以理論計算方法探討乙醇和甲醇在nNi/gamma-Al2O3(110)(n=1,2)表面的脫氫反應

Abstract

我們利用periodic DFT的方法，計算乙醇和甲醇在1-2Ni/gamma-Al2O3(110)表面的吸附結構和分解路徑。在我們的研究當中，乙醇和甲醇利用OH基吸附在表面的鋁原子上有較好的吸附能，計算的結果分別為-1.61eV和-1.41eV。 在乙醇反應的探討當中，乙醇會在表面上形成四圓環或五圓環的結構，其中，四圓環的中間產物最後經過1.60 eV的能障後會斷C-C鍵形成CH3 + CO，而五圓環的中間產物會斷C-O鍵形成乙烯，所需要克服的能障為1.27 eV。甲醇可能經過脫氫反應形成一氧化碳，所需要克服的最大能障為1.27eV，而甲醇斷C-O鍵形成CH3 + OH所需要克服的能障為1.51eV。乙醇在我們模擬的情況當中有較佳的吸附能，且甲醇在整個反應當中所需要克服的能障在比較上相對比乙醇大。We applied periodic density-functional theory (DFT) to investigate the dehydrogenation reactions of ethanol and methanol on 1-2Ni/gamma-Al2O3 (110) surfaces. In our studies, ethanol and methanol favor the adsorption orientation by using the OH group bonding to the Al atom on the surface; the adsorption energies were calculated to be -1.61 eV and -1.41 eV respectively. In our calculation, ethanol may form a four or five-membered ring structure on the surface. The four-membered ring intermediate could break the C-C bond to form CH3(a) + CO(a) with a dissociation barrier of 1.60 eV. And that of the five-membered ring would break the C-O bond to form ethylene with the barrier of 1.27 eV. Methanol may proceed dehydrogenation to produce carbon monoxide with a barrier of 1.27 eV, or to break the C-O bond to form CH3(a) + CO(a) with a barrier of 1.51 eV. In our calculation, we found out that ethanol had a larger adsorption energy, but methanol had higher barriers as compare to ethanol in the processes of dehydrogenation mechanisms.