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The modeling of a mixer used for mixing ammonia and flue gasses is considered. Simulations were performed using Flow Vision 3.14 (TESIS LLC). As a result of the simulation, the distribution of concentrations along the mixer length was obtained at 50%, 65%, 85%, and full flue gas loading. It was found that operations at 100% and 85% gas loads are accompanied by an acceptable distribution of ammonia in the mixer volume (Cov = 0.05). The development and creation of an experimental model in real production was carried out according to the results of the numerical simulation. The simulation results were compared with experimental data on the speed and concentration of ammonia in the control section. The discrepancy, in general, did not exceed 15%. The developed mixer corresponds to modern developments in terms of mixing quality but is simpler in design and more compact. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction by methanol (Methanol-SCR) on FER zeolite is a promising technology for the deNOx treatment of flue gas with a high concentration of sulfur. However, the resistance to alkali metal and sulfate ions is crucial for the practical application of Methanol-SCR catalysts. In this study, we investigated the poisoning mechanism of H-FER zeolite by K+ and sulfate ions. It was observed that K+ ions induce deactivation at high temperatures, whereas the decline at low temperatures (< 320 °C) can be attributed mainly to sulfate ions. Furthermore, surface modification of H-FER zeolite with metal oxide nanoparticles, such as alumina, has proved to be an effective method for improving its potassium sulfate resistance performance by preventing the diffusion of sulfate into zeolite pores. [ABSTRACT FROM AUTHOR]

The low temperature activity of Fe‐loaded zeolites as selective catalytic reduction of NOx by NH3 (NH3‐SCR) catalysts is a critical drawback for practical application. Here, we found unexpected improvement of low temperature activity by our proposed post‐synthetic treatment. An Al‐rich zeolite beta (Si/Al=5) is employed as the catalyst support, and the parent sample is dealuminated for higher hydrothermal stability, followed by the liquid‐mediated stabilization treatment and impregnation. It is found that stabilized samples feature excellent low temperature activity and high N2 selectivity even for a long‐term operation, along with the ability to maintain high NOx conversion after aging. The improved SCR activity should be attributed to abundant acid sites in Al‐rich framework and better stabilization of monomeric iron species after the stabilization treatment. Furthermore, the low yield of side product N2O is probably due to the absence of the generation of NH4NO3 during NH3‐SCR catalyzed by Fe‐loaded zeolites. [ABSTRACT FROM AUTHOR]

The low temperature activity of Fe‐loaded zeolites as selective catalytic reduction of NOx by NH3 (NH3‐SCR) catalysts is a critical drawback for practical application. Here, we found unexpected improvement of low temperature activity by our proposed post‐synthetic treatment. An Al‐rich zeolite beta (Si/Al=5) is employed as the catalyst support, and the parent sample is dealuminated for higher hydrothermal stability, followed by the liquid‐mediated stabilization treatment and impregnation. It is found that stabilized samples feature excellent low temperature activity and high N2 selectivity even for a long‐term operation, along with the ability to maintain high NOx conversion after aging. The improved SCR activity should be attributed to abundant acid sites in Al‐rich framework and better stabilization of monomeric iron species after the stabilization treatment. Furthermore, the low yield of side product N2O is probably due to the absence of the generation of NH4NO3 during NH3‐SCR catalyzed by Fe‐loaded zeolites. [ABSTRACT FROM AUTHOR]

Monoliths manufactured by Direct Ink Writing containing 60% SSZ-13 (SiO2/Al2O3 = 23) and SiO2 with 10% laponite as a binder were investigated as self-standing structured catalysts for NH3-SCR of NOx after a short (4 h) and prolonged (24 h) ion exchange with copper and then compared with pure SSZ-13 exchanged under the same conditions. The catalysts were characterized by morphological (XRD and SEM), textural (BET and pore size distribution), chemical (ICP-MS), red-ox (H2-TPR), and surface (NH3-TPD) analyses. The silica-based binder uniformly covered the SSZ-13 particles, and copper was uniformly distributed as well. The main features of the pure Cu-exchanged SSZ-13 zeolite were preserved in the composite monoliths with a negligible contribution of the binder fraction. NH3-SCR tests, carried out on both monolithic and powdered samples in the temperature range of 70–550 °C, showed that composite monoliths provided very good activity, and that the intrinsic activity of SSZ-13 was enhanced by the hierarchical structure of the composite material. [ABSTRACT FROM AUTHOR]

In Japan, a Waste To Energy (WTE) plant with a strict NOx emission limit value of 50 ppm (O2 12%-dry) has been operated with selective non-catalytic reduction (SNCR). Ammonia or urea is used as a media for SNCR, but urea is safer than ammonia and is easy to use. However, urea has a problem of lower NOx removal efficiency than ammonia. Therefore, a technology to convert urea to ammonia on-site is necessary. In this work, the basic performance of this urea decomposition system, the operation results of SNCR, and the CO2 reduction by SNCR were studied.The urea decomposition system was a catalytic reactor, and when the catalytic temperature was above 250 °C and the space velocity was below 6000 h−1, the conversion to ammonia was almost 100%. The NOx removal ratio of SNCR was 20% at an ammonia equivalence ratio of 0.4 and about 40% at an equivalence ratio of 0.6, a performance level similar to other plant. Furthermore, it was estimated that CO2 emissions were reduced by 3.1% by applying SNCR instead of SCR, and when combined with other CO2 reduction measures of this plant, CO2 emissions were reduced by 16.2%. [ABSTRACT FROM AUTHOR]

NOx storage and reduction (NSR) catalysts are a well-known and broadly used technology to reduce NOx emissions from combustion engines, which may also be applied for hydrogen fueled engines in the future. In this study, Pt- and Pd-based NSR-catalysts were investigated in the absence and presence of water to understand how NO oxidation as well as the storage and reduction phases are influenced by the gaseous environment with H 2 as a reductant. A planar channel configuration was chosen for conducting planar laser-induced fluorescence experiments during the storage phase in addition to steady-state oxidation measurements and transient lean/rich cycles in a packed bed reactor. The presence of steam significantly decreases the NO oxidation activity of both noble metal catalysts. The Pt/BaO/Al 2 O 3 catalyst is more active during transient lean/rich cycles, however, it suffers an activity loss during repeated cycles, whereas the activity of the Pd/BaO/Al 2 O 3 sample is slightly more stable in the wet gas feed over time. All experiments showed a strong correlation between the NO 2 formation over the catalyst and its storage capability. The influence of water in the exhaust gas on the NSR-catalysts shows a strong temperature dependency on storage and reduction of NO for both catalysts containing Pt and Pd. The storage behavior is also strongly influenced by both the experimental configurations chosen revealing the significance of the interaction of intrinsic catalytic kinetics and mass transfer in the surrounding flow field. [ABSTRACT FROM AUTHOR]

