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具羧酸官能基之二維結構SBA-15中孔洞矽材(S15C20)以及三維結構KIT-6中孔洞矽材(K6C20)之中。利用化學還原劑使金屬還原速率上升，並藉由S15C20以及K6C20表面原有的羥基及官能化的羧酸基，使離子鈀金屬能快速平均分散並負載在孔洞之中並還原奈米鈀金屬顆粒。由於S15C20以及K6C20具有高比表面積以及良好的孔洞體積，故使用S15C20以及K6C20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)@S15C20以及Pd(x)@K6C20應用在催化氯苯加氫脫氯反應當中，分別探討二維結構以及三維結構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(2)@K6C20作為催化劑去進行氯苯加氫脫氯反應，其轉換頻率 (TOF) 達50 h-1。在這項研究中，Pd(2)@K6C20展示了其應用於催化氯苯加氫脫氯是高活性的催化劑。 在第二部分研究中，接續使用與第一部分相同的催化劑。本實驗將Pd(x)@S15C20以及Pd(x)@K6C20應用在催化六價鉻還原反應當中。在催化六價鉻還原反應的研究中Pd(0.5)@S15C20表現出很高的催化活性，其TOF高達8.85 min-1。在這項研究中，Pd(0.5)@S15C20展現出其作為催化六價鉻還原反應的催化劑是非常具有前景的。 ;The use of palladium nanoparticles (Pd NPs) as catalysts for various c catalytic reactions is getting tremendous attention recently because of their high catalytic activity and stability. However, the Pd NPs aggregates very easily due to the high surface energy, which reduces the stability of the catalyst considerably. Synthesis of stable and highly dispersed Pd nanoparticles remains a great challenge. In this thesis, synthesis of highly dispersed Pd NPs using –COOH functionalized 2D hexagonal mesoporous silica SBA-15 (S15C20) and –COOH functionalized 3D cubic mesoporous silica KIT-6 (K6C20) as the supports have been reported. Mesoporous silica supports S15C20 and K6C20 are prepared by one pot co-condensation method. The Pd nanoparticles are immobilized within the mesopores of the supports S15C20 and K6C20 by double agent chemical reduction method. The particle size of Pd NPs ranges from 5.0 to 6.3 nm and 4.8 to 6.0 nm for Pd(x)@S15C20 and Pd(x)@K6C20, respectively, depending on molar amount of Pd loadings. The formation of highly dispersed Pd nanoparticles within the supports could be attributed to the homogenous distribution of the –COOH functional groups in S15C20 and K6C20. The prepared Pd(x)@S15C20 and Pd(x)@K6C20 are used as catalysts for the catalytic hydrodechlorination of chlorobenzene, and the catalytic reduction of environmentally harmful Cr(VI) to Cr (III). Pd(x)@S15C20 and Pd(x)@K6C20 exhibited superior catalytic activity for the catalytic hydrodechlorination of chlorobenzene under mild conditions with ammonium formate (HCOONH4) as a hydrogen donor. Amongst all the catalysts, Pd(2)@K6C20 exhibits the highest turnover frequency (TOF) of 50 h-1. The Pd(2)@K6C20 also exhibited excellent stability after used for three successive cycles without significant loss of its catalytic activity. Both the prepared catalysts Pd(x)@S15C20 and Pd(x)@K6C20 could effectively reduce environmentally harmful Cr(VI) to Cr (III) in presence of reducing agent formic acid (HCOOH) and promoter sodium formate (HCOONa) under mild conditions. Amongst all the catalysts, Pd(0.5)@S15C20 exhibited the highest turnover frequency of 8.85 min-1. In addition, Pd(0.5)@S15C20 showed excellent stability and recyclability which could retain high conversion after reuse for five times.
