Browsing by Author "Khalifa, Muzafar Tagelsir Hamza"
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- ItemCharacterisation of the adsorption and regeneration behaviour of a commercial activated alumina adsorbent when separating 1-hexanol and 1-decanol from n-decane(Stellenbosch : Stellenbosch University, 2023-03) Khalifa, Muzafar Tagelsir Hamza; Burger, Andries Jacobus; Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering.ENGLISH ABSTRACT: Paraffins produced in industry are usually associated with impurities such as oxygenates, and adsorption is commonly used to remove these oxygenates (e.g. alcohols). However, the recyclability of such adsorbents has rarely been studied. In this study, the reusability of activated alumina adsorbent used to adsorb 1-alcohols from a paraffin solvent was investigated. The objectives of this study included: (I) the measurement and investigation of single and binary-component adsorption data; (II) the modelling of equilibrium adsorption isotherms and adsorption kinetics; and (III) the measurement and investigation of the efficiency of adsorbent throughout consecutive adsorption/thermal regeneration cycles. One type of commercialized activated alumina adsorbent was used in this study. 1-hexanol and 1-decanol were used as adsorbates, while n-decane was used as the solvent. The effect of initial adsorbate concentration and alcohol carbon chain length on the adsorption and desorption were also briefly investigated. A bench-scale batch adsorption set-up was used for adsorption experiments. Schott bottles containing 1-alcohols + n-alkane solutions (at various initial concentrations of adsorbates) and adsorbents (10g of fresh adsorbent at first experiment) were immersed in a water bath, where the water temperature was maintained at 65 °C. The regeneration experiments were carried out at 205 °C, 185 °C and 165 °C using thermal regeneration columns. Heated purging carrier gas (nitrogen) was used to sweep through the adsorbent for the full duration of regeneration. For both single-component and binary systems, the total equilibrium adsorbent loading was found to increase when increasing the adsorbates’ initial concentration. For single-component solutions, the total adsorption capacity increased systematically as the initial concentration of adsorbates increased up to 2.5 mass%, but at even higher initial concentrations the capacity remained relatively constant. For the binary system, the equilibrium adsorbent loading began to plateau at initial concentrations higher than 2.0 mass%. The effect of carbon chain length exhibited different behaviour for single-component and binary systems. The adsorbent proved a slightly higher affinity to adsorb more of the 1-decanol in the single-component system, whereas in the binary system it was inclined to adsorb more of the 1-hexanol. At similar 1-alcohol initial concentrations in single and binary systems, it was found that the adsorption of a specific 1-alcohol from the binary systems was remarkably poorer than the adsorption of the same 1-alcohol from the corresponding singlecomponent systems. Equilibrium studies showed that the Freundlich and Sips isotherms are suitable for the single 1-hexanol and single 1-decanol adsorption systems, respectively. However, for the binary system, poor correlation was exhibited between the date and the Extended Langmuir, Extended Freundlich and Extended Sips models. Both single-component and binary systems can be described by Elovich kinetics and the Intra-Particle Diffusional Model. As expected, higher efficiencies were achieved for the respective single-component systems than for the binary system. As far as regeneration behaviour is concerned, the activated alumina adsorbent exhibited an adverse response to the highest regeneration temperature (205 °C). For both single-component and binary systems, the adsorbent offered a better efficiency at the regeneration temperature of 185 °C than at 205 °C and 165 °C. BET analysis showed a notable reduction in the total surface area of the regenerated adsorbent at 165 °C, indicating incomplete regeneration at such low temperature, was also confirmed by a systematic drop in adsorption efficiency down to 40% at the final regeneration cycle.