Esterification of n-Butanol with Acetic Acid in the Presence of H3PW12O40 Supported on Mesoporous Carbon Materials

The adsorption of H3PW12O40 (HPA) from methanol solutions on mesoporous carbon supports (multiwall carbon nanotubes (CFC-3) and CFC modified with nitrogen atoms (N-CFC)) was studied. It was found that up to 10 wt % HPA was irreversibly adsorbed on the surface of CFC. This character of adsorption is indicative of the strong interaction of the adsorbate (HPA molecules) with coal surface groups (carboxylic, lactone, etc.) to form intermolecular hydrogen bonds with π-electron interactions. It was found that N-containing surface centers affected the adsorption of HPA on N-CFC. The acid and catalytic properties of HPA/CFC systems in the esterification reaction of n-butanol with acetic acid were studied ([BuOH]/[HOAc] = 1 : 15 mol/mol; 80°C). It was found that the strength of proton centers, which was determined as proton affinity, decreased upon supporting HPA. The HPA/CFC-3 systems most actively catalyzed the reaction. The catalytic activity of HPA/N-CFC depended on the nature of N-containing groups at the support surface, and it decreased with concentration of pyridine-like structures.