Study on oxidation activity of Ce–Mn–K composite oxides on diesel soot

Abstract

As an effective method, diesel particulate filter (DPF) technology has a great contribution in reducing soot emissions from diesel engines. To achieve passive regeneration of DPF at low temperatures, K-doped ce 0.5 Mn 0.5 o 2 catalysts were synthesized using sol-gel method. The effect of K-doped catalysts-K z-ce 0.5 Mn 0.5 o 2-on the oxidation of soot had been studied by thermogravimetric analysis, and the corresponding catalytic properties were evaluated based on X-ray diffraction (XRD), hydrogen temperature programmed reduction (H 2-TPR), O 2 temperature programmed desorption (O 2-TPD) Raman spectroscopy (Raman), Brunauer-Emmett-Teller (BET) and Fourier-Transform-Infrared (FTIR). The results showed that K doping facilitated the oxidation of diesel particulate matter, which was indicated by the entire mass loss curve shifting to lower temperatures. K 0.2-ce 0.5 Mn 0.5 o 2 showed the best performance among the series of K-doped catalysts. Compared with the findings for Ce 0.5 Mn 0.5 o 2 , the ignition temperature of soot oxidation (T i) had been lowered by 28 ℃, and the maximum peak combustion temperature (T m) of the dry soot decreased by 61 °C. Furthermore, compared with the ce 0.5 Mn 0.5 o 2-catalyzed reaction, K doping led to a lower activation energy and significantly improved pre-exponential factor. The minimum reaction activation energy of 27.46 kJ/mol was exhibited by K 0.2-ce 0.5 Mn 0.5 o 2. Diesel vehicles are currently attracting interest owing to their distinctive characteristics of superior power performance and fuel economic properties 1-3 while the pollutants contained in diesel exhaust gas, particularly soot, pose hazards to human's living environment and become one of the source of greenhouse gas which leads to global warming. Therefore, finding proper ways to cut down soot emissions from diesel engines become one of the researching hotpots in the study progress of diesel vehicles, that' why many researchers studied diesel particulate filters (DPF), an effective methods of lowering soot emissions by passive regeneration by chemical catalysis and improving the temperature of the diesel exhaust which is sufficient for soot to burn out. Hence, selecting a suitable catalyst is the key challenge for regeneration 4-8. It is well known that the utilization rate of rare earth resources is low, despite their abundance. CeO 2 plays an important role in three-way catalysts owing to its excellent oxygen storage and release properties 9. Generally, CeO 2 performs as an oxygen buffer to store excess oxygen quickly as the oxygen concentration in the exhaust gas is increasing to higher level, and releasing oxygen promptly at low oxygen concentrations 10-12. In addition, CeO 2 is a promising noble metal substitute for improving the anti-poisoning performance and high temperature durability of catalysts 13,14. The technology of Ce-based catalysts is still constantly improving after decades of development. The unique chemical and physical properties of rare earth-based catalysts present due to their electronic ener...

Study of spatial and temporal aging characteristic of catalyzed diesel particulate filter catalytic performance used for diesel vehicle

“…The XRD, XPS and catalytic activity evaluation were used to characterize the aging performance of the CDPFs. The XRD is a research method to obtain the information of material composition, internal atomic or molecular structure or morphology through the analysis of X-ray diffraction and diffraction patterns, which can accurately measure the crystal structure and crystal size 32 . The XPS is an effective method to measure the composition and chemical state of surface elements of the materials by quantitatively evaluating the binding energy peak intensity and peak displacement of different atoms or molecule 33 .…”

Revealing the promoting effect of multiple Mn valences on the catalytic activity of CeO2 nanorods toward soot oxidation

“…9 Many catalysts have been successfully fabricated, such as metal oxides, noble metals, and perovskites. 6,10–22…”

“…9 Many catalysts have been successfully fabricated, such as metal oxides, noble metals, and perovskites. 6,[10][11][12][13][14][15][16][17][18][19][20][21][22] Noble metals exhibit a high activity as commercial catalysts; however, they are expensive and have limited reserves. 23 Developing efficient and inexpensive metal oxides is thus an alternative for removing soot particles.…”

“…Doping with transition metals or alkaline metals is an effective strategy to improve CeO 2 nanomaterials' performances. 13,[30][31][32][33] Nevertheless, the catalytic activities of modified CeO 2 are highly dependent on the chosen doping element and its chemical states. 30,32,34,35 Previous works suggest that Mnmodified CeO 2 nanomaterials can exhibit considerable catalytic activity in soot oxidation because of Mn's variable valence states and the synergistic effect between Mn and Ce.…”

Preparation of K Modified Three-Dimensionally Ordered Macroporous MnCeOx/Ti0.7Si0.3O2 Catalysts and Their Catalytic Performance for Soot Combustion

“…To improve the stability of K-based catalysts, the incorporation of K into other stable structures is considered to be a promising way to resolve the problem of thermostability, and many kinds of K-doped catalysts have been reported by previous literature [31][32][33]. However, how to effectively combine the good contact efficiency of 3DOM structure and high catalytic activities of K, Mn, and Ce in one system of catalysts is also a research hotspot in the design and preparation of catalysts [34,35].…”