Platinum‐promoted fibrous silica Y zeolite with enhanced mass transfer as a highly selective catalyst for n‐dodecane hydroisomerization

A fibrous silica zeolite Y (HY@KCC‐1) catalyst with a high surface area of 568 m²/g and unique core‐shell morphology was successfully synthesized via a modified KCC‐1 synthesis method. Characterization of the catalysts was achieved with X‐ray powder diffraction (XRD), field emission scanning microscope (FESEM), N₂ adsorption/desorption, and 2,6‐dimethylpyridine adsorbed Fourier‐transform infrared spectroscopy (FTIR). The Pt/HY@KCC‐1 has displayed complete n‐dodecane conversion coupled with an incredibly enhanced isomer yield of 72% at 350°C, nearly two‐fold higher than that of unmodified Pt/HY catalyst. Remarkably, Pt/HY@KCC‐1 had an internal effectiveness factor (η) of unity and negligible internal diffusion limitation, thus suggesting its potential application in hydroisomerization of higher hydrocarbons for enhancing fuel properties.     

Performance analysis of an air rock thermocline TES tank for concentrated solar power plants using the coupled DEM–CFD approach

Clean Technologies and Environmental Policy - One of the most common solutions currently available to meet future energy needs in the world is concentrated solar power (CSP) plants combined with...     

Adomian decomposition method for the effect of transpiration on natural convection MHD flow in a vertical annulus with heat generation/absorption

This article studies the effect of transpiration on a fully developed natural convection MHD flow in a vertical annulus with heat generation/absorption. The governing coupled differential equations are solved by an estimated analytical method identified as the Adomian decomposition method with initial conditions and an appropriate initial guess condition. Furthermore, the effect of several parameters illustrating the flow phenomena is considered through graphs and the numerical computations are obtained and presented through tables. However, it is observed that there is a decrease in velocity due to the effect of the suction of fluid on the heated porous wall with concurrent injection. Also, heat generation parameter enhances the temperature of the fluid on both the isothermal and constant heat flux.     

Ni/Pd-promoted Al2O3–La2O3 catalyst for hydrogen production from polyethylene terephthalate waste via steam reforming

Ni/Pd-co-promoted Al₂O₃–La₂O₃ catalysts for selective hydrogen production from polyethylene terephthalate (PET) plastic waste via steam reforming process has been investigated. The catalysts were prepared by impregnation method and were characterized using XRD, BET, TPD-CO₂, TPR-H₂, SEM, TGA and DTA. The results showed that Ni-Pd-co-impregnated Al₂O₃–La₂O₃ catalyst has excellent activity for the production of hydrogen with a prolong stability. The feed conversion of 87% was achieved over 10% Ni/Al₂O₃ catalyst which increased to 93.87% in the case of 10% Ni-1% Pd/Al₂O₃–La₂O₃ catalysts with an H₂ fraction of 0.60. The catalyst performance in term of H₂ selectivity and feed conversion was further investigated under various operating parameters, e.g., temperatures, feed flow rates, feed ratios and PET concentrations. It was found that the temperature has positive effects on H₂ selectivity and conversion, yet feed flow rate has the adverse effects. In addition, PET concentrations showed improved in H₂ selectivity in comparison to when only phenol as a solvent was involved. The Ni particles, which are the noble-based active species are more effective, thus offered good hydrogen production in the PET steam reforming process. Incorporation of La₂O₃ as support and Pd as a promoter to the Ni/Al₂O₃ catalyst significantly increased catalyst stability. The Ni–Pd/Al₂O₃–Al₂O₃ catalyst showed remarkable activity even after 36 h along with the production of carbon nanotubes, while H₂ selectivity and feed conversion was only slightly decreased.     

Mediation Model for Improving Cost Factors That Affect Performance of Small-Scale Building Construction Contract Business in Nigeria: A PLS-SEM Approach

Performance of small-scale building construction contract business poses a challenge to the sustainable development of the construction industry, particularly in developing countries like Nigeria. Small-scale construction contract business plays an important role in the economic development of any nation. In Nigeria, small-scale construction contract business has a tremendous role in the development of rural areas. This study assesses the mediation effects of client support with advance payment on cost factors that affect performance of small-scale contract businesses in Nigeria. The study identified three factors that affect cost performance of construction projects in developing countries: cash flow problems, effects of fraudulent practices, and effects of the nature of construction environments. In total, 550 survey questionnaires were administered to stakeholders in the Nigerian construction industry. Stratified proportionate random sampling method was used for the selection of respondents and 387 questionnaires were returned, with 357 used in the analysis.     

