Preparing a Zr-Doped CeO<sub>2</sub> Nanorod to Improve the Catalytic Performance of the Ni-Based Catalyst for Dry Reforming of Methane by Enhancing Oxygen Supply
Zongpeng Zou, Tao Zhang, Li Lv, Wenxiang Tang, Guoquan Zhang, Raju Kumar Gupta, Yan Wang, Shengwei Tang
Abstract
Dry reforming of methane (DRM) is a feasible route to realize the resource utilization of greenhouse gases CO 2 and CH 4 . The Ni-based catalyst is recognized as a potential catalyst for the industrialization of DRM. However, catalyst deactivation caused by carbon deposition is a challenge. Providing enough active oxygen species to accelerate the reaction between CH x ( x = 0–3) and oxygen species is the key to inhibit coking. Ni-based catalysts loaded on a Zr-doped Ce 1– x Zr x O 2 nanorod were prepared by a one-step hydrothermal method. Benefiting from lattice distortion caused by Zr doping, the Ni/Ce 0.95 Zr 0.05 O 2 catalyst showed the best catalytic activity and stability. Compared with the Ni/CeO 2 catalyst, the activation energy of CH 4 and CO 2 decreased by 20 and 22%, respectively. The 100 h stability test showed that the Ni/CeO 2 catalyst was 10% deactivated, and the carbon deposition rate was 0.82 mg c ·g cat · –1 ·h –1, while the Ni/Ce 0.95 Zr 0.05 O 2 catalyst showed excellent stability. The extensive characterization of the catalysts indicated that the enhancement in DRM activity upon Zr doping could be attributed to the increase of oxygen vacancies and the improvement in lattice oxygen mobility. However, excessive Zr doping formed ZrO 2 covering oxygen vacancies, resulting in decreased catalytic activity and stability. The results showed that lattice oxygen over the Ni/Ce 0.95 Zr 0.05 O 2 catalyst not only participated in the oxidation of carbon intermediates but also contributed to the deep dissociation of CH 4 over Ni through an oxygen-mediated dissociation pathway. Similarly, the redox cycle on the oxygen vacancies was also important for enhancing the CO 2 adsorption activation to relieve the coking of the catalyst.