Hydrocarbon production from decarboxylation of fatty acid without hydrogen

Abstract

Decarboxylation of oleic acid without hydrogen was carried out using hydrotalcites with three different MgO contents (30, 63 and 70 wt%). Effect of MgO content in hydrotalcites and reaction temperatures on the decarboxylation performance in terms of oleic acid conversion and product distribution were investigated. Also, the stability of hydrotalcites in the decarboxylation reaction was examined by XRD analysis. It was found that MgO content in hydrotalcites and reaction temperature played key roles in decarboxylation reaction. At lower reaction temperature and MgO concentration in hydrotalcite, the conversion of oleic acid scarcely occurred. On the other hand, oleic acid conversions were more than 98% and the oxygen content in the reaction product was less than 1 wt% in the case of decarboxylation with MG63 (63% of MgO) and MG70 (70% of MgO) at 673 K. Solid-like products were formed in the reaction at 623 K, resulting from saponification of oleic acid and MgO. Considering conversion and the stability of catalysts, higher temperature, 673 K, is preferred to prevail decarboxylation over saponification. It was confirmed that most of the oxygen molecules in oleic acid were removed in the form of CO 2 from the elemental and FT-IR analysis of the liquid products. Pure hydrocarbons such as octane, nonane and heptadecene were produced in the case of MG63 and MG70 at 673 K while decanoic acid was additionally observed in case of blank test and MG30 catalyst at 673 K.