NOPR Collection:

Effect of oxygen and oxidizers on the electrochemical behaviour of a-brass in aqueous solutions of different pH

1998-01-01T00:00:00Z

Title: Effect of oxygen and oxidizers on the electrochemical behaviour of a-brass in aqueous solutions of different pH Authors: AI-Kharafi, F M; Badawy, W A Abstract: The electrochemical behaviour of a-brass (Cu:Zn ≈ 70:30) in naturally aerated, oxygen saturated and oxygen free acidic, neutral and basic solutions of constant pH has been investigated. The effect of oxygen and oxidizers on the corrosion behaviour of the alloy in the different solutions has been discussed. The effect of oxygen or oxidizers on the corrosion parameters of the alloy is dependent on the solution pH. The removal of oxygen or oxidizers from acidic solutions increases the corrosion resistance of the alloy. In these solutions, the presence of oxygen or oxidizers enhances disproportionation reactions which lead to the breakdown of the passive film formed on the alloy surface. The preferential dissolution of zinc has been found to destroy the passive film, especially in acidic solutions. X-ray photoelectron spectroscopic investigations (XPS) of the alloy surface after long immersion time in solutions containing Cr₂O ions have shown that chromium is not incorporated in the barrier film. Scanning electron microscopy (SEM) does not show remarkable difference between the polished surface and the surface after immersion in the test solutions. In-acidic solutions containing dichromate ions increased corrosion rates have been measured and clear corrosion patterns in the scanning electron micrographs have been recorded. Page(s): 29-34

Alkylation of naphthalene with methanol over modified zeolites

1998-01-01T00:00:00Z

Title: Alkylation of naphthalene with methanol over modified zeolites Authors: Kulkarni, S J; Murthy, K V V S B S R; Nagaiah, K; Kumar, V Sylesh; Rao, Y V Subba; Subrahmanyam, M; Rao, A V Rama Abstract: The alkylation of naphthalene with methanol was carried out Over various modified HZSM-5 and HY zeolites. HY zeolite was modified considering the following three steps: (i) V-zeolite was dealuminated to stabilise the structure (ii) promoted with La³⁺ or Ce³⁺ to enchance the alkylation activity and (iii) modified by Mg²⁺ or K⁺ to reduce acidity and deactivation. MgLaY zeolite was observed as the better catalyst in this reaction. Page(s): 62-64

Can Mo-silicalite-1 be an efficient catalyst for the isomerization of 1-butene to iso-butene?

1998-01-01T00:00:00Z

Title: Can Mo-silicalite-1 be an efficient catalyst for the isomerization of 1-butene to iso-butene? Authors: Raghavan, P S; Mirajkar, S P Abstract: The role of iso-butene has always been dominant in petrochemical industries, which is produced by the skeletal isomerization of 1-butene. Application of the acid catalysts for the above reaction leads to more cracking than isomerization while over non-acidic catalysts conversion was found to be less. Here, attempts to synthesize A1 free Mo containing silicalites have been made which was found to give better activity for the above reaction. The reaction was carried out at different temperatures; space velocities; catalysts containing different Mo content and the results are discussed. Page(s): 59-61

Computer-aided reaction design in pericyclic reactions by using Turbo C

1998-01-01T00:00:00Z

Title: Computer-aided reaction design in pericyclic reactions by using Turbo C Authors: Reddy, B Sreenivasa; Dutta, Pradip K Abstract: A new concept for the search of unprecedented chemical reactions is presented. With the help of Turbo C (a high level computer language) the complete set of six-centre six-electron (6C-6e) pericyclic reactions has been generated. It looks like a set of known and unknown reactions. The unknown reactions can be predicted and some of them have been successfully performed in the laboratory. In this paper, the design of these new reactions aimed at the synthesis of given classes of compounds is described. Page(s): 56-58