(778c) Selective Hydrogenation of 1,3-Butadiene On Pd-Ni Bimetallic Catalyst: From Model Surfaces to Supported Catalysts

The selective hydrogenation of 1,3-butadiene serves as a means to purify the butene stream generated in the cracking of naphtha or gas oil. In order to successfully polymerize butene, 1,3-butadiene must be removed below 10ppm, because even small amounts of 1,3-butadiene are sufficient to poison the polymerization catalysts.

In order to identify the selective hydrogenation catalysts, 1,3-butadiene was studied on single crystal Ni/Pd(111) bimetallic surfaces, utilizing density functional theory (DFT) modeling and temperature-programmed desorption (TPD) in ultra high vacuum system. DFT results revealed lower activation barriers on the PdNiPd(111) surface than on Pd(111). Consistent with DFT predictions, TPD results revealed that the PdNiPd(111) surface was more active for hydrogenation of 1,3-butadiene to butene than Pd(111).

Surface science results were verified in a batch reactor on supported catalysts. Both the bimetallic (0.91w.t.%Pd 1.51%w.t.Ni) and monometallic (0.91w.t.%Pd, 1.51%w.t.Ni) catalysts were prepared by incipient wetness impregnation. SiO₂, g-Al₂O₃, CeO₂ were applied as supports for the study of support effect. Extended X-Ray absorption fine structure (EXAFS) and transmission electron microscopy (TEM) confirmed the formation of uniform, bimetallic particles. The PdNi bimetallic catalysts showed higher activity than the monometallic catalysts. Among the supports studied in this work, SiO₂ supported bimetallic catalyst was found to exhibit significant enhancement in hydrogenation activity than the monometallic Pd and Ni catalysts.