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CuO@TiO2 core–shell nanostructure catalyst with CuO core and TiO2 shell was prepared by a two-step method and then used in NH3-SCR reaction. FE-SEM, TEM and element mapping were used to investigate the morphologies of the sample. Their results indicated CuO nanorods were coated with TiO2 and thus forming a core–shell nanostructure. According to the results of N2 adsorption–desorption, XRD, Raman, XPS, NH3-TPD, H2-TPR and in situ DRIFTS, the core–shell nanostructure would benefit the formation of better redox ability, more oxygen vacancies, more acid sites and abundant adsorbed NOx species on the catalyst. Thus, the core–shell nanostructure catalyst presented significantly higher activity than pure CuO and TiO2. NH3-SCR reaction on CuO@TiO2 core–shell catalyst should follow both Eley–Rideal (E-R) mechanism and Langmuir-Hinshewood (L–H) mechanism. These findings may promote the development of the new effective non-vanadium-based SCR catalysts.

CuSO4/TiO2 catalysts with high catalytic activity and excellent resistant to SO2 and H2O, were thought to be promising catalysts used in Selective catalytic reduction of nitrogen oxides by NH3. The performance of catalysts is largely affected by calcination temperature. Here, effects of calcination temperature on physicochemical property and catalytic activity of CuSO4/TiO2 catalysts were investigated in depth. Catalyst samples calcined at different temperatures were prepared first and then physicochemical properties of the catalyst were characterized by N2 adsorption-desorption, X-ray diffraction, thermogravimetric analysis, Raman spectra, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption of NH3, temperature-programmed reduction of H2 and in situ diffuse reflectance infrared Fourier transform spectroscopy. Results revealed that high calcination temperature had three main effects on the catalyst. First, sintering and anatase transform into rutile with increase of calcination temperature, causing a decrement of specific surface area. Second, decomposition of CuSO4 under higher calcination temperature, resulting in disappears of Bronsted acid sites (S–OH), which had an adverse effect on surface acidity. Third, CuO from the decomposition of CuSO4 changed surface reducibility of the catalyst and favored the process of NH3 oxidation to nitrogen oxides (NOx). Thus, catalytic activity of the catalyst calcined under high temperatures (≥600°C) decreased largely.

In this study, the deactivation of commercial V2O5-WO3/TiO2 selective catalytic reduction catalysts by Pb was discussed primarily, and the combined promotive effects of SO2 and HCl on Pb-poisoned V2O5-WO3/TiO2 catalysts were studied. The results show that the treatment with SO2 and HCl markedly improves the NOx conversion of Pb-poisoned catalysts. SO2 and HCl react with Pb chemisorbed on V2O5, which increases effectively the ratio of V5+ and active oxygen species and the amount of acid sites.

Shape effects of nanocrystal catalysts in different reactions have attracted remarkable attention. In the present work, three types of α-Fe2O3 oxides with different micromorphologies were rationally synthesized via a facile solvothermal method and adopted in deep oxidation of ethane. The physicochemical properties of prepared materials were characterized by XRD, N2 sorption, FE-SEM, HR-TEM, FTIR, in situ DRIFTS, XPS, Mössbauer spectroscopy, in situ Raman, electron energy loss spectroscopy, and H2-TPR. Moreover, the formation energy of oxygen vacancy and surface electronic structure on various crystal faces of α-Fe2O3 were explored by DFT calculations. It is shown that nanosphere-like α-Fe2O3 exhibits much higher ethane destruction activity and reaction stability than nanocube-like α-Fe2O3 and nanorod-like α-Fe2O3 due to larger amounts of oxygen vacancies and lattice defects, which greatly enhance the concentration of reactive oxygen species, oxygen transfer speed, and material redox property. In addition to this, DFT results reveal that nanosphere-like α-Fe2O3 has the lowest formation energy of oxygen vacancy on the (110) facet (Evo (110) = 1.97 eV) and the strongest adsorption energy for ethane (−0.26 eV) and O2 (−1.58 eV), which can accelerate the ethane oxidation process. This study has deepened the understanding of the face-dependent activities of α-Fe2O3 in alkane destruction.

