Abstract
The use of heterogeneous catalysts in the transesterification reaction of vegetable oils has getting emphasis in recent years, mainly by the alternative of obtaining clean fuel derived from renewable sources. Metal oxide such as MgO or CaO, supported ones like and zeolites are often applied in transesterification process. Among them, hydrotalcite has shown potential as catalysts on this reaction due to their physicochemical properties, such as: thermal stability, porosity, specific surface area, memory effect, basicity, acidity and anion exchange capacity. This work studies the catalytic performance of the calcium and aluminum based hydrotalcite in the transesterification reaction of soybean oil in methanol and ethanol. The hydrotalcite samples treated at 450?C were impregnated with KOH. The efficiency of impregnated and non- impregnated samples was compared and the non-impregnated one showed the best performance. This property was attributed to the higher availability of active sites used in the transesterification process.
Highlights
Biodiesel is a mixture of ethyl or methyl esters of fatty acids derived from natural sources
Various arrangements of di- and trivalent cations have been used in the synthesis of layered double hydroxides (LDHs) and they have been applied in several fields, such as: Hydrotalcite based on Mg-Al as a solid catalyst for the methanolysis of soybean oil, the results showed the activity of the catalysts for the methanolysis reaction was correlated closely with their basicity
The calcined hydrotalcites were considered effective as catalysts of soybean oil both with ethanol as methanol
Summary
Biodiesel is a mixture of ethyl or methyl esters of fatty acids derived from natural sources (vegetable oil or animal fat). This mixture has basically the same specification of mineral diesel, in terms of viscosity and density. The transesterification reaction is the most widely used route for obtaining biodiesel and it is constituted of a set of organic reactions. In a transesterification reaction the ester group (R'-COOR'') is replaced by an alkoxy radical (OH), which is derived from an alcohol. The presence of a catalyst (usually an acid or strong base) significantly accelerates the balance of reaction [1]
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