MnOx Supported on Hierarchical SAPO-34 for the Low-Temperature Selective Catalytic Reduction of NO with NH3: Catalytic Activity and SO2 Resistance

Lusha Zhou,Jinkun Guan,Chenglong Yu,Bichun Huang

doi:10.3390/catal11030314

Abstract

The ethanol dispersion method was employed to synthesize a series of MnOx/SAPO-34 catalysts using SAPO-34 with the hierarchical pore structure as the zeolite carrier, which were prepared by facile acid treatment with citric acid. Physicochemical properties of catalysts were characterized by XRD, XPS, BET, TEM, NH3-TPD, SEM, FT-IR, Py-IR, H2-TRP and TG/DTG. NH3-SCR performances of the hierarchical MnOx/SAPO-34 catalysts were evaluated at low temperatures. Results show that citric acid etching solution at a concentration of 0.1 mol/L yielded a hierarchical MnOx/SAPO-34-0.1 catalyst with ca.15 wt.% Mn loading, exhibiting optimal catalytic activity and SO2 tolerance at low temperatures. Almost 100% NO conversion and over 90% N2 selectivity at 120 °C under a gas hourly space velocity (GHSV) of 40,000 h−1 could be obtained over this sample. Furthermore, the NO conversion was still higher than 65% when 100 ppm SO2 was introduced to the reaction gas for 4 h. These could be primarily attributed to the large specific surface area, high surface acidity concentration and abundant chemisorbed oxygen species provided by the hierarchical pore structure, which could also increase the mass transfer of the reaction gas. This finding suggests that the NH3-SCR activity and SO2 poisoning tolerance of hierarchical MnOx/SAPO-34 catalysts at low temperatures can be improved by controlling the morphology of the catalysts, which might supply a rational strategy for the design and synthesis of Mn-based SCR catalysts.

Highlights

Nitrogen oxides (NOx ), which are released from stationary and automobile exhausts, are major atmospheric pollutants that result in many environmental issues, such as haze, acid rain and photochemical smog [1]
It was found that the hierarchical pore structure improved the low-temperature activity and SO2 resistance of the MnOx /SAPO-34 catalyst
MnOx /H-SAPO-34-0.1 presented the optimal selective catalytic reduction (SCR) performance with more than 90% NO

Summary

Introduction

Nitrogen oxides (NOx ), which are released from stationary and automobile exhausts, are major atmospheric pollutants that result in many environmental issues, such as haze, acid rain and photochemical smog [1]. The best developed and most efficient flue gas cleaning technology for NOx abatement from stationary sources is the selective catalytic reduction (SCR) of NOx with ammonia [2,3,4]. Owing to their high efficiency in eliminating NOx , V2 O5 -WO3 /TiO2 catalysts have been used commercially as an NH3 -SCR catalyst. Manganese-containing catalysts exhibit desirable catalytic activities at low temperatures, which received much attention in recent years [7,8,9,10,11]. Fabricating Mn-based catalysts with both excellent catalytic activity and low SO2 sensitivity at low temperatures has attracted great interest in recent years

Methods

Results

Conclusion