Specific Surface Measurements Research Articles

Photodegradation of Rhodamine B by CeO2-CuO Binary Composite Nanoparticles Synthesized by Self-Combustion Method

A novel binary composite CeO2-CuO has been synthesized via self-combustion method employing cerium and copper nitrates, and glycine as fuel, and was investigated as photocatalyst to test the photodegradation of Rhodamine B (RhB) dye with visible light. The nanocomposite has been characterized by thermogravimetric analysis (TGA) to establish the temperature of calcination, X-ray diffraction (XRD) structural and morphologic analysis, scanning electronic microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), which enables the chemical characterization/elemental analysis of materials, the photoluminescence (PL), UV-Vis Diffuse reflectance spectroscopy (UV-Vis DRS), measurement of specific surface (SBET ) by N2 adsorption and temperature programmed reduction (TPR) analysis. The XRD diffractogram shows that the composite is majorly composed of 65.2% CeO2 and 34.8 % CuO. The nanoscaled-tested samples have an average particle size of 40 to 65 nm. The energy gap of the material as synthesized was 2.05 eV. The TPR curves show 2 peaks of hydrogen consumption in the sample, corresponding to the decrease (reduction) of CuO particles caused by their interaction with CeO2.The results of the photocatalytic tests show 28% conversion in the photodegradation of RhB organic pollutant during 180 min under visible light. The CeO2- CuO material could be reused for treatment of wastewater during several cycles, which demonstrates its stability for the process.

Photocatalytic degradation performance of antibiotics by WO3/α-Fe2O3/zeolite type II heterojunction with core-shell structure.

The accumulation of antibiotics in the environment can be harmful to human health, and research on their disposal technologies is of increasing interest. In this study, WO3/α-Fe2O3/zeolite (WFZ) type II heterojunction composites with core-shell structures were prepared by coupling WO3 semiconductors with visible-light photocatalytic activity with α-Fe2O3 via hydrothermal synthesis using zeolite as a carrier for the adsorption of synergistic photocatalytic degradation of antibiotics in wastewater. X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), specific surface, and porosity measurements were used to characterize the structure of WFZ type II heterojunction. The performance of WFZ heterojunction for the visible photocatalytic degradation of antibiotics (tetracycline hydrochloride (TCH), ciprofloxacin (CIP), and levofloxacin hydrochloride (LVF)) was investigated. Through four photocatalytic cycles, the catalyst exhibited excellent durability and stability. This was attributed to the core-shell structure and type II heterojunction promoting the effective separation of photogenerated carriers and the extended visible light response range, which resulted in the best photocatalytic activity of the catalyst under visible light irradiation. Radical trapping experiments showed that superoxide radicals (•O2-) and hydroxyl radical (•OH) were the main active species that played a major role in the photocatalytic degradation. These findings show that the synthesized WFZ type-II heterojunction can be used as a reliable visible-light-responsive photocatalyst for the treatment of antibiotics in wastewater.

Retrieving electrical and structural carbonate formation properties from measurements on crushed rock using a multidata inversion approach

