Browsing by Author "Elizabeth R. Lachter"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Correlating Chemical Structure and Physical Properties of Vegetable Oil Esters
    (2006) Elizabeth R. Lachter; Fabianne de P. Cardoso; Jorge de A. Rodrigues; Regina S.V. Nascimento; Edson Lima; Luciana R.M. Estevao
    The influence of FA ester chemical structures on the rheology and crystallization temperature of those compounds was evaluated using methyl, n-butyl, n-octyl, and 2-ethyl-1-hexyl FA esters with different chain lengths and different degrees of unsaturation. The rheological properties were analyzed in a highprecision rheometer at various temperatures, and the crystallization temperatures were determined by DSC. Esters produced from the esterification of pure FA and from the transesterification of vegetable oils (i.e., soybean, corn, linseed, and babassu coconut oils) were evaluated. The length of the FA chain was shown to have a marked influence on the viscosity and crystallization temperature of the systems, whereas branching affected only the crystallization temperature to a significant extent. The viscosity and crystallization temperature of the systems were also influenced by the degree of unsaturation. One double bond was shown to increase viscosity, whereas two or three double bonds caused a decrease in the viscosity of the systems. Unsaturation lowered the crystallization temperature in all cases, regardless of the number of double bonds. From all the oils studied, methyl esters from babassu coconut oil presented the lowest crystallization temperatures
  • Thumbnail Image
    Item
    Transesterification of Brazilian Vegetable Oils with Methanol over Ion-Exchange Resins
    (AOCS Press, 2005-09) Simone C.M. dos Reis; Elizabeth R. Lachter; Regina S.V. Nascimento; Jorge A. Rodrigues Jr.; Marcelli Garcia Reid
    The transesterification of several Brazilian vegetable oils with methanol was carried out at 60°C in the presence of several ion-exchange resins having different structures. The vegetable oils used were from Babassu coconut, corn, palm, palm kernel, and soybean. The effect of the methanol/oil mole ratio and the influences of the structure of the ion-exchange resin and the type of vegetable oil used on the catalytic activity of the ionexchange resins were investigated. The resins used were Amberlyst 15, Amberlyst 31, Amberlyst 35, and Amberlyst 36. Amberlyst 15 produced the best results for the transesterification of vegetable oils. The methyl ester yield is higher for palm kernel oil and Babassu coconut oil than for soybean oil, probably owing to their higher content of shorter-chain FA. Therefore, it was shown that the catalytic activity of the resin depends on the FA composition of the vegetable oil employed.