Highly selective catalytic reduction of NO via SO2/H2O-tolerant spinel catalysts at low temperature.

Xuanxuan Cai,Chaochao Xu,Wei Sun,Ji Yang,Limei Cao

doi:10.1007/s11356-016-7061-y

Abstract

Selective catalytic reduction of NOX by hydrogen (H2-SCR) in the presence of oxygen has been investigated over the NiCo2O4 and Pd-doped NiCo2O4 catalysts under varying conditions. The catalysts were prepared by a sol-gel method in the presence of oxygen within 50–350 °C and were characterized using XRD, BET, EDS, XPS, Raman, H2-TPR, and NH3-TPD analysis. The results demonstrated that the doped Pd could improve the catalyst reducibility and change the surface acidity and redox properties, resulting in a higher catalytic performance. The performance of NiCo1.95Pd0.05O4 was consistently better than that of NiCo2O4 within the 150–350 °C range at a gas hourly space velocity (GHSV) of 4800 mL g−1 h−1, with a feed stream containing 1070 ppm NO, 10,700 ppm H2, 2 % O2, and N2 as balance gas. The effects of GHSV, NO/H2 ratios, and O2 feed concentration on the NO conversion over the NiCo2O4 and NiCo1.95Pd0.05O4 catalysts were also investigated. The two samples similarly showed that an increase in GHSV from 4800 to 9600 mL h−1 g−1, the NO/H2 ratio from 1:10 to 1:1, and the O2 content from 0 to 6 % would result in a decrease in NO conversion. In addition, 2 %, 5 %, and 8 % H2O into the feed gas had a slightly negative influence on SCR activity over the two catalysts. The effect of SO2 on the SCR activity indicated that the NiCo1.95Pd0.05O4 possesses better SO2 tolerance than NiCo2O4 catalyst does.Graphical abstractThe NiCo1.95Pd0.05O4 catalyst achieved over 90 % NO conversion with N2 selectivity of 100 % in the 200∼250 °C range than the maximum 40.5 % NO conversion over NiCo2O4 with N2 selectivity of approximately 80 % in 350 °C.

Highlights

Nitrogen oxides (NOX), including NO, NO2, N2O, N2O3, N2O4, and N2O5, are mainly derived from fossil fuel combustion (Costa and Efstathiou 2007b)
Rodríguez and Saruhan (2010) reported that the highly active centers could be formed by the interaction sites between Pd and supports and high NOX conversion and N2 selectivities could be achieved by the synergistic effects of palladium and perovskites
We have considered the effects of the gas hourly space velocity (GHSV), NO/H2 ratios, and O2 feed concentration on the SCR activity

Summary

Introduction

Nitrogen oxides (NOX), including NO, NO2, N2O, N2O3, N2O4, and N2O5, are mainly derived from fossil fuel combustion (Costa and Efstathiou 2007b). The catalysts of H2-SCR primarily contain supported noble metal oxides (Jun Yub et al 2003; Yang and Jung 2009), among which the Pt-based and Pd-based catalysts have been revealed to possess good catalytic activity at relatively low temperatures (Chiarello et al 2007; Costa and Efstathiou 2007a; Qing et al 2010; Schott et al 2009). Rodríguez and Saruhan (2010) reported that the highly active centers could be formed by the interaction sites between Pd and supports and high NOX conversion and N2 selectivities could be achieved by the synergistic effects of palladium and perovskites. The Pd-doped nickel cobaltite catalyst was successfully prepared through a sol-gel auto-ignition method and exhibited good catalytic performance for the selective catalytic reduction of NO by H2 in the presence of oxygen at a low temperature. We investigated the durability of the catalyst and its tolerance to SO2 and H2O, respectively

Materials and methods

Results and discussion

Conclusions