SUMMARY Quantification understanding, and prediction of physical rock properties rely so far predominantly on laboratory analyses of cores and plugs. Based on such data, petrophysical models are found that relate both microstructural properties and environmental conditions to geophysically accessible quantities. When considering reactive rock–fluid–gas systems, for example in geothermal energy, enhanced oil recovery or carbon dioxide sequestration, especially with carbonatic rock matrix, this approach is costly and time-consuming at best, or impossible to implement at worst. This is based on the two following reasons: First, porosity, permeability and accessible internal surface area in solid rock plugs are often so low that experimental time duration of many months or even years would be required to achieve chemical equilibrium. Secondly, plugs are single specimens of their — generally heterogeneous — original rock formation, which strongly questions the representativeness of single-plug data. To overcome these shortcomings, we present a new methodology based on the combination of systematic crushing, multimethod laboratory measurements and model-based computational evaluation with solving an inverse problem. As a first step, a large amount of undisturbed rock is intentionally crushed and divided in several particle size classes. Then, petrophysical laboratory measurements are carried out on all particle size classes. The resulting data set is finally inverted for the intended properties of the undisturbed rock. This inverse problem entails a three-level forward model, which parametrizes the undisturbed rock properties, particle characteristics and particle packings, but can also be freely adapted to other tasks by any suitable model representation. The three-level model is designed to enforce the petrophysical correlation of all properties at all levels while using a minimal set of model parameters, thus keeping the inverse problem overdetermined. For the inversion, we have developed a publicly available software tool (AnyPetro) based on a Gauss–Newton inversion scheme to minimize a damped least-squares objective function. To demonstrate and validate the proposed methodology, we present a study using five rock types — four carbonates and one sandstone as a reference. Laboratory measurements of complex electrical conductivity (from spectral induced polarization), specific surface (from nitrogen adsorption) and intraparticle porosity (from mercury intrusion) have been carried out on eight particle size classes and on plugs of each rock for comparison. Supportive and complementary analyses include, for example particle geometry, nuclear magnetic resonance, scanning electron microscopy, computer tomography, uniaxial compression strength and mineralogical composition. We show that our new methodology is highly capable of robustly recovering the complex electrical conductivity, specific surface and porosity of the undisturbed rocks from the measured data. The resulting sets of model parameters are petrophysically reasonable and verifiable. The presented methodology can further be applied to the use of drill cuttings as sample material, which is often the only available rock material from deep wells. Our findings also represent a methodological advance for laboratory experiments on reactive systems and both the interpretation and prediction of petrophysical rock properties in such systems.

Adsorption mechanisms of azo dyes binary mixture onto different raw palm wastes

ABSTRACT This work aimed to understand the adsorption mechanism of dyes in a binary system onto different raw palm wastes and highlights its high efficiency for the removal of methylene blue and methyl orange in competition in aqueous solution. The proposition of the mechanism was based on several parameters and results for that several studies were performed. Characterisation of the specific surface by the methylene blue method and scanning electron microscopy was carried out to study the specific surface measurement and the surface morphology, respectively, on different raw palm wastes. The central composite design was used to evaluate the effects of the following factors (the solution pH and sorbent dose) also to optimise the experimental conditions. Based on CCD results the optimal conditions are pH = 7 and 90 mg for the adsorbent mass. The kinetic parameters calculated using different models show that the adsorption of the mixture of methyl orange (MO) and methylene blue (MB) is fitted to pseudo-first-order. Langmuir isotherm was found to be an adequate model describing the process in its several systems with an amount of adsorbed quantities of about 32.05 mg.g−1 for MB and 16.81 mg.g−1 for MO.

Absorption capacity of superabsorbent polymer in cement pastes: a robustness test

The aim of this study is to investigate how the absorption capacity of a superabsorbent polymer (SAP) in cement paste is influenced by a number of variables: cement type, water-to-cement ratio (w/c), additive, dry SAP particle size, mixing time, and temperature. By means of air void analysis of hardened cement paste, the absorption capacity and the specific surface of SAP voids are obtained. Parallel to the direct measurement of specific surface, this parameter is also derived from dry SAP particle size and absorption capacity. The results show that for the specific type of SAP examined the largest variation in absorption capacity is observed when changing the cement type. Prolonged mixing time can increase the absorption capacity of SAP up to 20%. The influence of a superplasticizer on the absorption capacity of SAP is statistically significant, whereas w/c ratio or dry SAP size has no apparent relation with absorption capacity. A temperature either higher or lower than 20 °C can lead to notably higher absorption capacity of SAP. Prediction of specific surface of SAP voids based on measured absorption capacity and calculation seems promising, as it agrees with the specific surface measured directly by air void analysis. During the preparation of differently sized SAP, it was realized that the order of rinsing and sieving influences the registered size distribution of SAP particles.

