Accelerated synthesis of Sn-BEA in fluoride media:effect of H₂O content in the gel

Sn-BEA synthesis in concentrated gels results in 2.5–4 fold reduction of crystallization time and formation of smaller zeolite crystals.</p

The analysis of operability of dilatometric microthruster with polymer working components

The article describes the device of a dilatometric microthruster. The study of the device's operability with low power consumption is carried out. It is based on the designed prototype of the thruster in vacuum conditions. The results of the experiments showed that at the pressure of the working gas-air mixture at the thruster inlet of 1 atm. and with a mass flow rate of gas 2,33•10–7 kg/s, the device is able to produce a thrust value within 33 mkH, with a specific thrust pulse of 140 m/s. In turn, the power consumption of the device is only 0,81 W

Energy systems modeling of Kazakhstan on a country and regions level

Climate change, energy safety, energy resources scarcity issues require policies and measures which are based quantitative and qualitative assessment of the whole chain of the energy system starting from extraction to transformation, distribution and consumption. TIMES modeling instrument allows to produce long term scenarios to conduct in-depth energy and environmental analyses

Energy systems modeling of Kazakhstan on a country and regions level

Climate change, energy safety, energy resources scarcity issues require policies and measures which are based quantitative and qualitative assessment of the whole chain of the energy system starting from extraction to transformation, distribution and consumption. TIMES modeling instrument allows to produce long term scenarios to conduct in-depth energy and environmental analyses

Initial stages of propane activation over Zn/MFI catalyst studied by in situ NMR and IR spectroscopic techniques

The early stages of propane activation over Zn-modified H-MFI catalysts were studied by in situ 13C MAS NMR and IR spectroscopic techniques. Propane 2-13C, propane 1-13C, deuterated propane, and deuterated dihydrogen were used as labelled reactants. Both techniques pointed to the formation of zinc propyl species at the onset of propane conversion. Moreover, formation of ZnOH groups simultaneously to zinc propyl species was evidenced by IR spectroscopic techniques. The results point to the propane activation through dissociative adsorption over zinc oxide species, followed by propene evolution and recombinative desorption of dihydrogen. Propene further oligomerizes over acidic sites, while dihydrogen either evolves as a final product or participates in propane hydrogenolysis into ethane and methane. At low partial pressure of reactants, H2 recombinative desorption and hydrogen evolution are favoured, whereas at high pressures, the hydrogenolysis route is preferable

119Sn MAS NMR Study of the Interaction of Probe Molecules with Sn-BEA: The Origin of Penta- and Hexacoordinated Tin Formation

119Sn CPMG MAS NMR was applied to study the adsorption of acetonitrile, methanol, isopropanol, isobutanol and water over Sn-BEA enriched with 119Sn isotope. Two signals observed at ca. -422 and -443 ppm over dehydrated samples were attributed to tetracoordinated framework tin sites with strong and weak Lewis acidity, respectively. The adsorption of acetonitrile and methanol resulted in observation of pentacoordinated tin species, due to the formation of 1:1 adsorption complexes over both Sn-sites. Water adsorption led first to formation of pentacoordinated tin species, which were further converted into hexacoordinated species at longer reaction times. The latter transformation was found to be kinetically limited and was attributed to chemical interaction of tin sites with water, such as hydrolysis of Si-O-Sn bonds. The adsorption of isopropanol and isobutanol was accompanied by the formation of pentacoordinated Sn species in the case of weak sites and hexacoordinated Sn over sites with strong Lewis acidity, pointing to the possibility of dissociative adsorption of secondary alcohols over strong Sn-sites

Production Process and Cost Accounting (Mizoguchi Commemorative Issue)

¹¹⁹Sn CPMG MAS NMR is demonstrated to be a fast and efficient method for characterization of Sn-sites in Sn-containing zeolites. Tuning of the CPMG echo-train sequence decreases the experimental time by a factor of 5–40 in the case of as-synthesized and hydrated Sn-BEA samples and by 3 orders of magnitude in the case of dehydrated Sn-BEA samples as compared to conventional methods. In the latter case, the reconstruction of the quantitative spectrum without the loss of sensitivity is shown to be possible. The method proposed allows obtaining ¹¹⁹Sn MAS NMR spectra with improved resolution for Sn-BEA zeolites with natural ¹¹⁹Sn isotope abundance using conventional MAS NMR equipment

¹¹⁹Sn MAS NMR Study of the Interaction of Probe Molecules with Sn-BEA: The Origin of Penta- and Hexacoordinated Tin Formation

¹¹⁹Sn CPMG MAS NMR was applied to study the adsorption of acetonitrile, methanol, isopropyl alcohol, isobutyl alcohol, and water over Sn-BEA enriched with ¹¹⁹Sn isotope. Two signals observed at ca. −422 and −443 ppm over dehydrated samples were attributed to tetracoordinated framework tin sites with strong and weak Lewis acidity, respectively. The adsorption of acetonitrile and methanol resulted in the observation of pentacoordinated tin species, due to the formation of 1:1 adsorption complexes over both Sn sites. Water adsorption led first to formation of pentacoordinated tin species, which were further converted into hexacoordinated species at longer reaction times. The latter transformation was found to be kinetically limited and was attributed to chemical interaction of tin sites with water, such as hydrolysis of Si–O–Sn bonds. The adsorption of isopropyl alcohol and isobutyl alcohol was accompanied by the formation of pentacoordinated Sn species in the case of weak sites and hexacoordinated Sn over sites with strong Lewis acidity, pointing to the possibility of dissociative adsorption of secondary alcohols over strong Sn sites

Relation between Morphology and Porous Structure of SAPO-11 Molecular Sieves and Chemical and Phase Composition of Silicoaluminophosphate Gels

The formation of silicoaluminophosphate gels using boehmite, Al isopropoxide, and di-n-propylamine as a template of silicoaluminophosphate gels as well as their subsequent crystallization into SAPO-11 molecular sieves was studied in detail using X-ray fluorescence spectroscopy (XRF), powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption&ndash;desorption methods. The effect of the chemical and phase composition of silicoaluminophosphate gels on the physicochemical properties of SAPO-11 molecular sieves was shown. The secondary structural units that the AEL lattice is composed of were found to be formed at the initial stage of preparation involving aluminum isopropoxide. Several approaches to control their morphology and secondary porous structure are also proposed