H2O Resistance Research Articles

Catalytic Ozonation of Formaldehyde with an Oxygen-Vacancy-Rich MnOx/γ-Al2O3 Catalyst at Room Temperature

Formaldehyde (HCHO) is known as one of the important indoor organic pollutants. How to remove and decompose the low concentration of formaldehyde at room temperature is important for indoor environments. Catalytic ozonation is an efficient method to thoroughly remove HCHO at room temperature, with high efficiency and few byproducts. A series of MnOx/γ-Al2O3 catalysts were prepared in this work via the impregnation method and treated with different reagents (acid, alkali, and H2O2) to evaluate their catalytic activity for HCHO removal. The results showed that MnAl-II (acid treatment) performed well in activity tests, reaching a nearly 100% HCHO conversion at an O3/HCHO of 2.0 and attaining a CO2 selectivity of above 95% at an O3/HCHO of 3.0 at 30 °C, with almost no ozone residual existing. The larger specific surface area, abundant oxygen vacancies, and higher number of acid sites contributed to the excellent performance of MnAl-II. Stability and H2O resistance tests of MnAl-II were also conducted. To reveal the intermediate product formation and further investigate the reaction mechanism of HCHO ozonation, in-situ DRIFTS measurement was carried out combined with DFT calculations.

Insight into NH3-SCR and H2O/SO2 resistance of Ce modified iron-based catalysts with the presence of arsenic

The mechanism of denitrification and arsenic poisoning during the selective catalytic reduction of NOx with ammonia using a cerium-modified iron-based catalyst was investigated through fixed bed activity tests and catalyst characterization. The results demonstrated that cerium formed a solid solution with Fe, and enriched the surface acid sites of the catalyst. Furthermore, cerium inhibited the arsenic-iron interaction, thereby protecting the active sites of the catalyst. After 6 h of arsenic poisoning, the NOx conversion of 0.1Ce catalyst decreased by only about 30 % of that of Fe2O3 catalyst. The cerium-modified iron-based catalyst exhibited significantly better H2O resistance than the Fe2O3 catalyst at 300 °C, and increased as the temperature rose·H2O adsorbed onto the Lewis acid sites on the catalyst surface, converting them into Brønsted acid sites, which promoted arsenic adsorption and oxidation on the surface, thereby greatly reducing adsorption activity of the catalyst. In the presence of SO2 and As2O3 in the flue gas, the denitrification efficiency of the catalyst further decreased, though the reduction is less pronounced than in the presence of H2O and As2O3 alone, and shows a negative correlation with SO2 concentration.

Architecture of core-shell Ce-OMS-2@CeO2 catalyst and its SCR activity and SO2+H2O tolerance performance at low-temperature

It is a challenge to develop highly sulfur dioxide and water (SO2+H2O) resistance for the low-temperature selective catalytic reduction (SCR) catalysts of nitrogen oxide (NOx) in the non-electric-power industry. In this paper, core-shell and loaded type of Ce-OMS-2 complexes (Ce-OMS-2@CeO2 and CeO2/Ce-OMS-2) were successfully prepared. Their textural properties were characterized and catalytic performance were carried out. The results showed that the core-shell Ce-OMS-2@CeO2 material could maintain the mesoporous structure and significantly improve the mass transfer and adsorption of the reaction gas NO, thus improving the SCR efficiency. On the contrary, for the loaded CeO2/Ce-OMS-2 catalyst, large amounts of CeO2 deposited on the surface of Ce-OMS-2 and blocked the mesoporous structure. Furthermore, SO2 reacted with CeO2/Ce-OMS-2 to form lots of metal sulfate (manganese sulfate or cerium sulfate), which led to the deactivation of the active Mn sites. Therefore, the CeO2/Ce-OMS-2 catalyst exhibited the low SCR activity and poor SO2+H2O tolerance during the SCR reaction. We also clarify the reason for the anti-sulfur of core-shell Ce-OMS-2@CeO2 catalyst. In the presence of SO2 and H2O, SO2 could easily react with NH3 and H2O to produce ammonium bisulfate (NH4HSO4, ABS) on the surface of the Ce-OMS-2 and CeO2/Ce-OMS-2 catalysts. Then ABS can be physically deposited on the surface of the catalysts, thus blocking the active Mn sites to participate in the SCR reaction. Interesting, for the core-shell Ce-OMS-2@CeO2 catalyst, the formed ABS could significantly be decomposed at low temperature, leading to the exposure of surface active Mn sites of the catalyst. Herein, it could maintain the efficient SCR performance over the Ce-OMS-2@CeO2 catalyst. A dynamic balance of ABS formation and decomposition was achieved over Ce-OMS-2@CeO2 even at low temperatures, which hindered the SO2 poisoning during the NH3-SCR reaction. As expected, the core-shell Ce-OMS-2@CeO2 catalyst showed excellent SCR performance and SO2+H2O resistance (~100% NO conversion in the temperature range of 100–200 °C without SO2, ~80% NO conversion for 4 h in the presence of SO2). This work provides an effective strategy for the development of efficient and stable Mn-based low-temperature SCR catalysts.

