Removal of VOCs by catalytic process. A study of MnZnO composites synthesized from waste alkaline and Zn/C batteries

Abstract

Spent alkaline and zinc-carbon batteries were subjected to a biohydrometallurgy process, in order to recover manganese and mixed manganese zinc oxides. Two solids were synthesized, one of them prepared by reaction of MnSO4 and KMnO4 (MnOx) and the other obtained by chemical precipitation with NaOH (ZnMnO). The characterization by XRD, TPR, FTIR and XPS revealed the presence of Mn3+ and Mn4+ cations in both samples, and the presence of ZnO and Mn-Zn spinels in ZnMnO. The samples were evaluated in the oxidation reaction of ethanol and toluene. The results in the flow reactor showed that ethanol conversion on both catalysts, MnOx and ZnMnO, is rather similar, but toluene conversion is markedly higher on MnOx, due to a greater Mn/Zn ratio and to the absence of a crystallized ZnO phase. The FTIR study demonstrated that ethanol is oxidized to acetaldehyde at low temperature, and to CO2 and CO at 400 °C. Traces of CH4 in the gas phase are also detected at high temperature. The formation of ethoxy and acetate groups is observed at the catalyst surface. With respect to toluene oxidation, CO2 is detected at 300 °C and when the temperature is increased, CO is also observed in the gas phase. The results showed that: (i) the alkaline and Zn-carbon batteries can be recycled as catalysts and (ii) the solids can be used in the catalytic process for VOCs control

Heterogeneous Catalysis in (Bio)Ethanol Conversion to Chemicals and Fuels: Thermodynamics, Catalysis, Reaction Paths, Mechanisms and Product Selectivities

“…For example, as unsupported K-doped manganese oxides catalyze the complete oxidation of ethanol to CO 2 at 430 K, alumina-supported catalysts with similar compositions allow full combustion at 473-500 K [46]. Poorly active catalysts indeed produce incomplete combustion with some acetaldehyde coproduction [47] by reaction (9), and due to the much higher toxicity of acetaldehyde with respect to ethanol, this needs to be completely avoided.…”

Novel and Sustainable Catalytic Ruthenium-Doped Glass Foam for Thermocatalytic Oxidation of Volatile Organic Compounds: An Experimental and Modeling Study

“…The catalysts used are usually honeycombed structures with parallel channels coated with catalytic species (noble metals or metal oxides) − by different methods such as sol–gel deposition, impregnation, or electrophoretic deposition . Many studies focused on the influence of the catalytic species to the removal of various VOCs such as toluene, , benzene, , formaldehyde, or ethanol . However, these types of fixed bed catalysts suffer from several drawbacks: (i) the cost of some catalytic species and coating and (ii) the diffusional limitations.…”

Recycling Waste Batteries: Recovery of Valuable Resources or Reutilization as Functional Materials

“…Gallegos et al synthesized ZnMnO catalyst from the waste alkaline and Zn–C batteries via a biohydrometallurgy process, for the oxidation reaction of ethanol and toluene . The results showed that the MnOx and ZnMnO catalysts possessed the similar ethanol conversion, whereas the latter one possessed markedly higher toluene conversion, owing to a greater Mn/Zn ratio and the absence of a crystallized ZnO phase.…”