The application of highly active vermiculite-based hydrotalcite-derived catalysts in methane dry reforming: The impact of promoter doping on carbon deposition

Abstract

The dry reforming of methane (DRM) exhibits promising potential for the treatment and valorization of greenhouse gases; however, catalyst deactivation remains a significant challenge faced by this process. In this study, wastewater generated during the activation of vermiculite was utilized as a raw material to synthesize bimetallic layered double hydroxide (LDH) materials. Various additives such as X (La, Ce, Sm) were incorporated into the VMT-X-NiCoHTlcs catalysts using an impregnation method. The physicochemical properties of the catalysts were characterized employing techniques such as X-ray diffraction (XRD), Nitrogen adsorption-desorption, hydrogen temperature-programmed reduction (H₂-TPR), and thermogravimetric analysis (TG). The catalytic activity was subsequently tested in a fixed-bed reactor at 750 °C under atmospheric pressure. Overall, all catalysts demonstrated excellent activity (with CH₄ conversion rates exceeding 85 % and CO₂ conversion rates surpassing 90 %) and stability over 24 h. This performance is likely attributed to the ionic level distribution of the active components Ni and Co within the layered double hydroxide structure, which can provide small particle sizes and uniform dispersion of active species through leaching during pretreatment, resulting in strong metal-support interactions. Furthermore, the incorporation of additives (X = La, Ce, Sm) significantly enhances the carbon deposition behavior of the catalyst. It has been observed that the addition of these additives facilitates the activation of CO₂ molecules, suppresses the excessive cracking of CH₄, and achieves a balance with the dissociation of CH₄, thereby reducing the formation of carbon deposits.