Study of mechanism and kinetic modeling of CO hydrogenation reaction over the impregnated Co-Ni/Al2O3 catalyst

An investigation of the kinetic and mechanism of CO hydrogenation reaction was performed on impregnated Co-Ni/Al₂O₃. Determination of kinetic parameters from the experiments was carried out in a micro fixed-bed reactor. Kinetic evaluations were performed under various operational conditions of T = 473–673 K, p = 1–14 bar, H₂/CO = 1–3, and GHSV = 4,500 hr⁻¹. Kinetic models and rate equations for CO consumption were obtained by using two main-type rate equations of Langmuir-Hinshelwood-Hougen-Watson (LHHW) and Eley-Rideal (ER). Estimation of various kinetic parameters was performed using a nonlinear regression method. According to the obtained experimental results and using statistical criteria, one kinetic expression based on the LHHW mechanism (-r_CO = k_p.b_CO.P_CO. b_H2. P_H2/[1+ b_CO.P_CO + b_H2.P_H2]²) was chosen as the best-fitted model. For this fitted model, the activation energy was found to be 109.2 kJ/mol. Characterization of the catalyst was also performed using X-ray diffraction (XRD), BET, scanning electron microscopy (SEM), and energy-dispersive x-ray spectrometer (EDS) techniques.     

DFT calculations,microsynthesis and characterization of isopropyl methylphosphonoselenofluoridate [sarin-Se]

Abstract

Isopropyl methylphosphonoselenofluoridate (sarin-Se) was synthesized in order to determine its analytical data and to compare them as well as its reactivity parameters with those of sarin. After synthesis, sarin-Se was characterized using ¹ Mesilaakso, M. In: Mesilaakso, M. (Ed.), Introduction, Chemical Weapons Convention Analysis, Sample Collection, Preparation and Analytical Methods, Wiley, Chichester, 2005.[Crossref] , [Google Scholar]H, ¹³ Rayman, M. P.; Infante, H. G.; Sargent, M. Food-Chain Selenium and Human Health: spotlight on Speciation. Br. J. Nutr. 2008, 100, 238–253.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]?C and ³¹P NMR spectroscopy and high resolution mass spectrometry (HRMS). ¹ Mesilaakso, M. In: Mesilaakso, M. (Ed.), Introduction, Chemical Weapons Convention Analysis, Sample Collection, Preparation and Analytical Methods, Wiley, Chichester, 2005.[Crossref] , [Google Scholar]H and ¹³ Rayman, M. P.; Infante, H. G.; Sargent, M. Food-Chain Selenium and Human Health: spotlight on Speciation. Br. J. Nutr. 2008, 100, 238–253.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]?C NMR chemical shifts were also calculated using density functional theory (DFT) and compared with experimental data, showing a close agreement. Electrophilicity indices of sarin and sarin-Se were calculated at B3LYP/6-31++G (2d, 2p) level of theory. HOMO-LUMO analysis provides a basis to explain electrophilic nature of sarin-Se and sarin, which are almost similar. Based on calculated data, ³¹P NMR chemical shift and the reactivity of sarin-Se towards some enzymes such as acetylcholinesterase and albumin were explained.     

3D quantum mechanical simulation of square nanowire MOSFETs by using NEGF method

In order to investigate the specifications of nanoscale transistors, we have used a three dimensional (3D) quantum mechanical approach to simulate square cross section silicon nanowire (SNW) MOSFETs. A three dimensional simulation of silicon nanowire MOSFET based on self consistent solution of Poisson-Schrödinger equations is implemented. The quantum mechanical transport model of this work uses the non-equilibrium Green’s function (NEGF) formalism. First, we simulate a double-gate (DG) silicon nanowire MOSFET and compare the results with those obtained from nanoMOS simulation. We understand that when the transverse dimension of a DG nanowire is reduced to a few nanometers, quantum confinement in that direction becomes important and 3D Schrödinger equation must be solved. Second, we simulate gate-all-around (GAA) silicon nanowire MOSFETs with different shapes of gate. We have investigated GAA-SNW-MOSFET with an octagonal gate around the wire and found out it is more suitable than a conventional GAA MOSFET for its more I _on /I _off , less Drain-Induced-Barrier-Lowering (DIBL) and less subthreshold slope.     

3-Bihom-ρ-Lie Algebras, 3-Pre-Bihom-ρ-Lie Algebras

The purpose is to introduce the notions of 3-Bihom-ρ-Lie algebras and 3-preBihom-ρ-Lie algebras. The authors describe their constructions and express the related lemmas and theorems. Also, they define the 3-Bihom-ρ-Leibniz algebras and show that a3-Bihom-ρ-Lie algebra is a 3-Bihom-ρ-Leibniz algebra with the ρ-Bihom-skew symmetry property. Moreover, a combination of a 3-Bihom-ρ-Lie algebra bracket and a Rota-Baxer operator gives a 3-pre-Bihom-ρ-Lie algebra structure.     

