Preparation Of Lanthanum-Nickel Oxide And Its Catalytic Performance To Decomposition Of Hydrogen Peroxide

Lanthanum-nickel composite oxides are widely used as catalysts.It is rarely reported that lanthanum-nickel composite oxides are used as the catalysts for the decomposition reaction of hydrogen peroxide.In this paper,lanthanum oxide and lanthanum-nickel composite oxides LaNiO3 and La2NiO4 were prepared by precipitation method,using lanthanum chloride and/or nickel chloride as raw materials,and oxalic acid and/or sodium carbonate as precipitants.The catalytic performance,catalytic reaction kinetics and catalyst structure before and after the decomposition reaction of hydrogen peroxide were studied.The main contents and results are as follows:1.Lanthanum oxide and lanthanum-nickel complex oxides LaNiO3 and La2NiO4 were prepared by precipitation method.Lanthanum oxide was prepared using lanthanum chloride as the raw material and oxalic acid as the precipitant,under the precipitation conditions of 40? and 1h,and the calcination conditions of 700? and 2h.The particle size distribution of lanthanum oxide was affected by the precipitation temperature,the pH of the solution and the adding method of the feed solutions.With the increase of precipitation temperature,decrease of pH of solution,the particle size of lanthanum oxide increased gradually.The lanthanum oxide prepared at the precipitation reaction temperature of 40? was columnar,and changed from columnar to lamellar as the reaction temperature increased.LaNiO3 was prepared using lanthanum chloride and nickel chloride as raw materials with the ratio of nLa to nNi of 1:1,and sodium carbonate as the precipitant,after reacted at 30? for 1h and calcined at 700? for 2h.When adjusting the ratio of nLa:nNi to 2:1,La2NiO4 was prepared using oxalic acid as the precipitant after the raw materials and the precipitant were stirred at 80? for 1h and the precipitation precursor was calcined at 1000? for 2h,or using sodium carbonate as the precipitant after the raw materials and the precipitant were stirred at 30? for 1h and precipitation precursor was calcined at 800? for 2h.La2NiO4 with the irregular rod structure was obtained by using oxalic acid as the precipitant,while La2NiO4 with the irregular block structure and LaNiO3 with the irregular spherical granular structure were obtained by using sodium carbonate as the precipitant.There were La3+and Ni2+ions at the surface of LaNiO3 and La2NiO4.Ni3+ion might coexist at the surface of LaNiO3 and La2NiO4.The precursor during preparation of lanthanum oxide was La2(C2O4)3·10H2O,which gradually lost its crystal water and formed the intermediate product La2O2CO3 and decomposed finally to La2O3.The precursors of lanthanum-nickel complex oxide were lanthanum-nickel oxalates and lanthanum-nickel carbonates containing crystalline water when using oxalic acid and sodium carbonate as precipitants,respectively.La2O2CO3,La2O3 and NiO were generated,and finally LaNiO3 or La2NiO4 was generated during the calcination.The thermal stability of LaNiO3 was weaker compared to La2NiO4.LaNiO3 was decomposed into a mixture of La2NiO4 and NiO when calcined at the temperature higher than 1000 0C.2.The catalytic performance of lanthanum oxide and lanthanum-nickel complex oxides LaNiO3 and La2NiO4 to the decomposition of hydrogen peroxide was studied.LaNiO3 and La2NiO4 had obvious catalytic effects on the decomposition of hydrogen peroxide.The catalytic performance of LaNiO3 was higher than that of La2NiO4.La2O3,NiO and Ni2O3 had no catalytic effect on the decomposition of hydrogen peroxide.Temperature and reaction time are important factors affecting the catalytic decomposition of hydrogen peroxide.Higher temperature and longer reaction time can improve the catalytic decomposition rate of hydrogen peroxide.The decomposition percentage of hydrogen peroxide was close to 100%at 35 0C and the reaction time of 40min when using LaNiO3 as the catalyst.The precipitation time,the precipitation temperature and the calcination temperature during preparation of LaNiO3 had a great influence on the surface morphology of LaNiO3,which influenced the catalytic performance of LaNiO3.The larger the specific surface area of LaNiO3,the better its catalytic performance.The catalytic performance of LaNiO3 was better,which was prepared at the precipitation temperature of 30? for 1h and calcination temperature of 700? for 2 h,using sodium carbonate as the precipitant.During the decomposition of hydrogen peroxide,LaNiO3 and La2NiO4 did not change to other substances.However,the tiny particles of LaNiO3 and La2NiO4 increased after the decomposition of hydrogen peroxide.3.The kinetics of decomposition of hydrogen peroxide catalyzed by LaNiO3 and La2NiO4 was studied.The reaction order of LaNiO3 and La2NiO4 catalytic decomposition of hydrogen peroxide was fitted,using MATLAB software.The results show that the reaction order of LaNiO3 and La2NiO4 catalytic decomposition of hydrogen peroxide is close to 0.54.LaNiO3 and La2NiO4 had similar catalytic effects on the decomposition reaction of hydrogen peroxide,and the catalytic reaction kinetic equation was r=kC0.54H2O2.The activation energy of LaNiO3 and La2NiO4 for the decomposition of hydrogen peroxide was 31.96kJ/mol and 48.54kJ/mol,respectively.Both La2NiO4 and LaNiO3 could reduce the activation energy of decomposition reaction of hydrogen peroxide.The catalytic ability of LaNiO3 for the decomposition reaction of hydrogen peroxide is stronger than that of La2NiO4.Therefore,LaNiO3 is an ideal catalyst for the decomposition of hydrogen peroxide.