Effect of surface manganese oxide species on soot catalytic combustion of Ce-Mn-O catalyst

Constructing cerium and manganese bimetallic catalysts with excellent catalytic performance for soot combustion is the research frontier at present.In order to find out the key factors for catalytic soot combustion of Ce-Mn-O catalysts,a series of Ce-Mn-O catalysts with different Ce/Mn proportions were prepared by co-precipitation method.The activity test results show that it increases first and then decreases with the increase of Mn content.The best catalytic activity is obtained for Ce_(0.64)Mn_(0.36) catalyst,which shows a maximum rate temperature(T_(m)) at 306℃ for CO_(2) production in TPO curve.Compared with non-catalytic soot combustion,the T_(m) decreases by mo re than 270℃.Syste matical characte rization results suggest that when the adsorbed surface oxygen,lattice oxygen,specific surface area and total reduction amount of the catalysts reach a certain value,the key factors leading to the difference of catalytic activity become the readily reducible and highly dispersed surface manganese oxide species and contact performance of the external surface.The surface manganese oxide species is beneficial to improving the low-temperature reducibility of catalysts and the porous surface is conducive to the contact between catalyst and soot.Furthermore,for the soot combustion reaction containing only O_(2),the promoting effect of Mn^(4+)is not obvious.

Effect of yttrium and manganese addition on catalytic soot combustion activity and anti-high-temperature stability of CeO_(2) catalyst

In order to analyze the influence of the addition of yttrium and manganese on the soot combustion performance and high temperature stability of CeO_(2) catalyst,a series of Y/Mn-modified CeO_(2) catalysts were prepared.The effects of structural properties,textural properties,oxygen vacancies,Ce^(3+),surface adsorbed oxygen species,reduction properties and desorption properties of oxygen species on the activity were analyzed by various characterization methods.The results of the activity test show that the addition of manganese is beneficial to enhancement of the activity,while the addition of yttrium increases the amount of reactive oxygen species,but decreases the activity.After aging at 700℃,the activity of the CeMn catalyst decreases most sharply,while the catalytic activity of the CeY catalyst can be maintained to a certain extent.Interestingly,the addition of yttrium and manganese at the same time can stabilize the activity.The fundamental reason is that yttrium and manganese move to the surface of the solid solution after aging,which increases the reduction performance of the catalyst,thus contributing to the increase of activity.Although the activity of CeYMn catalyst decreases after aging at 800℃,it is still higher than that of other catalysts aged at 700℃.