Enhancement strategies for NH3-SCR performance of MnCeOx nanowire aerogel catalyst: Synergistic modulation of phosphotungstic acid and structure

Improving the low-temperature SO2 and H2O resistance and N2 selectivity of manganese oxide（MnOx） catalysts is a major challenge in achieving industrial applications. This issue can be effectively addressed by using phosphotungstic acid (HPW) modified MnCeOx-N aerogel catalysts. The HPW-MnCeOx-N catalysts demonstrated excellent NOx conversion (∼100 % at 150–400 °C) and N2 selectivity (>90 % at 50–400 °C). Notably, even under challenging conditions such as 250 ppm SO2 at 250 °C, the catalytic activity of HPW-MnCeOx-N remained largely intact. The NOx conversion was still able to be maintained at 95 % even under the influence of 10 vol% H2O. This represents a significant improvement of 14 % and 5 % compared to the unmodified MnOx-N and MnCeOx-N catalysts, respectively. The integration of HPW within the lattice structure of the HPW-MnCeOx-N catalyst results in an increased number of oxygen vacancies and stronger surface acidity. The interaction between HPW and CeO2 promotes the formation of Ce4+-O-W species, which in turn modifies the redox properties of the MnCeOx-N catalyst. This modification leads to a suppression of NH species formation, thereby improving the selectivity towards N2 production. Physicochemical analyses have shown that the presence of HPW alters the reaction pathway of the MnCeOx-N catalyst, increasing the adsorption of NH3 species and significantly enhancing the generation of bidentate nitrate species, thereby facilitating the reaction through the L-H mechanism. On the HPW-MnCeOx-N catalyst, SO2 mainly inhibits the generation of monodentate nitrate and bridged nitrate species, while having little effect on the major active bidentate nitrates.

Low-Temperature NH3-SCR Technology for Industrial Application of Waste Incineration: An Overview of Research Progress

Selective catalytic reduction of nitrogen oxides with NH3 (NH3-SCR) was investigated deeper and deeper with poisoning factors such as H2O, SO2, heavy metals, etc. In order to remove the reheating process before the SCR reactor, the application trend of NH3-SCR technology in the non-power industry is concentrated on the condition of low temperature even ultra-low temperature. The present study summarizes the research process of SO2 and H2O resistance of NH3-SCR catalysts under low temperatures related to the working conditions of municipal solid waste incineration plants. In detail, the effects of a high content of H2O and low concentration of SO2 are reviewed. Other factors such as heavy metals, alkali, or alkaline earth metals in the reaction system, synergistic removal of NOx, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are addressed. Finally, the catalytic performance of assembled monolithic catalysts and pilot-scale experiments are also analyzed for the possibility of industrial application. Hopefully, in view of the questions outlined in this study, valuable insights could be taken into consideration for the development of NH3-SCR in waste incineration.

