New redox deposition-precipitation method for preparation of supported manganese oxide catalysts

Abstract

A new preparation method has been developed to produce homogeneous coatings of manganese compounds on alumina-coated monoliths by redox deposition-precipitation using acetone as solvent. The deposition is produced by reduction of manganese permanganate with ethanol. The Lewis acid sites on the alumina catalyze this reaction. Thus, the precipitation is produced preferentially on the surface of the monolith and not in the bulk of the solution. Monoliths prepared by this method are very active for the complete oxidation of oxygenated volatile organic compounds (VOCs). These monoliths consist of a mixture of complex phases including aluminum, sulfated alumina, potassium sulfate and manganese oxide.

Monoliths: A Review of the Basics, Preparation Methods and Their Relevance to Oxidation

“…Applications of monoliths so prepared include biomass gasification [125], methane combustion [126], oxidation [127,128] and selective catalytic reduction [129]. The technique usually involves precipitation of a metal salt with a base [130].…”

“…However, in comparison to impregnation, deposition-precipitation can present more difficulties in attaining a homogeneous layer. To resolve this issue, Barrio et al propose using redox deposition-precipitation [128].…”

Synthesis and characterization of Rh/MnO 2 -CeO 2 /Al 2 O 3 catalysts for CO-PrOx reaction

“…3 shows the Raman spectra obtained for the synthesized materials. RhCe 50 Al exhibit a main band centered at about 462 cm −1 , which is assigned to Ce F2g mode due to symmetrical stretching of Ce-O vibrational unit in octahedral coordination [34]. It is well known that the position and width of this band depends on several factors, such as phonon confinement, strain, inhomogeneity of the sizes distribution, presence of defects and dopants and variation in phono relaxation with the particles size.…”

“…MnO 2 -CeO 2 oxides have been found to be highly actives for oxidation of light oxygenates compounds [38][39][40][41][42][43][44][45][46]. Venkataswamy et al [47] Additionally, high purity grade ethanol was added as reducing agent [50]. RhCe 50 Al respectively) were also prepared.…”

“…Venkataswamy et al [47] Additionally, high purity grade ethanol was added as reducing agent [50]. RhCe 50 Al respectively) were also prepared. Raman spectra were recorded in a dispersive Horiva Jobin Yvon LabRam HR800 microscope with a He-Ne green laser (532.14 nm) working at 5 mW, and with a 600 g mm −1 grating (0.87 m spot laser).…”