Intramolecular dehydration of 5-nonanol over ion exchange resins

Abstract

Due to increasing environmental awareness as well as diminishing oil reserves, in recent years, pathways to obtaining renewable chemicals have been studied. One of the clearest pathways is to obtain bio-chemicals from lignocellulose. It consists mainly of lignin, hexoses and pentoses. A very wide range of reactions to obtain bio-chemicals is opened from hexoses (glucose, etc.) and pentoses (fructose, etc.). One of these pathways is the formation of alkenes from levulinic acid. It is a serial reaction system that undergoes the formation of γ–valero lactone, pentanoic acid and 5-nonanone. Later 5-nonanone is hydrogenated to obtain 5-nonanol, which is the starting point of the reaction that we propose to study: the dehydration of 5-nonanol to nonenes using ion exchange resins as catalysts. Nonenes are usually used to improve the gasoline blending. The reaction, discussed above, will be studied by performing catalyst screening and working with different reaction temperatures in a stirred tank batch reactor with the purpose of maximizing nonene production. The research clearly indicates that the catalytic reaction takes place mostly on the outer surface of the ion-exchange resins. Studied resins with different structural property yielded similar results in terms of selectivity. A mixture of nonenes were obtained, but no side-reactions were detected. The acid capacity of the resins is the most relevant property: the greater the acid capacity the higher the conversion of 5-nonanol. Thus, at 150ºC, the highest alcohol conversion and reaction rate was obtained over Amberlyst 35. Furthermore, the reaction was studied in the temperature range 140-180ºC over the thermostable resin Amberlyst 45. As expected, both alcohol conversion and reaction rate increased with temperature, with a selectivity of 100% to nonenes. The activation energy was estimated to be 138 kJ/mol