A XRD Study of the CuAl Layered Double Hydroxide Synthesis Evolution

We present experimental wettability alteration results in originally strongly water-wet, outcrop chalk core plugs using a static and two dynamic aging methods. Dynamic aging with continuous crude oil injection during the entire aging process exhibited greater reduction in water-wetness of the strongly water-wet chalk plugs than static aging without flushing. Two dynamic aging procedures were tested to find an optimal flooding rate for the most efficient reduction in water-wetness: (1) a constant crude oil flooding at 3 cm3/h using variable aging times (48, 96, and 192 h) and (2) a constant aging time (96 h) with variable flooding rates (1, 3, and 5 cm3/h). The aging temperature was kept constant in all tests (90 °C), and the impacts from varying aging times, pore volumes injected, and crude oil injection rate on the wettability alteration process were investigated. Aging was performed on consolidated, porous chalk samples with initial water present in the pore space. It was shown that static aging, i.e., aging in a stagnant, limited amount of crude oil, and dynamic aging, i.e., with continuous flooding of crude oil, performed equally well in terms of average Amott−Harvey water indices (Iw ∼ 0.6) for short aging times (72 h or less). For longer aging times, the static approach failed to established an Amott−Harvey water index under Iw = 0.25 and required 3 times as long of an aging time compared to dynamic aging (7 days for dynamic or 24 days for static required to establish Iw ∼ 0.25). Amott−Harvey water indices lower than Iw = 0.25 were established with dynamic aging for shorter aging times (less than 12 days). At a given constant aging time (96 h), it was found that wetting was sensitive to the crude oil injection rate and that there exists an optimal crude oil injection rate with the greatest change in wettability.

The Fischer–Tropsch synthesis is a catalytic conversion of syngas into hydrocarbon mixtures. A solvothermal method was used to prepare Iron–cobalt–cerium nanocatalyst for conversion of syngas into light olefins. Duration of aging time in preparing method is a key factor affecting in a chemical process. The results showed that the optimal aging time and operating temperature in order to increase light olefin selectivity is at 11 h and 330 °C. The effects of experimental variables including aging time (5, 8 and 11 h) and operating temperature (270–380 °C) were investigated. The nanocatalysts were characterized by temperature programed-reduction (TPR), X-ray diffraction (XRD), energy dispersive X-ray, Fourier infrared spectroscopy, and vibrating sample magnetometer. TPR profiles of the nanocatalysts synthesized at different time of aging indicated that aging time shifted the sample’s reducibility via affecting its particle size. Average crystalline size determined from XRD patterns ranged over 4.5–6.6 nm. It is found that particle size increases with increasing aging time. The results show that time of aging has effect on magnetic properties of nanocatalysts changing from soft ferromagnetic to a hard ferromagnetic one as aging time increases. In addition, the sample aged for 5h exhibits a maximum saturation magnetization of 7.768 emu/g, the maximum coercivity value of 1744.46 Oe is obtained for the sample aged for 8 h.

Effect of heat treatments on the microhardness and tensile strength of Al–0.25 wt.% Zr alloy

Growth of nano hexagon-like flake arrays cerium carbonate created with PAH as the substrate

Thioflavin T (ThT) is a fluorescent dye able to enhance significantly its fluorescence quantum yield upon binding to protein amyloids. ThT assay is widely used to detect and quantify amyloids in a variety of conditions, including solutions with different pH levels. In the present work, the effect of acidic and basic pH on the conformation of the ThT molecule and its absorption and fluorescence properties was studied. The results show that both acidic and basic pH decrease significantly the intensity of ThT absorption in the visible region and fluorescence emission intensity. Low pHs induce an immediate "all-or-nothing" decrease in the ThT signal, while in alkaline solutions the ThT signal decreases gradually over time. pH-induced signal quenching is less in the presence of glycerol or protein aggregates. Two different mechanisms are responsible for the ThT signal quenching-the ThT hydroxylation at basic pH and protonation of the nitrogen atom of the dimethylamino group at acidic pH. ThT assays should be carefully carried out at basic or acidic pH as strong pH dependence of ThT could be responsible for misinterpretation and false positive/negative experimental results. The potential unsuitability of ThT as a probe in solutions with high pH (>9) has been shown.

