Effect of low-loading of Ni on the activity of La0.9Sr0.1FeO3 perovskites for chemical looping dry reforming of methane.

Methane dry reforming (MDR) is a very appealing process to bring back waste CO 2 into the chemical production chain. Operating in chemical looping (CL) conditions allows to reduce deactivation by coke deposition and facilitates the use of concentrating solar energy to power this reaction. Perovskites have successfully applied as oxygen carriers for chemical looping, and those of the family La 1−x Sr x FeO 3 having lower Sr content have showed high activity and cycling stability for MDR. To further enhance the performance of these oxygen carriers, in this work we evaluate the impact of dispersing Ni in low concentration (<1 mol %) on the performance of La 0.9 Sr 0.1 FeO 3 for CL-MDR. Simple impregnation allows to distribute evenly the metal, which according to XPS is present as Ni2+ in the fresh material. CH 4 -TPR reveal that NiO x species are firstly reduced at around 650 ºC and they shift the onset of methane partial oxidation to lower temperatures with regards to the unmodified perovskite. However, during isothermal CL tests at 850 ºC, the presence of Ni does not modify much the syngas production during the methane reforming stage, although the H 2 /CO ratio increases with the presence of this metal. This indicates an increment in the contribution of methane cracking. In contrast, when feeding CO 2, the generation of CO is greatly enhanced by the incorporation of Ni, particularly at a loading of 0.4 mol %, while higher metal concentration are slightly less effective. Higher CO generation is attributed to the promotion of reverse Boudouard reaction, which can remove the coke previously deposited in the methane reforming stage. Accordingly, the Ni/ La 0.9 Sr 0.1 FeO 3 presents stable activity during several consecutive cycles. [Display omitted] • Low concentration of Ni (<1 mol %) was incorporated by wet impregnation on La 0.9 Sr 0.1 FeO 3. • Ni/ La 0.9 Sr 0.1 FeO 3 samples present high activity for chemical looping methane dry reforming at 850 ºC. • The presence of Ni does not increase substantially the activity for methane partial oxidation but increase the H 2 /CO ratio. • In contrast, Ni remarkably promote CO formation during the CO 2 stages with regards to the unloaded perovskite. • Stable activity is observed during 5 cycles due to the efficient coke removal by reverse Boudouard reaction. [ABSTRACT FROM AUTHOR]