Low-angle X-ray Diffraction Research Articles

Synthesis, characterization, and novel reactivity of nano CeO2 catalyst for solvent-free Knoevenagel condensation

We synthesized the nano CeO2 using the sol-gel method and characterized the material using different techniques, including XRD, FT-IR, BET surface area, SEM, and TEM analysis. We tested the catalytic functionalities of nano CeO2 catalyst for Knoevengel condensation of different substituted benzaldehydes with malononitrile, which offered exceptional 95 % conversion and yield. The results support that nano CeO2 material significantly boosted the yield of the desired product compared to the bulk material. The low-angle XRD profile showed that the regenerated nanomaterial fully retained the porous nature and cubic structure of ceria. FT-IR results reveal that the characteristic vibrational IR band is at 720 cm−1, which is attributed to Ce–O–Ce stretching. The BET surface area result indicates that nano-ceria possesses a higher surface area than bulk CeO2 material. The SEM analysis illustrates cube-like morphology and TEM data show the nanorod-like appearance of ceria. The nanocatalyst exhibited stable and sustainable activity during regeneration up to 5 cycles.

Solar-driven calcination of clays for sustainable zeolite production: CO2 capture performance at ambient conditions

This study presents the environmentally sustainable synthesis of zeolites from solar-calcined kaolin and halloysite, emphasizing their application in CO2 capture due to their distinctive porous structures and chemical attributes. Expanding upon prior research that utilized solar energy for kaolin calcination, we now explore halloysite as an alternative clay mineral for zeolite production and CO2 capture. Employing a solar simulator, halloysite was calcined at temperatures ranging from 700 to 1000 °C, resulting in the synthesis of zeolites 4A and 13X via hydrothermal methods. The synthesized zeolites were characterized using X-ray diffraction (XRD), low angle XRD (LA-XRD), transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FE-SEM), and Brunauer–Emmett–Teller (BET) surface area measurements. Notably, the presence of Al-Si spinel, which crystallizes at elevated solar calcination temperatures, persisted within the zeolite 13X matrix, inducing a secondary mesoporous phase. The observed hysteresis in 13X samples, rather than confirming the mesoporous character of zeolite 13X, indicates a tandem effect of mesoporous Al-Si spinel with microporous zeolite 13X, exemplifying systems known as micro/mesoporous zeolitic composites (MZCs). The correlation obtained between the interplanar distances calculated from LA-XRD and pore size distributions acquired from the BJH desorption branches highlights LA-XRD as an alternative analysis method for assessing mesoporosity. While the microporosity of Al-Si spinel possessing 13X samples positively correlates with CO2 capture performance, mesoporosity appears to have minimal impact. Among the zeolites synthesized using solar energy, zeolite 4A (LTA) demonstrates superior CO2 capture capability, achieving an adsorption capacity of 2.15 mmol/g at 25 °C and 1 bar. This study highlights the potential of solar energy in producing eco-friendly zeolites from kaolin and halloysite for improved CO2 capture, advancing sustainable environmental solutions.

Pressure dependence of intermediate-range order and elastic properties of glassy Baltic amber.

Amber is a unique example of a fragile glass that has been extensively aged below its glass transition temperature, thus reaching a state that is not accessible under normal experimental conditions. We studied the medium-range order of Baltic amber by x-ray diffraction (XRD) at high pressures. The pressure dependences of the low-angle XRD intensity between 0 and 5 Å^{-1} were measured from 0 to 7.3 GPa by the energy-dispersive XRD. The first diffraction peak at 1.1 Å^{-1} and ambient pressure has a doublet structure consisting of the first sharp diffraction peak (FSDP) at 1.05 Å^{-1} and the second feature at 1.40 Å^{-1}. The peak position and the width of the FSDP increase as the pressure increases, while the intensity of the FSDP decreases. Below P_{0}=2.4 GPa, the rapid increase of the FSDP peak position was observed, while above P_{0}, the gradual increase was observed. Below P_{0}, voids and holes in a relatively low-density state are suppressed, whereas above P_{0}, the suppression becomes mild. Such a change suggests the crossover from the low- to high-density state at P_{0}. There is a close correlation between the pressure dependence of XRD and previously reported sound velocity results. The correlation between the mean-square fluctuation of the shear modulus on the nanometer scale and fragility in amber and other glass formers is also discussed.

