Deep Oxidative Desulfurization of Planar Compounds Over Functionalized Metal-Organic Framework UiO-66(Zr): An Optimization Study.

This study aims to determine the catalytic activity and stability of ligand-modified UiO-66 with different functional groups (-NO2, -OH) in deep oxidative desulfurization from a model fuel (MF). The planar sulfur compounds included dibenzothiophene (DBT), 2-methylbenzothiazole (2-MB), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in n-dodecane as the fuel phase. The synthesized functionalized metal-organic framework (MOF) samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), nitrogen adsorption-desorption analysis, and microwave plasma-atomic emission spectrometer (MP-AES). The experiment assessment and desulfurization reaction optimization were carried out by the central composite design methodology. Response surface methodology and analysis of variance were employed to evaluate the individual process factors, their interactions, and sulfur removal responses. The responses showed that the oxidation of the planar compounds declined following the sequence DBT > 2-MB ≫ 4,6-DMDBT for all the MOFs. The findings revealed that at 66.7 °C, 3.0 equiv of oxidative agent over sulfur and 9.7 of MOF over sulfur by weight achieved the highest removal efficiency of 98.68% DBT, 93.23% 2-MB, and 69.32% 4,6-DMDBT for UiO-66-NO2 as a catalyst from the model fuel. It was also observed that UiO-66-NO2 had a higher efficiency in deep oxidative desulfurization when compared to other UiO-66-based catalysts used in the current study. Under optimal conditions, all the MOFs showed acceptable catalytic activity and reusability after four runs, although gradual loss of activity was observed.

Process Optimization for Catalytic Oxidation of Dibenzothiophene over UiO-66-NH2 by Using a Response Surface Methodology.

This research investigates the catalytic performance of a metal-organic framework (MOF) with a functionalized ligand-UiO-66-NH2-in the oxidative desulfurization of dibenzothiophene (DBT) in n-dodecane as a model fuel mixture (MFM). The solvothermally prepared catalyst was characterized by XRD, FTIR, 1H NMR, SEM, TGA, and MP-AES analyses. A response surface methodology was employed for the experiment design and variable optimization using central composite design (CCD). The effects of reaction conditions on DBT removal efficiency, including temperature (X 1), oxidant agent over sulfur (O/S) mass ratio (X 2), and catalyst over sulfur (C/S) mass ratio (X 3), were assessed. Optimal process conditions for sulfur removal were obtained when the temperature, O/S mass ratio, and C/S mass ratio were 72.6 °C, 1.62 mg/mg, and 12.1 mg/mg, respectively. Under these conditions, 89.7% of DBT was removed from the reaction mixture with a composite desirability score of 0.938. From the results, the temperature has the most significant effect on the oxidative desulfurization reaction. The model F values gave evidence that the quadratic model was well-fitted. The reusability of the MOF catalyst in the ODS reaction was tested and demonstrated a gradual loss of activity over four runs.

Cubic Iron Core-Shell Nanoparticles Functionalized to Obtain High-Performance MRI Contrast Agents.

Nanoparticles with SiO2 coating were synthesized to have a cubic iron core. These were found to have saturation magnetization very close to the highest possible value of any iron-containing nanoparticles and the bulk iron saturation magnetization. The in vitro toxicology studies show that they are highly biocompatible and possess better MRI contrast agent potential than iron oxide NPs.

CaH2-assisted low temperature synthesis of metallic magnetic nanoparticle-loaded multiwalled carbon nanotubes.

We studied synthesis of Ni or Fe nanoparticle-loaded multiwalled carbon nanotubes (MWCNTs) by pyrolyzing metal organic salts with CaH2, a very strong reductant. The use of CaH2 lowered the formation temperature of MWCNTs down to 400 °C without the use of toxic halogen-containing precursors and assistance of plasma.

Sr2FeO3 with stacked infinite chains of FeO4 square planes.

The synthesis of Sr2FeO3 through a hydride reduction of the Ruddlesden-Popper layered perovskite Sr2FeO4 is reported. Rietveld refinements using synchrotron and neutron powder diffraction data revealed that the structure contains corner-shared FeO4 square-planar chains running along the [010] axis, being isostructural with Sr2CuO3 (Immm space group). Fairly strong Fe-O-Fe and Fe-Fe interactions along [010] and [100], respectively, make it an S = 2 quasi two-dimensional (2D) rectangular lattice antiferromagnet. This compound represents the end-member (n = 1) of the serial system Sr(n+1)FenO(2n+1), together with previously reported Sr3Fe2O5 (n = 2) and SrFeO2 (n = ∞), thus giving an opportunity to study the 2D-to-3D dimensional crossover. Neutron diffraction and Mössbauer spectroscopy show the occurrence of G-type antiferromagnetic order below 179 K, which is, because of dimensional reduction, significantly lower than those of the other members, 296 K in Sr3Fe2O5 and 468 K in SrFeO2. However, the temperature dependence of magnetic moment shows a universal behavior.

Carboxylated SiO2-coated α-Fe nanoparticles: towards a versatile platform for biomedical applications.

Carboxylated SiO2-coated α-Fe nanoparticles have been successfully prepared via CaH2-mediated reduction of SiO2-coated Fe3O4 nanoparticles followed by surface carboxylation. These α-Fe-based nanoparticles, which are characterized by ease of coating with additional functional groups, a large magnetization of 154 emu per g-Fe, enhanced corrosion resistivity, excellent aqueous dispersibility, and low cytotoxicity, have potential to be a versatile platform in biomedical applications.

Low temperature solventless synthesis and characterization of Ni and Fe magnetic nanoparticles.

We have successfully implemented a facile, one-pot solventless synthesis procedure starting from acetylacetonate salts and CaH(2) to obtain carbon-coated ferromagnetic metallic Ni and Fe nanoparticles at low temperature. The use of CaH(2) as a reductant drastically reduces reaction temperature down to 140 °C.

Fe-site substitution effect on the structural and magnetic properties in SrFeO2.

We investigated the Fe-site substitution effect on the structural and magnetic properties of the infinite layer iron oxide Sr(Fe(1-x)M(x))O(2) (M = Co, Mn) using synchrotron X-ray diffraction, neutron diffraction, and (57)Fe Mössbauer spectroscopy. Both systems have a similar solubility limit of x ≈ 0.3, retaining the ideal infinite layer structure with a space group of P4/mmm. For the Fe-Co system, both in-plane and out-of-plane axes decrease linearly and only slightly with x, reflecting the ionic radius difference between Fe(2+) and Co(2+). For the Fe-Mn system the lattice evolution also follows Vegard's law but is anisotropic: the in-plane axis increases, while the out-of-plane decreases prominently. The magnetic properties are little influenced by Co substitution. On the contrary, Mn substitution drastically destabilizes the G-type magnetic order, featured by a significant reduction and a large distribution of the hyperfine field in the Mössbauer spectra, which suggests the presence of magnetic frustration induced presumably by a ferromagnetic out-of-plane Mn-Fe interaction.