Addition of low quantities of ytterbium to sol–gel prepared Ni/γ-Al2O3 catalysts has been shown to lead to significant increases in catalytic activity and long term stability in the catalytic ...conversion of CO2 and CH4 into syngas (H2 and CO). The role of ytterbium in these catalysts was investigated in this study through detailed investigations on the structure and composition of ytterbium promoted Ni/γ-Al2O3 catalysts using the following techniques: synchrotron X-ray diffraction, X-ray Photoemission Spectroscopy, Transmission Electron Microscopy, Scanning Electron Microscopy/Energy Dispersive X-ray analysis, Temperature Programmed Reduction techniques and N2 adsorption–desorption isotherms. The results obtained indicated that ytterbium, at small quantities (up to 2 wt%), interacted strongly with the support which in turn altered the interaction between nickel and the support (most notably it was found to completely inhibit the formation of NiAl2O4). This decreased interaction between Ni and the support also led to a higher quantity of Ni being present in the catalyst in the form of Ni.
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•Extensive characterisation data for Yb doped Ni-γ-Al2O3 catalysts.•Yb doping had a significant influence on microstructural characteristics.•Small quantities of Yb led to decreased formation of NiAl2O4.•Yb doping leads to a higher amount of free Ni.
We conducted a phase III, non-inferiority trial comparing safety and efficacy of RCP recombinant spike protein Covid-19 vaccine to BBIBP (Sinopharm).
Adult Iranian population received RCP or BBIBP in ...a randomized, double blind and an additional non-randomized open labeled trial arms. Eligible participants signed a written informed consent and received two intramuscular injections three weeks apart. In the randomized arm, an intranasal dose of vaccine or adjuvant-only preparation were given to the RCP and BBIBP recipients at day 51 respectively. Participants were actively followed for up to 4 months for safety and efficacy outcomes. Primary outcome was PCR + symptomatic Covid-19 disease two weeks after the second dose. The non-inferiority margin was 10% of reported BBIBP vaccine efficacy (HR = 1.36).
We recruited 23,110 participants (7224 in the randomized and 15,886 in the non-randomized arm). We observed 604 primary outcome events during 4 months of active follow-up including 121 and 133 in the randomized and 157 and 193 cases in the non-randomized arms among recipients of RCP and BBIBP respectively. Adjusted hazard ratios for the primary outcome in those receiving RCP compared with BBIBP interval were 0.91 (0.71–1.16) and 0.62 (0.49–0.77) in the randomized and non-randomized arms respectively. The upper boundary of 99.1% confidence interval of HR = 0.91 (0.67–1.22) remained below the margin of non-inferiority in the randomized arm after observing the early stopping rules using O'Brien Fleming method.
Our study showed that the RCP efficacy is non-inferior and its safety profile is comparable to the BBIBP.
•In a phase III, randomized, double blind non-inferiority trial we compared Razi-Cov Pars (RCP) covid-19 vaccine to BBIBP.•RCP recombinant vaccine efficacy is non-inferior and its safety profile is comparable to the BBIBP inactivated vaccine.•Estimated vaccine efficacy for prevention of symptomatic Covid-19 infection was 75.5% (95% CI: 51.8–87.7).
The sorption of phosphorus (in the form of phosphate species) was investigated using lanthanide functionalised mesoporous KIT-6. Thirteen lanthanide functionalised KIT-6 materials were prepared and ...studied (La/KIT-6, Ce/KIT-6, Pr/KIT-6, Nd/KIT-6, Sm/KIT-6, Eu/KIT-6, Gd/KIT-6, Tb/KIT-6, Dy/KIT-6, Ho/KIT-6, Er/KIT-6, Tm/KIT-6, and Yb/KIT-6). The prepared materials were characterised using Small Angle X-Ray Scattering, X-Ray Diffraction, BET surface area analysis, HRTEM and electrostatic Zeta potential. Phosphate sorption tests using the prepared materials showed the La (22.76 mg/g), Pr (22.71 mg/g), Nd (22.45 mg/g), Yb (21.91 mg/g) and Sm (20.57 mg/g) functionalised KIT-6 materials achieved the highest sorption capacities under the conditions used (Temp. 25 °C, P conc. 22.80 mg/L, stirring rate 120 rpm, sorbent concentration 0.1 g/mL, in 6h). The higher capacities obtained with these materials were most likely due to a combination of the relatively higher basicity of these materials combined with their relatively low surface charge. The capacities were also most likely influenced by the differences in solubility between the lanthanide phosphates that could form due to chemisorption. Investigations on the influence of other anions (chloride, sulphate, nitrate, and bicarbonate) on phosphate removal showed that only bicarbonate had a significant negative effect on phosphate sorption for all the materials studied.