Magnetic yolk-shell structured periodic mesoporous organosilica supported palladium as a powerful and highly recoverable nanocatalyst for the reduction of nitrobenzenes

A novel palladium-loaded yolk-shell structured nanomaterial with magnetite core and phenylene-based periodic mesoporous organosilica (PMO) shell (Fe3O4@YS-Ph-PMO/Pd) nanocatalyst was synthesized for the reduction of nitrobenzenes. The Fe3O4@YS-Ph-PMO/Pd was prepared through cetyltrimethylammonium bromide (CTAB) directed condensation of 1,4-bis(triethoxysilyl)benzene (BTEB) around Fe3O4@silica nanoparticles followed by treatment with palladium acetate. This nanocatalyst was characterized by using Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), low-angle and wide-angle powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) analyses. These analyses showed a magnetic nanomaterial with high chemical and thermal stability for the designed composite. The Fe3O4@YS-Ph-PMO/Pd nanocomposite was employed as a powerful and highly recoverable catalyst in the green reduction of nitroarenes in H2O at room temperature. A variety of nitroarene derivatives were applied as substrate in the presence of 0.9 mol% of Fe3O4@YS-Ph-PMO/Pd catalyst. All nitroarenes were selectively converted to their corresponding amines with high to excellent yields (92–96%) within short reaction times (10–18 min). This catalyst was recovered and reused at least 11 times without significant decrease in efficiency and stability.

Assessing the Acidic and Alkaline Recalcitrance of Covalently Modified Surface Amines on Ordered Mesoporous Carbon.

Ordered mesoporous carbon (OMC) scaffolds were covalently modified with primary amine groups by means of oxidation-coupling, yielding C-O-C bonds, or organometallic activation-coupling, yielding C-C bonds. The aminated OMCs were stressed by immersion in either 1 M hydrochloric acid or 1 M sodium hydroxide solutions at room temperature for 6 h and characterized by nitrogen sorption, electron microscopy, low-angle X-ray diffraction, thermogravimetric analysis, and the 4-nitrobenzaldehyde assay. Results demonstrate that aminated surfaces of OMC by butyllithium grafting are stable toward both 1 M HCl and 1 M NaOH, whereas the oxidation-aminated OMC surfaces can withstand 1 M NaOH only. This study illustrates the importance of chemical testing to supplant chemical intuition when tailoring carbon surfaces for applications where strong acids or bases are employed. This is especially emphasized for carbonaceous materials because of the surface heterogeneity among different carbon allotropes.

Fabrication of mesoporous titania films and kinetics of photoelectrocatalytic degradation of organic dye

Mesoporous titania films with worm-like patterns were fabricated on indium-tin oxide (ITO) glass by dip-coating skill, and were characterized systematically. Impacts of the process and technical parameters on the formation of the films were investigated. The mesoporous films were characterized by low-angle X-ray diffraction (XRD) and wide-angle XRD, transmission electron microscopy (TEM), scanning electron microscope (SEM), linear sweep voltammograms and nitrogen adsorption/desorption isotherms. Subsequently, the films were used in a photoelectrocatalytic system for the degradation of methyl orange. The influence of operation variables, including pH values, bias potential, light intensity, organics concentration and the mass of the films, on the degradation of the dye was investigated in details. More than 96 % degradation of the organics was achieved in 2 h. The kinetic results for the photoelectrocatalytic oxidation of the organic were also presented in this paper.

Improving the corrosion and wear resistance of CoCrNiSi0.3 Medium-Entropy Alloy by magnetron sputtered (CrN/Cr)x multilayer films

