3DOM SiO₂-Supported Different Alkali Metals-Modified MnOx Catalysts: Preparation and Catalytic Performance for Soot combustion

Abstract

A series of novel and cheap catalysts, which contain three‐dimensionally ordered macroporous (3DOM) structure and alkali‐doped MnOx nanoparticles, were designed and prepared by a facile method. The physical and chemical properties of as‐prepared catalysts were characterized by XRD, SEM, TEM, Raman and H2‐TPR and so on. The as‐prepared catalysts exhibit excellent catalytic performance for soot combustion, which the T10, T50 and T90 are 275 oC, 323 oC and 351 oC, respectively. This activity result is comparable to or even higher than noble metal catalyst in the medium and high temperature range. The high catalytic activities of as‐prepared catalysts are attributed to marcroporous structure, nano‐effect, immobilization effect and synergistic effect. Based on the analysis results, the possible reaction mechanisms of catalysts for soot combustion, were also proposed. Due to easy synthesis, low cost, high activity, the as‐prepared catalysts are promising for practical applications, and this work also provides potential research approaches to get excellent catalysts.

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

“…As shown in the Figure 4b-e, the reduction peaks can be divided into four ranges of 178-250 • C, 280-350 • C, 350-450 • C, and >650 • C. Due to the large negative reduction potential, MnO was not reduced to Mn 0 , even above 950 • C. Therefore, MnO was considered to be the final state for the preparation of catalyst reduction [47,48]. According to the reduction process of Mn-based oxides, the first peak at 178-250 • C may be attributed to MnO 2 reduction to Mn 2 O 3 , the second peak at 280-350 • C could be related to Mn 2 O 3 reduction to Mn 3 O 4 , and the third peak at 350-450 • C could belong to the Mn 3 O 4 reduction to MnO [16,49]. The fourth peak at >650 • C is assigned to the reduction of CeO 2 to Ce 2 O 3 .…”

“…Therefore, M was considered to be the final state for the preparation of catalyst reduction [47,48]. cording to the reduction process of Mn-based oxides, the first peak at 178-250 °C ma attributed to MnO2 reduction to Mn2O3, the second peak at 280-350 °C could be relate Mn2O3 reduction to Mn3O4, and the third peak at 350-450 °C could belong to the M reduction to MnO [16,49]. The fourth peak at >650 °C is assigned to the reduction of C to Ce2O3.…”

“…Different morphologies of catalysts with nanotube array, nanobelt, nanofiber, nanowire, disordered macropore, and 3DOM structures are studied to enhance effective contact [9][10][11][12][13][14]. Among the above morphologies, due to the interconnected macroporous structure with large pore diameter (>50 nm) and low diffusion resistance, the 3DOM catalyst has enough migration space for soot particles in its internal pores, which are expected to show excellent catalytic ability [15][16][17]. Many previous studies have shown that the catalytic performance of 3DOM oxide-based catalysts for soot combustion is superior to that of corresponding nanoparticle catalysts due to their structural effects [18][19][20].…”

Niobium oxide promoted with alkali metal nitrates for soot particulate combustion: elucidating the vital role of active surface nitrate groups

“…26–28 Alkali metals, potassium in particular, have been investigated intensively as active components for soot combustion. 28–31 Feng et al revealed that as a good electron donor, K + cations are conducive to the adsorption and dissociation of gaseous O 2 on perovskite surfaces. For instance, the presence of K + can weaken the Fe–O or Mn–O bonds on the catalyst surface, thus some of the lattice O 2− will be converted into adsorbed active oxygen anions, which play an important role in accelerating the soot combustion.…”

Mechanistic Insights into Oxygen Dynamics in Soot Combustion over Cryptomelane Catalysts in Tight and Loose Contact Modes via 18O2/16O2 Isotopic Variable Composition Measurements – A Hot Ring Model of the Catalyst Operation

“…Thus, searching for low-cost catalytic materials that may successfully operate below 300–400 °C is currently one of the main challenges for development of efficient and durable catalytic particle filters (CDPF), which are based on earth-abundant components. Although owing to their superior activity, supported highly dispersed platinum group metals have dominated the automotive deSoot catalysis, their high cost and limited availability have triggered a continuous search for alternative cheaper materials. , Among many examined transition metal oxide systems such as spinels and perovskites or ceria-based materials, often functionalized by addition of alkali (K, Na, Li, Rb, and Cs) or f-type metals (La and Pr), − mixed oxide systems (Bi 2 O 3 –Fe 2 O 3 , Cu/BaO/La 2 O 3 , CuO/SiO 2 , or Fe 2 O 3 /SiO 2 , along with manganese (Mn 2 O 3 ) and potassium manganese oxides of layered (birnessite, OL) and tunnel (cryptomelane, OMS-2) structures , ) exhibit promising performance as soot oxidation catalysts. Activity of the latter materials may further be improved upon doping with V, Nb, or Fe, which affects the physical and chemical properties of the cryptomelane matrix, − the shape of crystallites, and the redox state of Mn, while maintaining the parent OMS-2 molecular architecture.…”