This work presents the biofuel production results of the esterification of fatty acids (C12-C18) and high-acid-content waste vegetable oils from different soap stocks (soybean, palm, and coconut) with methanol, ethanol, and butanol by acid catalysis. We used Amberlyst-35 (A35) sulfonic resin as a heterogeneous acid catalyst and p-toluenesulfonic acid as a homogeneous catalyst for comparison. Both the heterogeneous (A35) and homogeneous (p-toluenesulfonic acid) reactions were performed with 5% w/w of catalyst. The final products were analyzed by proton nuclear magnetic resonance (1H NMR). The homogeneous catalyzed esterification of fatty acids with methanol, ethanol, and butanol produced esters with yields higher than 90%. In the reaction with fatty acids and methanol catalyzed by A35, the best results were achieved with lauric acid and methanol, with a yield of 97%. An increase in the hydrocarbon chain decreased the rate of conversion and yield for stearic acid with methanol, which was 90%. Maximum biodiesel production was achieved from coconut and soybean soap stocks and methanol (96%-98%), which showed conversions very close to those obtained from their respective fatty acids. Microwave irradiation reduced the reaction time from 6 to 1 h in the esterification reaction of fatty acids with butanol.

A atividade catalítica de sólidos ácidos como o fosfato de nióbio e a Amberlyst 35, uma resina trocadora de íons, foi avaliada na acetalização do hexanal com 2-etil-hexanol. Foram avaliadas a concentração do catalisador e a temperatura de reação na conversão do hexanal. A possibilidade de re-utilização do fosfato de nióbio também foi estudada e evidenciou ser possível re-utilizar este catalisador sem perda da atividade. O rendimento em acetal foi acima de 90% em condições brandas de reação.

The catalyst activity of solid acids such as niobium phosphate and Amberlyst 35, an ion exchange resin, was evaluated in the acetalization of hexanal with 2-ethyl-hexanol. The catalyst loading and the reaction temperature were evaluated in the hexanal conversions. The possibility of recycling niobium phosphate was also studied, showing that it was possible to reuse this catalyst without significant loss in its catalytic activity. The yield in acetal was above 90% under mild conditions.

Diferentes suportes poliméricos à base de estireno (S) e divinilbenzeno (DVB) foram sintetizados e suas morfologias caracterizadas por microscopia óptica e eletrônica de varredura. Foram preparados e caracterizados catalisadores sulfônicos a partir desses suportes e suas atividades catalíticas foram avaliadas na transesterificação de óleo vegetal com metanol. Os resultados obtidos com esses catalisadores foram comparados com os produzidos com uma resina sulfônica comercial. Verificou-se que os catalisadores sintetizados neste trabalho apresentaram desempenhos próximos ao da resina comercial.

Different polymer supports based on styrene (S) and divinylbenzene (DVB) were synthesized and their morphology was characterized by optical and scanning electron microscopy. Sulfonic catalysts were prepared from these supports, characterized and their activities were evaluated in vegetal oil transesterification with methanol and compared with the performance of a commercial sulfonic resin. The synthesized catalysts showed results close to the commercial resin.