This paper presents two mechanisms for the deNOx process and for the deN2O process (in two variants). The processes were carried out on a clinoptilolite zeolite catalyst with a deposited Cu–Cu monometallic dimer and Cu–Zn bimetallic dimer with bridged oxygen between the metal atoms. Analyses were performed for hydrated forms of the catalyst with a hydrated bridging oxygen on one of the metal atoms. Calculations were performed using DFT (density functional theory) based on an ab initio method. The analyses included calculations of the energies of individual reaction steps and analysis of charges, bond orders and bond lengths as well as HOMO, SOMO and LUMO orbitals of selected steps in the mechanism. Based on the results obtained, it was determined that the most efficient catalyst for both processes is a Cu–Zn bimetallic catalyst with a bridged hydroxyl group. It shows higher efficiency in the limiting step (formation of the -N2H intermediate product) than the previously studied FAU and MFI zeolites with a Cu–Zn bimetallic dimer. In addition, the possibility of using the catalytic system from the deNOx process in the deN2O process was presented, which can benefit SCR installations. In addition, it was proved that the order of adsorption of NO and N2O has significance for further steps of the deN2O process. In order to improve the comparison of FAU, MFI and CLI zeolite catalysts with a Cu–Zn dimer, further studies on the deN2O mechanism for the first two zeolites are needed. This study allows us to propose a bimetallic catalyst for the deNOx and deN2O processes. [ABSTRACT FROM AUTHOR]

Two series of MCM-36 zeolites intercalated with various pillars and modified with iron were synthesized, analyzed with respect to their physicochemical properties, and tested as catalysts for the NH3-SCR process. It was found that the characteristic MWW morphology of MCM-36 can be obtained successfully using silica, alumina, and iron oxide as pillars. Additionally, one-pot synthesis of the material with iron resulted in the incorporation of monomeric Fe3+ species into the framework positions. The results of catalytic tests revealed that the one-pot synthesized sample intercalated with silica and alumina was the most efficient catalyst of NO reduction, exhibiting ca. 100% activity at 250 °C. The outstanding performance of the material was attributed to the abundance of Lewis acid sites and the beneficial influence of alumina on the distribution of iron species in the zeolite. In contrast, the active centers originating from the Fe2O3 pillars improved the NO conversion in the high-temperature range. Nevertheless, the aggregated particles of the metal oxide limited the access of the reacting molecules to the inner structure of the catalyst, which affected the overall activity and promoted the formation of N2O above 300 °C. [ABSTRACT FROM AUTHOR]

The representative of natural layered clays, bentonite, was modified according to two routes and tested as a new catalyst for selective catalytic reduction of nitrogen oxides with ammonia (NH3-SCR). The natural acid-activated clay was ion-exchanged with Na+ or remained in H-form and pillared with metal oxides. In order to limit the number of synthesis steps, iron as an active phase was introduced simultaneously with Al2O3 during the intercalation procedure. Additionally, the samples were doped with 0.5 wt% of copper to promote low-temperature activity. It was found that the performed modifications resulted in disorganization of the ordered layered arrangement of bentonite. Nevertheless, acid activation and pillaring improved structural and textural parameters. The results of catalytic tests indicated that the samples containing Fe2O3 pillars promoted with Cu exhibited the highest NO conversion of 85% at 250 °C (H-Bent-AlFe-Cu) and 75% at 300 °C (Na-Bent-AlFe-Cu). What is important, activity of the protonated samples in the high-temperature region was noticeably affected by the side reaction of ammonia oxidation, correlated with the production of NO and resulting in N2O emission during the process comparing to Na-Bentonite catalysts. [ABSTRACT FROM AUTHOR]

This research work aims to study the performance of biochar-supported manganese-based catalysts for conversion of NOx in the selective catalytic reduction (SCR) process. Biochar, a high energy density solid generated from biomass pyrolysis, usually is combusted to provide extra heat to the pyrolysis process. Compared to other carbonaceous materials, biochar has a larger surface area, large surface functional groups and is more economically advantageous. An experimental and observational methodology was adopted in which biochar with activation temperatures of 500 °C, 600 °C, and 700 °C were used as additional catalytic support to the Manganese-based SCR catalyst. The prepared samples were analyzed by various techniques like X-ray diffraction, Scanning electron microscopy, X-ray photoelectron spectroscopy, NH3-Temperature-programmed desorption and H2-Temperature programmed reduction to study various parameters like crystallographic structure and crystal properties, chemical states and elemental composition, surface acidity, and reducibility of the catalyst. Upon adding biochar, it was observed that the pore volume increased by 150% and the surface area by 114%. Subsequently, catalytic activity tests were conducted on the effect of biochar on NOx removal, SO2, and H2O tolerance, and the optimum catalyst composition were found. Catalytic performance increases with the addition of biochar over all temperature ranges, with Mn/TiO2-Char700 reaching a maximum NOx conversion rate of 90%, indicating that biochar is a viable alternative to existing catalytic supports. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low-silica chabazite was synthesized without OSDA via interzeolite transformation. • The active center of Cu2+-2Z and [Cu(OH)]+-Z was tailored by CHA-cages opening. • The residual K+ ions ensure the stable presence of the active center Cu2+-2Z in 6MRs. Low-silica chabazite (CHA) catalysts with varying configurations of Cu2+-2Z and [Cu(OH)]+-Z active centers are developed through the regulation of the opening of CHA-cages. The catalysts are subsequently applied to the selective catalytic reduction of NO x by NH 3 (NH 3 -SCR) reactions. A series of characterizations and performance evaluations indicate that the density of [Cu(OH)]+-Z in eight-member rings (8MRs) is positively correlated with low-temperature performance. Moreover, the presence of partial Cu2+-2Z in six-member rings (6MRs) enhances activity and tolerance at high temperatures. The residual K+ ions in the CHA-cages after NH 4 + exchange are retained in the 6MRs. Density functional theory calculations demonstrate that the residual K+ ions stabilize the 6MRs structure, ensuring the entry and stable presence of the active Cu2+-2Z centers. In situ analysis reveals the reaction intermediates involved in the NH 3 -SCR process on representative catalysts. These findings can further elucidate the active centers of CHA-type catalysts and guide the design of commercial catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-oxidation synthesis strategy achieves strong synergistic effect of copper-iron complexes. • In situ technology explores the synergistic mechanism and magnetic field enhancement mechanism under reaction conditions. • Magnetic field promotes the adsorption of paramagnetic NO molecules and improves performance. Fe or Cu oxides and their composites are cost-effective yet seldom used in DeNO x because they deactivate easily. Doping/supporting enhances activity but increases synthesis complexity and cost. Here, we present a γ-Fe 2 O 3 -CuO composite oxide with a high synergy created through co-oxidation, which upon magnetization, exhibits further enhanced DeNO x activity. Detailed quasi in-situ XRD and in-situ DRIFTS analyses indicate that in Fe-Cu composite oxides, iron species inhibit the full reduction of Cu2+ to Cu0, while copper counters the formation of inactive α-Fe 2 O 3 , contributing to the γ-Fe 2 O 3 -CuO composite's enhanced stability during reactions. Fascinatingly, pre- and post-magnetization XPS and in-situ DRIFTS analyses demonstrate the magnetic field's role in promoting the chemisorption of both oxygen and NO, thereby enhancing DeNO x efficiency. This research not only achieves the synergistic coupling of copper and iron oxides and sheds light on the deactivation processes of their pure species but also serves as a pioneering exploration of magnetic manipulation in catalyst design, laying a foundation for future technological advancements. [ABSTRACT FROM AUTHOR]

