Fischer esterification is one of the most prominent industrial methods of ester production, involving a reaction between an alcohol and carboxylic acid in the presence of a catalyst to turn the carboxylic acid into an ester. However, Fischer esterification results in large amounts of waste due to the reaction reaching equilibrium, leaving reactants unconsumed. To increase the yield of ester, various catalysts were tested to determine their efficiency in the reaction between ethanol and citric acid, which form a common ester compound called triethyl citrate, used as a flavoring agent. A sulfonated silica gel catalyst was included in the reaction as a method of removing water from the reaction. Additionally, zinc oxide was used as a UVC photocatalyst to facilitate the nucleophilic attack of the alcohol on the carboxylic acid as the Zn2+ and O2- ions protonate the carboxylic acid. The sulfonated silica gel catalyst was tested in various quantities all with a one-hour reaction time. As expected in the hypothesis, as the quantity of sulfonated silica gel added to the reaction increased, so did the yield of ester. The ZnO was tested in the same quantities but at varying reaction times since it is a recyclable catalyst. It was determined that increasing the reaction time also increased the yield of reaction, further supporting the hypothesis. Compared to the control H2SO4 catalyzed reaction, both the sulfonated silica gel and ZnO catalysts resulted in higher yields of ester, suggesting that the implementation of combined catalytic techniques would benefit industrial ester production.
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