Epoxidation of propene on vanadium species supported on silica supports of different structure

Modulation of ODH Propane Selectivity by Zeolite Support Desilication: Vanadium Species Anchored to Al-Rich Shell as Crucial Active Sites

The commercially available zeolite HY and its desilicated analogue were subjected to a classical wet impregnation procedure with NH₄VO₃ to produce catalysts differentiated in acidic and redox properties. Various spectroscopic techniques (in situ probe molecules adsorption and time-resolved propane transformation FT-IR studies, XAS, ⁵¹V MAS NMR, and 2D COS UV-vis) were employed to study speciation, local coordination, and reducibility of the vanadium species introduced into the hierarchical faujasite zeolite. The acid-based redox properties of V centres were linked to catalytic activity in the oxidative dehydrogenation of propane. The modification of zeolite via caustic treatment is an effective method of adjusting its basicity—a parameter that plays an important role in the ODH process. The developed mesopore surface ensured the attachment of vanadium species to silanol groups and formation of isolated (SiO)₂(HO)V=O and (SiO)₃V=O sites or polymeric, highly dispersed forms located in the zeolite micropores. The higher basicity of HY_deSi, due to the presence of the Al-rich shell, aided the activation of the C−H bond leading to a higher selectivity to propene. Its polymerisation and coke formation were inhibited by the lower acid strength of the protonic sites in desilicated zeolite. The Al-rich shell was also beneficial for anchoring V species and thus their reducibility. The operando UV-vis experiments revealed higher reactivity of the bridging oxygens V-O-V over the oxo-group V=O. The (SiO)₃V=O species were found to be ineffective in propane oxidation when temperature does not exceed 400 °C.

Silica bonded N-(propylcarbamoyl)sulfamic acid (SBPCSA) as a highly efficient and recyclable solid catalyst for the synthesis of Benzylidene Acrylate derivatives: Docking and reverse docking integrated approach of network pharmacology

A green approach has been developed for the synthesis of a series of benzylidene acrylate 3(a-p) from differently substituted aromatic/heterocyclic aldehydes and ethyl cyanoacetate in excellent yields (90-98%), and employing silica bonded N-(Propylcarbamoyl)sulfamic acid as a recyclable catalyst under solvent-free condition. The molecular structure of compounds 3b, 3d and 3i were well supported by single-crystal X-ray crystallographic analysis. The present protocol bears wide substrate tolerance and is believed to be more practical, efficient, eco-friendly, and compatible as compared to existing methods. In-silico approaches were implemented to find the biochemical and physiological effects, toxicity, and biological profiles of the synthesized compounds to determine the expected biological nature and confirm a drug-like compound. A molecular docking study of the expected biologically active compound was performed to know the hypothetically binding mode with the receptor. Also, reverse docking is applied to recognize receptors from unknown protein targets for drug-like compounds to explain poly-pharmacology and binding postures with different receptors.

The design, synthesis and catalytic performance of vanadium-incorporated mesoporous silica with 3D mesoporous structure for propene epoxidation

Novel promising vanadium catalysts based on mesoporous silica of 3D structure, namely KIT-6, SBA-12, and MCF, for the direct propene epoxidation with N₂O.

Effect of SO2 on the Selective Catalytic Reduction of NOx over V2O5-CeO2/TiO2-ZrO2 Catalysts

The effect of SO₂ on the selective catalytic reduction of NO_x by NH₃ over V₂O₅-0.2CeO₂/TiO₂-ZrO₂ catalysts was studied through catalytic activity tests and various characterization methods, like Brunner−Emmet−Teller (BET) surface measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), hydrogen temperature-programmed desorption (H₂-TPR), X-ray photoelectron spectroscopy (XPS) and in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS). The results showed that the catalyst exhibited superior SO₂ resistance when the volume fraction of SO₂ was below 0.02%. As the SO₂ concentration further increased, the NO_x conversion exhibited some degree of decline but could restore to the original level when stopping feeding SO₂. The deactivation of the catalyst caused by water in the flue gas was reversible. However, when 10% H₂O was introduced together with 0.06% SO₂, the NO_x conversion was rapidly reduced and became unrecoverable. Characterizations indicated that the specific surface area of the deactivated catalyst was significantly reduced and the redox ability was weakened, which was highly responsible for the decrease of the catalytic activity. XPS results showed that more Ce³⁺ was generated in the case of reacting with SO₂. In situ DRIFTS results confirmed that the adsorption capacity of SO₂ was enhanced obviously in the presence of O₂, while the SO₂ considerably refrained the adsorption of NH₃. The adsorption of NO_x was strengthened by SO₂ to some extent. In addition, NH₃ adsorption was improved after pre-adsorbed by SO₂ + O₂, indicating that the Ce³⁺ and more oxygen vacancy were produced.

