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نویسندگان مقالات پربازدید :
مجله مهندسی شیمی
جزئیات رویداد
همایش ، رویداد ، ژورنال
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  • the role of hydrogen partial pressure in the gas phase hydrogenation of p-chloronitrobenzene over alumina supported au and pd: a consideration of reaction thermodynamics and kinetics

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    • تاریخ ارائه: 1392/01/01
    • تاریخ انتشار در تی پی بین: 1392/01/01
    • تعداد بازدید: 657
    • تعداد پرسش و پاسخ ها: 0
    • شماره تماس دبیرخانه رویداد: -
     the gas phase hydrogenation of p-chloronitrobenzene (p-cnb) over alumina supported au and pd has been subjected to thermodynamic and kinetic analyses where the h2partial pressure was varied from excess (h2/p-cnb up to 2300) to lean (stoichiometric) conditions. the catalysts have been characterised by temperature-programmed reduction (tpr), h2 chemisorption/temperature-programmed desorption (tpd), bet surface area/porosity, x-ray diffraction (xrd), x-ray photoelectron spectroscopy (xps) and transmission electron microscopy (tem) measurements. both catalysts exhibited nano-scale metal particles (mean diameter = 4.5 nm (au) and 2.4 nm (pd)) with the formation (from xps analysis) of electron-rich pdδ− but no significant electron transfer between au and al2o3. under thermodynamic control, cyclohexane is the only product where h2/p-cnb ⩾ 10 with product (p-chloroaniline, aniline, chlorobenzene, benzene and cyclohexane) dependence on h2/p-cnb in the range 1–8; at a given h2/p-cnb, reaction temperature (373–473 k) has a negligible effect. under conditions of catalytic control, au/al2o3 generated p-chloroaniline as the sole product while pd/al2o3 promoted hydrodechlorination to nitrobenzene and hydrogenation to aniline. a kinetic model is presented that accounts for the rate dependence on h2 partial pressure, where the maximum turnover frequency delivered by au/al2o3 (with a lower h2 adsorption coefficient) was an order magnitude lower than that recorded for pd/al2o3. adsorption ofp-cnb on pdδ−via the aromatic ring is proposed that serves to activate both –no2 and –cl for attack whereas au/al2o3 selectively activates –no2, leading to exclusive production of p-chloroaniline.

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