ZIF-67负载Pd/Pd–Cu复合纳米催化剂的制备及其加氢催化性能

ZIF-67 supported Pd nanoparticles and Pd–Cu nanoparticles for selective hydrogenation of 1,3-butadiene

1,3-丁二烯选择性加氢是石油化工中有效脱除1,3-丁二烯的方法。选用金属有机骨架ZIF-67作为载体,通过浸渍和H2还原法控制合成了Pd/ZIF-67和PdCu/ZIF-67复合纳米催化剂。采用XRD、氮气低温物理吸附、TEM、EDS、XPS等方法对Pd/ZIF-67和PdCu/ZIF-67进行了系统的物理化学性质表征,并在石英微型固定床上探索了其在1,3-丁二烯加氢反应中的催化活性、选择性和稳定性。结果表明,Pd/ZIF-67和PdCu/ZIF-67(1∶1)中Pd和Cu分别以Pd2+和Cu^(2+)存在,Pd纳米粒子和Pd–Cu纳米粒子高度分散在ZIF-67上。由于金属Pd–Cu和载体ZIF-67之间的相互作用以及Pd和Cu双金属间的几何效应,PdCu/ZIF-67(1∶1)的催化活性低于Pd/ZIF-67。Pd/ZIF-67在50℃催化1,3-丁二烯加氢时,1,3-丁二烯的转化率和总丁烯的选择性分别为99.9%和79.6%。PdCu/ZIF-67(1∶1)在130℃催化反应7 h后1,3-丁二烯的转化率和总丁烯的选择性分别为93.2%和64.3%。提高Cu的含量,PdCu/ZIF-67对于1,3-丁二烯的转化率降低,而对总丁烯的选择性提高。PdCu/ZIF-67(1∶1)比Pd/ZIF-67具有更高的稳定性,可以连续运行50 h,催化活性和丁烯选择性几乎保持不变。研究结果为新型高效加氢催化剂的设计制备提供了启示和参考。

Selective hydrogenation of 1,3-butadiene is an effective strategy to remove 1,3-butadiene in the petrochemical industry.ZIF-67 supported monometallic Pd(Pd/ZIF-67)and bimetallic Pd–Cu catalysts(PdCu/ZIF-67)with different Pd:Cu molar ratios(1∶3–3∶1)were synthesized by impregnation and hydrogen reduction.The prepared Pd/ZIF-67and PdCu/ZIF-67 catalysts were characterized using XRD,N_(2) adsorption-desorption analysis,TEM,EDS,XPS and ICPAES.The catalytic performance of supported Pd/ZIF-67 and PdCu/ZIF-67 catalysts were studied in the selective hydrogenation of 1,3-butadiene on the fixed-bed flow quartz reactor under atmospheric pressure.The XPS studies at Pd3d levels and Cu2p levels reveal that Pd and Cu particles on the surface of the ZIF-67 support are in a+2 valence state.TEM and EDS display that Pd nanoparticles and Pd–Cu nanoparticles are uniformly dispersed on ZIF-67.The experiment results show that the catalytic activity of PdCu/ZIF-67(1∶1)is lower than that of Pd/ZIF-67 due to strong interaction between Pd–Cu and ZIF-67 support and the geometric effects,i.e.,dilution of blocking of a fraction of the palladium surface by copper.The 1,3-butadiene conversion and butene selectivity reach 99.9%and 79.6%for Pd/ZIF-67 at50℃,respectively.For the PdCu/ZIF-67(1∶1)catalyst,the 1,3-butadiene conversion and butene selectivity are93.2% and 64.3%at 130℃ within 7 h,respectively.The hydrogenation activity of PdCu/ZIF-67 catalyst decrease with increasing of Cu content,while the butene selectivity increase.PdCu/ZIF-67(1∶1)show higher stability than Pd/ZIF-67,the conversion of 1,3-butadiene and butene selectivity almost remain the same after continuous run for50 h at 130℃.The results provide a reference for the design of new high efficiency 1,3-butadiene hydrogenation catalyst.