Non-vanadium-based catalysts with high SO2 tolerance are still interesting in selective catalytic reduction of NO by NH3 (NH3-SCR) and SO2 adsorption is the foremost step for the deactivation of catalysts. In order to alleviate the adsorption of SO2, we fabricated a series of rhenium (Re; without stable sulfate) supported TiO2 catalysts and studied their SO2 tolerance for the first time. Owing to suitable surface acidity and reducibility, ReOx/TiO2 catalysts exhibited satisfactory activity in a wide temperature range of 250–350 °C. As expected, experimental results and DFT calculations indicated that SO2 adsorption on ReOx/TiO2 catalysts was rather weak, thus the catalysts performed excellent SO2 tolerance in the NH3-SCR reaction. Moreover, in situ DRIFTS indicated that the NH3-SCR reaction on ReOx/TiO2 catalysts followed the Eley–Rideal mechanism and SO2 had little effect on the reaction mechanism. Our findings should provide new insights into the development of SCR catalysts with high SO2 tolerance.

A series of hierarchical porous carbons (HPCs) with different morphologies and well-developed porosity have been successfully synthesized via a facile and flexible template-free method using hierarchical assembly of polyimide as carbon precursor. Amongst, cornflower-like hierarchical porous carbon (FC4) displays the best CO2 capture property with an adsorption capacity up to 4.05 and 2.87 mmol g−1 at 273 and 298 K, respectively. The excellent CO2 capture capability of FC4 can be owing to the cooperative effect of moderate meso-/macropore channels and abundant framework micropores, which are conducive to diffusion and capture of CO2 adsorbate. Moreover, FC4 shows superior stability and recyclability and CO2 trapping selectivity with CO2/N2 initial and final adsorption ratios of 24 and 6.4, respectively. It can be anticipated that the FC4 is a promising adsorbent in the adsorption and separation of carbon dioxide under actual conditions.

Four kinds of carbon-based adsorbents (micro-mesoporous hybrid carbon nanosphere and N-doped hollow carbon sphere with single-, double- or ruga-shell morphology) with different structural and textural properties were prepared and systematically studied in CO2 capture. All synthesized samples possess high specific surface area (828–910 m2 g−1), large pore volume (0.71–1.81 cm3 g−1), and different micropore contents varied from 2.1% to 46.4%. Amongst, the ordered micro-mesoporous carbon nanosphere (OM-CNS) exhibits the best adsorption performance with CO2 uptake as high as 3.01 mmol g−1 under conditions of 298 K and 1.0 bar, better than most of the reported CO2 adsorbents. The excellent CO2 adsorption capacity of OM-CNS can be reasonably attributed to the synergistic effect of ordered mesopore channels and abundant structural micropores which are beneficial for the diffusion and trapping of CO2 adsorbate. Moreover, the OM-CNS shows excellent CO2 trapping selectivity and superior stability and recyclability, which endow the OM-CNS as a promising and environmental-friendly adsorbent for CO2 capture and separation under practical conditions.

Currently, Pb poisoning of heterogeneous catalysts is considered to be a key area of interest in research involved with industrial NOx reduction. As such, a series of Pb-poisoned V2O5-WO3/TiO2 catalysts were prepared by a wet impregnation method and the influence of SO2 on the performance of these poisoned catalysts for NOx reduction was assessed both experimentally and using theoretical calculations. As expected, the incorporation of Pb in these materials resulted in a significant reduction in their catalytic performance. The conversion of NOx over the Pb-V2O5-WO3/TiO2 catalyst increased from approximately 50% to 90% in presence of SO2 (2000 ppm) at 350 °C. It was postulated that in the absence of SO2, Pb reacts with surface V-OH species, which ultimately results in the destruction of Brønsted acid sites; considered to be crucial for the catalytic conversion of NOx. In the presence of SO2 however, enhanced catalytic activity was observed which was suggested to be a result of the formation of additional Brønsted sites (S-OH) via a surface bidentate sulfate intermediate species. The formation of these species was attributed to the interaction of Pb with SO2 and O2 on the surface of the catalyst. Density functional theory (DFT) calculations based on a monolayer V model on TiO2 (0 0 1) showed that SO2 absorbed selectively onto Pb sites rather than V or Ti oxides. It was subsequently determined that NH3 absorption proceeds through the formation of Pb-N species with Pb atom and H-O with SO2. We believe that the present work provides new insights into the design and application of SCR catalysts with specific relevance for application in flue gas streams which contain high quantities of Pb content.

