發(fā)布時(shí)間：2018-06-07 14:38

  本文選題：電紡絲技術(shù) + 鎳納米粒子��； 參考：《內(nèi)蒙古工業(yè)大學(xué)》2017年碩士論文

【摘要】：分布廣泛的鎳基納米材料由于價(jià)格低廉受到廣大研究者的關(guān)注。而以鎳基復(fù)合材料作為催化劑,得到了更廣泛的研究。其中對(duì)于Heck反應(yīng)的研究已經(jīng)具有了一定的深度,對(duì)于鈀基催化劑,負(fù)載型鎳基催化劑具有獨(dú)特的優(yōu)點(diǎn)。本文結(jié)合靜電紡絲、氫氣還原以及高溫碳化技術(shù),制備了具有良好形貌、高效催化活性以及可循環(huán)使用的鎳基碳納米纖維復(fù)合催化劑,具體研究如下:(1)利用靜電紡絲技術(shù)為基礎(chǔ)制備以無機(jī)氯化鎳為鎳源的納米纖維膜,結(jié)合兩種還原方法(氫氣高壓還原和氫氬混合氣常壓高溫還原)制備鎳碳纖維復(fù)合材料(Ni/CNFs)。通過系列表征方法對(duì)兩種鎳基纖維復(fù)合材料的纖維形貌、鎳納米粒子尺寸及分布和鎳的價(jià)態(tài)進(jìn)行了詳細(xì)的檢測(cè)分析:表明制備的復(fù)合催化劑具有好的纖維形貌且粒徑較小的鎳納米粒子在碳纖維中均勻分布,納米鎳以面心立方結(jié)構(gòu)晶型存在并為零價(jià)鎳。通過Heck反應(yīng)考察了兩種復(fù)合材料的催化性能,當(dāng)碳化溫度為500°C時(shí)兩種催化劑催化Heck反應(yīng)均具有較好的轉(zhuǎn)化率。比較兩種不同鎳基催化劑的催化結(jié)果,確定:高壓氫氣還原法制備的Ni(0)/CNFs具有較好的催化性能,故最適合的還原條件為高壓氫氣還原。(2)結(jié)合上述研究,以乙酰丙酮鎳鹽為鎳源,結(jié)合靜電紡絲技術(shù),利用高壓氫氣還原以及高溫碳化制備了Ni/CNFs。通過SEM、TEM、XPS等表征結(jié)果表明Ni/CNF排列整齊、光滑無節(jié)點(diǎn),鎳納米粒子分布均勻、尺寸均一,并且形成了零價(jià)鎳。根據(jù)Heck反應(yīng)結(jié)果表明,與無機(jī)鎳鹽比較,有機(jī)鎳鹽為鎳源制備的催化劑更穩(wěn)定,催化及循環(huán)性能更好,且具有一定的底物拓展能力。(3)為了提升機(jī)鎳鹽制備鎳基催化劑的催化性能,引入造孔劑聚甲基丙烯酸甲酯(PMMA)。通過對(duì)材料的表征,確定制備的鎳基多孔復(fù)合催化劑(Ni/PCNFs)具有良好的形貌和鎳納米粒子的分布,并形成了多孔結(jié)構(gòu),直徑分布在3 nm左右的零價(jià)鎳納米粒子均勻分布在碳纖維載體中。造孔劑有效的改善了催化性能偏低的缺點(diǎn)。碳化過程中PMMA分解,并在碳纖維上形成了孔結(jié)構(gòu),從而增加了底物與鎳活性位點(diǎn)的接觸,提高了反應(yīng)速率和轉(zhuǎn)化率。所以,制備的多孔碳纖維載鎳復(fù)合催化劑對(duì)Heck反應(yīng)具有更高效的催化性能。綜上所述,本文主要以靜電紡絲技術(shù)為基礎(chǔ),利用氫氣還原以及高溫碳化過程制備了可循環(huán)且高效的碳纖維負(fù)載鎳復(fù)合催化劑。碳纖維承載鎳基復(fù)合催化劑具有優(yōu)異的性能,有望取代鈀等貴金屬催化劑,并廣泛應(yīng)用于Heck反應(yīng)中。碳纖維不僅作為金屬載體,碳具有一定的還原性還可以進(jìn)一步保護(hù)制備的零價(jià)鎳納米粒子。負(fù)載型鎳基催化劑不僅僅在研究中展現(xiàn)出潛在的價(jià)值,而且在工業(yè)產(chǎn)業(yè)中也將具有應(yīng)用價(jià)值。
[Abstract]:Widely distributed nickel-based nanomaterials have attracted much attention due to their low price. The nickel matrix composite was used as catalyst, and more extensive research was carried out. The study of Heck reaction has a certain depth, and the supported nickel catalyst has a unique advantage for palladium based catalyst. In this paper, nickel based carbon nanofiber composite catalysts with good morphology, high catalytic activity and recyclability were prepared by electrospinning, hydrogen reduction and high temperature carbonization. The main results are as follows: (1) using electrospinning technology to prepare nanofiber membrane with inorganic nickel chloride as the source, and combining two reduction methods (hydrogen reduction under high pressure and hydrogen argon mixture at atmospheric pressure and high temperature reduction) to prepare Ni / CNFsO / Ni / CNFsN composite. The fiber morphology of two kinds of nickel matrix fiber composites was characterized by a series of characterization methods. The size and distribution of nickel nanoparticles and the valence states of nickel were analyzed in detail. The results showed that the prepared composite catalysts had good fiber morphology and the smaller nickel nanoparticles were uniformly distributed in carbon