Hydrogenation of p-chloronitrobenzene on Nanosized modifiedNiMoB catalyst
| Autor: | Chia-Hui Cheng, 鄭嘉蕙 |
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| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 Amorphous NiB alloy catalysts are beneficial for the hydrogenation of p-chloronitrobenzene. They possess better catalytic activity and selectivity in the hydrogenation reaction. In this study, we used sodium borohydride to reduce the precursor salts of nickel acetate, ammonium heptamolybdate tetrahydrate and additives (Pd, La, Fe and Co), and prepared a series of modified NiMoB catalyst by chemical reduction method. The molar ratio of Ni/Mo/B/additive was 1: 0.4: 3: 0.1, and an overdose of B was used to completely reduce the precursor salts. Ni catalysts were prepared in 50 vol.% methanolic solution at 298 K under N2 curtain gas with vigorous stirring of 500 rpm. In order to prevent the catalysts from oxidation and deactivation during the preparation, N2 curtain gas was used. The high activity of fresh catalysts was tested for the hydrogenation of p-CNB. The catalysts were characterized by inductively coupled plasma-mass spectrometry (ICP-MS), X–ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). The activity and selectivity of catalysts were tested for the liquid-phase htdrogenation reaction of p-CNB at 1.2 MPa pressure and two different temperatures, 353 K and 333 K, and under vigorous stirring of 500 rpm in the batch reactor (Parr Reactor Model 4842). The reaction medium was 80 ml methanol. During the run, the samples were withdrawn periodically (10 min) and analyzed by a gas chromatography. The results revealed that adding the additives into the catalysts would enhance the dispersing effect of active sites, activity and selectivity. The selectivity of main product, p-chloroaniline (p-CAN) was more than 90%. For modified NiMoB catalysts, La-doped one was better than the other catalysts, and more obvious electron transfer contributed to the best activity and selectivity. In order to study the influence of La/Ni molar ratio on the catalytic activity of La-doped NiMoB catalysts, the molar ratio of La/Ni was modified and found that the La(0.2)-NiMoB catalyst had excellent hydrogenation activity. It achieved 100% conversion within 60 min at 333 K with selectivity of 97.5%. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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