A Non-sodium Synthesis of Highly Ordered V-MCM-41 and Its Catalytic Application in Isomerization

Abstract

A rapid non-sodium process was developed to synthesize highly ordered V-MCM-41 mesoporous materials with atomic level dispersed vanadium species. NH 3 ÁH 2 O instead of NaOH was used to maintain the moderately basic synthesis condition. The characterization results of N 2 physisorption and XRD showed that the synthesized samples had highly ordered hexagonal structure. UV-Vis, UV-Raman, and EPR spectra provided evidence that most vanadium ions were tetrahedrally incorporated into the framework of siliceous MCM-41. The NH 3 -TPD proved the mild acidity of V-MCM-41 due to the incorporation of vanadium cations. The most important variables were structural order and vanadium loading which can be controlled easily by changing synthesis variables in such a way that collapse of the V-MCM41structure did not occur. The synthesized V-MCM-41 catalysts successfully catalyzed the isomerization of heptene. High conversion and isomer selectivity were achieved with good catalytic stability. The structure of V-MCM-41 can be well preserved after reaction.

Spherical V-MCM-48: the synthesis, characterization and catalytic performance in styrene oxidation

“…20,43 The band of bulk V 2 O 5 crystallites (ca. 450 to 480 nm) is not observed for all samples, 17,18 which accords well with XRD results.…”

“…Minor changes in experimental conditions, including pH, temperature, aging time or concentration of the template, may lead to the absence of cubic mesoporous structure. 10,17 Due to the lack of catalytic sites for pure mesoporous silicate materials, the incorporation of transition metals, 7,[18][19][20][21][22][23][24] including Ti, Mn, Fe, Cu and V, into the framework of M41S has been widely examined. The doping of transition metals can modify the surface acidity/basicity and the redox property of the mesoporous molecular sieves, and as a result, improve their catalytic activity.…”

Catalytic Epoxidation of cis-Cyclooctene over Vanadium-Exchanged Faujasite Zeolite Catalyst with Ionic Liquid as Cosolvent

“…Compared to the fresh catalyst, the peak at 273 nm disappears, implying the destructive tetrahedral structure of vanadium species during the reaction. For the used catalyst V-X in [emim]­[NTf 2 ], the peak at 261 nm assignable to V 5+ in tetrahedral coordination is still retained. − The peak shows a bathochromic shift compared to the corresponding peak of fresh V-X catalyst at 273 nm. The higher energy band implies that a greater distortion of tetrahedral structure has been developed along with the decrease of coordination number. , In addition, another broad peak appears at about 348 nm that can be assigned to the polyvanadate species in either tetrahedral or pentahedral coordination. − …”

“…For the fresh V-X catalyst, the strong peak at 218 nm in the UV–vis spectrum has no distinct difference compared to the parent faujasite zeolite. The peak at 273 nm is attributed to V 5+ in tetrahedral coordination. − The Raman bands at 294, 384, and 517 cm –1 are assigned to the parent faujasite zeolite. The 968 cm –1 band is due to V–O stretching. , The sample is easily hydrated under ambient conditions; thus, the VO–H resonance under a UV excitation causes the disappearance of the terminal VO stretching bands in the range of 990–1050 cm –1 .…”