Key features of nano NixMg1-xAl2O4 spinel for biogas bi-reforming: CO2 activation and coke elimination

Using green and sustainable biogas as raw material to produce syngas (H 2 /CO≈2) suitable for direct synthesis of green methanol has attracted wide attention, but developing efficient catalysts with high activity/stability remains a big challenge. A series of MgAl 2 O 4 spinel catalysts (denoted as Ni x Mg 1-x Al 2 O 4 ) is designed and applied in biogas bi-reforming. The nano Ni x Mg 1-x Al 2 O 4 catalysts were comprehensively characterized by Raman, SEM, HR-TEM, H 2 -TPR, CO 2 -TPD, etc. The CO 2 activation was verified by in situ CH 4 -TPSR/CO 2 -TPO, and the key role of Ni x Mg 1-x Al 2 O 4 in coke removal behavior mechanism was further confirmed. Due to the efficient CO 2 adsorption/activation and strong metal–support interaction, nano Ni x Mg 1-x Al 2 O 4 shows excellent catalytic stability to inhibit sintering and carbon deposition . At reforming conditions of 750 °C, a weight hourly space velocity (WHSV) of 32,400 mL g Cat −1  h −1 , the Ni 0.4 Mg 0.6 Al 2 O 4 catalyst exhibits excellent CH 4 /CO 2 conversion of 91/51 % are achieved, followed by slight decrease after 40 h, and remain basically stable for the next 40 h.