ย Journal of Materials Chemistry A
07 April 2021, Issue 13,ย
Page 7993 to 8816ย
NOx reduction consequences of lanthanide-substituted vanadates functionalized with S or P poisons under oxidative environments
Rare-earth metal vanadates (RMVO4) typically possess an iso-structural tetragonal architecture but vary in terms of their Lewis acidic (LA) properties, which depend on the nature of the RM element. This study pioneers the exploitation of the LA sites inherent to RMVO4 on a TiO2 support as grafting points to immobilize HSOAโ/SOA2โ/H3โBPO4Bโ species, which are notorious poisons of LA sites during the selective catalytic reduction of NOx with NH3 (SCR). The HSOAโ/SOA2โ (S) and H3โBPO4Bโ (P) species served as Brรถnsted acidic (BA) sites with distinct distributions and modulated the redox cycling characteristics of the resulting RM-S/RM-P catalysts. The SCR performance of Ce-S/Ce-P and the other catalysts was dictated by the redox sites and amount of BA sites, respectively, at โค300โ340 ยฐC, while exhibiting โMโ-shaped periodicity in a plot of SCR performance versus the type of RM. This periodicity was maintained at โฅ300โ340 ยฐC, although the catalyst performance was primarily dictated by the redox sites. With the exception of Ce-S/Ce-P, the RM-P catalysts outperformed the corresponding RM-S analogues in accelerating the SCR at โค300โ340 ยฐC, whereas the opposite trend was observed at โฅ300โ340 ยฐC. Furthermore, Gd-S consumed NOx and NH3via diverse pathways of NH4NO3 formation/transformation other than the SCR and production of ammonium sulfate (AS)/ammonium bisulfate (ABS) poisons, thus tolerating AS/ABS poisons in the most efficient manner at 250 ยฐC. This study demonstrates the importance of the RM in HSOAโ/SOA2โ/H3โBPO4Bโ-modified RMVO4 frameworks, whose properties on the BA and redox site and SCR performance varied markedly with the choice of RM.
- Hyo Jin An
- Dong Ho Kim
- Heon Phil Ha
- Jongsik Kim
https://pubs.rsc.org/en/journals/journalissues/ta#!issueid=ta009013&type=current&issnprint=2050-7488
Image created by minjeong Kim / Nanosphere
ย Journal of Materials Chemistry A
07 April 2021, Issue 13,ย
Page 7993 to 8816ย
NOx reduction consequences of lanthanide-substituted vanadates functionalized with S or P poisons under oxidative environments
Rare-earth metal vanadates (RMVO4) typically possess an iso-structural tetragonal architecture but vary in terms of their Lewis acidic (LA) properties, which depend on the nature of the RM element. This study pioneers the exploitation of the LA sites inherent to RMVO4 on a TiO2 support as grafting points to immobilize HSOAโ/SOA2โ/H3โBPO4Bโ species, which are notorious poisons of LA sites during the selective catalytic reduction of NOx with NH3 (SCR). The HSOAโ/SOA2โ (S) and H3โBPO4Bโ (P) species served as Brรถnsted acidic (BA) sites with distinct distributions and modulated the redox cycling characteristics of the resulting RM-S/RM-P catalysts. The SCR performance of Ce-S/Ce-P and the other catalysts was dictated by the redox sites and amount of BA sites, respectively, at โค300โ340 ยฐC, while exhibiting โMโ-shaped periodicity in a plot of SCR performance versus the type of RM. This periodicity was maintained at โฅ300โ340 ยฐC, although the catalyst performance was primarily dictated by the redox sites. With the exception of Ce-S/Ce-P, the RM-P catalysts outperformed the corresponding RM-S analogues in accelerating the SCR at โค300โ340 ยฐC, whereas the opposite trend was observed at โฅ300โ340 ยฐC. Furthermore, Gd-S consumed NOx and NH3via diverse pathways of NH4NO3 formation/transformation other than the SCR and production of ammonium sulfate (AS)/ammonium bisulfate (ABS) poisons, thus tolerating AS/ABS poisons in the most efficient manner at 250 ยฐC. This study demonstrates the importance of the RM in HSOAโ/SOA2โ/H3โBPO4Bโ-modified RMVO4 frameworks, whose properties on the BA and redox site and SCR performance varied markedly with the choice of RM.
https://pubs.rsc.org/en/journals/journalissues/ta#!issueid=ta009013&type=current&issnprint=2050-7488
Image created by minjeong Kim / Nanosphere