Catalytic dehydrogenation of cyclohexane over Ag-M/ACC catalysts for hydrogen supply

Dehydrogenation of cyclohexane to benzene has been carried out over Ag supported on activated carbon cloth (Ag/ACC) catalysts using a spray- pulse reactor. Hydrogen evolution was studied for hydrogen storage and supply system applications. The maximum rate of hydrogen evolution rate using monometallic Ag/ACC catalysts was 6.9 mmol/g_met/min for Ag loading of 10 wt%. An enhanced hydrogen evolution was observed by adding a small amount of noble metal (1 wt% Pt, Pd, Rh) to the Ag based catalysts. A synergistic effect was observed in the case of the Pt promoted catalysts on the hydrogen production were twice as compared to 10 wt% Ag catalyst only.     

Tribological Performance of Boronized,Nitrided, and Normalized AISI 4140 Steel against Hydrogenated Diamond-Like Carbon-Coated AISI D2 Steel

In the current work, AISI 4140 steel was pack-boronized at 950°C for 3 h and gas-nitrided at 550°C for 72 h. All specimens used in this work were prepared from the same steel bar. A 3-µm-thick diamond-like carbon (DLC) coating (a-C:H) was deposited on the AISI D2 high-carbon, high-chromium, cold-worked tool steel by a plasma-assisted chemical vapor deposition technique. Normalized, boronized, and nitrided steel pins were tested against DLC-coated AISI D2 steel at various normal loads (15, 30, 60, and 80 N) for 1,000 and 3,000 m sliding distance in ambient air. Specific wear rate of all pins decreased with increasing load, and a similar trend was observed for the coefficient of friction (COF). Microscopic and energy-dispersive spectroscopic (EDS) analysis confirmed the role of the transfer layer for a low COF with increasing load. At all loads, the specific wear rate of boronized pins was lower than that of the nitrided and normalized pin specimens. Boronized pins showed a specific wear rate in the range of 0.27 × 10^?8 to 0.44 × 10^?8 mm³/Nm and the COF was about 0.1.     

Solvent-Free Selective Oxidation of Benzyl Alcohol and Benzaldehyde by tert-Butyl Hydroperoxide Using MnO- 4-Exchanged Mg–Al–Hydrotalcite Catalysts

MnO^- ₄ (0.4 mmol/g)-exchanged Mg-Al-hydrotalcite is an active and highly selective catalyst for the oxidation of benzyl alcohol to benzaldehyde by tert-butyl hydroperoxide under reflux in the absence of solvent. It also shows high activity for the oxidation of benzaldehyde to benzoic acid. The higher the Mg/Al ratio, the higher is the catalytic activity (in both the reactions) and basicity of the hydrotalcite catalyst.     

Formulation and evaluation of solid self-microemulsifying drug delivery system of chlorthalidone by spray drying technology

The main objective of this study was to prepare a solid self-microemulsifying drug delivery system (S-SMEDDS) by spray drying liquid SMEDDS with an inert solid carrier Aerosil 200 to improve the dissolution rate and permeability of chlorthalidone (CTD). The liquid SMEDDS was composed of CTD, oleic acid, tween 20, and PEG 200. Preliminary screening was performed to select proper component combination. Solubility of CTD was determined in various vehicles. Ternary phase diagram for four series was constructed to delineate the boundaries of the nanoemulsion domain. Optimized S-SMEDDS (S3) was evaluated for dispersibility test (13.30?±?0.95), percentage transmittance (99.50?±?0.002), turbidity (260.43?±?1.02), percent drug content (97.86?±?0.56), droplet size (159.4), polydispersity index (PDI, 0.30), and zeta potential (?12.4). Solid-state characterization was done by scanning electron microscopy (SEM), differential scanning calorimetry, X-ray powder diffraction (XRD), and Fourier transform infrared (FT-IR). The XRD analysis confirmed that there was no crystalline CTD in the S-SMEDDS. SEM study revealed adsorption of liquid SMEDDS on Aerosil 200. In vitro drug release study was performed using water and 0.1N HCl as dissolution medium and compared with plain drug and marketed tablet Thaiklor TM 12.5, and marked increase in rate and extent of dissolution of S-SMEDDS was observed. Ex vivo intestinal permeability study revealed that diffusion of drug was significantly higher from S-SMEDDS than that of suspension of plain drug. The solid SMEDDS formulation was stable. In conclusion, the S-SMEDDS might be an encouraging strategy to improve the oral absorption of CTD.     

Dehydrogenation of methylcyclohexane over Pt/V2O5 and Pt/Y2O3 for hydrogen delivery applications

Dehydrogenation of methylcyclohexane (MCH) for hydrogen transportation and delivery application was carried out over 3 wt% Pt/V₂O₅ and 3 wt% Pt/Y₂O₃ catalyst. The catalytic activity was tested using a spray-pulse mode of reactor. Effective dehydrogenation of MCH under spray-pulse mode of reactant injection was observed. In terms of hydrogen evolution rate at 60 min from start of reaction the activity of 958 mmol/g/min was obtained at temperature of 350 °C. Nearly 100% selectivity toward hydrogen was obtained. A relatively high conversion of 98% was observed with 3 wt% Pt/Y₂O₃ at 60 min using an advanced spray-pulse reactor system. The catalysts were characterized using x-ray diffraction pattern (XRD), CO-chemisorption metal analysis, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis.     

