H2 Temperature-programmed Reduction Research Articles

Catalytic Oxidative Decomposition of Dimethyl Methyl Phosphonate over CuO/CeO2 Catalysts Prepared Using a Secondary Alkaline Hydrothermal Method

Bimetallic synergism plays an important role in lattice-doped catalysts. Therefore, lattice-doped bimetallic CuO/CeO2 catalysts were prepared by secondary alkaline hydrothermal reaction. During this process, the CeO2 nanomaterials were partially dissolved and recrystallized; thus, Cu ions were doped into the CeO2 lattice. The physical and chemical properties of CeO2, CuO/CeO2, and CuO were investigated. H2 temperature-programmed reduction characterization showed that the oxidation activity of CuO/CeO2 was significantly improved. X-ray photoelectron spectroscopy results showed that electron transfer occurred between Ce and Cu in the CuO/CeO2 catalyst. Additionally, Raman characterization confirmed the strong interaction between Cu and Ce. After CuO was loaded, the thermal catalytic decomposition performance of the catalyst was significantly improved with respect to the sarin simulant dimethyl methyl phosphonate (DMMP); with an increase in the Cu/Ce ratio, the performance first strengthened and then weakened. Additionally, the reaction tail gas and catalyst surface products were analyzed using mass spectrometry and ion chromatography, and the changes in the surface products during the thermal catalytic decomposition of DMMP were characterized at different temperatures using in situ diffuse reflectance infrared Fourier transform spectroscopy. Finally, the catalytic reaction pathways of DMMP on CeO2, CuO/CeO2, and CuO were inferred. The study results not only demonstrate an effective catalyst for the removal of nerve agent but also a feasible preparation method for lattice-doped bimetallic catalysts in the field of environmental protection.

PtPd nanoparticles on LaCoO3 with ruthenium in the interfaces for CO oxidation

In this work, trimetallic Pt-Pd-Ru nanoparticles (NPs) loaded on LaCoO3 perovskite were prepared by using LaCo0.9PtxPdyRu0.1-x-yO3 as precursor through citrate complexing sol-gol method and characterized by N2 adsorption/desorption, XRD, H2 Temperature-programmed reduction, XPS, CO-TPD, ICP-OES and TEM techniques. The special structure of the trimetallic catalyst and its catalytic performance for CO oxidation were investigated. The results demonstrated that Pt, Ru and Pd ions were successfully incorporated into the lattice of LaCoO3 to form with perovskite structure. After the reduction treatment, the catalyst Pt-Pd-Ru/LaCoO3 was obtained, which exhibited special structure of Pt surface, Pd sub-surface and Ru interface. The trimetallic Pt-Pd-Ru/LaCoO3 displayed the highest activity and best stability for CO oxidation as compared with corresponding bimetallic and monometallic catalysts. The significant improvement on the catalytic activity was ascribed to the combination of the oxygen vacancies on the surface of LaCoO3 and the highly dispersed NPs. The excellent stability was owing to the special metal-support interaction, that is the Pt-Pd in the NPs are connected and adhered to the support of LaCoO3 by the Ru species in the interface.

Effect of framework Al pairing on NO storage properties of Pd-CHA passive NOx adsorbers

Three Pd/H-CHA samples were prepared containing 53.0 %, 10.8 % and 6.5 % paired Al sites at near fixed Si/Al ratio and similar Pd loading. According to H2 temperature-programmed reduction, Pd was present almost exclusively as isolated cations in the two samples containing the higher concentrations of paired Al sites, whereas in the other sample PdO was also present. Simulated lean cold start tests on the fresh samples conducted in a microflow reactor showed that the sample containing PdO stored the lowest amount of NOx. When tested with CO/H2, the sample containing 53.0 % paired Al sites showed significantly better storage capacity than the other samples and deactivated less rapidly upon sequential tests. Experiments using lean gasoline engine exhaust revealed similar trends. This study showed that a high concentration of paired Al sites in Pd/H-CHA is beneficial for NOx storage capacity, thermal durability, and minimizing deactivation in the presence of CO/H2.

