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Selective catalytic reduction
About: Selective catalytic reduction is a research topic. Over the lifetime, 10502 publications have been published within this topic receiving 226291 citations.
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TL;DR: In this article, the selective catalytic reduction of NOx with ammonia (NH3-SCR) has been studied over Cu-CHA catalysts in which the loading of copper species was achieved using three different synthetic routes: two are based on post-synthetic treatment of the zeolite material (via aqueous or vapor phase) and a third involves the direct synthesis of a Cu-loaded SAPO-34.
137 citations
TL;DR: In this article, the results of in situ diffuse reflectance infrared Fourier transform (in situ DRIFT) spectroscopy and temperature programmed desorption (TPD) profiles indicated that the active sites of the Mn-Ce/TiO 2 catalyst were seriously sulfated at 200°C which led to an irreversible deactivation of the sample.
137 citations
TL;DR: In this paper, the first example of Mn(i)-catalysed hydrogenation of CO2 to HCOOH was reported, achieving TONs up to 10,000 and quantitative yields after 24 h using DBU as the base at 80 °C and 80 bar total pressure.
Abstract: The catalytic reduction of carbon dioxide is of great interest for its potential as a hydrogen storage method and to use carbon dioxide as C-1 feedstock. In an effort to replace expensive noble metal-based catalysts with efficient and cheap earth-abundant counterparts, we report the first example of Mn(i)-catalysed hydrogenation of CO2 to HCOOH. The hydride Mn(i) catalyst [Mn(PNPNH-iPr)(H)(CO)2] showed higher stability and activity than its Fe(ii) analogue. TONs up to 10 000 and quantitative yields were obtained after 24 h using DBU as the base at 80 °C and 80 bar total pressure. At catalyst loadings as low as 0.002 mol%, TONs greater than 30 000 could be achieved in the presence of LiOTf as the co-catalyst, which are among the highest activities reported for base-metal catalysed CO2 hydrogenations to date.
137 citations
TL;DR: In this paper, a series of vanadia supported on ceria nanorods are prepared by impregnation method for selective catalytic reduction (SCR) of NO with ammonia.
Abstract: A series of vanadia supported on ceria nanorods are prepared by impregnation method for selective catalytic reduction (SCR) of NO with ammonia. Two kinds of vanadia species (VOx) (oligomeric and polymeric VOx) and CeVO4 are dispersed on the ceria surface according to the vanadium surface density. These species slightly suppress the catalyst reducibility and concentration of surface oxygen defects rather than distort the ceria cubic lattice or enlarge the BET surface areas. Polymeric VOx and CeO2 create the Lewis acid sites and CeVO4 could be served as the Bronsted acid sites. Polymeric VOx provide new active sites compared with pure CeO2 for the SCR reaction and CeVO4 enhance the number of active sites. Moreover, part of the Lewis acid sites might be converted into the Bronsted acid sites at high temperature under the SCR gas flow. According to the investigations of the reaction mechanism, both Lewis and Bronsted acid sites are reactive with gaseous NO. At low temperature, cis-N2O22− and dimer (NO)2 are active, while surface nitrite or nitrate species are active at high temperature.
137 citations
TL;DR: In this article, three most important pillared clays (PILCs) were studied as catalysts for selective catalytic reduction (SCR) of NO by ethylene.
Abstract: Ion-exchanged pillared clays (PILCs) were studied as catalysts for selective catalytic reduction (SCR) of NO by ethylene. Three most important pillared clays, Al 2 O 3 -PILC (or Al-PILC), ZrO 2 -PILC (or Zr-PILC) and TiO 2 -PILC (or Ti-PILC), were synthesized. Cation exchanges were performed to prepare the following catalysts: Cu–Ti-PILC, Cu–Al-PILC, Cu–Zr-PILC, Cu–Al–Laponite, Fe–Ti-PILC, Ce–Ti-PILC, Ce–Ti-PILC, Co–Ti-PILC, Ag–Ti-PILC and Ga–Ti-PILC. Cu–Ti-PILC showed the highest activities at temperatures below 370°C, while Cu–Al-PILC was most active at above 370°C, and both catalysts were substantially more active than Cu-ZSM-5. No detectable N 2 O was formed by all of these catalysts. H 2 O and SO 2 only slightly deactivated the SCR activity of Cu–Ti-PILC, whereas severe deactivation was observed for Cu-ZSM-5. The catalytic activity of Cu–Ti-PILC was found to depend on the method and amount of copper loading. The catalytic activity increased with copper content until it reached 245% ion-exchange. The doping of 0.5 wt% Ce 2 O 3 on Cu–Ti-PILC increased the activities from 10% to 30% while 1.0 wt% of Ce 2 O 3 decreased the activity of Cu–Ti-PILC due to pore plugging. Cu–Ti-PILC was found to be an excellent catalyst for NO SCR by NH 3 , but inactive when CH 4 was used as the reducing agent. Subjecting the Cu–Ti-PILC catalyst to 5% H 2 0 and 50 ppm SO 2 at 700°C for 2 h only slightly decreased its activity. TPR results showed that the overexchanged (245%) PILC sample contained Cu 2+ , Cu + and CuO. The TPR temperatures for the Cu–Ti-PILC were substantially lower than that for Cu-ZSM-5, indicating easier redox on the PILC catalyst and hence higher SCR activity.
136 citations