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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.

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.

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.

Pt-Pd-HMS catalyst had been prepared by a one-pot approach and tested for toluene combustion. Comparing with conventional impregnated Pt-Pd/HMS (Ea = 111.41 kJ/mol, Pt-Pd particle size = 23.4 nm), the Pt-Pd-HMS exhibited lower activation energy (Ea = 80.23 kJ/mol) and smaller Pt-Pd particle size (6.3 nm). Moreover, surface Pt0/Pttotal 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 T90 = 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.

CuO-Fe2O3 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-Fe2O3–500 °C, which was reflected by the rapid formation of –NH2 and nitrate species on DRIFTS combining the XPS results. The intermediates –NH2 and NO of internal selective catalytic reduction (iSCR) predominantly accounted for the excellent catalytic activities.

The effect of Ce or La on the hydrothermal stability of Cu-SAPO-34 catalyst was evaluated by the selective catalytic reduction of NOx by ammonia (NH3-SCR) reaction after hydrothermal aging at 700 °C in 10 vol% H2O/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% NOx conversion was maintained over the aged Ce or La modified Cu-SAPO-34 at 175–350 °C, while extremely poor NH3-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.

A series of different manganese oxides supported Pd catalysts with low Pd loading of 0.3 wt.% have been synthesized and applied to CO catalytic oxidation at low-temperature. In situ DRIFTS was employed to dynamically trace CO oxidation process. It was found that the CO catalytic activity decreased in the order of Pd/OMS-2 > Pd/MnO2 > Pd/Mn2O3 >> Pd/Mn3O4. More interestingly, the Pd/OMS-2 catalyst exhibited exceptionally high activity of T99 = 16 °C, as well as higher reducibility. Furthermore, XPS and in situ DRIFTS results indicated that a substantial of lattice oxygen participated in CO oxidation, contributing to the optimal activity over Pd/OMS-2. While the low reactivity over Pd/Mn3O4 was ascribed to a small amount of lattice oxygen and the strongly adsorbed CO on Pd0.

In the previous research, we found that thermal treatment at high temperature could induce the re-dispersion of Ni particles on SBA-15 for dry reforming of methane (DRM). Here, we aimed to study the re-dispersion behavior of Ni particles of Ni/SBA-15 at different temperatures. The results indicated that the mean Ni particle size of Ni/SBA-15 catalysts were 16.9 nm, 14.5 nm, 7.1 nm and 18.4 nm after thermal treatment at 700 °C, 800 °C, 900 °C and 1000 °C, respectively. It could be seen the optimal inducing temperature of Ni/SBA-15 was at 900 °C. The relatively lower inducing temperature did not drive the re-dispersion of Ni particles sufficiently, while the large Ni particles were formed by re-aggregation of re-dispersive Ni species at relatively higher inducing temperature. After 34 h DRM reaction, encapsulated carbon was formed over the catalyst induced by low temperature and the catalytic performance decreased. However, a slight amorphous carbon was discovered over the catalyst induced at 900 °C with highly dispersion. Interestingly, in spite of a large amount of carbon deposition, the 1000Ni/SBA-15 still maintained excellent catalytic activity.

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.

A series of CeO2 prepared with H2SO4 (C–S), H3PO4 (C–P) and H2SO4 + H3PO4 (C–P–S) were investigated in selective catalytic reduction of NOx with NH3. The sulfates contributed to the improvement of Bronsted (B) acid sites, while phosphates were prone to the enhancement of Lewis (L) acid sites, which could improve the catalytic activity. Furthermore, sulfates existed in the surface of C–P–S and C–S; phosphates occurred on the subsurface region or were highly dispersed on the surface of C–P–S and C–P. Besides, the nitrates adsorbed on the CeO2 and NH3 contacted with the sulfates, which followed the L–H mechanism at 200 °C on C–P–S and C–S. The adsorption and activation of NO and NH3 over C–P occurred at the same active sites, which obeyed the E–R mechanism at 200 °C. C–P–S possessed the best catalytic activity because of the appropriate surface acidity and redox property, and more than 80% conversion of NOx was obtained at 220–450 °C. CeO2 modified by H2SO4 (C–S), H3PO4 (C–P) and H2SO4 + H3PO4 (C–P–S) was prepared and used for selective catalytic reduction of NOx by NH3. The presence of sulfate species over C–S and C–P–S contributed to the formation of surface acidity. CeO2 modified by phosphoric acid favored excellent oxidation ability.

