Preparation, Characterization And Dechlorination Performance Of Pd-Ni Bimetallic Catalysts

Pd-Ni bimetallic catalyst had been widely used in chemical industry,food processing,environmental protection and other fields,The popular preparation method to obtain the catalyst is impregnation,however,the products manufactured by this methodology has lots backdraws such as low dispersion degree,low utilization rate of active metal and dechlorination effect.A novel route combining chemical precipitation with ultrasonic technique was performed to prepare Pd-Ni bimetallic catalyst on different carrier in present study.The optimum conditions of deposition,calcination and reduction were studied,and the composition,physical phase and performance of the catalyst obtained were characterized by laser particle size analysis,X ray diffraction,differential thermal analysiser,transmission electron microscopy,and N2 adsorption-desorption insutrument,and also the hydrogenation dechlorination performance for shellac in liquid phase reaction was studied.Results showed the best deposition conditions of the γ-Al2O3 as the carrier for Pd-Ni bimetallic catalyst was pH 12,palladium nickel ratio 1:1,depostion time 2 h,deposition temperature 40 ℃,3%quality of dispersants,stirring speed 500 r/min,ultrasonic time 5 minutes and ultrasonic intensity by 60%(720 W),in this condition,particle size uniformLy distributed,catalyst particle size decreased to 5.07 micron from 14.07 micron,effective reduce the aggregation effect between particles;The best deposition conditions of SiO2 as the carrier for the Pd-Ni bimetallic catalyst was pH 11.5,nickel,palladium ratio 1:1,depostion temperature 35 ℃,depositon time for 1 h,4%quality of dispersants,stirring speed 500 r/min min,ultrasonic time 7 minutes and ultrasonic intensity by 20%(240 W).The best deposition conditions withγ-Al2O3-SiO2 as the carrier for Pd-Ni bimetallic catalyst was pH 11.5 nickel,palladium ratio 1:1,deposition time 1 h,deposition temperature 30 ℃,3%quality of dispersants,stirring speed 500 r/min min,ultrasonic time 7 minutes and ultrasonic intensity by 40%(480 W),The deposition time,ultrasonic time and ultrasonic intensity is more significant effects on gamma Al2O3-SiO2 catalyst in particle size and particle distribution.By thermo-differential and XRD analysis to determine the different carrier catalyst best roasting,reduction conditions:(1)the γ-Al2O3:roasting temperature is 600 ℃,roasting time 2 h,reduction temperature is 500℃,reduction time 2 h;(2)the carrier of SiO2,roasting temperature is 600 ℃ roasting time 2.5 h,reduction temperature is 500 ℃,reduction time 2 h;(3)the carrier y-Al2O3-SiO2:roasting temperature is 550 ℃,roasting time 2.5 h,reduction temperature is 500 ℃,reduction time 2 h.Three kinds of Pd-Ni bimetallic catalyst by reduction was’nt found NiO phase,phase crystallinity of the Pd was better,three kinds of catalyst’s phase peak shift to the right,consider produce Pd-Ni alloy.Hydrogenation dechlorination of shellac research showed that:in liquid-solid ratio 7:1,catalyst 8 g/L,hydrogen flow rate 0.1 L/min,the reaction temperature 90 °C,reaction time 4 h,stirring speed 300 r/min(1)under the condition of Pd-Ni/y-Al2O3 catalyst,chlorine content in shellac after dechlorination was 0.43%;(2)chlorine content in the shellac after Pd-Ni/SiO2 catalyst dechlorination was 0.48%;(3)chlorine content in the shellac after Pd-Ni/-γ-Al2O3-SiO2 catalyst dechlorination was 0.38%.we found that the Pd-Ni/y-Al2O3-SiO2 had higher effect on hydrogenation dechlorination performance.In addition,Chlorine content in the shellac after three kinds of bimetallic catalyst dechlorination were accord with standard of Europe and the United States,at the same time met the requirements of domestic food and pharmaceutical industry.