Selective catalytic reduction deactivation

Delahay, G., Guzman-Vargas, A. and Coq, B. (2007) Deactivation of a Fe-ZSM-5 catalyst during the selective catalytic reduction of NO by n-decane An operando DRIFT study, Appl. Catal. B Environ., 70, 45. 

Destruction of N20 can be carried out at lower temperatures by adding a reductant. In this case an iron-containing zeolite catalyst is used for the selective catalytic reduction of N20 using hydrocarbons as a reductant. The catalyst did not deactivate in a 2000-hour test under demanding conditions (450°C, 6% H20). Hydrocarbons such as propane (or LPG) and methane (widely available as natural gas) can be used as the reducing agent221. 

In-Sik Nam and Moon Hyeon Kim (Pohang University of Science and Technology, Korea) review new materials for the selective catalytic reduction of NOx from combustion processes. Despite significant research efforts over the last 20 years, there are still unresolved issues, such as inhibition and deactivation by steam. The authors show how new synthesis methods, especially for zeolites, can be used to improve these catalysts. 

Deactivation of Cu-ZSM-5 during Selective Catalytic Reduction of NO by Propane under Wet Conditions... 

The major concern in applying selective catalytic reduction is deactivation or poisoning of the catalyst. One cause of deactivation may be catalyst poisons present in the flue gases. 

The aim of this paper is to understand the influence of zinc on platinum catalytic behaviour. The added metal can either deactivate or provoke an increase in the catalytic activity of platinum either for reforming reactions or depollution reactions respectively, even when the gas atmosphere is always reductive. We shall study the influence -i) of the mode of preparation, -ii) of the zinc loading and -iii) of the kinetic parameters, on the activity of S-[Pt-Zn] catalysts in DeNOx reactions.The catalysts have been characterised by TPR, chemisorption and EXAFS and tested in the reaction of selective catalytic reduction (SCR) using diesel conditions. 

Deactivation Behavior of Selective Catalytic Reduction DeNOj, Catalysts... 

Chen J P, Buzanowski M A, Yang R T, Cichanowicz J E (1990) Deactivation of the Vanadia Catalyst in the Selective Catalytic Reduction Process. J Air Waste Manage Assoc 40 1403-1409... 

Fe-Zeolite Functionality, Durability, and Deactivation Mechanisms in the Selective Catalytic Reduction (SCR) of NOx with Ammonia... 

Trace metal concentrations in herbaceous biomass materials are the final area of concern, particularly with the emphasis on mercury emissions management and the possible concern for selective catalytic reduction catalyst deactivation or poisoning as a result of cofiring straws and other herbaceous biomass fuels [1,17]. The database ftM" herbaceous materials is not extensive. Table 5.10 presents a general range of values. 

Data adapted from Lezcano-Gonzalez I, Deka U, van der Bij HE, Paalanen P, Arstad B, Weckhuysen BM, Beale AM. Chemical deactivation ofCu-SSZ-13 ammonia selective catalytic reduction (NHfSCR) systems. Appl. Catal. B 2014 154-155 339-349. Copyright 2014, with permission of Elsevier. 

Vennestrpm PNR, Janssens TYW, Kustov A, GriU M, Puig-Molina A, Lundegaard LF, et al. Influence of lattice stability on hydrothermal deactivation of Cu-ZSM-5 and Cu-IM-5 zeolites for selective catalytic reduction of NO by NHj. J Catal 2014 309 477-90. 

The use of biomass in fossil fuel based power plants is of increasing interest, since it is considered as a CO2 neutral fuel, having zero human impact on the eaibon release to the atmosphere. Simultaneously, eontinuous efBdent selective catalytic reduction of NO with ammonia (NH3-SCR) remains a very important condition for the implementation of biomass fuel as a sustainable alternative for energy production. However, the NH3-SCR catalyst suffers from a number of deactivation phenomena when installed in boiler units based on biomass combustion, due to exposure to potassium containing fly ash[l]. The active V=0 and V-OH sites on the commercially used V205-W03/Ti02 based catalyst reacts with the potassium salts and form inactive alkali vanadates, which are unable to adsorb ammonia. 

Catalytic reduction of alkynes to ds-alkenes. This reduction is not possible with 10% Pd/C alone because this metal is too reactive and the alkane is formed readily. The selective reaction is possible if the Pd/C is deactivated by either Hg(0) or Pb(0), obtained by reduction of metal acetate with NaBH4. Sodium phosphinate, H2P02Na, is the preferred hydride donor. Since this donor is not soluble in the Organic solvents used, a phase-transfer catalyst, benzyltriethylammonium chloride, is added.3... 

Thus, the selectivities, deactivation mechanisms, and potential transformations of alkoxo and amido intermediates in such reactions are not well understood. It is even rare for transition metal amido and alkoxo complexes to be clearly identified as intermediates in catalytic chemistry. The hydrogenation of imines and ketones presumably involves such intermediates [68], but they have not been clearly detected in these reactions [69]. The catalytic reduction of CO on surfaces may involve alkox-ides, but well-characterized homogeneous analogs are unusual [58]. 

If the reoxidation to M0O3 (Fig. 1) is too slow, further reduction occurs, leading to other suboxides of molybdenum. These are less selective catalytically. Although not proven unequivocally, these suboxides are more difficult to reoxidise in the bulk (especially the ultimate term of the series, Mo40n)- This brings about a deactivation difficult to reverse. As will be mentioned later, the deactivation effect is still more catastrophic in binary oxides (molybdates) than in M0O3. 

Figure 8.33. Comparison between experimental and calculated activity according to eq. 8.120 (K. Liberkova, R. Touroude, D. Yu. Murzin, Analysis of deactivation and selectivity pattern in catalytic reduction of a molecule with different functional groups Crotonaldehyde hydrogenation on Pt/Sn02, Chemical Engineering Science, 57 (2002) 2519).

Reduction of the acid stage to the aldehyde 2S8 or 290 is possible by catalytic hydrogenation of the corresponding a-ketophosphonic esters [615] and subsequent termal [617] or alkaline [618] decomposition of the a-hydroxyphosphonic esters. Another possibility is the selective reduction of the ester with deactivated aluminum-hydrides [619] or catalytic reduction of the acid chloride [620]. On a bench scale, reduction of the bromofluoro benzonitrile with Raney nickel in formic acid [621] is particularly advisable. 

NBR is a high-strength elastomer widely used as an oil-resistant rubber, an adhesion material in coating, and a plastic modifier. Selective catalytic hydrogenation of NBR is difficult for two reasons (i) many metal catalysts can coordinate with the nitrile C=N bonds, thus deactivating the catalytic species, and (ii) some metal catalysts may not preferentially reduce C=C bonds over nitrile C=N bonds. Regardless, both rhodium- and ruthenium-based catalytic systems have shown high activity and selectivity toward C=C bond reduction in NBR, which was studied extensively in a recent review. ... 

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