Controlled synthesis of Cu-based SAPO-18/34 intergrowth zeolites for selective catalytic reduction of NOx by ammonia

Effect of Transition-Metal Oxide M (M = Co, Fe, and Mn) Modification on the Performance and Structure of Porous CuZrCe Catalysts for Simultaneous Removal of NO and Toluene at Low–Medium Temperatures

“…For the CuFeZrCe catalyst, coordinated NH 3 , ionic NH 4 + species, and weakly adsorbed NH 3 decrease quickly after the adsorption of NO + O 2 for 5 min. Moreover, the bands of NO x species including bidentate nitrate (1549 cm –1 ) and ionic nitrate (1414 cm –1 ) appeared and subsequently disappeared after 10 min. , The results indicate that gaseous NO reacted with NH 4 + or NH 3 in acid sites to form NH 4 NO 2 /NH 2 NO 2 , which further decomposed into N 2 and H 2 O. Subsequently, some bands belonging to the surface nitrate species including bridging nitrate species (1602 cm –1 ), linear nitrite (1481 cm –1 ), M–NO nitro compounds (1333 cm –1 ), nitrido compounds (1260 cm –1 ), monodentate nitrate (1105 cm –1 ), bidentate nitrate (1038 cm –1 ), and N 2 O 2 2– (802 cm –1 ) appeared. ,− The peaks at 3740 and 3653 cm –1 may be the N–OH groups corresponding to NO 2 via dimerization, disproportionation, and reaction with H 2 O to generate nitrous acid and nitric acid .…”

“…Moreover, the bands of NO x species including bidentate nitrate (1549 cm −1 ) and ionic nitrate (1414 cm −1 ) appeared and subsequently disappeared after 10 min. 46,50 The results indicate that gaseous NO reacted with NH 4 + or NH 3 in acid sites to form NH 4 NO 2 /NH 2 NO 2 , which further decomposed into N 2 and H 2 O. Subsequently, some bands belonging to the surface nitrate species including bridging nitrate species (1602 cm −1 ), linear nitrite (1481 cm −1 ), M− NO nitro compounds (1333 cm −1 ), nitrido compounds (1260 cm −1 ), monodentate nitrate (1105 cm −1 ), bidentate nitrate (1038 cm −1 ), and N 2 O 2 2− (802 cm −1 ) appeared.…”

Low-Cost CuX Catalyst from Blast Furnace Slag Waste for Low-Temperature NH3-SCR: Nature of Cu Active Sites and Influence of SO2/H2O

“…Several peaks were discovered around g = 2.38, 2.22, and 2.08 in Figure 4d. According to the literature, 9,42,43 the peak at g = 2.38 could be attributed to the active Cu 2+ species, the peak at g = 2.22 was assigned to the hyperfine structure of the 27 Al frame, and the peak at g = 2.08 belonged to the surface O 2− anions. It could be found that the Cu(N)X catalyst had the highest amount of active Cu 2+ species, while the Cu(C)X catalyst had the lowest amount, which was consistent with XPS result in Table S3, resulting in one of the reasons for the higher SCR activity of the Cu(N)X catalyst and the lower SCR activity of the Cu(C)X catalyst, which was also consistent with the catalytic activity results.…”

“…All the catalysts had diffraction peaks at 35.5, 38.9, 48.8, and 61.5°, which were assigned to the CuO phase. 14,26,27 Moreover, the peaks (2θ = 6.8, 15.5, 18.5, 20.2, 23.4, 26.8, and 30.5°) belonged to the structure of zeolite X were observed on Cu(N)X and Cu(N)X−S catalysts, 25,28,29 and the peak intensity of the Cu(N)X catalyst was higher, while there were only two peaks appeared on Cu(S)X and Cu(C)X catalysts, indicating that the structure of zeolite X in Cu(S)X and Cu(C)X catalysts might be destroyed during the ion-exchanged process, but the Cu(N)X catalyst still remained the zeolite X structure, which might be one of the reasons for the excellent SCR activity performance for the Cu(N)X catalyst. The microtopography of Cu(S)X, Cu(N)X, Cu(C)X, and Cu(N)X−S catalysts is described in Figure 3.…”

Synthesis of Hierarchical Porous SAPO-34 and Its Catalytic Activity for 4,6-Dimethyldibenzothiophene

“…Traditional microporous SAPO-34 is favored by researchers because of its high catalytic activity, high selectivity, and good hydrothermal stability in MTO reaction ( Liang, et al, 2021 ). However, traditional SAPO-34 has a small pore size and is prone to carbon deposition and deactivation in catalytic reaction of bulky organic molecules, which cannot meet the needs of the development of the chemical industry ( Zhong et al, 2017 ; Kim et al, 2021 ; Zhang et al, 2021 ). To cope with these shortcomings, several strategies have been developed to improve the diffusion limitation of SAPO-34, such as synthesis of nano-sized mesopore-containing SAPO-34 ( Yang et al, 2014 ; Sun et al, 2018 ; Mi et al, 2021 ).…”