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用SCC-DV-X_α(电荷自洽离散变分X_α)方法和过渡金属成键函数方法,对碱土金属离子助催的负载型催化剂M~(++)-Pd/SiO_2催化CO加氢合成甲醇的作用机理及M~(++)-Pd-SiO_2间的作用本质进行量子化学研究.得到与我们用XPS、ESR、TPd-MS等实验~([1])测定值一致的如下结果:Pd(100)面上吸附的CO是在Pd_2上的桥式吸附,吸附的(?)呈H~(δ-);在含Cl~-催化剂M~(++)-Pd/SiO_2上,碱土金属离子或直接与Pd相互作用,或通过O、Cl桥间接与Pd相互作用影响Pd的价态,从而影响对CO的活化、(?)的吸附态和中间态的品种;载体氧参与了甲醇的生成反应.这些理论计算结果,还进一步论证了我们根据实验提出的催化作用机理,即在催化剂上吸附的CO和吸附的H~(δ-),与载体上的O反应生成中间过渡态HCOO,它再经Pd~+活化和在H~(δ-)、H~(δ+)作用下生成H_2CO,最后与H~(δ+)作用生成CH_3OH.
An alkaline earth metal ion supported supported catalyst M ~ (++) - Pd / SiO_2 was used to catalyze CO hydrogenation to synthesize methanol with SCC-DV-X_α (charge self-consistent discrete variational X_α) method and transition metal bond function method And the nature of M ~ (++) -Pd-SiO_2 were investigated by quantum chemical method and the following results were obtained in agreement with the experimental results of ~ ([1]) using XPS, ESR and TPd- The adsorption of CO on the (100) surface was bridged on Pd_2, and the adsorption (~) was H ~ (δ-). On the Cl ~ - catalyst M ~ The interaction between Pd and Pd directly interacts with Pd or indirectly with O and Cl bridge to affect the valency of Pd, which affects the activation of CO, the adsorbed and intermediate species of (?) These results also further demonstrate the catalytic mechanism we proposed experimentally, that is, the CO adsorbed on the catalyst and the adsorbed H ~ (δ-) reacts with the O on the carrier to generate the intermediate transition state HCOO, It is then activated by Pd ~ + and H_2CO is generated under the action of H ~ (δ -) and H ~ (δ +), finally it forms H_ (δ +) to form CH_3OH.