The question remains over the role of the pore structure of the support material on the catalytic behaviour of Ni catalysts during the CO2/dry reforming of methane (DRM). For this reason, a series of ...mesoporous materials with different pore structures, namely MCM-41, KIT-6, tri-modal porous silica (TMS), SBA-15 and mesostructured cellular foams (MCFs) were synthesised via hydrothermal synthesis methods and further impregnated with 15 wt.% NiO (11.8 wt.% Ni). It was observed that synthesised TMS is a promising catalyst support for DRM as Ni/TMS gave the highest activity and stability among these materials as well as the Ni catalysts supported on classic ordered mesoporous silicates support reported in the literature at the relatively low temperature (700 °C). On the other hand, Ni supported on CMC-41 exhibited the lowest activity among them. To understand the reason for this difference, the physicochemical properties of these materials were characterised in detail. The results show that the thickness of the silica wall and the pore size of the support material play a critical role in the catalytic activity of Ni catalysts in the CO2 reforming of methane.
As part of the Glasgow Climate Pact, at COP27 in 2021, world leaders of 197 countries agreed to cut carbon dioxide emissions to prevent a “climate catastrophe” ...
This work reports the development of a synergistic nanostructured MnOx/TiO2 catalyst, with highly dispersed MnOx nanoparticles (4.5±1 nm) on shape‐controlled TiO2 nanotubes (8–11 nm width and 120–280 ...nm length), for selective synthesis of valuable aromatic imines at industrially important conditions. Pristine TiO2 nanotubes exhibited 97 % imine selectivity at a 38.3 % benzylamine conversion, whereas very low imine selectivity was obtained over commercial TiO2 materials, indicating the catalytic significance of shape‐controlled TiO2 nanotubes. The MnOx nanoparticle/TiO2 nanotube (10 wt% Mn) catalyst calcined at 400 °C showed the best activity with 95.6 % benzylamine conversion and 99.9 % imine selectivity. This catalyst exhibited good recyclability for four times and is effective for converting numerous benzylamines into higher yields of imines. The high catalytic performance of MnOx/TiO2 nanotubes was attributed to higher number of redox sites (Mn3+), high dispersion of Mn species, and shape‐controlled structure of TiO2, indicating that this catalyst could be a promising candidate for selective oxidation reactions.
Synergistic catalysis: An efficient catalytic strategy for synthesizing aromatic imines was reported over a nanostructured MnOx/TiO2 catalyst at industrially important conditions. The synergy between MnOx nanoparticles and TiO2 nanotubes led to improved catalytic properties, resulting in the highly selective synthesis of imines with good catalyst recyclability. This work can provide valuable insights for selective oxidation reactions.
Nickel–titanium (NiTi) nanoparticles are ultrafine smart materials manifesting shape memory effect at very small scales. We have produced NiTi nanoparticles surrounded by an amorphous carbon shell ...using an innovative spark discharge system. The resulting nanoparticles were studied using various characterization methods to systematically study their size, morphology, size distribution, composition, structure, and thermal behavior. Field-emission scanning electron microscopy and dynamic light-scattering results indicated that the average size of the produced nanoparticles was about 13 nm. High-resolution transmission electron microscopy, energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy showed that all of the particles had a titanium oxide coating covered with a ~ 2 nm-thick carbon layer. X-ray diffraction analysis demonstrated that the carbon and titanium oxide layers were amorphous and confirmed the formation of NiTi nanoparticles. Differential scanning calorimetry demonstrated an austenite to martensite phase transformation behavior in the produced nanoparticles and further indicated the formation of NiTi phases. EDS mapping showed an incomplete oxidation for nanoparticles suggesting that the amorphous carbon and titanium oxide layers synergistically act together as a combined protective layer. These results indicate that our novel spark discharge generator is an effective system for the synthesis of NiTi nanoparticles coated with a continuous film of carbon.
Graphical abstract
Shape-controlled metal nanomaterials are considered as a unique class of catalysts because of their synergistic size- and shape-dependent catalytic properties. This work reports the synthesis of a ...novel size- and shape-controlled catalyst, consisting of highly dispersed MnO
x
nanoparticles (average particle size of 4.5 nm) on shape-controlled SiO
2
nanospheres (250–300 nm) for selective cyclohexene oxidation using air as the oxidant under solvent- and base-free conditions. The MnO
x
/SiO
2
catalyst exhibited an excellent cyclohexene conversion (~ 92%) with a high selectivity (~ 96%) to the allylic products (2-cyclohexene-ol and 2-cyclohexene-one) under mild conditions, outperforming various SiO
2
supported CoO
x
, FeO
x
, and CuO
x
catalysts. The better performance of shape-controlled MnO
x
/SiO
2
nanocatalyst is due to high redox nature of Mn, uniform dispersion of smaller sized MnO
x
nanoparticles, and synergetic interaction between MnO
x
and SiO
2
spheres, as evidenced by XPS and TEM studies. Further, the MnO
x
/SiO
2
catalyst could be reused at least 5 times for selective cyclohexene oxidation with a negligible loss in its catalytic performance, indicating the excellent stability of shape-controlled metal nanocatalysts in organic synthesis under economically viable and mild conditions.