Layered-double-hydroxide-based Ni catalyst for CO2 capture and methanation

Ni-based catalysts prepared using layered double hydroxides (LDH) as precursors containing Mg and Ca are examined as dual-function materials for CO2 capture and methanation. X-ray diffraction, thermogravimetric analysis, H2 temperature-programmed reduction, N2 adsorption, and scanning transmission electron microscopy analyses revealed that the LDH-derived Ni catalysts form porous structures of composite oxides (MgO-NiO) containing 5-nm-sized micropores and highly dispersed 5–10-nm-sized Ni-metal nanoparticles. The methanation performance is investigated under isothermal cyclic operation with an O2-containing gas (10%-CO2/5%-O2/bal.-He) and 20%-H2/bal.-He at 320 °C; the results indicate that the LDH-derived Ni catalysts containing Ca, Mg, and Al exhibit high methanation activities. Mg contributes to the stabilization of the porous structure and enhances the Ni-metal dispersion, while Ca provides effective CO2 adsorption and storage sites.

Cobalt-Graphene Catalyst for Selective Hydrodeoxygenation of Guaiacol to Cyclohexanol.

Herein, cobalt-reduced graphene oxide (rGO) catalyst was synthesized with a practical impregnation–calcination approach for the selective hydrodeoxygenation (HDO) of guaiacol to cyclohexanol. The synthesized Co/rGO was characterized by transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD), and H2 temperature-programmed reduction (H2-TPR) analysis. According to the comprehensive characterization results, the catalyst contains single Co atoms in the graphene matrix and Co oxide nanoparticles (CoOx) on the graphene surface. The isolated Co atoms embedded in the rGO matrix form stable metal carbides (CoCx), which constitute catalytically active sites for hydrogenation. The rGO material with proper amounts of N heteroatoms and lattice defects becomes a suitable graphene material for fabricating the catalyst. The Co/rGO catalyst without prereduction treatment leads to the complete conversion of guaiacol with 93.2% selectivity to cyclohexanol under mild conditions. The remarkable HDO capability of the Co/rGO catalyst is attributed to the unique metal–acid synergy between the CoCx sites and the acid sites of the CoOx nanoparticles. The CoCx sites provide H while the acid sites of CoOx nanoparticles bind the C-O group of reactants to the surface, allowing easier C-O scission. The reaction pathways were characterized based on the observed reaction–product distributions. The effects of the process parameters on catalyst preparation and the HDO reaction, as well as the reusability of the catalyst, were systematically investigated.

High activity and stability of nano‐nickel catalyst based on LaNiO3 perovskite for methane bireforming

AbstractIn this study, a nano‐nickel Ni0 catalyst for bireforming of methane was in‐situ synthesized from the sol‐gel fabricating LaNiO3 perovskite. The various physico‐chemical methods such as powder X‐ray diffraction (XRD), energy‐dispersive X‐ray spectroscopy (EDS), H2 temperature‐programmed reduction (H2‐TPR), scanning electron microscopy (SEM), and CO2 temperature‐programmed desorption (CO2‐TPD) were used for characterization of the obtained samples. The coke accumulation was investigated via the temperature‐programmed oxidation (TPO) method. The results confirmed the formation of both LaNiO3 perovskite structure and a small amount of NiO with high crystallinity. H2‐TPR profiles and XRD patterns showed that the highly dispersed nanocrystals Ni0 on La2O3 catalysts were formed by in‐situ reduction of LaNiO3 at 800°C for as short as 1 hour or more. The crystal sizes of Ni0 and La2O3 crystals are in the range of 17‐18 nm and 18‐19 nm, respectively. The activity of the catalysts was studied in bireforming of methane by the micro‐flow method in a temperature range of 550‐800°C. LaNiO3‐based catalyst showed excellent performance for methane bireforming reaction. Of which, LaNiO3 sample calcined at 800°C for 1.5 hours and reduced at 800°C for 1.5 hours showed the highest activity when it reached the CH4 conversion of 87% and abnormally high CO2 conversion, reaching 97 % at 700°C and approximately 100 % at 800°C with an ideal H2/CO ratio of approximately 2. At 800°C, the activity of the most outstanding catalyst remained stable for 100 hrs thanks to the high sintering resistance of excellent dispersion of Ni in LaNiO3 lattice and high coke tolerance of the catalyst. The catalytic activity remained stable even when the amount of inert γ‐carbon reached 8.58 mgC/gcat.

