Ce–UiO-66 Derived CeO₂ Octahedron Catalysts for Efficient Ketonization of Propionic Acid

Abstract

CeO2–UiO octahedron catalysts derived from cerium-based metal–organic frameworks Ce–UiO-66 were synthesized for vapor-phase ketonization of propionic acid. Characterizations showed the CeO2–UiO octahedron is assembled from nanosized CeO2 crystallites with mesopores. XPS and Raman results indicated that more oxygen vacancies are formed in CeO2–UiO-450 catalyst than in CeO2–P prepared by a precipitation method. Intrinsic ketonization rates on CeO2–UiO-450 are improved relative to CeO2–P. At 350 °C, the turnover frequency based on acid–base pair on CeO2–UiO-450 (7.45 s–1) is 1.38 times higher than that on CeO2–P (5.41 s–1). Consistently, the activation energy is lowered from 130.5 kJ/mol for CeO2–P to 109.0 kJ/mol for CeO2–UiO-450. Infrared spectroscopy results showed that monodentate carboxylate is the active adsorption configuration, and its consumption is much faster on CeO2–UiO-450 than on CeO2–P. A linear correlation between the concentration of oxygen vacancy and intrinsic ketonization rate is found, indicating that the oxygen vacancy promotes ketonization on CeO2.

From Trash to Treasure: Probing Cycloaddition and Photocatalytic Reduction of CO2 over Cerium-Based Metal–Organic Frameworks

“…Figure b shows the XRD patterns of the synthesized Ce-MOFs. The XRD pattern of Ce-BDC is in good agreement with the literature, confirming the formation of the face-centered cubic MOF structure (space group Fm 3̅ m ) with hexanuclear [Ce 6 O 4 (OH) 4 (BDC) 6 ] clusters. , On the other hand, hydrothermally synthesized Ce-BDC-NH 2 is found to be isostructural with La-BDC-NH 2 MOF reported in the literature . XRD patterns confirm that the synthesized Ce-BDC and Ce-BDC-NH 2 are not of an isoreticular structure.…”

Ketonization of Propionic Acid on Lewis Acidic Zr-Beta Zeolite with Improved Stability and Selectivity

“…Ketonization of propionic acid (99%, J&K) was investigated in a fixed-bed tubular quartz reactor, as described in previous work. , The sample of 40–60 mesh was packed in the middle of the reactor and pretreated at 350 °C for 0.5 h in flowing Ar prior to reaction. Then, propionic acid was fed by a KDS-100 syringe pump (KD Scientific) and vaporized before entering the reactor.…”

Modular assembly of electron transfer pathways in bimetallic MOFs for photocatalytic ammonia synthesis

“…The vibration peaks of 1162, 1040 and 767 cm −1 corresponded to the deformation vibration of carboxyl and benzene, respectively. 23,[28][29][30] In addition, in the metal node of the UiO-66 series MOFs (M 6 O 4 (OH) 4 , M = Ce or Hf), the metal change does not obviously affect the peak position of their functional groups. 23,28 Therefore, the vibration modes at 679, 580 and 473 cm −1 are attributed to the stretching vibrations of M-O, μ 3 -O and μ 3 -OH, respectively.…”