Development of Innovative Structured Catalysts for the Catalytic Decomposition of N2O at Low Temperatures

Abstract

Nitrous oxide (N2O), produced from several human activities, is considered a greenhouse gas with significant environmental impacts. The most promising abatement technology consists of the catalytic decomposition of N2O into nitrogen and oxygen. Many recently published papers dealing with N2O catalytic decomposition over Ni-substituted Co3O4 are related to the treatment of N2O concentrations less than 2 vol% in the feed stream. The present work is focused on developing catalysts active in the presence of a gaseous stream richer in N2O, up to 20 vol%, both as powder and in structured configurations suitable for industrial application. With this aim, different nickel-cobalt mixed oxides (NixCo1−xCo2O4) were prepared, characterized, and tested. Subsequently, since alumina-based slurries assure successful deposition of the catalytic species on the structured carrier, a screening was performed on three nickel-cobalt-alumina mixed oxides. As the latter samples turned out to be excellent catalysts for the N2O decomposition reaction, the final catalytic formulation was transferred to a silicon carbide monolith. The structured catalyst led to the following very promising results: total N2O conversion and selectivity towards N2 and O2 were reached at 510 °C by feeding 20 vol% of N2O. It represents an important achievement in the view of developing a more concretely applicable catalytic system for industrial processes.

NiCoAl-Based Monolithic Catalysts for the N2O Intensified Decomposition: A New Path towards the Microwave-Assisted Catalysis

“…Specifically, in the case of NiCo/Al 2 O 3 /SiC(0), the deposited species consist of a mix of oxides (alumina and Ni-Co mixed oxide), while the NiCoAl/SiC(0) is characterized by the presence of a Ni-Co-Al mixed oxide. The evidence of the differences in the chemical nature of these compounds was deeply described in the previous work [36] after the study of several powder catalyst formulations for the N 2 O decomposition reaction. Figure 7b shows that three and four cycles were necessary to prepare NiCo/Al 2 O 3 /SiC(0) and NiCoAl/SiC(0), respectively, suggesting that the higher stability of the latter could also be attributed to the more gradual deposition of the active phase.…”

“…The test was performed in the temperature range 20-600 °C in the presence of a reducing mixture 5 vol% H2-Ar and with a heating rate of 10 °C/min. Other characterization techniques have been previously used and the details were given in a previous work [36]. After a preliminary study, as the NiCoAl/SiC(0) sample was more promising for the process under investigation, two final structured catalysts, namely NiCoAl/SiC(A) and NiCoAl/SiC(B), were prepared.…”

“…The test was performed in the temperature range 20-600 • C in the presence of a reducing mixture 5 vol% H 2 -Ar and with a heating rate of 10 • C/min. Other characterization techniques have been previously used and the details were given in a previous work [36].…”

“…The heat to the reaction section was supplied by means of an electrical furnace where the reactor was in horizontal position. Further details about the experimental apparatus used for the conventional heating mode tests can be found in our previous work [36]. The microwave-assisted N 2 O decomposition reaction was studied in a laboratory plant that differs essentially from the heat providing system and the reactor configuration.…”

“…The catalytic decomposition of nitrous oxide has been widely studied and it has been found that the transition metal oxides are the most active species, especially cobalt-based mixed oxides [30][31][32][33][34][35]. In our previous work [36], a SiC-based structured catalyst was investigated for the catalytic decomposition of nitrous oxide. The results demonstrated that a catalytic system as performant as the powders can be successfully achieved by depositing a nickel-cobalt-aluminum mixed oxide over a SiC honeycomb monolith.…”