Surfactant-confined synthesis of novel W-precursor and its application in the preparation of efficient hydrotreating catalysts

This article presents a surfactant-dispersed W precursor to prepare highly active hydrotreating (HDT) Al2O3-supported NiW catalyst. The proposed strategy converts polytungstate anions into surfactant-dispersed decatungstate precursor with a core–shell structure, which is then successfully deposited onto the pore channels of γ-alumina under moderate hydrothermal conditions. A variety of characterization methods, including X-ray diffraction (XRD), inductively coupled plasma-optical emission spectrometry (ICP-OES), N2 adsorption–desorption, fourier transform infrared (FT-IR), ultraviolet–visible spectroscopy (UV–Vis), Raman spectroscopy, and H2 temperature programmed reduction (H2-TPR) were employed to identify the structure and composition of synthesized W precursor, as well as its states on the catalyst surface after drying and after calcination. After sulfidation, slab morphology and proportion of WS2 and NiWS phases on the as-obtained sulfide catalysts were determined by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Results show that the hydrothermal deposition method ensures the the uniform distribution of the W species. Moreover, the long-chain quaternary ammonium cation shell of as-prepared W-precursor not only weakens the metal-support interaction, but also acts as a dispersant to prevent the aggregation of W species after decomposition. The multiple effects facilitate the formation of highly dispersed WS2 slabs with enhanced stacking, and therefore yield a larger number of accessible NiWS edge sites after Ni incorporation. The resulted W/Al2O3 and NiW/Al2O3 catalysts exhibits higher HDT activity for dibenzothiophene (DBT) and quinoline (Q) removal in comparison with that of reference catalysts prepared from conventional precursor. The present work explores the essential role of surfactants in adjusting metal-support interaction and controlling the morphology of active phases, and reveals the directing effects of W-precursors on the size and morphology of active phases, thereby further shedding light on the rational design and controllable fabrication of supported WS2 for efficient HDT.

One-pot synthesis of CNT-SAPO-34 composite supported copper and cerium catalysts with excellent surface resistance to SO2 and H2O in NH3-SCR

CuCe/CNTx-SAPO-34 (x = 0, 0.5, 1, 2) with various CNT doping quantities were synthesized through the one-pot hydrothermal synthesis method using CNT and SAPO-34 as composite supporters. The selected CuCe/CNT1-SAPO-34 catalyst exhibits remarkable SCR activity and high H2O/SO2 resistance in a wide temperature range of 200–450 °C. X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), H2-temperature programmed reduction (H2-TPR), and NH3-temperature programmed desorption (NH3-TPD) were used to characterize the physiochemical structure, surface state of active sites reducibility, and surface acidity of the catalysts. The characterization results reveal that CuCe/CNT1-SAPO-34 possesses a hierarchical structure, small particle size, high levels of surface Cu2+, Ce3+ and chemisorbed oxygen, enhanced reducibility, and suitable surface acidity. For comparison, CuCe/CNT1-SAPO-34 (P) mixed mechanically with CuCe/CNT0-SAPO-34 and CNT was investigated through the NH3-SCR with and without H2O/SO2, it also displays lower resistance of H2O and SO2 than CuCe/CNT1-SAPO-34. The catalytic performance made CuCe/CNT1-SAPO-34 a promising catalyst for the NOx emission control from diesel vehicles.

