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Exploring reliable hydrogenation catalysts to remove trace olefins in aromatic hydrocarbons through hydrogenation is an important topic. In this paper, a bimetallic Cu–Ru/montmorillonite (Cu–Ru/M) catalyst was prepared using a step-by-step impregnation method, and the effects of bimetallic catalysts on removing olefins were assessed. The catalysts were characterized using X-ray diffraction, Brunauer–Emmett–Teller specific surface area, inductively coupled plasma atomic emission spectrometry, high-resolution transmission electron microscopy and temperature-programmed reduction of H2. The results show that there is a strong interaction between Cu and Ru on the Cu–Ru/M catalyst, which improves the dispersion of the metals on the surface of the support M. The hydrogen spillover phenomenon of Cu–Ru/M enhances its activity and adsorption capacity for hydrogen species. The catalytic performance test confirmed that the bimetallic catalyst has significantly greater activity and stability. The optimal loadings are 5% copper and 1% ruthenium, and the performance of this catalyst is comparable to those of noble-metal Pt/M catalysts.
Samples from the pyrophyllite reserves in the Malatya–Pütürge region, used in the production of the whitest cement in Europe, were beneficiated using flotation. The mineralogical composition of the natural pyrophyllite, as determined using X-ray diffraction, includes pyrophyllite, kaolinite, quartz, illite–mica and feldspar. The chemical composition of pyrophyllite contains 69.75% SiO2 and 23.04% Al2O3. The pyrophyllite percentage (40–45 wt.%) of the natural sample increased to 60–80 wt.% after flotation. In flotation experiments, the effects of reagent amounts, types and their mixtures were investigated. Methyl isobutyl carbinol (MIBC) and pine oil as frothers and kerosene as a collector were used in the flotation studies. The use of reagents as mixtures has a positive effect on the beneficiation compared to use on their own. The best result was obtained for a mixture of MIBC with kerosene, which is a non-ionic hydrocarbon oil, yielding a concentrate containing 26.63% Al2O3. Improved results were also observed for kerosene plus frother mixtures after flotation cleaning circuits. The bubbles formed during flotation were photographed and the bubble diameters were measured using the ImageJ program. The Al2O3 content was evaluated by correlating the bubble diameters. In general, selectivity decreased during experiments in which bubble diameters were reduced.
High-performance mullite-based composite ceramics were prepared successfully using natural kaolin and alumina as raw materials and ZrO2 as an additive. The influence of sintering temperature and ZrO2 content on the sintering behaviour and mechanical properties of zirconia-toughened mullite ceramics was studied systematically. With increasing sintering temperature from 1450°C to 1560°C, the primary phases of as-sintered composite ceramics were mullite and corundum with a small amount of ZrO2, and the bulk density of the composite ceramics increased from 2.29 to 2.72 g cm–3. Furthermore, the ZrO2 phase transition promoted transgranular fracture, and ZrO2 grains were pinned at the grain boundaries, thereby enhancing the mechanical strength of the composite ceramics. Moreover, the AZS12 sample, with 12 wt.% ZrO2 and sintered at 1560°C, had the greatest flexural strength and fracture toughness of 91.6 MPa and 2.47 MPa m–1/2, respectively. Adding ZrO2 to the composite ceramics increased their flexural strength by ~37.6%.
The sorption properties of two layered minerals of the hydrotalcite supergroup – hydrotalcite and stichtite – were investigated with the aim of determining their kinetic parameters of sorption and their adsorption isotherm type. Pristine hydrotalcite and stichtite were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive Х-ray analysis and laser diffraction analysis of the particle-size distribution. The ‘memory effect’ of the sorbents was examined after calcination at 650°C. Slight indications of reconstructed hydrotalcite were observed, while the stichtite dehydration–rehydration cycle was irreversible. The hydrotalcite and stichtite were used to remove Congo Red from the aqueous solution. The pseudo-second order kinetic model described the process adequately. Mixed external and internal diffusion was confirmed for both minerals. The sorption of Congo Red on stichtite fits the Langmuir model. Stichtite demonstrated a maximum adsorption capacity of 2.5 mmol g–1 at 35°C. Increasing temperature increased the adsorption rate of Congo Red on stichtite but did not affect the adsorption rate constant for hydrotalcite.