A series of silicotungstic acid modified CeO2 (SC-x, x represents the pH value of solution that is used for the preparation of catalysts) were prepared for the selective catalytic reduction (SCR) of NOx with NH3. SC-9 showed the best catalytic activity among the samples. The monodentate nitrate, bidentate nitrate, bridging nitrate and NO2 were detected over SC-9 and SC-10. Monodentate nitrate and bridging nitrate disappeared over SC-8. Furthermore, the monodentate nitrate and bridging nitrate could react with NH4+ on Bronsted acid sites to generate NH4NO3, and then was reduced by NO to form NO2, accompanied with the fast reaction between NO2 and coordinated NH3 on Lewis acid sites in the presence of gaseous NO. Besides, the SCR reaction pathway of SC catalysts followed by the Langmuir–Hinshelwood mechanism and the Eley–Rideal mechanism.

Mesoporous Al2O3-supported Pt-Pd catalyst was prepared via a one-step evaporation-induced self-assembly (EISA) process and employed for toluene combustion. It was found that the T90 (160 °C) and activation energy (43 kJ/mol) of the one-pot prepared Pt-Pd-Al2O3 catalyst are lower than the conventional Al2O3- supported Pt-Pd catalyst prepared by the wet impregnation method (250 °C, 49.8 kJ/mol). Moreover, the one-pot prepared Pt-Pd-Al2O3 catalyst shows the presence of nano Pt-Pd particles in the mesochannels. In terms of the one-pot EISA approach, the bi-metallic Pt-Pd-Al2O3 catalyst exhibits reduced noble-metal mean particle size (6.1 nm) and T90 than the mono-metallic Pt-Al2O3 and Pd-Al2O3 catalysts. It was demonstrated that the present Pt-Pd-Al2O3 catalytic system exhibits the lowest T90 and T50 parameter values and apparent activation energy at comparable space velocities and toluene feed composition compared to several best performed catalysts reported in the literature.

Carbon dioxide reforming of methane to syngas was investigated over a series of MgO promoted Ni/CNT catalysts. MgO played a critical role in improving the catalytic performance of Ni/CNT. The results showed that the addition of MgO strengthened the interaction of Ni and interior surface of CNT. Highly dispersed nickel particles with small size (less than 4.5 nm) were also observed in MgO modified CNT. Otherwise, the NiO nanoparticles were facilely reduced over the catalyst prepared with a narrow size of CNT, as shown in H2-TPR. The reaction tests demonstrated that the Ni-based catalyst with an addition of MgO and narrow size of CNT exhibited better catalytic activity. Furthermore, the lifetime of Ni-based catalyst was prolonged effectively after adding MgO, attributed to the stabilization and dispersion of Ni particles and the effective restraint on the gasification of CNT.

The solid superacid TiO2-ZrO2-SO42−-supported 20 wt.% CeO2 catalyst (20CeO2/Ti-Zr-S) was synthesized for selective catalytic reduction of NO with NH3 (NH3-SCR). The NH3-SCR performance was significantly enhanced by the construction of strong acid sites on the surface of 20CeO2/Ti-Zr-S and over 96% NO conversion was obtained at 225–425 °C. Meanwhile, the strong interaction between solid superacid and CeO2 resulted in excellent redox property and abundant surface oxygen species. Furthermore, the NH3-SCR reaction over 20CeO2/Ti-Zr-S catalyst mainly followed the Langmuir-Hinshelwood mechanism at low-temperature (250 °C). The M-NO2 (M = Ce, Ti, Zr) nitrate compounds, monodentate and bridging nitrates were the crucial intermediates in Langmuir-Hinshelwood mechanism. In addition, amide (–NH2) species were available at 350 °C over 20CeO2/Ti-Zr-S catalyst, which facilitated the high-temperature NH3-SCR activity via Eley-Rideal pathway.

