制备方法对NiP非晶态合金性质及催化活性的影响
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摘要: 分别使用三种方法制备了NiP非晶态合金:次磷酸钠还原镍盐(方法1)、次磷酸镍自分解(方法2)和使用有机胺调节溶液pH值的次磷酸还原镍盐(方法3)。研究了产品的物性,并以环丁烯砜加氢反应为探针检测了NiP非晶态合金的催化活性。研究结果表明,次磷酸钠体系制备的产品性质比较稳定,条件的改变对产物性质的影响不显著,催化活性一般在50%~60%之间;次磷酸镍体系中制备的样品显示出较高的催化活性,环丁烯砜转化率在90%以上;次磷酸体系制备样品的性质对条件变化较为敏感,催化剂的活性在70%~98%之间波动。发现方法2得到的NiP非晶态合金呈现为分散的完美的球形颗粒,且颗粒之间不存在聚集现象;使用方法3可以得到高比表面积的NiP非晶态合金。两种新方法所制备的NiP非晶态合金具有较小的粒径、较高的比表面积、较高的热稳定性和较高的催化反应活性。Abstract: NiP amorphous alloy catalysts were prepared via three different ways, reduction of Ni2+ by NaH2PO2 (method 1), self-oxidation and reduction of Ni(H2PO2)2 (method 2), and the reduction of Ni2+ by H3PO2 with amine adjusting the pH value of solution (method 3). All the NiP samples have amorphous structure inferred from the X-ray Diffraction (XRD) patterns. But the catalysts prepared by the two new methods show smaller particle size and higher surface area than the samples by method 1, and they show higher catalytic activity in the hydrogenation of sulfolene evaluated in a 250 mL autoclave. In order to exhibit the influence of preparation methods on properties of NiP samples, three samples were prepared at the same conditions via different ways, respectively, which were signed as NiP-4 (from method 1), NiP-5 (from method 2) and NiP-9 (from method 3). Transmission Electron Microscope (TEM) images show these samples have different shapes and sizes. NiP-4 sample has not very regular shape. NiP-5 particles are isolated balls while the shape of NiP-9 is near spherical. Their average particle sizes are about 160?nm, 30?nm and 10?nm, respectively. Extend of surface oxidation increases with the particle size decreasing. Crystallization performance of these amorphous alloys is determined by Differential Scanning Calorimetry (DSC) analysis. Their crystallization temperature is in the order of NiP-9 (682 K) > NiP-5 (679 K) > NiP-4 (625 K), which means their structure stability in the same order.
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Key words:
- NiP amorphous alloy /
- sodium hypophosphite /
- nickel hypophosphite /
- hypophosphite acid /
- sulfolene /
- hydrogenation
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