The main finding from this research was that the surface zeta potential of the materials studied had a strong influence on phosphate adsorption.
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•Comparison of lathanide supported KIT-6 materials for adsorption of phosphate.•Strong correlation between phosphate adsorption and zeta potential of materials studied.•Excellent phosphate removal using.
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•Catalyst geopolymers could utilize for the de-pollution of surrounding environment.•Recent progress in substituting concrete & substrates with geopolymers is discussed.•The review ...highlight studies used waste materials for catalyst geopolymer synthesis.•Agricultural and industrial wastes have been identified as potential resources.•Opportunities and Challenges remaining for a wider use are discussed.
Air pollution and water pollution are critical issues because they negatively affect ecosystem and human health, as well as affecting buildings and industries. Utilizing photocatalysts that rely on light irradiation to decompose pollutants is a promising solution to this issue. Geopolymers, when used as a green substitute for cement and other engineered materials, can be synthesized using different agricultural and industrial wastes. These materials exhibit synergies in the depollution process and can be regarded as cost effective and novel in the context of removing organic pollution from water and air to protect and improve the environment. Geopolymer catalytic performance is closely linked to the composition, microstructure, and preparation method of the geopolymer. This review investigates the types of geopolymers and catalysts and their corresponding preparation methods and performances. The limitations of these products and future works are also detailed.
Applying metallic interlayer between diamond-like carbon (DLC) and substrate is a promising method to improve the adhesion and efficiency of DLC films. Understanding how the interlayer parameters ...affect the properties of DLC coatings leads to production of long-time excellent performance of them. In this study, DLC films deposited by PECVD and 10, 20 and 40 nm layers of Ni and Cr were sputtered on silicon substrates to use as the adhesion layers. The role of chemical structure and physical parameters (surface roughness) of interlayers on the final properties of DLC films were investigated using atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nanoscratch and nanoindentation techniques. It was found that a lower surface roughness with a sharp and homogenous distribution of particles sizes (height) results in formation of a smooth DLC film with lower friction coefficient, more stress reduction and better adhesion strength. It was discussed that the chemical structure of the interlayer was important in the solubility and diffusion of carbon atoms and consequently in instability of sp3 and sp2 bonding. Results demonstrated that 40 nm Cr interlayer, not only improved the adhesion of the DLC films but also generated the lowest friction coefficient, better wear resistance and the highest hardness (27 GPa).
Motivated by the significant scope which exists to generate value-added products from agricultural waste materials, in this work a comprehensive study was performed on the microstructure of ...alkali-treated coconut coir in order to evaluate its potential as an environmentally friendly absorbent. By investigating the influence of the alkali concentration, temperature and treatment time through a systematic Design of Experiments (DOE) approach, it was found that alkali-treated coconut coir possessed greatly improved water and moisture absorption properties (27% and 30% increases, respectively, compared to those of untreated coconut coir). The efficiency of heavy metal removal of treated coconut coir samples has been studied by investigating Cu (II) removal performance of selected samples with higher water and moisture absorbency. The effect of contact time and concentration of Cu (II) on the Cu (II) removal efficiency of samples have been investigated. The results show almost five times higher Cu (II) removal performance for the treated sample compared to raw coconut coir under optimized conditions. These findings highlight that the alkali treatment of biomaterials such as coconut coir can be used to tailor their water-absorbency properties as well as their adsorption properties, providing facile and effective adsorbent materials from readily available agricultural waste materials.
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•Detailed characterization of alkali treated coconut coir (CC) samples was performed.•Optimized sample showed 27% and 30% improved water and moisture absorbency.•Treated CC with various water absorbency could utilize for different applications.•Treated CC shows almost five times higher Cu (II) removal performance.
