摘要
The modulating effects of Cu modification and oxalate or borohydride ligands functionalization on the structure,catalyst d-band center(εd),upper d-band edge(εu),and acetylene partial hydrogenation of expediently synthesized Ce alloyed Pt supported catalysts were investigated.Firstly,a 5 wt%Pt alloyed Ce was synthesized via flame spray pyrolysis.The PtCe sample was further supported on zeolite Y,ZY,(PtCe/ZY)and copper modified ZY(PtCe/Cu-ZY).Furthermore,the PtCe was supported on two other oxalate and borohydride ligands functionalized copper modified ZY(PtCe/CuX-ZY and PtCe/CuB-ZY,respectively).The high-angle annular darkfield scanning transmission electron microscopy(HAADF/STEM)data showed a reduction in the PtO average particle size from 2.65 nm in PtCeO_(2) to average 1.73,0.64,and 0.30 nm in PtCe/Cu-ZY,PtCe/CuX-ZY,and PtCe/CuB-ZY,which was corroborated by the electron energy-loss spectroscopy(EELS)results wherein nonhomogeneous mixing of elements was seen with segregated Pt clusters in the non-functionalized samples.Conversely,both PtCe/CuX-ZY and PtCe/CuBZY samples showed near-perfect homogeneity with no distinct Pt signals.The measuredεu values for PtCe,PtCe/Cu-ZY,PtCe/CuX-ZY,and PtCe/CuB-ZY are+1.85,+0.40,-0.15,and-0.19 eV,respectively.The positive values indicated strong metal-adsorbate bonding typical of large Pt sizes while the negative values indicated weak metal-adsorbate bonding due to highly downsized Pt sizes.The ethylene yield(YC2H4)over the PtCe sample showed depletion as the reaction temperature increased,while it reflected maxima at 120℃ with 55.3%YC2H4 over PtCe/ZY.The maxima shifted to 180℃ with enhanced YC2H4 of 71.4%in PtCe/Cu-ZY.On the contrary,both PtCe/CuX-ZY and PtCe/CuB-ZY exhibited a monotonous increase in YC2H4 up to the maximum C_(2)H_(2)conversion with YC2H4 of 81.9%and 92.1%at 180 and 160℃,respectively.These results showed that both the Cu modification and ligands functionalization were highly invaluable to enhance the properties and activities of the semihydrogenation of acetylene(SHA)catalysts.
