Abstract
Pd nanoparticles (PdNPs) stabilized by methyl cellulose (MC) were synthesized in an aqueous solution, which are monodispersed nanoparticles. PdNPs/α-Al2O3 catalyst was prepared with monodispersed PdNPs and showed better catalytic performance than Pd/α-Al2O3 catalyst prepared by the incipient wetness impregnation method using Pd(NO3)2 as a precursor. The catalysts were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS). It was found that monodispersed PdNPs were spherical or elliptical nanoparticles with exposed (111) and (100) facets, and the PdNPs/α-Al2O3 catalyst showed a more concentrated distribution of Pd particles on the surface of α-Al2O3 support than the Pd/α-Al2O3 catalyst. The preparation method achieved the highly dispersed PdNPs/α-Al2O3 catalyst with smaller Pd particle size and decreased the aggregation of Pd active sites, which was responsible for higher acetylene conversion and ethylene selectivity.
Highlights
Ethylene is an important chemical for polymerization to polyethylene
The transmission electron microscopy (TEM) image shown in Figure 1a indicates that the Pd nanoparticles (PdNPs) stabilized by methyl cellulose (MC) are monodispersed spherical or elliptical nanoparticles
Monodispersed PdNPs stabilized by MC were successfully synthesized in an aqueous solution
Summary
Ethylene-rich feed stream contains trace amount of acetylene (0.5–2% by volume) for the tail-end hydrogenation reactor. The small trace of acetylene as impurity has to be reduced to less than 5 ppm [1,2,3]. For the selective hydrogenation of acetylene, supported Pd catalysts are used for the catalytic removal process. Supported Pd catalysts with low Pd loading still have attracted much attention in recent years [4,5,6,7,8,9,10]. The recent advance on supported Pd catalysts is to increase their ethylene selectivity and enhance their long-term stability. For improving the performance of supported Pd catalysts, bimetallic Pd catalysts have been investigated extensively with the addition of a second metal as a promoter to dilute Pd ensemble size [11,12,13,14,15,16,17,18,19,20,21,22]
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