Zirconium-containing UiO-66 as an efficient and reusable catalyst for transesterification of triglyceride with methanol

Abstract

Zirconium-based MOFs of the UiO family have attracted considerable attention due to their high thermal, chemical and mechanical stability. With the aim of further exploring the applications of zirconium-based UiO-66 in acid-catalyzed reactions and elucidating the effects of the defects in UiO-66 materials on their catalytic performances, in this work, a series of zirconium-containing UiO-66 samples were synthesized by varying the synthesis temperatures and BDC/Zr (terephthalic acid/ZrCl 4 ) ratios in the synthesis system. The synthesized UiO-66 samples were characterized by X-ray diffraction (XRD), N 2 adsorption-desorption, scanning electron microscopy (SEM), thermogravimetrical analysis (TGA), temperature-programmed desorption of NH 3 (NH 3 -TPD). Their catalytic performances were investigated in transesterification of tributyrin and soybean oil with methanol. The results showed that UiO-66 samples with different amounts of defects could be successfully prepared by varying the synthesis temperatures and/or the BDC/Zr ratios used in the synthesis system. The catalytic activities of the UiO-66 materials greatly depended on their linker defects and enhanced with the increase of the defect amount. The UiO-66 was an efficient catalyst for transesterification of tributyrin and soybean oil with methanol under mild reaction conditions and its catalytic activity was comparable to other solid acid catalysts reported in the literatures. The UiO-66 catalyst was relatively stable and could be reused.

An alumina‐coated UiO‐66 nanocrystalline solid superacid with high acid density as a catalyst for ethyl levulinate synthesis

“…Two peaks in the NH 3 ‐TPD curve of UiO‐66 corresponded to weak acid and strong acid sites with corresponding desorbed ammonia volumes of 19 and 44 cm 3 g −1 , respectively (Table 1). Based on the results of TGA and literature reports, 40 the inorganic [Zr 6 O 4 (OH) 4 ] 12+ clusters in UiO‐66 would undergo dehydroxylation to form inner clusters of Z 6 O 6 as the temperature increased. UiO‐66 thus contained mostly Lewis acid sites.…”

“…UiO-66 is not strongly acidic, as it contains mostly weakly acidic sites and a small number of moderately acidic Lewis acid sites. 40 The Lewis acidity of UiO-66 arises from the unsaturated coordination of its Zr centers, which makes it a solid acid catalyst with broad application prospects. 41 Therefore, some researchers have improved UiO-66 for its application as a heterogeneous catalyst.…”

“…The morphological characteristics and microstructures were also examined using SEM, and the SEM images of the as‐synthesized WO x @UiO‐66 showed that the catalyst was composed of uniformly dispersed grape cluster‐like particles. UiO‐66 is not strongly acidic, as it contains mostly weakly acidic sites and a small number of moderately acidic Lewis acid sites 40 . The Lewis acidity of UiO‐66 arises from the unsaturated coordination of its Zr centers, which makes it a solid acid catalyst with broad application prospects 41 .…”

Hydrothermal Synthesis of Zr‐Amino Terephthalate and its Composite with MWCNTs as a Novel Electrode Material in Nitrite Quantification

“…A range of Zr−MOFs have been used as catalysts in several organic synthetic reactions like cross‐aldol condensation, esterification and in the degradation of dyes [16–19]. The electrochemical sensing applications of Zr MOFs are very few [20].…”

CO2 Hydrogenation to Methanol over Ce and Zr Containing UiO-66 and Cu/UiO-66

“…The stability of UiO-66 structure explains its wide use in heterogeneous catalysis. It was studied, e.g., in transesterification of triglyceride with methanol [24], sulphide oxidation [25], desulfurization [26], and other reactions [27]. A number of papers concerning catalytic performance of the UiO-66 modified in Zr nodes or the BDC linker, or decorated with metals, was published.…”