This article compares performance of selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) applied on the same pilot unit, a 500 kW fluidized bed boiler burning Czech lignite. Correlation of the denitrification efficiency on the normalized stoichiometric ratio (NSR) is investigated. The fundamental principle of the SCR and SNCR is similar with the same reaction scheme. The difference is in the use of the catalyst that lowers the activation energy of the key reaction. As a result, the reduction is performed in the SCR method at lower temperatures. During experiments, the NSR was up to 1.6 for the SCR method. For the SNCR method, which has a higher reducing agent consumption, maximum denitrification efficiency was reached for NSR about 2.5. The efficiency of both secondary methods was investigated. The denitrification efficiency during experiments exceeded 98 % for the SCR method, and the SNCR method, together with the primary measures, reached an efficiency of 58 %.

[Display omitted] • SSZ-52 zeolite with a Si/Al ratio of 7 was successfully synthesized for the first time. • The defect-free structure of SSZ-52-7 was observed by high-resolution iDPC-STEM images. • Cu-SSZ-52-7 catalyst showed optimal NO x conversion and hydrothermal stability. • The aged Cu-SSZ-52-7 remained the highest amount of active Cu sites and acid sites. Cu-SSZ-52 zeolites, celebrated for their exceptional low-temperature NH 3 -SCR activity, are hampered by poor hydrothermal stability attributable to a low Si/Al ratio, which significantly constrains their practical utility. In this work, we successfully synthesized Cu-SSZ-52 catalysts with a Si/Al ratio as high as 7 for the first time. iDPC-STEM and PXRD analysis confirmed that the catalysts have the same structure as SSZ-52. Notably, the Cu-SSZ-52-7 catalyst showcased enhanced deNO x performance both prior to and following hydrothermal aging, outperforming Cu-SSZ-52 catalysts with a Si/Al ratio of 4 and Cu-SSZ-13 catalysts with a Si/Al ratio of 7. Our findings underscore that a continuous increase in the Si/Al ratio resulted in the promotion of deNO x activity and hydrothermal stability of Cu-SSZ-52 catalysts. [ABSTRACT FROM AUTHOR]

• The NOx conversion of the iron-manganese ore catalyst is above 85 %. • NH 3 prefers to adsorb on Fe sites on the Fe 2 O 3 /MnO 2 (110) surface. • The dehydrogenation process of NH 3 is more likely to occur at the Fe sites. • Mn sites play a important role in promoting the NH 2 NO decomposition to N 2. • The reason for the low N 2 selectivity of iron-manganese ore catalysts was discussed. Natural iron-manganese ores exhibit a good deNO x activity at low temperatures after a simple treatment, but the reason for its low N 2 selectivity requires further in-depth study. This work conducted deNO x performance and characterization tests on iron-manganese ore catalysts. Based on the experimental results, a simplified computational model of the iron-manganese ore catalyst (Fe 2 O 3 /MnO 2 (110) surface) was constructed, and the density functional theory (DFT) method was used to investigate the mechanism of N 2 formation in the NH 3 -SCR process. Fe and Mn in the iron-manganese ore play an important role in the deNO x activity, and NH 3 forms the stable chemical adsorption on its surface, especially on the Fe site, where the adsorption capacity of NH 3 is stronger than that of Mn site. The Fe site exhibits better ability than the Mn site in the dehydrogenation reaction of NH 3. However, in a comprehensive comparison, the capability of iron-manganese ore catalyst to promote NH 3 dehydrogenation is not high. In addition, the key NH 2 NO intermediate prefers to form on the Mn site over the Fe 2 O 3 /MnO 2 (110) surface. Among them, the Mn site is better than the Fe site in promoting the decomposition of NH 2 NO intermediate to form N 2. The study can further understand the microscopic mechanism of iron-manganese ore catalysts in N 2 formation, which lays a foundation for improving the N 2 selectivity of iron-manganese ore deNO x catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper presents the modeling and simulation of an industrial-scale chemical looping combustion (CLC) power plant, including all process units (reactors, flue gas treatment units, heat integration, steam cycle, and CO2 compression train). A model of a 525 MWth CLC power plant was built using a rigorous representation of the solid fuel and oxygen carrier. Petcoke was considered the main fuel of interest in this study, and it is compared with other solid fuels. The flue gas compositions obtained with the model show that cleanup units are mandatory to comply with CO2 quality requirements. High levels of flue gas treatment, including 97.1% deNOx and 99.4% deSOx, are needed to achieve typical specifications for captured CO2. This is mainly due to the high level of contaminants in the fuel, but also to the absence of nitrogen in the CLC flue gas, thus resulting in higher concentrations for all substances. The high level of flue gas treatment is thus one of the important challenges for solid fuel combustion in CLC. The overall CO2 capture efficiency of the plant is estimated to be as high as 94%. Regarding the energy balance, a process net efficiency of 38% is obtained. Comparing the results with other available technologies shows that CLC exhibits one of the highest net plant efficiencies and carbon capture rates. CLC is thus a promising technology to produce clean energy from solid fuels. Finally, based on a sensitivity analysis, it is shown that process efficiency is mainly affected by the design and performance of the CLC furnace, the steam injection rate in the fuel reactor, the char separation efficiency, and the excess oxygen in the air reactor. [ABSTRACT FROM AUTHOR]