Enhanced activity and water resistance of SiO2-coated Co/In-SSZ-13 catalysts in the selective catalytic reduction of NOx with CH4

CH4 selective catalytic reduction of NOx (CH4-SCR) is a promising technology to synergistic control of CH4 and NOx emission from LNG-powered vehicles and ships, while its insufficient catalytic activity and H2O resistance are key barriers for application. In this work, SiO2 coated Co3O4/In-SSZ-13 catalysts (Co/In-Z@Si) were prepared to simultaneously improve the CH4-SCR activity and H2O tolerance. The proper Co3O4 introduction enhanced the catalytic performance of the In-SSZ-13, while excessive amount of Co3O4 addition led to more CH4 being oxidized and insufficient CH4 participating in the CH4-SCR reaction. There was a “seesaw effect” between NO oxidation and CH4 oxidation performance of the catalysts. The H2O resistance of the Co/In-Z catalysts significantly enhanced via ultrathin SiO2 coating. The NOx and CH4 conversion maintained 81 % and 90 % in the presence of H2O at 500 °C for the Co/In-Z@Si catalyst, respectively. The in situ DRIFTS confirmed that the SiO2 coating could adsorb H2O molecules, prevent H2O from contacting the active sites, and limit the competitive adsorption between H2O and CH4 on the catalyst. This work provides a good candidate with superior catalytic performance and H2O resistance for removal of NOx and CH4 from LNG-powered vehicles and ships simultaneously.

New insights into improved SO2＆H2O resistance over MoCrCeOx catalyst by CTAB for medium-low temperatures NH3-SCR: Regulation of surface acid and oxygen species

Selective catalytic reduction (NH3-SCR) of NH3 is the most efficient NOx removal technology. Improving the SO2/H2O resistance of SCR catalyst is of great importance for its industrial application. The Mo(0.3)-CrCeOx catalysts synthesized by the citric acid method exhibited excellent high concentration SO2 resistance but poor H2O tolerance. In this work, cetyltrimethylammonium bromide (CTAB) was used to improve SO2＆H2O resistance over Mo(0.3)-CrCeOx catalyst at medium-low temperatures. The mechanism of CTAB modification and the discrepancy to citric acid (CA) method were investigated. The results indicated that the CTAB catalyst had a large specific surface area, and was conducive to forming a specific structural strength. The enhancement of surface acidity of CTAB is the reason for the further enhancement of SCR activity. The regulation of hydroxyl oxygen to promote the activation of Brønsted acid sites is the key factor to SO2＆H2O resistance. In addition, the in-situ DRIFTS results revealed the different mechanisms of the two catalysts. This paper raised the deactivation reason of sol-gel catalyst caused by SO2＆H2O and presented an effective modification strategy.

Effect of Mn or Fe on CrMoOx /TiO2 selective catalytic reduction catalyst

Developing a high-efficiency catalyst with both superior low-temperature activity and good sulfur and water resistance is still challenging for the NH3 selective catalytic reduction (SCR). Herein, a series of Mn- and Fe-doped CrMoOx/TiO2 catalysts were elaborately designed and the Cr3Mo6Mn2/TiO2 catalyst exhibits the best NOx conversion rate, reaching 81. 8 % at 90 ℃ and closing to 100 % at 150 ℃, and the NOx conversion reach ∼71 % at 150 ℃ for 30 h in presence of H2O+SO2. A series of characterization studies revealed that the abundance of Lewis acidic sites on the catalysts and the protective effect of Mo are conducive to the enhancement of SO2+H2O resistance. cr3Mo6Mn2/TiO2 dominates the SCR reaction through the Eley-Rideal (E-R) pathway between adsorbed NH4+/NH3 and gaseous NOx, generating N2 and H2O. This work provides a new strategy for improving the tolerance of chromium-based oxide catalysts to sulfur dioxide and water at low temperatures.

Synthetic Pt-Fe(OH) x catalysts by one-pot method for CO catalytic oxidation.

Catalytic oxidation is used to control carbon monoxide (CO) emissions from industrial exhaust. In this work, The prepared Pta-Fe(OH) x catalysts (x represents the mass fraction of Pt loading (%), a = 0.5, 1 and 2) by the one-pot reduction method exhibited excellent CO catalytic activity, with the Pt2-Fe(OH) x catalyst, 70% and ∼100% CO conversion was achieved at 30°C and 60°C, respectively. In addition, the Pt2-Fe(OH) x catalyst also showed excellent H2O resistance and hydrothermal stability in comparison to the Pt2/Fe(OH) x catalyst prepared by impregnation method. Characterization results showed that the excellent catalytic performance of the catalysts was mainly attributed to the abundant surface oxygen species and Pt0 the presence of H2O, which promoted the catalytic reaction of CO, and Density functional theory (DFT) calculation showed that this was mainly attributed to the catalytic activity of the hydroxyl (-OH) species on Pt2-Fe(OH) x surface, which could easily oxidize CO to -COOH, which could be further decomposed into CO2 and H atoms. This study provides valuable insights into the design of high-efficiency non-precious metal catalysts for CO catalytic oxidation catalysts with high efficiency.