Role of phase in NiMgAl mixed oxide catalysts for CO2 dry methane reforming (DRM)

Supported Ni catalysts are considered promising for dry methane reforming (DRM) because of their low cost and high activity. However, they suffer from coke formation at elevated reaction temperatures, leading to rapid catalyst deactivation. Here, we developed a synthesis route for highly active and stable nickel-based catalysts for DRM by changing the Mg/Al ratio. Manipulation of the Mg/Al ratio in NiMgAl catalysts induces a change in the phases present, which subsequently leads to enhancement in activity and stability. The highest activity and stability were observed when both spinel and periclase phases were present in the catalysts at Mg/Al ratio of 1.5 (Ni-Mg1.5AlOx). Based on X-ray diffraction (XRD), H2 temperature-programmed reduction (TPR), chemisorption, and UV-Vis-NIR characterizations, as well as CO2 temperature-programmed desorption (TPD), we found that the co-existence of spinel and periclase phases is associated with changes in Ni reducibility, basicity, and the location of Ni2+ species. This work demonstrates how a change in phase in catalysts influences key factors determining activity and stability for the design of active and stable catalysts.

Tuning the high-temperature hydrothermal stability of one-pot derived Cu-SSZ-13 in the presence of SO2 for selective catalytic reduction of NOx by ammonia

The high temperature hydrothermal stability in the presence of SO2 of the one-pot synthesized Cu-SSZ-13 was investigated for selective catalytic reduction of NOx by NH3 (NH3-SCR). The uncalcined samples were treated with HNO3 (pH = 1.0–1.1) with different duration (3, 6, and 9 h) and then calcined, finally subjected to 750 oC hydrothermal aging without/with the presence of SO2. Various characterization results indicate that different duration of HNO3 treatment results in dealumination but has almost no effect on the distribution of Al and Si species. In contrast, it leads to difference in the content of Cu species and finally in their distribution. The 6 and 9 h samples contain higher content of more stable Cu species, which contribute to the high hydrothermal stability in the presence of SO2. H2-temperature programmed reduction (H2-TPR) is a powerful technique to reveal the properties of Cu-SSZ-13; the reduction behavior at lower temperatures (Cu2+ → Cu+) determines the NH3-SCR activity whilst the case at higher temperatures (Cu+ → Cu0) determines the high-temperature hydrothermal stability in the presence of SO2. This work demonstrates that the hydrothermal stability of Cu-SSZ-13 in the presence of SO2 can be tuned by engineering the distribution of Cu species via post HNO3 treatment.

Comparative study of hydrodeoxygenation performance over Ni and Ni2P catalysts for upgrading of lignin-derived phenolic compound

To deeply understand the different hydrodeoxygenation (HDO) behavior of the monometallic Ni and Ni2P catalysts in HDO processes, the Ni/SiO2 and Ni2P/SiO2 catalysts were prepared, respectively. The as-prepared catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, X-ray photoelectron spectra (XPS), H2 temperature-programmed reduction (H2-TPR), transmission electron microscope (TEM), NH3 temperature-programmed desorption (NH3-TPD), and CO uptakes. Taking the lignin-derived phenolic compound as raw material, the HDO performance and reaction route of the monometallic Ni and Ni2P catalysts were compared. The results showed that the phosphorization contributed to highly dispersion of active sites, formation of smaller active sites and significantly enhanced acid sites, showing Ni2P/SiO2 catalyst is a bifunctional metal–acid catalyst. For both of the Ni/SiO2 and Ni2P/SiO2 catalysts, the HDO of m-cresol mainly proceeded by the hydrogenation (HYD) step. However, the acid sites on Ni2P/SiO2 catalyst can significantly promote the conversion of oxygenated 3-methylcyclohexanol (MCHnol) to deoxygenated methylcyclohexane (MCH) owing to its strong hydrogenolysis of C–OH bond originated from the bifunctional metal–acid sites. In addition, the unique electron structure of Ni2P phase involved in two different types of sites (tetrahedral Ni(I) and square pyramidal Ni(II)) and the highly dispersed smaller Ni2P particles also contributed to the outstanding HDO performance. Density functional calculation (DFT) calculations clarified that the Ni2P active phase possessed prior ability to cleavage of C–OH bond in comparison with the metallic Ni species. As a result, Ni2P/SiO2 catalyst showed a significantly higher selectivity to MCH (96.3 %) than that of Ni/SiO2 (14.1 %) catalyst at the conditions of 250 ℃ for 240 min.

