Surface Acid Sites Research Articles

Ozone-assisted oxidation of methyl ethyl ketone over mesoporous MnOx/γ-Al2O3 catalysts

Mesoporous MnOx/γ-Al2O3 (MA) catalysts were synthesized using two different manganese precursors (acetate and nitrate forms) to remove methyl ethyl ketone (MEK) via ozonation at room temperature. The MA catalyst prepared with the acetate precursor (MA-A) showed higher catalytic performance in the decomposition of MEK and ozone compared with the MA catalyst prepared with the nitrate precursor. Based on the N2 physisorption and high-resolution transmission electron microscopy, the superior activity of MA-A could be attributed to its large surface area and pore volume, as well as the increased dispersion of MnOx particles. In addition, an appropriate strength of surface acid sites and a higher ratio of active Mn3+/Mn4+ on MA-A resulted in the improved activity.

Facile Preparation of CeO2 Supported on Graphene Oxide Sheets for NH3‐SCR: Improvement of Catalytic Activity and SO2 Tolerance

AbstractIn this paper, a series of highly dispersed CeO2 catalysts on graphene oxide sheets (GO) were prepared by simple impregnation method. The catalysts were applied for selective catalytic reduction(SCR) of NO with NH3. Compared with the 5 wt %CeO2/GO and 15 wt %CeO2/GO catalysts, 10 wt %CeO2/GO catalyst exhibited better catalytic performance in the temperature range of 175–325 °C and higher SO2 resistance at 275 °C. The as‐prepared catalysts were characterized by TEM, AFM, XPS, XRD, BET, H2‐TPR, NH3‐TPD and FT‐IR, respectively. The characterization results indicated that 10 wt %CeO2/GO catalyst possessed larger specific surface area, enriched surface acidic sites, high redox capacity and oxygen vacancies. In addition, Ce3+ on the surface of CeO2/GO catalyst could reduce the oxidation property of SO2, thus improving the SO2 resistance of the catalyst. Meanwhile, the stability of 10 wt %CeO2/GO catalyst was tested. At 275 °C, the NO conversion maintained at 94 % within 30 hours, suggesting the excellent stability.

Continuous hydrogenation of CO2-derived ethylene carbonate to methanol and ethylene glycol at Cu-MoOx interface with a low H2/ester ratio

The Cu-based catalysts have been widely employed in the hydrogenation of CO2-derived ethylene carbonate (EC) to methanol (MeOH) and ethylene glycol (EG), but still suffered from some problems such as excess hydrogen/ester ratio, unsatisfactory MeOH selectivity and catalyst stability & deactivation. Herein, a MoOx-promoted Cu/SiO2 catalyst, which was prepared via a one-pot modified hydrothermal method and derived from copper phyllosilicate precursors, exhibited superior catalytic performance (89% MeOH yield and 99% EG yield) and good stability (>150 h) at a H2/EC ratio (20). Remarkably, the turnover frequency (TOF) and space time yield of MeOH (STYMeOH) reached up to 17.5 h−1 and 0.207 g⋅gcat−1⋅h−1, respectively, which are among the highest values in the literature data. The characterization results and kinetic studies revealed that modification of Cu species by MoOx obviously changed the electronic properties of Cu species, reduced the activation energy and enhanced the Cu+/(Cu0 + Cu+) ratios. Such modification may lead to possible formation of Cu-O-Mo bond between Cu species and MoOx species located on the periphery of Cu-MoOx interface, which might strengthen the adsorption and activation of EC, stabilize the Cu nanoparticles, and thus improve the selectivity to MeOH and catalyst stability. In addition, MoOx decoration had obvious effect on the strength and quantity of the surface acid sites.

