33 research outputs found
Operando Studies of Aerosol-Assisted Sol–Gel Catalyst Synthesis via Combined Optical Trapping and Raman Spectroscopy
Get PDFNew insights have been gained into chemical transformations occurring in the initial stages of aerosol-assisted sol–gel (AASG) synthesis of catalysts. This has been achieved through the combined application of optical trapping and Raman spectroscopy. AASG is an emerging technology in catalyst manufacturing that presents numerous advantages over conventional approaches, including the ability to access unique catalyst morphologies. However, the processes occurring during synthesis are largely inferred from bulk-phase analyses due to challenges in conducting in situ or operando measurements on moving aerosols within a flow tube. Herein, these obstacles are overcome through Raman spectroscopic interrogation of a single aerosol droplet constrained within an optical trap, which acts as a direct analogue for a particle moving along a flow tube. These studies represent the first operando investigations of AASG synthesis. The synthesis of Ni/Al2O3 catalysts has been studied, with spectroscopic interrogation conducted on each component of the precursor synthesis solution, where possible, up to and including a mixture containing all components necessary for catalyst synthesis. Raman spectroscopy confirms the formation of stable self-assembled macrostructures within the aerosol and provides direct insights into the reaction mechanisms. Crucially, evidence was obtained allowing alternative reaction pathways to be postulated within the confined environment of an aerosol droplet in comparison to bulk-phase syntheses. In aerosols where nickel was not present, but contained all other components, isothermal room-temperature studies showed the formation of stable but unreactive droplets of ∼1 μm, which were proposed to contain micelle-type structures. Upon heating, initial gelation transformations were seen to be achieved at temperatures higher than ∼56 °C. Notably, little loss of spectral intensity corresponding to the C–H stretch (ethanol) was observed from the heated aerosol, implying that evaporation is not a prerequisite for the reaction. When nickel is present in the synthesis solution reactive transformations occur at room temperature, proposed to result in a continuous Al–O–Ni–NO3 structure; a more rapid transformation takes place at elevated temperatures. These results provide the first direct evidence of the processes occurring within aerosols during AASG and shed new light on the mechanistic understanding of this technology. This therefore facilitates the design of new synthetic approaches and hence the production of catalysts and other materials with enhanced properties
Synthesis of TiO<sub>2-x</sub>/W<sub>18</sub>O<sub>49</sub> hollow double-shell and core-shell microspheres for CO<sub>2</sub> photoreduction under visible light
Get PDFEfficient low-loaded ternary Pd-In2O3-Al2O3 catalysts for methanol production
Get PDFPd-In2O3 catalysts are among the most promising alternatives to Cu-ZnO-Al2O3 for synthesis of CH3OH from CO2. However, the intrinsic activity and stability of In2O3 per unit mass should be increased to reduce the content of this scarcely available element and to enhance the catalyst lifetime. Herein, we pro -pose and demonstrate a strategy for obtaining highly dispersed Pd and In2O3 nanoparticles onto an Al2O3 matrix by a one-step coprecipitation followed by calcination and activation. The activity of this catalyst is comparable with that of a Pd-In2O3 catalyst (0.52 vs 0.55 gMeOH h-1 gcat-1 at 300 & DEG;C, 30 bar, 40,800 mL h-1 gcat-1 ) but the In2O3 loading decreases from 98 to 12 wt% while improving the long-term stability by three-fold at 30 bar. In the new Pd-In2O3-Al2O3 system, the intrinsic activity of In2O3 is highly increased both in terms of STY normalized to In specific surface area and In2O3 mass (4.32 vs 0.56 g gMeOH h-1 gIn2O3-1 of a Pd-In2O3 catalyst operating at 300 & DEG;C, 30 bar, 40,800 mL h-1 gcat-1).The combination of ex situ and in situ catalyst characterizations during reduction provides insights into the interaction between Pd and In and with the support. The enhanced activity is likely related to the close proximity of Pd and In2O3, wherein the H2 splitting activity of Pd promotes, in combination with CO2 activation over highly dispersed In2O3 particles, facile formation of CH3OH
Efficient low-loaded ternary Pd-In2O3-Al2O3 catalysts for methanol production
