Abstract
Sulfonated carbonaceous material useful as a solid acid catalyst was prepared from lignosulfonate, a waste of the paper-making industry sulfite pulping process, and characterized by 13C-NMR, FT-IR, TGA, SEM and elemental analysis, etc. The sulfonic acid group density and total density of all acid groups in the sulfonated carbonaceous material was determined by titration to be 1.24 mmol/g and 5.90 mmol/g, respectively. Its catalytic activity in the esterification of cyclohexanecarboxylic acid with anhydrous ethanol was shown to be comparable to that of the ionic exchange resin Amberlyst-15, when they were used in the same amount. In the meantime, the sulfonic acid group was found to be leached out by 26%–29% after it was exposed to hot water (95 °C) for 5 h. The catalytic usefulness of the prepared carbonaceous material was investigated by performing esterifications.
Highlights
IntroductionOver the recent two decades or so carbon-based solid acids have received much attention in the fields of catalysis and organic synthesis [1,2,3,4,5,6,7,8,9,10,11,12,13,14]
Over the recent two decades or so carbon-based solid acids have received much attention in the fields of catalysis and organic synthesis [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. They have several advantages such as readiness of separation from the reaction mixture, resulting reusability, and reduction in the amount of waste water generated in washing processes for removing the remaining acid from products, compared to homogenous catalysts such as p-toluenesulfonic acid or sulfuric acid when used in organic reactions
The catalyst was prepared from the lignosulfonate according to Scheme 1
Summary
Over the recent two decades or so carbon-based solid acids have received much attention in the fields of catalysis and organic synthesis [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. Lignosulfonate is an interesting compound because it already has a sulfonic acid group on the sp carbon of the molecule and an activated aromatic ring available for electrophilic sulfonation. It was chosen as a starting material with a hope that some catalyst characteristics such as density of SO3H groups and resistance to hydrolysis might be improved
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