Chromium-based MIL-101 Research Articles

Green and efficient oxidative desulfurization of refractory S-compounds from liquid fuels catalyzed by chromium-based MIL-101 stabilized MoOx catalyst

In this work, MoOx/MIL-101(Cr) a new composite material, involving the collaboration of MoOx and MIL-101(Cr) to remove the refractory S-compounds (RSCs) from fuels via oxidative desulfurization (ODS) process were successfully synthesized. The prepared catalyst was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), powder X-ray diffraction (P-XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), fourier transform infrared spectroscopy (FT-IR), N2 sorption measurement (BET) and X-ray photoelectron spectroscopy (XPS). The prepared MoOx/MIL-101(Cr) was applied for the ODS of model fuel oil and showed the remarkably catalytic activity for the removal of RSCs from model fuel oil via oxidation. In addition, the effect of Mo-loading amount, H2O2/sulfur (O/S) molar ratio, and reaction temperature on the ODS reactivity were investigated. To explore the specific reaction mechanism of ODS over the MoOx/MIL-101(Cr), the effect of radical scavengers on ODS activity was examined. The radical scavengers experiments showed that the present oxidation reaction occurred through a radical mechanism involving the formation of •OH and •O2͞ species. In addition, it was found that the ODS efficiency is majorly related to the Mo5+ species forming with electron transfer to Mo6+ ion from Lewis acid sites of MIL-101(Cr). Furthermore, the MoOx/MIL-101(Cr) catalyst possesses recycling performance and remarkable stability, and even after five recycles, the removal of DBT was >94.8%. Hence, it could be confirmed that MoOx/MIL-101(Cr) is very useful in the ODS to remove RSCs from fuels in the presence of H2O2.

Highly efficient and selective one-pot tandem imine synthesis via amine-alcohol cross-coupling reaction catalysed by chromium-based MIL-101 supported Au nanoparticles

One-pot tandem synthesis of imines from alcohols and amines is regarded as an effective, economic and green approach under mild conditions. In this work, Au nanoparticles (NPs) dispersed on MIL-101 (Au/MIL-101) were demonstrated as highly active and selective bifunctional heterogeneous catalyst for production of various imine derivatives with excellent yields, via amine-alcohol cross-coupling reaction at 343 K in an open flask under an Ar atmosphere. Various physicochemical techniques, including inductively coupled plasma optical emission spectroscopy (ICP-OES), powder X-ray diffraction (P-XRD), X-ray photoelectron spectroscopy (XPS) transmission electron microscopy (TEM) and N2 adsorption-desorption, were used to characterize of the Au/MIL-101 catalyst. The obtained bifunctional catalyst is highly active and selective towards one-pot imine formation and exhibited the highest TOF (30.15-51.47 h−1) among all the ever-reported MOF-supported Au catalysts. The reaction mechanism of the imine formation from alcohol and amine over Au/MIL-101 catalyst was proposed. Mechanism experiment results demonstrate that Au NPs highly effective in activating oxidation of benzyl alcohol to benzaldehyde while the Lewis acid sites on MIL-101 catalyzed the second condensation step without interfering with the oxidation step. As a result, the excellent catalytic performance of Au/MIL-101 can be ascribed to the synergistic effect between Au NPs with Lewis acid sites in MIL-101.

Chromium-based MIL-101 metal organic framework as a fully regenerable D4 adsorbent for biogas purification

In this work, the chromium-based MIL-101 metal organic framework has been synthesized and investigated as a fully regenerable, high capacity sorbent for siloxanes, which are common contaminants in raw biogas from anaerobic digestion. Adsorption isotherms of D4, the most common siloxane in waste treatment plants, have been collected at different temperatures and modelled by means of the Langmuir theoretical isotherm. The selected metal organic framework shows a remarkable affinity for siloxane adsorption and an outstanding saturation capacity weakly dependent on temperature. Moreover, repeated adsorption isotherms, collected after a reactivation treatment of the same adsorbent sample, clearly indicate full regeneration capabilities. Considering that chromium-based MIL-101 is also a noticeable H2S adsorbent, the results reported in this work pave the way to its potential application for the simultaneous removal of the two main poisoning compounds contained in biogas.

Use of a Metal Organic Framework for the Adsorptive Removal of Gaseous HCl: A New Approach for a Challenging Task.

In this work, the potentialities of the amino-functionalized, chromium-based MIL-101 metal organic framework (NH2-MIL-101) as a high capacity, fully regenerable hydrogen chloride adsorbent have been proved by a thorough adsorption thermodynamics investigation. The chosen adsorbent showed high gaseous HCl adsorption capacities and, to the best of our knowledge, it is the first example of a totally regenerable substrate for this kind of adsorbate, as evidenced by both experimental and modeling results. This paves the way to the implementation of greener, more energetically efficient pressure/temperature swing adsorption processes to purify biogas feeds for high-temperature fuel cells.

Enhanced Adsorption Performance of Aromatics on a Novel Chromium-Based MIL-101@Graphite Oxide Composite

Chromium-based MIL-101 and graphite oxide (GO) composite (MIL-101@GO) was synthesized and applied for adsorption performances toward a series of aromatics (benzene, toluene, and ethylbenzene). Desorption activation energies of aromatics on this composite were evaluated based on temperature-programmed desorption (TPD) experiments. The results indicated that the aromatic uptakes on the composite increase with the carbon number at low pressure. In contrast, at high pressure, their adsorption capacities exhibit an opposite trend. The composite possesses high uptakes of the aromatics, which are approximately 1.8–6.0 times higher compared with conventional adsorbents. The desorption activation energies of the aromatics increase with the carbon number of aromatics. Additionally, the adsorption of ethylbenzene on the composite is highly reversible. More importantly, the MIL-101@GO composite exhibits enhanced thermal conductivity up to 0.369 W/mK at 303 K. The MIL-101@GO composite with high adsorption capacity, en...

Parametric Study of Hydrogen Sulfide Adsorption on Chromium-Based MIL-101 in a Fixed-Bed

Parametric Study of Hydrogen Sulfide Adsorption on Chromium-Based MIL-101 in a Fixed-Bed

Experimental Measurement of the Adsorption Equilibrium and Kinetics of CO2 in Chromium-Based Metal-Organic Framework MIL-101

A series of MIL-101 samples with hierarchical pore structures and different surface areas (2000-4800 m2/g) was synthesized by hydrothermal method and characterized by X-ray diffraction, thermogravimetric analysis and 77-K N2 adsorption isotherm. The adsorption equilibrium and kinetics of CO2 were studied at 288, 298 and 308 K within a pressure range of 0-5 MPa by a volumetric method. The adsorption heat, mass-transfer constant, diffusion coefficient and diffusion activation energy were also investigated in this work. The results showed that the chromium-based MIL-101 adsorbent exhibited an impressive selectivity for CO2 over N2, and had an adsorption capacity of 20 mmol/g of CO2 at 298 K and 5.0 MPa, which was much better than that of other conventional adsorbents (e.g. SBA-15, MCM-41, SG-A). The adsorption heat of CO2 on MIL-101 was in the range of 21-45 kJ/mol, which decreased with the loading of CO2. The mass-transfer constants and diffusion coefficients increased with the temperature and decreased wit...