Get PDFPd-In2O3 catalysts are among the most promising alternatives to Cu-ZnO-Al2O3 for synthesis of CH3OH from CO2. However, the intrinsic activity and stability of In2O3 per unit mass should be increased to reduce the content of this scarcely available element and to enhance the catalyst lifetime. Herein, we propose and demonstrate a strategy for obtaining highly dispersed Pd and In2O3 nanoparticles onto an Al2O3 matrix by a one-step coprecipitation followed by calcination and activation. The activity of this catalyst is comparable with that of a Pd-In2O3 catalyst (0.52 vs 0.55 gMeOH h−1 gcat-1 at 300 °C, 30 bar, 40,800 mL h−1 gcat-1) but the In2O3 loading decreases from 98 to 12 wt% while improving the long-term stability by threefold at 30 bar. In the new Pd-In2O3-Al2O3 system, the intrinsic activity of In2O3 is highly increased both in terms of STY normalized to In specific surface area and In2O3 mass (4.32 vs 0.56 g gMeOH h−1 gIn2O3-1 of a Pd- In2O3 catalyst operating at 300 °C, 30 bar, 40,800 mL h−1 gcat-1).The combination of ex situ and in situ catalyst characterizations during reduction provides insights into the interaction between Pd and In and with the support. The enhanced activity is likely related to the close proximity of Pd and In2O3, wherein the H2 splitting activity of Pd promotes, in combination with CO2 activation over highly dispersed In2O3 particles, facile formation of CH3OH
Highly selective CO₂ photoreduction to CO on MOF-derived TiO₂
Get PDFMetal–Organic Framework (MOF)-derived TiO2, synthesised through the calcination of MIL-125-NH2, is investigated for its potential as a CO2 photoreduction catalyst. The effect of the reaction parameters: irradiance, temperature and partial pressure of water was investigated. Using a two-level design of experiments, we were able to evaluate the influence of each parameter and their potential interactions on the reaction products, specifically the production of CO and CH4. It was found that, for the explored range, the only statistically significant parameter is temperature, with an increase in temperature being correlated to enhanced production of both CO and CH4. Over the range of experimental settings explored, the MOF-derived TiO2 displays high selectivity towards CO (98%), with only a small amount of CH4 (2%) being produced. This is notable when compared to other state-of-the-art TiO2 based CO2 photoreduction catalysts, which often showcase lower selectivity. The MOF-derived TiO2 was found to have a peak production rate of 8.9 × 10−4 μmol cm−2 h−1 (2.6 μmol g−1 h−1) and 2.6 × 10−5 μmol cm−2 h−1 (0.10 μmol g−1 h−1) for CO and CH4, respectively. A comparison is made to commercial TiO2, P25 (Degussa), which was shown to have a similar activity towards CO production, 3.4 × 10−3 μmol cm−2 h−1 (5.9 μmol g−1 h−1), but a lower selectivity preference for CO (3 : 1 CH4 : CO) than the MOF-derived TiO2 material developed here. This paper showcases the potential for MIL-125-NH2 derived TiO2 to be further developed as a highly selective CO2 photoreduction catalyst for CO production
Elucidating the significance of copper and nitrate speciation in Cu-SSZ-13 for N2O formation during NH3-SCR
Get PDFUnwanted N2O formation is a problem that has been noted in selective catalytic reduction (SCR) where copper zeolite catalysts are utilized. With its immense global warming potential and long-term stability, elevated atmospheric N2O has already been identified as a future challenge in the war on climate change. This paper explores the phenomenon of N2O formation during NH3-SCR over Cu-SSZ-13 catalysts, which are currently commercialized in automotive emissions control systems, and proposes a link between N2O production and the local copper environment found within the zeolite. To achieve this, a comparison is made between two Cu-SSZ-13 samples with different copper co-ordinations produced via different synthesis methods. A combination of synchrotron X-ray absorption near-edge spectroscopy, UV–vis, Raman, and density functional theory (DFT) is used to characterize the nature of copper species present within each sample. Synchrotron IR microspectroscopy is then used to compare their behavior during SCR under operando conditions and monitor the evolution of nitrate intermediates, which, along with further DFT, informs a mechanistic model for nitrate decomposition pathways. Increased N2O production is seen in the Cu-SSZ-13 sample postulated to contain a linear Cu species, providing an important correlation between the catalytic behavior of Cu-zeolites and the nature of their metal ion loading and speciation
EXPERIMENTAL STUDY ON THE EFFECT OF NANO SILICA PARTICLES ON CREEP BEHAVIOR OF SOFT CLAY SOIL
No full textThe compressibility behavior of clay soil has been a major concern in geotechnical engineering. When clay is subjected to a load, effective stress increases with time as a result of dissipation of induced excess pore water pressure, which is known as primary consolidation. After the complete dissipation of the excess pore water pressure, if the load is continuously maintained on the clay, further deformation can be observed over a long period of time, which is known as the secondary compression or creep. When buildings, embankments, and other structures are built on clay soils, large settlements can often be found. Especially, time-dependent deformation in structures built on soft soil may cause damage. Therefore, the study of creep behavior of clay soil for geotechnical application is necessary. Before construction of a structure, to provide a suitable bed, different ways, such as preloading, consolidation and appropriate additives, are applied. In recent years, improvement of soil characteristics using different additives is widely employed. In this study experimental programs are conducted to investigate the