含釕金屬之催化劑於自致熱乙醇轉氫之研究

Abstract

在本實驗中，我們成功合成出兩種不同結構的催化劑，分別是Ce0.7La0.3O2-σ以及La2Zr2-xRuxO7 (x=0~0.4)，並應用在自致熱乙醇轉氫的反應上。合成出的粉體利用X光粉末繞射儀、掃描式電子顯微鏡、感應耦合電漿原子發射光譜分析儀、氮氣等溫吸/脫附儀、程溫還原反應以及X光光電子能譜儀去分析、鑑定材料的性質。 在第一部分，我們利用水熱、微波、共沉澱、溶膠凝膠等四種不同方法製備Ce0.7La0.3O2-σ催化劑，探討不同反應途徑對於催化劑性質以及催化效果的影響。在最佳化條件下進行48小時的長時間穩定性測試，發現所有的催化劑均呈現穩定且優異的催化效率，其中由水熱、微波、共沉澱法所製備的催化劑擁有較佳的催化結果。 在第二部分，我們以溶膠凝膠法合成出一系列的La2Zr2-xRuxO7 (x=0~0.4) 催化劑。在自致熱乙醇轉氫的實驗中，催化效率會隨著Ru在催化劑中的含量增加而提升。我們也比較利用函浸法和溶膠凝膠法製備金屬固溶體催化劑的催化結果，與函浸法的5% Ru/La2Zr2O7催化劑相比， La2Zr1.8Ru0.2O7固溶體的Ru含量較低，卻呈現出較高的氫氣選擇率，因此說明固溶體可以將金屬均勻分散並有助於催化活性的提升。經過長時間48小時測試，5 wt.% Ru/La2Zr2O7 和La2Zr1.8Ru0.2O7催化劑均表現穩定。

Hydrogen produced by auto-thermal steam reforming of ethanol was studied with the use of 5%Ru/Ce0.7La0.3O2-σ, 5%Ru/La2Zr2O7, and La2Zr2-xRuxO7 (x=0.1~0.4) catalysts. In the first part, different synthetic routes of sol-gel, co-precipitation, microwave and hydrothermal methods were utilized to prepare Ce0.7La0.3O2-σ nanoparticles. For the second part, a series of pyrochlore-typed materials, La2Zr2-xRuxO7 (x=0~0.4) were synthesized through sol-gel method. All samples were characterized by powder X-ray diffraction (PXRD), scanning electron microscope (SEM), inductively coupled plasma-atomic emission spectrometer (ICP-AES), BET surface area, temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The catalytic performance and stability of the 5 wt.%Ru/Ce0.7La0.3O2-σ catalysts was studied and the results indicated the better activities for the catalysts synthesized by co-precipitation, microwave, and hydrothermal methods. For the series of La2Zr2-xRuxO7 catalysts (x=0~0.4), the catalytic performances were investigated with respect to the selectivity of hydrogen. Production of hydrogen was enhanced by the incorporated Ru4+ ions. Comparing with the 5 wt.% Ru/La2Zr2O7 catalyst prepared by the conventional impregnation method, La2Zr1.8Ru0.2O7 showed a higher hydrogen selectivity with a lower Ru content. The enhanced activity was due to the well dispersion of Ru within the as-prepared solid solution. Long term stability was tested on 5 wt.% Ru/La2Zr2O7 and La2Zr1.8Ru0.2O7 catalyst, and showed a constant performance for 48hrs.