ABSTRACT
Bimetallic oxide is a potential catalyst for oxidative desulfurization of fuel. Thus, an appropriate method is needed to improve its catalytic performance. Manufacturing defect is an effective means. In this contribution, an oxygen vacancies (OVs) regulation strategy for enhancing the catalytic activity of bimetallic oxide is proposed. Density functional theory (DFT) calculations show that the crystal phase has a huge influence on the generation energy of oxygen vacancies, so a series of V-Nb mixed oxide with different crystal phases are synthesized. Detailed characterizations show that the as-prepared tetragonal V-Nb mixed oxide (T-VNbOx) has lower OVs formation energy and larger OVs concentration (compared to orthorhombic V-Nb mixed oxides, O-VNbOx). Owing to the activation of OVs, the catalytic activity of T-VNbOx was significantly enhanced to form ultra-deep oxidative desulfurization. In addition, T-VNbOx can be cycled eight times without significantly degrading the desulfurization performance.
ABSTRACT
Phosphomolybdate-based ionic liquid [(C8H17)3NCH3]3PMo12O40 was prepared and supported on a magnetic mesoporous silica (γ-Fe2O3@SiO2@mSiO2) to obtain a magnetic mesoporous catalyst. The morphology and components of the catalyst were characterized by FT-IR, XRD, XPS, SEM, TEM, nitrogen adsorption-desorption isotherms, and VSM. With air as oxidant, the catalyst showed perfect desulfurization performance in oxidation of dibenzothiophene (DBT). The removal of DBT from model oil could reach 100% within 5â¯h at 120⯰C. After reaction, the catalyst could be separated by a magnet and recycled at least four times without obvious decrease in the catalytic performance.
ABSTRACT
Hydrogen peroxide (H2O2) decomposition mechanism and its oxidative desulfurization activity on hexagonal boron nitride monolayer (h-BN) have been explored by density functional theory (DFT) at M06-2X/6-311 + G (d,p) level. A cluster model which contains seven rings has been constructed to simulate the h-BN surface. It is found that 7 possible species will be generated after the decomposition of H2O2. Among them, 2H*+O2* and 2H*+2O* are relatively unstable while other species, such as HOO*+H*, HO*+HO*, H*+HO + O*, H2O*+O* are relatively stable and may exist in the current system. In addition, 4 decomposition pathways have been explored. Results show that the H2O2* will first undergo an O-H bond break (HOO*+H*), then the HO-O bond decomposes into H*+HO*+O* (Pathway (b)). By considering the concentration and activation energy together, the H2O*+O* is proposed to be the most possible active species for oxidative desulfurization due to the relative higher concentration and lower activation energy.
Subject(s)
Boron Compounds/chemistry , Hydrogen Peroxide/chemistry , Oxidation-Reduction , Adsorption , Density Functional Theory , Molecular Conformation , Molecular Structure , Structure-Activity RelationshipABSTRACT
To obtain the adsorption strength is the key point for materials design and parameters optimization in chemical engineering. Here we report a simple but accuracy method to estimate the adsorptive energies by counting the number of π-orbital involved atoms based on theoretical computations for hexagonal boron nitride (h-BN) and graphene. Computational results by density function theory (DFT) as well as spin-component scaled second-order Møller-Plesset perturbation theory (SCS-MP2) both confirm that the adsorptive energies correlate well with the number of π-orbital involved atoms for π-orbital contained molecules. The selected molecules (adsorbates) are commonly used in chemical industry, which contains C, N, S, O atoms. The predicted results for the proposed formulas agree well with the current and previous DFT calculated values both on h-BN and graphene surfaces. Further, it can be also used to predict the adsorptive energies for small π-orbital contained molecules on BN and carbon nanotubes. The interaction type for these adsorptions is typical π-π interaction. Further investigations show that the physical origin of these interactions source from the polar interactions between the adsorbents and adsorbates. Hence, for separation or removal of aromatic molecules, how to modify the aromaticity and polarity of both adsorbents and adsorbates will be the key points for experiments.