PdAu/Al_2O_3合金纳米催化剂的合成、表征及其在4-氯硝基苯加氢中的应用

Synthesis, Characterization and Catalytic Activity of Pd Au/Al_2O_3 for p-Chloronitrobenzene Hydrogenation

采用乙二醇连续还原法合成了不同摩尔比的PdAu合金纳米颗粒.利用XRD、TEM、DRIFT-IR和紫外可见光光谱表征技术对其进行了表征.结果表明,纳米Pd种子与氯金酸钠发生置换反应,表面元素重新排布,Pd、Au纳米颗粒以PdAu合金形式存在,且合金粒径大小可控.将不同摩尔比的PdAu合金纳米颗粒采用共沉淀法负载到Al_2O_3载体上,制得PdAu/Al_2O_3催化剂,并将其应用于4-氯硝基苯的加氢反应中.与Au/Al_2O_3、Pd/Al_2O_3催化剂(4-氯硝基苯转化率为0和37.4%)相比,PdAu/Al_2O_3催化剂大大提高了4-氯硝基苯加氢活性,其中PdAu-1/0.5/Al_2O_3催化剂具有最高的催化活性,4-氯硝基苯转化率为69.4%,这可能归因于PdAu合金纳米颗粒间的协同效应和PdAu与Al_2O_3载体间的强相互作用.

PdAu alloy nanoparticles with different molar ratio have been synthesized via sequential reduction method using glycol as the reductant. The results of XRD, TEM, DRIFT-IR and UV-visible spectra indicate that Au in sodium tetrachloroaurate （NaAuCI4） is partially replaced by Pd, resulting with the rearrangement of the surface atoms, thus the nanoparticles of Pd and Au are generated in the form of PdAu alloy with controllable particle size. PdAu/Al2O3 catalyst is prepared using the co-precipitation method and applied for p- chloronitrobenzene （p-CNB） hydrogenation with H2. Compared with Au/Al2O3 （the conversion of p-CNB being 0） and Pd/Al2O3 （the conversion of p-CNB being 37.4%） catalysts, the catalytic performance of PdAu/Al2O3 catalyst is significantly improved, where PdAu-1/0.5/Al2O3 exhibits the best catalytic performance with the highest conversion of p-CNB being 69.4%, which is probably attributed to the synergistic effect among PdAu nanoparticles and strong interaction between PdAu and A1203 support.