Heavy oil has been regarded as the most available alternative energy resource.However,it exploitation is still confronted with great challenge due to its high density and viscosity.In-situ combustion,the most promising strategy for heavy-oil exploitation,has only limited applications because of its great dependence on geological characteristics as well as oil property.The use of heterogeneous catalysts is expected to be a sustainable route to tune the oxidation behavior of heavy oil and to extend the applicability of in-situ combustion.Herein,MnO2 nanoparticles have been employed to facilitate the cracking of heavy compounds,promote the heat production,and improve the recovery efficiency.It was observed that the MnO2 doubled the oxidative decomposition of heavy oil in the low temperature interval,and accelerated the heat-releasing rate in the high temperature interval.The increased weight loss at low temperatures was attributed from the decomposition of heavy components since light compounds were removed away before experiments.The addition of MnO2 decreased the apparent activation energies of the oxidation reactions both at low and high temperatures,calculated by the distributed activation energy model.The performance of the MnO2 is expected not only to make in-situ combustion to be feasible for wider oil reservoirs,but also to be promising for all the thermal recovery processes to improve oil recovery and give an updating effect of the produced oil.