Adsorption and Decomposition of NOx on Heteropolyacids: An Evaluation of the Adsorption Performance

Abstract

In order to develop an efficient method by which to eliminate NOx pollution, several new catalyst systems including different heteropolyacids (HPAs) and supported phosphotungstic acids (HPWs) (HPW/SiO2, HPW/SnO2, HPW/USY and HPW/ZSM-5) for adsorption-decomposition of NOx were prepared and studied. The obtained catalysts were characterized using Brunauer-Emmett-Teller (BET) measurement and Fourier transform infrared (FT-IR) analysis. The results showed that W-containing HPAs were superior to Mo-containing HPAs. Among the selected catalysts, HPW/SnO2 with a 50% HPW loading had the highest NOx adsorption rate of 77.3%, for which the amount of saturated NOx adsorption (85.4 mg g–1) was much higher than that of HPW (50.5 mg g–1). The NOx adsorption performance of the catalyst was mainly determined by the interaction between the support and the HPW, which was also affected by the specific surface area of the catalyst. FTIR characterization revealed that the adsorbed NOx mainly existed in the HPW bulk phase in the form of NOH+. A gas chromatograph-mass spectrometer (GC-MS) was used to confirm the effectiveness of NOx decomposition into N2.