In this study, a medium entropy alloy (MEA) system consisting of Co, Cr, and Ni was selected to incorporate Si, resulting in the creation of CoCrNiSi0.3 MEA. The surface was coated with (CrN/Cr)x multilayer films to improve wear and corrosion resistance. The hardness, wear, corrosion, and nanoindentation tests were used to analyze the characteristics of CrN/Cr multilayer films and their protective performance. Low grazing angle X-ray diffraction (GIXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), water contact angle analyzer, and transmission electron microscopy (TEM) were utilized to investigate the composition and structure of (CrN/Cr)x multilayer films. The intermediate Cr layer inhibits the columnar growth of the CrN layers and is progressively refined as the number of CrN/Cr bilayers increases. The Cr layer exhibits superior toughness in the multilayer structure and effectively hinders crack propagation. Therefore, the (CrN/Cr)3 multilayer film has the most outstanding anti-wear performance. The wear rates under 2 N and 4 N loads are 3.331 × 10−6 mm3•m−1•N−1 and 1.124 × 10−5 mm3•m−1•N−1, respectively. The growth of columnar crystals is suppressed and a more compact multilayer film is formed, resulting in a reduction in the defect density and an increase in the water contact angle, which retards the ingress of corrosive liquid and improves corrosion resistance. The corrosion current density of the (CrN/Cr)3 multilayer film is 0.73 μA•cm−2, while the corrosion polarization impedance is 962.35 Ω•cm2.

Long-Range Hot-Carrier Transport in Topologically Connected HgTe Quantum Dots.

The utilization of hot carriers as a means to surpass the Shockley-Queasier limit represents a promising strategy for advancing highly efficient photovoltaic devices. Quantum dots, owing to their discrete energy states and limited multi-phonon cooling process, are regarded as one of the most promising materials. However, in practical implementations, the presence of numerous defects and discontinuities in colloidal quantum dot (CQD) films significantly curtails the transport distance of hot carriers. In this study, the harnessing of excess energies from hot-carriers is successfully demonstrated and a world-record carrier diffusion length of 15µm is observed for the first time in colloidal systems, surpassing existing hot-carrier materials by more than tenfold. The observed phenomenon is attributed to the specifically designed honeycomb-like topological structures in a HgTe CQD superlattice, with its long-range periodicity confirmed by High-Resolution Transmission Electron Microscopy(HR-TEM), Selected Area Electron Diffraction(SAED) patterns, and low-angle X-ray diffraction (XRD). In such a superlattice, nonlocal hot carrier transport is supported by three unique physical properties: the wavelength-independent responsivity, linear output characteristics and microsecond fast photoresponse. These findings underscore the potential of HgTe CQD superlattices as a feasible approach for efficient hot carrier collection, thereby paving the way for practical applications in highly sensitive photodetection and solar energy harvesting.

Mesoporous organosilicas with highly-content tyrosine framework as extractive phases for non-steroidal anti-inflammatory drugs in aquatic media

BackgroundAttentions regarding ordered mesoporous silica materials (OMSs), with large specific surface areas and narrow pore size distribution, which are prepared via self-assembly techniques, have been raised in sorption, separation, and sample preparation. However, in order to extend and improve their applications, a functionalization step is required. Organic units can be anchored on the inner or outer surface as well as in the silica wall framework by co-condensation-, grafting-, and periodic mesoporous organosilica (PMO) preparation approaches. Apparently, by synthesizing PMO with extensive and flexible organic bridging groups within the mesoporous wall, an efficient extractive phase can be achieved. ResultsWe employed tyrosine amino acid to synthesize a PMO-based extractive phase. The FT-IR, 1H NMR, HR-ESI-MS, Low angle-XRD, TEM, FESEM, BET, and EDX-MAP analyses confirmed the successful synthesis of PMO within the salt-assisted templating method. A comprehensive study on sorption behavior of PMO was performed and its efficiency was evaluated against the grafting and co-condensation methods. Then, it was implemented to the pipette tip-micro solid phase extraction (PT-μ-SPE) of widely used non-steroidal anti-inflammatory drugs (NSAIDs) in water/wastewaters. Limits of detection and quantification were obtained in the range of 0.1–1.5 and 0.3–5 μg L−1, respectively. The calibration plots are linear in the 1–1000, 3–1000, 10–750, and 3–750 μg L−1, respectively. The intra-and inter-day precision at 50 and 200 μg L−1 levels are 2.9–7.1 % and 3.5–8%, while recoveries are between 84 and 111 %. SignificanceHigh-capacity tyrosine functionalized PMO with 2D hexagonal symmetry silica mesoporous structures found to be highly efficient extractive media. Despite the bulkiness and flexibility of the bridging group within the mesoporous wall, the synthesis condition was optimized in order to load more organic content in the PMO structure. The PMO performance was superior over organically modified ordered mesoporous silica materials prepared by the grafting and co-condensation methods.

