SBA-15負載鎢鋯金屬氧化物對甘油的氣相脫水反應研究

Abstract

介孔洞材料SBA-15具有高的比表面積，以及均勻的六方角柱規則孔洞，加上有良好的水熱穩定性，使得其成為良好的觸媒載體。故將低表面積的鎢鋯氧化物負載於在SBA-15身上增加鎢鋯氧化物的比表面積。本實驗是利用超臨界乙醇共沉澱法將鎢鋯氧化物負載於SBA-15孔洞材料身上，利用超臨界流體的特性，讓鎢鋯氧化物的分散性達到更好，來探討甘油脫水得到丙烯醛反應的反應活性。探討利用不同的氧化鎢和氧化鋯以及SBA-15的三者比例、此複合材料的鍛燒溫度、以及酸量的多寡。利用超臨界乙醇共沉澱法製成的鎢鋯氧化物複合材料，在低角度的X光繞射實驗得知，複合材料保有原本的SBA-15規則六角柱狀排列。而且從氮氣吸脫附實驗可以得到高表面積的觸媒材料。相較於直接含浸法，所合成的觸媒材料的混和金屬氧化物顆粒會阻塞且填滿介孔洞SBA-15的孔道。合成出的觸媒應用在固定床氣相甘油的脫水反應，實驗得知丙烯醛 (acrolein) 為主要生成物，且有甘油脫一次水的產物丙酮醇(hydroxyacetone)與乙醛為其他副產物。

Zirconia loaded with tungsten oxide (abbreviated as WZ) has been reported to be an efficient catalyst in dehydration of glycerol to form acrolein. In the present study, mesoporous SBA-15, which has very high surface area and a uniform hexagonal array of channel-shaped mesopores, was used as the support for preparing supported WZ catalyst (abbreviated as WZ/SBA-15) in order to increase the surface area of tungstated zirconia. Different methods for preparing the supported catalysts were compared. The catalysts prepared through supercritical ethanol were found to retain well ordered porous structure based on small angle X-ray diffraction. The acidities were examined by NH3-TPD and FT-IR, The gas-phase dehydration of glycerol in the presence of water was investigated at temperatures around 290 oC. Factors of catalyst preparation such as the weight ratios of tungsten and zirconium to SBA-15, the calcination temperature of the catalysts, and various silica supports in influencing the catalytic performances were examined.