Preparation of Mesoporous Mn–Ce–Ti–O Aerogels by a One-Pot Sol–Gel Method for Selective Catalytic Reduction of NO with NH3

Abstract

Novel Mn–Ce–Ti–O composite aerogels with large mesopore size were prepared via a one-pot sol–gel method by using propylene oxide as a network gel inducer and ethyl acetoacetate as a complexing agent. The effect of calcination temperature (400, 500, 600, and 700 °C) on the NH3–selective catalytic reduction (SCR) performance of the obtained Mn–Ce–Ti–O composite aerogels was investigated. The results show that the Mn–Ce–Ti–O catalyst calcined at 600 °C exhibits the highest NH3–SCR activity and lowest apparent activation energy due to its most abundant Lewis acid sites and best reducibility. The NO conversion of the MCTO-600 catalyst maintains 100% at 200 °C in the presence of 100 ppm SO2, showing the superior resistance to SO2 poisoning as compared with the MnOx–CeO2–TiO2 catalysts reported the literature. This should be mainly attributed to its large mesopore sizes with an average pore size of 32 nm and abundant Lewis acid sites. The former fact facilitates the decomposition of NH4HSO4, and the latter fact reduces vapor pressure of NH3. The NH3–SCR process on the MCTO-600 catalyst follows both the Eley–Rideal (E–R) mechanism and the Langmuir–Hinshelwood (L–H) mechanism.

MnFeOx@TiO2 Nanocages for Selective Catalytic Reduction of NO with NH3 at Low Temperature

“…For FeFe@Ti, the diffraction peaks at 25.28, 37.80, 48.05, 53.89, 55.06, 62.69, 68.76, 70.31, 75.03, and 82.66° corresponded to the anatase TiO 2 (PDF # 21-1272) (101), (004), (200), (105), (211), (204), (116), (220), (215), and (224) crystal planes, respectively. , The diffraction peaks at 33.15 and 35.61° were attributed to the (104) and (110) crystal planes of hematite Fe 2 O 3 (PDF #33-0664), respectively. , For the MnFe, the diffraction peaks at 18.84, 23.12, 32.92, 42.92, and 55.14° were ascribed to the (200), (211), (222), (402), and (044) crystal planes of Mn 2 O 3 (PDF #24-0508), respectively. , The diffraction peaks at 35.61 and 62.45° were attributed to the (110) and (214) crystal planes of hematite Fe 2 O 3 (PDF #33-0664), respectively. , It was clear that the MnFe catalyst had a weaker diffraction peak, which indicated that the Mn 2 O 3 and Fe 2 O 3 species had better dispersion properties. For MnFe@Ti, the diffraction peaks at 25.28, 37.80, 48.05, 53.89, 55.06, 62.69, and 75.03° corresponded to anatase TiO 2 (PDF #21-1272) (101), (004), (200), (105), (211), (204) and (215) crystal planes, respectively. , The diffraction peaks at 35.61° were attributed to the (110) crystal planes of hematite Fe 2 O 3 (PDF #33-0664). , The diffraction peaks at 42.92° were ascribed to the (402) crystal plane of Mn 2 O 3 (PDF #24-0508). , The high intensity of the diffraction peaks of anatase TiO 2 and the decrease of the diffraction peaks of the Mn 2 O 3 and Fe 2 O 3 indicated that the Mn 2 O 3 and Fe 2 O 3 species were coated with the TiO 2 shell layer. In addition, as shown in Figure S4, the XRD patterns before and after the MnFe@Ti reaction were compared.…”

“…Three peaks were attributed to Mn 2+ , Mn 3+ , and Mn 4+ , respectively. 37,55 The Mn 2p 1/2 spectrum could be ascribed to 651.93, 653.10, and 654.36 eV. The three peaks were also attributed to Mn 2+ , Mn 3+ , and Mn 4+ , respectively.…”

“…The three peaks were also attributed to Mn 2+ , Mn 3+ , and Mn 4+ , respectively. 37,55 As shown in Table S4, the Mn 4+ /Mn total (Mn 2+ + Mn 3+ + Mn 4+ ) ratios in MnFe and MnFe@Ti were 32.18 and 35.65%, respectively. Obviously, there were more Mn 4+ species in MnFe@Ti.…”

“…35,36 For the MnFe, the diffraction peaks at 18.84, 23.12, 32.92, 42.92, and 55.14°were ascribed to the (200), ( 211), ( 222), (402), and (044) crystal planes of Mn 2 O 3 (PDF #24-0508), respectively. 22,37 The diffraction peaks at 35.61 and 62.45°were attributed to the (110) and (214) crystal planes of hematite Fe 2 O 3 (PDF #33-0664), respectively. 35,36 It was clear that the MnFe catalyst had a weaker diffraction peak, which indicated that the Mn 2 O 3 and Fe 2 O 3 species had better dispersion properties.…”

C,N‐modified TiO2‐supported Mn–Ce–Cox‐based catalyst for low‐temperature NH3‐SCR

“…5(B)(b), we can see that the broad peak at 580 °C can be interpreted as the overlapping of the reduction of the Ti-C,N and Mn 3 O 4 → MnO. 61 Compared with (a), the two reduction peaks of (b) shift to low temperature, which confirms that Ti-C,N promotes the redox ability of Mn-Ce/Ti-C,N. 62 The H 2 -TPR result of Mn-Ce-Co x /Ti-C,N catalysts are shown in Fig.…”