Nanotechnologies / Materials
Exhaust gas treatment, Wastewater treatment

Development of environmental catalysts for effective
decomposition of harmful organic compounds
Department of Applied Chemistry, Graduate School of Engineering
Assistant Professor Naoyoshi Nunotani
https://researchmap.jp/nunotani?lang=en

Nanotechnologies / Materials

Abstract
Novel environmental catalysts have been created to decompose
harmful organic compounds, such as VOCs (e.g. toluene) andphenolic compounds, into non-toxic carbon dioxide and water. In
these catalysts, oxidation was facilitated by the active oxygen supply from the promoter, which were developed from the viewpointof the solid state chemistry field. By using the developed catalyst,
gaseous toluene was completely oxidized at the temperature as
low as 100°C, where a typical catalyst required 170°
C. In theliquid-phase, furthermore, the developed catalyst completely removed phenol under the moderate conditions of the atmosphericopen-air system at 80°C, while typical catalysts needed sever conditions of 10-50 atm at 140-170°C.

production of resin, etc.; however, they have to be removed fromexhaust gas and wastewater due to their harmful effects for humanand the environment. The novel catalysts, created in this study,
showed considerably high activities compared to the typical catalysts. These catalysts are expected to apply the advanced equipment having simple, low-cost, and sustainable system.

▍ Background & Results
To date, several methods have been utilized for the removal of
harmful organic compounds. Among them, the catalytic decomposition is regarded as a sustainable system, because harmful compounds can be catalytically oxidized into non-toxic carbon dioxideand water. However, typical catalysts (e.g. Pt/Al2O3) required hightemperatures and/or high pressures (e.g., 170°C for toluene combustion in gas-phase, and 10-50 atm and 140-170°C for phenol
oxidation in liquid-phase).
Although a general method to obtain high activity is the controlof dispersion and surface area of an activator (Pt, etc.), this study
focuses on the introduction of the promoter, which can supply active oxygen species from inside the lattice toward the activator (Fig.
1). CeO2-ZrO2 solid solution is a famous promoter in automotive
exhaust catalyst; however, it works at elevated temperatures of ca.
800°C. Thus, it is important to develop novel promoters which canoperate at lower temperatures. From the viewpoint of the solid statechemistry field, in this study, NiO was introduced into the CeO2ZrO2 lattice to form the oxide ion vacancy for oxide ion migration.
As a result, the oxygen supply ability successfully improved, andthe Pt/CeO2-ZrO2-NiO/Al2O3 catalyst exhibited the high activity fortoluene combustion compared to the Pt/CeO2-ZrO2/Al2O3 case (Fig.
2). By using Pt/CeO2-ZrO2-NiO/Al2O3, toluene was completely oxidized at the temperature as low as 100°C, which is lower than thetypical catalyst (170°C for complete toluene combustion).
For the liquid-phase oxidation, SnO2 was introduced into theCeO2-ZrO2 lattice, because the Sn ion can hold two kinds of valence states (Sn4+ and Sn2+), resulting in the high oxygen supply
ability. By using CeO2-ZrO2-SnO2 as a promoter, phenol was completely removed under the moderate conditions of the atmosphericopen-air system at 80°C, where the typical catalysts required 1050 atm and 140-170°C.

▍ Significance of the research and Future perspective

Figure 1. Schematic illustration of decomposition of harmful organic compounds
using oxygen supply from the promoter toward the activator.

Figure 2. Temperature dependence of toluene conversion over Pt/CeO2-ZrO2-NiO/
Al2O3 and Pt/CeO2-ZrO2/Al2O3.

Organic compounds including VOCs and phenolic compounds
have been widely used as organic solvents and raw materials forP a t e n t
Jeong, Minchan; Nunotani, Naoyoshi; Imanaka, Nobuhito et al. Introduction of NiO in Pt/CeO2-ZrO2/γ-Al2O3 Catalysts for Removing Toluene in Indoor Air.
Materials Letters. 2017, 208, p. 43-45, doi: 10.1016/j.matlet.2017.05.048
Abdul Rohman Supandi; Nunotani, Naoyoshi; Imanaka, Nobuhito. Complete Phenol Removal in Liquid-phase under Moderate Condition over Pt/CeO2ZrO2-SnO2/ZrO2/SBA-16 Catalysts. Functional Materials Letters. 2020, 13, p. 2050030: 1-4, doi: 10.1142/S1793604720500307
UR
L https://www-chem.eng.osaka-u.ac.jp/~imaken/K e y w o r d environmental catalysts, volatile organic compounds, rare earths
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