Preparation Of Manganese-based Oxides And Their Catalytic Properties For Toluene Oxidation

Volatile Organic Compounds（VOCs）refer to a wide range of contaminants that can cause damage not only to the environment but also to humans.There are various methods for the treatment of VOCs,among which catalytic oxidation technology is widely studied for its low energy consumption,high treatment capacity and universal applicability.Manganese is considered to be one of the most promising elements for application due to its extremely strong oxidation ability and multiple variable valence states.Thus,Mn₂O₃@Mn O₂ and Co_0.02Mn₂O₃ catalysts were synthesized by KMn O₄ modification and doping with cobalt,respectively,and the catalysts were assist explored by an arrangement of characterizations.In this paper,Mn₂O₃ nanosphere catalyst was synthesized by redox reaction between KMn O₄ and n-butanol with butyric acid as the soft-template agent,and different structures of Mn₂O₃ were obtained by varying the calcining temperature.In the catalytic combustion of toluene,the Mn₂O₃-500 catalyst demonstrated the best catalytic performance.XRD,N₂ adsorption and desorption,H₂-TPR,O₂-TPD,and XPS tests were used to study the physicochemical properties of catalysts.However,the disadvantages of the single Mn₂O₃ catalyst in terms of stability and poor water resistance remain unchanged.In order to improve Mn-based catalysts’catalytic activity,Mn₂O₃ surface was modified with acidic KMn O₄ to obtain Mn₂O₃@Mn O₂ catalysts with a core-shell structure,while the Mn₂O₃@Mn O₂ sample calcined at 350 ^oC exhibiting the highest catalytic activity,good stability of catalytic activity,better water resistance and the ability to be recycle used.The bulk phase structure,redox ability and the surface properties of the catalyst were characterized through a series of tests,showing that the good catalytic activity of the Mn Ox-1 catalyst was due to the surface lattice oxygen and surface Mn⁴⁺species.To further improve the stability of the catalysts,the Mn₂O₃ catalysts was modified by 2%Co and a series of Co_0.02Mn₂O₃-X（X=0,1,2 and 3 m L）catalysts were prepared by varying the amount of HCl added.It was found that Co_0.02Mn₂O₃-2 catalyst exhibited better catalytic peiformance with T₅₀and T₉₀ are 235 ^oC and 247 ^oC,respectively.At the same time,there was no significant deactivation of the catalytic activity during the24 h test.This proposes that doping cobalt can essentially move forward the activity stability of the catalysts,but the through-water steadiness still ought to be moved forward.