Preparation Of Supported Nano Bimetallic Catalyst Through Hydrotalcite-like In Situ-growth On Support

In recent years,bimetallic catalysts have drawn great attention due to their superior catalytic performance.However,preparation of supported nano bimetallic catalyst is still a problem witch hindered its application in industry.This paper provided a strategy to prepare highly dispersed supported nano bimetallic catalysts with homogeneous components.In hydrotalcite-like structure,metal cations can achieve molecular level dispersion in the hydroxide layers.In this study,LDHs with two metal ions in situ grew on the ?-Al₂O₃ support.The precursor was in situ grown on the surfance of ?-Al₂O₃ support by sharing the sole Al source.It makes the LDHs loaded on the ?-Al₂O₃ support uniformaly.After appropriate calcination and reduction,well dispersed nano bimetallic particles loaded on ?-Al₂O₃ support can be obtained.Firstly,MgNiCo/Al-LDH successfully in situ grew on monolithic macroporous ?-Al₂O₃ by hydrothermal process.After calcined and reduced at 750 °C,supported Ni-Co alloy catalysts were obtained.Small Ni-Co alloy nanoparticles were highly dispersed on the MgAlOx nanosheets and MgAlOx nanosheets were uniformly fixed on monolithic macroporous ?-Al₂O₃.The resultant catalysts exhibited excellent catalytic performance for ethanol steam reforming.The conversion of ethanol can achieve to 100% at temperature of 400 °C,WHSV=80,000 m L gcat^-1 h^-1 with reaction mixture of H2O/C2H5OH=3 in mole ratio.The selectivity of H2 can reach 65%.The stability was tested at 650 °C and a high space velocity of 240,000 ml gcat^-1 h^-1 for 30 h.The activity didn't go down after 30 h.Then MgCuCo/Al-LDH also successfully in situ grew on monolithic macroporous ?-Al₂O₃ by hydrothermal process.After directly reduced at 500 °C under 5 vol% H2/Ar,supported Cu-Co alloy catalysts were highly dispersed on monolithic macroporous ?-Al₂O₃.The resultant catalysts exhibited excellent catalytic performance for higher alcohol synthesis from syn gas.The conversion of CO can achieve to 54% and the selectivity of C2+OH in total alcohols can get up to 68.4% at temperature of 280 °C,WHSV=3,900 m L gcat^-1 h^-1 under pressure of 4 MPa.Finally,CuCo/Al-LDH successfully in situ grew on commercial ?-Al₂O₃ by hydrothermal process.CuCo bimetallic nanoparticles were highly dispersed on ?-Al₂O₃ after reduction.With different reduction temperature,the structure of CuCo bimetal was also different.Cu-Co alloy can obtained after the precursors were reduced at 500 °C by H2 while hollow structured Cu-Co alloy and Co@Cu nanoparticles formed after the precursors were reduced at 600 °C and 700 °C.It may be due to Co diffusion or the segregation of copper and cobalt at high temperature.Cu-Co alloy exhibited excellent catalytic performance for higher alcohol synthesis from syn gas,while hollow structured Cu-Co alloy and Co@Cu nanoparticles had bad catalytic performance.This demonstrates that the synergism between Cu an Co plays a key role in the formation of C2+OH.