Dimethyl carbonate production via transesterification reaction using nitrogen functionalized graphene oxide nanosheets

Nitrogen-functionalized graphene oxide (GO) nanocatalysts were prepared using ammonia, methylamine, ethylamine, and hydrazine hydrate as a nitrogen source. Nanocatalysts samples were thoroughly characterized using XRD, Raman, FTIR, XPS, FESEM, TEM, and TGA techniques. Quantitative and qualitative analyses of surface acidic and basic sites were done by NH3- and CO2-TPD techniques. Nanocatalysts were further examined for DMC production via transesterification reaction of propylene carbonate (PC) with CH3OH. Quantitative analysis of nitrogen-containing functional groups in the prepared sample with respect to other functional moieties was performed. Among various nanocatalysts, ammonia functionalized GO (AGO) was found to be the best for DMC production. At optimized reaction conditions of temperature (180 °C), time (6 h), and catalyst dose (1 wt% with respect PC), the highest DMC yield of ∼50% was observed. Reusability studies using AGO nanocatalyst were conducted up to four consecutive test cycles to evaluate catalysts' potentiality towards DMC synthesis. Thus, N-functionalized GO is a useful metal-free nanocatalyst that could also be explored for other chemical processes.

Selective catalytic reduction of NO by Co-Mn based nanocatalysts

Abstract One of the most significant aspects in selective catalytic reduction (SCR) of nitrogen oxides (NOx) is developing suitable catalysts by which the process occurs in a favorable way. At the present work SCR reaction by ammonia (NH3-SCR) was conducted using Co-Mn spinel and its composite with Fe-Mn spinel, as nanocatalysts. The nanocatalysts were fabricated through liquid routes and then their physicochemical properties such as phase composition, degree of agglomeration, particle size distribution, specific surface area and also surface acidic sites have been investigated by X-ray diffraction, Field Emission Scanning Electron Microscope, Energy-dispersive X-ray spectroscopy, energy dispersive spectroscopy mapping, Brunauer–Emmett–Teller, temperature-programmed reduction (H2-TPR) and temperature-programmed desorption of ammonia (NH3-TPD) analysis techniques. The catalytic activity tests in a temperature window of 150–400 °C and gas hourly space velocities of 10,000, 18,000 and 30,000 h−1 revealed that almost in all studied conditions, CoMn2O4/FeMn2O4 nanocomposite exhibited better performance in SCR reaction than CoMn2O4 spinel.

An innovative nanocatalyst α-Fe2O3/AlOOH processed from gibbsite rubbish ore for efficient biodiesel production via utilizing cottonseed waste oil

A novel dispersed α-Fe2O3 on AlOOH (Fe2+/Fe3+/AlOOH) acid catalyst synthesized via utilizing a deposition hydrothermal route and thoroughly characterized using XRD, SAED-TEM, FTIR, N2 sorptiometry and XPS measurements was employed for biodiesel production via trans-esterification of waste cooking cottonseed oil (WCO). The resulting catalysts own high surface texturing and acid sites loading characteristics especially 12% Fe2+/Fe3+/AlOOH that owns the highest surface area value (323 m2 g−1), uniform 4 nm mesopores, and high total acid sites loading of 0.45 mmol g−1. The optimum conditions for the transesterification of waste cooking oil (WCO) of the latter catalyst were 60 °C, methanol:WCO molar ratio of 6:1, 3% catalyst mass ratio, and 180 min reaction time to achieve 95% FAME yield. This catalyst exhibited high reusability and enabled facile separation and production of high quality biodiesel comparable to the universal ASTM standards. XPS results indicated that the catalytic reaction is promoted on the 12% catalyst when Fe3+/Fe2+ atomic ratios equal 4:1 is combined with AlOOH of appreciable OH bonds. Although 8% catalyst exposed 100% ratio of AlOOH as the 12% catalyst however, the strong interaction exhibited in the later catalyst besides boosting the ratio of Fe3+ that owns two surface active sites; in front of only one on the former, appears to enhance the FAME yield. The calculated activation energy of the reaction indicates a value of 51.54 KJ mol−1 and from the thermodynamic parameters (ΔH‡, ΔS‡ and ΔG‡) the reaction appears to be non-spontaneous and thus accommodated endothermicity beside an entropy decrease.

