The present work aims to investigate the effect adding Ag, Co, Ni, Cd and Pt to copper on ethanol dehydrogenation. The catalysts synthesized by deposition–precipitation method were characterized using various physicochemical methods such as N2 adsorption–desorption, TPR, SEM–EDX, XRD, XPS and TGA–DSC-MS. Catalytic evaluation results revealed that the predominant product of the reaction was acetaldehyde. Monometallic copper or mixed with Cd, Ag or Co show good catalytic performances. Adding nickel to copper improves the process conversion but reduces acetaldehyde selectivity, giving rise to methane in produced hydrogen. Pt-Cu/SiO2 catalyst guides the reaction towards diethyl ether. Time on stream tests performed during 12 h at 260 °C, showed that adding Cd to Cu enhances its stability by over 30% of conversion, this is explained by the reduction of copper crystallites sintering, which makes Cd-Cu/SiO2 a promising catalyst for the production of acetaldehyde by ethanol dehydrogenation.
This work aims at demonstrating the interest of a new methodology for the design and optimization of composite materials and structures. Coupling reliability methods and homogenization techniques allow the consideration of probabilistic design variables at different scales. The main advantage of such an original micromechanics-based approach is to extend the scope of solutions for engineering composite materials to reach or to respect a given reliability level. This approach is illustrated on a civil engineering case including reinforced fiber composites. Modifications of microstructural components properties, manufacturing process, and geometry are investigated to provide new alternatives for design and guidelines for quality control. 相似文献
The diversified use of filamentary composites in harsh marine environments, recorded in recent years, has prompted researchers to focus their work on the reliability prediction. Through failure criteria, Tsai–Wu and the maximum stress, the reliability of multilayer tubular structures under mechanical loading is the subject of this paper, where Monte Carlo method estimated the failure probability. A sensitivity analysis was performed in order to identify the influence of the different parameters, such as materials’ properties, geometry, manufacturing and loading, on the reliability of the composite cylindrical structure studied. To achieve a high accuracy of the results, we have carried out 105 simulations. The results showed great influence on pressure loading, ply thickness and finally winding angle of filament composite. 相似文献
This paper reports work studying the partial substitution of the commonly used plasticiser di-octyl phtalate (DOP) by the permanent plasticisers ethylene-vinyl-acetate (EVA) and acrylonitrile-butadiene-styrene (ABS) in order to reduce migration of additives initially present in poly(vinyl chloride) (PVC) stabilised with epoxidised sunflower oil (ESO). Various formulations with and without the two different permanent plasticisers were prepared. Their tensile properties were compared. Migration tests with agitation at 40°C in two food simulants (olive oil and 15% aqueous ethanol) were carried out. The mass variation of the PVC samples with time was investigated. Migration phenomena were studied by using various analytical methods such as Fourier transform infrared spectroscopy (FTIR), atomic absorption spectrometry (AAS) and scanning electron microscopy (SEM). The results showed that additives migration can be considerably reduced by partial substitution of DOP with both permanent plasticisers used. The best results were obtained with the binary system of plasticisers based on DOP:ABS (30:10). 相似文献
The ability of microorganisms to grow at high temperature, alkaline pH, and high salinity makes them an attractive target for enzyme-production with several industrial applications. One strain TN-X30 has been selected as protease producer and identified as Streptomyces mutabilis after a phenotypic and molecular study. Its production of protease was improved using Taguchi L27 design. The strategy was carried out to identify the optimum levels and the interaction of the screened factors. Following this step, maximum protease activity (10,895 U/ml) was achieved after 6-days of incubation. The TN-X30 protease activity had an optimum of pH and temperature of 10 and 65°C, respectively. Thermodynamic parameters at 60°C were enthalpy 14.26 kJ/mol, entropy −220 J/mol/K, and Gibbs free energy 90.53 kJ/mol. TN-X30 protease production displayed a 16-fold increase reaching 175,000 U/ml in a 100-L fermentor. Furthermore, the lyophilization in presence of sorbitol enhanced the stability of the TN-X30 protease which remained active at 75% after 24-months of storage. The lyophilized TN-X30 protease exhibited exceptional stability indexes in presence of some known commercialized detergent components as NEODOL® 25-7, Dehydol® LT 7, Na2 CMC, Galaxy LAS, Galaxy LES 70, Galaxy 110, Galaxy CAPB Plus, and Sulfacid K. The lyophilized enzyme also displayed high stability with respect to both solid and liquid detergents. Finally, TN-X30 protease exhibited remarkable destaining of blood, egg, and chocolate stained cloth pieces. These findings may promote TN-X30 protease for use as bioadditive in detergent formulation, thereby reducing environmental chemical threat. 相似文献
The kinetics of oil extraction from olive cake by using ethanol 96% was studied for different solvent-to-solids ratios and
temperatures. The thermodynamic aspect of the extraction process was also examined. In the kinetic study, the results produced
by the model of So and Macdonald (a model involving two main mechanisms of oil extraction: a washing process and a diffusion
process with two stages) were found to be in good agreement with the experimental data. The yield of oil in the extract increased
with increasing contact time, solvent-to-solids ratio and extraction temperature. The calculated values of the mass transfer
coefficients of various stages of the extraction were found to increase linearly with solvent-to-solids ratio and temperature.
In all cases, the predominant mechanism in the extraction was the washing of the oil occurring on the particle surface. The
values of the activation energy were 8.56 kJ mol−1 for the washing stage, 9.88 kJ mol−1 for the first stage of diffusion and 17.55 kJ mol−1 for the second stage of diffusion by changing temperature from 20 to 50 °C. Further, the results obtained from thermodynamic
study of extraction process gave positive values of enthalpy and entropy changes and negative values of change in free energy.
Under the equilibrium conditions, the temperature coefficient was found to be 1.02. 相似文献