丝光沸石纳米片负载Pd催化剂实现2-苯基吡啶的双酰基化

Mordenite zeolite nanosheets supported palladium catalyst for diacylation of 2-phenylpyridine

以自制的含季铵基团的阳离子聚合物(COPQA)为模板剂,合成了大比表面积、具有花状形貌的丝光沸石纳米片(NS-MOR),以NS-MOR为载体,采用离子交换方法制备了负载Pd催化剂(Pd/NS-MOR)。对NS-MOR及Pd/NS-MOR进行了XRD、N2吸附-脱附、SEM、TEM及XPS测试。以2-苯基吡啶和苯甲醛为反应原料,评价了Pd/NS-MOR的催化性能。结果表明,在Pd/NS-MOR催化剂中,小粒径的Pd^(0)和Pd^(2+)物种高度分散在NS-MOR表面,而在γ-Al_(2)O_(3)负载的Pd催化剂(Pd/γ-Al_(2)O_(3))中仅有Pd^(2+)物种。Pd/NS-MOR实现了2-苯基吡啶的C2—H和C6—H键的同时活化,其催化活性和双酰基化产物选择性(92%)远高于Pd/γ-Al_(2)O_(3)。而以Pd(NO_(3))_(2)、Pd(OAc)_(2)、Pd(Ph CN)_(2)Cl_(2)为催化剂的2-苯基吡啶C—H键活化反应中均几乎无法得到双酰基化产物。此外,Pd/NS-MOR不仅具有良好的底物兼容性,而且循环使用5次后仍保持较高的2-苯基吡啶的转化率(95%)和双酰基化产物的选择性(85%)。

Mordenite nanosheets(NS-MOR)with large specific surface area and flower-like morphology were synthesized from self-made cationic copolymer containing quaternary ammonium groups(COPQA),and then loaded with Pd to prepare catalyst Pd/NS-MOR via ion-exchange method.NS-MOR and Pd/NS-MOR obtained were characterized by XRD,N2 adsorption-desorption,SEM,TEM and XPS,and the catalytic performance of Pd/NS-MOR was evaluated in the reaction of 2-phenylpyridine and benzaldehyde.The results showed that Pd^(0)and Pd^(2+)species with small particle size were highly dispersed on the surface of NS-MOR in the Pd/NS-MOR,while only Pd^(2+)species were found inγ-Al_(2)O_(3)supported Pd catalyst(Pd/γ-Al_(2)O_(3)).Pd/NS-MOR achieved the simultaneous activation of C2—H and C6—H bonds of 2-phenylpyridine,and showed much higher catalytic activity and selectivity of diacylated product(92%)than Pd/γ-Al_(2)O_(3)in the C—H bond activation of 2-phenylpyridine,while no diacylated product could be obtained when Pd(NO_(3))_(2),Pd(OAc)_(2)and Pd(PhCN)_(2)Cl_(2)were used as catalyst.In addition,besides substrate compatibility,Pd/NS-MOR also exhibited good 2-phenylpyridine conversion(95%)and diacylated product selectivity(85%)after being recycled 5 times.