One-Dimensional Nanostructures of Polypyrrole for Shielding of Electromagnetic Interference in the Microwave Region.

Polypyrrole one-dimensional nanostructures (nanotubes, nanobelts and nanofibers) were prepared using three various dyes (Methyl Orange, Methylene Blue and Eriochrome Black T). Their high electrical conductivity (from 17.1 to 60.9 S cm−1), good thermal stability (in the range from 25 to 150 °C) and resistivity against ageing (half-time of electrical conductivity around 80 days and better) were used in preparation of lightweight and flexible composites with silicone for electromagnetic interference shielding in the C-band region (5.85–8.2 GHz). The nanostructures’ morphology and chemical structure were characterized by scanning electron microscopy, Brunauer–Emmett–Teller specific surface measurement and attenuated total reflection Fourier-transform infrared spectroscopy. DC electrical conductivity was measured using the Van der Pauw method. Complex permittivity and AC electrical conductivity of respective silicone composites were calculated from the measured scattering parameters. The relationships between structure, electrical properties and shielding efficiency were studied. It was found that 2 mm-thick silicone composites of polypyrrole nanotubes and nanobelts shield almost 80% of incident radiation in the C-band at very low loading of conductive filler in the silicone (5% w/w). Resulting lightweight and flexible polypyrrole composites exhibit promising properties for shielding of electromagnetic interference in sensitive biological and electronic systems.

Comparative study of malachite green and phenol adsorption on synthetic hematite iron oxide nanoparticles (α-Fe2O3)

This article explored the adsorption of the cationic malachite green (MG) dye and phenol, on hematite iron oxide nanoparticles (α-Fe2O3).The characterization of Fe2O3 was evaluated by specific surface measurements of Brunauer Emmett-Teller (BET) and by Fourier transform infrared spectroscopy (IFTR).The results collected on the kinetics adsorption of malachite green show that the adsorption followed a pseudo-second order kinetics.The percentage of elimination reaches respectively 86.13% and 94% for MG (C=6.10−4mol/L) and phenol (C=5.10−4mol/L).The experimental isotherms were analyzed with Langmuir and Freundlich using nonlinear regression. The results showed respectively that the isotherms of Freundlich and Langmuir best fitted to the equilibrium data for MG and phenol. The thermodynamic study has shown that the adsorption of MG and phenol on α-Fe2O3 is endothermic (ΔH°> 0); it increases with temperature. Negative ΔG° values have shown that the adsorption of MG and phenol on α-Fe2O3is spontaneous. However, the positive values of ΔS° indicate the increase in the disorder of the interface of the α-Fe2O3solution during the fixation of MG and phenol.

Exploring the adsorption and diffusion characteristics of tectonic coal at different mass ratios based on the specific surface Gibbs function

Tectonic coal is a soft coal, and the integrity of a tectonic coal seam can become compromised by the formation of cracks under the action of tectonic stresses. A series of tests were conducted to investigate the effect of the mass ratios of tectonic coal on its rock characteristics, including coal gas adsorption tests, specific surface measurements, and initial gas velocity determinations. The study showed that the adsorption value of coal sample gradually increased with increases in the mass ratio of tectonic coal. When the tectonic coal mass ratio reached 50%, the adsorption of the coal sample and initial gas velocity Δp reached highest values. In addition, a mathematical model using the Gibbs function was developed to determine the relationship between the initial gas velocity and the different mass ratios of tectonic coal. This research provides a theoretical foundation for further research on the control of coal and gas outbursts.

An investigation on the suitability of hydrated building lime from travertine limestone outcrop of Bogongo, South West of Cameroon

In the present study, physico-chemical investigations were carried out on hydrated lime produced from the limestone of the travertine outcrop of Bogongo in the South West Region of Cameroon. The aim was to evaluate the suitability of that hydrated lime as building lime. The raw material was characterized and then fired at 900 °C. The fired product was hydrated, dried and also characterized. Chemical and mineralogical analyses, density, BET specific surface measurements and thermal analyses were performed. Results were compared to those for an EN 459-1 CL 90-S industrial commercial hydrated lime. It has been shown that, hydrated lime production using the raw material from the Bogongo travertine could yield products with almost similar physico-chemical properties compared to imported CL 90 S hydrated lime, thus could have positive consequence in the commercial exploitation of the Bogongo travertine limestone outcrop.

