Solvent-Free Synthesis and Characterization of Bimetallic UiO-66(Zr/Sn) Heterogeneous Catalyst for Biodiesel Production

Ithas been verified that UiO-66(Zr) is an effectiveheterogeneouscatalyst for the production of biodiesel. The construction of multimetalsites in the structure of UiO-66(Zr) can be a promising way to enhancethe catalytic performance of UiO-66(Zr). In this contribution, UiO-66(Zr)with tin sites is simply fabricated under solvent-free conditions.The results from XRD, EDX, and XPS analyses indicate that tin specieshave been introduced into the structure of UiO-66(Zr). The nitrogensorption data show that UiO-66(Zr/Sn)-5-130-24 obtained under optimizedsynthesis conditions maintains a large BET specific surface area (1170m(2)/g) and pore volume (0.84 cm(3)/g). The NH3-TPD results reveal that UiO-66(Zr/Sn)-5-130-24 possessesmore acid sites than UiO-66(Zr) probably because the introductionof tin species brought about the missing of linkers in the structureof UiO-66(Zr). As a consequence, UiO-66(Zr/Sn)-5-130-24 exhibits highercatalytic efficiency with an oleic acid conversion of 98.8% than UiO-66(Zr)(oleic acid conversion of 86.2%) at 333 K in the esterification reactionof oleic acid with methanol to obtain biodiesel. Furthermore, thereusability test demonstrates that such a catalyst can be readilyrecycled and reused.