Enhancement of toluene removal over α@δ-MnO2 composites prepared via one-pot by modifying the molar ratio of KMnO4 to MnSO4•H2O

The construction of composite crystal structure is an effective strategy for developing enhanced functionality and can generally be constructed via two steps. Herein, a series of alpha@delta-MnO2 catalysts with different alpha/delta phase ratios are one-pot synthesized using a hydrothermal method; their molar ratio of KMnO4 to MnSO4 center dot H2O was accurately controlled from 2.9 to 3.7. The catalytic results show that all alpha@delta-MnO2 catalysts exhibit significantly better catalytic performance in oxidizing toluene than single alpha-MnO2 and delta-MnO2 due to a synergistic effect, in which alpha@delta-2 with the closest two-phase proportion has the highest activity (T-90 = 238 degrees C under a WHSV of 60,000 mL.g(-1).h(-1)). Various characterization results indicate that alpha@delta-2 has the largest specific surface area, highest defects, oxygen vacancies, and best low-temperature reducibility among alpha-MnO2, delta-MnO2, and alpha@delta-2. Also, the possible reaction pathway for oxidizing toluene over the prepared catalysts is speculated using both TD/GC-MS and in-situ DRIFTS experiments.

Automated summary

The study successfully synthesized a series of alpha@delta-MnO2 catalysts with different alpha/delta phase ratios using a hydrothermal method, accurately controlling the molar ratio of KMnO4 to MnSO4•H2O. It was found that the catalysts exhibited significantly better catalytic performance compared to single-phase MnO2.