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.

A series of CuO-Fe 2 O 3 composite oxides were successfully prepared for low temperature selective catalytic oxidation of ammonia (NH 3 -SCO). Higher Cu/Fe ratio in CuO-Fe 2 O 3 catalysts led to higher activity for NH 3 oxidation and the lower Cu/Fe ratio improved the N 2 selectivity. The optimal catalyst with a Cu/Fe molar ratio of 5:5 displayed a low complete conversion temperature ( 2 selectivity (>91%). H 2 -TPR results indicated that the synergistic effect existed between Fe 2 O 3 and CuO, which was beneficial to the catalytic performance. The results of the DRIFTS showed that NH 3 -SCO reaction mainly followed the internal SCR (i-SCR) mechanism. The adsorbed NH 3 was first activated and reacted with atomic oxygen to form the nitrosyl (-HNO). Then the -HNO was oxidized by oxygen atoms from O 2 to form NO species. Meanwhile, the in situ -formed NO could react with -NH 2 to form the main product of N 2 .

Ni/SBA-15 catalyst was prepared by homogeneous precipitation method (Ni-HP) and used for dry reforming of methane (DRM). The related characterization results indicated that the Ni particles were highly dispersed with a size range of 2-5 nm. Compared with Ni/SBA-15 catalyst prepared by impregnation (Ni-IM), the reduction temperature of Ni-HP obtained from H2-TPR was greatly improved, suggesting the stronger metal-support interaction. After reacting at 700 °C for 100 h, the CH4 conversion of DRM over Ni-HP catalyst slightly decreased from 74.5% to 73.8%. While, for the Ni-IM catalyst, the CH4 conversion dropped from 61.7% to 37.3%. Furthermore, the average particle size of Ni-HP was 3.7 nm and 4.7 nm before and after the long-time stability test, respectively, ascribed to the good anti-sintering property. Although a certain amount of coke was produced, mainly with disorder filamentous carbon of base-growth, the Ni/SBA-15 prepared by homogeneous precipitation exhibited excellent catalytic activity and stability.

A number of Co3O4 catalysts with various structures and exposed crystal planes were prepared by different methods. The effects of the structures and exposed crystal planes on the catalytic activity of Co3O4 catalysts were investigated for the catalytic decomposition of N2O. The Co3O4 with nanorod structure was enclosed by (220) planes; Co3O4 with irregular shape crystallites predominantly exposed (111) and (040) lattice planes; Co3O4 with bulk particles only showed the single exposure of (040) planes; the spherical particles of Co3O4 presented the (220) and (311) planes. The results indicated that Co3O4 with irregular shape crystallites showed the best catalytic activity and over 80% of N2O conversion was obtained at 384–450°C. The bulk particles of Co3O4 showed inferior performance. In addition, the exposed crystal planes of Co3O4 prepared by different methods can affect the catalytic decomposition of N2O.

A series of precipitants and commercial surfactants (soft templates) were employed to synthesize mesoporous/nano CeO2 by a hydrothermal method. As-prepared CeO2 was impregnated with palladium and employed for low-temperature catalytic oxidation of CO. It was found that both soft templates and precipitants had significant effects on the morphology, particle size, crystallinity, and porous structure of the CeO2, having a significant effect on the surface palladium abundance, molar ratios of surface species, and catalytic activity of the final impregnated Pd/CeO2. Using ammonia as precipitant could facilitate increased surface palladium abundance and surface molar ratios of PdO/Pd SMSI , Ce3+/(Ce3+ + Ce4+), and Osurface/Olattice. The catalytic activity of the final Pd/CeO2 catalysts could be enhanced as well. The optimal P123-assisted ammonia-precipitated Pd/CeO2 catalyst exhibited over 99% catalytic conversion of CO at 50 °C.

