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The development of superior low-temperature catalytic performance and inexpensive catalysts for the removal of volatile organic compounds (VOCs) is crucial for their industrial application. Herein, CuO/Ce0.6Zr0.4O2 catalysts calcinated at different temperatures (Cu/CZ-X, X represented calcination temperature) were prepared and used to eliminate toluene. It can be found that Cu/CZ-550 presented the highest low-temperature catalytic activity, with the lowest temperature (220 °C) 50% conversion of toluene, the highest normalized reaction rate (3.1 × 10−5 mol·g−1·s−1 at 180 °C) and the lowest apparent activation energy value (86.3 ± 4.7 kJ·mol−1). Systematically, the surface properties analysis results showed that the optimum redox property, abundant oxygen vacancies, and plentiful surface Ce3+ species over Cu/CZ-550 were associated with the strong interaction between Cu and support could significantly favor the adsorption and activation of toluene, thus resulting in its superior catalytic performance. [ABSTRACT FROM AUTHOR]

With the development of carbon dioxide (CO2) capture, storage and utilization (CCSU) technologies, CO2 has gradually become a desired feedstock for the production of value-added chemicals like methane (CH4). Ceria (CeO2)-based catalysts have gained much attention because of their potential to efficiently hydrogenate CO2 to CH4 under mild conditions. Here we systematically outline the advances in CeO2-based catalysts for CO2 methanation mainly from the perspective of mechanism investigation and catalyst development. Various in situ/operando and ex situ technologies have verified that active metal and oxygen vacancies at the metal/metal oxide–CeO2 interface act as the prime active sites to promote the formation and hydrogenation of key intermediates during the CO2 methanation reaction. Kinetic analysis and in situ DRIFT characterization combined with theoretical calculations revealed that the reaction mechanism toward CO2 methanation is sensitive to active sites, and the formate route versus the carboxyl (CO*) route has been widely detected as the main methanation pathway over CeO2-based catalysts. Additionally, mainstream strategies to improve CeO2-based catalysts include optimizing reducibility, adjusting the distribution of basic sites, dispersing active metal supported on CeO2, and increasing the amount of oxygen vacancies or additional active sites for CO2 adsorption and selective hydrogenation into CH4. Finally, perspectives on the deeper understanding of active sites and intermediates' evolution and the challenges of CeO2-based catalysts for CO2 methanation in future investigations are presented. [ABSTRACT FROM AUTHOR]

CuO–CeO2 (Cu–Ce) catalyst with a CuO/CeO2 mass ratio of 1 prepared by a sol–gel method is used in the CO catalytic oxidation reaction in the actual industrial sulfur-containing atmosphere. At a reaction temperature of 200 °C, the catalyst exhibits quite different stability under sulfur-containing and sulfur-free conditions. When 30 ppm SO2 was added to the feed gas, the Cu–Ce catalyst had an initial CO conversion rate of 100%, gradually decreasing after 26 h, and this catalyst completely deactivated at about 50 h. However, the CO conversion rate of the catalyst under sulfur-free conditions could be nearly maintained at 100% within the measured time range (60 h). The results of IR, Raman, and XPS characterizations proved that the accumulation of cerium sulfate on the Cu–Ce catalyst would cover the active sites of the catalyst, eventually leading to the complete deactivation of the catalyst, which provides favorable evidence for the actual industrial anti-sulfur application. [ABSTRACT FROM AUTHOR]

The improved Ni/SBA-15 catalysts were prepared by thermal inducing method and applied to dry reforming of methane. The promoting effect exerted by thermal activated reconstruction was studied systematically by means of various characterization techniques. TEM results indicated that the thermal inducing process led to the reconstruction of Ni particles to form ultra-fine Ni nanoparticles (2–3 nm) uniformly distributed on SBA-15. The resulting Ni nanoparticles not only improved catalytic activity but also inhibited the formation of carbon deposition during the DRM reaction. The thermal treatment catalyst with tiny particles presented the superior catalytic performance in the DRM reaction, where H 2 /CO ratio was close to 1 and no deactivation was discovered after continuous reaction at 750 °C for 50 h. Additionally, it was found that the metal-support interaction was strengthened observably after the thermal activated reconstruction. The strong interaction anchored Ni particles to prevent their high temperature sintering, thus forming stable catalytic centers. Therefore, the conversions of both CO 2 and CH 4 almost stabilized at 90% and 85%, respectively, for the thermal activated reconstruction samples during the long-term catalytic test. Image 1 • The T-Ni/SBA-15 catalyst exhibits excellent catalytic activity. • The reconstruction of Ni particles improved catalytic activity and inhibited the formation carbon deposition. • The metal-support interaction was significantly enhanced after the thermal activated reconstruction. [ABSTRACT FROM AUTHOR]

Catalytic desulfurization is favored for its ability to desulfurize low concentrations of SO2 by generating sulfur without the need for flue gas conditioning or additives. Maintaining reaction efficiency at a low temperature would justify the industrial scale use of this method. To that end, in this study, we modified a previously reported highly efficient CuO-ZrSnO4 catalyst and investigated its desulfurization performance. The non-thermal plasma (NTP) method was used to enhance the low-temperature efficiency of the catalyst. The desulfurization rate was significantly improved without generating excess heat or by-products in the low-output mode of post-plasma-catalysis-type (PPC-type) dielectric barrier discharge (DBD). In addition, we studied the physicochemical properties of the catalyst (pore structure, physical structure, morphology, electronic properties, and chemical state) under plasma enhancement conditions. The catalyst loaded with 20 wt% Cu and aged at 40 °C exhibited optimum desulfurization performance. This study provides a theoretical foundation for the analysis of plasma-enhanced catalytic desulfurization under low-temperature conditions. [ABSTRACT FROM AUTHOR]

A series of CeO2-modified TiO2–ZrO2–SO42− catalysts were employed to the selective catalytic reduction (SCR) of NOx by NH3. The obtained results indicated that the interaction between CeO2 and TiO2–ZrO2–SO42− contributed to the increased reducibility and decreased surface acidity with the augment of CeO2. The in situ DRIFTS results suggested that suitable surface acidity and reducibility could be offered by increasing the ceria loadings from 24 to 40 wt%. The amount of adsorbed NH3 species, amide species (–NH2) and activated nitrate was increased with the augment of ceria. Excessive addition of CeO2 (80 wt%) resulted in the lacking of surface acid sites and induced the inert nitrate species generation on the catalysts surface. [ABSTRACT FROM AUTHOR]

The promoting effects of SO42− on N2 selectivity for selective catalytic oxidation (SCO) of ammonia to nitrogen over RuO2/ZrO2 catalyst were systematically investigated. The catalysts were measured by different characterization methods (BET, XRD, TEM, NH3–TPD and in situ DRIFTS). The results showed that the introduction of SO42− into RuO2/ZrO2 presented obvious effects on the structure, surface acidity and N2 selectivity of RuO2/ZrO2. The introduction of SO42− obviously increased the amount of surface acid sites, which could promote the adsorption of ammonia species and prevent the excessive oxidation of ammonia to NOx, improving the N2 selectivity dramatically. The DRIFTS results confirmed that the SCO of ammonia over RuO2/ZrO2–SO42− followed the in situ selective catalytic reduction of NOx (i-SCR) mechanism, involving NH3 oxidation to NO species and –NH2 reacted with NO to form the main product N2. The presence of SO42− not only increased the surface acid sites of the catalyst, but also inhibited the production of nitrate species, which was beneficial to improve the N2 selectivity. [ABSTRACT FROM AUTHOR]