Simultaneous removal of NO and dichloromethane (CH2Cl2) over Nb-loaded cerium nanotubes catalyst

Herein, a series of niobium oxide supported cerium nanotubes (CeNTs) catalysts with different loading amount of Nb2O5 (0–10 wt.%) were prepared and used for selective catalytic reduction of NOx with NH3 (NH3-SCR) in the presence of CH2Cl2. Commercial V2O5-WO3-TiO2 catalyst was also prepared for comparison. The physcial properties and chemical properties of the Nb2O5 loaded cerium nanotubes catalysts were investigated by X-ray diffractometer, Transmission electron microscope, Brunauer-Emmett-Teller specific surface area, H2-temperature programmed reduction, NH3-temperature programmed desorption and X-ray photoelectron spectroscopy. The experiment results showed that the loading amount of Nb2O5 had a significant effect on the catalytic performance of the catalysts. 10 wt.% Nb-CeNTs catalyst presented the best NH3-SCR performance and degradation efficiency of CH2Cl2 among the prepared catalysts, due to its superior redox capability, abundant surface oxygen species and acid sites, the interaction between Nb and Ce, higher ratio of Nb4+/(Nb5++ Nb4+) and Ce3+/(Ce3+ + Ce4+), as well as the special tubular structure of cerium nanotube. This study may provide a practical approach for the design and synthesis of SCR catalysts for the simultaneously removal NOx and chlorinated volatile organic compounds (CVOCs) emitted from the stationary industrial sources.

A strategy for constructing highly efficient yolk-shell Ce@Mn@TiOx catalyst with dual active sites for low-temperature selective catalytic reduction of NO with NH3

In this work, Ce@MnOx catalysts with core-shell structure were obtained via simple hydrothermal treatment, and the redox capacity can be effectively improved through co-existence of Ce and Mn. Since the strong oxidation capacity of MnOx can lead to the peroxidation of ammonia, the redox capacity can be suppressed with the decrease of manganese content. However, in the case of low manganese content, it is discovered that the surface acidity is very weak and the ammonia adsorption behavior on the catalyst is limited, which is detrimental to the NH3-SCR process. To solve this problem, a series of yolk-shell structured Ce@Mn@TiOx were accordingly constructed, where the TiO2 shell can provide more surface acid sites to promote the adsorption and activation of ammonia. As expected, the Ce@Mn@TiOx exhibits excellent catalytic performance for NH3-SCR at low temperature and possesses a relatively wide working temperature window. More importantly, the TiO2 shell could protect the active sites from water vapor competitive adsorption as well as sulfur attack. Thus, the Ce@Mn@TiOx-10% catalyst exhibited satisfied water vapor resistance in the SCR process, and its sulfur tolerance was also improved to a certain extent. In situ DRIFTs analysis demonstrated that the Ce@Mn@TiOx-10% catalyst mainly follows the L-H reaction mechanism. Consequently, the separation of acid and redox sites has been successfully accomplished by the construction of Ce@Mn@TiOx with yolk-shell structure, where the outer shell (TiO2) mainly enhanced the adsorption capacity of ammonia and protected active centers from attacking by moisture and even sulfur species, while the MnOx interlayer enhanced the interfacial electronic interaction of Ce/Mn and ensured efficient redox cycle during the NH3-SCR process.

Role of silicotungstic acid on the catalytic performance over CeO2‐HSiW catalysts for selective catalytic reduction of NOx with NH3

The CeO2 modified by silicotungstic acid (impregnation method [SiW/CeO2] and one pot method [CeO2‐Si‐W]) was investigated in the NH3‐SCR reaction. The surface nitrate species and surface acid sites were improved by the introduction of silicotungstic acid into CeO2, which stopped forming stable nitrate, and then improved the N2 selectivity. The interaction between Ce and W species existed and caused the formation of Ce2(WO4)3 at CeO2‐Si‐W, resulting in the abundance of unsaturated W=O, which contributed to the generation of Brønsted acid sites and was responsible for the superior SCR performance. Thus, CeO2‐Si‐W exhibited the best NOx conversion and nearly 100% NOx conversion was obtained at 225–450°C.

