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采用红外光谱、紫外漫反射光谱和程序升温分解技术研究了担载于ZrO_2和Zr(OH)_4上的Co_2(CO)_6(PBu_3)_2络合物在真空和空气中的脱羰基作用、结构变化过程及由此制得的分散型Co催化剂上Co的吸附态。结果表明,该络合物经担载后其羰基主频带均随载体的灼烧温度的增高而向低波数位移。表征Co—Co键电子跃迁和Co→CO电荷转移性质的紫外光谱特征带变化不大。担载络合物于真空加热时,随升温而逐渐脱去羰基,同时部分端羰基转变为桥羰基,完全脱羰基后可变为具有吸附CO能力的分散型Co金属催化剂。吸附的CO以线式存在。当样品暴露于空气时,CO吸附中心被破坏而不再出现吸附的CO振动频带。根据实验结果提出了在ZrO_2和Zr(OH)_4上的络合物的结构模型,并讨论了它们的分解机理,以及CO吸附在脱羰基后的分散型Co催化剂上的红外光谱。
The decarbonylation of Co_2 (CO) _6 (PBu_3) _2 complex supported on ZrO_2 and Zr (OH) _4 in vacuum and air was studied by infrared spectroscopy, ultraviolet diffuse reflectance spectroscopy and temperature programmed decomposition. The changing process and the adsorbed state of Co on the dispersed Co catalyst prepared in this way. The results showed that the carbonyl of the complex was shifted to the low wavenumber with the increase of the burning temperature of the carrier. The characteristic bands of UV spectrum characterizing the electronic transition of Co-Co bond and the charge transfer property of Co → CO have little change. When the supported complex is heated under vacuum, the carbonyl group is gradually removed as the temperature is raised, and at the same time, some carbonyl groups are converted into bridge carbonyls, and after completely decarbonylation, they become dispersed Co metal catalysts with CO sorption capacity. Adsorbed CO exists in a line. When the sample is exposed to air, the CO adsorption center is destroyed and the adsorbed CO vibrational band no longer appears. Based on the experimental results, the structural models of ZrO_2 and Zr (OH) _4 complexes were proposed. Their decomposition mechanism and the IR spectra of CO adsorbed on decarbonylation dispersed Co catalysts were discussed.