Highly active three-dimensional cage type mesoporous ferrosilicate catalysts for the Friedel–Crafts alkylation

Three-dimensional cage type ferrosilicate catalysts with different n_Si/n_Fe ratios (FeSBA-1(x) where x denotes the n_Si/n_Fe molar ratio) have been prepared at a molar hydrochloric acid to silicon ratio of 10 using cetyltriethylammonium bromide as the template. The obtained materials have been unambiguously characterized by XRD, N₂ adsorption, and ESR spectroscopy, and their catalytic activity in the benzylation of benzene and the substituted benzene has also been investigated. The catalytic results of the FeSBA-1 catalysts with different n_Si/n_Fe ratios have been compared with the uni-dimensional FeSBA-15, AlSBA-15 and FeHMS catalysts. It has been found that the activity of the FeSBA-1 catalysts is much higher as compared to that of the FeSBA-15, FeHMS and AlSBA-15 catalysts. The activity of the catalysts declines in the following order: FeSBA-1(36) > FeSBA-1(90) > FeSBA-1(120) > FeSBA-1(344) > FeSBA-15(152) > FeHMS(50) > AlSBA-15(45). The effect of various reaction parameters such as reaction time, reaction temperature, reactant feed ratio and the various electron donating groups on the benzene ring affecting the activity and selectivity of FeSBA-1(344) have also been studied. The catalysts are highly active and show a complete conversion of benzyl chloride and a clean selectivity to diphenylmethane (DPM) within a short period of time under the optimized reaction conditions. The reaction kinetics of the catalysts has been extensively investigated and the results are presented. The apparent rate constant of the FeSBA-1(344) and the BC conversion sharply increase with increasing the reaction temperature. The activity of the FeSBA-1(344) catalyst for the benzylation of different aromatic compounds is in the following order: benzene > anisole > mesitylene > p-xylene > toluene.     

Evaluation of bond integrity in sandwiched structures by dry couplant ultrasonic technique

The ultrasonic dry-couplant technique has been used to evaluate adhesive bonds in honeycomb and aluminium-fibre reinforced plastic-aluminium sandwich materials. The technique does not require conventional liquid couplant. Both pitch-catch and through transmission methods were adopted. Disbonds have been successfully detected and evaluated using the technique.     

Enhancement of photocatalytic activity by metal deposition: characterisation and photonic efficiency of Pt, Au and Pd deposited on TiO2 catalyst

Pt, Au and Pd deposited TiO2 have been prepared and characterised by surface analytical methods such as surface area, XRD, and scanning electron micrograph and photophysical characterisation by diffuse reflectance spectroscopy. The photocatalytic activity of the doped catalysts was ascertained by the photo-oxidation of leather dye, acid green 16 in aqueous solution illuminated with low-pressure mercury lamp ( approximately 254 nm). The effect of metal contents on the photocatalytic activity was investigated. The highest photonic efficiency was observed with metal deposition level of less than 1 wt%.     

Energy efficient and secured distributed data dissemination using hop by hop authentication in WSN

Wireless Networks - Dissemination is a service provided for Wireless Sensor Networks to update the deployed sensor nodes online by using over air programming through radio communication. Since the...     

Analytical solution for combined economic and emissions dispatch

Due to the environmental concerns that evolve from the emissions produced by fossil-fuelled power plants, the economic dispatch that minimises only the total fuel cost can no longer be considered single-handed. This paper proposes an analytical strategy based on mathematical modelling to solve economic, emission, and combined economic and emission dispatch problems by a single equivalent objective function. The proposed strategy has been applied to dissimilar realistic systems at different load conditions and the outcome of one such realistic system is presented here.     