A series of clinoptilolite-supported catalysts, modified with hydrotalcite-like phase (HT) by co-precipitation, were prepared and tested in NH3-SCR reactions. It was found that deposition of HT on clinoptilolite increased conversion of NO within 250–450 °C, and that the positive impact on the catalytic activity was independent of HT loading. The promoting effect of clinoptilolite was attributed to Brönsted acid sites present in the zeolite, which facilitated adsorption and accumulation of ammonia during the catalytic process. Concentration of N2O in the post-reaction gas mixture reached its maximum at 300 °C and the by-product was most likely formed as a consequence of NH4NO3 decomposition or side reaction of NH3 oxidation in the high-temperature region. The gradual elimination of nitrous oxide, noticed as the material with the highest concentration of hydrotalcite phase, was attributed to the abundance of oligomeric iron species and the superior textural parameters of the material. UV-Vis experiments performed on the calcined samples indicated that Fe sites of higher nuclearity were generated by thermal decomposition of the hydrotalcite phase during the catalytic reaction. Therefore, calcination of the materials prior to the catalytic tests was not required to obtain satisfactory overall catalytic performance in NO reductions. [ABSTRACT FROM AUTHOR]

The catalytic performance of Fe-catalysts in selective catalytic reduction of nitrogen oxides with ammonia (NH3-SCR) strongly depends on the nature of iron sites. Therefore, we aimed to prepare and investigate the catalytic potential of Fe-MCM-22 with various Si/Fe molar ratios in NH3-SCR. The samples were prepared by the one-pot synthesis method to provide high dispersion of iron and reduce the number of synthesis steps. We have found that the sample with the lowest concentration of Fe exhibited the highest catalytic activity of ca. 100% at 175 °C, due to the abundance of well-dispersed isolated iron species. The decrease of Si/Fe limited the formation of microporous structure and resulted in partial amorphization, formation of iron oxide clusters, and emission of N2O during the catalytic reaction. However, an optimal concentration of FexOy oligomers contributed to the decomposition of nitrous oxide within 250–400 °C. Moreover, the acidic character of the catalysts was not a key factor determining the high conversion of NO. Additionally, we conducted NH3-SCR catalytic tests over the samples after poisoning with sulfur dioxide (SO2). We observed that SO2 affected the catalytic performance mainly in the low-temperature region, due to the deposition of thermally unstable ammonium sulfates. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu-SSZ-13 catalysts with different Cu2+ species were synthesized successfully. • The balance between Cu2+-2Z and [Cu(OH)]+-Z exhibited optimal DeNOx performance. • The optimal ratio of Cu2+ species can promote the rapid formation of intermediates. In diesel vehicle exhaust after-treatment systems, high silica Cu-SSZ-13 has received increasing attention as a commercialized catalyst owing to its high efficiency in selective catalytic reduction reactions with NH 3 (NH 3 -SCR). However, research on the regulation of Cu2+ species within metal active centers in the pore structure of chabazite (CHA)-type zeolite to improve catalytic performance lacks sufficient depth. Herein, SSZ-13 zeolite with various Al distributions was prepared by adjusting the proportion of N,N,N-Trimethyl-1-adamantanaminiumhydroxide (TMAdaOH) and Na in the initial gel. Moreover, three representative Cu-SSZ-13 catalysts with different Cu2+ species were synthesized via an ion exchange method. 23Na MAS NMR and NO adsorption infrared spectroscopy results revealed that with increasing Na content and decreasing TMAdaOH concentration in the initial gel, the number of paired Al in the CHA framework gradually increased. Consequently, this increased the number of Cu2+-2Z sites near six-membered ring (MR) and reduced the amount of [Cu(OH)]+-Z sites near eight-MR. The fresh Cu-SSZ-13 catalyst, with a moderate amount of Cu2+-2Z and [Cu(OH)]+-Z, exhibited optimal catalytic performance across the entire temperature window. After hydrothermal aging, Cu-SSZ-13 with a higher concentration of Cu2+-2Z species featured optimal performance among all Cu-SSZ-13 catalysts above 400 °C. These findings indicated the significance of balancing the amount of both Cu2+-2Z and [Cu(OH)]+-Z in the Cu-SSZ-13 zeolite. Additionally, the results elucidated the reaction intermediates involved in the NH 3 -SCR process catalyzed by Cu-SSZ-13 with various Cu species. [ABSTRACT FROM AUTHOR]

The efficiency and robustness of selective catalytic reduction (SCR) by NH3 catalysts for exhaust gas purification, especially of heavy-duty diesel engines, will continue to play a major role, despite the increasing electrification of powertrains. With that in mind, the effect of the synthesis scale on commercially available Cu-exchanged chabazite catalysts for SCR was investigated through physicochemical characterizations and catalytic tests. During hydrothermal aging, both industrial and lab-scale prepared catalysts underwent structural dealumination of the zeolite framework and redistribution of the Al sites. Although both catalysts demonstrated similar NO conversion activity under SCR conditions, the lab-scale catalyst showed higher selectivity and lower activity in NH3 oxidation. Variations in N2O formation and NH3 oxidation rate were found to correlate with the formation of different copper species, and the compositions become less controllable in industrial-scale process. This case study focused on routes of ion exchange, and the results provide new insights into catalytic performance of the industrially-produced zeolites. [ABSTRACT FROM AUTHOR]

Grafted tungstophosphoric acid (H3PW12O40/ HPW) is applied as a catalyst in the selective catalytic reduction of NOx with NH3 (NH3-SCR). The HPW/CeO2 catalyst has been found to be effective in the SCR reaction compared to HPW/SiO2. The cobalt-exchanged HPW/CeO2 improved NOx conversion, which reached 98% over a wide operating temperature window (280–500 °C). The better NOx performance of the CoPW/CeO2 catalyst is mainly due to the higher dispersion of tungsten on the CeO2 support, the formation of oxygen vacancies and the production of nitrogenous species. Incorporation of vanadium decreased the acidity of HPW, which reduced SCR activity on the HPVW/CeO2 catalyst. [ABSTRACT FROM AUTHOR]