Mesoporous silica-supported Ni can serve as alternative effective catalysts for dry reforming of methane. However, conventional synthesis method requires long synthetic time and high cost, and the resulting catalysts show unsatisfactory catalytic stability due to coking and sintering. In this paper, we reported a facile, low-cost and environmental benign method to introduce Ni species into HMS mesoporous silica (Ni-HMS) in a self-assembled way. FT-IR, H 2 -TPR, and TEM manifested that the obtained Ni-HMS established uniform distributed Ni particles (3.9 ± 0.5 nm) and strong metal-support interaction derives from Si-O-Ni bonding. The dry reforming of methane results demonstrated that the Ni-HMS showed more active and stable catalytic performance than that of Ni impregnated HMS catalyst (Ni/HMS). Notably, the catalytic activity was well maintained even after reacting at 700 °C for 100 h. HAADF-STEM and TG-DSC revealed that coking and sintering were unnoticeable over the endurance-tested Ni-HMS catalysts. The strong anchor effect of pore wall to Ni nanoparticles inherent to the one-pot synthesis was suggested to be the original reason for enhanced resistance toward coking and sintering.

The mechanism of phosphotungstic acid modification CeO 2 catalysts (P-W/CeO 2 ) with different CeO 2 supports were investigated by in situ diffuse reflectance infrared transform spectroscopy for the selective catalytic reduction of NO by NH 3 . The results indicated that the NH 3 -SCR reaction over P-W/CeO 2 followed both the Langmuir–Hinshelwood mechanism and the Eley–Rideal mechanism. The reaction between NH 4 + and bidentate nitrate (NO 3 − ) took place, and then the H 2 O, N 2 and adsorbed NO 2 were formed. The coordinated NH 3 species reacted with adsorbed NO 2 and gaseous NO to generate N 2 and H 2 O. The interaction between CeO 2 and phosphotungstic acid contributed to the favored surface acidity (Lewis and Bronsted acid sites) and excellent redox property. The Bronsted acid sites facilitated the generation of NO 2 -adsorbed and Lewis acid sites accelerated the Eley–Rideal mechanism, while the NO oxidation to bidentate nitrate or NO 2 -adsorbed species was an important step in the reaction mechanism of P-W/CeO 2 .

The present research has probed the effect of different thermal-treatment temperatures on the catalytic activity of CO oxidation and the physio-chemical properties of an OMS-2 supported palladium catalyst. The catalytic activity of Pd/OMS-2 increased with an increase in the thermal-treatment temperature from 300 to 500 °C. The optimal Pd/OMS-2 catalyst exhibited over 99% CO conversion at 35 °C. An elevated thermal-treatment temperature up to 500 °C led to a decrease in OMS-2 crystallinity and surface chemisorbed oxygen (–OH), while the surface atomic ratios of oxygen/Mn and palladium increased with the calcination temperature. A high thermal-treatment temperature above 500 °C led to the phase transformation of OMS-2 into Mn2O3, and an abrupt alteration in the Pd–support interaction and deactivation of the Pd/OMS-2 catalyst.

Manganese oxide octahedral molecular sieves (OMS-2) synthesized from hydrothermal (H-OMS-2), reflux (R-OMS-2), co-precipitation (C-OMS-2), and solid phase (S-OMS-2) methods were impregnated with palladium and used for CO catalytic oxidation. Preparation methods presented an obvious effect on the morphology and catalytic activity of Pd/OMS-2 catalysts for CO oxidation. The hydrothermal synthesized OMS-2 (Pd/H-OMS-2) exhibited more ordered nanorod structure and higher crystallinity than Pd/R-OMS-2, Pd/C-OMS-2, and Pd/S-OMS-2. Further surface analysis indicated that different preparation methods of synthesizing OMS-2 and the impregnation process followed have a significant effect on the chemical states of Mn and O over the final Pd/OMS-2 products. The kinetics studies showed the trend of apparent activation energy (E a) over different catalysts: Pd/H-OMS-2 (18.19 kJ/mol)

