NaY zeolites modified by La3+ and Ba2+: the effect of synthesis details on surface structure and catalytic performance for lactic acid to acrylic acid

Modified NaY zeolites have been widely studied and the modification metal element is normally single, while few researches have been conducted on NaY zeolites modified by two kinds of metals. In our study, a series of La3+ and Ba2+ modified NaY zeolites were synthesized through different impregnation procedures. Lactic acid dehydration to acrylic acid was selected as a probe reaction to test the catalytic performance of these zeolites synthesized. The effects of synthesis details on their pore structures and surface acid/base properties were investigated by means of techniques such as N2 sorption, NH3-TPD and CO2-TPD. The characterization results demonstrated that the samples synthesized by two-step impregnation had more medium acid and base sites inducing better catalytic performance. Moreover, compared with successive impregnations, calcination between two impregnations could endow the samples with much more acid amount. These special surface properties resulted in the improvement of selectivity to acrylic acid during lactic acid dehydration.