In this paper, an infrared study has been performed on CO2 adsorption over polyethylenimine (PEI) functionalized protonated titanate nanotubes (PTNTs) prepared by a simple wet impregnation method. It was found that PTNTs had a large amount of acidity sites, which had strong interaction with the amino groups of the loaded PEI. This interaction could lead to good dispersion of PEI molecules, resulting in good performance in adsorption capacity, amine efficiency and adsorption kinetics. Both weakly and strongly adsorbed CO2 species formed under CO2 exposure, which were attributed to hydrogen-bonded species and carbamate groups, respectively. The existence of strong surface acidity increased the proportion of weakly adsorbed CO2 on the protonated amine species, which was beneficial to the adsorption–desorption cyclic performance. Furthermore, it was confirmed that the interaction between the support surface and amine also resulted in the superior thermal stability of amine-modified sorbents. Overall, our results suggested that suitably tuning surface acidity of the support could effectively facilitate CO2 adsorption.
Manganese-rich MnSAPO-34 molecular sieves were prepared by one-pot synthesis method for NO
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abatement using the ammonia-selective catalytic reduction (NH 3 -SCR) technology and characterized using ICP, BET, XRD, FE-SEM, H 2 -TPR, NH 3 -TPD, XPS, and DR UV-Vis analyses. The experimental results indicate that the Mn content and chemical state, as well as the surface acidity, of the MnSAPO-34 molecular sieves significantly enhance their DeNO
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efficiency at low temperatures (ca. 200–300 °C). The manganese-rich MnSAPO-34 was synthesized using a combination of triethylamine and diisopropylamine as the structural directing agents and high Mn loading ( n (MnO)/ n (P 2 O 5 ) = 0.4). The resulting catalyst exhibits the highest activity among all of the samples with a NO
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conversion value of nearly 95% and a N 2 selectivity that is higher than 90% at 220–400 °C. In addition, this catalyst presents higher NO
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conversion than the conventional V 2 O 5 -WO 3 /TiO 2 catalysts and other SAPO-based catalysts below 300 °C. Furthermore, the analytical results indicate that the manganese species in the catalyst are mainly in the form of a framework Mn(IV), which could play a significant role in the NH 3 -SCR process as the specific active species. The results suggest that controlling the types and content of the organic amine templates and variations in the surface acidity of the catalysts may significantly enhance the SCR activity at lower temperatures.
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