Pt-Pd-HMS catalyst was obtained by one-pot method. Benzoic route and aliphatic carbonyl route coexisted for the catalytic combustion of toluene over the active sites of one-pot synthesized Pt-Pd-HMS, while benzoic was the major pathway of toluene catalytic combustion over the active sites of impregnated Pt-Pd/HMS. Simultaneous generation of benzoate and aliphatic compounds accelerated toluene combustion over the Pt-Pd-HMS catalyst. • One-pot synthesized Pt-Pd-HMS exhibits optimal performance with T 90 = 179 °C. • One-pot approach and bi-metallic strategy reduced metal particle size. • Generation of benzoate and aliphatic species accelerate catalytic performance. Pt-Pd-HMS catalyst had been prepared by a one-pot approach and tested for toluene combustion. Comparing with conventional impregnated Pt-Pd/HMS (E a = 111.41 kJ/mol, Pt-Pd particle size = 23.4 nm), the Pt-Pd-HMS exhibited lower activation energy (E a = 80.23 kJ/mol) and smaller Pt-Pd particle size (6.3 nm). Moreover, surface Pt0/Pt total of the Pt-Pd-HMS (52.8%) was higher than that of the Pt-Pd/HMS (46.8%), and Pt-Pd-HMS obtained an optimal catalytic performance with T 90 = 179 °C at a GHSV = 26,000 mL/(g·h). In-situ DRIFTS indicated that simultaneous generation of benzoate species and aliphatic compounds as intermediates occurred on the active sites of Pt-Pd-HMS. In contrast, the intermediates of toluene combustion on the active sites of Pt-Pd/HMS were dominated by benzoates. [ABSTRACT FROM AUTHOR]

CuO-Fe 2 O 3 catalysts categorized by the thermal treatment were systematically investigated for ammonia oxidation to nitrogen. The activity results exhibited that the calcination temperature had a significant contribution to the difference of the catalytic performance. Lower calcination temperature (≤500 °C) resulted in the excellent catalytic activity owing to the formation of large surface area, superior redox behavior and abundant surface oxygen species. On the contrary, the catalytic activity of catalysts declined with further raising the calcination temperature (≥600 °C) due to the destroyed structure and acid sites. In addition to this, DRIFTS study revealed that the reaction of ammonia oxidation largely depended on the presence of surface active oxygen on the catalysts. In particular, fast ammonia activation was observed on CuO-Fe 2 O 3 –500 °C, which was reflected by the rapid formation of –NH 2 and nitrate species on DRIFTS combining the XPS results. The intermediates –NH 2 and NO of internal selective catalytic reduction (iSCR) predominantly accounted for the excellent catalytic activities. The significant difference of the activation of surface species and catalytic activity impacted by the calcination temperature was observed, and the complete conversion temperature of NH 3 on CF-500 is 25 °C lower than that of CF-400. The NH 3 -SCO reaction over CuO-Fe 2 O 3 catalysts followed the same "internal" selective catalytic reduction (iSCR) mechanism. The key intermediate (-NH 2) could rapidly react with the in situ-generated NO ad-species to form N 2 and H 2 O. Unlabelled Image • The calcination temperature displayed a significant effect on CuO-Fe 2 O 3 for ammonia oxidation. • The CuO-Fe 2 O 3 –500 °C reached 100% conversion of NH 3 at 225 °C. • Calcination temperature influenced the physicochemical property and acidity of catalysts. • CuO-Fe 2 O 3 calcined at different temperatures showed similar reaction mechanism following iSCR path. [ABSTRACT FROM AUTHOR]

The effect of different pH values (8, 9, 10 and 11) on the catalytic activity over CeSiW catalysts was investigated for the selective catalytic reduction of NO by NH3. CeSiW-9 showed a remarkable higher NOx conversion. The strongest interaction was observed between silicotungstic acid and CeO2 over CeSiW-9, resulting in the improvement of redox ability and surface acidity, which could increase the catalytic activity. The superior catalytic performance of the CeSiW-9 catalyst was attributed to the favored pore structures, excellent redox ability and the abundance of surface acid sites, which depended on pH values in the preparation process of CeSiW catalysts. [ABSTRACT FROM AUTHOR]

Highly dispersed Ni/SBA-15 catalysts were prepared via template extraction with varying different extraction times (Ni/S-x, x = 0.5, 3.5, 6.5 h) for methane reforming with carbon dioxide. Based on the various characterization results and initial activity evaluation, Ni/S-3.5 h catalyst showed the best catalytic performance. Compared with the catalyst prepared via template calcination (Ni-S), Ni/S-3.5 h catalyst held steady with CH4 and CO2 conversions while those of the Ni-S catalyst respectively decreased by 15 and 11% during the long-term stability test at 700 °C for 50 h. As TEM and TG-DSC results confirmed, Ni particles in spent Ni/S-3.5 h catalyst stayed well-dispersed with size slightly increasing from an initial 3.9-4.1 nm and nearly no carbon deposition was observed. On the contrary, Ni-S catalyst was subjected to sintered metal particles (increased from 11.6 to 18 nm) and formed carbon fibers. The prominent resistance to sintering and coking over stable Ni/S-3.5 h catalyst was attributed to the high dispersion and strengthened metal-support interaction induced via the residual in situ templates. [ABSTRACT FROM AUTHOR]

For the selective catalytic reduction (SCR) of NO x by NH 3 , a variety of SO 4 2−/α-Fe 2 O 3 catalysts were created and utilized. The consequences manifest that the sulfation treatment signally boosted the NO x conversion of α-Fe 2 O 3. With varying SO 4 2− loadings, the T 90 of SO 4 2−/α-Fe 2 O 3 catalysts ranges from 10% SO 4 2−/α-Fe 2 O 3 (301 °C) > 15% SO 4 2−/α-Fe 2 O 3 (306 °C) > 5% SO 4 2−/α-Fe 2 O 3 (314 °C) > 20% SO 4 2−/α-Fe 2 O 3 (321 °C). The optimum concentration of sulfate treatment samples was 10% wt., producing approximately 100% NO x conversion at 325–400 °C. Although the introduction of SO 4 2− weaken the redox capacity of α-Fe 2 O 3 , the quantity and strength of acidic sites on SO 4 2−/α-Fe 2 O 3 was dramatically enhanced. Meanwhile, introducing SO 4 2− to α-Fe 2 O 3 hindered the ammonia oxidation process and increased the pore volume of the catalyst, enhancing SCR activity. In situ DRIFTS investigations demonstrated that NH 3 adsorbed on Brønsted acid sites displayed better stability over SO 4 2−/α-Fe 2 O 3 catalysts. Due to the decreased capacity of the catalyst surface to adsorb NO x , the E-R route prevails on 10% SO 4 2−/α-Fe 2 O 3 catalyst. [Display omitted] • SO 4 2− could effectively improve the SCR activity of SO 4 2−/Fe 2 O 3 catalyst. • The 10% SO 4 2−/α-Fe 2 O 3 catalyst showed >95% conversion of NO x at 325–400 °C. • SO 4 2− treatment can obviously enhanced the surface acidity of the catalyst. • The 10% SO 4 2−/α-Fe 2 O 3 catalyst mainly follows the E-R mechanism. [ABSTRACT FROM AUTHOR]

