Interesterificação Do Óleo De Crambe Com Adição De Solução Aquosa De Ácido Acético Ao Meio Reacional

Abstract

A interesterificação permite a obtenção de ésteres livre de glicerol, com a produção da triacetina, que pode ainda ser utilizada como aditivo ao biocombustível. A fim de potencializar a produção de ésteres e triacetina a inserção de aditivos a reação tem sido abordada. O presente estudo teve como objetivo avaliar o efeito de adicionar solução aquosa de ácido acético 26% (SA26%) em 5 e 10% (em relação a massa de óleo) sobre o rendimento em ésteres e teor de triacetina, bem como verificar seu efeito sobre os ésteres individuais, variando a temperatura da reação de 300 a 325 °C e tempo de residência entre 10 a 30 minutos. Para a maioria das reações conduzidas com SA(26%) a 300 °C houve maior produção de ésteres, se comparadas as reações sem o aditivo (p<0,05). Os resultados demonstraram que as reações conduzidas com SA26% permitiram elevar os rendimentos de ésteres em até 45%. Foi possível constatar ainda conversão completa dos triglicerídeos em ésteres com apenas 20 min de reação, com 10% de SA(26%) 300 °C. O aumento da temperatura resultou em maior rendimento inicial (10 min), contudo foi observada redução dos ésteres individuais analisados, sendo que, dentre estes o linoleato se mostrou mais susceptível a decomposição térmica. AbstractThe interesterification allows the production of esters free of glycerol, with the production of triacetin, which can still be used as an additive to biofuel. In order to potentiate the esters and triacetin production the insertion of additives into the reaction has been approached. The present study aimed to evaluate the effect of adding aqueous solution of acetic acid 26% (SA26%) in 5 and 10% (relative to oil mass) on the ester yield and triacetin content, as well as to verify its effect on obtaining the individual esters, varying the reaction temperature from 300 to 325 °C and residence time between 10 to 30 minutes. For the majority of the reactions conducted with SA26% at 300 °C there was higher ester production, when compared with the reactions without the additive (p<0.05). The results showed that the reactions conducted with SA26% allowed to raise ester yields by up to 45%. It was also possible to verify complete conversion of the triglycerides to esters with only 20 min of reaction, with 10% of SA26% at 300 °C. The increase in temperature resulted in a higher initial yield (10 min), however, a reduction of the individual esters analyzed was observed, with linoleate being more susceptible to thermal decomposition.

Use of the Product from Low Pressure Extraction (Crambe Seed Oil and Methyl Acetate) for Synthesis of Methyl Esters and Triacetin Under Supercritical Conditions

“…Exceptions were methyl linoleate, which showed a reduction of ≈47% at 300 °C, and methyl linolenate, which was not detected under the conditions evaluated. This behavior was expected due to the susceptibility of these MEs to thermal decomposition, with reductions in their content at 300 °C [ 4,33 ] and 325 °C [ 46,71 ] reported in the literature. According to Ortiz‐Martínez et al., [ 72 ] the ease of the thermal decomposition of methyl esters is related to the presence of unsaturation.…”

“…As described above (Equation (4)), the reaction between MA and FFA forms, besides ME, acetic acid, which can act as an acid catalyst, decreasing the thermal degradation of triacetin [ 31 ] and the time required for the conversion to esters. [ 33 ]…”

“…The pretreatment of the raw material is not required, and the separation and purification of the products are relatively easy steps, [ 30 ] and thus unrefined oils can be used, which reduces the cost. Another advantage is that the free fatty acids in these oils form acetic acid, as seen in Equation (4), which enhances the reaction rate due to its catalytic effect, [ 31–33 ] enabling the products to be obtained in a shorter time. [ 31,32,34 ] …”