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Highlights • The SCR reaction occurred within a thin layer (ca. 0.2 mm) in the wall near the catalyst channel. • The SO 2 oxidation occurred in the entire catalyst wall. • The effects of the operating parameters were investigated synthetically. • A strategy for catalyst design, i.e., applying thin-walled design was proposed. Abstract A three-dimensional model that combined the selective catalytic reduction (SCR) of NO with ammonia and SO 2 oxidation reactions over monolith honeycomb catalyst was established to study the effects of catalyst structure and operating parameters on NO reduction and SO 2 oxidation. The model was to proved to be valid by experimental data. Simulation results showed that the SCR reaction only took place within a thin layer (ca. 0.2 mm) of the catalyst wall surface, whereas SO 3 generated via SO 2 oxidation accumulated throughout the entire wall. The effects of typical operating parameters, i.e., space velocity, temperature, feed concentrations of NO, NH 3 and SO 2 were studied. Temperature and gas velocity were found to be the major influencing factors on SO 2 oxidation. A strategy for monolith catalyst struction optimization, i.e., using thin-walled catalyst was proposed on the basis of these results. [ABSTRACT FROM AUTHOR]

[Display omitted] • The competition adsorption mechanism of NH 3 and CB at low temperature is revealed. • Byproduct of NH 3 -SCO promotes deep oxidation of intermediates in CBCO reaction. • The forms of N and Cl species in simultaneous catalytic oxidation are unveiled. As the emission limits for NO x become further stringent, development of a synergistic control technology to prevent emissions of slipped ammonia (NH 3) and chlorinated organics from steel production and waste incineration is both a prospect and a challenge for the environmental issues. In this work, the designed ruthenium-based catalyst (RuNb/ST) showed the excellent chlorobenzene (CB)/NH 3 synergistic removal performance and N 2 /CO 2 selectivity above 300 ℃. The activity of NH 3 and CB were suppressed at relatively low temperature due to the competitive adsorption of CB and NH 3. Whereas, there was a significant improvement in the N 2 /CO 2 selectivity at relatively high temperature. The removal mechanism was studied by experiments, in which the accumulation of chlorine species, the role of NO 2 and the oxidation of CB were considerable. In contrast to the carrier, the vast majority of the chloride ions adsorbed onto the active sites after dissociating from CB could be efficiently removed in form of Cl 2 via the Deacon Reaction catalyzed by RuO 2. CB was predominantly converted into CO 2 and H 2 O with a fraction persisting as organics. Partial of organics were attacked by Cl ions to generate organic chlorine-containing by-products. The presence of NO 2 molecule was found to promote the cleavage of the benzene ring within CB, and expedited the carbon migration towards the ultimate product of CO 2 , resulting in a notable reduction of byproducts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel catalysts for CVOCs removal present excellent low-temperature activity and high chlorine resistance. • WO x loading affects the surface species morphology while polymer structure at 10% loading shows the best performance. • The RuO 2 -WO x /Sn 0.2 Ti 0.8 O 2 catalysts exhibit highly stable activity in both dry and wet conditions. • Experimental and computational results prove WO 2 Cl 2 to be the main species for tungsten loss on chlorine poisoned catalysts. • The removal performance of CB, TCE and DCM by the cordierite catalyst is validated. The development of catalysts with high activity, selectivity, and durability is crucial for the catalytic oxidation of chlorinated volatile organic compounds (CVOCs). Although acid-modified supports are widely used in catalysis to improve the catalytic activity at low temperature, the acid sites are easily deactivated by Cl poisoning, and the poisoning mechanism remains unclear. Here, a series of RuO 2 -WO x /Sn 0.2 Ti 0.8 O 2 catalysts were synthesized for dichloromethane (DCM) catalytic oxidation. Spectroscopic characterizations revealed that the loading amount of tungsten oxide highly affects the structure of the surface species and, consequently, the low-temperature catalytic activity. SEM, XRD and DFT calculations elucidated that the loss of tungsten species in the form of WO 2 Cl 2 is the main reason for the catalyst deactivation. By loading RuO 2 , the loss of tungsten species could be effectively avoided via the Deacon reaction. The cordierite catalyst exhibits excellent catalytic activity for the oxidation of different types of CVOCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hg0 adsorption with C and S on the FeS surface has been studied via DFT-D2 method. • DOS and ICOHP demonstrated the interaction between the adsorbates and the surfaces. • Carbon can promote mercury physisorption on the pristine FeS(0 0 1)-S surface. • The HgS generation process occurs through Langmuir-Hinshelwood Mechanism. Elemental mercury (Hg0) adsorption behaviors and mechanisms on the low-Miller index mackinawite surface (FeS(0 0 1)-S surface), with the engagement of carbon or sulfur, were investigated via DFT-D2 theoretical calculations. The simulation results show that the most favorable adsorption site for the C and Hg atoms was the lower-S site on the pristine surface, while S atom preferred the upper-S site. C atom could cause charge transfer and inter-atomic charge redistribution during adsorption. The carbon atom performs as a linker to connect the substrate and the Hg atom in the most stable mercury adsorption geometry onto the carbon-doped surface. Hg0 is physically adsorbed over the sulfur-doped surface. The HgS molecule chemically attached to the surface at the upper-S site via the Hg atom to form a S-Hg-S structure, and its generation process follows Langmuir-Hinshelwood Mechanism. Firstly, the Hg and S atoms were pre-adsorbed on the FeS(0 0 1)-S surface. Then the system needed to overcome an activation energy barrier (E b) of 89.82 kJ·mol−1. It was an endothermic process in which two separate atoms generated HgS*. However, C atom will impede the reaction as occupying the adsorption sites of mercury and sulfur. [ABSTRACT FROM AUTHOR]

