Strong microwave-absorbing catalyst Ni/CaO-CNT synthesis via enhancing magnetic loss for low carbon biodiesel production

Microwave-assisted technology has emerged as an efficient approach to enhance heterogeneously catalyzed transesterification reactions to produce fatty acid methyl esters (FAME), which are the major components of biodiesel. Our previous studies have confirmed that the dielectric loss capability of the catalyst plays a crucial role in enhancing catalytic activity under microwave fields. However, in addition to dielectric loss performance, the impact of magnetic loss performance on material absorption performance must not be overlooked. To address this gap, this study systematically investigates the role of magnetic loss in microwave-assisted transesterification. Herein, we successfully synthesized a magnetic catalyst (Ni/CaO-CNT) and non-magnetic catalyst (Cu/CaO-CNT) to investigate influence of magnetic loss on transesterification, evaluated the catalytic performance in transesterification reaction of palm oil and methanol. The results indicated that Ni doping optimized the magnetization of Ni/CaO-CNT (5.4 emu/g), and when compared to Cu/CaO-CNT, the magnetic loss ability of Ni/CaO-CNT was increased by 6.5 times, greatly enhancing its microwave-absorbing capacity. Although Cu/CaO-CNT catalyst had a higher basicity (0.68 mmol/g) than the Ni/CaO-CNT (0.65 mmol/g), the Ni/CaO-CNT demonstrated superior catalytic performance under microwave conditions, achieving a transesterification conversion of 94.4% compared to 87.3% of Cu/CaO-CNT, an over 7% improvement that demonstrates magnetic loss significantly enhances catalytic efficiency beyond what can be achieved through basicity alone. Moreover, the turnover frequency (TOF) of Ni/CaO-CNT reaches 84.28 h −1 , substantially higher than that of Cu/CaO-CNT (68.12 h −1 ). Compared to the non-magnetic catalyst, Cu/CaO-CNT, the Ni/CaO-CNT catalyst saves 38.5% of energy consumption and reduces 2.1 kg of CO 2 per kilogram of FAME produced.