Ca Doping Effect on the Competition of NH3–SCR and NH3 Oxidation Reactions over Vanadium-Based Catalysts

The Ca poisoning effect constrains vanadium-based catalysts from further application in high-calcium content flue gas, and the deactivation effect of CaO on V2O5–WO3/TiO2 (VWT) and V2O5/TiO2 (VT) catalysts has been investigated from a new perspective. As the NH3 selective catalytic reduction (NH3–SCR) results showed, the NO conversion at 400 °C declined by 71.7% for VT and by 34.8% for VWT after CaO doping, and the decrease in NO conversion for NH3–SCR at temperatures greater than 300 °C was mainly caused by the competition of the NH3 oxidation reaction. The characterization of catalysts by NH3–SCR, XRD, Raman spectroscopy, H2-TPR, NH3-TPD, and TEM showed that the number of surface acid sites decreased and that the oxidation and reduction properties of the catalysts all deteriorated after CaO doping, which is the primary reason for the decrease in NO conversion. CaO also affected NH3 oxidation, and the L-NH3 adsorbed on CaO favored the NH3 oxidation reaction, as DRIFTS showed. NH3 reaction pathways changed by CaO doping because NH3 oxidation becomes more competitive at temperatures greater than 300 °C. Density functional theory (DFT) calculations confirmed the NO formation pathway on CaO, and the competition mechanism of NH3–SCR and NH3 oxidation reactions has been described, which has hardly been reported.

A Facile Route to Prepare PbZr Nanocomposite Catalysts for the Efficient Synthesis of Diphenyl Carbonate

Diphenyl carbonate is a versatile chemical intermediate and key building block for the synthesis of polycarbonates. A facile route to prepare PbZr nanocomposites were developed using different precipitants to investigate the effect on the catalytic activity of the solid acid catalysts. The structure–performance relationship of the nanocomposites, dispersion of active components and structure stability, and the catalytic performance were thoroughly analyzed. The results showed that there existed the interaction between Zr and Pb, which induced the homogenous dispersion of Pb and high surface acid sites that could enhance the catalytic activities. Among the catalysts, PbZr–NH4OH represented the best catalytic performance and superior stability, indicating that NH4OH was more favorable compared with sodium hydroxide, ammonium carbonate and urea. The research provides a valuable reference in a wide range application of nanocomposite preparation for the effective and clean production of various carbonates.

Ce–Si Mixed Oxide: A High Sulfur Resistant Catalyst in the NH3–SCR Reaction through the Mechanism-Enhanced Process

Investigating catalytic reaction mechanisms could help guide the design of catalysts. Here, aimed at improving both the catalytic performance and SO2 resistance ability of catalysts in the selective reduction of NO by NH3 (NH3-SCR), an innovative CeO2-SiO2 mixed oxide catalyst (CeSi2) was developed based on our understanding of both the sulfur poisoning and reaction mechanisms, which exhibited excellent SO2/H2O resistance ability even in the harsh working conditions (containing 500 ppm of SO2 and 5% H2O). The strong interaction between Ce and Si (Ce-O-Si) and the abundant surface hydroxyl groups on CeSi2 not only provided fruitful surface acid sites but also significantly inhibited SO2 adsorption. The NH3-SCR performance of CeSi2 was promoted by an enhanced Eley-Rideal (E-R) mechanism in which more active acid sites were preserved under the reaction conditions and gaseous NO could directly react with adsorbed NH3. This mechanism-enhanced process was even further promoted on sulfated CeSi2. This work provides a reaction mechanism-enhanced strategy to develop an environmentally friendly NH3-SCR catalyst with superior SO2 resistance.