A series of CeO2 supports over phosphotungstic acid doped CeO2 (P-W/CeO2) prepared by hydrothermal (Cat-A), sol–gel (Cat-B) and precipitation (Cat-C) methods were investigated in selective catalytic reduction of NOx by NH3. The catalytic activity of P-W/CeO2 was dramatically affected by the preparation methods of CeO2 supports. Results implied that the incorporation of W species could cause the decease of cell parameter and lattice contraction, resulting in inducing the formation of more Ce3+ and oxygen vacancies over the Cat-A catalyst, leading to the excellent oxidation ability and SCR activity. Furthermore, the Cat-A catalyst possessed the most amount of Lewis acid sites, resulting in the superior catalytic activity. Besides, the larger specific area and the excellent redox ability were responsible for the outstanding SCR performance. In brief, the favorable activity in NH3 oxidation, as well as NO oxidation, contributed to the excellent catalytic activity. Therefore, the Cat-A catalyst exhibited the best SCR activity and over 90% NOx conversion was obtained at 190–450 °C.

A series of sulfated CeO 2 catalysts were synthesized by impregnation and sol-gel methods and used for selective catalytic reduction (SCR) of NO x by NH 3 . The results showed that the sulfated CeO 2 catalysts prepared by sol-gel method showed excellent catalytic activity at 150–450 °C, and more than 90% NO x conversion was obtained at 232–450 °C with a gas hourly space velocity of 60000 h −1 . The catalysts were characterized by X-ray diffraction (XRD), N 2 adsorption, Raman, thermogravimetry (TG), H 2 -temperature-programmed reduction (H 2 -TPR) and Py-infrared spectroscopy (Py-IR). The excellent SCR performance was associated with the surface acidity and the micro-structure. The introduction of sulfate acid into CeO 2 could increase the amount of Bronsted and Lewis acid sites over the catalysts, resulting in the improvement of the low temperature activity. The sulfated CeO 2 catalysts prepared by sol-gel method possessed lower crystallization degree, excellent redox property and larger specific surface areas, which were responsible for the superior SCR performance.

The Cu/ZSM-5 catalysts prepared by different copper precursors were used for the selective catalytic reduction (SCR) of NO x with NH3. The Cu/ZSM-5 catalyst prepared by the copper nitrate (Cu/ZSM-5-N) presented the best performance among the Cu/ZSM-5 catalysts and showed above 90 % NO x conversion at 225–405 °C. The average particle size of CuO was 5.82, 9.20, and 11.01 nm over Cu/ZSM-5-N, Cu/ZSM-5-S (prepared by copper sulfate), and Cu/ZSM-5-C (prepared by copper chloride), respectively. The Cu/ZSM-5-N catalyst showed the highly dispersed copper species, the strong surface acidity, and the excellent redox ability compared with the Cu/ZSM-5-C and Cu/ZSM-5-S catalysts. The Cu+ and Cu2+ existed in the Cu/ZSM-5 catalysts and the abundant Cu+ over Cu/ZSM-5-N might be responsible for the superior SCR activity.

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 FeWO4 or WO3 species with an optimal ratio, prompting its best active window with more than 90% NOx 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 Bronsted acid sites. The reaction intermediate between NO3− and NH2 formed on the surface of FeOx-WO3 catalyst was such a crucial factor in improving the reaction performance of NH3-SCR and the difference of N2 selectivity.

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)

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 CO2 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.

Mesoporous nano Pd/CeO2, Pd/CeO2–ZrO2 and Pd/CeO2–ZrO2–Al2O3 catalysts were prepared via a soft template-assisted hydrothermal method and employed in low-temperature catalytic CO oxidation. Almost 100% of CO conversion could be obtained by the optimal Pd/CeO2–ZrO2–Al2O3 catalyst at 60 °C. Addition of Zr and Al into Pd/CeO2 lead to an increase of the pore volume, average size of mesopores, the surface Ce3+/Ce4+ atomic ratios and Oadsorbed/Olattice, while the activation energy (Ea) decreased in the order Pd/CeO2 (50.4 kJ mol−1) > Pd/CeO2–ZrO2 (40.7 kJ mol−1) > Pd/CeO2–ZrO2–Al2O3 (32.4 kJ mol−1). The low-temperature CO catalytic conversion increased with the decreased activation energy (Ea).

