Development of multiple alkali metals doped La-Ni based perovskites for CO2 gasification of biochar to produce CO rich syngas

Abstract

Under the background of carbon neutrality, there is an urgent need for the production of high-valued syngas from renewable carbon resources. This work focused on the evaluation of multiple alkali metals doping on the catalytic activity of La-Ni based perovskite catalysts in CO2 gasification of biochar. The structure and property evolution of samples were analyzed by XRD, SEM, TEM, XPS, Raman spectra, CO2-TPD, etc. The experiment results found that Li+ exhibited a stronger catalytic gasification promotion effect than K+ and Na+, owing to the high mobility of the smallest radius ions in the lattice. Among the samples, La0.4K0.2Na0.2Li0.2NiO3 possessed the best catalytic performance with the maximum release rates of CO of 116.76 mL min−1·g−1 and 3.25 times in reactivity indexes in contrast to the LaNiO3. Correspondingly, it also showed significant resistance to ash in the cycle gasification experiments. Deep substitution with multiple alkali metals at A-site produced more active oxygen species ([O]) on the oxygen vacancies (Ov) and increased the proportion of Ni3+ of the La0.4K0.2Na0.2Li0.2NiO3, resulting in excellent catalytic CO2 gasification capacity. Furthermore, the adsorption and activation capacity of CO2 were also enhanced by the surface basic active sites generated by alkali metals substitution. Based on the experiments and characterization results, the redox recycling between Ni2+−Ov and Ni3+−[O] were proposed as the main reaction mechanisms for CO2 gasification of biochar. This study provides a valuable exploration for the complex substitution of perovskite catalysts and high-efficiency CO2 gasification of biochar.