Role of Preparation Method in Tailoring Ni/Al2O3 Catalysts for Low-Pressure Methanation

Abstract Methanation is an important technological process producing synthetic natural gas. This study compares five preparation methods for Ni/Al 2 O 3 catalysts and discusses their impact on the formation of Ni active sites and their methanation activity. Conventional wet impregnation was evaluated alongside methods involving microwave-assisted deposition (MC), ultrasonic waves (UT), and pH-adjusted methods such as ammonia evaporation (AE) and deposition precipitation (DP). These techniques primarily influenced the size of Ni active sites as well as their reducibility and stability. The stability of NiO/Ni species after reduction and methanation was described. Their performance of prepared Ni/Al 2 O 3 was assessed in CO 2 methanation within a temperature range of 250–490 °C under a low gauge pressure of 0.2 MPa. The highest methane yield of 42% was obtained with the MC catalyst; however, a high reaction temperature of 449 °C was needed. On the other hand, both DP and AE catalysts outperformed all tested catalysts in the catalyst productivity. This was due to the smaller Ni/NiO particles and their higher thermal stability. Graphical Abstract