Comparison of Different Metal Doping Effects on Co3O4 Catalysts for the Total Oxidation of Toluene and Propane

Abstract

Metal-doped (Mn, Cu, Ni, and Fe) cobalt oxides were prepared by a coprecipitation method and were used as catalysts for the total oxidation of toluene and propane. The metal-doped catalysts displayed the same cubic spinel Co3O4 structure as the pure cobalt oxide did; the variation of cell parameter demonstrated the incorporation of dopants into the cobalt oxide lattice. FTIR spectra revealed the segregation of manganese oxide and iron oxide. The addition of dopant greatly influenced the crystallite size, strain, specific surface area, reducibility, and subsequently the catalytic performance of cobalt oxides. The catalytic activity of new materials was closely related to the nature of the dopant and the type of hydrocarbons. The doping of Mn, Ni, and Cu favored the combustion of toluene, with the Mn-doped one being the most active (14.6 × 10−8 mol gCo−1 s−1 at 210 °C; T50 = 224 °C), while the presence of Fe in Co3O4 inhibited its toluene activity. Regarding the combustion of propane, the introduction of Cu, Ni, and Fe had a negative effect on propane oxidation, while the presence of Mn in Co3O4 maintained its propane activity (6.1 × 10−8 mol gCo−1 s−1 at 160 °C; T50 = 201 °C). The excellent performance of Mn-doped Co3O4 could be attributed to the small grain size, high degree of strain, high surface area, and strong interaction between Mn and Co. Moreover, the presence of 4.4 vol.% H2O badly suppressed the activity of metal-doped catalysts for propane oxidation, among them, Fe-doped Co3O4 showed the best durability for wet propane combustion.

Multi‐Functional Cerium Modification to Accelerate the Oxygen Reduction Reaction of Spinel Co3O4

“…Compared with pure Co 3 O 4 , the Raman bands of the x % CeÀ Co 3 O 4 samples are more weak and broad because of the incorporation of Ce into the Co 3 O 4 lattice, resulting in lattice expansion and lattice distortion, as revealed by XRD analysis. [16] With the increase of Ce content, the intensity of band at ∼ 465 cm À 1 where corresponds to the Raman active F 2g mode of cubic fluorite type CeO 2 [17] becomes higher, indicating the formation of CeO 2 for the x % CeÀ Co 3 O 4 samples.…”

“…Compared with pure Co 3 O 4 , the Raman bands of the x % CeÀ Co 3 O 4 samples are more weak and broad because of the incorporation of Ce into the Co 3 O 4 lattice, resulting in lattice expansion and lattice distortion, as revealed by XRD analysis. [16] With the increase of Ce content, the intensity of band at ∼ 465 cm À 1 where corresponds to the Raman active F 2g mode of cubic fluorite type CeO 2 [17] becomes higher, indicating the formation of CeO 4b) reveals two major peaks with binding energy at ∼ 779.6 and ∼ 794.6 eV with a spin energy separation of 15 eV, corresponding to the Co 2p 3/2 and Co 2p 1/2 , respectively. [18] In detail, the Co 2p 3/2 peak can be divided into two peaks, which is ascribed to Co 3 + (∼ 779.6 eV) and Co 2 + (∼ 781.1 eV) respectively.…”

“…As shown in Figure 4a, five characteristic bands at 671, 607, 513, 470, and 192 cm À 1 corresponding to the stretching mode of spinel Co 3 O 4 (A 1g , F 3 2g , F 2 2g, E g , F 1 2g symmetry) are clearly observed. [16] Among them, the band at ∼ 192 cm À 1 reveals the tetrahedral sites of CoO 4 , while the band at 671 cm À 1 reveals the octahedral sites of CoO 6 . Compared with pure Co 3 O 4 , the Raman bands of the x % CeÀ Co 3 O 4 samples are more weak and broad because of the incorporation of Ce into the Co 3 O 4 lattice, resulting in lattice expansion and lattice distortion, as revealed by XRD analysis.…”

“…As shown in Figure 4a, five characteristic bands at 671, 607, 513, 470, and 192 cm À 1 corresponding to the stretching mode of spinel Co 3 O 4 (A 1g , F 3 2g , F 2 2g, E g , F 1 2g symmetry) are clearly observed. [16] Among them, the band at ∼ 192 cm À 1 reveals the tetrahedral sites of CoO 4 , while the band at 671 cm À 1 reveals the octahedral sites of CoO 6 .…”

Hydrothermal deposition as a novel method for the preparation of Co–Mn mixed oxide catalysts supported on stainless steel meshes: application to VOC oxidation

“…Cai et al demonstrated that Mn introduction leads to increased surface Co 2+ concentration and active oxygen, which contributed to high catalytic activity in VOC oxidation (Cai et al, 2015). In a recent study (Zhang et al, 2020), the introduction of Mn increased reducibility and catalytic performance of cobalt oxides. The Co-Mn oxide catalysts were more active in toluene oxidation than their Co-Ni or Co-Cu analogues.…”