Preparation of berberine-naringin dual drug-loaded composite microspheres and evaluation of their antibacterial-osteogenic properties

To develop a drug-loaded composite microsphere that can simultaneously release the berberine (BBR) and naringin (NG) to repair infectious bone defects. The NG was loaded on mesoporous microspheres (MBG) to obtain the drug-loaded microspheres (NG-MBG). Then the dual drug-loaded compound microspheres (NG-MBG@PDA-BBR) were obtained by wrapping NG-MBG with polydopamine (PDA) and modifying the coated PDA with BBR. The composite microspheres were characterized by scanning electron microscopy, X-ray diffraction, specific surface area and pore volume analyzer, and Fourier transform infrared spectroscopy; the drug loading rate and release of NG and BBR were measured; the colony number was counted and the bacterial inhibition rate was calculated after co-culture with Staphylococcus aureus and Escherichia coli for 12 hours to observe the antibacterial effect; the biocompatibility was evaluated by live/dead cell fluorescence staining and cell counting kit 8 assay after co-culture with rat's BMSCs for 24 and 72 hours, respectively, and the osteogenic property was evaluated by alkaline phosphatase (ALP) staining and alizarin red staining after 7 and 14 days, respectively. NG-MBG@PDA-BBR and three control microspheres (MBG, MBG@PDA, and NG-MBG@PDA) were successfully constructed. Scanning electron microscopy showed that NG-MBG@PDA-BBR had a rough lamellar structure, while MBG had a smooth surface, and MBG@PDA and NG-MBG@PDA had a wrapped agglomeration structure. Specific surface area analysis showed that MBG had a mesoporous structure and had drug-loading potential. Low angle X-ray diffraction showed that NG was successfully loaded on MBG. The X-ray diffraction pattern contrast showed that all groups of microspheres were amorphous. Fourier transform infrared spectroscopy showed that NG and BBR peaks existed in NG-MBG@PDA-BBR. NG-MBG@PDA-BBR had good sustained drug release ability, and NG and BBR had early burst release and late sustained release. NG-MBG@PDA-BBR could inhibit the growth of Staphylococcus aureus and Escherichia coli, and the antibacterial ability was significantly higher than that of MBG, MBG@PDA, and NG-MBG@PDA ( P<0.05). But there was a significant difference in biocompatibility at 72 hours among microspheres ( P<0.05). ALP and alizarin red staining showed that the ALP positive area and the number of calcium nodules in NG-MBG@PDA-BBR were significantly higher than those of MBG and NG-MBG ( P<0.05), and there was no significant difference between NG-MBG@PDA and NG-MBG@PDA ( P>0.05). NG-MBG@PDA-BBR have sustained release effects on NG and BBR, indicating that it has ideal dual performance of osteogenesis and antibacterial property.

Imidazolium-Containing Hybrid Organic-Inorganic Materials for the Conversion of CO2: Unveiling the Key Role of the Ionic Template.

A straightforward synthesis of a series of hybrid organic-inorganic materials (HOIMs) containing imidazolium moieties was achieved. The preparation of the imidazolium acetate precursor was performed in a single-step procedure using the Debus-Radziszewski reaction. The as-synthesized alkoxysilane was employed in combination with tetraethyl orthosilicate to generate an HOIM presenting a high specific surface area. Two different structure-directing agents (SDAs), an anionic (sodium dodecyl sulfate (SDS)) or a cationic (cetyltrimethylammonium bromide) surfactant, were used to investigate the role played by the SDA on the distribution of the imidazolium-based active sites within the silica structure. After the synthesis, the acetate ion was replaced with Cl- and Br- via a simple acid treatment. This procedure favors also the removal of the surfactant, thus releasing the porosity of the solids. The HOIMs synthesized were fully characterized via low-angle X-ray diffraction, N2 physisorption, transmission electron microscopy, 13C and 29Si MAS NMR, combustion chemical analysis, X-ray photoelectron spectroscopy, and CO2 physisorption to assess their physicochemical and structural features, as well as the successful incorporation of imidazolium salts. Their catalytic activity in the conversion of CO2 was tested over different epoxides to produce the corresponding cyclic carbonates. The key role of the SDS (anionic surfactant) as a templating agent was proved. The best material was stable under the selected reaction conditions, reusable over multiple cycles, and active on a series of different epoxides, thus proving its versatility.

