Active sites for adsorption of B-carotene
Loading...
Date
1982-03
Authors
Tan, Siam Hwa
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The nature of active sites in aluminosilicates for the adsorption of B-carotene was investigated. Cation exchanged zeolites with varying + 2+ 2+ 3+ 2+ extent of exchange of NH4+, Mg2+, Ca2+, Fe3+ and Cu2+ were prepared. The crystallinity of these samples activated at 450°C were checked by x-ray diffraction and the surface areas were determined by N2 adsorption (BET). The surface acidities of the samples were also determined by nonaqueous titration using triphenylmethanol indicator. Apparent adsorption isotherm of B-carotene in acetone by activated cation exchanged zeolites were obtained at ambient temperature. The adsorption activities increased with the increase in the extent of exchange of Na+,ion for NH4+, Fe3+ and Cu2+ ions. However, no activiy was observed for Na+, Mg 2+ and Ca 2+ exchanged zeolites. The order of activities was found to be: Cu2+ >Fe3+ >H+>>Mg2+-Ca2+-Na+. The removal of B-carotene by the cation exchanged zeolites involved an initial rapid chemisorption process followed by a zero order reaction. In Cu(II)NaY, the apparent activation energy for the zero order reaction was 9. 94 kcal. mol-1. Bronsted acidity and transition metal ions were proposed to be the active centres. In HNaY and HNaX, the activities are due to the Bronsted acid sites. MgNaX and CaNaX are not active because the Bronsteds acid are located in inaccessible positions
Description
Keywords
B-carotene