One-pot synthesis of vanadium-containing silica SBA-3 materials and their catalytic activity for propene oxidation

V-containing silica SBA-3 mesoporous catalysts were prepared by means of one-pot hydrothermal procedure with NH₄VO₃ or VOSO₄ as vanadium precursors under various acidic medium of the reaction mixture (pH < 1, 2.2 or 3.1). The combined spectral techniques (DR UV-vis, FTIR, EPR) as well H₂-TPR allowed to determine the nature of vanadium species in the studied samples. A successful incorporation of vanadium into the structure of silica SBA-3 was attained for the samples with low V content (<1 wt%), whereas the V-rich samples (i.e. >5 wt%) exhibited the presence of isolated vanadium and also of polynuclear surface species. The resulting V-bearing samples contain the Brønsted and Lewis acidic centres evidenced by FTIR spectra of adsorbed pyridine and by catalytic activity for 2-propanol decomposition and cumene cracking. Ammonia TPD allowed to estimate the number and strength of acid sites in regards to the vanadium content. Propene oxidation with N₂O revealed noticeable activity of the synthesised V-SBA-3 samples in epoxidation reaction. On the basis of TOF analysis indicating the activity of particular vanadium ions it seems that not all of the introduced V atoms take part in the formation of mild electrophilic oxygen species responsible for propene oxide formation.

Efficient SBA-3 vanadosilicate catalysts for propene oxidation obtained for the first time by the one-pot synthesis.

Textural and morphology changes of mesoporous SBA-15 silica due to introduction of guest phase

The research focuses on study of guest phase effect on the surface area and pore volume of SBA-15 with the emphasis on elucidation of reasons for these changes. The changes of surface area and pore volume are evident from evaluated N2 adsorption isotherms of VOx-SBA-15 even for samples with relative low content of supported guest phase, which is “atomically” spread on the surface in the form of anchored monomeric vanadyl species. These species cannot block the pore with diameter of 10 nm, nevertheless the presence of such phase causes decrease in adsorbed nitrogen during physisorption. Comparison of guest phase amount with differences in adsorbed amount of nitrogen led to conclusion that each vanadyl complex prevents adsorption of about one or two N2 molecules in the layer and influences two adsorption layers. Significant pore blocking occurs in the VOx-SBA-15 materials only in the case of presence bulk oxide-like nanospecies. Re-structuralization of silica mimicking phase separation phenomena relying on spinodal decomposition of a system was observed by SEM/TEM analysis and adsorption isotherms inspection for materials with high vanadium content.

Synthesis and catalytic performance in the propene epoxidation of a vanadium catalyst supported on mesoporous silica obtained with the aid of sucrose

Sucrose is an effective template for mesoporous silica—an efficient support of vanadium catalysts, active in propene epoxidation to propylene oxide.

One-pot, two-step conversion of alkynes to α-amino (α,α-diamino) ketones with a DMF-activated N-bromoimide strategy

A simple, one-pot, two-step cascade reaction for the synthesis of α-amino ketones has been developed.

Gas phase dehydration of glycerol catalyzed by gamma Al2O3 supported V2O5: a statistical approach for simultaneous optimization

Selective gas-phase dehydration of glycerol to acrolein over V₂O₅/γ-Al₂O₃ catalysts was investigated.

Partial oxidation of ethylbenzene by H2O2 on VOx/HZSM-22 catalyst

Highly dispersed extra-framework vanadium species mainly led to the oxidation of EB with 17.5% yield and 72.5% selectivity to AP.

The effect of redox properties of ceria-supported vanadium oxides in liquid phase cyclohexene oxidation

In the presence of redox catalysts, cyclohexene oxidation leads to an epoxidation product, while in the presence of acidic features; the allylic oxidation is predominant and leads to cyclohexenol and cyclohexenone.

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

High-quality spherical V-MCM-48 catalysts were successfully synthesized and showed higher catalytic activity for the selective oxidation of styrene to benzaldehyde.