Preparation of magnetic MgO/Fe3O4 via the green method for competitive removal of Pb and Cd from aqueous solution

The current work focused on the development of magnesium oxide – based adsorbent for heavy metal removal. Magnetic MgO/Fe3O4 composite was prepared using lysine as a binding agent. The as-prepared adsorbents were characterized using Fourier transform infrared (FTIR) spectroscopy, Transmission electron microscopy (TEM), zeta potential, x-ray diffraction (XRD), Vibrating sample magnetometer (VSM), and specific surface measurement. The adsorption efficiency of MgO, Lysine-modified MgO and magnetic MgO /Fe3O4 composite were determined through Pb(II) and Cd(II) removal from aqueous solution. The effect of pH (2–12), adsorbent dosage (0.3–1.5 g/l) and contact time on adsorption efficiency were investigated. The results showed that maximum efficiency was obtained in the presence of 0.5 g/l of the adsorbent. Additionally, it was found that the pseudo second-order model interpreted the kinetic of adsorption on as-prepared adsorbents. Competitive adsorption of Pb(II)-Cd(II) multi-component solution were studied at different feed concentration. Compared to single-component systems, the adsorption efficiency of Cd(II) was reduced by 33, 19, and 4 % for MgO, lysine modified MgO and magnetic MgO/Fe3O4 composite, respectively. For adsorption of Pb(II) ion, Cd(II) showed inhibition effect only on lysine-modified MgO. The experimental competitive adsorption data were adequately fitted on extended Langmuir isotherm.

Rheological and mechanical properties of bauxite residue as hot mix asphalt filler

Bauxite residue (red mud) is a highly alkaline solid waste generated in the process of production of aluminium metal from bauxite ore. More than 5.5 million tons of red mud is generated in India. The aluminium industries, worldwide and in India, have expressed strong need for dedicated research to explore large-scale utilization of red mud. Towards this end, the objective of this study is to investigate the use of red mud as a filler in hot mix asphalt (HMA). Stone dust, a traditionally used filler material, is used as the control filler. For a comprehensive evaluation approach, the present investigation is conducted at three levels: filler, mastic and mixture characterisation. Red mud and stone dust fillers are characterised using scanning electron microscopy (SEM), pH, Rigden voids, methylene blue value, particle size analysis, and specific surface measurement. Mastic rheology is studied using the dynamic shear rheometer by temperature sweep and multiple stress creep and recovery (MSCR) tests. Finally, dense-graded bituminous concrete (BC) mixes are designed by the Marshall method followed in India, at different filler contents of both filler types. Mixture performance is investigated in terms of indirect tensile strength and Cantabro abrasion loss. Results show that addition of both fillers improved the viscoelastic response of the base binder. Red mud mixes showed higher resistance to disintegration and higher tensile strength than the control mixes with stone dust filler. Based on the findings of this study, red mud showed good potential for use as a filler in dense graded bituminous mixes.

Estimating the mineral surface area of soils by measured water adsorption. Adjusting for the confounding effect of water adsorption by soil organic carbon