A study of the effect of the aging atmosphere on the activity of co-precipitated copper zinc oxide catalysts for the ambient temperature oxidation of carbon monoxide is described and discussed. Four aging atmospheres are reported: air, N2, H2 and CO2, and both the precipitation and the aging of the precipitate were carried out by flowing these gases through the precipitation cell at constant pH and temperature. For all atmospheres, the surface area of the final CuO-ZnO catalyst increases with aging time and, consequently, the specific activity (mol CO converted/g catalyst/h) also increases. However, the intrinsic activity (mol CO converted/m2/h) initially decreases with aging time before attaining a steady level. The highest activity catalysts were obtained using air as the aging atmosphere and TPR studies indicate that this catalyst is less readily reduced. Catalysts prepared using CO2 as the aging atmosphere have lower activity, although the surface areas of these catalysts are not markedly lower. The study demonstrates that selection of the appropriate aging atmosphere, as well as the aging time, is an important parameter for the preparation of co-precipitated catalysts.

A study of the effect of the aging atmosphere on the activity of co-precipitated copper zinc oxide catalysts for the ambient temperature oxidation of carbon monoxide is described and discussed. Four aging atmospheres are reported: air, N2, H2 and CO2, and both the precipitation and the aging of the precipitate were carried out by flowing these gases through the precipitation cell at constant pH and temperature. For all atmospheres, the surface area of the final CuO-ZnO catalyst increases with aging time and, consequently, the specific activity (mol CO converted/g catalyst/h) also increases. However, the intrinsic activity (mol CO converted/m2/h) initially decreases with aging time before attaining a steady level. The highest activity catalysts were obtained using air as the aging atmosphere and TPR studies indicate that this catalyst is less readily reduced. Catalysts prepared using CO2 as the aging atmosphere have lower activity, although the surface areas of these catalysts are not markedly lower. The study demonstrates that selection of the appropriate aging atmosphere, as well as the aging time, is an important parameter for the preparation of co-precipitated catalysts.

Nickel–iron layered double hydroxide (LDH): Textural properties upon hydrothermal treatments and application on dye sorption

This review provides a state-of-the-art summary of distributed zeolite technology, as well as identifying strategies to further promote the absorption of these materials in various areas of study. Zeolites are materials that can be synthesized or found in natural rock deposits a with a basic composition consisting in Al, Si, and O. Zeolite’s consideration as a future material is due to many facile synthesis methods to obtain different structures with variations in pore size, surface area, pore volume and physical properties. These methods are developed using the control of relevant synthesis parameters that influences structure formation, such as crystallization temperature, time of aging and/or crystallization, stoichiometric relationships between components of synthesis gel, pH of the medium, and in some cases the type of structure-directing agent. Each method will lead to geometric changes in the framework formation, making possible the formation of typical chemical bonds that are the fingerprint of any zeolitic structure (O-Si-O and Al-O-Si), forming typical acid sites that give specificity in zeolite and allows it to act as a nanoreactor. The specificity is a characteristic that in some cases depends on selectivity, a fundamental property derived of the porosity, mostly in processes that occur inside the zeolite. In processes outside the structure, the surface area is the main factor influencing this property. Moreover, there are many natural sources with adequate chemical composition to be used as precursors. Some of these sources are waste, minimizing the deposition of potential hazardous materials that can be recalcitrant pollutants depending on the environment. Besides its uses as a catalyst, zeolite serves as a support for many bioprocesses; therefore, this review aims to explain relevant aspects in chemical nature, physical properties, main methods of synthesis, main precursors used for synthesis, and relevant applications of zeolites in chemical catalysis and biological processes.

