This work synthesized a series of Ni/CeO 2 /Al 2 O 3 catalysts with varying CeO 2 doping amounts to enhance low-temperature CO 2 methanation. The introduction of CeO 2 weakens the interaction between Ni and Al 2 O 3 , leading to the formation of Ni-CeO 2 active sites. This results in a high dispersion of Ni and CeO 2 , improved catalyst reducibility, increased number of active sites, and enhanced the CO 2 methanation. This work further investigated the impact of WHSV and catalyst stacking configuration to enhance the reaction. When the catalyst is stacked into three segments with a temperature gradient of 330 °C, 300 °C, and 250 °C under WHSV=9000 ml·h –1 ·(g cat) –1 , the CO 2 conversion significantly increases to 95%, which is remarkably close to the thermodynamic equilibrium (96%).
Ozonation process is a promising yet challenging method for the removal of refractory organic matter due to the sluggish reaction for generating hydroxyl radical (˙OH) at a neutral pH condition. Herein, an efficient heterogeneous catalytic ozonation system using CeO2/Al2O3 catalyst was developed to remove dimethyl phthalate (DMP) from wastewater. Under a neutral condition of pH = 6, this system achieved almost 100% DMP removal within 15 min at an optimized catalyst dosage of 30 g L−1 and the ozone flow rate of 22.5 mg min−1. Moreover, the catalytic ozonation system exhibited a stable degradation performance of DMP in a wider pH range (pH = 5–10). The results of electron paramagnetic resonance (EPR) and quantitative tests confirmed the ultrafast conversion of O3 to ˙OH (0.774 μM min−1) on the surface of CeO2 based ceramic catalyst. The quenching experiments further supported the predominant role of ˙OH in the mineralization of DMP. These results highlight the potential of using the heterogeneous catalytic ozonation system for the efficient removal of refractory organic matter from wastewater.
CeO 2 /Al 2 O 3 catalysts prepared by three methods were investigated for selective reduction of NO with NH 3 . It was found that the catalyst prepared by the single step sol–gel method had the best SCR activity and SO 2 resistance performance. From the results of BET, XRD, TPD and TPR, it can be concluded that large surface area, strong interaction, highly dispersed nano-crystalline ceria , high NH 3 adsorption capacity and good redox ability might be the main reasons for the excellent performance of CeO 2 /Al 2 O 3 catalyst prepared by the single step sol–gel method.
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