bleaching and the quality of bleached oil can be affected by many kinds of causes, such as the physic-chemistry characters of the minim-components, the adsobents'composition and structure,and the operation circumstances. Bases on the changing rules of many kinds of minim-components in the bleaching system,this paper studied systemically on the adsorption thermodynamics.This paper also investigated primarily on the adsorption kinetics. The adsorption rules of minim-components on the attapulgite during the bleaching process were advanced .Main original conclusions are shown as follows:(1) Chorophyll,carotenoid, phosphortides, FFA, primary and hypooxide could be adsorbed during the bleaching process. There also exist balance or the changing rules between adsorption and catalysis. The results showed that the best condition of bleaching is 30min,110℃and 1% (/oil weighty) clay. Under this condition, the adsorbents has the best effect on the minim-components which mainly composes of coloring matters, at the same time, the oxidation and decomposition degrees can be kept under the lower level.(2)Oil bleaching system attributes to the solid-liquid diluted- solution adsorption system. Its adsorption isotherm on the different kinds of adsorbents presents the shape of"L", which indicates that the polarity of surface of attapulgite are more similar to the polarity of colors, and the triglyceride has not strong competitive adsorption to the surface of adsorbents. This paper investigated and compared many kinds of adsorption isotherm caused by different adsorbents such as bentonites active carbon and attapulgite. The adsorption of colors in the low concentration conform to Freundlich type isotherm. Studying on the effect of pore distribution on the adsorption process,we found that the adsorption is the co-function of surface structure, surface and pore distribution. Only when the pore sizes and distributions of attapulgite get along with the best estate, can we gain the highest adsorb capacity and the fast adsorb speed. From the change of standard thermodynamics function we can investigate the trend,degree and drive force of the adsorption of colors on the attapulgite. The adsorption enthalpy change(-0.0434~-0.0036kJ/mol), Gibbs free energy change (-10.23~-11.77 kJ/mol) and entropy change(-33.34~-27.78 J/mol.K ) were calculated according to the relationship of the thermodynamic function. The results showed that the adsorption of color particles is an exothermic processes. With the increasing of temperature and quantity of adsorbent , the adsorption increased. The sorption of color particles by attapulgites was an entropy-increasing process in this temperature range.(3)The adsorption of chorophyll, carotenoid, phosphorusand linoleic acid can divide into two steps: in the first step,the adsorption time is very short ;in the second step,the adsorption is long. The adsorption dynamics of chorophyll and phosphorus, follows the laws of Bamgham.The adsorption of carotenoid obviously has a inducement period .The adsorption of linoleic acid was irregular. In the oil bleaching system , the existence of triglyceride can prolong the other minim-components'adsorption. On the other hand, when the balance between the liquid phase...