Effect of La calcination temperature on catalytic performance of PtSnNaLa/ZSM-5 catalyst for propane dehydrogenation

Abstract

The effect of La calcination temperature on catalytic performance of PtSnNaLa/ZSM-5 catalyst for propane dehydrogenation was studied. XRD, 27Al MAS NMR, NH3-TPD, TEM, H2-TPR and hydrogen chemisorption were used to characterize the catalysts. In contrast to the catalyst without the calcination of La, the treatments in the range of 500–650°C resulted in the strong interaction between La species and the support, thus suppressing the dealumination of the support to some extent. Furthermore, in these cases the interactions between Sn species and the support as well as Pt and Sn oxides became strengthened, which were advantageous to the reaction. In our experiments, the catalyst when the calcination temperature of La was 650°C showed the best reaction activity and stability. The average yield of propene was about 34.3% over 82h for the reaction of propane dehydrogenation at 590°C. However, after the thermal treatment of La at 700°C, sharply decreased of the catalyst acidity was inevitable due to the severe dealumination. Meanwhile, sintering of Pt particles and the formation of Sn0 species were also found, which seriously resulted in the deactivation of catalyst. Finally, a model for the effect of La calcined treatment was also proposed.