Changhai Li

Low temperature CO catalytic oxidation and kinetic performances of KOH–Hopcalite in the presence of CO2

Catalytic removal of CO from fire smoke is critical to ensure human safety and post-fire atmospheric recovery in typical confined spaces. Copper manganese oxide compounds show promise as highly efficient catalysts for low temperature CO oxidation. However, the CO oxidation activity will be affected when the catalyst is applied in fire smoke containing high-concentration CO2. In this work, a bi-functional catalyst of KOH–Hopcalite is synthesized by impregnation of KOH on Hopcalite (copper manganese oxides mixture) precursor. The catalyst is characterized by N2 adsorption–desorption, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). CO oxidation activity and long-term working stability of the precursor and catalyst in the presence of CO2 are investigated. CO oxidation activity of the precursor would decrease when CO2 is present. KOH modification can mitigate the inhibiting effect of CO2 on CO oxidation activity of the precursor. Reaction mechanisms and kinetic performances of the catalyst in the presence of CO2 are also demonstrated. The catalyst could be potentially utilized as a scavenging agent for post-fire cleanup and atmospheric recovery in confined spaces.

Copper Manganese Oxides Supported on Multi-Walled Carbon Nanotubes as an Efficient Catalyst for Low Temperature CO Oxidation

Multi-walled carbon nanotubes (MWCNTs) with unique properties are finding increasing utility in catalytic applications. In this work, Cu–Mn@MWCNTs (copper manganese oxides supported on MWCNTs) was synthesized as an efficient catalyst for low temperature CO oxidation. The catalyst was characterized by N2 adsorption–desorption, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The CO oxidation activity and long-term working stability of the catalyst were evaluated in 0.1–0.5 % CO and balanced air using a modified fixed-bed reactor. The effects of CO concentration and Cu/Mn molar ratio on the CO oxidation performances were also demonstrated. The increasing CO concentration (0.1–0.5 %) will impair the CO oxidation performances due to the covering of active sites and formation of carbonates and/or hydroxyl species. The increased CO oxidation activity with the changing Cu/Mn molar ratio (1:8–1:1) is ascribed to the improving oxygen utilization in the redox process by increasing Cu content. The synergistic interaction within the Cu–Mn bimetallic catalytic system and the unique properties of the MWCNTs support are also highlighted for the enhanced CO oxidation activity. The catalyst could be considered as a promising option for removing trace CO from typical confined spaces such as space-crafts, submarines and mine refuge chambers.Graphical Abstract

Low-Temperature CO Catalytic Oxidation over KOH-Hopcalite Mixtures and In Situ CO 2 Capture from Fire Smoke

The presence of CO and CO2 in fire smoke is believed as hazardous and is considered as the prime reason for life casualties in evacuation and emergency rescue. It is critically necessary to find new technology options for removing CO and CO2 from fire smoke. In the present work, a novel KOH-Hopcalite catalyst was prepared by impregnating KOH on the commercially available Hopcalite precursor. The CO oxidation and in situ CO2 capture behaviors of the catalyst were tested in simulated fire smoke atmosphere of 0.4 vol.% CO, 1.0 vol.% CO2, and 283–363 K in a fixed-bed reactor. The CO catalytic oxidation activity increased with the increase of temperature, and the CO2 capture performance decreased with temperature increasing. The CO oxidation and CO2 capture capacities of the catalyst in 0.4 vol.% CO+1.0 vol.% CO2 were 0.54 and 0.77 mmol g−1, respectively. With the reaction paths, it was found out that the spillover effect occurred first for CO oxidation, and the in situ CO2 was then chemisorbed by KOH. The reaction kinetics was further investigated with the correlation between the deactivation model and the experimental breakthrough data. The apparent activation energies for the CO oxidation and CO2 capture processes were 15.95 and 12.39 kJ mol−1, respectively. The catalyst showed considerable CO catalytic oxidation and in situ CO2 capture performance at low temperature. Therefore, it can be considered as a novel agent in respiratory protection system for evacuation and emergency rescue in fire smoke or as a scavenging sorbent for post-fire cleanup in confined spaces.

Reaction characteristics of KOH-modified copper manganese oxides catalysts for low-temperature CO oxidation in the presence of CO2

Binary copper manganese oxides catalysts supported on different activated carbons were prepared using the co-precipitation and high-pressure impregnation methods. The catalysts were further modified by KOH to mitigate the adverse effect of CO2 on their CO oxidation performances. The as-synthesized catalysts were characterized by N2 adsorption–desorption, X-ray diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. The effects of support and synthesis method, CO concentration, CO2 concentration, gas hourly space velocity (GHSV), and particle size on CO oxidation performances of the catalysts were investigated. The nature of the different activated carbon supports showed no significant effect on their CO oxidation performances. By contrast, the high-pressure impregnation method was conducive to more effective loading and uniform dispersion of the active components on the support and therefore to benefit the catalyst enhanced CO oxidation performances. Under the given experimental conditions, CO oxidation conversion decreased with the increase of CO concentration, CO2 concentration, GHSV, and particle diameter.