Self-Defense Effects of Ti-Modified Attapulgite for Alkali-Resistant NO_x Catalytic Reduction

Abstract

Nowadays, the serious deactivation of deNO x catalysts caused by alkali metal poisoning was still a huge bottleneck in the practical application of selective catalytic reduction of NO x with NH3. Herein, alkali-resistant NO x catalytic reduction over metal oxide catalysts using Ti-modified attapulgite (ATP) as supports has been originally demonstrated. The self-defense effects of Ti-modified ATP for alkali-resistant NO x catalytic reduction have been clarified. Ti-modified ATP with self-defense ability was obtained by removing alkaline metal cation impurities in the natural ATP materials without destroying its initial layered-chain structure through the ion-exchange procedure, accompanied with an obvious enrichment of Brønsted acid and Lewis acid sites. The self-defense effects embodied that both ion-exchanged Ti octahedral centers and abundant Si–OH sites in the Ti-ion-exchange-modified ATP could effectively anchor alkali metals via coordinate bonding or ion-exchange process, which induced alkali metals to be immobilized by the Ti-ion-exchange-modified ATP carrier rather than impair active species. Under this special protection of self-defense effects, Ti-ion-exchange-modified ATP supported catalysts still retained plentiful acidic sites and superior redox ability even after alkali metal poisoning, giving rise to the maintenance of sufficient NH x and NO x adsorption and the subsequent efficient reaction, which in turn resulted in high NO x catalytic reduction capacity of the catalyst. The strategy provided new inspiration for the development of novel and efficient selective catalytic reduction of NO x with NH3 (NH3-SCR) catalysts with high alkali resistance.

Compensation or Aggravation: Pb and SO2 Copoisoning Effects over Ceria-Based Catalysts for NOx Reduction

“…Additionally, O 1s XPS spectra in Figure C were divided into two main feature peaks, namely chemisorbed oxygen (O α ) and lattice oxygen (O β ) . Since O α commonly migrated easily in the redox reaction and always considered as active oxygen species, ratios of O α /(O α + O β ) (F­(O α )) were also calculated based on the divided O 1s XPS spectra. The initial proportion of O α among CT was 20.36%, with it dropping significantly to 15.54% for Pb-CT, which resulted from the binding of Pb to CeO 2 that greatly reduced active oxygen species on the surface.…”

“…Additionally, O 1s XPS spectra in Figure 2C were divided into two main feature peaks, namely chemisorbed oxygen (O α ) and lattice oxygen (O β ). 21 Since O α commonly migrated easily in the redox reaction and always considered as active oxygen species, 22…”

NOx Reduction over Smart Catalysts with Self-Created Targeted Antipoisoning Sites

“…NH 3 temperature-programmed desorption mass spectra (NH 3 -TPD-MS) were used to study the surface acidity and quantify the acid amount of as-prepared catalysts, with the results demonstrated in Figure A. The MS signals for each catalyst were divided into four peaks, among which the desorption peaks below 200 °C represented weak acid sites, those at 200–400 °C represented medium-strong acid sites, and those above 400 °C represented strong acid sites. , It was observed that four NH 3 desorption peaks located at 177, 208, 260, and 350 °C emerged in the profile of CeO 2 /MMT-Ti. As for CeO 2 /TiO 2 , similar desorption peaks were also apparent at 180, 212, 267, and 350 °C.…”

Revealing the Promotion Effects of Nb on Alkali Resistance of FeVO4/TiO2 Catalysts for NOx Reduction

“…The development of industry and transportation during past centuries increased significantly the emissions of nitric oxides (NO x ) to the atmosphere [1–3] . NO x causes several pollution issues like haze, ozone, acid rain, among others [4–7] . Nowadays, selective catalytic reduction (SCR) of NO x with ammonia is generally recognized as the most efficient technology for reducing the abatement of NO x [8–10] .…”

“…[1][2][3] NO x causes several pollution issues like haze, ozone, acid rain, among others. [4][5][6][7] Nowadays, selective catalytic reduction (SCR) of NO x with ammonia is generally recognized as the most efficient technology for reducing the abatement of NO x . [8][9][10] The commercial V 2 O 5 -WO 3 / TiO 2 catalysts have widespread application in coal-fired power plants because of the satisfactory SCR activity in temperature of 300-400 °C.…”