Kikuchi's necrotizing lymphadenitis. Clinical and pathological study of a new case

Contribution to the topic with the case of a woman, 24, admitted in our ENT Department for exam and treatment of multiple right sided adenopathies of the neck. The histopathological study was consistent with diagnosis of Kikuchi's necrotizing lymphadenitis. This is a new clinicopathologic entity first described, 1972, by Kikuchi, of unknown etiology, an a picture characterized for painful cervical lymphadenitis presented in young women and healing spontaneously after 2-3 months course. We want to emphasize in this paper the scarcity of cases published and the difficulties arising when dealing with the differential diagnosis with lympho-proliferative malignancies as well.     

Kinetic modeling of oxidative dehydrogenation of propane with CO2 over MoOx/La2O3–Al2O3 in a fluidized bed

A 4-step kinetic model of CO₂-assisted oxidative dehydrogenation (ODH) of propane to C₂/C₃ olefins over a novel MoO_x/La₂O₃–γAl₂O₃ catalyst was developed. Kinetic experiments were conducted in a CREC Riser Simulator at various reaction temperatures (525–600 °C) and times (15–30 s). The catalyst was highly selective towards propylene at all combinations of the reaction conditions. Langmuir-Hinshelwood type kinetics were formulated considering propane ODH, uni- and bimolecular cracking of propane to produce a C₁-C₂ species. It was found that the one site type model adequately fitted the experimental data. The activation energy for the formation of propylene (67.8 kJ/mol) is much lower than that of bimolecular conversion of propane to ethane and ethylene (303 kJ/mol) as well as the direct cracking of propane to methane and ethylene (106.7 kJ/mol). The kinetic modeling revealed the positive effects of CO₂ towards enhancing the propylene selectivity over the catalyst.     

Role of suction/injection and slip flow on hydromagnetic free convective flow in a vertical coaxial cylinder under the influence of radial magnetic field

This investigation attempts to address heat and mass transfer behavior exhibited by a steady fully developed natural convective flow of a viscous, incompressible, and electrically conducting fluid in a vertical porous annulus in the presence of radially applied magnetic field and velocity slip. The motion of the fluid in the annular gap is triggered by the buoyancy forces due to temperature gradient of the inner and outer cylinders. The governing momentum and energy equations responsible for the flow are transformed into dimensionless forms using the appropriate dimensionless parameters. Accordingly, analytical solutions of the energy and momentum fields are derived with the appropriate boundary conditions. The effects of the controlling parameters involved in the flow on the temperature field, velocity field, and drag on the walls of the cylinders are illustrated graphically and with the aid of tables. Findings affirm that fluid temperature can be decreased/increased by increasing suction/injection on the porous wall. Furthermore, the fluid flow in the annular gap can be enhanced by increasing Grashof number, fluid injection, and velocity slip.     

On the effect of heat generation/absorption on magnetohydrodynamic free convective flow in a vertical annulus: An Adomian decomposition method

This article deliberates fully developed natural convective flow of heat-generating/absorbing fluid in open-ended vertical concentric annulus under a magnetic field. The momentum and energy equations which arise from the definition of velocity and temperature are written in the dimensional form and then recast into the nondimensional form. Approximate solutions are obtained by using the semi-analytical Adomian decomposition method. The solutions for the velocity, temperature, skin friction, mass flux and rate of heat transfer are obtained. The influence of physical parameters such as heat generation/absorption parameter $\left(\delta \right)$ and Hartmann number (M) are illustrated with the aid of graphs and tables. In the course of this investigation, it is found that an increase in the heat generation/absorption parameter increases the temperature. In addition, the magnitude of the temperature is higher for heat-generating fluid in comparison to heat-absorbing fluid. Furthermore, the temperature and velocity can be controlled by carefully selecting suitable values of the heat generation/absorption parameter and Hartmann number respectively.