The effect of the superposition of an alternating current on a direct current on the electrodeposition of nickel-​iron alloys

Electrodeposited Ni-​Fe alloys show a variable compn. when electroplated in the presence of a superimposed a.c. The alloy compn. depends on the ratio of the a.c. to the d.c., the frequency, the amplitude and the waveform. By a suitable choice of conditions the electrodeposited Ni-​Fe alloy can be prepd. with a specified compn. throughout. A mechanism for the action of the a.c. on the d.c. which produces the specified compn. is proposed

Esterification of dicarboxylic acids to diesters over Mn+-montmoril lonite clay catalysts

Esterification of dicarboxylic acids with various alcohols and phenols in presence of metal exchanged montmorillonite clay catalyst (Mn+-mont; Mnþ ¼ Al3þ, Fe3+, Cr3+, Zn2+, Mn2+, and Ni2+) is studied. Among the catalysts used, Al3+-mont was found to be the most effective, as it gave good to excellent yields of esters under mild reaction conditions. The heterogeneous catalyst presented here can be regenerated and reused. All these features indicate the high potential of the reaction as ‘‘green chemistry’’ process

Brønsted and Lewis acidity of modified montmorillonite clay catalysts determined by FT-IR spectroscopy

The surface acidity of different modified montmorillonite clay catalysts, Al3+-exchanged montmorillonite (Al3+-Mont) and aluminium pillared montmorillonite (Al-PILC) was determined by DRIFTS (diffuse reflectance Fourier transform infrared spectra) using pyridine as probe molecule. The method involved treating the clay sample directly with pyridine, drying the sample at 120 °C and recording FT-IR spectra in the region 1650 and 1350 cm−1. The spectra obtained showed well resolved absorption bands for Lewis and Brønsted acid sites in the clay catalysts. In order to understand the role of acid sites present on clay catalysts, esterification of propionic acid with p-cresol has been studied. The Brønsted acidity data obtained by FT-IR study for modified montmorillonite clay catalysts correlated well with the catalytic activity in the esterification reaction. Among the modified clay catalysts, Al3+-Mont and H+-Mont clay catalysts showed good activity and Al-PILC showed negligible activity in esterification. The inactivity of Al-PILC catalysts is attributed to the absence of Brønsted acidity

Synthesis of phenylacetates using aluminium-exchanged montmorillonite clay catalyst

Liquid phase esterification of phenylacetic acid with phenol and substituted phenols has been investigated over montmorillonite clay exchanged with H + - Al 3+ - and aluminium polyhydroxy oligomer cations. Among the catalysts studied, Al 3+ - montmorillonite dried at 100°C showed 67 conversion, while the same catalyst dried at 200deg;C showed reduced conversion of 36. Al 3+ - montmorillonite dried at 400°C and montmorillonite exchanged with aluminium polyhydroxy oligomer cations dried at 100°C and calcined at 500°C failed to bring about the reaction. Effects of mole ratio of reactants, reaction period and catalyst amount on yield of the ester and catalyst regeneration are also investigated. Esterification of phenylacetic acid with phenol, cresols, nitrophenols and resorcinol has been carried out in the presence of montmorillonite clay exchanged with H +-ions, Al 3+-ions and polyhydroxy oligomer cations of Al. Na +-montmorillonite (raw clay) was inactive, H +- and Al 3+-montmorillonites, dried at 100°C, showed 52 and 67 conversions to ester, respectively, upon refluxing the phenylacetic acid (20 mmol) and p-cresol (40 mmol) for 6 h. While Al 3+- montmorillonite dried at 200°C showed a conversion of 36 the same catalyst when dried at 400°C showed no conversion. Montmorillonite exchanged with aluminium polyhydroxy oligomers dried at 100°C and calcined at 500°C to get pillared clay (d 0 0 1=17.5 à ) failed to bring about the esterification. Effect of concentration of reactants, amount of catalyst and the reaction time on the yield of p-cresyl phenylacetate has been investigated. The esterification of phenylacetic acid with phenol and substituted phenols like m-cresol, o-cresol, p-nitro phenol and o-nitro phenol showed reduced yield due to steric factors. The activity of the clay catalyst after regeneration has also been studied. © 2004 Published by Elsevier B.V

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The effect of the superposition of an alternating current on a direct current on the electrodeposition of Ni-Fe alloys

Electrodeposited Ni-Fe alloys show a variable composition when they are electroplated in the presence of a superimposed alternating current. The alloy composition depends on the ratio of the alternating to the direct current, the frequency, the amplitude and the waveform. By a suitable choice of conditions the electrodeposited Ni-Fe alloy can be prepared with a specified composition throughout. A mechanism for the action of the alternating current on the direct current which produces the specified composition is proposed. © 1981

Acid activated indian bentonite, an efficient catalyst for esterification of carboxylic acids

The preparation, characterization, and catalytic properties of acid activated Indian bentonite (AAIB) are reported. AAIB has been characterized by XRD (basal spacing, 15.05 à ), specific surface area (273 m 2/g), pore volume and pore diameter using BET method, TGA, SEM, and surface acidity by n-butylamine back titration method and infrared spectroscopy using pyridine as a probe molecule. The activity of Montmorillonite K10, ZrO 2, S-ZrO 2, p-toluenesulfonic acid (p-TSA), Indian bentonite (IB), and AAIB was investigated by the esterification of p-cresol with stearic acid. Among the catalysts, AAIB was found to be more active. The esterification of various carboxylic acids with phenols and alcohols was studied on AAIB to obtain corresponding esters in good yields. The regeneration and reusability of AAIB has also been investigated. © 2008 Springer Science+Business Media, LLC