Performance improvement of PDMS/PES membrane by adding silicalite-1 nanoparticles: separation of xenon and krypton

The polydimethylsiloxane (PDMS) mixed matrix membrane with dispersed phase of nanozeolite silicalite-1 has been synthesized on polyethersulphone (PES) as a support, and its performance in the gas separation of xenon and krypton has been studied. For this purpose, nanozeolite silicalite-1 is synthesized by the hydrothermal clear solution method and is characterized by XRD and SEM analysis. In this research, the separation performance of MMM has also been compared with the polymeric PDMS membrane. Furthermore, the effect of feed pressure and loading percentage of nanozeolite in the polymeric matrix are evaluated. The results indicate that the addition of nanozeolite to the polymeric matrix improves its separation performance, and that the changes of the feed pressure have no major effect. The average permeability of the krypton and xenon gases through the PDMS polymeric membrane is calculated as 1.25 × 10^?9 and 1.78 × 10^?9 cm mol/(cm² s kPa), respectively, while by adding only 5 wt% of nanosilicalite-1 to the polymeric matrix of the membrane, this amount increased to 1.82 × 10^?9 and 8.07 × 10^?9 cm mol/(cm² s kPa), respectively. In addition, the presence of nanosilicalite-1 as the filler leads to an increase in the selectivity of xenon to krypton up to 4.38.     

Efficient Synthesis of Bicyclo[3.3.1]nonane Systems via Tandem 1,3-Dinucleophilic Addition of 4-Hydroxy-2-quinolinones to Quinolinium Salts

The synthesis of bicyclo[3.3.1]nonane systems is reported. The synthesis is based on the tandem 1,3-dinucleophilic addition of 4-hydroxy-2-quinolinone to quinolinium salts.     

Molybdatophosphoric Acid/NaNO2/Wet SiO2 as an Efficient System for the Aromatization of 1,2‐Dihydroquinolines under Mild and Heterogeneous Conditions

A combination of molybdatophosphoric acid and NaNO₂ in the presence of wet SiO₂ was used as an effective oxidizing agent for the oxidation of 1,2‐dihydroquinolines to their corresponding quinoline derivatives in dichlomethane at room temperature with excellent yields.     

Investigation on the Complexation of Dioxovanadium (V) with D-(-)-Quinic Acid in Water + 1-Butyl-3-Methylimidazolium Tetrafluoroborate and Water + Methanol Mixed Solvents Using the KAT Model

The complex formation reaction of the $ {\text{VO}}_{2}^{ + } $ VO 2 + cation with D-(-)-quinic acid {(1R,3R,4S,5R)-(-)-1,3,4,5-tetrahydroxycyclohexane-1-carboxylic acid} at T = 298 K, I = 0.1 mol·dm^?3 of sodium chloride in various aqueous solutions of 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim]BF₄, and methanol were studied by using potentiometric and UV spectrophotometric techniques. As far as we know, the calculated stability constants data presented in the current work are the first reported values for [bmim]BF₄ and methanol mixed solvents. The Kamlet–Abboud–Taft solvatochromic equation enabled us to interpret the UV data and the stability constants values. The Redlich–Kister equation was applied for the calculation of solvatochromic parameters in the binary water + [bmim]BF₄ mixtures. Hydrogen bonding is important for the dissociation constant in both media. In these systems the solvent polarizability and hydrogen-bond donor ability are the main interactions for the stability constants in the aqueous ionic liquid and methanol solutions, respectively.     

Spectroscopic studies of dehydrogenation of ammonia borane in carbon cryogel

Ammonia borane (AB) is of great interest for storing hydrogen, an important issue in the growing field of hydrogen technology. The reaction pathways leading to the thermal decomposition of solid-state AB incorporated in carbon cryogels (CC) have been studied by spectroscopic methods. The time-dependent thermal decomposition was followed by in situ 11B nuclear magnetic resonance (NMR) and showed a significant increase in hydrogen release kinetics for AB in CC compared to neat AB. Both 11B NMR and Fourier transform infrared spectroscopy show a new reaction product, formed in the thermal decomposition of AB in CC scaffold (CC-AB) that is assigned to reactions with surface oxygen groups. The results indicate that incorporation of AB in CC enhances kinetics because of the reactions with residual surface-bound oxygen functional groups. The formation of new products with surface -O-B bonds is consistent with the greater reaction exothermicity observed when hydrogen is released from CC-AB materials. Scanning electron microscopy shows different morphology of AB in CC-AB nanocomposite as compared to neat AB.     

Coherent carbon cryogel-ammonia borane nanocomposites for H2 storage

Coherent carbon cryogel-ammonia borane (C-AB) nanocomposites were synthesized, and improved H2 storage properties are reported. Porous carbon cryogels were impregnated with AB in tetrahydrofuran solution at 25 degrees C under argon; 30% of the carbon cryogel pore volume was filled to produce a 24 wt % C-AB nanocomposite. Nitrogen sorption isotherms, X-ray diffraction, differential scanning calorimetry, differential thermal/thermal gravimetric analyses, mass spectrometry, and 11B NMR were used to characterize the coherent C-AB nanocomposites. Findings include a merged two-step hydrogen release reaction with an appreciable reduction in the dehydrogenation temperature to <90 degrees C as well as the suppression of borazine release. The possible nanosize effects on the H2 storage properties are discussed.     

Application of specific ion interaction theory and parabolic models for the molybdenum(VI) and tungsten(VI) complexes with NTA and IDA at different ionic strengths

The interaction of nitrilotriacetic acid (NTA) and iminodiacetic acid (IDA) with tungsten(VI) (pH 7.5) and molybdenum(VI) (pH 6.00) has been studied in aqueous solutions at 25 ℃, and different ionic strengths (0.1 相似文献   

Mn(III)-porphyrin/graphene oxide nanocomposite as an efficient catalyst for the aerobic oxidation of hydrocarbons

In this study, manganese porphyrin was grafted on the surface of graphene oxide nanosheets via covalent bonding to produce a heterogeneous catalyst. The prepared nanocomposite was characterized using X-ray diffraction, UV–vis spectroscopy, scanning electron microscopy, Fourier transform infrared, and thermogravimetric analysis. Atomic absorption spectroscopy was also used to determine the amount of the loaded catalyst. The catalytic efficiency of the immobilized Mn-porphyrin was investigated for the aerobic oxidation of alkenes and saturated alkanes in acetone under mild reaction conditions. The prepared heterogenized catalyst displays superior catalytic performance as compared to the homogeneous catalyst. Moreover, the excellent turnover number (more than 31,767) achieved for the oxidation of styrene indicates the high longevity of the supported catalyst. The catalyst structure is preserved well after the oxidation reaction and is simply reused at least five times, without any significant loss of the catalytic efficiency.