MnOx oxides with different morphologies (nanowire (MnOx-W), nanocube (MnOx-C), nanorod (MnOx-R), and nanosphere (MnOx-S)) and exposed facets were synthesized via a solvothermal method. The catalytic performance of the synthesized MnOx materials for methyl ethyl ketone (MEK) destruction was investigated. Results show that the activity of MnOx-W with highly exposed {101} facets of Mn3O4 is superior to that of MnOx-C, MnOx-R, and MnOx-S exposing {321} facets of Mn2O3, {110} facets of MnO2, and {101} and {112} facets of Mn3O4, respectively. MEK can be completely mineralized into CO2 at 195 °C over MnOx-W under a relatively high gas hourly space velocity of 37 200 h−1, which is even better than some typical noble metal loaded catalysts. The lowest apparent activation energy of MnOx-W (27.7 kJ mol−1) for MEK destruction also confirms its excellent catalytic activity. Density functional theory (DFT) results reveal that the {101} facets of Mn3O4 have the highest MEK adsorption energy (0.79 eV), which indicates that MEK molecules have a high affinity to adsorb onto the MnOx-W surface, promoting the oxidation process of MEK. In situ DRIFTS and TPSR results indicate that the mineralization of MEK into CO2 over MnOx-W goes through an oxidation route with diacetyl as the primary intermediate. We found that the highly exposed {101} active facets, abundant oxygen vacancies, and excellent low-temperature reducibility are responsible for the superior oxidation performance of MnOx-W. This finding may bring new insights into the designing of highly effective catalysts and has implications for a wide range of reactions not limited to MEK oxidation.

Novel CuMCeOx (M = Y, Eu, Ho, and Sm) trimetal oxide catalysts with developed mesoporosity and an enhanced oxygen migration capability were fabricated by a reproducible self-precipitation approach for the first time. The incorporation of a rare-earth element (especially Y, Eu, and Ho) can increase the reducibility of, and mobility of surface adsorbed oxygen on, a CuCeOx catalyst, which leads to a remarkable increase in catalytic activity in the oxidation of toluene. Among these catalysts, the CuHoCeOx catalyst possesses the highest oxidation activity, with the complete mineralization of toluene at 220 °C at a relatively high GHSV of 50 000 h−1, which is ascribable to the synergetic effect of Ho and the CuCeOx framework, which creates abundant active oxygen vacancies over mixed oxides. Raman spectroscopy and density functional theory (DFT) studies reveal that Ho element is coordinated to two oxygen atoms and occupies the site of a Ce atom, which changes the π-bonding of Ce in the CuCeOx binary oxide and thus leads to the weakening of Ce–O bonds and an enhanced oxygen storage capacity. A possible reaction pathway and a mechanism for the combustion of toluene over a CuHoCeOx sample are proposed by means of in situ DRIFTS and DFT studies, which prove that the toluene oxidation process obeys the Mars–van Krevelen mechanism, with aldehydes and ketones as the primary organic intermediates, before decomposition to CO2 and H2O.

