Deciphering the ZrO2 phase engineering effects on dry reforming of methane over the Ni/ZrO2 catalysts

Abstract

The Ni/ZrO2 catalyst, with inexpensive price, high activity and excellent thermostability, has been widely investigated for dry reforming of methane (DRM). However, the stability of the catalyst still remains challenging due to the inevitable Ni sintering and carbon deposition under the high-temperature operation. Herein, the effects of the ZrO2 phase engineering in the Ni/ZrO2 catalyst on the DRM performance are highlighted. The characterization results reveal that the rising precipitated temperature can improve the tetragonal ratio (vt) in the catalysts using KOH as the precipitant and the catalyst with higher vt can be obtained via employing Na2CO3 or NaOH as the precipitant. The increased vt might be caused by the increased Ni content inserted into the ZrO2 support lattice. Ni dispersion is promoted with the raised vt resulting from the enhanced metal-support interaction. Besides, stronger acidity-basicity and more defects, including Zr3+ and surface oxygen species, are also detected on the catalyst with higher vt. Thus, the activity and stability over the Ni/ZrO2 catalysts displays a positive relation with the vt value. Especially, the conversions of CH4 and CO2 over the catalyst precipitated at 80 °C with NaOH as the precipitant are 80% ∼ 62% and 85% ∼ 72%, respectively, after evaluated for 3600 min with 4.3% carbon deposition. It has also been identified that the tetragonal ZrO2 plays a vital role in restraining carbon accumulation and graphitization. Furthermore, the infrared spectroscopy experiments illustrate that the reactive oxygen species are richer on the catalyst with higher vt and easier to react with CH4.