Sodium benzyl sulfonate functionalized-bentonite as a novel adsorbent for water softening process

In this work, novel Sodium benzyl sulfonate functionalized-bentonite (SBSB) adsorbent was synthesized through the reaction of bentonite with benzyl alcohol and chlorosulfonic acid. The prepared adsorbent was characterized using Low-angle XRD, FT-IR and TGA methods, and applied for the removal of calcium and magnesium ions from water solutions. The effect of contact time and initial hardness concentration on the hardness removal efficiency of the prepared adsorbents were studied. It was found that the adsorption was reached the equilibrium condition within about 60 min, and the maximum adsorption capacity (52.5 mg g−1) was achieved in the hardness of 150 mg L−1. Compared to pristine bentonite, the adsorption efficiency of SBSB was significantly enhanced, which is ascribed to the presence of benzyl sulfonate functional groups on its surface. The adsorption isotherm of calcium and magnesium ions on SBSB was described by Langmuir and its adsorption kinetic behavior followed pseudo-second-order model.

Influence of sulphonation on Al-MCM-41 catalyst for effective bio-glycerol conversion to Solketal

Al-MCM-41 and sulphate modified Al-MCM-41 catalysts with variable sulphate loadings (0.25-1SAM) were synthesized through sol-gel and impregnation techniques respectively for the transformation of glycerol into solketal, a fuel additive via acetalization reaction. The mesoporous structure, surface morphologies, composition and porosity of the prepared catalysts were subjected to characterization by Low angle XRD, SEM-EDAX, TEM, FT-IR, XPS and BET-surface area studies. The strength and quantification of acid sites were obtained from TPD of NH3. Pyridine-adsorbed FTIR and 27Al MAS NMR data distinguished Lewis and Brønsted acid sites present on the catalysts. Among the synthesized catalysts, 1 N sulphated Al-MCM-41 was a better catalyst that promotes a higher solketal formation rate of 23.5 mmol h−1g cat−1 by the acetalization of glycerol. This is much higher in comparison to 4 times lesser activity of 6.1 mmol h−1gcat−1 exhibited by the parent Al-MCM-41. This catalyst further showed consistent activity and reusability up to 5 cycles. Large surface area, total acidity, strong Lewis acid sites, compatible surface characteristics of 1 N sulphated Al-MCM-41 endorse the higher acetalization activity of the catalyst. As a result, these parameters have been regarded as crucial considerations in designing a better catalyst in the effective conversion of glycerol to solketal.

DPP-Cu2+ Complexes Gated Mesoporous Silica Nanoparticles For pH and Redox Dual Stimuli-Responsive Drug Delivery.

A simple pH and redox dual stimuli-responsive diketopyrrolopyrrole (DPP)-Cu2+ complexes gated mesoporous silica nanoparticles (MSN) were prepared for precise drug delivery and controlled drug release. MSN was prepared by sol-gel method and then laminated. Carboxylic acid (CA)-Pyrrolo[3,4-c] pyrrole-1,4-dione, 2,5-dihydro-3,6-di-2-pyridinyl (PyDPP) was grafted onto the surface of amino-functionalized MSN (MSN-NH2) through a simple amide reaction and then complexed with Cu2+ to form gated molecules after doxorubicin (DOX) loading. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Low-angle X-ray diffraction (XRD) showed that MSN with uniform particle size (100 nm) and porous structure was successfully prepared. The prepared MSN, MSN- NH2, and MSN-DPP were fully characterized by Zeta potential, Fourier transforms infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption- desorption. High DOX-loading capacity (18.22%) and encapsulation efficiency (89.16%) were achieved by optimizing the mass ratio of MSN to DOX. Release studies showed that the gated molecules of our designed DPP-Cu2+ complexes had a good blocking effect under physiological conditions (the cumulative release rate of drugs within 24 hours was only 4.18%) and responded well to the pH and redox glutathione (GSH) dual stimuli. In vitro cytotoxicity assay showed that MSN-DPP-Cu2+ had good biocompatibility in both Hep G2 cells and L02 cells (the relative cell viability of both cells within 48 hours was above 97%), and the MSN-DPP-Cu2+@DOX could be triggered for efficient drug release in Hep G2 cells. The MSN-DPP-Cu2+ described in this research may be a good delivery system for the controlled release of antitumor drugs and can provide a potential possibility for clinical application in the future.

