超小奈米鈀金屬於二維與三維結構中孔洞矽材以及中孔洞碳氮材在有機催化反應之應用;Ultrasmall Palladium Nanoparticles Confined in 2D-3D Mesoporous Silica and Mesoporous Carbon Nitride for the Catalytic Organic Reaction

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题名:	超小奈米鈀金屬於二維與三維結構中孔洞矽材以及中孔洞碳氮材在有機催化反應之應用;Ultrasmall Palladium Nanoparticles Confined in 2D-3D Mesoporous Silica and Mesoporous Carbon Nitride for the Catalytic Organic Reaction
作者:	林家榕;Lin, Chia-Jung
贡献者:	化學學系
关键词:	鈀奈米金屬;催化反應;有序中孔洞矽材;中孔洞碳氮材料;Catalyst
日期:	2019-07-23
上传时间:	2019-09-03 14:28:24 (UTC+8)
出版者:	國立中央大學
摘要:	本論文主要分為兩大部分，在第一部分研究中，超小奈米鈀金屬還原在中孔洞材料之二維結構SBA-15以及三維結構KIT-6之中，利用化學還原劑使金屬還原速率上升，並藉由和SBA-15以及KIT-6表面原有的羥基，使離子鈀金屬能快速平均分散並負載在SBA-15以及KIT-6孔洞之中並還原奈米鈀金屬顆粒。由於SBA-15以及KIT-6具有高比表面積以及良好的孔洞體積，故使用SBA-15以及KIT-6作為載體可以提高奈米鈀金屬分散率和負載率從而提高催化活性。本實驗將製成的Pd(x)@SBA-15以及Pd(x)@KIT-6應用在催化苯乙烯氫化反應當中，分別探討二維結構以及三維結構、不同氫供體以及不同溶劑對催化活性之影響。經過一系列的研究使用Pd(30)@KIT-6作為催化劑去進行催化苯乙烯氫化反應，其轉換頻率（TOF）高達363 h-1。在這項研究中，Pd(30)@KIT-6展示了其用於催化苯乙烯氫化是高活性催化劑。在第二部分研究中，通過奈米模鑄法(Nanocasting)合成出中孔洞碳氮材料（MUFC），並將奈米鈀金屬顆粒負載在MUFC上作為催化觸媒。藉由MUFC上不僅可以利用有缺陷的C-N位點和氮間隙可以很均勻分散鈀金屬顆粒，且由於其具有鹼性的含氮位點可有效促進反應進行，從而提高催化活性。本實驗將Pd(x)@MUFC應用在催化苯甲醇氧化反應當中，分別探討不同載體、不同溶劑以及不同鹼添加試劑對催化活性之影響。在催化苯甲醇氧化反應的研究中Pd(30)@MUFC表現出很高的催化活性，其轉換頻率（TOF）高達750 h-1。在這項研究中，Pd(30)@MUFC展示了其用於催化苯甲醇氧化反應中是高前景催化劑。;This study consists of two main parts. In the first part, the Palladium nanoparticles (Pd NPs) with a particle size of 2-3nm are successfully confined within the 2D mesoporous silica SBA-15 and the 3D mesoporous silica KIT-6. Under the wet impregnation process, SBA-15 and KIT-6 were immersed in Pd2+ precursor and adsorbed into the pores, then. The mixture chemically reduced by reagent containing NaBH4 and NH3BH3 to obtain Pd(x)@SBA-15 and Pd(x)@KIT-6. It was found that the use of SBA-15 and KIT-6 support can highly enhance the dispersion and efficiency due to the high surface area and large pore volume. In addition, SBA-15 and KIT-6 with the pore size of 9.09 nm and 9.56 nm, respectively, may effectively confine the Pd NPs and subsequently avoid the aggregation. According to the X-ray diffraction pattern and TEM image, it can be confirmed that the particle size of Pd NPs is about 2-3 nm and highly dispersed without aggregation. The Pd(x)@SBA-15 and Pd(x)@KIT-6 exhibited superior catalytic activity and chemoselectivity for the catalytic transfer hydrogenation of styrene under mild conditions with formic acid and ammonium formate as a hydrogen donor. Among all the as-prepared catalysts, the Pd(30)@KIT-6 exhibited the highest turnover frequency (TOF) of 363 h-1. In addition, Pd(30)@KIT-6 exhibited an excellent high stability after five successive cycles without significant loss of its catalytic activity. In the second part of study, heteroatom doped carbon materials have received considerable attention in the field of catalysis. Herein, we report a catalyst made of palladium nanoparticles (Pd NPs) supported on mesoporous nitrogen-doped carbon (MUFC), Pd@MUFC. The use of the mixture of melamine-urea-formaldehyde as a precursor and the mesoporous silica SBA-15 as a hard template afforded a high-nitrogen-content mesoporous carbon material that showed high activity in stabilizing Pd NPs. The N-doped mesoporous carbon, MUFC, can provide a large surface area to adsorb the reductant and substrate, and enhance the accessibility of the active sites of the Pd NPs in the catalytic reaction process. When Pd@MUFC was applied as catalyst in the catalytic aerobic oxidation of benzyl alcohol, it achieved conversion rate and selectivity of 99.9% within 30 minutes. Among all the as-prepared catalysts, the Pd(30)@MUFC exhibited the highest turnover frequency of 750 h-1. The remarkable catalytic activity for the benzyl alcohol oxidation can be attributed to the ultra-small Pd NPs confined in the hexagonal N-doped carbonaceous MUFC.
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