Superior stability of Ca-La co-doped Ni/BN catalyst for biogas reforming to methanol syngas

Abstract

Ni-based catalysts are often easily deactivated during biogas reforming due to sintering, carbon deposition and other reasons. In this study, Ni was used as the active component and BN was used as the carrier to explore the doping of Ca, Ce and La to enhance the basicity of the catalyst. Ca, Ce and La can form Ca₂BO₄, CeBO₃, LaBO₃ and the like with the carrier BN while improving the dispersibility of the active components. The co-doping of Ca and La not only forms gradient alkaline sites, but also improves the interaction between the active components and the carrier, promotes the adsorption of CO₂ and carbon deposition activation, and improves the thermal stability of the catalyst. In addition, the effects of doping La and co-doping CaLa on the activity and stability of the catalyst were compared. Characterization results such as XRD, XPS, TG, TEM, Raman, H₂-TPR and CO₂-TPD show that NiCaLaCeBN has more alkaline adsorption sites and stronger thermal stability than NiLaCeBN. Under the conditions of reaction temperature of 800 °C, WHSV = 31,310 mLg_Cat⁻¹h⁻¹, CH₄:CO₂:N₂:H₂O molar ratio of 3:2:1:2, the conversion rate of NiCaLaCeBN catalyst is about 95 % (CH₄), 54 % (CO₂), and the product H₂/CO ratio is close to 2. After continuous operation for 200 h, it still maintains excellent activity and stability.