Interactions of Ni/ZnO with alumina support and their influence on deep reactive adsorption desulfurization

Double hydrolysis mesoporous alumina (DHA) synthesized via hydrothermal technique and used as support for the loading of ZnO and Ni. The desulfurization activities and their interactions of Ni/ZnO/DHA adsorbents were compared with Ni/ZnO supported on commercially prepared alumina (Com). The higher breakthrough desulfurization activity and sulfur adsorption capability of these catalysts are influenced by the binding extant of Zn/Ni atoms with Al2O3 support, more free ZnO/Ni species and the formation of inactive ZnAl2O4 phases. The catalysts were characterized using nuclear magnetic resonance (NMR) spectroscopy, UV–vis diffuse reflectance spectroscopy (UV–vis DRS), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, H2-temperature programmed reduction (H2-TPR) and N2 adsorption-desorption. Desulfurization activity shows that Ni/ZnO/DHA-80 °C catalyst achieved an excellent breakthrough sulfur removal (10 mg/L) up to 30.26 mL responsible for 110.4 mg S/g sulphur adsorption capability. This desulfurization performance is one fourth fold higher as compared to commercial Ni/ZnO/Com catalyst, achieving a compromised desulfurization activity of 1300 mg/L at set 30.26 mL model fuel flow with 38 mg S/g accumulative sulfur capacity. Detailed characterization results show that, the superior desulfurization activity shown by Ni/ZnO/DHA catalyst is due to the presence of meagre amount of unsaturated pentacoordinate Al3+ centers on Ni/ZnO/DHA surface which are responsible for lesser interaction of Ni/ZnO with Al2O4 and reduce the formation of inactive spinal ZnAl2O4 and NiAl2O4 phase even after many regeneration cycles which increases the active ZnO molar concentration as compared to Ni/ZnO/Com catalyst.

Low temperature synthesis of Cu1−xAl2.5 spinel solid solution as sustained release catalyst for methanol to hydrogen

In order to find a method to synthesize spinel solid solution at low temperature, in this paper, pseudo-boehmite and copper nitrate were used as raw materials, and citric acid was used as accelerator for the first time, the Cu1−xAl2.5 spinel solid solutions were synthesized by ball milling treatment of the solid mixture and then calcined at elevated temperatures. The obtained materials were characterized by X-ray diffraction (XRD), Brunner−Emmett−Teller (BET) measurements, H2-temperature programmed reduction (H2-TPR), infrared (IR) and thermogravimetric methods (TG), and the mechanism of citric acid promoting the synthesis of the spinel solid solution was suggested. The results show that an optimal amount of citric acid can significantly promote the formation of the spinel structure, thus substantially decreasing the synthetic temperature from the above 900 °C–700 °C. At 700 °C, the preparation without the accelerator resulted in small amount of the spinel solid solution, while the use of accelerator gave rise to 82.96% spinel solid solution. Importantly, the Cu1−xAl2.5 spinel solid solution prepared at 700 °C demonstrates the best sustained release catalytic performance, and the catalytic activity reached more than 90% and remained stable within 50 h. The findings of this report might be provide guidance for the solid phase preparation of catalysts at relatively lower temperatures, thus facilitating the commercialization of the sustained release catalyst system.