A novel tactic was employed to evaluate the low-temperature NH3-SCR (selective catalytic reduction) NOx removal property of manganese oxides (MnOx) in various valence states, avoiding the influences of size, morphology and synthetic method on catalytic activity. Firstly, similar sized hollow-spherical MnO2, Mn2O3, Mn3O4 and MnO were obtained by decomposing MnCO3 at 440 and 500 °C in Air, 430 °C in H2 and Ar, respectively. The orders of MnOx catalytic activity varied at different reaction temperature range, while MnO2 showed the best NO conversion. Surface acidity has significant influences on the SCR activity, Mn3O4 exhibits a better catalytic property than Mn2O3 below 300 °C, and conversely, Mn2O3 has a better high-temperature NO conversation than Mn3O4 due to a stronger NH3 adsorption ability above 300 °C. MnO will be oxidized in the studied atmosphere with 5% O2 to Mn3O4, Mn5O8 and finally to Mn2O3 successively, and the mixed phases of MnO/Mn3O4 or Mn3O4/Mn5O8 exhibit a better catalytic activity than Mn2O3 at 200–300 °C. [ABSTRACT FROM AUTHOR]

The Cu-SAPO-18 was prepared by the one-pot method and modified through hydrothermal post-treatment, metal-doped Nd(x)/Cu-SAPO-18 (x = 0.4, 0.8, 1.2, 1.6) catalysts were obtained. The catalytic performance of fresh and aged Nd(x)/Cu-SAPO-18 was evaluated by ammonia selective catalytic reduction (NH3-SCR) reaction. The NOx conversion rate of Nd (1.2)/Cu-SAPO-18 was highest. More than 94.5% NOx conversion was maintained over the aged Nd(x)/Cu-SAPO-18 during 250–450°C, which was almost 10% higher than the conversion of aged Cu-SAPO-18. Various techniques including XRD, XRF, BET, SEM, 27Al MAS NMR, XPS, UV-vis, NH3-TPD, H2-TPR, were applied to explore the effect of Nd content on the physiochemistry property of Cu-SAPO-18. The addition of Nd effectively maintained the relatively large specific surface area and uniform pore size distribution. Moreover, the dealumination progress of Cu-SAPO-18 was mitigated and the aggregation of copper species during hydrothermal aging process was restrained. Thus, Nd(x)/Cu-SAPO-18 owed less CuOx and more amount of isolated Cu2+ ions, which stabilized catalyst structure by entering the double 6-membered ring (D6R). Meanwhile, the incorporation of Nd enhanced the redox property and stabilised surface acid sites of Cu-SAPO-18, which were responsible for facilitating the adsorption and activation of reactants. [ABSTRACT FROM AUTHOR]

The application of layered zeolites of MWW topology in environmental catalysis has attracted growing attention in recent years; however, only a few studies have explored their performance in selective catalytic reduction with ammonia (NH3-SCR). Thus, our work describes, for the first time, the one-pot synthesis of Fe-modified NH3-SCR catalysts supported on MCM-22, MCM-36, and ITQ-2. The calculated chemical composition of the materials was Si/Al of 30 and 5 wt.% of Fe. The reported results indicated a correlation between the arrangement of MWW layers and the form of iron in the zeolitic structure. We have observed that one-pot synthesis resulted in high dispersion of Fe3+ sites, which significantly enhanced low-temperature activity and prevented N2O generation during the reaction. All of the investigated samples exhibited almost 100% NO conversion at 250 °C. The most satisfactory activity was exhibited by Fe-modified MCM-36, since 50% of NO reduction was obtained at 150 °C for this catalyst. This effect can be explained by the abundance of isolated Fe3+ species, which are active in low-temperature NH3-SCR. Additionally, SiO2 pillars present in MCM-36 provided an additional surface for the deposition of the active phase. [ABSTRACT FROM AUTHOR]

In this study, a series of Co-modified bimetallic MOF-74-Ni1Cox(x = 1, 2, 4, 6, 8) catalysts were successfully prepared by a hydrothermal method and applied for CO-SCR. Bimetallic MOF-74-NiCo catalysts exhibited higher catalytic activity than pure Ni-MOF-74 material. It was found that MOF-74-Ni1Co6 catalyst achieved a more than 98% NO conversion from 200 °C to 300 °C. This enhanced CO-SCR performance of MOF-74-NiCo catalysts were ascribed to the formation of more oxygen vacancies and strong synergistic interaction between Co and Ni ions. The feasibility of bimetallic MOF-74-NiCo as a promising DeNOx catalyst was evaluated in this work. [ABSTRACT FROM AUTHOR]

On the way towards a decarbonized mobility, hydrogen combustion engines can particularly contribute to applications for heavy‐duty and long‐haul routes. Using clean hydrogen as fuel results in formation of nitrogen oxides as quasi‐exclusive pollutant emissions, which can be minimized by combining motor‐related measures with an emission control system in the exhaust tailpipe. This review provides an overview on the impact of various engine operation conditions on the emissions of a hydrogen combustion engine and summarizes state‐of‐the‐art and future concepts for an efficient exhaust gas after‐treatment. [ABSTRACT FROM AUTHOR]

: In the present study we propose a more promising catalyst for the deNOx process to eliminate harmful nitrogen oxides from the environment. The study was performed with a computer calculation using density functional theory (DFT) based on an ab initio method. Two zeolite catalysts, FAU and MFI, were selected with additional Cu–O–Zn bimetallic dimer adsorbed inside the pores of both zeolites. Based on the analysis of preliminary studies, the most probable way of co-adsorption of nitric oxide and ammonia was selected, which became the initial configuration for the reaction mechanism. Two types of mechanisms were proposed: with hydroxyl groups on a bridged position of the dimer or a hydroxyl group on one of the metal atoms of the dimer. Based on the results, it was determined that the FAU zeolite with a bimetallic dimer and an OH group on the zinc atom was the most efficient configuration with a relatively low energy barrier. The real advantage of the Cu–Zn system over FAU and MFI in hydrothermal conditions has been demonstrated in comparison to a conventional Cu–Cu catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bulk V 2 O 5 catalysts were synthesized using organic acids with large surface areas. • The large surface area of V 2 O 5 was obtained by the addition of carboxylic acid. • V 2 O 5 with pore structure contributed to an increase the acid sites and redox sites. • High NO conversion was obtained at a low temperature (<150 °C) by bulk V 2 O 5. Selective catalytic reduction using NH 3 (NH 3 -SCR) is a chemical process that is used for the elimination of NOx (NO and NO 2). Although current vanadia-based catalysts need a high reaction temperature, which leads to deactivation of the catalysts, bulk vanadium oxide showed the potential for NH 3 -SCR at a low temperature below 150 °C. We investigated a method for synthesis of vanadium oxide with a large surface area using an organic acid to enhance its NH 3 -SCR activity. Vanadium oxide catalysts were synthesized from ammonium metavanadate (NH 4 VO 3) and organic acids (oxalic acid, succinic acid, malic acid and citric acid). When carboxylic acids (oxalic acid and succinic acid) were used as the organic acid source, the surface area of the catalysts increased up to 41 cm2 g−1, which was larger than that of vanadium oxide synthesized without an organic acid and with hydroxy acid. SEM and TEM measurements showed that vanadium oxide catalysts synthesized by the calcination of vanadyl oxalate at 300 °C (V 2 O 5 -OX_300) formed a pore structure that contributed to the increase in surface area. An increase in the number of acid sites and redox sites, which is important for NH 3 -SCR to proceed, was confirmed from NH 3 -TPD and H 2 -TPR measurements for V 2 O 5 -OX_300. The NO conversion of V 2 O 5 -OX_300 (47 % at 100 °C) was higher than that of the catalysts synthesized from only NH 4 VO 3 (19 % at 100 °C), indicating that vanadium oxide catalysts synthesized using carboxylic acid have the low-temperature NH 3 -SCR activity due to the increase in their surface area. [ABSTRACT FROM AUTHOR]

