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

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-67 and PdCu/ZIF-67 catalysts were characterized using XRD, N2 adsorption-desorption analysis, TEM, EDS, XPS and ICP-AES. 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 Pd 3d levels and Cu 2p levels reveal that Pd and Cu particles on the surface of the ZIF-67 support are in a +2 valence state. TEM and EDS displayed 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 at 50℃, respectively. For the PdCu/ZIF-67 (1∶1) catalyst, the 1,3-butadiene conversion and butene selectivity are 93.2% 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 for 50 h at 130℃. The results provide a reference for the design of new high efficiency 1,3-butadiene hydrogenation catalyst.