Paper
Combining Ion Exchange and Water Adsorption Processes for High Grade Glycerol from Biodiesel
- Authors:
- Manuel Carmona; María María Teresa García; Ángela Ángela Alcázar; Juan F. Rodriguez; Ángel Ángel Carnicer
- Abstract
- Two different ways to purify crude glycerol have been proposed depending on the catalyst used in the biodiesel production. When alkalis as NaOH or KOH are used ion exchange and adsorption could be advantageously employed to remove the salt and water content respectively. In this work, the water removal is accomplished by using three different molecular sieves zeolite 5A in Na+ and Ca2+-form, Zeolita A in Na+ and Ca2+-form and Zeolita A in K+-form commonly applied for water adsorption. The larger water sorption capacity of the zeolite 5A-Na, Ca at 303 K allowed selecting it as the best choice for the dehydration of glycerol. The adsorption experimental data were fitted with the adsorption model of Tóth and further experiments have been carried out at 318 and 333 K with the aim to obtain the thermodynamic properties △Hº and △Sº. The negative values of these both properties indicated that this adsorption process is exothermic and feasible. On the other hand, when sodium or potassium alkoxides are used in the biodiesel production water is not involved in glycerol purification. Thus, ion exchange studies for the systems H+/Na+ and H+/K+ using the resin Amberlite 252 for a solution containing a mixture 50/50 of glycerine in methanol and a methoxide content of 0.25 mol L-1 at 298 K were carried out. Langmuir equation was used to fit the experimental equilibrium data and the shape of the isotherm confirms the irreversibility of the process leading to the methanol production. It was obtained that the Langmuir separation factor is independent on the system but the maximum ion uptake is higher for the K+ than Na+ attending to its low hydrated radii. These results confirm the feasibility to purify glycerol streams by applying the proper technology in a aqueous or non-aqueous media.
- Keywords
- Glycerol; Ion Exchange; Adsorption; Biodiesel
- StartPage
- 14
- EndPage
- 22
- Doi