Fe–Mn nano-sized catalysts show remarkable deNOx activities at low temperatures. However, there is a noticeable disparity in N 2 selectivity before and after the addition of Fe element, and the cause of this difference remains unknown. In this study, Fe–Mn nano-sized catalysts were prepared by using the hydrothermal method and their deNOx performance and physicochemical properties were examined. Based on the results of experimental research, the simplified computational models for Fe–Mn nano-sized catalysts before and after introducing Fe element were constructed, namely α-MnO 2 (200) surface and Fe–Mn cluster model. The mechanism of N 2 generation during the NH 3 -SCR process of Fe–Mn nano-sized catalysts was thoroughly investigated by using the density functional theory. The Mn sites of Fe–Mn clusters are more favorable for NH 3 dehydrogenation reaction compared to the Mn sites on the α-MnO 2 (200) surface. Furthermore, compared to the α-MnO 2 (200) surface, the NH 2 NO intermediate tends to undergo dehydrogenation on the Fe–Mn clusters to generate N 2. These results will help to gain insight into the microscopic mechanism of Fe–Mn nano-sized catalysts in N 2 generation during NH 3 -SCR and lay the foundation for enhancing the N 2 selectivity of Fe–Mn catalysts. [Display omitted] • The deNOx efficiency of the nano-sized Fe–Mn catalyst can exceed 99% at 160–180 °C. • The nano-sized Fe–Mn catalyst exhibits favorable levels of N 2 selectivity. • NH 3 shows a greater tendency to adsorb on the Fe–Mn clusters than α-MnO 2 surface. • NH 2 NO on the Fe–Mn clusters undergoes dehydrogenation reactions to generate N 2. [ABSTRACT FROM AUTHOR]

A series of Mn–Ti oxide catalysts were synthesized by the sol–gel method and the effects of different synthesis conditions were investigated in sequence. The microstructures and properties of the catalysts were characterized by using N2 adsorption–desorption, XRD, SEM, H2-TPR, NH3-TPD, Raman and XPS. The catalytic performance over Mn–Ti oxide catalysts prepared under different synthesis conditions for the low-temperature SCR of NO with NH3 were also comparatively evaluated. The results reveal that the calcination temperature and metal source play a significant role in the characteristics and the SCR activities of the catalysts. A relatively low calcination temperature is beneficial to low-temperature SCR activity. Manganese nitrate or manganese acetate as the Mn source combining with tetrabutyl titanate as Ti source can achieve high SCR activities. The excellent low-temperature NH3-SCR activity can be ascribed to the appropriate textural properties, amorphous Mn-oxides with equal ratio of Mn3+/Mn4+, good low-temperature reducibility and abundant surface B-acid sites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical ordered MnFe 1-δ Co δ O x ternary oxide catalysts were prepared. • Co doping can enhance the low-temperature performance of the NH 3 -SCR reaction. • The enhanced performance depends on the increased acidity and redox of Hierc-MnFe 1-δ Co δ O x. • Co doping can retard the sulfuration rates of Hierc-MnFe 1-δ Co δ O x catalysts. Manganese (Mn)-based mixed oxides are considered the most efficient catalysts for low-temperature ammonia selective catalytic reduction of nitrogen oxides (NO x) (NH 3 -SCR of NO x). Water resistance and sulfur tolerance, especially the SO 2 tolerance of Mn-based catalysts, are the main obstacles preventing their practical application. Therefore, in this study, a series of cobalt (Co)-doped MnFeO x ternary mixed oxides catalysts with a hierarchically ordered structure (Hierc-MnFe 1-δ Co δ O x , δ = 0.2, 0.4 and 0.6) were developed and applied for NH 3 -SCR of NO x at low temperature. Compared with Hierc-MnFeO x , Hierc-MnFe 1-δ Co δ O x catalyst exhibited enhanced low-temperature activity and a broadened temperature window (NO x conversion above 80% was between 90 and 343 °C over Hierc-MnFe 0.6 Co 0.4 O x), as well as better H 2 O resistance and SO 2 tolerance. The enhanced low-temperature activity was attributed to a larger amount of active oxygen species, a higher proportion of Mn4+, Fe3+ and Co3+ content, and the improvement of surface acidity, which can facilitate the adsorption and activation of NO and NH 3. Additionally, the Hierc-MnFe 0.6 Co 0.4 O x catalyst exhibited superior soot tolerance due to its special hierarchically ordered architecture. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that the Co-modified Hierc-MnFe 1-δ Co δ O x ternary oxide catalyst could efficiently protect nitrate species on Hierc-MnFe 0.6 Co 0.4 O x from the poisoning effect of SO 2 , thereby boosting its SO 2 tolerance. This study provides a good candidate for low-temperature de NO x application with enhanced SO 2 and soot tolerance. [ABSTRACT FROM AUTHOR]

This Minireview presents an overview of the advancement and capabilities of the steady‐state isotopic transient kinetic analysis in the selective catalytic reduction of NOx. Firstly, a brief overview of the method and the kinetic parameters of catalyst‐surface reaction intermediates, including concentration and coverage of surface intermediates, surface residence time and intrinsic turnover frequency (TOF), is provided. Furthermore, the focus is on the application of SSITKA or a unique combination of SSITKA‐DRIFTS for the identification of active and/or inactive (spectators) species in NH3−SCR, H2−SCR and HCs−SCR. Different forms of adsorbed species and their formation rates revealing the main elementary steps on the catalyst's surface involving labeled molecules are discussed. The emphasis is laid on the optimization and design of industrial catalysts. [ABSTRACT FROM AUTHOR]

