Surface exposure engineering of highly active Mn-based spinel in monolithic catalysts for efficient acetone degradation.

Volatile organic compounds (VOCs) from different industrial processes cause harm to the environment and human health. Highly active and stable monolithic catalysts play a vital role in VOCs degradation in practical application. Here, the Mn-based spinel monolithic catalyst (BTMn catalyst) was prepared from bauxite and Mn(OH)2 using phase inversion method, and then further treated with NaOH solution to obtain the BTMn-OH catalyst. The temperature for 90 % of acetone conversion over BTMn-OH is 86 °C lower than that over BTMn. The CO₂ selectivity of BTMn-OH is higher by 8-28 % than that of BTMn. The reaction rate of BTMn-OH is 13 times higher than that of BTMn at 160 °C. Compared to BTMn, abundant Lewis acid sites in BTMn-OH enhance its adsorption capacity for acetone. After alkali treatment, BTMn-OH exhibits a higher surface proportion of Mn3O4/MnAl2O4 phases, accompanied by more surface adsorbed oxygen species and Mn³ ⁺, which collectively contribute to its excellent low-temperature acetone oxidation performance. BTMn-OH also exhibits excellent catalytic stability. Formic acid degradation is the rate-limiting step for BTMn-OH, accompanied by the rapid conversion of methanol. This work provides a new insight into the design of highly active and stable spinel based monolithic catalysts for efficient purification of VOCs.