Chemical analysis of impurities in diverse bioethanol samples

Abstract

Bioethanol has recently become an important resource for chemical industries. The chemical compositions of 17 different types of bioethanol were investigated with a focus on impurities that could affect catalytic performances in the downstream chemical processes. Lignocellulosic ethanol contained higher concentrations and a greater variety of organic impurities compared to sugar- or starch-derived bioethanol. Twenty-nine impurities were identified in lignocellulosic ethanol, whereas 16 impurities were in sugar- or starch-derived bioethanol. Lignocellulosic ethanol contained high concentrations of acetic acid, acetaldehyde, methanol, and furan-related compounds such as furfural. In contrast, with the exception of molasses-derived bioethanol obtained by crude distillation, the concentrations of these components were lower in sugar- or starch-derived bioethanol samples. Lignocellulosic ethanol contained dimethyl disulfide and thiazole, whereas the only organosulfur compounds found in sugar- or starch-derived bioethanol were dimethyl sulfde and dimethyl sulfoxide. These sulfur-containing impurities can cause catalyst deactivation in the bioethanol transformation processes. In lignocellulosic ethanol, more than 0.1 μg/mL of Si was detected.