促進劑對非晶形鎳硼觸媒在對氯硝基苯氫化反應的影響

Effect of Additives on Ni-B Colloid Catalysts for the Hydrogenation of p-Chloronitrobenzene

陳亮夫(Liang-Fu Chen)

指導教授 ： 陳郁文

國立中央大學/工學院/化學工程與材料工程學系/碩士(2006年)

摘要

在對氯硝基苯的氫化反應中，非晶形的鎳硼觸媒有狠好的催化活性與選擇性，比較起貴重金屬如鈀或白金，雖然此觸媒有較好的選擇性，但在活性表現上仍較對重金屬遜色許多，本研究的目的在於提高非晶形鎳硼觸媒的催化活性，藉由鉻、鈰、釷、鎢、釕及鉬等金屬鹽類，以一定的含量於鎳硼觸媒製做時導入，針對觸媒在表面積、熱穩定性及催化活性的變化來做討論，在表面積的改變上，改質過與未改質的差異並未很明顯，而在熱穩定性上，可發現改質過後的觸媒均可抑制鎳硼觸媒的結晶現象，且在反應溫度範圍的結構也很穩定，在活性上，除了鉻與鈰外，改質過後的鎳硼觸媒均提高了觸媒活性，其中以鉬在此研究中，有最明顯的改善，其在100℃的活性是鎳硼觸媒的六倍，且能在反應溫度降至50 ℃時，仍有100％的轉化率，藉由實驗數據與儀器分析的結果，來討論改質觸媒特性與催化活性。

關鍵字

對氯硝基苯的氫化反應 ； 促進劑 ； 鎳 ； 奈米觸媒 ； 改質劑

並列摘要

Ni-B amorphous catalysts proved to be a better catalyst on both activity and selectivity for hydrogenation of p-chloronitrobenzene (p-CNB) from previous studies. However, the catalytic activity of Ni-B catalyst did not compete with that of noble metals viz., Pd and Pt. In order to enhance the catalytic activity of Ni-B for the hydrogenation, six additives were introduced into Ni-B amorphous catalyst, including metal salts of Cr, Ce, Th, W, Ru and Mo. A series of modified Ni-B amorphous nanocatalysts were prepared by chemical reduction of mixed salts of the metal additive and nickel acetate tetrahydrate with sodium borohydride in water/methanol solution. The characterization results revealed that at a specific weight ratio of metal dopants, some particles of modified Ni-B catalysts became smaller and have better thermal resistance, and protecting the special amorphous structure even at high temperature. During hydrogenation of p-CNB, some modified Ni-B catalysts have showed lower catalytic activity than unmodified one. However, the catalytic activity of these promoted catalysts are better than Raney nickel used in industries, with high selectivity to the main product of p-CAN (p-chloroaniline). Among these promoted catalysts, Mo-Ni-B showed the best activity and reached almost 100% conversions even at lower reaction temperature of 323K. According to kinetic studies and results of various characterization methods, such as powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and N2 sorption, the correlation of the catalytic performance to both the structural and the electronic characteristics have been arrived and discussed briefly.

並列關鍵字

promoter ； modifier ； hydrogenation of p-chloronitrobenzene ； nanocatalyst ； nickel

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