fiber. Nanocrystalline nickel exists in the crystal form of face centered cubic structure and is zero valence nickel. The catalytic properties of the two composite materials were investigated by Heck reaction. When the carbonization temperature was 500 擄C, the catalytic activity of the two catalysts for Heck reaction was better. Comparing the catalytic results of two kinds of nickel based catalysts, it is determined that the Ni(0)/CNFs prepared by high pressure hydrogen reduction method has better catalytic performance, so the most suitable reduction condition is high pressure hydrogen reduction. (2) combined with the above research, the nickel acetylacetone salt is used as nickel source. Ni / CNFs were prepared by high pressure hydrogen reduction and high temperature carbonization combined with electrostatic spinning technology. The results showed that the Ni/CNF was neatly arranged, smooth without nodes, uniform distribution of nickel nanoparticles, uniform size, and the formation of zero-valence nickel. According to the results of Heck reaction, compared with inorganic nickel salt, the catalyst prepared by organic nickel salt is more stable, and its catalytic and cycling performance is better than that of inorganic nickel salt. In order to improve the catalytic performance of nickel salt to prepare nickel based catalyst, a pore-making agent polymethyl methacrylate (PMMA) was introduced. Through the characterization of the material, it was confirmed that the prepared Ni-base porous composite catalyst (Ni / PCNFs) had good morphology and distribution of nickel nanoparticles, and formed a porous structure. Nickel nanoparticles with a diameter of about 3 nm were uniformly distributed in carbon fiber carriers. The pore-making agent can effectively improve the low catalytic performance. During carbonation, PMMA was decomposed, and the pore structure was formed on carbon fiber, which increased the contact between substrate and nickel active site, and increased the reaction rate and conversion rate. Therefore, the prepared porous carbon fiber supported nickel composite catalyst has a more efficient catalytic performance for Heck reaction. In conclusion, based on electrostatic spinning technology, carbon fiber supported nickel composite catalysts were prepared by hydrogen reduction and high temperature carbonization. Carbon fiber supported nickel based composite catalysts have excellent performance and are expected to replace palladium and other noble metal catalysts and are widely used in Heck reactions. Carbon fiber is not only used as metal carrier, but also can protect the prepared nickel nanoparticles. Supported nickel based catalysts not only show potential value in research, but also have application value in industrial industry.
【學(xué)位授予單位】：內(nèi)蒙古工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O621.251

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