Poisoning effect of sulphate on the selective catalytic reduction of NO by C3H6 over Ag-Pd/Al2O3

Abstract

The Ag-Pd/Al 2 O 3 catalyst showed a higher NO x conversion than Ag/Al 2 O 3 in the selective catalytic reduction (SCR) of NO x by C 3 H 6 especially at temperatures ranging from 573 to 773 K. However, the presence of SO 2 in the feed gas decreased the activity of NO x reduction over AgPd/Al 2 O 3 more greatly than that over Ag/Al 2 O 3 . The sulphate species formed on the poisoned Ag-Pd/Al 2 O 3 and Ag/Al 2 O 3 were characterized by BET, inductively couple plasma optical emission spectrometer (ICP-OES), XRD, temperature programmed desorption (TPD) and in situ diffuse reflectance infra-red fourier transform spectroscopy (DRIFTS) methods. Two kinds of sulphate species were found on the SO 2 poisoned AgPd/Al 2 O 3 catalyst, and the formation of nitrate was blocked by the surface sulphate species. The addition of Pd into Ag/Al 2 O 3 promoted the formation of sulphate on the Ag sites in the presence of SO 2 , which was considered to be the possible reason for the weak sulphur resistance of Ag-Pd/Al 2 O 3.

Improved SO2 Tolerance of Cu-SAPO-18 by Ce-Doping in the Selective Catalytic Reduction of NO with NH3

“…Figure 7 shows the DRIFTS spectra of the Cu-SAPO-18 sample that was exposed first to 500 ppm NO in the presence of oxygen at 150 • C and then to 100 ppm SO 2 . When the sample surface was saturated by the adsorption of NO + O 2 , the bands at 1629 and 1575 cm −1 were observed on the in situ DRIFTS spectrum of the Cu-SAPO-18 sample, in which the band at 1629 cm −1 was assigned to the adsorbed bidentate nitrate species [41], whereas the one at 1575 cm −1 was attributed to the bridging nitrate species [34]. When SO 2 was introduced to the system, the characteristic band at 1575 cm −1 attributed to the nitrate species at the copper sites disappeared with time extension, and the characteristic bands at 1644 cm −1 due to the adsorption of SO 2 on the hydroxyl groups [26] and at 1375 cm −1 assigned to weak adsorption of sulfate species [42] increased in intensity.…”

“…The isolated Cu 2+ with a positive charge could form the Lewis acid on the sample surface, which was easy to combine with SO 2 in the gas phase, and translated into the sulfates and/or sulfites in the presence of gas-phase oxygen molecules [14]. It has been reported that conversion of SO 2 to SO 3 could result in a much higher reaction rate over the copper-containing catalysts [41]. Since Cu 2+ species in the cage of Cu-SAPO-18 exist in an isolated environment, they could interact with the sulfate and/or sulfite species to form cupric sulfates and/or sulfites at the original positions of the catalyst.…”

Influence of Fe‐modified Mn–Ce–Fe–Co–Ox/P84 catalytic filter materials for low‐temperature NO removal synergistic Hg0oxidation

“…The reason may be is that H 2 O can absorb free SO 3 in flue gas to form densely distributed H 2 SO 4 molecules, which hinders the adsorption conversion of gas‐phase NH 3 , NO x , and Hg 0 molecules, while more easily reacting to form sulfates, such as (NH 4 ) 2 SO 4 17 . Simultaneously, SO 2 reacts with metal oxides, such as MnO x , CeO 2 , and other reactive phases to form Mn(SO 4 ) 2 and Ce 2 (SO 4 ) 3 , which decreases the content of active components on the catalyst surface and are continuously deposited on the catalytic filter material surface 18 …”

SO2 promoted alkali metal doped Ag/Al2O3 catalysts for CH4-SCR of NOx

“…The patterns for alumina reflect the amorphous or poor crystalline nature of samples. In most of the literature, the formation of Ag 2 (SO 4 ) 3 and Al 2 (SO 4 ) 3 type compounds were identified over Ag-alumina systems in the presence of SO 2 [1,8,20,28]. It is also accounted that the presence of SO 2 usually suppresses the catalytic activity by forming such species.…”