The fabrication of mesoporous η-Al2O3 nanofiber with tunable pore size by template-induced strategy

In this work, we prepared mesoporous η-Al2O3 nanofiber with tunable pore size using diverse surfactants. The as-prepared mesoporous η-Al2O3 nanofiber was characterized by a combination of various physicochemical techniques. The influence of surfactants types and polymerization degree on surface morphology and adsorption performance of mesoporous η-Al2O3 nanofiber was compared. The results of transmission electron microscopy (TEM), low-angle X-ray diffraction (XRD) and N2 adsorption–desorption isotherm prove the existence of mesoporous structure in η-Al2O3 nanofiber. Polyethylene glycol (PEG) is favored over polyether (PPG) in the preparation of mesoporous η-Al2O3 nanofiber, and PEG with a lower degree of polymerization is beneficial to form well-defined mesoporous structure. The η-Al2O3 nanofiber (PEG600) has the highest specific surface area and the best adsorption performance, followed by the η-Al2O3 nanofiber (PEG2000), and then the η-Al2O3 nanofiber (PPG). Both the adsorption isotherm and the adsorption kinetics equation prove that the adsorption mechanism of methylene blue on mesoporous η-Al2O3 nanofiber is the combination of chemical and multilayer adsorption. This work provides a new avenue to prepare mesoporous η-Al2O3 nanofiber with tunable pore size for the application of mesoporous material in battery, adsorbent, catalytic and biomedical carrier.

Sub-THz Vibrational Dynamics in Ordered Mesoporous Silica Nanoparticles.

The vibrational dynamics in the sub-THz range of mesoporous silica nanoparticles (MSNs) having ordered cylindrical mesopores was investigated. MCM-41 and SBA-15 particles were synthesized, and their structure was determined using scanning electron microscopy (SEM), low-angle X-ray diffraction (XRD), N2 physisorption analyses, and Raman scattering. Brillouin scattering measurements are reported and enabled determining the stiffness of the silica walls (speed of sound) using finite element calculations for the ordered mesoporous structure. The relevance of this approach is discussed based on the comparison between the numerical and experimental results and previous works reported in the literature.

Lamellar-structured fibrous silica as a new engineered catalyst for enhancing CO2 methanation

Recently, Centre of Hydrogen Energy (CHE) has developed new structures of fibrous mesoporous silica nanoparticles (FMSN) and fibrous Mobil composition of matter-41 (FMCM-41) called CHE-SM and CHE-S41, respectively. Both are used as a support, along with adding 5 wt% Ni as active metal and examined on carbon dioxide (CO2) methanation. The low angle x-ray diffraction (XRD) and transmission electron microscopy (TEM) results proved that Ni/CHE-S41 possessed a hexagonal structure while Ni/CHE-SM was discovered in a lamellar structure. In addition, the XRD and N2 adsorption–desorption revealed that Ni particles were deposited on the surface of CHE-SM due to the smaller support pore size (4.41 nm) than the average Ni particles diameter (5.61 nm) resulting in higher basicity and reducibility. Meanwhile, Ni/CHE-S41 revealed deposition of Ni particles in the pore due to difference in support pore size (4.89 nm) compared to average Ni particles diameter (4.01 nm). Consequently, Ni/CHE-SM performed higher CO2 conversion (88.6 %) than Ni/CHE-S41 (82.9%) at 500 °C, while both achieved 100 % selectivity towards methane. Furthermore, the Ni/CHE-SM displayed excellent resistance towards coke formation during 50 h stability test at 500 °C. It is confirmed as Ni/CHE-SM exhibited a weight loss of 0.469% in TGA analysis and a G:D band ratio of 0.43 in Raman spectroscopy, both of which were lower than the corresponding values of Ni/CHE-S41 (0.596% weight loss and 0.74 G:D band ratio). These properties of Ni/CHE-SM are beneficial in methane production field as coke formation could affect the equilibrium of CO2 methanation process.