Sb-loaded MnOx/TiO2/CNTs catalysts for selective catalytic reduction of NOx: insight to the SO2 and H2O tolerance

PurposeThis paper aims to synthesize and test Mn-Sb/TiO2-CNT catalysts with different Sb/Mn molar ratios to be used in NH3-SCR reaction.Design/methodology/approachA series of Sb-loaded carbon nanotubes (CNTs)-based Mn/TiO2 catalysts were prepared by the incipient wetness co-impregnation method and tested for the selective catalytic reduction (SCR) of NOx with NH3.FindingsThe Sb-loaded Mn/TiO2-CNTs catalyst outperformed other catalysts and presented the highest activity in the temperature regime of 100–400°C. The catalyst loaded with Sb also showed good SO2 and H2O resistance and exhibited better thermal stability. A stepwise study of SO2 addition evidenced that Mn-Sb/TiO2-CNTs catalyst exhibited better SO2 resistance than the base catalyst Mn/TiO2, where the Sb doping greatly inhibited the sulphating of active phase of the catalyst.Originality/valueIn Sb-loaded catalysts, the formed SOx species fused with SbOx instead of MnOx. This favoured interaction of SO2 with SbOx successfully prevents the MnOx from being sulphated by SO2 which substantially improves the SO2 tolerance of Sb-loaded catalysts.

Engineering binary CrmNb1-mOx (m = 0.1, 0.3, 0.5) oxides catalysts to enhance its NH3-SCR denitration activity and SO2 resistance: Study on the influence of redox property and acidity

It is still a challenge to create novel simply environmentally friendly NH3-SCR denitration catalysts in presence of SO2 and H2O, and to further understand the role of redox property and acidity of catalyst. In this work, a series of binary CrmNb1-mOx (m = 0.1, 0.3 and 0.5) oxides with different Cr/Nb ratio were engineered for NH3-SCR denitration by using the citric acid complex method. Among these catalysts, Cr0.3Nb0.7Ox revealed best catalytic performance with over 90 % NO conversion in the range of 210–390 ℃ and great SO2 and H2O resistance. The effects of different Cr/Nb ratio on catalytic activity was investigated though following characterization such as Raman spectroscopy, Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), N2 physical adsorption, NO-Temperature programmed desorption (NO-TPD), H2-Temperature program reduction (H2-TPR), X-ray photoelectron spectra (XPS), NH3-Temperature programmed desorption (NH3-TPD) and In situ Diffuse reflectance infrared Fourier transform spectroscopy (In situ DRIFTS). The impact of surface redox property and acidity on catalytic performance was further investigated by changing the Cr/Nb ratio. The results suggest that different Cr/Nb ratio result in catalysts having different Brunauer-Emmett-Teller (BET) surface area, and variation of crystal structure, generating the improvement of the surface acid amount and the enhancement of the oxidizing ability due to existence of more surface active oxygen species. Besides, the results of in situ DRIFTS verify that more acid sites are exposed on the Cr0.3Nb0.7Ox surface and react with absorbed NOx even in the existence of SO2, which followed Langmuir-Hinshelwood (L-H) mechanism.

