Acid functionalized carbons as catalyst for glycerol etherification with benzyl alcohol

Abstract

In this paper, the catalytic behaviour of two different carbonaceous systems, commercial carbon (Cc) and synthetic carbon (Cs) functionalized with concentrated sulfuric acid (–SO₃H) and with reduced aryl diazonium salt (–PhSO₃H), was studied in the etherification of glycerol (Gly) with benzyl alcohol (BA). The catalytic activity and selectivity were studied varying the catalyst percentage (5, 10 and 15 wt%) and the initial reactant mass ratio. Taking into account the results obtained, the experimental conditions selected to continue with the catalytic studies were: temperature 393 K, Gly:BA molar ratio 3:1 and a catalyst loading of 10 wt%. Mono- and diethers were the main products. For the Cc-based catalysts, higher conversion (66%) and selectivity (90%) were obtained with the most acidic system, Cc–PhSO₃H. Changing the carbon functionalization method (–PhSO₃H for –SO₃H groups) produced a considerable increase in glycerol conversion (from 23 to 66%) and in selectivity to ME + DE (from 62 to 90%). On the other hand, for both Cs-based systems a great increase in performance was obtained, about 95% conversion after 360 min of reaction. Monoether was the major product of the reaction with a selectivity of 79% for Cs–SO₃H and 87% for Cs–PhSO₃H, which was maintained with reuse. Etherification of glycerol (Gly) with benzyl alcohol (BA) with two carbonaceous systems synthesized in the laboratory and functionalized with –SO₃H and –PhSO₃H.