改質鎳硼觸媒在對氯硝基苯氫化反應的研究; Hydrogenation of p-Chloronitrobenzene on modified-NiB Catalysts

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Title:	改質鎳硼觸媒在對氯硝基苯氫化反應的研究;Hydrogenation of p-Chloronitrobenzene on modified-NiB Catalysts
Authors:	蘇鎮芳;Jenn-Fang Su
Contributors:	化學工程與材料工程研究所
Keywords:	觸媒;鎳硼;Catalyst;NiB
Date:	2010-06-16
Issue Date:	2010-12-08 13:34:57 (UTC+8)
Publisher:	國立中央大學
Abstract:	非晶相鎳硼合金觸媒於對-氯硝基苯氫化反應上有很好的催化活性和選擇性，這項研究主要為不同添加劑對鎳硼觸媒氫化反應活性影響。鉬及鈀為添加劑，硼氫化鈉為還原劑，以化學還原法在室溫下製備改質後的非晶相鎳硼合金觸媒；製備溶劑使用50 vol. %甲醇之混合溶劑；為避免製備過程中，觸媒被溶氧氧化使得活性降低，因此在製備環境中通以氮氣流，並探討其物理與化學特性於對-氯硝基苯氫化反應上的影響。以感應耦合電漿、X光繞射儀、穿透式電子顯微鏡、高解析度穿透式電子顯微鏡、X光能譜散佈分析儀和X光光電子能譜儀等儀器鑑定其物理、化學特性和表面性質；以液相選擇性對-氯硝基苯氫化反應來測試觸媒的活性與選擇性，反應條件設定在：反應器為半批式反應器 (Parr Reactor Model 4842)；反應溫度為353 K；壓力為1.2 MPa；攪拌速率500 rpm；反應溶劑為甲醇；結果顯示鉬和鈀的加入，扮演著分散劑的腳色，避免觸媒聚集，強化觸媒的熱穩定度、活性位置的分散性，提升反應的活性和選擇率，並皆以非晶相狀態存在。從X光光電子能譜儀分析結果，鉬同時以元素態和氧化態存在，和有著最適當的添加量；不同的添加劑會影響觸媒表面各元素比例及表面電子轉移，進而達到催化鎳硼觸的效果；以鈀改質後的鎳硼觸媒具有強的磁性。而後針對未改質與鉬改質之鎳硼觸媒進行觸媒壽命測試，在相同的反應條件下，連續進行3次批次反應測試，結果顯示鉬改質之鎳鈷硼觸媒則能有效地使觸媒壽命延長。 NiB alloy catalyst has been reported to be a good catalyst for the hydrogenation of p-chloronitrobenzene to p-chloroaniline. The objective of this study was to investigate the effects of Mo and Pd contents on the catalytic properties of NiB in the hydrogenation of p-chloronitrobenzene. A series of NiB catalysts with various modifiers (Mo, and Pd) were prepared by chemical reduction method using NaBH4 as the reducing agent at 298 K. The catalysts were characterized by inductively coupled plasma-mass spectrometry, X–ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive spectrometer, and X-ray photoelectron spectroscopy. The catalytic properties of these catalysts for p–chloronitrobenzene (p-CNB) hydrogenation were studied. Adding proper content of modifiers improved the activity, selectivity and thermal stability of NiB. Both of the modified catalysts Mo-NiB and Pd-NiB processed amorphous structure. The Pd and Mo acted as the spacer to prevent the NiB particles from aggregation, so the particle sizes of the modified catalysts were less than that of the unmodified NiB catalysts. Furthermore, the Magnetization of ultrafine particles remarkably increase with doping Pd into NiB. XPS results showed that molybdenum modifier existed both in elemental and oxidized states. Different modifiers had various effects on the surface composition of NiB catalyst. The elemental state of modifier( Mo and Pd) formed nano-alloy with Ni and affected their electron densities which influenced the products distributions (the relative contents of p–chloronitrobenzene, aniline, and nitrobenzene) in the p-CNB hydrogenation. The life time tests NiB and Mo-NiB were also studied. The results showed that Mo additive could extend the life of NiB. After the hydrogenation reaction, the NiB catalyst sintered to numerous large grains. However, Mo-NiB retained the original black nano-clusters and the catalytic activities were maintained at high level after 3 batch runs. These effects were responsible for the different behaviors of Mo-, and Pd-modified NiB catalysts in the p-CNB hydrogenation.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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