Hydrogen production via CO2-reforming of methane over Cu and Co doped Ni/Al2O3 nanocatalyst: impregnation versus sol–gel method and effect of process conditions and promoter

In this study, Cu and Co doped Ni/Al₂O₃ nanocatalyst was synthesized via impregnation and sol–gel methods. The physiochemical properties of nanocatalyst were characterized by XRD, field emission scanning electron microscopy (FESEM), particle size distribution, BET, fourier transform infrared spectroscopy (FTIR), TG–DTA and energy dispersive X-ray (EDX) analysis. The samples were employed for CO₂-reforming of methane in atmospheric pressure, temperature range from 550 to 850 °C, under various mixture of CH₄/CO₂ and different gas hourly space velocity. XRD patterns besides indicating the decline of the peaks intensity in sol–gel method, proved the potential of this procedure in diminishing the crystal size and preventing the NiAl₂O₄ spinel formation. Moreover, high surface area might derive of smaller particle size and uniform morphology of sol–gel prepared ones, confirmed by FESEM and BET analysis. TG–DTG analysis as well supported the higher surface area for sol–gel made ones, represented the proper calcination temperature (approximately 600 °C). Also, presence of the active phases and elemental composition of nanocatalysts determine via EDX analysis. Promoting the basicity and the adsorption rate of CO₂, is attributed to the higher amount of OH groups for sol–gel prepared samples, proved by FTIR. Ni–Co/Al₂O₃ due to the synergetic effect of sol–gel method and cobalt addition depicted excellent characterization such as higher surface area, smaller particle size, supplying more stable support and enhanced morphology. Therefore, this nanocatalyst represented the best products yield (H₂ = 98.21 and CO = 95.64), H₂/CO close to unit (0.92–1.05) and stable conversion during 1,440 min stability test. So, Ni–Co/Al₂O₃ among all of the prepared nanocatalysts demonstrated the best catalytic performance and presented it as a highly efficient catalyst for dry reforming of methane. Despite of the stable yield of Ni–Cu/Al₂O₃, it depicted the lower catalytic activity and H₂/CO ratio than the unprompted nanocatalysts.     

A novel cyclodione coumarin from the stem bark of Mesua beccariana

Our ongoing investigations on the stem bark of Mesua beccariana afforded a novel cyclodione coumarin, beccamarin, together with two known xanthones, mesuarianone, mesuasinone, two anthraquinones, 4-methoxy-1,3,5-trihydroxy-anthraquinone and 2,5-dihydroxy-1,3,4-trimethoxyanthraquinone and one coumarin, mammea A/AB. The structures were elucidated by 1D and 2D NMR and MS techniques.     

Optimal control for unitary preparation of many-body states: application to Luttinger liquids

Many-body ground states can be prepared via unitary evolution in cold atomic systems. Given the initial state and a fixed time for the evolution, how close can we get to a desired ground state if we can tune the Hamiltonian in time? Here we study this optimal control problem focusing on Luttinger liquids with tunable interactions. We show that the optimal protocol can be obtained by simulated annealing. We find that the optimal interaction strength of the Luttinger liquid can have a nonmonotonic time dependence. Moreover, the system exhibits a marked transition when the ratio τ/L of the preparation time to the system size exceeds a critical value. In this regime, the optimal protocols can prepare the states with almost perfect accuracy. The optimal protocols are robust against dynamical noise.     

Modeling and active vibration suppression of a single-walled carbon nanotube subjected to a moving harmonic load based on a nonlocal elasticity theory

This paper investigates active vibration suppression of a single-walled carbon nanotube (SWCNT) under the action of a moving harmonic load using Eringen’s nonlocal elasticity theory. The SWCNT is modeled according to the nonlocal Euler–Bernoulli beam theory. A Dirac-delta function is used to describe the position of the moving load along the SWCNT. Next, a linear classical optimal control algorithm with displacement-velocity feedback is used to suppress vibration in the SWCNT with control forces acting as actuators. The effects of a small-scale parameter, slenderness ratio, moving load velocity, and the excitation frequency of a moving load on the dynamic deflection of the SWCNT are examined. Finally, the ability of the control algorithm to suppress the response of the SWCNT under the effects of a moving load with a number of controlled modes and control forces is surveyed.     

Preparation of Al-magadiite material,copper ions exchange and effect of counter-ions: antibacterial and antifungal applications

Research on Chemical Intermediates - In this work, the Al-magadiite is synthesized by the hydrothermal method. It is then used to prepare three copper exchanged materials using copper nitrate,...     

Effect of magnetic field on laminar forced convective heat transfer of MWCNT–Fe3O4/water hybrid nanofluid in a heated tube

Journal of Thermal Analysis and Calorimetry - A numerical investigation is carried out to assess the hydrothermal performance of a water-based hybrid nanofluid containing both Fe3O4 (magnetite)...     

Robust control of wheel slip in anti-lock brake system of automobiles

In this paper, performances of two model-free control systems including Fuzzy Logic Control (FLC) and Neural Predictive Control (NPC) on tracking performance of wheel-slip in Anti-lock Braking System (ABS) are compared. As an accurate and control oriented model, a half vehicle model is developed to generate extensive simulation data of the braking system. Brake system identification is preformed through a Perceptron neural networks model of brake system which is trained with offline data by Gradient Descent Back Propagation (GDBP) algorithm. In order to reduce the time cost of the calculations and improving the robustness of closed loop control system, an online Perceptron neural network adaptively generates the optimum control actions. By a comparative simulation analysis it is shown that the NPC system has a better tracking performance, shorter stopping time and distance than the FLC controllers. The robustness of the proposed control systems are evaluated under ±25 % uncertainty. It is shown that the NPC system is more robust against both exogenous disturbances and modeling uncertainties than the FLC system.     

Comparison of Syndiotactic Polystyrene Morphology Obtained Via Heterogeneous and Homogeneous Polymerization with Metallocene Catalyst

Summary: Supported catalyst system for the slurry phase polymerization of styrene in toluene was prepared by the immobilization of 2-methylindenyltrichlorotitanium(2-MeIndTiCl₃) on silica and activation of this catalyst was performed by methylaluminoxane(MAO) in polymerization media. Homogeneous polymerization of styrene with 2-methylindenyltrichlorotitanium activated by MAO was performed in toluene. The morphology of obtained syndiotactic polystyrene (sPS) via heterogeneous and homhgeneous catalyst system was compared. Polymerization of styrene by homogeneous catalyst lead to formation of gel and resultant polymers presented a compact and dense texture while the global gelation do not occur with silica supported catalyst at different Ti/SiO₂ mol ratios and sPS was obtained as separated particles. Unlike to the homogeneous catalyst, obtained polymers showed a porous texture. Highly porous texture of sPS was obtained with Ti/SiO₂ = 0.5% mol ratio.