Abstract: A series of WO3–ZrO2 carriers were prepared by co-precipitation method with different mass fractions (0wt%, 5wt%, 10wt%, 15wt% and 20wt%) of WO3, and MnO x –CeO2/WO3–ZrO2 monolith catalysts were prepared for selective catalytic reduction of NO x with ammonia (NH3-SCR) in the presence of excessive O2. The catalysts were characterized by N2 adsorption–desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and NH3/NO temperature-programmed desorption (NH3/NO-TPD). The experimental results showed that, the tungsten modified monolith catalyst MnO x –CeO2/WO3–ZrO2 with the WO3 content 10wt% had the best catalytic activity and the widest reaction window; it possessed a better thermal stability than V2O5/WO3/TiO2 catalyst, and showed a better H2O and SO2 tolerance than MnO x –CeO2/ZrO2. The characterization results indicated that MnO x –CeO2/10% WO3–ZrO2 had the best textural properties, a well-dispersed state of WO3, the lowest binding energy of Ce3+ 3d5/2, the maximum value of Ce3+:Ce=20.7%, the suitable molar ratio of Mn:Ce≈1, and a co-existence state of MnO2–Mn2O3. In addition, it had the most adsorbed sites of NH3 or NO species. The NO x conversion was more than 80% in the temperature range of 150°C to 380°C at the space velocity of 10,000h−1. It possessed better potential for practical application. [Copyright &y& Elsevier]

A series of Ce/Fe-Zr-SO 4 2 - catalysts have been prepared and developed for selective catalytic reduction of NO with ammonia (NH 3 -SCR). The catalysts were characterized by XRD, H 2 -TPR, N 2 adsorption-desorption, NH 3 -TPD and DRIFTS. The characterization results demonstrated that the coexistence of cerium and sulfuric acid on Fe-Zr catalyst could contribute to excellent SCR performance. Among all samples, Ce/Fe-Zr-0.3 S catalyst showed the optimal NO X conversion, reaching more than 80% at 250 °C at a GHSV of 60,000 h−1. Moreover, the optimum concentration of SO 4 2- to modify Ce/Fe-Zr catalyst was 0.3 mol/L. The low sulfuric acid concentration contributed to improving low-temperature activity, while high concentration leaded to outstanding high-temperature activity. According to H 2 -TPR and NH 3 -TPD, the presence of SO 4 2- increased the total amount of acid sites and more stable sulfate species were formed with higher concentration of sulfuric acid. In situ DRIFTS revealed the NH 3 molecule was mainly activated at the Lewis acid site and reacted with the adsorbed NO X species (such as bidentate nitrates) to produce N 2 and H 2 O, which conformed to the L-H reaction mechanism. [Display omitted] • The optimal sulfuric acid concentration for the acid-treated Ce/Fe-Zr support was 0.3 mol/L. • The superior catalytic activity was greatly due to proper surface acid sites and redox ability. • The introduction of both CeO 2 and SO 4 2- improved low-temperature catalytic activity of Fe-Zr catalysts. • Different concentrations of sulfuric acid had different effects on catalytic activity. [ABSTRACT FROM AUTHOR]

CuO-CeO 2 catalysts modified with WO 3 were prepared by a sol-gel method and applied in selective catalytic oxidation (SCO) of NH 3 to N 2. It can be found that the NH 3 conversion showed a gradually decreased trend but the N 2 selectivity monotonically increased with the WO 3 introduced. As evidence from H 2 -TPR and Raman measurements, the doping of WO 3 resulted in a decrease in the concentration of oxygen vacancy and thereby reduced the redox ability of Cu-Ce, which was not helpful for the conversion of NH 3. However, NH 3 -TPD and in situ DRIFTS results showed that WO 3 introduction can significantly enhance the density of Brønsted acid sites on the catalyst and thereby promote the adsorption of NH 3 molecules. Typically, CuO-CeO 2 doping with 15 wt% WO 3 (Cu-Ce-15W) presented the highest NH 3 storage capacity. This could suppress the over-oxidation of NH 3 and thus make contribution to the enhancement of N 2 selectivity. This work could help to engineer highly efficient catalysts for NH 3 -SCO reaction. [Display omitted] • CuO-CeO 2 catalysts modified with WO 3 were prepared by a sol-gel method. • Cu-Ce-W catalysts exhibited excellent NH 3 -SCO performance at 200–300 °C. • Enhanced acidity contributed to the superior N 2 selectivity over Cu-Ce-W. • The doping of WO 3 resulted in a decrease in the concentration of oxygen vacancy. • Cu-Ce-W catalysts could suppress the over-oxidation of NH 3 and thus make contribution to the enhancement of N 2 selectivity. [ABSTRACT FROM AUTHOR]

In order to understand the role of Ca in coke behavior, the DRM reaction was performed in the thermodynamic active zone of coke formation. After dynamically reacting at 650 °C for 48h, the Ni-HMS catalyst was covered with a substantial number of nanotubes, while only a few amount of carbon deposition was produced on the NiCa-HMS catalysts. The remarkable anti-coking property was mainly due to robust basic sites supplied by CaO, which promoted the CO 2 adsorption and accelerated the carbon gasification reaction. Moreover, strong basicity could inhibit the adsorption of methane and reduced the production of cracked carbon. Apart from these, the introducing of Ca significantly enhanced the metal-support interaction and decreased the particle size of nickel. • We have prepared a series of NiCa-HMS catalysts with high anti-carbon and anti-sintering properties by a facile one-step synthesis method. • Ni particles were stabilized by the enhanced metal-support interaction. • The carbon deposition of the catalyst is suppressed after doping CaO. A series of Ni-Ca-HMS catalysts were prepared by one-step co-assembly synthesis and applied to dry reforming of methane. The promoting effect of CaO on the inhibition of carbon deposition was investigated via the DRM reaction over the Ni-HMS catalysts. The results indicated that the doping of Ca not only significantly enhanced the metal-support interaction, but also decreased the graphitic degree of deposited carbon. Moreover, it was found that the coking-resistance was obviously increased after introducing calcium. The presence of CaO promoted CO 2 adsorption and accelerated the removal of carbon. Interestingly, the Ni/Ca ratio also played a vital role. The Ni-Ca-HMS catalyst with Ni/Ca ratio of 3:2 exhibited the highest stability and coke-resistance during continuously reacting in the thermodynamic active zone of coke formation (557 ~ 700 °C). Only 4.2% deposited carbon was produced for 3Ni2Ca-HMS catalyst after dynamically reacting at 650 °C for 48 h, which was much lower than Ni-HMS catalyst (31.7%). Besides, excellent anti-sintering property was also obtained on 3Ni2Ca-HMS catalyst only with the increment of Ni particle size from 3.73 to 3.99 nm. [ABSTRACT FROM AUTHOR]