The present work elucidated the effects of structures and surface species on the activity of CeO2 and SO42− doped MCM-41 catalysts toward NO reduction by NH3. The results indicated that the sulfated species were generated over Cat-A (Ce(NO3)3·6H2O and H2SO4 simultaneously doped on MCM-41) and Cat-B (Ce(NO3)3·6H2O first immersed to MCM-41 and followed by impregnation of H2SO4) except for Cat-C (H2SO4 first doped onto MCM-41 and followed by Ce(NO3)3·6H2O). The sulfate ion contributed to the formation of Ce3+ concentration, oxygen vacancies, and surface acidity, resulting in improvement of SCR activity. However, the positive influence on SCR activity was overwhelmed by the decomposition of sulfated species. The apparent activation energy of Cat-A (60 kJ mol−1) was much lower compared with that of Cat-B and Cat-C (71 and 78 kJ mol−1, respectively). Pore structures and surface species were responsible for the SCR activity over the CeO2 and SO42− doped MCM-41 catalysts. The best catalytic activity was obtained over Cat-A, followed by Cat-B, and Cat-C exhibited the least catalytic activity.

The catalytic hydrolysis of HCN was systematically investigated using Fe/ZSM-5, Nb/ZSM-5 and Fe–Nb/ZSM-5 catalysts. Fe–Nb/ZSM-5 exhibited the highest HCN hydrolysis activity and the reaction products were NH3 and CO. However, no NH3 was detected due to the large ammonia storage capacity of the catalysts. The interaction between the Fe and Nb species resulted in increased amounts of isolated Fe3+, Nb5+, oligomeric FexOy and NbxOy clusters, which could contribute to improving HCN hydrolysis. Furthermore, the excellent redox properties, favored pore structure and abundance of surface acid sites were responsible for the superior catalytic hydrolysis of HCN. Furthermore, the reaction pathway was speculated as follows: HCN and H2O reacted to produce methanamide. Methanamide further reacted with H2O to generate ammonium formate, which decomposed to formic acid and NH3. Formic acid was then converted into CO and H2O via pyrolysis.

A series of CeO2-ZrO2-WO3 catalysts for the selective catalytic reduction (SCR) of NO with NH3 were prepared by hydrothermal method. The influence of calcination temperature on the catalytic activity, microstructure, surface acidity and redox behavior of CeO2-ZrO2-WO3 catalyst was investigated using various characterization methods. It was found that the CeO2-ZrO2-WO3 catalyst calcined at 600 °C showed the best catalytic performance and excellent N2 selectivity, and yielded more than 90% NO conversion in a wide temperature range of 250–500 °C with a space velocity (GHSV) of 60000 h−1. As the calcination temperature was increased from 400 to 600 °C, the NO conversion obviously increased, but decreased at higher calcination temperature. The results implied that the higher surface area, the strongest synergistic interaction, the superior redox property and the highly dispersed or amorphous WO3 species contributed to the excellent SCR activity of the CeO2-ZrO2-WO3 catalyst calcined at 600 °C.

The selective catalytic reduction (SCR) of NO by NH3 has been investigated over the CeO2–ZrO2–WO3 (CZW) catalysts prepared by hydrothermal synthesis, incipient impregnation, co-precipitation and sol–gel methods. The results indicate that the CZW catalyst prepared by hydrothermal method shows the best SCR activity, and more than 90% NO conversion is obtained at 195–450 °C with a gas hourly space velocity of 50,000 h−1. The samples are characterized by XRD, N2 adsorption–desorption, SEM, EDS, XPS, H2-TPR, NH3-TPD and Pyridine-IR techniques. The results imply that the superior SCR activity of CZW catalyst is contributed to the excellent redox property, strong acidity and highest content of chemisorbed oxygen species. Furthermore, the larger surface area and greater total pore volume improve the redox ability and enhance NO conversion at low temperature, while the co-existence of Lewis and Bronsted acid sites enhance the SCR activity at high temperature.

A series of acid modified CeO 2 catalysts were prepared and used for selective catalytic reduction (SCR) of NO with NH 3 . The results showed that the SCR activity of pure CeO 2 was greatly enhanced by the modification of acid. The CeO 2 modified by 20% phosphotungstic acid exhibited the best NO conversion in a wide temperature range of 150–550 °C. The SCR activity was slightly influenced by SO 2 and H 2 O, while such effect was reversible. The improvement of SCR activity and N 2 selectivity over CeO 2 catalyst modified by acid was attributed to the enhanced amount and intensity of Bronsted or Lewis acid sites.

