Effects of solid supports on the kinetics of Ester hydrolysis.

Abstract

Research into catalytic and adsorptive properties of various naturally occurring substances is crucial. Catalysis and adsorption plays a very important role in the industrial world, especially in the fields of synthesis purification/refinery and pollution control. In this research work results obtained on adsorption of esters in clay montmorillonites and activated charcoal have been presented. The resultant change in physical and chemical properties of montmonillonite and/or activated charcoal, especially on treatment with acid and/or heat are shown to affect the adsorption properties of the esters. The adsorption efficiencies for raw montimorillonite clays and charcoal have been shown to be above 93% and independent of the amount of solid support used. Acid treatment of the solid supports has however been observed to enhance the adsorption efficiencies of bentonite and zeolite and at the same time diminish those of diatomite and activated charcoal. The adsorption efficiency of activated charcoal decreased to 65% on treatment with conc. Sulphuric in a ratio of 5:1(acid: charcoal, wtlwt). When bentonite was heated in the oven and then used as a matrix to adsorb ethyl acetate, an inverse linear l relationship between the amount of ethyl acetate adsorbed and the quantity of bentonite used was observed. Infra-red spectra showed that the C=O stretching vibration of the adsorbed molecules shifted to lower frequencies compared with the carbonyl band at 1700cm-1 in the spectra of pure liquids. This observation points to the fact that the carbonyl group of the ester is hydrogen bonded to hydroxyl of the silicate layer. The Lewis and Bronsted acid sites on the raw and acidified bentonite samples were also identified from the infra-red spectra of ethyl acetate adsorbed in the raw and acidified samples. This was in line with the observations madesey Segar et al (1999) and Mokaya et al (1992).