含 Cu -胺基之介孔SBA-15 之合成及其應用在二氧化碳下催化 苯乙炔羧酸化加成反應

Abstract

隨著工業革命的發展，大氣下的溫室氣體逐年增加，因此Carbon dioxide capture and storage (CCS)的研究受到科學家的矚目。近年來，不僅只是研究如何收集二氧化碳，越來越多科學家主要研究方向在如何把二氧化碳轉換成有經濟價值的化學物質。 本研究主要是以一步合成法製備含不同胺基官能之扁平狀SBA-15分子篩，使用tetraethylorthosilicate(TEOS)作為矽源且以非離子型界面活性劑P123(EO20PO70EO20)當作模板，在酸性條件下加入適當的ZrOCl2．8H2O合成具有二維孔洞結構p6mm的扁平狀介孔SBA-15分子篩。再加入含胺基官能基，製備出具有規則排列的骨架結構及孔洞大小相當一致的含胺基官能基介孔SBA-15材料。經由XRD、N2 sorption isotherm、SEM、TGA、Solid state NMR、FT-IR和XAS鑑定，可得知此材料之結構、形貌和證實胺基官能基有鑲嵌在二氧化矽的骨架中。接著，將一價銅離子(Cu+)引入含胺基官能基扁平狀SBA-15內，利用ICP-MS鑑定觸媒中銅的相對含量，並由X光吸收光譜 鑑定材料中銅的價數及配位環境。之後將觸媒應用在二氧化碳下催化苯乙炔羧酸化加成反應，產物羧酸鹽經由甲基化反應轉變成酯，再利用GC-FID偵測產率。不同的溫度和銅量會影響催化結果，Cu-10%-diamine-p-at-HMDS催化乙炔加成反應，經16小時後產率可得到72%，另外 Cu-10%-guanidine-p-at催化苯乙炔加成反應，經16小時後產率可得到42%，Cu-10%-NH2-p-at和Cu-10%-NH2-p-at-HMDS在相同條件下，其產率分別為74%和69%。可能因素為guanidine為強鹼，會與酸性產物有作用，因此無法脫附而進行下一步甲基化反應，而再生後Cu-10%-guanidine-p-at觸媒的產率有明顯下降，歸因於觸媒上的銅，在反應過程中可能有流失，導致效果變差。而SBA-15表面 矽烷醇基(Si-OH)經過HMDS甲基修飾後的Cu-10%-guanidine-p-at-HMDS催化苯乙炔加成反應16 小時後得到的產率為66%。觸媒第一次再生後，其催化活性維持不變，但第二次再生之後，產率有輕微的降低。此外，反應需添加Cs2CO3無機鹼，才能得到較高的產率。

Carbon dioxide is a green house gas. Abrupt raising the concentration of CO2 in atmosphere due to rapid consumption of fossil fuels has caused the global warming. The transformation of CO2 into value-added compounds has been considered to be one of the important ways in CO2 capture and storage. Up to now, various methods have been developed in order to transform CO2 into useful chemicals like esters, cyclic carbonate, formic acid, methanol, ureas and so on. SBA-15 mesoporous silica materials with high surface area, large pore of 5~10 nm in diameter and narrow pore-size distribution have attracted much attention in recent years for their applications in sorption and catalysis, especially for bulky molecules often encountered in reactions of fine chemicals and pharmaceuticals. Copper incorporated on functionalized SBA-15 can be used as recyclable catalysts in the homocoupling reaction of terminal alkynes, C-H activation, and decarboxylation of aromatic carboxylic acid. In this work, platelet SBA-15 materials were functionalized with propylamine, diamine- and guanidine- groups through one-pot co-condensation of tetraethylorthosilicate (TEOS) and amino-containing trimethoxysilane in the presence of P123 as pore-directing agent and appropriate amount of Zr(Ⅳ) ions. The resultant materials were characterized by XRD, N2 sorption isotherm, TGA, SEM, FT-IR, Solid NMR, and XAS. Cu-amine-SBA-15-p materials were examined as the catalysts in carboxylation of phenylacetylene with CO2. The yield of phenylpropiolic acid product was determined by GC-FID after methylation reaction. The optimal yield of methyl phenylpropynoate up to 72% was obtained over Cu-diamine-SBA-15-p-at-HMDS after 16 h reaction at 80℃ under ambient pressure. In the same condition, the yield of Cu-10%-prNH2-p-at and Cu-10%-prNH2-p-at-HMDS was 74% and 69%, respectively. The yield was lower down when the reaction temperature was increased or the amount of copper was decreased. Besides, The yield of methyl phenylpropynoate up to 42% was obtained over Cu-guanidine-SBA-15-p-at after 16 h reaction at 80℃ under ambient pressure, attributed to guanidine group without chelating with copper had the stronger interaction than the other functional group with adsorbed acidic product. Modification of SBA-15 surface by methylation of silanol groups with HMDS would decrease catalytic activity. The optimal yield of methyl phenylpropynoate of 66% was obtained over Cu-guanidine-SBA-15-p-at-HMDS after 16 h reaction at 80℃ under ambient pressure. However, Cu-guanidine-SBA-15-p-at-HMDS could be reused at least once without significant loss of activity. Addition of Cs2CO3 as additives was essential to achieve good yield of methyl phenylpropiolate.