Effects of pretreatment atmospheres on the catalytic performance of Pd/γ-Al2O3 catalyst in benzene degradation

•Effects of atmosphere pretreatment on catalytic performance of Pd/γ-Al2O3 were studied.•Inert atmosphere pretreatment led to modified crystal structure, with crystalline PdO transformed to amorphous state.•Crystal structure is another important factor affecting the catalytic activity besides chemical state.

In the current paper, a strategy for catalytic degradation of benzene over Pd/γ-Al2O3 catalysts via different atmospheres (H2, N2, He and air) pretreatment was carried out in a fixed bed reactor. The experimental results indicated that H2, N2, and He pretreatments have a significant positive effect on the initial activity of the catalyst compared to air. We have also investigated the effects of pretreatment atmospheres on the catalytic performance for benzene degradation through the information on the chemical state and crystal structure of the catalysts using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and CO chemisorption measurements techniques. The chemical state of Pd species decreased via H2 pretreatment, leading to the increase of the initial catalytic activity, while chemical state increased accompanying with a decrease in degradation benzene via air pretreatment. There is no change in the chemical state of Pd species using inert atmosphere (N2 and/or He) pretreatment, but the initial activity of the catalyst improved significantly due to the modified crystal structure of Pd species in the catalysts, with the crystalline PdO being transformed to amorphous state.

Graphical abstractA strategy for catalytic degradation of benzene over Pd/γ-Al2O3 catalysts via different atmosphere (H2, N2, He and air) pretreatments was carried out in a fixed bed reactor. The experimental results indicated that H2, N2, and He pretreatments have a significant positive effect on the initial activity of the catalyst compared to air. The chemical state of Pd species decreased via H2 pretreatment, leading to the increase of the initial catalytic activity, while chemical state increased accompanying with a decrease in degradation benzene via air pretreatment. There is no change in the chemical state of Pd species using inert atmosphere (N2 and/or He) pretreatment, but the initial activity of the catalyst improved significantly due to the modified crystal structure of Pd species in the catalysts, with the crystalline PdO being transformed to amorphous state.Figure optionsDownload full-size imageDownload as PowerPoint slide