NEXAFS Characterization and Reactivity Studies of Bimetallic Vanadium Molybdenum Oxynitride Hydrotreating Catalysts

Abstract

The surface and bulk compositions of vanadium molybdenum oxynitride (V 2 MoO 1.7 N 2.4 ), prepared by temperature-programmed reaction (TPR) of vanadium molybdenum oxide (V 2 MoO 8 ) with ammonia, have been characterized using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS data were recorded at the K-edges of nitrogen and oxygen, the L-edge of vanadium, and the M-edge of molybdenum. The nitrogen K-edge region of V-Mo oxynitride shows the characteristic NEXAFS features of early-transition-metal nitrides, although these features are different from those of either VN or Mo 2 N. Furthermore, comparison of the electron yield and fluorescence yield measurements also reveals that the oxidation state is different for vanadium near the surface region and for vanadium in the bulk, which is estimated to be 2.8 ( 0.3 and 3.8 ( 0.3, respectively. The oxidation state of bulk molybdenum is also estimated to be 4.4 ( 0.3. The X-ray diffraction pattern shows that the bulk phase of the bimetallic oxide is different from the pure monometallic oxide phases but the oxynitride has a cubic structure that resembles the pure vanadium and molybdenum nitride phases. The V-Mo oxide as prepared shows a preferential orientation of [001] crystallographic planes which is lost during the nitridation process. This shows that the solid state transformation V 2 MoO 8 f V 2 MoO 1.7 N 2.4 is not topotactic. The hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and hydrodeoxygenation (HDO) activities of V-Mo oxynitride are also compared to those of either VN or Mo 2 N catalysts. The bimetallic V-Mo oxynitride catalyst shows higher HDS, HDN, and HDO activities than those of the monometallic nitride catalysts.

AuN films - structure and chemical binding

“…The analysis theta/2theta (diffraction pattern) and omega/2omega (rocking curves) geometries and parallel beam with 40 kV voltage and 30 mA current were performed; all data are shown in Table . The stress and crystallite sizes of the samples were determined using Scherrer equation: where β t is the total broadening of the diffraction line, ε is the microstrain, β o is the instrumental broadening [calculated from the quartz calibration standard using topas r software (Bruker, Billerica, MA, USA) and Rietveld method, which gave a value of approximately 0.03514 °], D is the crystallite size, λ is the wavelength of the ion gun (0.1540 nm), and θ is the Bragg diffracted angle.…”

“…A 400.4‐eV binding energy was assigned to the formation of carbonitrides and oxynitrides. Moreover, this species is usually obtained using a plasma‐assisted system . Figure shows the N1s narrow spectrum of sample M11.…”

“…The analysis theta/2theta (diffraction pattern) and omega/2omega (rocking curves) geometries and parallel beam with 40 kV voltage and 30 mA current were performed; all data are shown in Table 2. The stress and crystallite sizes of the samples were determined using Scherrer equation: [19,20]…”

“…Moreover, this species is usually obtained using a plasma-assisted system. [19,25] Figure 2 shows the N1s narrow spectrum of sample M11. The observed low intensity of the N1s peak compared with sample M2 indicates a lower N 2 content, and the deconvolution of the spectra was not possible because the background signal is equal to the peak position.…”

Periodic DFT Study on the Adsorption and Catalytic Desulfurization of Thiophene over VC(001) and VN(001) via Hydrogenation and Direct Pathways

“…The PDOS (Figure ) of the VC(001) surfaces projected onto the V 3d states shows that the metallic states are important for the molecule–surface interaction. The interaction between V 3d and surface C 2p states characterized by low energy states within the range from −4 to −2 eV is attributed to chemical bonds between the V and C atoms. , The V 3d states fall mainly in the Fermi level vicinity for the clean surface. After the thiophene adsorption, the density of the states around the Fermi level has been slightly perturbed.…”