Comparative Study on the Reaction Pathways of 2-Chloropropanoic Acid on Cu(100) and O/Cu(100)

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• 作者：Zi-Xian Yang ; Shang-Wei Chen ; Szu-Han Lee ; Tai-You Chen ; Jong-Liang Lin
• 刊名：Journal of Physical Chemistry C
• 出版年：2017
• 出版时间：January 12, 2017
• 年：2017
• 卷：121
• 期：1
• 页码：315-323
• 全文大小：544K
• ISSN：1932-7455

文摘

CH₃CHCOOH and CH₃CHCOO have been theoretically predicted to be important in the decarboxylation or decarbonylation of propanoic acid on Pd(111). In the present study, we explore the possibility to prepare these two intermediates on Cu(100) and oxygen-predosed Cu(100) (O/Cu(100)), with CH₃CHClCOOH as the precursor, and to investigate their adsorption geometries and reactions on the surfaces using X-ray photoelectron spectroscopy, reflection–absorption infrared spectroscopy, temperature-programmed reaction/desorption, and calculations of density functional theory. CH₃CHClCOO and CH₃CHCOO are suggested to be formed on Cu(100) at 250 K by heating the CH₃CHClCOOH adsorption layers. However, CH₃CHCOO can promptly recombine with the H from the deprotonation of CH₃CHClCOOH to generate CH₃CH₂COO. The adsorbed propanoate decomposes mainly into H₂, CO, and CO₂ at a temperature higher than ∼380 K. On O/Cu(100), CH₃CHClCOO is the predominant species found in the dissociation of CH₃CHClCOOH at 250 K. The preadsorbed O disables the CH₃CHCOO hydrogenation to form CH₃CH₂COO due to the lack of adsorbed H. This intermediate is not stable above ∼400 K and decomposes into H₂, H₂O, CO, and CO₂, probably with a small amount of acrolein or methylketene. The CH₃CHCOO is shown theoretically to be bonded on Cu(100) via the unsaturated carbon and one of the oxygen atoms.