Performance of La-Ba Co-modified Alumina Prepared by Peptizing Method

Abstract

La-Ba co-modified alumina was prepared from two kinds of pseudo boehmite and HNO_3 as peptizer by peptizing method.The structure and surface property of the alumina were characterized by XRD,BET surface area analyzer,NH_3-temperature programmed desorpfion and NO_2-temperature programmed desorption technology.XRD results showed thatγ-Al_2O_3 phase existed in all the modified alumina samples after calcination at 1273 K.A little BaCO_3 was generated when content of BaO was increased to 14%(w).BET results showed that both of 5%(w) La_2O_3- modified and 5% La_2O_3-8%BaO co-modified alumina (Ba-8) samples exhibited larger specific surface area and pore volume after calcination at 1273 K.N_2 adsorption and desorption isotherms of all alumina exhibited that their surface pore structure was slit-shape and ink-shape pores,pore diameter distribution of Ba-8 was broader and centered between 5 and 10 nm,and other samples centered at 10 nm.NH_3-TPD results indicated that the larger the BaO doping concentration,the less the acidic amount was.At the same time,surface acidity of alumina apparently became weak. NO_2-TPD results showed that BaO doped alumina adsorbed more NO_2 than La_2O_3 doped,sample Ba-8 adsorbed the most NO_2.As sample Ba-8 simultaneously exhibited good textural properties,proper surface acidic amount,acidity and stronger NO_2 adsorption capacity,it had the best catalytic performance when it was used as catalyst carder.The temperatures of light-off and complete conversion of C_3H_3 were 526 K and 593 K,respectively.