Lindlar's catalyst, i. e., calcium carbonate‐supported palladium (Pd) modified with lead, has been used for semihydrogenation of an alkynyl group in the presence of hydrogen gas (H₂). We examined hydrogenation of an alkynyl group in organosilane and hydrocarbon in methanolic suspensions of a Pd‐loaded titanium(IV) oxide (Pd−TiO₂) photocatalyst without the use of additives and H₂. In the photocatalytic reaction, Pd particles worked as co‐catalysts for hydrogenation and alkyne hydrogenation had priority to alkene hydrogenation. Since the Pd co‐catalyst was temporarily deactivated during the reaction owing to accumulation of the oxidized product(s) of methanol, the capacity of hydrogenation of the unsaturated C−C bond was limited. By optimizing the capacity and amount of alkynes, almost complete semihydrogenation of alkynes was achieved under a poison‐free condition. Pd−TiO₂ can be regenerated by very simple treatments, i. e., washing and drying at room temperature.

中文翻译：

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Pd-TiO2光催化剂上利用临时原位失活将炔基进行无加成的半氢化为烯基

Lindlar的催化剂i。例如，用铅改性的碳酸钙负载钯（Pd）已用于在氢气（H ₂）存在下对炔基进行半氢化反应。我们研究了在不使用添加剂和H _2的情况下，负载钯的二氧化钛（Pd-TiO ₂）光催化剂的甲醇悬浮液中有机硅烷中的炔基和烃中的烃的氢化作用。在光催化反应中，Pd颗粒作为助催化剂进行加氢，炔烃加氢优先于烯烃加氢。由于甲醇中氧化产物的积累，Pd助催化剂在反应过程中暂时失活，因此不饱和C-C键的氢化能力受到限制。通过优化炔烃的容量和数量，可以在无毒条件下实现炔烃的几乎完全半氢化。Pd-TiO ₂可以通过非常简单的处理即再生。例如，在室温下洗涤和干燥。