A series of Ca modified Co3O4 catalysts with different Ca/Co molar ratios were synthesized by the co-precipitation method and applied to N2O catalytic decomposition. The experimental results showed that the performance of N2O catalytic decomposition was obviously enhanced by the addition of Ca into the Co3O4 catalyst. The Ca modified Co3O4 catalyst with Ca/Co molar ratio of 1:2 exhibited the highest catalytic performance and almost 100% N2O conversion was achieved at 400 °C. The characterization results showed that the addition of suitable calcium composition could promote the growth of the 111 crystal plane of Co3O4 and provide abundant surface oxygen on the surface of the catalyst. The kinetics studies confirmed that the activation energy of the Ca modified Co3O4 catalyst with Ca/Co molar ratio of 1:2 (Ea = 17.84 kJ mol−1) was lower than that of pure Co3O4 (Ea = 43.21 kJ mol−1), implying that the addition of Ca into the Co3O4 was beneficial to the catalytic decomposition of N2O.

A stable Ni/SBA-15 catalyst was prepared by an ammonia evaporation (Ni-AE) method for dry reforming of methane. The characterization results exhibited that the highly dispersed and uniformly distributed Ni nanoparticles with strong metal–support interactions can be obtained by the ammonia evaporation method. The presence of Ni phyllosilicate was crucial to obtain Ni nanoparticles with a size of 3.2–5.2 nm after reduction by H2, which were smaller and exhibited a narrower size distribution than in the sample prepared by impregnation (Ni-IM). Dry reforming of methane reactivity results showed no observed decrease of activity for Ni-AE even when reacted at 800 °C for 100 min or 700 °C for 100 h, while the Ni-IM presented an obvious decrease under the same conditions. TEM images of spent Ni-AE catalyst further confirmed that the Ni nanoparticles were highly dispersed, and the weight loss of Ni-AE (2.09%) revealed by the TG curves is much lower than that of the Ni-IM sample (24.16%). The strong metal–support interactions derived from Ni phyllosilicate were mainly responsible for resistance to coking and sintering.

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 NH3 (NH3-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 FeWO4 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 NH2 intermediate and subsequent reduction by NO, while the formation of NH4NO3 species over FW-IM was easily transformed into N2O species.

A series of Fe–Ti-Ox 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 H2O. 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 NH3). 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 TiO2 and decline in quantity of Fe2+ species. Besides, Fe–Ti-Ox catalysts with amorphous states of TiO2 could enhance catalytic hydrolysis of HCN, which depended on the effect of calcination temperature during the preparation process of Fe–Ti-Ox catalysts.

RuOx/TiO2 and RuOx/TiO2-SO42− catalysts were prepared and used for selective catalytic oxidation of ammonia (NH3-SCO). The results indicated that N2 selectivity over RuOx/TiO2 was significantly enhanced after the introduction of SO42−. The introduction of SO42− into RuOx/TiO2 observably increased the amount and strength of acid species on the surface of catalyst. Specifically, the RuOx/TiO2-SO42− sulfated treatment at 2 h possessed the optimal surface acidic property obtaining more than 85% N2 selectivity at 300 °C, which was apparently higher than that of RuOx/TiO2 with 66% N2 selectivity. The strong interaction between sulfated support and RuOx resulted in excellent redox property at high temperature, abundant surface oxygen and more Ru4+ species. Particularly, DRIFTS and NH3-TPD illustrated that the increased N2-selectivity was put down to Bronsted and Lewis acid sites augmented via sulfating treatment of TiO2, promoting the dehydrogenation of adsorbed ammonia species on the catalyst surface, then the formation of more NH2 species could facilitate the reduction of NO to harmless N2, meanwhile, the generation of HNO species also were reduced to N2 by NH. Therefore, the excellent acid properties of RuOx/TiO2-SO42− gave rise to the formation of few nitrate species with an iSCR mechanism, which ensured to the high N2 selectivity.