Fe3O4@C@MCM41-guanidine core–shell nanostructures as a powerful and recyclable nanocatalyst with high performance for synthesis of Knoevenagel reaction

In this study, preparation, characterization and catalytic application of a novel core–shell structured magnetic with carbon and mesoporous silica shells supported guanidine (Fe3O4@C@MCM41-guanidine) are developed. The Fe3O4@C@MCM41-guanidine was prepared via surfactant directed hydrolysis and condensation of tetraethyl orthosilicate around Fe3O4@C NPs followed by treatment with guanidinium chloride. This nanocomposite was characterized by using Fourier transform infrared spectroscopy, vibrating sample magnetometry, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, thermal gravimetric analysis, wide-angle X-ray diffraction and low-angle X-ray diffraction techniques. This nanocomposite have high thermal, chemical stability, and uniform size. Fe3O4@C@MCM41-guanidine catalyst demonstrated high yield (91–98%) to prepare of Knoevenagel derivatives under the solvent free conditions at room temperature in the shortest time. Also, this catalyst was recovered and reused 10 times without significant decrease in efficiency and stability. Fortunately, an excellent level of yield (98–82%) was observed in the 10 consecutive catalyst cycles.

Nickel Oxide Nanoparticles on KIT-6: An Efficient Catalyst in Methane Combustion

KIT-6 silica with well-ordered three–dimensional (3D) mesopores has been synthesized as a support for nickel-based catalysts. Transmission Electron Microscopy (TEM) and low-angle X-ray Diffraction (XRD) analysis are used to ensure that the ordered 3D mesostructure is stable after NiO incorporation. In this study, the catalytic activities of the NiO/KIT-6 samples are investigated. Additionally, the results show that a 10 wt% NiO/KIT-6 catalyst exhibits high catalytic performance in methane combustion, with T10, T50 and T90 being only 386 °C, 456 °C and 507 °C, respectively. Hydrogen Temperature Programmed Reduction (H2-TPR) studies have shown that the interaction between NiO and KIT-6 in the 10 wt% NiO/KIT-6 catalyst is weak. Methane Temperature programmed Surface Reaction (CH4-TPSR) results show that the surface oxygen of the NiO/KIT-6 catalyst allows it to exhibit a high catalytic performance. NiO/KIT-6 catalysts exhibit superior activities to SBA-15, MCF and SiO2 support catalysts because KIT-6 has a higher surface area and ordered 3D mesopore connectivity, which is favorable for better NiO dispersion and peculiar diffusion for reactant and products. Furthermore, the used catalyst maintained an ordered mesostructure and reduction property.

Synthesis of spherical amine-functionalized silica molecular sieve and application as selective adsorbents for aromatic hydrocarbons analysis

In this work, spherical amine-functionalized mesoporous silica (Sp-Amino-Si) molecular sieve was fabricated by an acid hydrothermal method using 3-aminopropyltriethoxysilane as a modifier and toluene as the solvent. The results of scanning electron microscopy, Barrett-Joyner-Halenda pore size distribution, Fourier transform-infrared spectroscopy, and low-angle X-ray diffraction patterns revealed that the Sp-Amino-Si was monodispersed microspheres with uniform and controllable pore sizes sharing two-dimensional hexagonal P6mm symmetry and a large number of amino groups. The Sp-Amino-Si molecular sieve was verified to be suitable for the selective separation of aromatic hydrocarbons (AMHs) containing two fused benzene rings among other compounds from environmental water matrix. Under the optimized conditions, the Sp-Amino-Si exhibited much higher adsorption efficiency for AMHs (above 88.19%), comparing to the original SBA-15 (below 44.52%). The maximum adsorption capacities for naphthalene, methyl naphthalene, 2-methyl naphthalene, and acenaphthene were 477.1, 1006.5, 893.3, and 1253.2 µg·g−1, respectively. The high selectivity of Sp-Amino-Si for the four AMHs attributed to the size sieving and p-π interactions between the lone pair electrons of amine groups and the π-electrons in AMHs molecules. The Sp-Amino-Si based solid-phase extraction coupled with high performance liquid chromatography detection method was constructed for the analysis of the four AMHs, and the recoveries of spiked AMHs ranged from 89.67% to 112.74% with a relative standard deviation lower than 5.75%. This study provides some inspiration and a reliable method for AMHs separation, removal, and analysis.