• Banumathi Arabindoo

      Articles written in Journal of Chemical Sciences

    • Isomorphous substitution of Mn(II), Ni(II) and Zn(II) in AlPO-31 molecular sieves and study of their catalytic performance

      V Umamaheswari C Kannan Banumathi Arabindoo M Palanichamy V Murugesan

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      Isomorphously substituted molecular sieves, MAPO-31, NAPO-31 and ZAPO-31, were prepared under mild hydrothermal conditions from gels containing sources of aluminium, phosphorus, appropriate metal and dipropylamine (DPA), presumably acting as a structure-directing template. They were characterized by XRD, FTIR, TGA, inductively coupled plasma (ICP), ESR, Brunauer, Emmett, Teller (BET) and diffusion reflectance spectroscopy (DRS) techniques. In the XRD, the peak at 2θ = 16.7° of the metal substituted AlPO-31 is more intense than that of pure AlPO-31 suggesting preferential occupation of the plane corresponding to it as compared to other planes. The O-H stretch in the IR spectra of the metal-substituted molecular sieves is blue-shifted with respect to the parent AlPO-31 molecular sieves possibly due to metal substitution. Theg values obtained from the ESR spectra of MAPO-31 and NAPO-31 also substantiate framework substitution. Ethylation of toluene was carried out between 300 and 450°C over the above catalysts as a model test reaction. The high toluene conversion over metal-substituted molecular sieves proves the isomorphic substitution of metal ions in the AlPO-31 framework.

    • Vapour phase alkylation of ethylbenzene witht-butyl alcohol over mesoporous Al-MCM-41 molecular sieves

      Vumamaheswari M Palanichamy Banumathi Arabindoo V Murugesan

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      The alkylation of ethylbenzene witht-butyl alcohol was studied over Al-MCM-41 (Si/Al = 50 and 90) and Al, Mg-MCM-41 (Si/(Al+Mg) = 50) in the vapour phase from 200 to 400°C. The products werep-t-butylethylbenzene (p-t-BEB),p-t- butylvinylbenzene (p-t-BVB) andm-t-butylethylbenzene (m-t-BEB). Ethylbenzene conversion decreased with increase in temperature and increase in the ethylbenzene content of the feed. The reaction between the freely diffusing ethylbenzene in the channel and thet-butyl cations remaining as charge compensating ions yieldedp-t- BEB.p-t-BVB, an unexpected product in this investigation, was produced by dehydrogenation ofp-t-BEB over alumina particles present in the channels of the molecular sieves. Adsorption of ethylbenzene on Brønsted acid sites and its subsequent reaction with very closely adsorbedt-butyl cations proved to be necessary to obtainm-t-BEB. Thoughm-t-BEB was obtained, the correspondingm-t-butylvinylbenzene was not observed in this study. Study of time durations indicated rapid and slow catalyst deactivation at lower and higher streams respectively.

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