Cobalt oxides as Co2B catalyst precursors for the hydrolysis of sodium borohydride solutions to generate hydrogen for PEM fuel cells

Cobalt boride (Co₂B) is an inexpensive catalyst for the hydrolysis of sodium borohydride (NaBH₄) to generate hydrogen (H₂) for PEM fuel cells. Preparation of Co₂B in situ in the H₂ generation vessel as well as in an external reactor was studied using cobalt (III) oxide (Co₃O₄) and lithium cobalt oxide (LiCoO₂) as precursors. The oxide precursors were characterized by XRD and the Co₂B catalysts by XRD and ICP. Co₂B formation from the oxide precursors depends on the crystallinity of the oxides as well as the concentration of NaBH₄ in the solution. During reduction of the oxides to CoB₂, Co(s) metal, Co(BO₂)₂ may also form from competing side reactions, however crystalline oxides react faster leading to higher Co₂B yield and better H₂ generation efficiency. Crystallinity of Co₃O₄ was improved by preparing it at a higher temperature. Co₃O₄ prepared at 600 °C reacts faster leading to enhanced Co₂B formation than Co₃O₄ prepared at lower temperatures (200 °C and 400 °C). The activation energy for the hydrolysis of NaBH₄ by Co₂B formed in situ from Co₃O₄ produced at 600 °C was calculated to be 77.90 kJ mol⁻¹. This activation energy value is found to be slightly higher than that of Pt, Ru-based catalysts.     

Real-time decay of fluorinated fullerene molecules on Cu(001) surface controlled by initial coverage

Nano Research - In this study, the evolution of C60F18 molecules on a Cu(001) surface was studied by means of scanning tunneling microscopy and density functional theory calculations. The results...     

Q-learning based routing for in-network aggregation in wireless sensor networks

Wireless Networks - In-network data aggregation is an inherent paradigm that extends the lifetime of resource-constrained wireless sensor networks (WSNs). By aggregating sensor data at...     

Equilibrium and kinetic studies on the removal of Acid Red 114 from aqueous solutions using activated carbons prepared from seed shells

The use of low-cost and ecofriendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. This paper deals with the removal of Acid Red 114 (AR 114) from aqueous solutions using activated carbons prepared from agricultural waste materials such as gingelly (sesame) (Sp), cotton (Cp) and pongam (Pp) seed shells. Optimum conditions for AR 114 removal were found to be pH 3, adsorbent dosage=3g/L of solution and equilibrium time=4h. Higher removal percentages were observed at lower concentrations of AR 114. The adsorption isotherm data were fitted to Langmuir and Freundlich equation, and the adsorption capacity of the studied adsorbents was in the order Sp>Cp>Pp. Kinetic studies showed that the adsorption followed both pseudo-second-order and Elovich equation. The thermodynamics parameters such as DeltaG degrees, DeltaH degrees, DeltaS degrees were also evaluated. The activated carbons prepared were characterized by FT-IR, SEM and BET analysis.     

Synthesis and evaluation of polythiocyanogen (SCN)x as a rechargeable lithium-ion battery electrode material

Polythiocyanogen, (SCN)_x, is a promising lithium-ion battery electrode material due to its high theoretical capacity (462 mAh g⁻¹), safe operation, inexpensive raw materials, and a simple and less energy-intensive manufacturing process. The (SCN)_x was prepared from the solution of trithiocyanate (SCN)₃⁻ in methylene dichloride (MDC), which was prepared by electrochemical oxidation of ammonium thiocyanate (NH₄SCN) in a two-phase electrolysis medium of 1.0 M NH₄SCN in 0.50 M H₂SO₄ + MDC. The (SCN)₃⁻ underwent auto catalytic polymerization to (SCN)_x during MDC removal. Battery electrodes with (SCN)_x as the active material were prepared, and tested in Swagelok cells using lithium foil as the counter and reference electrode. The cells delivered capacities in the range of 200-275 mAh g⁻¹ at the discharge-charge rate of 0.2 C. The cells were tested up to 20 cycles and showed repeatable performance with a coulombic efficiency of 97% at the 20th cycle. The results presented here indicate that (SCN)_x is a promising lithium-ion battery electrode-material candidate for further studies.