Effect of small molecular organic acids on the structure and catalytic performance of sol-gel prepared cobalt cerium oxides towards toluene combustion

Abstract

Cobalt cerium oxide catalysts with small molecular organic acids (SOAs) as chelatingagents were prepared via the sol-gel method and investigated for the complete oxidation of toluene.Four kinds of natural SOAs, i.e. malic acid (MA), citric acid (CA), glycolic acid (GA), and tartaricacid (TA), were selected. The effect of organic acids on the composition, structure, morphology andcatalytic performance of metal oxides is discussed in details. The cobalt cerium oxides catalysts werecharacterized by various techniques, including TG-DSC, XRD, SEM-EDS, N2-adsorption anddesorption, XPS, and H2-TPR analyses. The results show that the nature of organic acids influencedthe hydrolysis, condensation and calcination processes, as well as strongly affected the textural andphysicochemical properties of the metal oxides synthesized. The best catalytic activity was obtainedwith the CoCe-MA catalyst, and the toluene conversion reached 90% at 242 °C. This outstandingcatalytic activity could be related to its textural, redox properties and unique surface compositionsand oxidation states. In addition, the CoCe-MA catalyst also showed excellent stability in long-timeactivity test.