Doping effect of rare earth metal ions Sm3+, Nd3+ and Ce4+ on denitration performance of MnOx catalyst in low temperature NH3-SCR reaction

The MnXOx catalysts (i.e., MnSmOx, MnNdOx, MnCeOx) were prepared by reverse co-precipitation method and used for NH3-SCR reaction. It is found that MnCeOx catalyst presents the best low temperature catalytic activity (higher than 90% NOx conversion in the temperature range from 125 to 225 °C) and excellent H2O + SO2 resistance. In order to explore the reason for this result, the characterization of X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET), H2-temperature programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflaxions infrared Fourier transformations spectroscopy (DRIFTS) were conducted. The obtained results suggest that MnCeOx catalyst shows the largest amount of acid sites and the best reducibility among these MnXOx catalysts. Besides, Ce4+ doping inhibits the crystallization of MnOx catalyst and shows the largest specific surface area. Finally, in situ DRIFTS experiments reveal that NH3-SCR reaction over MnCeOx catalyst follows both Langmuir–Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms, which is through “fast SCR” reaction.

The Promoting Effect of Ti on the Catalytic Performance of V-Ti-HMS Catalysts in the Selective Oxidation of Methanol

The effects of Ti modification on the structural properties and catalytic performance of vanadia on hexagonal mesoporous silica (V-HMS) catalysts are studied for selective methanol-to-dimethoxymethane oxidation. Characterizations including N2 adsorption–desorption (SBET), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS UV-Vis), Micro-Raman spectroscopy, FTIR spectroscopy, and H2 temperature-programmed reduction (H2-TPR) were carried out to investigate the property and structure of the catalysts. The results show that Ti can be successfully incorporated into the HMS framework in a wide range of Si/Ti ratios from 50 to 10. Ti modification can effectively improve the distribution of vanadium species and thus enhance the overall redox properties and catalytic performance of the catalysts. The catalytic activity of the V-Ti-HMS catalysts with the Si/Ti ratio of 30 is approximately two times higher than that of V-HMS catalysts with comparable selectivity. The enhanced activity exhibited by the V-Ti-HMS catalyst is attributed to the improved dispersion and reducibility of vanadium oxides.

Rod‐Like MnOx Catalyst Derived from Mn‐MOF‐74 for Chlorobenzene Oxidation at Low Temperature

AbstractIn this study, a series of MnOx catalysts were prepared by pyrolysis of Mn‐MOF‐74 precursors. The calcination temperature had influence on the structure and catalytic performance of MnOx catalysts in the catalytic oxidation of chlorobenzene. Their physicochemical properties were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption, X‐ray photoelectron spectroscopy (XPS), H2 temperature programmed reduction (H2‐TPR) and Fourier transform infrared (FTIR), respectively. The order of catalytic activity was as follows: rod‐like MnOx‐700 > rod‐like MnOx‐600 > boat‐like MnOx‐800. The MnOx‐700 catalysts exhibited excellent activity for chlorobenzene (CB) decomposition, and the T90 (temperature with CB conversion of 90 %) was 225 °C. The main reason was that MnOx‐700 inherited the advantage of Mn‐MOF‐74 with high specific surface area, and had higher ratio of Mn3+/Mn4+ (2.51) and Osur/Ototal (0.53). Meanwhile, the MnOx‐700 can maintain over 90 % CB conversion at elevated temperature for 100 h. This work can provide an idea for the further development of high efficiency catalysts prepared via MOF‐template in the CB decomposition.

CO Methanation over NiO-CeO2 Mixed-Oxide Catalysts Prepared by a Modified Co-Precipitation Method: Effect of the Preparation pH on the Catalytic Performance.

In this study, a series of NiO-CeO2 mixed-oxide catalysts have been prepared by a modified co-precipitation method similar to the one used for the synthesis of hydrotalcites. The syntheses were carried out at different pH values (8, 9 and 10), in order to determine the influence of this synthetic variable on the properties of the obtained materials. These materials were characterized by using different techniques, such as TGA, XRD, ICP, N2 adsorption-desorption isotherms, H2 temperature-programmed reduction (H2-TPR), and electron microscopy, including high-angle annular dark-field transmission electron microscopy (HAADF-TEM) and EDS. The characterization results revealed the influence of the preparation method, in general, and of the pH value, in particular, on the textural properties of the oxides, as well as on the dispersion of the Ni species. The catalyst prepared at a higher pH value (pH = 10) was the one that exhibited better behavior in the CO methanation reaction (almost 100% CO conversion at 235 °C), which is attributed to the achievement, under these synthetic conditions, of a combination of properties (metal dispersion, specific surface area, porosity) more suitable for the reaction.