Iron-tungsten composite oxides catalyst prepared by grinding methods (FW-GR) exhibits excellent catalytic activity for SCR NO by NH 3. The FW-GR catalyst possessed higher surface acidic sites and acidic strength, the main reaction mechanisms follows the "L-H" at low temperature and "E-R" at high temperature. • The iron-tungsten catalysts prepared by grinding and sol–gel methods exhibited high activity for the NH 3 -SCR of NO x. • The NO conversion was strongly related to the FeWO 4 species. • The iron-tungsten catalysts prepared by grinding leads to increased Lewis and Brønsted acid sites and proper redox property. • Grinding method was simple and environmentally friendly. A series of iron-tungsten composite oxides catalysts prepared by grinding methods (FW-GR), incipient impregnation (FW-IM), sol–gel (FW-SG) and microemulsion (FW-ME) methods were used for selective catalytic reduction of NO by NH 3 (NH 3 -SCR). The SCR activity was significantly depended on the preparation method, the NO conversions over different catalysts were following the order of FW-GR > FW-SG > FW-ME > FW-IM. The results indicated that the NO conversion was strongly related to the FeWO 4 species. It also discovered that the catalyst with higher specific surface area, surface Fe2+ content, surface adsorbed oxygen species, redox potential, surface acidic sites and acidic strength showed better NO reduction activity among all catalysts. In situ DRIFTS results revealed that the main reaction mechanisms of iron-tungsten catalysts were "L-H" at low temperature and "E-R" at high temperature. The SCR reaction over FW-GR sample involved the formation of NH 2 intermediate and subsequent reduction by NO, while the formation of NH 4 NO 3 species over FW-IM was easily transformed into N 2 O species. [ABSTRACT FROM AUTHOR]

FeOx, TiO2, and Fe–Ti–Ox catalysts were synthesized and used in the catalytic hydrolysis of hydrogen cyanide (HCN). Nearly 100% HCN conversion was achieved at 250 °C over the Fe–Ti–Ox catalyst. TiO2 rutile was detected over TiO2, but not over Fe–Ti–Ox, which suggested that the interaction between Fe and Ti species could inhibit the TiO2 phase transition. Furthermore, the interaction between Fe and Ti species over Fe–Ti–Ox could promote the selectivity of NH3 and CO. The mechanism of hydrolysis of HCN over FeOx, TiO2, and Fe–Ti–Ox can be given as follows: HCN + H2O → methanamide → ammonium formate → formic acid → H2O + CO. [ABSTRACT FROM AUTHOR]

The CuO-MnO x catalysts annealed at different temperatures were prepared and applied for catalytic oxidation of toluene. It was found that with the increase of annealing temperature, the toluene conversion improved initially but then reduced. The catalyst annealed at 500 °C showed the best toluene oxidation performance, and T 100 was only 230 °C. The results of XPS, Raman and H 2 -TPR proved that the O latt /O ads ratio and the synergistic effect were enhanced with annealing temperature at 300–500 °C, while a slight decline was observed beyond 500 °C. Thereby, abundant lattice oxygen and strong synergistic effect between CuO and MnO x in CM-500 contributed to its superior toluene oxidation performance. In addition, a mechanism pathway was proposed based on the in-situ DRIFTS results. The initial step was the adsorption of toluene on catalyst, then the benzoic acid was rapidly converted to phenol and maleate in the presence of O 2 , then the intermediates were further oxidized to CO 2 and H 2 O by reacting with the supplementary surface lattice oxygen. The amount of intermediate species on the surface of the catalyst was significantly affected by the annealing temperature, and the most surface oxygen species and oxygen vacancies were observed on CM-500. Toluene could convert to benzoic acid under anaerobic conditions, and then react with lattice oxygen on oxygen vacancies in the presence of O 2 , in line with the M-V-K mechanism. Unlabelled Image • The catalyst annealed at 500 °C presented the highest toluene oxidation activity. • The strong synergy facilitated the generation of surface lattice oxygen. • Surface lattice oxygen participated directly and dominantly in toluene oxidation. • Surface lattice oxygen could be replenished by gaseous oxygen. [ABSTRACT FROM AUTHOR]

The HSiW(x)/Ce‐Fe catalysts were used to research the effect of silicotungstic acid contents on the catalytic activity in the selective catalytic reduction of NOx with NH3. Doping different contents of silicotungstic acid affected surface species and redox property as well as the catalytic activity. With the increasing amount of HSiW (x = 5%, 10% and 20%), the redox reaction between Fe3+/Fe2+ and Ce4+/Ce3+ enhanced, which could improve the ratio of Ce3+ and Fe3+. And then, more Ce3+ increased the ratio of chemisorbed oxygen (Oα). Besides, the type and strength of acid sites over HSiW(x)/Ce‐Fe was affected by the HSiW contents. These factors facilitated the catalytic performance. Thus, the NOx conversion of HSiW(x)/Ce‐Fe(x = 20%) was higher than 90%, which maintained in a wide temperature range between 200 and 400 °C. [ABSTRACT FROM AUTHOR]

The promoting effects of WO 3 on RuO 2 -Fe 2 O 3 catalyst were systematically investigated for the selective catalytic oxidation of ammonia to nitrogen. It was found that the introduction of 5 wt.% WO 3 led to a dramatic promoting effect on the high-temperature N 2 selectivity of RuO 2 -Fe 2 O 3 catalyst, giving 100% NH 3 conversion at 250 °C and 94% N 2 selectivity at a high temperature of 400 °C. In depth analysis using XRD, Raman and H 2 -TPR revealed that the addition of WO 3 into the RuO 2 -Fe 2 O 3 catalyst could strongly inhibit the crystallinity of Fe 2 O 3 and decrease the reducibility of RuO 2 -Fe 2 O 3 catalyst, which were related to the strong interaction between WO 3 and Fe 2 O 3 . Moreover, in situ DRIFTS studies illustrated that the ammonia oxidation over 1RuO 2 -5WO 3 -Fe 2 O 3 catalyst followed the iSCR mechanism, involving the oxidation of NH 3 into NO species and the reaction of -NH 2 with in situ-formed NO to form N 2 . The introduction of WO 3 not only promoted the formation of more acid sites on the catalyst surface but also restrained the formation of nitrate species at high temperature, with few NO x formed, which contributed to the high N 2 selectivity. [ABSTRACT FROM AUTHOR]