Investigation of crystal size effect on the NOx storage performance of Pd/SSZ-13 passive NOx adsorbers

The crystal size effect on the NOx adsorption and desorption over Pd/SSZ-13 passive NOx adsorbers (PNA) was investigated. SSZ-13 zeolites with various crystal size (0.4, 0.8, and 2.3 μm) presented highly textural uniformity. 0.4 μm Pd/SSZ-13 showed the highest NOx storage capacity and robust hydrothermal stability. According to the combined XRD, HAADF-STEM, H2-TPR, and CO-TPR results, ionic Pdn+ ions were dispersed better on Pd/SSZ-13 with a smaller crystal size. The nature of Pdn+ ion distribution was investigated by bulky and external surface acidic characterization. It was found that more external surface acid sites were formed on as-prepared smaller-sized SSZ-13 zeolites, which contributed to easier Pdn+ ion diffusion. The kinetic study showed that the NOx adsorption on Pd/SSZ-13 obeyed the pseudo-second-order model and the NOx adsorption activation energy for Pd/SSZ-13 was 25∼38 kJ/mol, independent of the crystal size. This work might guide the design of state-of-the-art zeolite supported PNAs.

Optimizing acido-basic profile of support in Ni supported La2O3+Al2O3 catalyst for dry reforming of methane

The increasing alarm of global warming always draws interest in reactions like dry reforming of methane (DRM) where both global warming gases (CO2 and CH4) are converted into value-added chemical building blocks, such as syngas. Nickel catalyst active sites along with support acid-base profiles play a key role in DRM. Herein, xLa2O3+(100-x) Al2O3 (x = 0, 10, 15, 20%) supports are prepared and followed by NiO dispersion over the produced support by impregnation method. It was tested for DRM reaction and characterized with TGA, XRD, TEM, IR, Surface area and porosity measurement, H2-TPR, CO2-TPD and NH3-TPD techniques. Upon increasing the basic lanthana proportion in the acidic alumina support, the crystallinity of alumina and acidity of total support decline. Up to 15% Lanthana addition in support claims a low acid and rich basic surface including super basic sites (related to unidentate carbonates) which governed optimum catalytic performance 64% CH4 conversion, 79% CO2 conversion and H2/CO ~ 1 up to 460-min in time on stream test. 20% lanthanum oxide loading led to inferior performance due to rapid loss of surface area, pore-volume, pore diameter, acidity and medium basic strength sites. Fine-tuning of acid-base lanthana-alumina support with dispersed Ni species are a means for understanding DRM.

Influence of Alumina Precursor Properties on Cu-Fe Alumina Supported Catalysts for Total Toluene Oxidation as a Model Volatile Organic Air Pollutant

The structure–property relationship of catalytic supports for the deposition of redox-active transition metals is of great importance for improving the catalytic efficiency and reusability of the catalysts. In this work, the role of alumina support precursors of Cu-Fe/Al2O3 catalysts used for the total oxidation of toluene as a model volatile organic air pollutant is elucidated. Surface characterization of the catalysts revealed that the surface area, pore volume and acid site concentration of the alumina supports are important but not the determining factors for the catalytic activity of the studied catalysts for this type of reaction. The determining factors are the structural order of the support precursor, the homogeneous distribution of the catalytic sites and reducibility, which were elucidated by XRD, NMR, TEM and temperature programed reduction (TPR). Cu–Fe/Al2O3 prepared from bayerite and pseudoboehmite as highly ordered precursors showed better catalytic performance compared to Cu-Fe/Al2O3 derived from the amorphous alumina precursor and dawsonite. Homogeneous distribution of FexOy and CuOx with defined Cu/Fe molar ratio on the Al2O3 support is required for the efficient catalytic performance of the material. The study showed a beneficial effect of low iron concentration introduced into the alumina precursor during the alumina support synthesis procedure, which resulted in a homogeneous metal oxide distribution on the support.