effects of low percent Nano silica on creep behavior. One-dimensional single stage and stepwise compression creep tests are conducted using standard oedometer apparatus under different stress levels on soft clay samples. Creep mechanisms are explained based on contacts and deformation of particle and relationship between coefficients of secondary compression and void ratio. Test results clearly indicate that the behavior of soft clay affects percentage of Nano silica and stress levels. With increasing the Nano silica to a specified level, the creep rate of samples decreases, and thus, the soil sample becomes denser. However by a more increase in ratio of Nano silica, porosity and coefficient of secondary compression decreases. On the other hand, it was observed that there is a nonlinear relation between the vertical stress level and coefficient of secondary compression. Also in stabilized samples with Nano silica, the values of compressibility index are smaller than the samples without Nano silica. Of course with increasing the Nano silica to 0.5 weight percentage, due to soil resistance increment against settlement the compressibility index decreases, and with more increase in the weight percentage of Nano silica the compressibility index increases
Mikrorozmnażanie Orchis catasetum-rzadkiej i zagrożonej orchidei
No full textThe application of modern biotechnology for mass propagation of rare and endangered species needs to develop a proper in vitro protocol. Here, a protocol was developed for high frequency in vitro multiplication of an endangered orchid, Orchis catasetum. Protocorms, as explants were cultured on Murashige and Skoog (MS) medium fortified with different concentrations of N6 -benzyladenine (BA), Į-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA) either individually or in combination. A combination of 0.5 mg·L BA and 0.5 mg·L NAA was found to be suitable for maximum protocorm-like bodies (PLBs) regeneration (20.40 × plantlet⁻¹). The largest number of root (7.16 × plantlet⁻¹) and leaf (10.10 × plantlet⁻¹), also the highest plant height (114.20 mm × plantlet⁻¹) and root length (193.40 mm × plantlet⁻¹) were obtained on MS medium supplemented with 0.5 mg·L BA a long with 0.5 mg · L NAA. Plantlets with well-developed leaves and roots were transplanted to pots filled with perlite, wood pieces, ionolite and mineral cartridge shell (1:1:1:1), also perlite individually and transferred to the greenhouse. Upon ex vitro transfer, 100% of plants survived.Zastosowanie nowoczesnej biotechnologii do masowego rozmnażania rzadkich i zagrożonych gatunków wymaga opracowania właściwej procedury in vitro. W niniejszych badaniach opracowano metodę wysokiej częstotliwości rozmnażania in vitro zagrożonej orchidei Orchis catasetum. Protokormy, jako eksplanty, były hodowane na pożywce Murashige and Skoog (MS) wzmocnionej różnymi stężeniami N6 -benzyloadeniny (BA), kwasu 1-naftylooctowego (NAA) oraz kwasu indolilomasłowego (IBA), pojedynczo lub w kombinacji. Stwierdzono, ze kombinacja 0,5 mg · L BA i 0,5 mg · L NAA była odpowiednia do maksymalnej regeneracji PLB (20,40 × sadzonka⁻¹). Największą liczbę korzeni (7,16 × sadzonka⁻¹) i liści (10,10 × sadzonka⁻¹), a także największą wysokość roślin (114,20 mm × roślina⁻¹) i długość korzeni (193,40 mm × sadzonka⁻¹) uzyskano na pożywce MS uzupełnionej za pomocą 0,5 mg · L BA razem z 0,5 mg · L NAA. Sadzonki o dobrze rozwiniętych liściach i korzeniach były przeniesione do doniczek wypełnionych perlitem, trocinami, jonolitem i kompleksem minerałów (1:1:1:1), a także samym perlitem, po czym zostały przeniesione do cieplarni. Po przeniesieniu ex vitro 100% roślin przeżyło
A morphometeric magnetic resonance imaging study of age and gender-related volumetric changes of putamen nucleus in healthy humans
No full textIntroduction: The purpose of this study was to determine the age, sex, and hemispheric differences in volume of the human putamen nucleus in right-handed healthy humans. Materials and Methods: This study was performed on 120 normal human subjects (60 males, 60 females) 15-65 years old that was divided into young (<40 years) and old (�40 years) groups. The sectional brain images obtained via magnetic resonance imaging was analyzed and processed using the image-J software and the putamen volume was calculated using the Cavalieri's principle. Results: The analyses revealed bilateral age-related shrinkage of the putamen in both sexes and the putamen was significantly smaller in older than younger subjects (P <0.001). The age-related shrinkage of the putamen in men and women was about 20.49 and 16.79, respectively. There were no statistically significant volume differences between males and females. There were significant negative correlations between age and the volumes of the putamen nucleus. In both sexes, a significant rightward asymmetry was observed in the putamen (4.21 in men and 3.32 in women). Conclusion: Bilateral age-related shrinkage and rightward asymmetry of the putamen was found in normal humans and there were no volume differences between men and women. Results provide useful baseline data to the age and sex-related change of the volume of putamen
