CAJ | 학술논문

采用广义梯度近似(GGA)的密度泛函理论(DFT)(DFT-GGA)对Co-Pd催化剂上CH_4/CO_2两步法合成乙酸反应中CO_2与金属表面物种M-H(M=Co, Pd)和Pd-CH_3的插入反应机理进行了研究, 给出了CO_2与M-H和Pd-CH_3的插入反应机理. 计算结果表明, 在CO_2与M-H和Pd-CH_3相互作用的4个反应路径中, 反应以CO_2与Co-H 作用生成产物HCOO-Co为动力学优先路径, 但由于HCOO以双齿形式与金属Co结合, 其结合能较大, 导致HCOO在金属表面不易脱附, 故较难形成甲酸;反应生成H_3CCOO-Pd产物路径次之, H_3CCOO和Pd之间结合能较小, H_3CCOO容易脱附形成主产物乙酸;生成H_3COOC-Pd反应为动力学最不利路径, 故甲酸甲酯为动力学禁阻产物;计算结果与实验结果吻合得很好.
채용엄의제도근사(GGA)적밀도범함이론(DFT)(DFT-GGA)대Co-Pd최화제상CH_4/CO_2량보법합성을산반응중CO_2여금속표면물충M-H(M=Co, Pd)화Pd-CH_3적삽입반응궤리진행료연구, 급출료CO_2여M-H화Pd-CH_3적삽입반응궤리. 계산결과표명, 재CO_2여M-H화Pd-CH_3상호작용적4개반응로경중, 반응이CO_2여Co-H 작용생성산물HCOO-Co위동역학우선로경, 단유우HCOO이쌍치형식여금속Co결합, 기결합능교대, 도치HCOO재금속표면불역탈부, 고교난형성갑산;반응생성H_3CCOO-Pd산물로경차지, H_3CCOO화Pd지간결합능교소, H_3CCOO용역탈부형성주산물을산;생성H_3COOC-Pd반응위동역학최불리로경, 고갑산갑지위동역학금조산물;계산결과여실험결과문합득흔호.
The insertion reactions of CO_2 with M-H (M=Co, Pd) and Pd-CH_3 were systematically investigated by the first-principle DFT-GGA calculations. The mechanisms of CO_2 reacting with M-H and Pd-CH_3 were obtained for the direct synthesis of acetic acid from CH_4/CO_2 by a two-step reaction sequence on Co-Pd catalysts. The calculation result showed that the pathway that CO_2 inserts into Co-H bonds forming HCOO-Co was the most advantageous in dynamics for all four designed reaction paths. However, HCOO was linked with Co in bi-dentate form, whose binding energy was very large, so the desorption of HCOO hardly taken place and formic acid was little produced. Meanwhile, the pathway that CO_2 inserts into Pd-CH_3 bonds forming H_3CCOO-Pd was secondly preferential pathway favored in dynamics. The binding energy between H_3CCOO and Pd was small, and desorption of H_3CCOO easily occurred, so the main product was acetic acid. While methyl formate was inhibited by dynamics. The calculated result was in accordance with the experimental facts.