AbstractSpecific surface area can be a strong predictor of organic carbon (SOC) contents in soils. Specific surface area can be estimated reliably and cost‐effectively from water adsorption by air‐dry soil samples, but SOC itself can also adsorb water. For estimating the mineral component of specific surface area, it is, therefore, necessary to exclude water‐adsorption by SOC. Here, we refer to “apparent specific surface area” for measurements that include water adsorption by both mineral soil and SOC. We used a mathematical approach to estimate water adsorption by SOC so that this component can be subtracted from measurements of apparent specific surface area.We used a dataset of apparent specific surface area and soil carbon at seven depths from 50 soil cores collected from a research farm in the Manawatu region in New Zealand. Both apparent specific surface area and SOC content decreased with soil depth with very high correlation (r2 = 0.98). We estimated the SOC contribution to apparent specific surface area from the slope of the relationship between changes in apparent specific surface area and SOC content. For our soils, the SOC contribution to apparent specific surface area was estimated as 0.43 ± 0.02 m2 mgC−1. This parameter allows apparent specific surface area measurements to be corrected for the water adsorption by SOC to calculate the functionally relevant mineral specific surface area.Highlights Soil surface area can be estimated from the H2O content of air‐dry soil but SOC also adsorbs H2O. We developed a mathematical approach to estimate water adsorption by SOC. We estimated the contribution of SOC to apparent specific surface area as 0.43 ± 0.02 m2 mgC−1. Mineral specific surface area can be inferred by subtracting SOC‐based H2O adsorption.

Hydroxyapatite Nanoparticles for Acidic Mine Waters Remediation

Mining activities have a high negative impact on the environment and on human health. Environmental impacts can result in contamination of surface water, groundwater, soil and air. Large volumes of wastewater produced by mining activities have to be remediated before being discharged into the environment. Due to the complex composition of wastewater coming from the mining industry and because their negative impacts, numerous remediation techniques have been applied. Adsorption is one of the most extensively used ways to remediate mining wastewater as a consequence of its low cost, easiness to be performed, and also due to the wide variety of materials (natural and synthetic) that can be use as adsorbents. Hydroxyapatite (HAP, Ca10(PO4)6(OH)2), a naturally occurring form of calcium phosphate has a good capacity to remove heavy metal ions from aqueous solutions due to its excellent properties. By preparing hydroxyapatite using different synthesis methods, its properties can be manipulated in order to increase the adsorption properties and reactivity. Herein, we reported synthesis of hydroxyapatite (HAP) samples using different synthesis conditions to establish the effect of synthesis conditions onto HAP properties. The HAP samples prepared have been characterized by the use of X-ray diffraction, FT-IR spectroscopy, specific surface measurements, Scanning Electron Microscopy (SEM). The stoichiometric compounds with high degree of crystallinity, low average particle diameter values, and low specific surface have been prepared by the solid state reaction and high calcination temepratures. The addition of surfactant (dispersant) has resulted in an increase in the specific surface area, which will result in an increase in the retention capacity of heavy metal ions in wastewater. The adsorbents prepared were used to remediate mine water. Results showed that non-calcinated HAP samples have a higher heavy metals adsorption capacity compared to HAP samples calcinated at 600 �C and 900 �C. The HAP samples prepared in presence of surfactant exhibit a higher heavy metals adsorption capacity than samples prepared in absence of surfactant. The values of the retention capacity differ depending on the nature of the metal ion: QMn(II) ] QFe(III) ] QZn(II) ] QPb(II) ] QNi(II). A change in the pH of mine water from 2.6 to 5.5 has occur that means that the metal ion retention mechanism goes through chemical reactions. The metal ions retention capacity suggests application of hydroxyapatite for remediation of mining wastewater.

Experimental Investigation of the Adsorption Characteristics of Mixed Coal and Variations of Specific Surface Areas before and after CH4 Adsorption