A series of CuO-CeO2-ZrO2 catalysts were prepared by different methods and applied to the selective catalytic reduction of NO with NH3 reaction at low temperature. The results showed that the SCR activities, morphology, particles dimension, and the surface chemical state of CuO-CeO2-ZrO2 catalysts were obviously influenced by the preparation method. The SCR performance results showed that the CuO-CeO2-ZrO2 catalyst prepared by co-precipitation method presented the best activity in the temperature range of 125–180 °C. The characterization results showed that the Ce4+, Ce3+, Cu2+ and Cu+ species were coexistence in the CuO-CeO2-ZrO2 catalysts, and the Cu species mainly existed as Cu2+. It was also found that the high surface area, the synergistic effect between copper and ceria, enhanced acidity and the highly dispersed copper species were responsible for the high SCR activity of the CuO-CeO2-ZrO2 catalyst.

The CuO-MnOx 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 T100 was only 230 °C. The results of XPS, Raman and H2-TPR proved that the Olatt/Oads 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 MnOx 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 O2, then the intermediates were further oxidized to CO2 and H2O by reacting with the supplementary surface lattice oxygen.

A series of WO 3 –ZrO 2 carriers were prepared by co-precipitation method with different mass fractions (0 wt%, 5 wt%, 10 wt%, 15 wt% and 20 wt%) of WO 3 , and MnO x –CeO 2 /WO 3 –ZrO 2 monolith catalysts were prepared for selective catalytic reduction of NO x with ammonia (NH 3 -SCR) in the presence of excessive O 2 . The catalysts were characterized by N 2 adsorption–desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and NH 3 /NO temperature-programmed desorption (NH 3 /NO-TPD). The experimental results showed that, the tungsten modified monolith catalyst MnO x –CeO 2 /WO 3 –ZrO 2 with the WO 3 content 10 wt% had the best catalytic activity and the widest reaction window; it possessed a better thermal stability than V 2 O 5 /WO 3 /TiO 2 catalyst, and showed a better H 2 O and SO 2 tolerance than MnO x –CeO 2 /ZrO 2 . The characterization results indicated that MnO x –CeO 2 /10% WO 3 –ZrO 2 had the best textural properties, a well-dispersed state of WO 3 , the lowest binding energy of Ce 3+ 3d 5/2 , the maximum value of Ce 3+ :Ce=20.7%, the suitable molar ratio of Mn:Ce≈1, and a co-existence state of MnO 2 –Mn 2 O 3 . In addition, it had the most adsorbed sites of NH 3 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 10,000 h −1 . It possessed better potential for practical application.

A series of tungsten modified MnOx–CeO2 monolith catalysts were prepared and used for selective catalytic reduction (SCR) of NO by NH3 in the presence of O2. The experimental results showed that the SCR performance and SO2-resistant ability of MnOx–CeO2 were greatly enhanced by the introduction of tungsten. The catalyst containing 10% WO3 showed the highest NO conversion in a wide temperature range of 162–374 °C. The highly dispersed or amorphous tungsten oxide and the strong interaction between tungsten and MnOx–CeO2 should be the reasons for the excellent performance of the catalyst containing 10% WO3.

MnO x /CeO 2 –ZrO 2 –Al 2 O 3 (MnO x /CZA) catalysts with different amounts of manganese loading were prepared by incipient wetness impregnation method for selective catalytic reduction (SCR) of NO with NH 3 at low temperature. The catalysts were characterized by N 2 adsorption–desorption measurement, XRD, XPS, and H 2 -TPR. Catalytic activity tests reveal that the MnO x /CZA catalyst with 10% manganese loading has the best catalytic activity, almost 90% NO is translated to N 2 in the temperature range of 143–300 °C. The highly dispersed MnO x species, the good oxidation activity of NO to NO 2 , the existent synergistic effect between the manganese and cerium oxides, and the various oxidation states of manganese oxides may be the main reasons for the best SCR activity. In addition, the SCR activity is slightly influenced in the presence of SO 2 and H 2 O, while such effect is restorable after heating treatment.