Influence of precipitation conditions on precursor particle size distribution and activity of Cu/ZnO methanol synthesis catalyst

We demonstrate the structural reorganization of gold nanorods (GNRs) that could fine-tune localized surface plasmon resonance (LSPR) by using modified wet chemical synthesis on the solid substrate. Controlling the growth solution ageing time using the modifiable GNRs is an approach to overcome the limitations of rods formation due to inhomogeneous and uncontrollable size and aspect ratio. In this study, the suitable ageing time of GNRs was determined to produce optimum GNRs in terms of surface density and aspect ratio. As the ageing time was increased from 30 min to 24 h, the colour of the growth solution was changed from light to dark purple. The change is associated with the density of the nanorods formation. The optical spectral peaks of GNRs occur in a range between 500 nm and 800 nm in the visible and near-infrared region spectrum for transverse surface resonance (t-SPR) and longitudinal surface resonance (l-SPR), respectively. From the morphological analysis, it was found that 20 h ageing time resulting in high density and homogeneous GNRs with 74.81% surface density with 4.23 ± 0.04 aspect ratio. Hence, the growth ageing time of GNRs can be manipulated to control their shape evolution and dimension in terms of size and aspect ratio. The controllable aspect ratio and size GNRs can be potentially used as sensing material in plasmonic applications.

Ovalbumin gels were prepared by heat treatment at constant pH and ionic forces. Ovalbumins are widely utilized as emulsifying or binding agents. However, due to their protein origin, mechanical properties of ovalbumins are enclosed in a wide range of rheological responses depending on concentration, ionic strength, pH, and aging time. The objective of this work was to study the effect of processing conditions (pH, ionic strength, and protein content) on the textural attributes of an ovalbumin protein system by means of uniaxial compression. Gels were prepared by dispersing proteins (purity 98%) (8.3–12.5% w/w) until complete dissolution in deionized water at 90°C by 45 min, pH (6.3–9.1) was adjusted using citric acid, and the ionic strength (0–100 mM of NaCl) was adjusted using NaCl. The storage of gels was done at 63°C (24–168 h). The rheological tests of gels were done by uniaxial compression. A rupture force peak was observed at high protein content together with an increase in the Young’s modulus. At fixed conditions of ion content (NaCl 50 mM) and pH of 7, the gels presented a maximum in fracture force and Young's modulus after 7 days of storage. The addition of minimum amount of citric acid increases the stability of ovalbumin gels. This information is useful to ensure that the final product will remain stable during storage time at longer shelf lives.

A simple sol−gel route has been developed for the preparation of mesoporous and nanocrystalline anatase thin layers. An anatase hydrosol was first synthesized at room temperature from acidic hydrolysis of titanium isopropoxide. The optimization of the synthesis parameters, including titanium concentration, HCl/Ti and H2O/Ti ratios, temperature, and aging time, enabled us to produce a clear sol with a very low HCl/Ti ratio (equal to 1). As a function of the further thermal treatment conditions, it was then possible to control the size of the anatase crystallites (from 5 to >10 nm) and the O/Ti stoichiometry (from 1.9 to 2.0). Ordered mesoporosity was obtained by using a triblock copolymer as the templating agent. Preliminary experiments evidenced the photocatalytic activity of the prepared layers.

In our present study, the effects of different parameters on the synthesis of silicoaluminophosphate, SAPO-34, were investigated and the product selectivity and catalytic performance of this catalyst were studied for the reaction of methanol to olefins in a fixed bed reactor. In spite of examining the conventional parameters effective in the hydrothermal preparation of SAPO-34, such as templating agents or mixed templating agents with different ratios, different alumina and silica sources, aging time and hydrothermal reaction in static state, we have investigated the effect of the mixing method and the addition of crystal growth inhibitors on the morphology and particle size of the prepared zeolites. The synthesized catalysts have been characterized with several methods such as Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, BET and X-ray powder diffraction. Under our experimental conditions, the prepared SAPO-34 has shown better selectivity to propylene, minimum paraffinic byproducts and a higher percentage of total olefins compared to a commercial ZSM-5 catalyst.

A series of HMS molecular sieves with different pore structures were prepared by using dodecylamine and octadecylamine as template and tetrabutyl orthosilicate as silicon source to study the different pH values and temperatures. Adsorption performance. The physicochemical properties of HMS molecular sieves were characterized by BET, XRD and SEM. The results showed that the HMS molecular sieve material synthesized by dodecylamine as template was obtained after standing for 12 h in water bath for 12 h, pH 2 and calcination temperature was 550 °C. The best adsorption effectis HMS molecular sieve material synthesized by octadecylamine as template agent has the best adsorption effect when the aging time is water bath for 24 h, pH is 10, and calcination temperature is 550 °C. The adsorption rates are up to 71.72% and 74.78%, respectively.