Promoting effect of Pd modification on the M/TiO2 (M = V, Ce, Mn) catalyst for catalytic oxidation of dichloromethane (DCM)

To improve the catalytic oxidation of dichloromethane, a series of Pd modifying M4/TiO2(M = V, Ce, Mn) catalysts were prepared by impregnation method and characterized by ICP-MS, XRD, BET, O2/NH3-TPD, H2-TPR, XPS and DRIFT. It was found that Pd0.12V4/TiO2 catalyst possessed the best catalytic performance with excellent CO2 selectivity and stability compared to other catalysts. Characterization results illustrated that Pd modification improved the redox ability of catalyst to oxidize DCM to intermediates mainly CO, and the addition of Pd also slightly improved the surface adsorbed oxygen species, which played a great role in further oxidation of CO to CO2. Meanwhile, the V2O5 loading can maximize the acidity of catalyst, which is beneficial for the adsorption of DCM and cleavage of C-Cl bond. The reaction mechanism was concluded that DCM firstly adsorbed on surface acid sites to be further oxidized to CO which then was oxidized to CO2 by the surface adsorbed oxygen species.

Propane Dehydrogenation on Ga2O3-Based Catalysts: Contrasting Performance with Coordination Environment and Acidity of Surface Sites

α-Ga2O3, β-Ga2O3, and γ-Ga2O3 as well as the silica-supported catalysts γ-Ga2O3/SiO2, β-Ga2O3/SiO2, and Ga(NO3)3-derived Ga/SiO2 were prepared, characterized, and evaluated for propane dehydrogenation (PDH) at 550 °C. The coordination environment and acidity of surface sites in stand-alone and SiO2-supported Ga2O3 catalysts were studied using FTIR, 15N dynamic nuclear polarization surface-enhanced NMR spectroscopy (15N DNP SENS), and DFT modeling of the adsorbed pyridine probe molecule. The spectroscopic data suggest that the Lewis acidic surface Ga sites in γ-Ga2O3 and β-Ga2O3 (the latter obtained from colloidal nanocrystals of γ-Ga2O3 via thermal treatment at 750 °C) are similar, except that β-Ga2O3 contains a larger relative fraction of weak Ga3+ Lewis acid sites. In contrast, α-Ga2O3 features mostly strong Lewis acid sites. This difference in surface sites parallels their difference in catalytic activities: i.e., weak Lewis acid surface sites are more abundant in β-Ga2O3 relative to α-Ga2O3 and γ-Ga2O3 and the increased relative abundance of weak Lewis acidity correlates with a higher initial catalytic activity in PDH, 0.41 > 0.28 > 0.14 mmol C3H6 m–2 (Ga2O3) h–1 at 550 °C, for respectively β-, α-, and γ-Ga2O3 with initial propene selectivities of 86, 83, and 88%. Dispersion of γ-Ga2O3 or β-Ga2O3 on a silica support introduces strong as well as abundant weak Brønsted acidity to the catalysts, lowering the PDH selectivity. The γ-Ga2O3/SiO2 catalyst was slightly more active than β-Ga2O3/SiO2 in PDH (Ga normalized activity) with initial propene formation rates of 11 and 9 mol C3H6 mol Ga–1 h–1 (sel = 76 and 73%, respectively). However, these catalysts deactivated by ca. 55% within 100 min time on stream (TOS) due to coking. In contrast, Ga/SiO2, with mostly tetracoordinated surface Ga sites and abundant, strong Brønsted acid sites, gave a lower activity and selectivity in PDH (3.5 mol C3H6 mol Ga–1 h–1 and 49%, respectively) but showed no deactivation with TOS. DFT calculations using a fully dehydroxylated oxygen-deficient model β-Ga2O3 surface show that tetra- and pentacoordinated Ga Lewis acid sites bind pyridine more strongly than tricoordinated Ga sites and a higher relative fraction of strong Lewis acid sites correlates with increased coking. Overall, our results indicate that weakly Lewis acidic, tricoordinated Ga3+ sites are likely driving the superior PDH activity of β-Ga2O3.