A series of CeO 2 –ZrO 2 –WO 3 (CZW) catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction (SCR) of NO with NH 3 over a wide temperature of 150–550°C. The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H 2 O. The fresh catalyst showed above 90% NO x conversion at 201–459°C, which is applicable to diesel exhaust NO x purification (200–440°C). The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures (below 300°C), while the activity was notably enhanced at high temperature (above 450°C). The aged CZW catalyst (hydrothermal aging at 700°C for 8 hr) showed almost 80% NO x conversion at 229–550°C, while the V 2 O 5 –WO 3 /TiO 2 catalyst presented above 80% NO x conversion at 308–370°C. The effect of structural changes, acidity, and redox properties of CZW on the SCR activity was investigated. The results indicated that the excellent hydrothermal stability of CZW was mainly due to the CeO 2 –ZrO 2 solid solution, amorphous WO 3 phase and optimal acidity. In addition, the formation of WO 3 clusters increased in size as the hydrothermal aging temperature increased, resulting in the collapse of structure, which could further affect the acidity and redox properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • (NH 4) 2 SO 4 was used instead of liquid H 2 SO 4 to introduce SO 4 2− into V 2 O 5 /CeO 2 ; • NO x conversion is over 95 % at 225–400 °C on 2 %SO 4 2−- V 2 O 5 /CeO 2 ; • The introduction of SO 4 2− enhanced Brønsted acid sites and the formation of polymeric vanadyl species; • The NH 3 -SCR reaction over 2 %SO 4 2−-V 2 O 5 /CeO 2 followed the Langmuir-Hinshelwood and Eley-Rideal routes concurrently. Ceria-supported vanadia (VO x /CeO 2) catalyst has been extensively investigated in the field of NO x selective catalytic reduction with NH 3 (NH 3 -SCR) but is limited in practical application owing to its poor sulfur resistance and high-temperature activity. Herein, a series of SO 4 2− modified V 2 O 5 /CeO 2 catalysts were fabricated to improve the overall catalytic performance. The 2 %SO 4 2−-V 2 O 5 /CeO 2 catalyst exhibited above 95 % NO x conversion, 90 % N 2 selectivity in the temperature range of 225–400 °C and excellent SO 2 + H 2 O tolerance, which was much better than V 2 O 5 /CeO 2 catalyst. Characterization results showed that the introduction of SO 4 2− over V 2 O 5 /CeO 2 increased the Ce3+/(Ce3++ Ce4+) ratio to promote the formation of oxygen vacancies and promoted the generation of more conducive polymeric vanadyl species. The synergistic effect of the redox sites and acid centers provided moderate redox property and enhanced surface acidity, thus improving the adsorption of NH 3 and inhibiting the over-oxidation of NH 3 that occurs on V 2 O 5 /CeO 2. In-situ DRIFTS indicated that the NO x reduction over V 2 O 5 /CeO 2 and 2 %SO 4 2−-V 2 O 5 /CeO 2 followed the Langmuir-Hinshelwood and Eley-Rideal routes concurrently. This study can expound the reasonable design of vanadium-based catalysts for efficient NO x reduction in industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • α-MnO 2 catalysts with different O v concentration were fabricated by a morphology strategy. • MnO 2 -D presented superior catalytic activity and durability than MnO 2 -P. • MnO 2 -D presented a lower oxygen vacancy formation energy (0.69 eV) than MnO 2 -P (1.59 eV). • A bidentate and tridentate carbonate pathway was involved in MnO 2 -D. The engineering defect such as oxygen vacancies over catalysts surface were essential for obtaining superior performance. Herein, two α-MnO 2 (MnO 2 -D and MnO 2 -P) with different O V concentration were facilely fabricated through a morphology strategy to catalyze CO oxidation. Typically, the T 90 value (∼180 °C) of MnO 2 -D with more O v concentration was significantly lower than that (∼250 °C) of MnO 2 -P and this optimized sample also presented superior durability (stable at 180 °C for 100 h). Various surface and structural characterizations including XPS, EPR and TEM, demonstrated that MnO 2 -D possessed plentiful defective Mnδ+-O V active structures, which could serve as catalytically activated sites for oxygen molecular via a MvK mechanism. Additionally, the proportion of surface adsorbed oxygen over MnO 2 -D (27.6 %) was higher than that of MnO 2 -P (17.7 %) from O 2 -TPD results. DFT calculation results further indicated that a remarkably lower formation energy of O V was observed over MnO 2 -D (0.69 eV) than MnO 2 -P (1.59 eV), firmly favoring the oxygen activation. According to in situ DRIFTS results, the bidentate and tridentate carbonate pathways were mainly involved over MnO 2 -D during oxidation. This work provided a facilely constructed defective Mnδ+-O V active structures over MnO 2 -based catalysts. [ABSTRACT FROM AUTHOR]

The ion-exchanged Nd3+ significantly enhances the deNO x activity and low-temperature hydrothermal aging stability of Cu/SAPO-34 by stabilizing the zeolite framework and isolated Cu2+ ions. The NO x reaction rate of Cu/Nd-S-F is faster than that of Cu/S-F because of the formation of more active Cu2+ ions. [Display omitted] • The Nd-doping enhances the deNO x activity and low-temperature (70 °C) hydrothermal stability of Cu/SAPO-34 catalyst. • Cu/SAPO-34 exhibits poor low-temperature hydrothermal stability. • The active Cu2+ ions in Cu/SAPO-34 are partly transformed into unactive CuO under hydrothermal aging at 70 °C. • Nd3+ stabilizes the zeolite framework and isolated Cu2+ and combines with PO 4 3- to form NdPO 4. Designing a highly efficient and cost-effective deNO x catalyst for curbing NO x emission in diesel vehicle exhaust is highly desired but challenging. Herin, a Nd-promoted Cu/SAPO-34 (Cu/Nd-S) catalyst with superior NO x reduction efficiency and low-temperature hydrothermal stability was proposed. The NO x conversion of fresh Cu/Nd-S-F at 200 °C was improved to 86.1 % compared to fresh Cu/S-F (78.1 %). XRD and H 2 -TPR results revealed that Nd3+ ions filled the defect sites of zeolites and combined with P species to form NdPO 4 , thus stabilizing the zeolite framework and maintaining the stability of active copper species. The interaction between Nd3+ ions and Cu2+ ions protected the active copper species (Cu2+-2Z and [Cu(OH)]+-Z) from the attack of low-temperature (70 °C) moisture. However, Cu/SAPO-34 suffered from the rapid and irreversible deterioration under 70 °C of water bath, leading to the loss of surface Brønsted acid sites (Al-(OH)-Si) and isolated Cu2+ ions, so aged Cu/S-70 exhibited inferior NO x conversion. Meanwhile, in situ DRIFTS transient experiments elaborated that the NH 3 -SCR reaction over Cu/SAPO-34 and Cu/Nd-SAPO-34 catalysts obeyed the E-R and L-H routes simultaneously. To be noted, the Nd-doping engineering afforded a promising strategy for boosting the low-temperature hydrothermal stability of Cu/SAPO-34 catalysts for the practical application of NO x removal. [ABSTRACT FROM AUTHOR]