A theoretical study of N2, O2, NO and NO+ adsorption with cerium-modified mordenite (Ce-MOR) was carried-out. It was used the two-layer Integrated molecular Orbital + molecular Mechanics methodology (ONIOM2) by combining Density Functional Theory (DFT) and Universal Force Field (UFF) for the high and low level model, respectively. The formation active species of Ce based on the adsorption of CeO+ on crystallographycs positions T1, T2 and T4 in H-MOR. The geometric, vibrational and thermodynamic results indicate that the Ce atom of the CeO+ binds exothermal and spontaneously to two crystallographic non-equivalent oxygens (Om) of MOR (TnOm1Om2 ) according to: T1O1O4, T1O2O3, T2O4O7, T2O5O7 y T4O7O10 (T: Al or Si). The results of the interaction of N2, O2, NO and NO+ with Ce-MOR indicate that exothermic and spontaneous adsorption occurs only on the active sites located on the main 12 membered ring (12-MR) channel, according to: T1O1O4, T2O5O7 and T4O7O10. In general, the Ce-MOR system stabilizes the electrophilic species [CeO(NO+)], with activity for NOx reactions with nucleophilic reducting agents such as NH3, while it 1NO, 1 2NO adsorption that could be applicable for NOx catalysis in the absence of reducing agents. On the basis of the thermodynamic reaction functions, it is proposed that the most probable site for the location of the active CeO+ is T2O5O7. [ABSTRACT FROM AUTHOR]

• (EtOH + NH 3)-SCR process ensures impressive DeNOx performances in NO only media. • (Ag/Al 2 O 3 +WO 3 /Ce-Zr) dual-bed allows the Fast-SCR reaction at low temperature. • NH 3 -SCR reactivity over WO 3 /Ce-Zr is not optimal. • Adsorption of NH 3 compete with oxygenated EtOH-SCR by-products over WO 3 /Ce-Zr. • NO 2 partially reacts with CH 3 CHO to form NO over WO 3 /Ce-Zr. The Selective Catalytic Reduction (SCR) is one of the most efficient process for NO x removal from Diesel exhaust gas. However, the urea/NH 3 -SCR process implemented in recent vehicles still suffers from a poor activity in the low temperature range (T < 250°C). One main reason is its dependency against the NO 2 /NO x ratio, limiting the expected fast-SCR reaction in this temperature range. Recently, we shown that the addition of ethanol to ammonia led to a significant increase of the activity of a Ag/Al 2 O 3 catalyst in this low temperature range. Moreover, in a dual-bed configuration (Ag/Al 2 O 3 +WO 3 /Ce x -Zr y O 2), a remarkable improvement was achieved at low temperature using only NO as NO x. The present work aims to highlight the DeNO x chemistry encountered over the WO 3 /Ce x -Zr y O 2 catalyst in a bifunctional (EtOH+NH 3) mixture. In addition to the fact that this process takes advantage of the low temperature NO 2 formation over the upstream Ag/Al 2 O 3 catalyst, this work also puts in evidenced unexpected interactions between NO 2 and CH 3 CHO (resulting from ethanol oxidation over Ag/Al 2 O 3) thus leading to NO emission. [ABSTRACT FROM AUTHOR]

The present work is focused on the removal of NOx with reduced blue TiO2 with Fe (blue Fe-TiO2)- and Cu (blue Cu-TiO2)-doped photocatalyst. TiO2 was reduced via lithium in EDA (blue TiO2). Fe and Cu ions were doped in the reduced TiO2 (blue Fe-TiO2 and blue Cu-TiO2). The material resulted in a core-shell structure of amorphous and anatase phase. XPS suggests the existence of Ti3+ species and oxygen vacancies within the structure of TiO2. Additionally, valence bond (VB)-XPS shows the generation of intermediate levels at the band edge of the doped photocatalyst. Photocurrent, electrochemical impedance spectroscopy and cyclic voltammetry confirmed the enhanced charge-separation process in doped reduced TiO2. The photocatalysts were tested for the photo-oxidation of NOx. Blue Fe-TiO2 reveals the efficiency of 70% for NO elimination and 44.74% for NO2 formation. The improved efficiency of the doped photocatalyst is related to the re-engineered structure with Ti3+ species, oxygen vacancies, and charge traps. Electron spin resonance (ESR) measurement was carried out for blue Fe-TiO2 to confirm the formation of reactive oxygen species (ROS). Furthermore, ion chromatography was used to investigate the mechanism of NOx oxidation. In conclusion, the doped blue TiO2 has a strong tendency to photo-oxidize NOx gasses. [ABSTRACT FROM AUTHOR]

• CeSnWBaO x /TiO 2 catalyst maintained stable NO removal under fluctuating flue gas. • Ammonia was mainly stored in physical form and partly by chemical adsorption. • High temperature enhanced ammonia activation, excess NO induced ammonia release. • The characteristics have great guiding significance for dealing with ammonia slip. The ceria-based catalyst exhibited excellent storage/release characteristics of ammonia, ensuring stable deNO x efficiency under fluctuating engineering conditions, while greatly reducing ammonia slip. In this work, characteristics of ammonia storage/release of CeSnWBaO x /TiO 2 catalyst were investigated. Results showed that the catalyst exhibited much higher catalytic activity than the theoretical maximum under low NH 3 /NO ratios. Especially, the amount of effective ammonia release reached maximum at 250 °C with increase of excess NO. Low temperature was conducive to storage and the stable storage amount was 22.97 μmol·m−2 at 50 °C, effective release of ammonia occurred mainly at the active temperature window. Ammonia storage of the CeSnWBaO x /TiO 2 catalyst was affected by the activation of active sites and thermal vibration at the same time. Ammonia storage under low temperature was mainly in physical form and at weak acid sites, while high temperature enhanced activation of ammonia, resulting in an increase of ammonia storage at 350 °C. The catalyst had both weak and strong stored-ammonia, strong stored-ammonia could be effectively released only in the induction of NO. Ammonia storage of catalyst was the key to ensure stable deNO x efficiency under fluctuating engineering condition. The characteristics are of great guiding significance for dealing with ammonia slip. [ABSTRACT FROM AUTHOR]

