Biogas dry reforming over Li–Ni–Al LDH-derived catalysts.

Biogas dry reforming or dry reforming of methane (DRM) is an alternative to produce hydrogen, in the context of development of sustainable routes for energy production, since this route uses CH 4 and CO 2 , two greenhouse gases as reactants. However, the deactivation of catalysts due to carbon deposition and sintering is the main drawback of this reaction. In this work, with the aim of minimizing carbon formation and sintering during DRM, the effect of lithium as a promoter in catalysts Ni–Al derived from layered double hydroxides was investigated. The catalysts were prepared by co-precipitation and characterized by different techniques: BET surface area (S BET), X-ray diffraction (XRD), temperature-programmed reduction (TPR), CO 2 and H 2 temperature-programmed desorption (CO 2 -TPD and H 2 -TPD), Scanning Electron Microscopy (SEM-EDS), temperature-programmed oxidation (TPO). The catalytic tests were carried out in a fixed bed reactor using a synthetic biogas (60% CH 4 and 40% CO 2) in the temperature range of 500–750 °C. The incorporation of Li into the Ni–Al-LDH changed the reducibility and basicity of the catalysts. The Li2 sample containing an intermediary amount of Li (5 wt%) showed the highest reduction temperature and highest density of basic sites, which resulted in the smallest Ni crystallite size before and after the reactions. As a result, this catalyst presented the greater resistance to sintering and a lower rate of carbon produced. For the reaction carried out at 700 °C, only the Li2 catalyst remaining active during the test and reaching a maximum of 80% and a final CH 4 conversion of 54% after 480 min of reaction, whereas CO 2 conversion was higher than 90%. All other samples deactivated at different rates due to carbon deposition and sintering. [Display omitted] • Li–Ni–Al LDH-derived catalysts were successfully prepared by coprecipitation. • The introduction of Li changes the reducibility and the basicity of Ni–Al. • Sample with 5 wt% Li showed the smallest crystallite size and the highest basicity. • Sample with 5 wt% Li showed the highest sintering resistance and the lowest carbon rate. • Catalyst with 5 wt% Li was the only one that maintained activity with time-on-stream at 700 °C. [ABSTRACT FROM AUTHOR]