Investigation of long-term anti-sulfur and deactivation mechanism of monolithic Mn-Fe-Ce/Al2O3 catalysts for NH3-SCR: Changes in physicochemical and adsorption properties

Owing to the different reaction properties and deactivation mechanisms caused by the structural discrepancy of monolithic catalysts, abundant scientific results of powder or granular NH3-SCR catalysts have still not sufficiently robustly applied in recent years. Furthermore, minimal research has been focused on monolithic catalysts. As a result, this work prepared monolithic Mn-Fe-Ce/Al2O3 catalysts by active component impregnation (ACI-Mn-Fe-Ce/Al2O3) and precursor impregnation methods (PI-Mn-Fe-Ce/Al2O3) and investigates the long-term SO2 and H2O resistance of the catalysts. Compared with the PI-Mn-Fe-Ce/Al2O3 catalyst, the monolithic ACI-Mn-Fe-Ce/Al2O3 catalyst showed better performance. The catalytic activity follows a bell-shaped curve with an optimal performance at a drug loading of 5 %. The ACI-Mn-Fe-Ce/Al2O3 catalyst exhibits long-term resistance to SO2 and H2O and can still convert more than 70 % NOx after 168 h of SO2 and H2O resistance test. Characterization of the ACI-Mn-Fe-Ce/Al2O3 catalysts before and after the reaction showed that the reducibility decreased after the reaction, and more Mn4+ was transformed into Mn2+ to weaken the catalytic activity. However, more Fe2+ and Ce3+ were generated during the reaction, increasing the number of oxygen vacancies, oxygen defects, and hydroxyl-like groups, all of which would contribute to a certain extent to counteract the passivation effect of SO2 on the catalysts. In situ DRIFTs analysis shows that the formation of surface sulfates has a minimal effect on the adsorption of NO, but it does affect the adsorption of coordinated NH3 on Lewis acid sites. This work elucidates the deactivation details of Mn-Fe-Ce/Al2O3 catalysts from the perspective of physicochemical properties, which provides a reference for the development of better low-temperature SO2-resistance catalysts for industrial applications.

Efficient toluene degradation using Bacillus subtilis biofilm-supported Mn–Ce/zeolite catalysts

This study investigated a new approach for synthesizing Bacillus subtilis biofilm-supported Mn–Ce/zeolite catalysts for the degradation of gaseous toluene. Four different metal oxide nano-catalysts (ZMn, ZMnCe-10%, ZMnCe-20%, and ZMnCe-30%) were synthesized with varying ratios of manganese (Mn) and cerium (Ce) on zeolite nanoparticles. TEM, SEM, XRD, BET, XPS, and EDX mapping were used to examine these four samples, as well as simple zeolite. Based on these analyses, the catalytic activity of the prepared samples ZMn, ZMnCe-10%, ZMnCe-20%, and ZMnCe-30% for the complete oxidation of toluene and toluene intermediate products were tested with Non-thermal plasma (NTP) technology in a dielectric barrier discharge (DBD) reactor. Among all, ZMnCe-20% showed the highest toluene degradation efficiency (89%) at low concentrations (200 ​ppm) and humidity (>50%). Later, highly efficient and hydrophobic nano-biocatalysts were prepared by combining B. subtilis biofilm wild-type (WT) and engineered B. subtilis biofilm EPS with ZMnCe-20% catalyst. EPS is the main component found in biofilm matrix and plays a key role in influencing properties such as biofilm stability, electron transfer, surface roughness and hydrophobicity. Compared to WT B. subtilis biofilm, EPS overexpressed B. subtilis biofilm showed stronger growth and development on ZMnCe-20% nanocatalyst. Moreover, the NTP system packed with ZMnCe-20%/biofilm (EPS+) nano-biocatalyst exhibited the highest toluene degradation activity (99%) with (83%) CO2 selectivity, (up to 50%) reduction in NOx concentration and complete ozone decomposition at (250 ​ppm) toluene concentrations and increased humidity (>90%). High-energy electrons generated in the NTP system break the C–H and C–C bond between the rings of the toluene molecule, forming several byproducts which are later reacted with active radical species such as O, OH, and O3 and further converted into final degradation products (CO2 and H2O). The results demonstrated successful biofilm development and growth on the ZMnCe-20% catalyst with advanced features such as superhydrophobicity, H2O resistance, improved surface roughness, and electron generation. In short, the study's approach combines bioengineering and material science to develop sustainable nano-biocatalysts for removing VOCs in industrial and environmental settings.

Alkali metal modified Pt/EG-TiO2 catalysts for CO oxidation with efficient resistance to SO2 and H2O

Doping 0.15 wt% Na in Pt/EG-TiO2 catalysts could significantly improve the CO oxidation activity and resistance to SO2 and H2O, which provides a new route for the development and industrial applications of the Pt-based catalysts with good SO2 and H2O resistance.