The Nanjing Bao'ensi site is the largest and highest-ranking royal temple from the Ming Dynasty, and it is famous for its full-body glass pagoda. In this study, the glazed tiles excavated from the southern area of the Bao'ensi site were selected and analysed using X-ray diffraction, thermal dilation and energy-dispersive X-ray fluorescence to determine their phase composition, firing temperature and chemical composition. The glazed tile bodies of the Bao'ensi site consist mainly of quartz and mullite, although some samples contain trace amounts of other minerals. All of the body samples were fired to the same temperature range (i.e. 1000–1100°C). The firing temperature combined with the phase composition indicate that the raw materials and firing process of the glazed tile body samples have similarities, but there are certain differences. The source of the raw materials for a portion of the glazed tile bodies is Dangtu, Anhui, whilst the source of the raw materials for the remaining materials remains to be discovered.
In polymer composites, montmorillonite nanosheets are crucial as fire retardants, reinforcers, anti-corrosives, detoxifying agents and ultraviolet-protection agents. However, the quality of montmorillonite nanosheets can be improved by optimizing the raw bentonite purification process in which undesirable phases are removed. Optimization of Iranian calcium bentonite purification for nanomontmorillonite synthesis considering various parameters based on various physical approaches to dispersion and ultrasonication was investigated; the calcium bentonite purification was performed using sodium hexametaphosphate followed by either sedimentation or centrifugation, and the nanomontmorillonite synthesis was performed using ultrasonic treatment. The effects of suspension concentration, milling type, pH and centrifugation duration and speed on the separation of various impure phases were evaluated qualitatively and optimized. The raw and purified bentonite and the synthesized nanomontmorillonite were characterized using X-ray powder diffraction, X-ray fluorescence spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy. The cation-exchange capacity was also measured in the raw and purified samples. Optimal experimental conditions in the dispersed samples were achieved at a 2.5 wt.% concentration of bentonite suspension and planetary milling at pH 7. While the ultrasonic treatment was more effective than the dispersion approach for cristobalite elimination, a smaller lateral size of the montmorillonite sheets, optimized at 0.5 wt.% concentration of the suspension, was achieved. The increased cation-exchange capacity after the purification improved the exfoliation and delamination of montmorillonite nanosheets in the presence of cetyltrimethylammonium bromide as the surfactant. The interplanar spacing of (001) planes of 15 Å in raw bentonite shifted to 21 Å and 19 Å in purified and non-purified samples, respectively, after synthesis.
Uniaxial and isothermal compression tests of kaolinite were carried out using molecular dynamics simulations. Five different temperatures (300, 400, 500, 600 and 700 K) and pressures ranging from 0.0001 to 50 GPa were selected to study the temperature and pressure effects on the mechanical properties of kaolinite. As kaolinite may undergo a phase transition at ~1572 K, a highest temperature of 700 K was chosen to avoid such structural change. The Young's modulus, strength and elastic constants of kaolinite under various temperatures were calculated, and the relative change of the elastic constant C33 with temperature was found to be almost 12 times greater than the relative change of the interlayer constant C11. The microstructures under various compressive strains were tracked and they exhibited various failure modes in three directions. The temperature and pressure effects on the mechanical properties of three crystal directions were analysed. The results showed that the Young's modulus of the z-direction is the most affected by temperature; however, the influence of temperature on the strengths of the three crystal directions was the same. In addition, the structure of the z-direction was the most sensitive to temperature under the same hydrostatic pressure due to the weak interactions between layers.