A series of Fe modified hydrotalcite-derived Ni-based catalysts (Ni 3 Fe x -calc) were synthesized to evaluate the effect of Fe on CO 2 methanation performance over Ni 3 -calc catalyst. The results showed that Ni 3 –Fe 0.5 -calc had superior catalytic activity with 78% CO 2 conversion rate at 200 °C. The addition of moderate amount of Fe can effectively improve the reducibility, enrich the medium basic sites of Ni 3 -calc catalyst, and further facilitate the adsorption and activation of CO 2. This resulted in the outstanding low-temperature CO 2 methanation activity, as well as the enhanced resistance of carbon deposition. In-situ DRIFTS results indicated that the CO 2 methanation reaction mechanism involved a progressive hydrogenation of carbonate and formate species to methane route. The formate species was the main intermediates during CO 2 methanation. The introduction of Fe could significantly accelerate the hydrogenation rate of carbonates and formate species. • Fe-modified improves catalytic performance over the Ni-based catalysts for low-temperature CO 2 methanation. • Introducing Fe can significantly improve the adsorption of CO 2 due to the increase in basic sites. • The hydrogenation rate of carbonates and formate species is accelerated with Fe modification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reduced Ni-MgO catalysts were characterized by Ni0 species stabilized by Ni2+. • High crystalline MgO support can retain more Ni0 species on the surface. • The moderate MSI exhibits improved spatial distribution of Ni0. • The HCO 2 * converted rapidly at the rich Ni0/Ni2+ site can promote the activity. To deeply explore the key role of Ni species over highly active Ni-MgO catalysts for the dry reforming of methane (DRM) is still a great challenge. This study presents a Ni-MgO catalyst with a high proportion of active Ni0 species stabilized by Ni2+ (Ni0/Ni2+ site) by electron transfer from Ni0 to Ni2+, which demonstrates remarkable DRM performance, even operating at a high temperature of 750 °C for 200 h. Compared with the Ni-MgO catalysts with strong interaction between Ni species and MgO, the Ni-MgO catalyst with moderate interaction between Ni species and highly crystalline MgO exhibits superior thermal stability, resulting in the high proportion Ni0/Ni2+ sites and the improved spatial distribution of Ni0. TPSR results show that the activation temperatures of CH 4 were obviously decreased (∼100 °C) over the Ni-MgO catalyst with abundant Ni0/Ni2+ sites. Interestingly, the abundant mid/strong base sites that existed on Ni-MgO with a high proportion of Ni0/Ni2+ sites can restrain the carbon deposition due to the increased CO 2 adsorption ability in the DRM reaction. The formate (HCOO*) pathway was validated by in situ DRIFTS, indicating that the plentiful Ni0/Ni2+ sites promoted the activation of HCO 3 * into HCOO*, and then generated H 2 and CO. This study provides a comprehensive understanding of the relationship between the Ni species on MgO and the reaction pathway in dry reforming of methane. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ordered mesoporous phosphotungstate support for NH 3 -SCR catalyst. • Fe/NPW catalyst exhibits high NO conversion and favorable SO 2 + H 2 O tolerance. • The highly dispersed Fe species on acid support enhances the synergistic effect of redox sites and acid centers. • High W5+/(W5+ + W6+) and Fe2+/(Fe2+ + Fe3+) ratios and easy electron transfer accelerate NH 3 -SCR redox cycle. • The synergistic effect of redox sites and acid center potentiates adsorption and activation of NH 3 on Lewis sites. An ordered mesoporous phosphotungstate loading dispersed iron oxide is obtained as Fe/NPW catalyst for NH 3 -SCR. The Fe/NPW catalyst exhibits higher than 90 % NO x conversion at 250–475 °C and excellent SO 2 tolerance since the ordered and uniform mesoporous structure favors the diffusion of reactants and dispersion of active ingredients. Moreover, the high dispersion enhances the interfacial interaction between Fe and W species on Fe/NPW catalyst, increasing the W5+/(W5++W6+) ratio to promote the formation of oxygen vacancies and surface adsorbed oxygen (O α). Additionally, the synergistic effect of the redox sites and acid centers enabled by the dispersed iron oxide on the ordered mesoporous phosphotungstate provides moderate redox property and enhanced surface acidity. It improves the adsorption of NH 3 and inhibits the over-oxidation of NH 3 that occurs on Fe 2 O 3 surface. Furthermore, the in-situ DRIFTS results show that the abundant surface acidity of phosphotungstate can suppress the formation of nitrate species. The introduction of Fe provides redox sites for reaction and enhances the thermal stability and activation of ammonia species adsorbed on Lewis acid sites, facilitating the Eley-Rideal pathway on Fe/NPW catalyst. The results of this work reveal that the synergistic effect of redox sites and acid centers on the ordered mesoporous Fe/NPW catalyst contributes to the excellent performance in the NH 3 -SCR process. [ABSTRACT FROM AUTHOR]

[Display omitted] • SO 4 2--FeO x -Nb 2 O 5 catalyst exhibits the best activity over the whole temperature range. • Niobium modifies the electronic structure and alleviates the reducibility of catalyst. • Sulfation provides more Brønsted acid sites for surface ammonia adsorption. • Niobium promotes the binding of iron to sulfate to form redox acid sites. A series of iron-based composite oxide catalysts, modified with acid and niobium, were produced for the purpose of selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) via co-precipitation. The obtained SO 4 2--FeO x -Nb 2 O 5 (S-FeNbO x) catalyst exhibited significantly better SCR performance than the unmodified FeO x catalyst, with a NO x conversion above 90% and N 2 selectivity higher than 95% in the temperature range of 275–450 °C. The characterization results suggest that the addition of Nb not only modifies the electronic structure and alleviates the reducibility but also enhances the surface acidity of the catalysts. The sulfuric acid modification of FeO x -Nb 2 O 5 catalyst promotes the formation of redox-acid sites. The in situ Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFTs) results revealed that the combining sulfuric acid and niobium modifications resulted in a significant increase in the amount of Brønsted acid sites, and also led to a blue shift of the band related to the Lewis acid sites, implying the existence of a synergistic effect of the two modification methods. The creation of redox-acid sites significantly enhances the adsorption and activation capacity of NH 3 on the catalyst surface. These results suggest that the NH 3 -SCR reaction to primarily follow the Eley-Rideal (E-R) mechanism on the catalyst. [ABSTRACT FROM AUTHOR]

Graphical abstract The hydrothermal stability of Cu-SAPO-34 was significantly enhanced by the addition of Ce or La. The introduction of Ce or La effectively mitigated the dealumination and restrained the aggregation of copper species. The hydrothermal treatment cut off the "E-R" reaction route over the Cu-SAPO-34 and opened the new reaction pathway ("L-H" mechanism) over the Cu/La-SAPO-34. Highlights • Adding Ce or La into Cu-SAPO-34 effectively enhanced the hydrothermal stability. • Cu2+ increased over Cu/La-SAPO-34 after aging and affected low-temperature activity. • The addition of Ce or La restrained the aggregation of Cu species and dealumination. • The introduction of Ce or La stabilized the surface acid sites of Cu-SAPO-34. • Hydrothermal aging changed SCR reaction route of Cu-SAPO-34 and Cu/La-SAPO-34. Abstract The effect of Ce or La on the hydrothermal stability of Cu-SAPO-34 catalyst was evaluated by the selective catalytic reduction of NO x by ammonia (NH 3 -SCR) reaction after hydrothermal aging at 700 °C in 10 vol% H 2 O/air for 10 h. The hydrothermal stability of Cu-SAPO-34 was dramatically enhanced by introducing small amount Ce or La into Cu-SAPO-34. More than 93% NO x conversion was maintained over the aged Ce or La modified Cu-SAPO-34 at 175–350 °C, while extremely poor NH 3 -SCR activity was obtained over the aged Cu-SAPO-34. In situ diffuse reflection infrared Fourier transform spectrum (DRIFTS) results illustrated that the hydrothermal treatment cut off the intrinsic "E-R" reaction route over the Cu-SAPO-34 and opened the new reaction pathway ("L-H" mechanism) over the La modified Cu-SAPO-34 catalyst. Additionally, the introduction of Ce or La effectively mitigated the dealumination progress and restrained the aggregation of copper species over Cu-SAPO-34 during the hydrothermal aging, further maintaining the relatively large specific surface area and uniform pore size distribution. Meanwhile, the incorporation of Ce or La enhanced the redox property and stabilized the surface acid sites of Cu-SAPO-34, further facilitating the adsorption and activation of reactants. [ABSTRACT FROM AUTHOR]

