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本文应用SCC-DV-X_α(电荷自洽离散变分X_α)方法,对合成甲醇的铜、锌氧化物催化剂上CO及H_2的活化本质进行量子化学计算。通过对CO在催化剂CuO～ZnO的活性中心模型上可能的吸附方式的计算,得到CO是以端基顶位吸附在原子簇CuO-ZnO的Cu(Ⅰ)上。从吸附态CO上的5σ与2π轨道占有的电子数,轨道组成和原子间轨道重迭集居数的计算结果表明:CO被吸附后由σ轨道给予活性中心原子簇上Cu的电子为0.30e,而铜反馈到CO2X上的电子戈0.23e,这种σπ络合,活化了CO分子。对催化剂组分ZnO的(1010)表面原子簇模型Zn_8O_8进行电子结构性质的计算表明,Zn_8O_8原子簇的态密度同UPS的结果一致。它的前线轨道LUMO主要由表面的Zn4s和Zn4p形成的sp~3杂化轨道组成,HOMO主要由O2p轨道组成。它们分别同H相互作用,从而活化H,并使其异裂成Zn~(2+)+H~-和O~(2-)-H~+。
In this paper, SCC-DV-X_α (charge self-consistent discrete variational X_α) method was used to conduct the quantum chemistry calculations on the activation properties of CO and H_2 on the copper and zinc oxide catalysts for the synthesis of methanol. Through calculation of the possible adsorption mode of CO on the active center model of CuO ~ ZnO catalyst, CO is adsorbed on the Cu (Ⅰ) cluster of CuO-ZnO clusters by the terminal top group. The calculations of the numbers of electrons, orbital compositions and the number of orbital overlap occupied by 5σ and 2π orbitals on the adsorbed CO show that the electron donated by σ orbital to Cu on the active center cluster is 0.30e , While copper is fed back to the electron lattice on CO2X, 0.23e. This sigma-π complex activates the CO molecule. Calculations of the electronic structure properties of (1010) surface atomic cluster model Zn_8O_8 of ZnO as a catalyst component show that the state density of Zn_8O_8 cluster is consistent with that of UPS. Its frontier orbital LUMO consists mainly of sp ~ 3 hybrid orbital formed by Zn4s and Zn4p on the surface, and HOMO consists mainly of O2p orbitals. They interact with H, respectively, to activate H and make it heterolytic to Zn ~ (2 +) + H ~ - and O ~ (2 -) - H ~ +.