A series of highly active de-NO x catalysts, Eu-modified MnO x -TiO 2 (MnTiEu), was prepared by an inverse co-precipitation method. Their physiochemical properties were investigated by XRD, TEM, EDS, BET, XPS and H 2 -TPR in detail, and their catalytic activities were evaluated by the selective catalytic reduction (SCR) of NO with NH 3 . The results showed that the introduction of Eu with proper amount into MnO x -TiO 2 can effectively restrain the crystallization process of MnO x and TiO 2 , enhance specific surface area, increase the concentration of both surface Mn 4 + and chemisorbed oxygen species, improve the stability of Mn 4 + and Mn 3 + , reduce the amount of surface acid sites, enhance the strength of surface acid sites. The obtained MnTiEu-0.3 catalyst (the molar rate of Eu/Mn was 0.3 and the mole rate of Mn/Ti was 0.1) exhibited a 100% NO x conversion activity in a wide temperature window from 180 to 390 °C and a 100% N 2 selectivity from 120 to 390 °C under a high space velocity of 36,000 h − 1 . Furthermore, MnTiEu-0.3 catalyst presented stronger resistance to concurrent H 2 O and SO 2 poison in comparison with MnO x -TiO 2 catalyst without Eu addition. In - situ DRIFT spectra suggested that NH 3 can be adsorbed on both Lewis and Bronsted acid sites. For MnO x -TiO 2 catalyst, both coordinated NH 3 species on Lewis acid sites and NH 4 + species on Bronsted acid sites can react with gas-phase NO following E-R mechanism. As regards MnTiEu-0.3, the NH 3 -SCR of NO follows both Eley-Rideal and Langmuir-Hinshelwood mechanisms, in which the Eley-Rideal mechanism is predominated.

Sulfur poisoning and regeneration behavior of In/H-BEA catalyst were carried out in NOx reduction by CH4. In/H-BEA catalyst exhibited a poor resistance to sulfur dioxide after addition of 200 ppm SO2 and 10 vol.% H2O into NO reduction with CH4 at 450 °C for 45 h. Sulfur poisoning of In/H-BEA was attributed to the inhibition of NOx adsorption on Bronsted acid sites, suppression of reaction intermediates generation on the active sites, and the formation of surface sulfate species. The formation of surface sulfate reduced the availability of surface active sites, blocked the pore structure and decreased the surface area of catalyst. These changes in chemical and textural properties resulted in a severe loss in the activity of sulfated In/H-BEA catalyst for NO reduction with CH4. H2 reduction is a promising technology for regeneration of In/H-BEA deactivated by SO2 for removing NOx from lean-burn and diesel exhausts. Indium sulfate could be reduced by H2 to InO+ with In2O3 and In(OH)2+ as the intermediates. The optimal parameters of H2 reduction was regeneration temperature of 400 °C and regeneration time of 60 min which completely recovered the catalytic activity of In/H-BEA.

Heterogeneous catalysts with single‐atom active sites offer a means of expanding the industrial application of noble metal catalysts. Herein, an atomically dispersed Pt1‐Co3O4 catalyst is presented, which exhibits an exceptionally high efficiency for the total oxidation of methanol. Experimental and theoretical investigations indicate that this catalyst consists of Pt sites with a large proportion of occupied high electronic states. These sites possess a strong affinity for inactive Co2+ sites and anchor over the surface of (111) crystal plane, which increases the metal–support interaction of the Pt1‐Co3O4 material and accelerates the rate of oxygen vacancies regeneration. In turn, this is determined to promote the coadsorption of the probe methanol molecule and O2. Density functional theory calculations confirm that the electron transfer over the oxygen vacancies reduces both the methanol adsorption energy and activation barriers for methanol oxidation, which is proposed to significantly enhance the dissociation of the CH bond in the methanol decomposition reaction. This investigation serves as a solid foundation for characterizing and understanding single‐atom catalysts for heterogeneous oxidation reactions.

Due to high catalytic activity and excellent resistance to SO2 and H2O, sulfate materials are considered to be promising vanadium-free catalysts for selective catalytic reduction of NOx with NH3 (NH3-SCR). Despite this, investigations about thermal stability of sulfate SCR catalysts are limited, which is surprising given that sulfates are typically susceptible to thermal decomposition. In this work, the thermal stability of Fe2(SO4)3/TiO2 catalysts was investigated. It was determined that the thermal decomposition of Fe2(SO4)3 resulted in NOx conversion decreased from 90% to 60% at 350 °C. Interestingly however, the introduction of SO2 into the gas stream was found to reverse the effects of the thermal deactivation and the NOx conversion of 90% (350 °C) was once again observed. Extensive characterization of each catalyst sample and density functional theory (DFT) calculations were subsequently conducted. The reduction in catalytic activity after the thermal treatment was attributed to the transformation of Fe2(SO4)3 to α-Fe2O3, which reduced the quantity of Bronsted acid sites on the catalyst. The presence of SO2 in the gas stream was found to reverse this phase transformation which ultimately led to the recovery of Bronsted acid sites. DFT calculations indicated that SO2 adsorbed selectively on Fe atoms of the thermal deactivated catalysts and S-Fe bond should mainly be formed by electrons from p orbitals of S and Fe atoms. Then NH3 could be adsorbed on the surface by N-S bond with SO2. The recoverable property of this catalyst provides a promising outlook for the commercial application, especially given that industrial flue gas streams regularly contain SO2.