The paper assesses the influence of cooling medium on synthesis of detonation nanodiamond by detonation of high explosive mixtures. X-ray diffraction and surface analysis measurements of synthesized ...samples were performed to investigate the role of the environment of chamber on the efficiency of the detonation nanodiamond production in this method. The X-ray line broadening was used to evaluate the peak profiles of diamond nanoparticles and their corresponding average crystallite sizes. The results indicated that the amount of detonation nanodiamond decreased with the heat capacity of the medium in the detonation chamber.
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•To improve human comfort the desiccant cooling system has received much attention.•Desiccant materials have crucial effect on performance of desiccant cooling systems.•Composition, ...microstructure and preparation methods are most important parameters.•Carbon based desiccant materials have a significant potential for future research.•Limitations & recommendations towards developing desiccant materials are discussed.
A desiccant cooling system is among the best options to overcome future energy demand issues while considering human comfort by its ability to control both temperature and humidity. Although desiccant materials remarkably affect the performance of desiccant-based cooling systems, most studies focus on the design. This paper presents a review of the recent investigations on advanced desiccant materials regarding the improvement of the material properties for desiccant cooling application, emphasizing other important parameters, such as environmental conditions, cost, and design to achieve optimal performance. The preparation and performance of silica- and carbon-based desiccant materials are discussed. The current most suitable desiccant materials under different conditions for desiccant air conditioning systems and suggestions for future works are presented.
•Ionic radius of promoter affects the morphology of support and Ni–Al2O3 interaction.•The morphology of support was found to effect the initial activity of the catalyst.•The degree of Ni–Al2O3 ...interaction affects catalyst reducibility and Ni0 size.•The Ni0 size influenced the type of carbon on the catalysts and catalyst stability.
The present work was undertaken to investigate the effect of different lanthanide promoters on the structure–activity properties of Ni/γ-Al2O3 catalyst for CO2 reforming of CH4. Accordingly, a number of lanthanides, namely Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm were incorporated into the Ni/γ-Al2O3 catalyst by means of sol–gel method. An extensive physicochemical characterisation was performed using XRD, TG-DTA, BET surface area, BJH, XPS, Raman, H2-TPR, and TEM techniques. Surprisingly, low initial conversions of CH4 and CO2 were obtained for promoted Ni/γ-Al2O3 catalysts compared with un-promoted catalyst, which is due to the presence of smaller pore sizes in the promoted catalysts. The observed initial activity order for conversions of CH4 and CO2 is un-promoted >Eu>Tb>Ho>Tm>Er>Dy>Pr>Sm>Gd>Nd. Interestingly, promoted Ni/γ-Al2O3 catalysts exhibited an outstanding efficiency in time-on-stream studies up to 60h than the un-promoted catalyst. This significant observation is mainly due to low amounts of amorphous coke deposited on the surface of promoted Ni/γ-Al2O3 catalysts compared with un-promoted catalyst. Among all investigated lanthanides, the Er-promoted Ni/γ-Al2O3 catalyst showed the best performance in CH4 conversion, which is attributed to optimum Ni particle size, more reducibility, and low amounts of amorphous coke formation. It was shown that the catalytic efficacy of Ni/γ-Al2O3 catalysts is highly dependent on the nature of the promoter. These notable findings are expected to bring new opportunities in the design of novel promising catalytic materials for CO2 reforming of CH4.
Abstract
This work reports the development of a synergistic nanostructured MnO
x
/TiO
2
catalyst, with highly dispersed MnO
x
nanoparticles (4.5±1 nm) on shape‐controlled TiO
2
nanotubes (8–11 nm ...width and 120–280 nm length), for selective synthesis of valuable aromatic imines at industrially important conditions. Pristine TiO
2
nanotubes exhibited 97 % imine selectivity at a 38.3 % benzylamine conversion, whereas very low imine selectivity was obtained over commercial TiO
2
materials, indicating the catalytic significance of shape‐controlled TiO
2
nanotubes. The MnO
x
nanoparticle/TiO
2
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 MnO
x
/TiO
2
nanotubes was attributed to higher number of redox sites (Mn
3+
), high dispersion of Mn species, and shape‐controlled structure of TiO
2
, indicating that this catalyst could be a promising candidate for selective oxidation reactions.
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