Efficient hydrogen supply through catalytic dehydrogenation of methylcyclohexane over Pt/metal oxide catalysts

This paper describes the results of experiments on dehydrogenation of methylcyclohexane over Pt supported on metal oxides (Pt/MO) and Pt supported on perovskite (Pt/Per) catalysts. The reaction is being considered as a means for delivery of hydrogen to fueling stations in the form of more easily transportable methylcyclohexane. Among Pt/MO catalysts, the best activity as determined by the hydrogen evolution rate was observed over Pt/La₂O₃ catalyst at 21.1 mmol/g_met/min. Perovskite-supported catalysts exhibited relatively higher activity and selectivity, with Pt/La_0.7Y_0.3NiO₃ giving the best performance. This Pt/Per catalyst had an activity of ca 45 mmol/g_met/min with nearly 100% selectivity towards dehydrogenation. The catalysts were characterized using XRD, CO-chemisorption and SEM-EDXA techniques. The present study reports catalysts that minimize the use of Pt and explores tailoring the properties of the perovskite structure.     

Multiband,miniaturized, maze shaped antenna with an air‐gap for wireless applications

A novel maze shaped multiband monopole antenna with a miniaturized size of only 6 × 4 × 1.6 mm³ is proposed. To further achieving excellent radiation performances across the desired operating bands, an air‐gap is set between the proposed antenna and system ground. To assess the performances of the antenna, simulations are initially carried out by loading a 1.6 mm thick nonconducting Polycarbonate material (analogous to an air‐gap) between the antenna and system ground, and a simplified equivalent circuit (EC) model of the proposed antenna is also derived. The proposed antenna has excited two different resonance frequencies, in which the lower band (f_L) and upper band (f_U) can yield broad 10‐dB impedance bandwidths of 6.5% (2.37‐2.53 GHz) and 16% (5.05‐5.90 GHz), respectively. Furthermore, desirable gain and radiation efficiency of 2.85 to 6.40 dBi and 57% to 85%, respectively across the two operating bands were also achieved. A practical experiment is also carried out by installing the proposed antenna into a real laptop computer (L412 Think Pad Lenovo).     

A feasibility analysis of hydrogen delivery system using liquid organic hydrides

The paper discusses the techno-economic feasibility of a hydrogen storage and delivery system using liquid organic hydrides (LOH). Wherein, LOH (particularly cycloalkanes) are used for transporting the hydrogen in chemical bonded form at ambient temperature and pressure. The hydrogen is delivered through a catalytic dehydrogenation process. The aromatics formed in the process are used for carrying more hydrogen by a subsequent hydrogenation reaction. Cost economics were performed on a system which produces 10 kg/h of hydrogen using methylcyclohexane as a carrier. With proprietary catalysts we have demonstrated the possibility of hydrogen storage of 6.8 wt% and 60 kg/m³ of hydrogen on volume basis. The energy balance calculation reveals the ratio of energy transported to energy consumed is about 3.9. Moreover, total carbon footprint calculation for the process of hydrogen delivery including transportation of LOH is also reported. The process can facilitate a saving of 345 tons/year of carbon dioxide emissions per delivery station by replacing gasoline with hydrogen for passenger cars. There is an immense techno-economic potential for the process.     

Non-noble Ni–Cu/ACC bimetallic catalyst for dehydrogenation of liquid organic hydrides for hydrogen storage

The effect of Cu on dehydrogenation activity of Ni has been observed when dehydrogenation of methyl cyclohexane (MCH) was carried out by using bimetallic Ni–Cu supported on activated carbon cloth (ACC) catalysts with various Ni to Cu ratios and constant total metal content of about 10 wt%. The dehydrogenation of MCH was studied for delivery of clean hydrogen to hydrogen fueling station. Catalysts have been synthesized by adsorption method and characterized by atomic absorption spectroscopy (AAS), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Among all combinations of this study 8 wt% Ni + 2 wt% Cu/ACC was found to show strong synergetic effect. This catalyst exhibited relatively high H₂ evolution rate 39.4 mmol/g_met/min during the dehydrogenation of MCH. At the same time methane evolution rate was relatively low which indicated insignificant side reaction of hydrogenolysis. The study reveals that presence of specific amount of Cu enhances the dehydrogenation activity of Ni and suppresses the hydrogenolysis activity for the same. The Ni–Cu/ACC catalyst may be a potential non-noble metal catalyst for dehydrogenation reaction.     

Nitric Oxide Reduction Using Hydrogen Over Perovskite Catalysts with Promotional Effect of Platinum on Catalytic Activity

The catalytic activities of strontium substituted La_0.7Sr_0.3MnO₃ type perovskite catalysts for NO reduction using H₂ as reducing agent has been studied, which is further improved by incorporation of Pt outside (0.1 wt.%Pt/La_0.7Sr_0.3MnO₃) and inside (La_0.7Sr_0.3Mn_0.97Pt_0.03O₃) the perovskite lattice structure. Pt shows excellent enhancement in catalytic selectivity towards N₂ when supported on the perovskite. The catalysts were characterized using thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area. Catalysts evaluations were carried out using thermo-gravimetric analysis coupled with mass spectra (TG-MS).