Pt@g-C 3 N 4 /CeO 2 photocatalyst was prepared by calcination of g-C 3 N 4 /CeO 2 mixture followed by impregnating Pt. Under the irradiation of visible light with the presence of water vapor at room temperature, Pt@g-C 3 N 4 /CeO 2 showed significant performance for remediation of NO x. The deNO x mechanism was studied by modified in-situ FTIR. The results proved that NO was prone to adsorb on the surface of Pt@CeO 2 and oxidized to nitrite for storage. Then, the photoinduced hydrogen on Pt@g-C 3 N 4 component could diffuse into the vicinity of nitrite through the spillover effect of Pt and reacted with nitride to produce N 2 and H 2 O. Image 1 • Pt@g-C 3 N 4 /CeO 2 photocatalyst for the remediation of low concentration NO x at room temperature was prepared. • The strong interaction between g-C 3 N 4 and CeO 2 contributes to the formation of nitrite rather than nitrate. • H 2 reacts with nitrites on surface of catalyst to generate N 2 and H 2 O. [ABSTRACT FROM AUTHOR]

V2O5-MoO3/TiO2 based catalytic bag filters were developed for the simultaneous removal of particulates and NO in the temperature range of 200–250 °C. Good denitrification activity, dedust efficiency as well as high adhesion strength in the temperature range of 200–250 °C was exhibited. The study of catalyst powder for coating revealed that the increased V and Mo content in catalyst can elevate the low-temperature activity, and the chosen V10Mo10 sample for coating showed the best activity with 100% NO conversion at just 180 °C. The further research on catalytic bag filter found the low ratio of PTFE, high loading and long residence time (e.g., low filtration velocity or double layer filter) may help to achieve high DeNOx efficiency. The best performance was obtained with above 80% NO conversion at 200–250 °C even in the presence of SO2/H2O and 99.9% dust collection efficiency on the condition of 500 g/m2 loading, 10% PTFE, 0.5 m/min filtration velocity and double layers of filter, which demonstrated great feasibility for industrial application. [ABSTRACT FROM AUTHOR]

The properties of dihydroxycarbonate (malachite) and trihydroxynitrate of copper were studied in order to apply their ammonia solutions for the synthesis of copper-substituted ZSM-5 zeolites. Copper concentration and NH 4 OH/Cu2+ ratio in the solutions varied 1–12 g/l and 6–30, respectively. The parameters of Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherms revealed the favorability of the chosen conditions and the chemical nature of [Cu(NH 3) n ]2+ ions sorption by zeolite. For both copper salts, the sorption capacity of H-ZSM-5 for Cu2+ ions was higher in the solutions having NH 4 OH/Cu2+ = 6–10 compared to 30. To identify the synthesis and structure – activity relationship correlations, the ammonia solution and Cu-ZSM-5 samples were characterized by EPR, UV–visible spectroscopy, temperature-programmed reduction by hydrogen (H 2 -TPR). The calcined Cu-ZSM-5 samples produced at NH 4 OH/Cu2+ = 6–30 contained two types of the isolated Cu2+ ions (bare Cu2+ and [Cu(OH)]+), differing in their Redox properties. Their reducibility improved with an increase in the copper loading and with a decrease in NH 4 OH/Cu2+. At NH 4 OH/Cu2+ = 6–10, the samples additionally comprised the structures of Cu2+ ions with extra-lattice oxygen (ELO), which were formed due to hydrolysis of [Cu(NH 3) n (H 2 O)]2+ to [Cu(NH 3) n (OH)]+ and then to [Cu(OH) 2 Cu]2+. Cu2+–ELO structures possessed a greater ability to complete reduction than both types of isolated Cu2+ ions. Correlations with DeNOx properties in selective catalytic reduction (SCR) of NO by propane and ammonia are discussed. [Display omitted] • Synthesis of ion-exchanged Cu-ZSM-5 using ammonia solutions of copper hydroxysalts. • NH 4 OH/Cu2+ in solution affect copper content and type of Cu-ions loaded in ZSM-5. • At NH 4 OH/Cu2+ = 30, there is 2 types of isolated Cu2+ ions differing in Redox. • At NH 4 OH/Cu2+ = 6–10, reducibility is improved due to Cu2+–ELO structures. • Cu2+–ELO structures enhance SCR NO performance compared with isolated Cu2+ ions. [ABSTRACT FROM AUTHOR]

Hydrogen as carbon-free fuel is a very promising candidate for climate-neutral internal combustion engine operation. In comparison to other renewable fuels, hydrogen does obviously not produce CO2 emissions. In this work, two concepts of hydrogen internal combustion engines (H2-ICEs) are investigated experimentally. One approach is the modification of a state-of-the-art gasoline passenger car engine using hydrogen direct injection. It targets gasoline-like specific power output by mixture enrichment down to stoichiometric operation. Another approach is to use a heavy-duty diesel engine equipped with spark ignition and hydrogen port fuel injection. Here, a diesel-like indicated efficiency is targeted through constant lean-burn operation. The measurement results show that both approaches are applicable. For the gasoline engine-based concept, stoichiometric operation requires a three-way catalyst or a three-way NOX storage catalyst as the primary exhaust gas aftertreatment system. For the diesel engine-based concept, state-of-the-art selective catalytic reduction (SCR) catalysts can be used to reduce the NOx emissions, provided the engine calibration ensures sufficient exhaust gas temperature levels. In conclusion, while H2-ICEs present new challenges for the development of the exhaust gas aftertreatment systems, they are capable to realize zero-impact tailpipe emission operation.

As a new way for the high-value utilization of red mud (RM) waste, we proposed an improved approach to prepare the RM-based sludge/powder via the sulfuric acid hydrothermal dissolution and NH3 aqueous precipitation route and then the RM-based industrial-sized honeycomb (150 × 150 × 600 mm) was successfully produced by the extrusion moulding method in pilot scale. The synthesized RM-based powdery/honeycomb catalyst exhibited more than 80% deNOx activity and good durability of H2O and SO2 above 350°C. But the decline of NO conversion was also observed above 350°C, which was confirmed to result from the increased oxygenation of NH3 at high temperature. To improve the NO conversion at high temperature, NH3 was shunted and injected into the catalyst bed at two different places (entrance and centre) to facilitate its uniform distribution, which relieved the oxidation of NH3 and increased deNOx efficiency with 98% NO conversion at 400°C. This work explored the industrial application feasibility for the RM-based honeycomb catalyst as well as the possible solution to decrease the oxygenation of NH3 at high temperature, which presented a valuable reference for the further pilot tests of RM catalyst in industry.

Supported binary indium–cobalt oxide catalysts showed high activity in joint reduction of nitrogen(I, II) oxides with carbon monoxide. Their activity is determined not only by the composition, but also by the order of introducing the active components. In moist reaction systems (N2O + NO + CO + H2O), the best results were reached on In2O3,Co3O4/Al2O3 catalysts: 90–98% conversion of the reactants at 450–500˚C. [ABSTRACT FROM AUTHOR]