MODIFICATIONS IN SETTING TIMES, MOISTURE RESISTANCE, COMPRESSIVE STRENGTH, AND THERMAL STABILITY OF MAGNESIUM OXYCHLORIDE BY INCORPORATING SHELLAC AS AN ADDITIVE

Magnesium oxychloride cement (MOC) has better cementing properties than ordinary Portland cement (OPC) but it is not largely used in construction work due to its weak moisture tolerance and low early strength at high temperatures. Shellac is a natural resin that works as a very good binder and sealant. It can perform an imperative role in MOC performance. In the present research, different percentages of Shellac (5%, 10%, 15%, and 20%) were mixed with MOC and investigated for their physical and mechanical properties in terms of setting time, moisture ingress, and compressive strength. It was found that 5% Shellac works best for reinforcing the strength and H2O resistance of MOC, while it retards the setting process. The interaction of shellac with MOC, crystalline phases, and thermal stability was also investigated using spectroscopic (FT-IR and Powdered XRD), and thermogravimetric (TGA-DSCDTA) analysis. The outcomes have shown improved mechanical and physical properties with increased thermal stability than simple MOC.

Enhancing strategies for the activity and H2O resistance of MnCo-CMS flexible SCR catalysts and hydrophobic modification by modulating the surface energy

Melamine sponge is a flexible organic rubber-plastic foam characterized by its highly porous three-dimensional mesh structure. By optimizing the carbonization process of the melamine sponge, NH3-SCR catalysts with enhanced flexibility were developed. In this study, MnCo-CMS (Carbonized melamine sponge) catalysts were synthesized using the impregnation method. Response surface methodology (RSM) and central composite design (CCD) were employed to investigate the effects of impregnation time, loading, and calcination temperature on the mass reaction rate and N2 selectivity. The results showed that loading had the most significant influence, followed by calcination temperature and impregnation time. Under the optimal preparation conditions of 32.5 wt% loading, the calcination temperature at 420 °C, and the impregnation time for 342 min, the mass reaction rate could reach 11.02 cm3min-1g−1, and the N2 selectivity could achieve 87.4 %. Experimental validation confirmed that various preparation processes resulted in catalysts with high SCR activity (rate constant k > 9.5 cm3min-1g−1 and N2 selectivity > 80 %). The Mn-Co loading should be within the range of 28–36 wt%, the calcination temperature within the range of 380–420 °C, and the impregnation time should be 150 min or more. Materials with low surface energy could result in excellent hydrophobicity. In this study, it was found that melamine sponges could be modified into low surface energy carbon foams by temperature modulation. The change in surface energy was utilized as a modification approach to enhance the water resistance of the NH3-SCR catalyst. Importantly, the optimized process significantly improved the stability and water resistance of the catalysts.

Mechanistic Insight into the Promotion of the Low-Temperature NH3-SCR Activity over NiMnFeOx LDO Catalysts: A Combined Experimental and DFT Study.

Mn-based catalysts have attracted much attention in the field of the low-temperature NH3 selective catalytic reduction (NH3-SCR) of NO. However, their poor SO2 resistance, low N2 selectivity, and narrow operation window limit the industrial application of Mn-based oxide catalysts. In this work, NiMnFeOx catalysts were prepared by the layered double hydroxide (LDH)-derived oxide method, and the optimized Ni0.5Mn0.5Fe0.5Ox catalyst had the best denitration activity, excellent N2 selectivity, a wider active temperature range (100-250 °C), higher thermal stability, and better H2O and/or SO2 resistance. A transient reaction revealed that Ni0.5Mn0.5Fe0.5Ox inhibited the NH3 + O2 + NOx pathway to generate N2O, which may be the main reason for its improved N2 selectivity. Combining experimental measurements and density functional theory (DFT) calculations, we elucidated at the atomic level that sulfated NiMnFeOx (111) induces the adjustment of the acidity/basicity of up and down spins and the ligand field reconfiguration of the Mn sites, which improves the overall reactivity of NiMnFeOx catalysts. This work provides atomic-level insights into the promotion of NH3-SCR activity by NiMnFeOx composite oxides, which are important for the practical design of future low-temperature SCR technologies.

