Boosting the Catalytic Performance of γ-MnOOH Through Post-Treatment with Potassium Hydroxide on n-Butylamine with CO₂

In this study, a simple potassium hydroxide (KOH) post-treatment was applied to increase the catalytic performance of γ-MnOOH in the carbonylation of n-BuNH₂ with CO₂ by the hydrothermal method. The catalytic activity of γ-MnOOH was significantly boosted and the degree of enhancement is directly related to the add amount of KOH, i.e. K(6.7)-γ-MnOOH > K(6.9)-γ-MnOOH > K(6.0)-γ-MnOOH > γ-MnOOH, in which the catalytic activity of K(6.7)-γ-MnOOH with n(KOH):n(γ-MnOOH) = 6.7 showed the greatest lift with the conversion of n-BuNH₂ and the N,N′-dibutylurea yield from 48.81% and 47.85% for pristine γ-MnOOH up to 75.26% and 74.53% for K(6.7)-γ-MnOOH under 5.0 MPa at 160 °C for 4 h, respectively. XRD, SEM, FT-IR, BET, ESR, TG-DSC and XPS were utilized for additional characterization in order to explore the mechanism behind the increased catalytic activity of the as-synthesised K(x)-γ-MnOOH (x = 6.0, 6.7, and 6.9). And it is found that after KOH treatment that the surface oxygen vacancy concentration of γ-MnOOH is significantly enhanced by a surface hydroxyl dehydration of γ-MnOOH and thus promoted an increase of the catalytic activities of K(x)-γ-MnOOH (x = 6.0, 6.7 and 6.9) in the carbonylation of BuNH₂ with CO₂. This method provides a simple, economical, and effective way to enhance the catalytic activities of metal oxides in CO₂ capture and utilization.