The effect of different pH values (8, 9, 10 and 11) on the catalytic activity over CeSiW catalysts was investigated for the selective catalytic reduction of NO by NH3. CeSiW-9 showed a remarkable higher NOx conversion. The strongest interaction was observed between silicotungstic acid and CeO2 over CeSiW-9, resulting in the improvement of redox ability and surface acidity, which could increase the catalytic activity. The superior catalytic performance of the CeSiW-9 catalyst was attributed to the favored pore structures, excellent redox ability and the abundance of surface acid sites, which depended on pH values in the preparation process of CeSiW catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • γ-Al 2 O 3 supported Pt single atoms tuned by barium was precisely fabricated. • The optimized catalyst presented an outstanding catalytic activity and durability. • The electron-rich Ptδ− and available oxygen sites have a synergistic effect. • This synergistic effect gives it superior performance. • The reaction followed the modified L-H mechanism. The in-depth identification of the catalytic active-sites for low-temperature CO oxidation over single atom catalysts was essential for high-efficiency catalyst design but faced greatly challenging. Herein, γ-Al 2 O 3 supported Pt single atoms tuned by barium species (Pt-Ba/γ-Al 2 O 3) was precisely fabricated to contribute to this issue. This catalyst with 0.1 wt% Pt can completely remove CO at a temperature as low as ∼ 120 °C and further display an outstanding sulfur-resistance durability performance, which outperformed those of most Pt-based reported catalysts. Various characterizations such as AC HAADF-STEM, in situ DRIFTS, and DFT calculations were conducted to reveal the concrete roles of Pt natures and active oxygen species. The results demonstrated that in contradiction of poisoning of Pt (sub)nanometre structures by CO over Pt/γ-Al 2 O 3 counterpart, the electron-rich Ptδ− single-atoms formed by the electron donation from barium species and plentiful available oxygen species over Pt-Ba/γ-Al 2 O 3 synergistically promoted catalytic low-temperature CO oxidation and thereby contributed primarily to its superior performance. Typically, the electron-rich Ptδ− single-atoms provided the main sites for CO activation and the available oxygen species were the active centers for O 2 activation. The CO oxidation reaction followed the modified L-H mechanism rather than the conventional L-H one. Findings could guide the design of effective catalysts for the fundamental and industrial catalytic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of PdO σ /Fe 1-x W x O y catalysts was prepared and used to catalyze CO oxidation. • PdO σ /Fe 0.6 W 0.4 O y showed excellent sulfur resistance at relatively low temperatures. • WO 3 could increase sulfur-resistance by reducing SO 2 adsorption. • PdO 2 (4+) appears to be more resistant to sulfur than PdO (2+). Efficient sulfur-tolerant catalysts for purification in sulfur-containing steel sintering flue gas remain a severe challenge. Herein, a series of Fe 2 O 3 modified by WO 3 -supported PdO σ was fabricated to make progress in this issue. WO 3 decoration decreases Pd dispersion but significantly enhances the sulfur resistance of PdO σ /Fe 2 O 3 for CO catalytic oxidation. Typically, at an SO 2 concentration as high as 1000 ppm, the optimal PdO σ /Fe 0.6 W 0.4 O y can keep its activity with a CO conversion of 90% even at relatively low temperatures (175 °C) for 20 h, which was superior to most reported catalysts. As evidenced by systematical surface properties and kinetic analysis, this accepted sulfur tolerance was closely related to the enhanced amount of surface acid sites and the formation of a new phase of FeWO 4 from the strong interaction of FeO x and WO 3 , which could suppress SO 2 adsorption and decrease the deposition of the undesirable sulfate (S6+). Additionally, PdO 2 (4+) appears to be more resistant to sulfur than PdO (2+), probably due to the latter palladium species being more likely to react with sulfur. Also, WO 3 modification induced the chemical state of sulfur component changing from S6+ to S4+, thereby preserving PdO 2 (4+) catalytic activity species and showing remarkable performance of sulfur tolerance. [ABSTRACT FROM AUTHOR]

The solid superacid TiO 2 -ZrO 2 -SO 4 2− -supported 20 wt.% CeO 2 catalyst (20CeO 2 /Ti-Zr-S) was synthesized for selective catalytic reduction of NO with NH 3 (NH 3 -SCR). The NH 3 -SCR performance was significantly enhanced by the construction of strong acid sites on the surface of 20CeO 2 /Ti-Zr-S and over 96% NO conversion was obtained at 225–425 °C. Meanwhile, the strong interaction between solid superacid and CeO 2 resulted in excellent redox property and abundant surface oxygen species. Furthermore, the NH 3 -SCR reaction over 20CeO 2 /Ti-Zr-S catalyst mainly followed the Langmuir-Hinshelwood mechanism at low-temperature (250 °C). The M-NO 2 (M = Ce, Ti, Zr) nitrate compounds, monodentate and bridging nitrates were the crucial intermediates in Langmuir-Hinshelwood mechanism. In addition, amide (–NH 2 ) species were available at 350 °C over 20CeO 2 /Ti-Zr-S catalyst, which facilitated the high-temperature NH 3 -SCR activity via Eley-Rideal pathway. [ABSTRACT FROM AUTHOR]

[Display omitted] • The addition of urea enhances the K 2 O resistance of FeO x -WO 3 catalyst. • Urea could induce the K 2 O to aggregate on FeO x -WO 3 catalyst surface. • K 2 O mainly binds to WO 3 species to protect Fe 2 O 3 active species. • K/FeO x -WO 3 (urea) catalyst retains more Lewis acid sites. The improvement of alkali tolerance of de-NO x catalysts remains an immense challenge for selective catalytic reduction (SCR) of NO by NH 3. In this work, NO x removal efficiency was nearly retained in the presence of potassium over FeO x -WO 3 (FW) catalysts via protecting iron active species using different template agents. Typically, FW using urea (FW-(urea)) as template agent showed superior de-NO x performance after being poisoned by potassium (K/FW-(urea)). Urea could promote the facile binding of potassium with WO 3 , which acted as alkali-poisoning sites so that iron active species were reserved to a great extent. Additionally, potassium species tended to be aggregated over K/FW-(urea) and thus a lot of iron active sites could be exposed. Besides, K/FW-(urea) catalyst has higher surface acidity, superior redox ability, stronger interaction of WO 3 with Fe 2 O 3 , and more surface adsorbed oxygen compare with other parallel poisoned samples. This is the reason for the remarkable ability of potassium resistance over K/FW-(urea). The strategy of template regulation could offer a novel route for maintaining considerable NH 3 -SCR performance in the presence of alkali. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-CeZrAl with unique surface properties presented superior catalytic performance in DRM. • The superior catalytic activity was due to rich oxygen vacancies and active oxygen species. • The optimum active site-support interaction resulted in the high dispersion of Ni active sites. Ni-CeZrAl catalyst prepared by a facile co-precipitation method was applied for dry reforming of methane (DRM). DRM catalytic performance of Ni-CeZrAl presented the highest methane conversion of 38.1% at 650 °C, and remained stable at 700 °C for 50 h without deactivation. Kinetic investigations further showed the lowest apparent activation energy (34.5 kJ/mol) of DRM reaction and the highest CH 4 TOF value (7.62 × 10−2 s−1) at 640 °C over Ni-CeZrAl. The surface properties of these samples were systematically characterized by H 2 -chemisorption, H 2 -TPR, XPS, Raman, CO 2 -TPD and O 2 -TPD. It can be found that the superior catalytic behaviors of Ni-CeZrAl catalyst were closely associated with its high dispersion of surface Ni0 active phase. More importantly, ample oxygen vacancies and basic sites favored the formation of disordered carbon and effectively protected the Ni active sites. The inferior activity in Ni-CeAl was due to the formation of NiAl 2 O 4 inactive spinel phase. Similarly, weak interaction and fewer active sites resulted in the inferior catalytic performance of Ni-CeZr. Hence, unique surface properties of Ni-CeZrAl with the optimum active site-support interaction were responsible for considerable performance. This work provides a guidance to design high performance Ni-based catalysts for DRM. [ABSTRACT FROM AUTHOR]

