利用不同基材合成固體有機鹼觸媒以及其在轉酯化的應用

Abstract

利用鎂鋁層狀雙氫氧化物、氫氧化鋯以及商用的矽膠作為基材，嫁接有機胺官能基、胍官能基和咪唑官能基，並使用這些固體有機鹼作為觸媒，檢視其催化轉酯化反應的效果。利用沉澱法合成層間陰離子為十二烷基硫酸根之鎂鋁層狀雙氫氧化物，探討含碳酸根與十二烷基硫酸根的層狀雙氫氧化物對嫁接胺官能基的影響。而合成的鹼觸媒會利用X光粉末繞射鑑定層狀雙氫氧化物結構，使用元素分析搭配熱重分析計算鎂鋁層狀雙氫氧化物、氫氧化鋯以及矽膠嫁接量，並利用氮氣吸附-脫附測量表面積以及孔體積，並使用掃描式電子顯微鏡鑑定觸媒形貌。 在固定醇油比例(6:1)，觸媒量(3wt%)，用嫁接胍官能基的氫氧化鋯催化三酸甘油酯進行轉酯化反應，在40分鐘便可以達到83.9%的conversion，yield可以達到58.2%。

The Mg-Al layered double hydroxides (LDHs), silica gel and zirconium hydroxide grafted with aminopropyl-groups, 3-guanidinylpropyl-groups and 2-formylimidazolylpropyl-groups were prepared and used as the base catalysts for transesterification. LDHs intercalated with carbonate and DS (dodecyl sulfate) were prepared by co-precipitation method, and the effect of interlayer anions on the grafting of amino-groups was examined. The amine-grafted materials were characterized by X-ray diffraction (XRD), nitrogen sorption isotherms, Element Analysis (EA) and thermo-gravimetric analysis (TGA). The catalytic activities of amine-grafted materials were compared with the pristine materials in base-catalyzed transesterification. Transesterification was performed at reflux temperature, using a fixed methanol to triacetin mole ratio of 6:1 and catalyst of 3 wt% (based on the quantity of triacetin used). One-pot transformation of triacetin with methanol using guanidine-grafted Zirconium hydroxide gave a 58.2% FAME yield after 40 min, with 83.9% conversion for transesterification.