TiO2催化正丁醛自缩合反应机理

TiO2-Catalyzed n-Butyraldehyde Self-Condensation Reaction Mechanism

为明晰锐钛矿TiO2催化正丁醛自缩合反应机理,采用原位反应红外分析和探针分子中毒催化剂酸碱活性位相结合的方法对酸碱活性位的作用进行了研究.气态正丁醛在TiO2表面的吸附及物种变化结果表明,正丁醛分别通过Ti-OH和Ti4+两种活性位吸附在TiO2表面,进而发生羟醛缩合反应.分别采用NH3和CO2作为探针分子中毒TiO2的酸碱活性位,并评价中毒后催化剂对正丁醛自缩合反应的催化效果,发现TiO2的酸性位起主要催化作用,而碱性位会促进副反应发生.在此基础上,提出了锐钛矿TiO2催化正丁醛自缩合的反应机理.

To clarify the reaction mechanism of n-butyraldehyde self-condensation catalyzed by anatase TiO2,the catalysis of acidic sites and basic sites was investigated by the combination of in situ Fourier transform-infrared spectroscopy(FT-IR)analysis and poisoning acidic or basic sites on TiO2 surface by a probe molecule.The adsorption behavior of gaseous n-butyraldehyde molecule and the variation of reaction species on TiO2 surface indicated that two n-butyraldehyde molecules were adsorbed separately on Ti4+and Ti-OH active sites and then reacted to 2-ethyl-2-hexenal.NH3 and CO2 were respectively used as the probe molecule to poison the acidic and basic sites on TiO2 surface and the catalytic performance of the poisoned catalyst for n-butyraldehyde self-condensation was evaluated to clarify the role of the acidic and basic sites.The results showed that the acidic sites played a major catalytic role while the basic sites promoted side-reactions.On this basis,the reaction mechanism of n-butyraldehyde self-condensation catalyzed by anatase TiO2 was established.