A series of CuSO4/TiO2 binary oxide catalysts with different CuSO4 loadings (0–20 wt%) were prepared by a facile solid state impregnation protocol. The physicochemical properties of the catalysts and the NO reaction route were extensively characterized via N2 adsorption/desorption, XRD, Raman, NH3-TPD, NO-TPD, H2-TPR, XPS, and in situ DRIFTS. The CuSO4 content had significant influence on catalytic activity. High CuSO4 loading favored the solid reaction between CuSO4 and TiO2, promoted the formation of sulfite and weak acid sites, and obviously increased the activity at temperatures below 340 °C. However, at a temperature higher than 340 °C, NH3 oxidation increased with CuSO4 loading and caused NOx conversion to decrease when the CuSO4 loading was higher than 10 wt%. Thus, the sample with 10 wt% CuSO4 loading presented the broadest temperature window and it also showed an excellent resistant to SO2 and H2O. Both Bronsted and Lewis acid sites were formed on the catalyst. S–OH of sulfate and sulfite were the main reason for formation of Bronsted acid sites. NH3-SCR reaction on CuSO4/TiO2 followed the Eley–Rideal mechanism: NH3 first adsorbed on Bronsted and Lewis acid sites as NH4+ and NH3, then reacted with gaseous NO and O2 to form N2 and H2O.

Effects of propane/methane ratios on NO x reduction by mixtures of methane and propane over In/H-BEA catalyst were investigated at temperatures ranging from 250 to 550 °C. The higher catalytic activity of In/H-BEA was exhibited for CH 4 -SCR at high temperatures above 450 °C, while the higher NO x conversion was achieved in C 3 H 8 -SCR at below 425 °C. A broadened temperature window and enhanced CO 2 selectivity were achieved by combining of methane and propane as the co-reductant. The mixtures with propane/methane of 1/2 showed the most superior T 50 (325 °C) and T 90 (500 °C) temperatures for NO x reduction over In/H-BEA catalyst. For the promotion mechanism of propane on NO reduction by methane at low temperature, the formation of carbonaceous species (e.g. R-COOH) were enhanced by the activation of C 3 H 8 on Bronsted acid sites at low temperature, and further promoted the generation of NCO species, which was a crucial determining step for NO reduction.

A series of CuSO4/TiO2 catalysts were prepared using a wet impregnation method. The activity of each sample in the selective catalytic reduction of NO by NH3 (NH3-SCR) was determined. The effects of SO2 and H2O, and their combined effect, on the activity were examined at 340 °C for 24 h. The catalysts were characterized using N2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction of H2 (H2-TPR), temperature-programmed desorption of NH3 (NH3-TPD), and in situ diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS). The CuSO4/TiO2 catalysts had good activities, with low production of N2O above 340 °C. SO2 or a combination of SO2 and H2O had little effect on the activity, and H2O caused only a slight decrease in activity during the experimental period. The NH3-TPD and H2-TPR results showed that CuSO4 increased the amounts of acid sites and adsorbed oxygen on the catalyst. In situ DRIFTS showed that the NH3-SCR reaction on the CuSO4/TiO2 catalysts followed an Eley–Rideal mechanism. The reaction of gaseous NO with NH3 adsorbed on Lewis acid sites to form N2 and H2O could be the main reaction pathway, and oxygen adsorption might favor this process.

