Esterification Catalyzed By Interfacial Photothermal Heating

As an important chemical raw material,ethyl acetate is widely used in rubber,plastics,dyes and spices.In China,the preparation of ethyl acetate by acetic esterification is the most common method.This process relies on the reversible reaction of acetic acid and ethanol,but all the reversible chemical reactions are governed by the equilibrium law.It means that under the fixed reaction conditions,the conversion of the reaction has its equilibrium limit.To improve the productivity of esters,conventionally superfluous reactants and dehydrants are used to further drive the forward reaction.However,these methods are not only energy intensive but also cause more difficulty in separating the final products.Herein,we propose an interfacial photothermal catalysis design based on a sulfonic acid functionalized graphene aerogel to realize esterification beyond the chemical equilibrium limit without excess reactants or dehydrants.During this process of interfacial photothermal catalysis,because of the local photo-thermal effect and different molecular bond affinities with catalyst,the generated products evaporate out of reactive sites quickly,leading to the local excess of reactants and thereby thermodynamically driving the reaction toward the ester generation.Taking ethyl acetate as a typical example for demonstration,a record acetic acid conversion of77% is achieved without adding excess reactants(reactants feed ratio 1:1),which was significantly higher than the theoretical chemical equilibrium limit(62.5%)in traditional homogeneous reaction system.The dual advantages of the system in structure design and material design made it better catalytic performance.The cyclic stability and expandability of the material are also well verified.Finally,the theoretical calculation shows that it has significant advantages in saving energy consumption of product separation when it is applied to industrial esterification reaction.It is expected that this interfacial photothermal catalytic system can be applied not only to esterification,but also to other chemical synthesis fields such as thermal catalysis,nitration and acylation.