The unsaturated cations (Fem+ and Wn+) about surface defect gave rise to form more Lewis acid sites, and the O-W-O and W-O-W in connection with hydrated tungsten species led to the formation of Brønsted acid sites. The calcination at 500 °C for iron-tungsten catalyst was accompanied by the coexistence of surface defect and FeWO 4 or WO 3 species with an optimal ratio, prompting its best active window with more than 90% NO x conversion at 220–500 °C. The reaction intermediate between NO 3 − and NH 2 formed on the surface of FeO x -WO 3 catalyst was such a crucial factor in improving the reaction performance of NH 3 -SCR and the difference of N 2 selectivity. • The surface defect and surface acidity of FeO x -WO 3 catalysts were efficaciously regulated via thermal treatment. • The unsaturated cations about surface defect and the O-W-O and W-O-W in connection with hydrated tungsten species enhanced the surface acidity. • Formed NO 3 − and NH 2 had an effect on the NH 3 -SCR performance and N 2 selectivity. Iron-tungsten composite oxide catalysts have been prepared using a no-water grinding method followed by calcination from 400 to 800 °C. Treatment from 400 °C to 800 °C led to the crystallinity increase and weaker interaction between Fe and W. The catalyst calcined at low temperature (400 °C) obtained ample lattice defect, more surface Fe2+ species and surface oxygen and showed the greatest low-temperature catalytic activity. At high calcination temperature, less surface oxygen-vacancies and weak reducibility of samples were found and correspond to decreased catalytic properties. The calcination at 500 °C for iron-tungsten catalyst was accompanied by the coexistence of surface defect and FeWO 4 or WO 3 species with an optimal ratio, prompting its best active window with more than 90% NO x conversion at 220–500 °C. More specially, the unsaturated cations (Fem+ and Wn+) about surface defect gave rise to form more Lewis acid sites, and the O-W-O and W-O-W in connection with hydrated tungsten species led to the formation of Brønsted acid sites. The reaction intermediate between NO 3 − and NH 2 formed on the surface of FeO x -WO 3 catalyst was such a crucial factor in improving the reaction performance of NH 3 -SCR and the difference of N 2 selectivity. [ABSTRACT FROM AUTHOR]

A series of bi-metallic Pt–Pd-SBA-15 catalysts which promoted the dispersion of Pt–Pd by surface functionalization of SBA-15 were prepared and applied for toluene oxidation. We found that PVP-assisted Pt–Pd-SBA-15 exhibited the minimal average particle size (4.6 nm) and the highest Pt0/Ptn+ (50.6%) among all the catalysts decorated with polyvinylpyrrolidon (PVP), citric acid and ethylenediamine, respectively. Kinetic study revealed that the Ea of all catalysts decreased accompanied with catalytic activity in the following order: Pt–Pd-SBA-15-PVP (83.5 kJ/mol) < Pt–Pd-SBA-15-citric (100.1 kJ/mol) < Pt–Pd/SBA-15 (110.7 kJ/mol) < Pt–Pd-SBA-15-(en) 2 (150.6 kJ/mol). Based on the above analyses, a conclusion could be drawn that PVP-induced dispersion process improved significantly the surface Pt0/Ptn+ (50.6%) ratio and reduced the particle size of Pt–Pd nanoparticles, which enhanced the activity of toluene oxidation. Furthermore, in-situ DRIFTS studies showed that benzoic acid and maleic acid were typical intermediates produced during the catalytic combustion of toluene. Wherein, toluene could be oxidized to benzoic acid by positively charged Pt and Pd in the absence of O 2. On the other hand, toluene was oxidized to maleic acid under an aerobic atmosphere. Image 1 • Surface functionalization of SBA-15 promoted the dispersion of Pt–Pd nanoparticles and surface Pt0/Pt total. • Benzoic acid and maleic acid were typical intermediates during the catalytic combustion of toluene. • The destruction and further oxidation of aromatic ring could be accelerated under an aerobic atmosphere. [ABSTRACT FROM AUTHOR]

• WO 3 -FeO x catalysts were synthesized using a novel and facile solvent-free method. • The NO x removal efficiency of 0.3W-Fe was nearly 100 % in a wide temperature range of 225−500 °C. • The strong interaction between WO 3 and Fe 2 O 3 induced the formation of Fe 3 O 4. • The interaction between WO 3 and Fe 2 O 3 promoted the adsorption of NH 3 and NO x. • The NH 3 -SCR reaction over WO 3 -FeO x followed the L-H and E-R mechanism synchronously. WO 3 -FeO x catalysts with various WO 3 contents were synthesized through a facile solvent-free method, satisfying the selective catalytic reduction of NO (NH 3 -SCR). Strikingly, the optimum 30 %WO 3 -FeO x catalyst with the largest surface area exhibited the most outstanding catalytic activity, achieving the nearly 100 % NO x removal efficiency in a wide temperature window between 225−500 °C, which was better than that of Fe-W series catalysts reported in other studies. In addition, Raman and XPS results proved that the introduction of WO 3 altered the electronic environment of Fe 2 O 3 , inducing the formation of Fe 3 O 4 (Fe2+) and surface adsorbed oxygen. In situ DRIFTS demonstrated that the interaction between WO 3 and Fe 2 O 3 not only promoted the adsorption capacity of NH 3 on the catalyst, but also contributed to the formation of adsorbed NO x species. NO x reduction reaction on WO 3 -FeO x catalyst proceeded via the Eley-Rideal and Langmuir-Hinshelwood mechanism synchronously. All of these factors, jointly, accounted for the superior catalytic activity and N 2 selectivity of WO 3 -FeO x catalysts. [ABSTRACT FROM AUTHOR]

A series of Fe–Ti-O x catalysts calcined at different temperatures (signed as Fe–Ti- x , and x symbolized the calcination temperature of 300, 400, 500, 600 and 700 °C, respectively) were prepared and studied for the catalytic hydrolysis of HCN in the presence of H 2 O. The results implied that Fe–Ti-4 (the calcination temperature was 400 °C) showed the best catalytic hydrolysis efficiency of HCN and the abundant productions (CO and NH 3). With the calcination temperature increasing, the catalytic hydrolysis of HCN activity decreased dramatically, which was related to the reduction of specific surface areas and redox property, the formation of rutile TiO 2 and decline in quantity of Fe2+ species. Besides, Fe–Ti-O x catalysts with amorphous states of TiO 2 could enhance catalytic hydrolysis of HCN, which depended on the effect of calcination temperature during the preparation process of Fe–Ti-O x catalysts. Fe–Ti-O x catalysts prepared by self-assembly method were investigated in the catalytic hydrolysis of HCN. The formation of pseudobrookite Fe 2 TiO 5 over Fe–Ti-O x possessed more amounts of Fe2+ species, which accelerated the HCN catalytic hydrolysis. Furthermore, the amounts of Fe2+ species contributed to the production of NH 3. Besides, Fe–Ti-O x catalysts with rutile TiO 2 could inhibit the catalytic performance. Image 1 • Rutile TiO 2 over Fe–Ti-O x inhibited the catalytic hydrolysis of HCN. • Formation of Fe 2 TiO 5 over Fe–Ti-O x improved the HCN catalytic hydrolysis. • More amounts of Fe2+ species over Fe–Ti-O x improved the selectivity of NH 3 and CO. • Catalytic hydrolysis of HCN over Fe–Ti-O x depended on calcination temperatures. [ABSTRACT FROM AUTHOR]