Graphic Abstract
Shape-controlled MnO
x
/SiO
2
nanocatalyst shows an excellent catalytic activity and a high selectivity to allylic products in the oxidation of cyclohexene under mild conditions
Nanostructured Ni-incorporated mesoporous alumina (MAl) materials with different Ni loading (7, 10 and 15 wt %) were prepared by a template assisted hydrothermal synthesis method and tested as ...catalysts for CO2 reforming of methane under different conditions (nickel loading, gas hourly space velocity (GHSV), reaction temperature and time-on-stream (TOS)). The most active catalyst tested (Ni(10 wt%)-MAl) showed a very high stability over 200 h compared to a Ni(10 wt%)/γ-Al2O3 prepared using a co-precipitation method which had a significant loss in activity after only ∼4 h of testing. The high stability of the Ni-MAl materials prepared by the template assisted method was due to the Ni nanoparticles in these catalysts being highly stable towards migration/sintering under the reaction conditions used (800 °C, 52,000 mL h−1 g−1). The low susceptibility of the Ni nanoparticles in these catalysts to migration/sintering was most likely due to a strong Ni-support interaction and/or active metal particles being confined to the mesoporous channels of the support. The Ni-MAl catalysts also had significantly lower amounts of carbon deposited compared to the catalyst prepared using the co-precipitation method.
► Nanostructured Ni-incorporated mesoporous alumina catalysts. ► Catalysts for CO2 reforming of methane under various conditions. ► Catalysts show high activity and stability over 200 h ► Ni nanoparticles confined to mesopores resistant to sintering and migration. ► Catalysts showed low inactive carbon deposition.
Pemphigus vulgaris (PV) is a chronic autoimmune disorder with potentially fatal outcomes. The aim of this study was to investigate the effect of l‐carnitine (LC) on secreted frizzled‐related ...protein‐5 (SFRP5), omentin, visfatin, and glycemic indices in PV patients under corticosteroid treatment. In this randomized, double‐blind, placebo‐controlled clinical trial, 52 patients with PV were divided randomly into two groups to receive 2 g of LC or a placebo for 8 weeks. Serum levels of SFRP5, omentin, visfatin, and also glycemic indices were evaluated at the baseline and end of the study. LC supplementation significantly decreased the serum level of visfatin (95% CI −14.718, −0.877, p = .05) and increased the serum levels of SFRP5 (95%CI 1.637, 11.380, p < .006) and omentin (95% CI 9.014, 65.286, p < .01). However, LC supplementation had no significant effects on the serum levels of glycemic factors such as insulin (95% CI −1.125, 3.056, p = .426), fasting blood sugar (95% CI −4.743, 3.642, p = .894), homeostatic model assessment of insulin resistance (95% CI −0.305, 0.528, p = .729), and quantitative insulin‐sensitivity check index (95% CI −0.016, −0.010, p = .81). LC supplementation decreased visfatin serum level and increased omentin‐1 and SFRP5 serum levels in patients with PV. However, it has no significant effect on the serum levels of insulin and glycemic indices.
Geopolymer is a promising porous material that can be used for evaporative cooling applications. Developing a greener geopolymer using agricultural and industrial wastes is a promising research area. ...In this study, we utilize rice husk (RH), rice husk ash (RHA), metakaolin (MK), ground granulated blast furnace slag (GGBS), and palm oil fuel ash (POFA) to prepare geopolymer pastes, with alkali liquid as an activator. Many geopolymer samples have been prepared as per the Design of Experimental software (DOE), and its corresponding response surface mode and central composite design and later they were characterized. The samples were cured in an oven for 2 h at 80 °C, and thereafter stored at room temperature (~25–30 °C) prior to being tested for its water absorption and compressive strength. The effect of the different composition of precursors on water absorption, density, porosity, and the compressive strength of the prepared geopolymers have been investigated. The results showed that the compressive strength of geopolymers is directly proportional to the ratio of the alkali liquid. Post-optimization, the best geopolymer paste mixture was confirmed to contain 10% of RH, 15% RHA, 35% MK, 10% POFA and 30% of GGBS, with 72% desirability for maximum water absorption (~38%) and compressive strength (4.9 MPa). The results confirmed its applicability for evaporative cooling.
In this study, different chemically treated coconut coir (CC), local waste biomass, has been developed as an adsorbent for the removal of methylene blue (MB) from an aqueous solution. The acid and ...base treated coconut coir with higher water and moisture absorbency have been investigated for dye removal performance. The influence of different experimental factors such as initial MB concentration and condition of chemical treatments on dye removal performance of coconut coir were studied. The compositional and structural changes of the treated samples were determined using X-ray diffraction (XRD), scanning electron microscope (SEM), X-Ray photoelectron spectroscopy (XPS), Fourier Transform Infrared spectroscopy (FT-IR), and Thermogravimetric analysis (TGA). The best sample showed the removal percentage of methylene blue equal to % 92.36 and %91.62 in 0.05mM and 0.03 mM of MB, respectively. The results showed the simply modified cheap waste biomass could be used as an effective green adsorbent for dye removal in aqueous solution.
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