Simulation of fluid-structure interaction in a microchannel using the lattice Boltzmann method and size-dependent beam element on a graphics processing unit

Fluid-structure interaction （FSI） problems in microchannels play a prominent role in many engineering applications. The present study is an effort toward the simulation of flow in microchannel considering FSI. The bottom boundary of the microchannel is simulated by size-dependent beam elements for the finite element method （FEM） based on a modified cou- ple stress theory. The lattice Boltzmann method （LBM） using the D2Q13 LB model is coupled to the FEM in order to solve the fluid part of the FSI problem. Because of the fact that the LBM generally needs only nearest neighbor information, the algorithm is an ideal candidate for parallel computing. The simulations are carried out on graphics processing units （GPUs） using computed unified device architecture （CUDA）. In the present study, the governing equations are non-dimensionalized and the set of dimensionless groups is exhibited to show their effects on micro-beam displacement. The numerical results show that the displacements of the micro-beam predicted by the size-dependent beam element are smaller than those by the classical beam element.     

Interacting ghost dark energy in Brans-Dicke theory

We investigate the QCD ghost model of dark energy in the framework of Brans-Dicke cosmology. First, we study the non-interacting ghost dark energy in a flat Brans-Dicke theory. In this case we obtain the equation of state and the deceleration parameters and a differential equation governing the evolution of ghost energy density. Interestingly enough, we find that the equation of state parameter of the non-interacting ghost dark energy can cross the phantom line (wD=−1) provided the parameters of the model are chosen suitably. Then, we generalize the study to the interacting ghost dark energy in both flat and non-flat Brans-Dicke framework and find out that the transition of wD to phantom regime can be more easily achieved for than when resort to the Einstein field equations is made.     

Crystallization of Liquid Gold Nanoparticles by Molecular Dynamics Simulation

Molecular dynamics simulation of the crystallization behavior of liquid gold (Au) nanoparticles, with 1, 2, 3, 4, 5 and 6 nm in diameter, on cooling has been carried out based on the embedded-atom-method potential. With decreasing cooling time, the final structure of the particle changes from amorphous to crystalline structure. We showed that the structure of the fully crystallized particle is polycrystalline face-centered cubic (FCC). The FCC structure of the gold nanoparticle is proved energetically the most stable form. And the final structure of nanoparticles is affected by cooling time and size of nanoparticles. We also showed that the melting point of particles is affected by size of nanoparticles.     

Dispersive liquid–liquid microextraction using extraction solvent lighter than water

For the first time a dispersive liquid–liquid microextraction method on the basis of an extraction solvent lighter than water was presented in this study. Three organophosphorus pesticides (OPPs) were selected as model compounds and the proposed method was carried out for their preconcentration from water samples. In this extraction method, a mixture of cyclohexane (extraction solvent) and acetone (disperser) is rapidly injected into the aqueous sample in a special vessel (see experimental section) by syringe. Thereby, a cloudy solution is formed. In this step, the OPPs are extracted into the fine droplets of cyclohexane dispersed into aqueous phase. After centrifuging the fine droplets of cyclohexane are collected on the upper of the extraction vessel. The upper phase (0.40 μL) is injected into the gas chromatograph (GC) for separation. Analytes were detected by a flame ionization detector (FID) (for high concentrations) or MS (for low concentrations). Some important parameters, such as the kind of extraction and dispersive solvents and volume of them, extraction time, temperature, and salt amount were investigated. Under the optimum conditions, the enrichment factors (EFs) ranged from 100 to 150 and extraction recoveries varied between 68 and 105%, both of which are relatively high over those of published methods. The linear ranges were wide (10–100 000 μg/L for GC‐FID and 0.01–1 μg/L for GC‐MS) and LODs were low (3–4 μg/L for GC‐FID and 0.003 μg/L for GC‐MS). The RSDs for 100.0 μg/L of each OPP in water were in the range of 5.3–7.8% (n = 5).     

Determination of trace amounts of thallium by adsorptive cathodic stripping voltammetry with xylenol orange.

Trace amounts of thallium(I) can be determined using adsorptive cathodic stripping voltammetry in the presence of Xylenol Orange (XO). The reduction current of the thallium(I)-XO complex ion was measured by square-wave cathodic stripping voltammetry. The peak potential was at -0.44 V vs. Ag/AgCl. The effect of various parameters (pH, ligand concentration, accumulation potential and collection time) on the response are discussed. The response was linearly related to the thallium concentration in the range 0.5-110 ng ml(-1) and 110-2000 ng ml(-1). The limit of detection was 0.2 ng ml(-1). The relative standard deviation for the determination of 80 ng ml(-1) thallium was 2.8%. Many common anions and cations did not interfere with the determination of thallium. The interference of lead was reduced by the addition of 0.003 M sodium carbonate. The voltammetric procedure was then successfully applied to the determination of thallium in various complex samples.