A mixed catalyst prepared by mechanically milling VW/TiO₂ and low content of Pt/Al₂O₃ for SCO of high-concentration NH₃

Abstract

It is believed that a high-concentration NH3 in exhaust gas requires to be removed with the application of marine NH3-fuel engines in the near future. Herein, a novel mixed catalyst...

Influence of deposition order of dual active components on the NH3-SCO performance of the bimetallic Pt–V system supported on TiO2

“…35 The reduction peak at 755.1 °C could be attributed to the reduction of the TiO 2 support. 27 Two main reduction peaks could be observed in the H 2 -TPR profile of the V 0.5 /TiO 2 catalyst. The primary reduction peak at 426.8 °C could be assigned to the reduction of V 5+ species to V 3+ species, and the reduction peak at 755.1 °C could be attributed to the reduction of the TiO 2 support.…”

“…11. It could be seen that the intensity of the IR bands that could be ascribed to NH 3 species bonded to Lewis acid sites (3382, 3333, 3254, 3152 cm −1 ) and NH 4 + species bonded to Brønsted acid sites (1460, 1415, 1433 cm −1 ) in the in situ DRIFT spectra of the prepared catalysts was obvious lower than that of the TiO 2 support, 27 indicating that the impregnation of Pt and V components might result in the decrease of both Lewis acid sites and Brønsted acid sites. This was in agreement with the NH 3 -TPD results.…”

“…Meanwhile, the intensity of the IR bands of the -NH 2 species (1530, 1563 cm −1 ), NH 4 + species bonded to Brønsted acid sites (1422 cm −1 ), NH 4 NO 3 species (1356 cm −1 ) and bidentate nitrate species (1593, 1379 cm −1 ) increased significantly. 27 This indicated that NH 3 species bonded to Lewis acid sites and coordinated NH 3 species on the surface of the Pt 0.04 /TiO 2 catalyst could react with O 2 to produce –NH 2 species, NH 4 + species, NH 4 NO 3 species and bidentate nitrate species.…”

“…2(a), there were several obvious diffraction peaks in the XRD spectra of the prepared catalysts. The diffraction peaks at 25.2°, 37.1°, 37.8°, 38.8°, 47.9°, 53.9°, 55.0°, 62.9°, 68.9°, 70.2° and 75.0° were ascribed to anatase TiO 2 species (ICDD 21-1276), 27 while the diffraction peaks at 27.5° and 36.0° were attributed to rutile TiO 2 species (ICDD 21-1272). 24 As shown in Fig.…”

“…33 Under the action of O*, the adsorbed NH 3 species could be easily converted to N 2 , N 2 O and NO via eqn (10)–(16). 27 NH 3 + O* → –NH 2 + –OH–NH 2 + O* → –NH + –OH–NH + O* → –HNO–NH + 2O* → –HNO 2 –NHO + –NH → N 2 + H 2 O–NHO + –NHO → N 2 O + H 2 O–HNO 2 → NO + –OHThus, the abundant Pt 0 species on the surface of the V 0.5 /Pt 0.04 /TiO 2 and Pt 0.04 /TiO 2 catalysts were beneficial for them to exhibit excellent NH 3 conversion performance. Moreover, there might be a synergistic effect between the Pt 0 species and V species on the surface of the V 0.5 /Pt 0.04 /TiO 2 catalyst, which was conducive to efficiently oxidizing NH 3 to NO and then reducing NO to N 2 .…”