Promoting chlorine resistance and inhibiting by-product generation are critical issues in catalytic destruction of chlorinated volatile organic compounds (CVOCs). Herein, a yolk-shell-like mesoporous CoCrOx as a robust catalyst was synthesized for deep destruction of dichloromethane (DCM) considering its superior mass transfer and molecule enrichment ability. The strong interaction between Co and Cr elements in CoCrOx results in efficient generation of active Cr6+ and oxygen species, which greatly enhances the activity of CoCrOx in DCM oxidation, much higher than that of Co3O4, Co3O4+Cr2O3 and Cr2O3. Chloromethane (CH3Cl), trichloromethane (CHCl3) and tetrachloromethane (CCl4) can be detected as the cleavage of C H bond and generation of C-Cl bond during DCM destruction. We found that the acid sites can effectively inhibit the formation of by-products over CoCrOx material, which is a promising material for CVOC elimination. The results from this work provide some new insights into the design of catalysts for CVOC destruction.

Here, lauric acid (LA) with a remarkable tailoring property of pore structure and porosity was adopted as modulator for the synthesis of Mn-MIL-100. Results reveal that LA amount has a significant effect on the morphology, crystal size and porous structure of prepared materials. The synthesized catalysts were coupled with a dielectric barrier discharge reactor to improve toluene decomposition performance. We found that the introduction of catalysts can remarkably enhance toluene removal efficiency (TRE), CO2/COx selectivity and energy yield (EY), and simultaneously inhibit the generation of O3 and NOx compared with the non-thermal plasma (NTP) system as the presence of catalysts with developed hierarchical porous structure and well-dispersed crystal particle provides abundant adsorbed centers and active sites for surface reactions. Amongst, LA-8 sample shows the best catalytic performance with TRE, CO2 and COx selectivity of 94.7%, 44.9% and 92.4%, respectively (specific energy density (SED) of 473 J L−1), much higher than the NTP system (respectively; 63.3%, 34.2% and 73.6%). Moreover, the EY of NTP-Catalysis system (5.19 g kWh−1) is also obviously higher than that of single NTP (1.94 g kWh−1) at SED of 262 J L−1. This work paves a way for application of MOFs in NTP-Catalysis system for VOC decomposition.

Catalyst chlorine poisoning is a critical issue to be solved for chlorine-containing VOCs decomposition. Herein, we found that three-dimensional nanosphere-like meso-macroporous MnCo3Ox (SMC-F) synthesized via a co-precipitation method has much higher activity and selectivity for 1,2-dichloroethane destruction than the bulk MnCo3Ox; however, polychlorinated by-products as 1,1,2-trichloroethane, trichloroethylene, perchloroethylene, trichloromethane and perchloromethane originated from the cleavage of C Cl and C C bonds can be detected. As such, CrOx was further introduced to enhance the low temperature activity and selectivity of SMC-F. Results reveal that the incorporation of CrOx boosts surface lattice oxygen (O2−) amount and mobility and generates highly reducible Cr6+ and Mn4+ species in Cr/SMC-F, improving its activity and selectivity remarkably. Only 1,1,2-trichloroethane can be found during 1,2-dichloroethane destruction as the C C bond cleavage route is generally inhibited over Cr/SMC-F. The improved O2− mobility and oxidation property of Cr/SMC-F facilitate surface Cl desorption, ensuring its superior catalytic efficiency and chlorine resistance.

The deactivation and regeneration of selective catalytic reduction catalysts which have been used for about 37,000 h in a coal power plant are studied. The formation of Al2(SO4)3, surface deposition of K, Mg and Ca are primary reasons for the deactivation of the studied Selective catalytic reduction catalysts. Other factors such as activated V valence alteration also contribute to the deactivation. Reactivation of used catalysts via environment-friendly and finance-feasibly approaches, that is, dilute acid or alkali solution washing, would be of great interest. Three regeneration pathways were studied in the present work, and dilute nitric acid or sodium hydroxide solution could remove most of the contaminants over the catalyst surface and partly recover the catalytic performance. Notably, the acid-alkali combination washing, namely, catalysts treated by dilute sodium hydroxide and nitric acid solutions orderly, was much more effective than single washing approach in recovering the activity, and NO conversion increased from 23.6% to 89.5% at 380°C. The higher removal efficiency of contaminants, the lower dissolution of activated V, and promoting the formation of polymeric vanadate should be the main reason for recovery of the activity.