Enhanced Basicity of MnOx-Supported Ru for the Selective Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid.

The present study focused on developing a stable basic MnOx support for Ru (RuMn) for the efficient oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) in water in the absence of an external base. A series of MnOx supports, synthesized via hydrothermal approach using urea as precipitant, was prepared by thermal treatment at various temperatures (300-800 °C) before doping with Ru. The RuMn-2 (1 wt % Ru, MnOx calcined at 400 °C) possessed a large number of basic sites (1.72 mmol g-1 ) based on CO2 temperature-programmed desorption analysis, affording an FDCA yield of 87 % with a turnover frequency of 22 h-1 . Transmission electron microscopy energy-dispersive X-ray spectroscopy elemental mapping of RuMn-2 showed a high dispersion of Ru over the surface of MnOx, contributing to the efficient HMF oxidation. Moreover, X-ray diffraction, X-ray photoelectron spectroscopy, and H2 temperature-programmed reduction indicated that the predominant MnO2 phase (ϵ-MnO2 ) played a vital role in HMF oxidation. RuMn-2 was recyclable for up to four runs without significant loss in the activity and retained its structural integrity.

Tungsten Oxide Modified V2O5-Sb2O3/TiO2 Monolithic Catalyst: NH3-SCR Activity and Sulfur Resistance

In this study, a V2O5-Sb2O3/TiO2 monolithic catalyst was modified by introducing WO3. The WO3-modified catalyst exhibited enhanced catalytic activity in the measuring temperature range of 175–320 °C. The changes in dispersion of vanadia species were investigated by ultraviolet-visible (UV-Vis) spectroscopy and H2 temperature-programmed reduction (H2-TPR). A durability test was conducted in a wet SO2-containing atmosphere at 220 °C for 25 h. The sulfate deposition was estimated by temperature-programmed decomposition (TPDC) of sulfates, thermo-gravimetric (TG) analysis, and temperature-programmed desorption (TPD) of NH3. Isothermal SO2 oxidation and temperature-programmed surface reaction (TPSR) of NH4HSO4 with NO were performed. Based on these characterizations, effects of WO3 modification on the sulfate tolerance of the catalyst were explored.

Al2O3 and phosphorus effect on the active phase and catalytic performance of Ni–Mo catalysts prepared by coprecipitation in hydrodesulfurization of benzothiophene

With the Mo, Ni acting as active constituents and Al2O3, phosphorus acting as additive, Ni-Mo-P-Al unsupported catalyst is synthesized by coprecipitation route. This catalyst is applied in the fluid-bed desulfurization process, with fluid catalytic cracking(FCC) diesel oil serving as the model sulfur compound. The catalysts are characterized by X-ray diffraction (XRD), specific surface area (BET), N2 adsorption and desorption, temperature-programmed desorption of ammonia (NH3-TPD), transmission electron microscopy (TEM), infrared Spectrum (FT-IR), H2 temperature-programmed reduction(H2-TPR), Laser Raman spectroscopy(LRS) and Gas chromatography(GC-PFPD) techniques. It shows that the introduction of Al2O3 contributes a higher surface area and pore volume to the catalysts. With phosphorus addition, the amount of tetrahedral Mo species decreased, and the number of octahedral Mo species increased. The catalyst acidity is changed from strong to weak, and more dispersed MoS2 particles formed with the formation of the Ni–Mo–S phase. At 280 °C, a hydrogen pressure of 4 MPa, an liquid hourly space velocity(LHSV) of 2.0 h−1 and a hydrogen-to-oil ratio of 500, the desulfurization rate reaches 99.8% and the sulfur concentrations decrease from 3950 μg/g to 7.9 μg/g.