Self-Constructing 100% Water-Resistant Metal Sulfides through In Situ Acid Etching for Effective Elemental Mercury (Hg0) Capture.

Metal sulfides (MSs) can efficiently entrap thiophilic components, such as elemental mercury (Hg0), and realize environmental remediation. However, there is still a critical problem challenging the extensive application of MSs in related areas, i.e., how to self-regulate their water (H2O) resistance without complexing the sorbent preparation procedure. This work for the first time developed an in situ acid-etching method that self-engineered the water affinity of MSs through changing the interfacial interaction between MSs and Hg0/H2O. The introduction of abundant, undercoordinated sulfur onto the sorbent surface was the primary reason accounting for the significantly improved H2O resistance. The high surface coverage of undercoordinated sulfur induced the formation of polysulfur chains (Sx2-) that stabilized Hg0 via a bridging bond and repelled H2O, attributed to the favorable electron configurations. These properties made the surface of MSs highly hydrophobic and increased the adsorption selectivity toward Hg0 over H2O. The MSs exhibited 100% H2O resistance even in the presence of 20% H2O, which is much higher than the H2O concentration under most practical scenarios. From these perspectives, this work for the first time overcame the detrimental effects of H2O on MSs through a self-regulating way that is scalable and negligibly complexes the sorbent preparation pathway. The highly water-resistant and cost-effective MSs as prepared can serve as efficient Hg0 removal from industrial flue gas in the future.

Sulfur and Water Resistance of Carbon-Based Catalysts for Low-Temperature Selective Catalytic Reduction of NOx: A Review

Low-temperature NH3-SCR is an efficient technology for NOx removal from flue gas. The carbon-based catalyst designed by using porous carbon material with great specific surface area and interconnected pores as the support to load the active components shows excellent NH3-SCR performance and has a broad application prospect. However, overcoming the poor resistance of H2O and SO2 poisoning for carbon-based catalysts remains a great challenge. Notably, reviews on the sulfur and water resistance of carbon-based low-temperature NH3-SCR catalysts have not been previously reported to the best of our knowledge. This review introduces the reaction mechanism of the NH3-SCR process and the poisoning mechanism of SO2 and H2O to carbon-based catalysts. Strategies to improve the SO2 and H2O resistance of carbon-based catalysts in recent years are summarized through the effect of support, modification, structure control, preparation methods and reaction conditions. Perspective for the further development of carbon-based catalysts in NOx low-temperature SCR is proposed. This study provides a new insight and guidance into the design of low-temperature SCR catalysts resistant to SO2 and H2O in the future.

Hierarchical structured Ti-doped CeO2 stabilized CoMn2O4 for enhancing the low-temperature NH3-SCR performance within highly H2O and SO2 resistance

Developing effective and stable catalysts for low-temperature selective catalytic reduction (SCR) of NOx remains challenging. Herein, we constructed a hierarchical structure by loading CoMn2O4 onto Ti-doped CeO2, that CoMn2O4/CeTiOx catalyst has shown superior deNOx activity (>95% at 100–225 °C), prominent reaction activation energy (28.8 ± 0.9 kJ mol−1) and outstanding stability (>75% at 100–200 °C within H2O and SO2). The “low-temperature active sites” and “dual anti-poisoning sites” contribute to excellent activity and stability. Firstly, the hierarchical structure boosts generation of active metal-support interface, which is conducive to oxygen migration (including adsorbed oxygen (Oads), lattice oxygen (Olat) and oxygen vacancy (Ov)) and metal charge transfer (Mn2+/3++Ce4+↔Mn3+/4++Ce3+, Ti4++Ce3+↔Ce4++Ti3+). This is the key to breaking through the limits of catalytic activity stability. Secondly, enhanced surface acidity favors NH3 adsorption and activation, which accelerates -NH2/-NH concatenate with NOx through Eley-Rideal mechanism to generate N2 and H2O. Thirdly, the dual strong SO2 affinity sites by Ti-induced CeO2 crystal reconstruction retard the active center affected by the sulfate species, which contributes to striking stability. This work highlights the importance of design of isolated active sites to improve SO2 and H2O endurance.