Probing the role of surface acid sites on the photocatalytic degradation of tetracycline hydrochloride over cerium doped CdS via experiments and theoretical calculations.

Surface acid site regulation of photocatalysts is a promising strategy to improve their performance. Herein, surface acid sites of cadmium sulfide were rationally regulated by cerium doping, which resulted in significantly increased photocatalytic activity for tetracycline hydrochloride (TC-HCl) degradation. The generated Brønsted acid sites were verified to favor the adsorption of organic molecules because of their strong affinity. Meanwhile, Lewis acid sites acted as the active sites for C-C bond cleavage via a nucleophilic substitution process, which was testified by the Fukui function and electrostatic potential. Besides, Ce3+ doping suppressed the recombination of electron-hole pairs, which also boosted the performance of TC-HCl degradation. Moreover, the degradation pathway of TC-HCl was deduced based on theoretical calculations and HPLC-MS results. The toxicity of pollutants and intermediates was also evaluated. This work provided new insight into the rational design and preparation of highly efficient photocatalysts for environmental purification.

Visible light driven enhancement in photodegradation of organic dyes using FexTi1-xO2 thin films

Fe doped TiO2 thin films (Fe, 0.02, 0.03, 0.04 and 0.05 mol %) were prepared using dip coating method. Dip coating method provides thin films of self-assembly with sol gel technique. The prepared thin films were subjected to different characterization studies. The structural properties of samples were analyzed with powder X-Ray diffraction method. It is observed that Fe ion incorporation has modified the crystallite size of TiO2 particle significantly which can have effect on the wavelength of the light source required for the photocatalytic process. The surface morphological properties were investigated via FESEM and AFM techniques. The higher concentration of Fe doped TiO2 thin films exhibit the larger surface area and roughness which leads to better enhancement for catalytic properties. The optical absorption studies showed the absorption edge of doped TiO2 samples has shifted towards longer wavelength region. The catalytic efficiency of prepared samples was investigated by the degradation of organic pollutants methylene blue and Congo red dyes and the results showed enhanced chemical reaction ensued between the methylene blue and Fe TiO2 samples. Further the treated water was used to grow plant like green gram (Vigna radiata) and the growth of plant was studied. The anatase phase, narrowing band gap, acidic surface sites and large surface area of Fe doped TiO2 thin film infer the sample as an efficient photocatalyst for environmental purification.

Effect of mass ratio on micro-mesoporous Cu-SSZ-13/CeWTi composite catalysts for the selective catalytic reduction of NO with ammonia.

A series of micro-mesoporous SSZ-13/CexWyTiz composites with different zeolite/oxide ratios were synthesized using a one-step crystallization method. The effects of the mass ratio on the crystal form, specific surface area, pore structure, surface element properties, redox properties, surface acidity and deNOx performance of the Cu-SSZ-13/CeWTi composite catalysts were investigated using X-ray diffractometry (XRD), Brunauer–Emmett–Teller analysis (BET), X-ray photoelectron spectroscopy (XPS), H2 temperature programmed reduction (H2-TPR) and NH3 temperature programmed desorption (NH3-TPD). The results reveal that the Cu-SSZ-13/CeWTi composite catalysts formed a micro-mesoporous structure. The increase in the mass ratio leads to the increased microporous ratio of the composite catalysts, the improved crystal structure of SSZ-13 and a higher specific surface area and pore volume, which is conducive to enhancing the low-temperature deNOx activity, but its high-temperature performance (450 °C and above) decreases. The introduction of micropores into mesoporous materials can result in the production of more Ce4+, surface chemisorption oxygen species Oα and acid sites. The Cu-SSZ-13/CeWTi composite catalyst with a mass ratio of 1 : 4 demonstrated the best micro-mesoporous ratio, low-temperature selective catalytic reduction (SCR) performance and hydrothermal stability.