Tectonic coal is a kind of soft coal that is generated during tectonic movement. Gas outbursts usually occur in seams containing both virgin coal and tectonic coal. To reveal the adsorption characteristics of this type of coal seam (containing both virgin coal and tectonic coal), both tectonic coal and virgin coal were collected from the same longwall face and a series of laboratory tests were conducted, including coal sorption tests and pore specific surface measurements. Both the tectonic coal and virgin coal were crushed into coal powder (0.18–0.25 mm) for the coal sorption tests. In these laboratory tests, different mass ratios between tectonic coal and virgin coal were tested. We found that with the increase of the percentage of tectonic coal, the adsorption volume showed a rising trend, reached its maximum value, and then decreased. The specific surface areas of the mixed coal samples had the same evolution trends as those of the adsorption volume. From the laboratory tests, we found that when the mass ratio of virgin coal to tectonic coal was 1:1, both the adsorption volume and the specific surface areas reached their maximum values. Due to the percentage variation of the tectonic coal in the panel with the advancement of the longwall face, when the tectonic coal accounted for 50% of the total coal, the gas content would rise. Thus, proper measures should be adopted for outburst hazards control. The mathematical model between the change of specific surface area and the stress and strain of pore expansion before and after gas adsorption was established, and the relationship between the change of pore structure and gas emission before and after gas adsorption was obtained. It provides a theoretical basis for further research on coal and gas outburst mechanisms.

Measurement of interfacial area from NMR time dependent diffusion and relaxation measurements

The interfacial area between two immiscible phases in porous media is an important parameter for describing and predicting 2 phase flow. Although present in several models, experimental investigations are sparse due to the lack of appropriate measurement techniques. We propose two NMR techniques for the measurement of oil-water interfacial area: (i) a time dependent NMR diffusion technique applicable in static conditions, similar to those used for the measurement of the solid specific surface of a porous media, and (ii) a fast relaxation technique applicable in dynamic conditions while flowing, based on an interfacial relaxation mechanism induced by the inclusion of paramagnetic salts in the water phase. For dodecane relaxing on doped water, we found an oil interfacial relaxivity of 1.8μm/s, large enough to permit the measurement of specific interfacial surface as small as 1000cm2/cm3. We demonstrate both NMR techniques in drainage followed by imbibition, in a model porous media with a narrow pore size distribution. While flowing, we observe that the interfacial area is larger in imbibition than in drainage, implying a different organization of the oil phase. In a carbonate sample with a wide pore size distribution, we evidence the gradual invasion of the smallest pores as the oil-water pressure difference is increased.

МЕТОДЫ И УСТРОЙСТВА ДЛЯ ИЗМЕРЕНИЯ УДЕЛЬНОЙ ПОВЕРХНОСТИ ДИСПЕРСНЫХ МАТЕРИАЛОВ

The aim of this work is to systematize the information contained in scientific publications, patents, websites on methods and devices of measuring the specific surface area of dispersed materials, the classification of measurement methods, consideration of their physical bases, comparative analysis of metrological characteristics and mathematical models for specific surface measurements. Comparative analysis of mathematical models of measurement, metrological characteristics and the physical basis of the method is given. A patent search revealed that the described invention is used as adsorbate gas, nitrogen or argon, an inert gas (helium) as the carrier gas. To achieve adsorption temperature the liquid nitrogen is used as the refrigerant. Analysis of commercially available models suggests that a significant portion of analyzers operates on the base of the low-temperature gas adsorption method (BET), and only a small part is made with limited permeability methods measurement range of the specific surface materials. The most used is a laboratory method of low-temperature gas adsorption (BET method or MTD). Despite the many commercially available analyzers are fundamentally common dynamic response - a long analysis time, due to the fact that adsorption processes at low temperatures are slow. Such speed information to the control system is unacceptable because they do not allow the quality control process. Search and development of high-speed analyzer remains relevant for the determination of the specific surface.

Synthesis of nanometric MoNbW alloy using self-propagating high-temperature synthesis

Nanometric powders of stoichiometric compositions in the Mo-Nb-W ternary system were produced by Self-propagating High-temperature Synthesis (SHS) using magnesium to reduce their oxides, in presence of sodium chloride. The influence of Mg and adiabatic temperature on the phase compositions of the final products were determined. After reaction, samples were analyzed by XRD, SEM, and BET.Results demonstrate the possibility to obtain high purity nanostructured products in the 20–800nm range, with an average equivalent diameter, from specific surface measurements, of 66nm. For moderate excess Mg amounts, due to the low Mg boiling temperature, niobium is not completely reduced and forms complex compounds with MgO, whereas reduction is near-complete for the highest Mg amounts.

