Preparation, characterization and properties of Ru porphyrin/mcm-41 catalyst

Abstract

Mesoporous molecular sieve MCM-41 has been modified with 3-amino-propyltriethoxysilane, and the modified product, MCM-41 (m), exhibits a powerful encapsulation ability for [RuL(CO)(EtOH)] (L = meso-tetrakis (4-chlorophenyl) porphyrin). Encapsulated products, designated as Ru/MCM-41 (m) , with Ru porphyrin content ranging from 0.1 % ∼8.3 % were obtained and characterized by means of XRD, DTA-TG, UV-Vis spectrum and others. Experimental results indicate that the Ru porphyrin molecules were dispersed in the channels of MCM-41 (m) as single molecule and not as crystal state. After encapsulation the main structure of the Ru porphyrin is retained and its thermal stability is increased. The immobilization of the Ru porphyrin onto the channel surface of MCM-41 (m) is attributed to a ligand exchange reaction. The Ru/MCM-41 (m) with low Ru content possesses high catalytic activity and this is due to efficient site isolation and good diffusion pathways. The turnover number for oxidation of six alkenes catalyzed by O. 1 % Ru/MCM-41 (m) is 20-40 times higher than that by free [RuL(CO)(EtOH)]. The Ru/MCM-41(m) catalysts have shape selectivity, long service life and can be easily recovered by filtration.

應用3- 氨丙基三乙氧基矽烷對MCM- 41 介孔分子篩進行了改性. 改性產物( 記為MCM- 41( m) ) 具有較強的裝載釕卟啉[ Ru( Ò ) L ( CO) ( EtOH ) ] ( L = meso- tetrakis( 4- clo rophenyl) porphyr in) 的能力. 製備了裹載01 1%~ 813%釕卟啉的產物( 記為Ru/ MCM- 41( m) ) . 應用X 射線衍 射、差熱- 熱失重分析和紫外- 可見光譜等方法對裹載產物進行了表徵. 結果表明, 釕卟啉在MCM- 41( m) 孔道中是以單分子態存在, 而不是以晶態存在. 裝載後釕卟啉仍保持其基本結構, 並且熱穩 定性增加. 軸向配體取代反應使釕卟啉固定在MCM-41( m) 孔道表面上. 低釕含量的Ru/MCM- 41 ( m) 具有高催化活性, 這是有效的位置分離和擴散孔道通暢的結果. 以01 1%Ru/MCM- 41( m) 和自 由的釕卟啉為催化劑進行的6 種烯烴的氧化反應結果表明, 前者的催化轉換數是後者的20~ 40 倍. Ru/ MCM- 41( m) 催化劑具有特殊的形狀選擇性, 較長的壽命, 並且容易過濾回收.