CO2 reforming of methane over Ni/ZnAl2O4 catalysts: Influence of Ce addition on activity and stability

The catalytic performance of Ni supported on Ce-promoted ZnAl₂O₄ was evaluated in methane dry reforming. The effect of different nominal loadings of cerium (3, 5 and 7 wt%) in the activity, product yield and stability was studied. Ce presented a promote effect in catalytic activity, product yield and especially in stability. However the catalytic performance was considerably influenced by the amount of cerium. SEM images presented smaller particles and TPR profiles revealed stronger active phase/support interaction by Ce addition which led to increasing methane conversion and decreasing coke deposition. Although high amount of Ce was not in favor of its promoting effect due to aggregation of CeO₂ on the catalyst surface. Among the catalysts investigated, the optimal catalytic activity and stability was achieved over the sample with 5 wt% of cerium.     

Correction to: Deposition of bismuth sulfide and aluminum doped bismuth sulfide thin films for photovoltaic applications

Journal of Materials Science: Materials in Electronics -     

Partial Oxidation of Propane Over Mo1V0.3Te0.23Nb0.12Ox Catalyst in a Fluidized Bed Reactor

A fluidized bed reactor, for the first time, was employed to investigate the partial oxidation of propane to acrylic acid over Mo₁V_0.3Te_0.23Nb_0.12O_x catalyst. Effects of temperature, oxygen concentration, steam concentration, space velocity, and dilution with different sizes of SiC were studied and discussed. The reaction in the fluidized bed was compared with the reaction in the classical fixed bed. The results indicated that at constant temperature propane conversion obtained in the fixed bed reactor was higher. But the fluidized bed recompensed it by higher acrylic acid selectivity leading to acrylic acid yields and formation rates considerably over the fixed bed. In the fluidized bed reactor, an enhancement in the acrylic acid selectivity was observed over fixed bed at similar conversions. It is suggested that passing a large portion of gas phase oxygen through bubbles allows operation under lower oxygen partial pressure, which favors the desired reaction path. With the heat sink feature of the diluent, the catalytic performance is more influenced by dilution in the fixed bed. However, hot spots are less likely to occur in the fluidized bed and dilution has little effect on the catalytic performance. However, propane conversion increases slightly by increasing SiC particle diameter due to better fluidization quality.     

An Insight into the Silanization of Montmorillonite Nanoparticles

The purpose of this study is to investigate the effect of reaction conditions on the silanization of montmorillonite nanoparticles using methacryloxypropyltrimethoxysilane (γ–MPS) and to establish relationships between the reaction conditions, the grafting percentage, and the silane arrangement on the particles. The silanization reaction was performed in the following conditions: (i) acidic ethanol-water solution with a pH of 5 and (ii) basic cyclohexane with a pH of 9. To characterize the surface of montmorillonite nanoparticles, analytical methods such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), CHN elemental analysis, and X-ray diffraction (XRD) diffraction were utilized. In addition, the dispersion stability of modified particles suspended in different solvents was investigated using a separation analyzer. The results revealed silane grafting in cyclohexane (pH?=?9) achieved higher silanization efficiency, leading to a larger basal spacing in montmorillonite nanoparticles. A parallel arrangement was also suggested for the silane molecules on the surface of the nanoparticles. The higher hydrophobicity of the modified nanoparticles and the decreased overall density of the grafted particles led to a better dispersion in ethanol and toluene.     

Uniform Cooling of a Flat Surface by an Optimized Array of Turbulent Impinging Air Jets

Abstract

The aim of this study is to investigate the uniform cooling of a hot isothermal heated target surface, using four turbulent impinging air jets. Eight parameters including the width of jets, the space between the inner jets, the space between inner and outer jets, the distance of jets from the plate, the impingement angle of jets, and the overall volumetric flow rate of the cooling air per unit depth of the nozzle are considered as design variables. The normalized standard deviation of the local Nusselt number from the desired Nusselt number is considered as the objective function. An optimization algorithm based on pattern search method is utilized to obtain the optimum array of the jets. Two different scenarios of the problem are considered, one with fixed normal impingement angles and the other with the optimized angles. Results show an almost uniform distribution of the local Nusselt number. Increasing the amount of desired Nusselt number for the case with fixed impinging angles results in a higher Reynolds number, a wider opening for outer jets and a reduction in jet to jet and jet to surface distances. However, changes in design parameters for the case with optimum impinging angles are erratic.     

Use of Two-Phase Pseudo Pressure Method to Calculate Condensate Bank Size and Well Deliverability in Gas Condensate Reservoirs

This paper introduces a novel approach in the use of two-phase pseudo pressures for the calculation of condensate bank radius and productivity index of wells and the interpretation of gas condensate well test data. It is shown that knowledge of the relationship between condensate saturation and pressure is necessary for the integration of pseudo pressure in all regions of the reservoir. In the region of the reservoir where immobile condensate saturation develops, an equation that is valid for the region far from the wellbore has been used. While for the region where condensate is considered to be mobile, an equation has been used based on the steady state method. This method is tested using a data set that was generated by a compositional simulator for radial homogenous. A set of real PVT data from a producing gas condensate field is used for simulation of the gas condensate reservoir. Using this approach, it is possible to calculate condensate bank radius and total skin, mechanical skin, and permeability of the reservoir, yielding answers that are extremely close to those of the simulator. It is also shown that the condensate saturation profile in the reservoir produced using this method is also similar to the one produced by the simulator. An inflow performance curve is calculated using two-phase pseudo pressures. In this curve, the impact of the presence of condensate around the wellbore on productivity is studied.     

A modified three-phase multistage fluid bed model by considering axial dispersion in bubble side

ABSTRACT

The previously published multistage three-phase model (proposed by El-Halwaghi and El-Rifai) has been improved by considering axial dispersion in the bubble phase. Comparing the predicted results of the developed model with the different experimental data available in the literature showed a close agreement on both axial concentration profile and overall conversions. The presented model is found to be valid over a wider range of operating conditions as compared to the original model. At high reaction rates where the shortcomings of the hydrodynamic model come to light as well as at high superficial gas velocities where the reactant concentration in the bubble side is critical in reactor performances, the developed model gives obviously better results. It has also been shown that the proposed model is attractive in scale-up procedure. The effects of enlargement of bed diameter on reactor performances could be predicted by the presented model more reasonably.     

Deposition of bismuth sulfide and aluminum doped bismuth sulfide thin films for photovoltaic applications

Journal of Materials Science: Materials in Electronics - Binary bismuth sulfide (Bi2S3) and ternary aluminum-doped bismuth sulfide (Al@Bi2S3) thin films were prepared by the chemical bath...