Reactive Grinding Synthesis of LaBO3 (B: Mn, Fe) Perovskite; Properties for Toluene Total Oxidation

Abstract

LaBO3 (B: Mn, Fe) perovskites were synthesized using a three-step reactive grinding process followed by a calcination at 400 °C for 3 h. The three successive steps are: (i) solid state synthesis (SSR); (ii) high-energy ball milling (HEBM); (iii) low-energy ball milling (LEBM) in wet conditions. The impact of each step of the synthesis on the material characteristics was deeply investigated using physico-chemical techniques (X-ray diffraction (XRD), N2-physisorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS)) and the catalytic performances of the synthesized materials were evaluated for the toluene total oxidation reaction. Starting from single oxides, microcrystalline perovskite phase, exhibiting negligible surface areas, is obtained after the SSR step. The HEBM step leads to a drastic reduction of the mean crystal size down to ~20 nm, along with formation of dense aggregates. Due to this strong aggregation, surface area remains low, typically below 4 m2·g−1. In contrast, the second grinding step, namely LEBM, allows particle deagglomeration resulting in increasing the surface area up to 18.8 m2·g−1 for LaFeO3. Regardless of the perovskite composition, the performance toward toluene oxidation reaction increases at each step of the process: SSR < HEBM < LEBM.