Studies on lattice oxygen utilization during catalytic conversion of n-heptane activated by V2O5/Al2O3

• The influences brought by V2O5/Al2O3 became weaker with increasing time on stream.
• Lattice oxygen of V2O5/Al2O3 was consumed continuously with a decreasing rate.
• D-values of conversion presented a linear relationship with the rate.
• D-values of H2, C3H6, C4H8 and aromatic yield increased monotonically with the rate.

Continuous flow conversion of n-heptane over a commercial equilibrium ZSM-5 catalyst without and with introduction of V2O5/Al2O3 in absence of gas phase oxygen was tested in a fixed-bed reactor at 570 °C. Our previous study suggested an important role of surface lattice oxygen of V2O5/Al2O3 in promotion conversion of n-heptane over ZSM-5 catalyst in a pulse reaction mode. Thus, lattice oxygen utilization of the continuous reaction process was studied in this paper. By analyzing the fresh and used V2O5/Al2O3 catalysts passing through different reaction times by XPS method, we found that the surface lattice oxygen of V2O5/Al2O3 was consumed continuously with a decreasing rate during the process. Meanwhile, the influences by V2O5/Al2O3 introduction became weaker with increasing time on stream. The differences of the values of conversion without and with presence of V2O5/Al2O3 showed a linear relationship with the consumption rate of lattice oxygen. Besides, the D-values of hydrogen, aromatics, propylene and butylenes also increased monotonically with the consumption rate.