Effective Way to Control the Performance of a Ceria-Based DeNO_x Catalyst with Improved Alkali Resistance: Acid–Base Adjusting

Abstract

Compared with V 2 O 5 −WO 3 /TiO 2 , the ceria catalyst supported on sulfated zirconia (referred to as CeSZ) shows a superior alkali resistance for selective catalytic reduction of NO in flue gases. It reveals an unexpected result that a moderate amount of potassium (normally considered as SCR poisons) could even enhance the activity of CeSZ catalyst. To investigate this exceptional phenomenon, we studied the surface acid−base properties of CeSZ catalysts with different amounts of K and their influences on SCR performances. Although K resulted in a sharp decrease in Brønsted acid sites, the total acidity, especially strong acidity, barely changed when K/Ce was less than 0.4. It was proposed that a small amount of potassium could initially alter some Brønsted acid sites to Lewis ones, therefore retaining the majority of total acidity. Moreover, increased surface basicity due to K depositing led to an enhancement in NO chemisorption and oxidation, which is beneficial to the SCR process via the reaction of NO 2 and NO x ad-species with adsorbed NH 3 species. This explains why the SCR catalytic activity was improved at lower temperature for CeSZ catalysts after K depositing. Therefore, the catalytic activity and reaction temperature window of CeSZ catalyst could be controlled by simply tuning the surface acid/base sites, which may give some inspiration to improve the catalytic activity and poisoning tolerance.

Oxidative Esterification of Methacrolein to Methyl Methacrylate over Gold Nanoparticles on Hydroxyapatite

“…To determine the surface acidity, in situ FTIR spectra of pyridine adsorbed on the supported Au samples were measured (Figure ). In each case, a strong band at approximately =1454 cm −1 is assigned to the vibration of pyridine adsorbed on Lewis acidic sites associated with metal Ca 2+ ions, whereas a weak band at =1545 cm −1 is assigned to the vibration mode of pyridine adsorbed on Brønsted acidic sites related to the POH group in the HAP structure . An observable small shoulder band at =1609 cm −1 is probably associated with pyridine adsorbed on strong Lewis acidic sites .…”

A highly active K/Cu-Mn-O catalyst for the removal of nitric oxide in indoor air

“…Subsequently, these samples were heated at a rate of 5℃/min to 375℃ in feed gas (0.53 ppm of NO), and the total flow rate was 3.9 × 10 −2 m 3 /h, which corresponded to GHSV of 161,200 h −1 . 33 With a balance of total NO between the inlet and the outlet gases, NO conversion was obtained by equation (1), 14 as follows where the [NO] in and [NO] out indicate the inlet and outlet concentration at steady state, respectively. The effluent gases were detected online by a chemiluminescent NO x analyser (42i, Thermo Fisher Scientific Co. Ltd., USA).…”

Perovskite LaFeO3-SrTiO3 composite for synergistically enhanced NO removal under visible light excitation

“…During the past few decades, various de-NO x techniques have been developed in order to combat with the environmental issues, such as acid rain, photochemical smog and heavy haze that are associated with nitrogen oxide (NO x ) emissions [1][2][3]. Among them, selective catalytic reduction and three way catalysis are demonstrated to be the most effective abatement approaches for exhaust gases from industrial power plants and mobile vehicles, respectively [4,5].Though considerable reduction has been achieved by these techniques, with the rapid industrialization and urbanization in developing countries, the NO x pollutants continue to accumulate in the atmosphere, causing the frequent occurrence of heavy haze events. Recently, photocatalysis has offered an appealing way to remedy NO x pollution at ppb-ppm level in surrounding air, due to the advantages of using abundant solar energy and ambient working conditions [6,7].…”