Waste eggshell membrane-templated three-dimensional CoOx catalyst for efficient low-temperature toluene oxidation with strong thermal stability

Abstract

Eggshell membrane was used as the template to synthesize three-dimensional network CoOx catalysts. Besides, hydrogen reduction at 650 °C was adopted to simultaneously remove poisoned sulfur species and produce metal Co, which was self-oxidized on the catalyst surface at room-temperature, accompanied with better reducibility. Compared to counterpart CoOx (direct calcination of C4H6CoO4∙4 H2O), CoOx synthesized by using eggshell membrane possesses more Co3+ and lattice oxygen because its three-dimensional network structure is beneficial to the mass transfer of the reaction. The structure of applied catalyst will be reformed during the oxidation process. Although the active Co species are Co3+, the spillover of hydrogen from Co0 to surface leads to a better reducibility of ESM-CoOx, which significantly improves the low-temperature toluene oxidation activity of the catalyst. As a result, ESM-CoOx exhibits a best low-temperature catalytic activity of toluene oxidation (reaching 99% conversion at 250 °C, toluene reaction rate at 225 °C is 2.98 μmol gcat−1 s−1). Importantly, the above cobalt catalyst shows excellent thermal stability and 5 vol% water resistance at 250 °C. This work thus provides a novel process to tail highly active CoOx catalyst for low-temperature volatile organic chemicals oxidation in real application.