Sustainable hydrogen production and CO₂ mitigation from acetic acid dry reforming over Ni/Al₂O₃ catalyst

Dry reforming of acetic acid (DRA) was first-time investigated on 10%Ni/Al₂O₃ at varied temperatures within 923–973 K employing several CO₂:CH₃COOH ratios of 1.5:2; 1:1; and 2:1. Depending on NiO particle size and location on support surface or inside the porous support structure, the H₂ reduction of NiO phase to active metallic Ni⁰ form was evidenced at different reduction temperatures within 550–950 K and the estimated degree of reduction was about 73.68%. Weak, medium, and strong basic centres were evidenced on 10%Ni/Al₂O₃ via CO₂ desorption measurement. Increasing DRA temperature improved both CH₃COOH and CO₂ conversions with the corresponding apparent activation energy of 100.71 and 58.50 kJ mol⁻¹. As CO₂ partial pressure was increased from 0 to 40 kPa, the initial CH₃COOH conversion was noticeably enhanced from 30.5% to 97.8% whilst H₂/CO ratio always remained less than unity (0.73–0.77). Notably, DRA was a two-step process and barely negligible CH₄ intermediate product was evidenced since it was promptly reformed by CO₂ into syngas. The Ni⁰ active form was not susceptible to oxidation during DRA and carbon deposited on spent catalyst surface was heterogeneous in nature with the evident co-existence of amorphous and graphitic carbons.