[Display omitted] • The overall CO 2 mass transfer coefficient decreased under exposure to SO 2. • pH variation of amine solution increased in the presence of SO 2. • The saturated CO 2 capacity largely decreased under exposure to SO 2. • SO 2 greatly weakened the interaction between amine and CO 2. • Modification of overall CO 2 mass transfer coefficient considering the effect of SO 2. Understanding the competitive mechanism in absorption process between SO 2 and CO 2 is essential for simultaneous absorption of SO 2 and CO 2. In this study, the effect of SO 2 on CO 2 absorption using amine solution was studied experimentally and theoretically. The CO 2 absorption rates in MEA/MMEA/MDEA solutions were determined using wetted wall column. Results showed that the reduction of flue gas temperature was beneficial for CO 2 absorption at the typical coal-fired flue gas CO 2 concentration. On this basis, the effect of SO 2 on CO 2 absorption performance was studied. Firstly, the overall CO 2 mass transfer coefficient decreased under exposure to SO 2. Secondly, in the presence of SO 2 , pH variation of amine solution increased. In addition, the saturated CO 2 capacity largely decreased when SO 2 was continuously bubbled into the solution. Furthermore, the quantum chemical calculation showed that CO 2 had little effect on the absorption performance of SO 2 whereas SO 2 greatly weakened the interaction between CO 2 and amines. The overall CO 2 mass transfer coefficient was modified considering the effect of SO 2. The competitive absorption factor, χ, was introduced to modify the CO 2 liquid phase diffusion coefficients. The average deviation of overall CO 2 mass transfer coefficient narrowed to 1.76 % (0.5 mol/L MEA), 1.13 % (1.0 mol/L MEA), 1.88 % (1.0 mol/L MMEA) and 1.43 % (1.0 mol/L MDEA) respectively, which agreed well with the experimental results. [ABSTRACT FROM AUTHOR]

Arsenic (As) is found to be poisonous to the commercial V 2 O 5 WO 3 /TiO 2 catalysts for selective catalytic reduction of NO x with NH 3 . The NO x conversion of catalysts declines and N 2 O formation dominates at high temperature (above 300 °C) after As poisoning. A series of activity and characterization experiments are applied to reveal the deactivation mechanism caused by As. Results indicate that doping of As on the catalysts, which exists as H 2 AsO 4 − and HAsO 4 2− , doesn’t seriously change surface area of catalysts or TiO 2 phase, but greatly decreases both the Lewis and Brønsted acid sites. It is found that V OH is destroyed and less reactive As OH is newly formed. V OH site is crucial to the NH 3 adsorption and its destruction by As contributes to catalyst deactivation. Besides, stronger oxidizability of catalysts that resulted from more surface-active oxygen aroused by As leads to substantial non-selective catalytic reduction reaction and NH 3 oxidation at high temperature. Both of these two aspects result in lower NO x conversion and higher N 2 O formation. However, SO 4 2− can provide remarkable surface acidities and the sites that destroyed by As can thus be supplied. Benefited from these new reactive acid sites, catalysts with prominent SO 4 2− loading show superior arsenic resistance even with a high As content, which indicate to be a promising anti-poisoning formula. Finally, mechanism of arsenic poisoning and resistance effect of SO 4 2− is proposed based on the above analysis. [ABSTRACT FROM AUTHOR]