Controlled synthesis of bimetallic Nb-Fe composite oxides with high thermal stability for catalytic degradation of binary VOCs pollutants

Abstract

A string of niobium-iron composite oxides with varying Nb/Fe ratios and calcination temperatures were produced and utilized to remove mixed contaminants (500 ppmv chlorobenzene and 500 ppmv toluene in air), and the structure/texture of catalytic materials were systematically characterized. The findings of the structure-performance study revealed that the physicochemical qualities of Nb2O5-Fe2O3 were greatly enhanced than pure metal oxide. The presence of iron oxide hindered the crystallization of niobium oxide, which aided in the uniform dispersion of niobium-iron components into each other. Forming FeNbO4 at Nb/Fe molar ratio of 1/2 effectively improved the thermal stability of catalyst, withstood short-time thermal shock below 850 °C. The formation of niobium-iron composite oxides improved the specific surface area, optimized the pore size distribution, increased surface acid centers, enhanced reduction/oxidation cycle, and promoted metal-metal interaction for the Nb-Fe-O catalysts. At 320 °C, the catalytic degradation efficiency of 1Nb2Fe-500 could approach 90% for chlorobenzene and 85% for toluene, and it could sustain this efficiency for at least 80 h without evident deactivation, with a high CO2 selectivity of 86%. Furthermore, the Nb-Fe-O catalysts met the environmentally benign and low-cost requirements for environmental catalysis.