Investigations on the Pozzolanic Effect of Sugar Cane Bagasse Ashes Used in Cementitious Composites

Brazil is a major producer of alcohol from sugar cane, a fuel with low environmental impact. The production of alcohol generates a large amount of bagasse, the biggest waste of Brazilian agriculture. This bagasse is usually burned for energy production providing nearly 3% of residual ashes. The potential use of these ashes like mineral admixture of cementitious composites depends on calcination conditions. The present work identifies the physical and chemical characteristics of ashes from the furnace exhauster, obtained in an industry located at southeast region of Brazil. The ashes were obtained from bagasse of sugar cane harvest in two different seasons. Chemical composition analysis, X-ray diffraction, grain size distribution, loss on ignition, thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), specific surface measurements (BET) and Fourier transform infrared spectroscopy (FTIR) tests were used to characterize the ashes. The pozzolanic activity was estimated by pozzolanic activity index tests with cement and lime, by the modified Chapelle test, electrical conductivity in lime solution tests, TGA and FTIR. The ashes presented different chemical compositions and degree of amorphicity. The ashes with a higher content of silica, the lower organic material content and high degree of crystallinity (1st harvest), for the same size, have higher pozzolanic on electrical conductivity in lime solution tests than the ashes with lower silica content and higher amorphicity (2nd harvest). However, the results of differential scanning calorimetry (DSC) and modified Chapelle method would indicate the pozzolanicity of the ashes of the 2nd harvest. The results of pozzolanic activity index (with cement or lime) indicated the ashes were not pozzolanic.

Tuning the adsorption potential. Separation of aromatic hydrocarbons by cobalt and zinc zeolitic imidazolate frameworks

The formation of solid solutions (alloys) is a well-established route for tuning the functional properties in materials science, e.g. steels, semiconductors, ceramics. As will be discussed below in this contribution, it appears as a convenient way to control the pore windows accessibility and surface properties. This study illustrates the tuning of the adsorption potential for aromatic hydrocarbons through the formation of solid solutions of Co(II) and Zn(II) imidazolates. The best separation capability and the highest adsorption heats were observed for the mixed compositions (alloys). The random substitution of Zn by Co atoms in the network of zinc methyl-imidazolate, and vice versa, create anisotropies in the metal coordination environment, which are responsible for the appearance of local electron field gradients. This is equivalent to an increase for the adsorption potential able to interact with molecules (adsorbates) with dipole and/or quadrupole moments. Such hypothesis was corroborated for the separation of benzene, toluene and p-xylene, three molecules with quadrupole moments. The highest adsorption heat values for these adsorbates correspond to the solid solution containing Zn and Co. The materials under study were characterized from chemical analysis, X-ray diffraction data, thermal analysis, and specific surface measurements.

Aging of Commercial Diesel Oxidation Catalysts: A preliminary Structure/Reactivity Study

This study focuses on the catalytic behavior of the diesel oxidation catalyst using different aging characteristics of road mileage in order to improve the efficiency of an ammonia SCR system on an after-treatment line composed by a DOC + DPF + SCR. The studied catalyst is a commercial diesel oxidation catalyst (Pt/Pd/Al2O3) provided by Continental. Hydrothermal aging were performed on carrots of monolith in varying the temperature of treatment. These carrots were characterized, X-ray diffraction, transmission electron microscopy coupled by EDS and specific surface measurement (SBET). The catalytic measurements consisted of series of temperature programmed surface reactions. To be close to real driving conditions, our experimental setup comprised a pre-heater in which the gases were heated up to 500 °C. The goal of this study is to understand the evolution of the active phase with the aging and to correlate these aging results with the corresponding overall catalytic activity and their impact on the reactions involved in the DOC with respect to CO, hydrocarbons and NO.