Homogeneous Deposition Precipitation Research Articles

Fischer–Tropsch synthesis: The effect of hydrophobicity on silica-supported iron catalysts

This work focuses on the effect of surface hydrophobicity of SiO2 supports on the performance of SiO2-supported Fe catalysts during Fischer–Tropsch synthesis (FTS). Three different hydrophobized SiO2 supports were synthesized by varying the amount of the dichlorodimethylsilane used for the hydrophobization of the hydrophilic mesoporous SiO2 gel. Fe metal of approximately 9wt% was loaded on the hydrophilic SiO2, and three hydrophobized SiO2 supports by homogeneous deposition precipitation. The wholly hydrophobized SiO2 surface improved the catalytic activity of Fe catalysts because the hydrophobized SiO2 increased the reducibility of the iron oxide and inhibited readsorption of water over the surface of the Fe catalyst, therefore creating more available active sites for the adsorption of CO. Also, hydrophobized SiO2 decreased the CH4 selectivity and C2–C4 selectivity and increased C5+ selectivity of the Fe catalysts due to the promotion of chain growth by the hydrophobized SiO2. Furthermore, the hydrophobized SiO2 decreased the CO2 selectivity of the Fe catalysts because the hydrophobized SiO2 hindered the readsorption of water over the surface of the Fe catalysts, which leads to the inhibition of water gas shift reaction and subsequently the hindering of the CO2 formation.

Catalytic Vapor Phase Oxidation of Glycerol to Glyceric Acid Over Activated Carbon Supported Gold Nanocatalysts

A series of activated carbon (AC) supported Au nanocatalysts with different loadings of Au were prepared by using the homogeneous deposition–precipitation (HDP) method. The samples were characterised with myriad techniques such as X-ray diffraction (XRD), CO-chemisorption, N2 adsorption–desorption measurements, transmission electron microscopy (TEM), inductively coupled plasma-optical emission spectrometer (ICP-OES) and X-ray photoelectron spectroscopy (XPS) to understand the structural and textural properties in detail. The catalysts were tested for the vapour phase oxidation of glycerol to glyceric acid under base-free medium in an aerobic condition at normal atmospheric pressure. The Au/AC nanocatalysts with smaller size Au particles ([Formula: see text][Formula: see text]nm) showed higher glycerol conversion and selectivity for glyceric acid, and also a longer catalyst life. While the larger Au particles ([Formula: see text][Formula: see text]nm) showed less activity and selectivity. Among all the nanocatalysts tested, the 1.0[Formula: see text]wt.% Au/AC sample having smaller particle size of Au showed the best catalytic performance in terms of glycerol conversion and glyceric acid selectivity. These results suggest that the oxidation activities of Au/AC nanocatalysts are strongly influenced by the size of Au nanoparticle, nature of the support material and through a metal-support interaction.

Improved photoluminescence property by homogeneous deposition-precipitation method for Eu2+ doping in Si–N–O frameworks

The highly dispersed Eu2+ activators with improved photoluminescence property have been successfully achieved by a homogeneous deposition-precipitation (DP) process and the followed heat treatment using SrSi2O2N2 lattice as the typical Si–N–O frameworks. The phase composition, photoluminescence properties and surface states were investigated by XRD, fluorescence spectrophotometer, FESEM and XPS. Compared with the sample prepared by traditional solid state reaction (SSR) method, the luminescence intensity of the SrSi2O2N2: Eu2+ phosphor prepared by DP method exhibits an enhanced luminescence intensity with 1.4 times for green emission peak at 529 nm under excitation of 370 nm. The homogeneous DP process facilitates the uniform distribution of Eu2+ activators in the Si–N–O frameworks and results in a slower decreasing tendency between emission intensity and Eu2+ concentration. The results of FESEM and decay times indicated that the phosphors prepared by DP and SSR method exhibit the characteristic folded platelet-like morphology and similar fluorescence lifetime (918.4 ns and 914.4 ns, respectively). The XPS results revealed that the amount of Sr–O bands in the phosphor prepared by DP method is much higher than that in the sample prepared by SSR method. Interestingly, the SrSi2O2N2: Eu2+ phosphor can be obtained through this DP method even at a low heat treatment temperature (800 °C) under a strongly reducing atmosphere. It is suggested that the deposition-precipitation process will be an efficient synthetic strategy to construct uniform Eu2+ distribution in Si–N–O frameworks and further to enhance the luminescence intensity of the SrSi2O2N2: Eu2+ phosphor.

Heterogeneous catalytic reduction of anthropogenic pollutant, 4-nitrophenol by Au/AC nanocatalysts

Activated carbon-supported gold nanocatalysts (Au/AC) were synthesized by the homogeneous deposition–precipitation (HDP) method by adding drop-wise of NaBH4 into the aqueous solution of HAuCl4. Catalytic activity of these nanocatalysts was investigated for the reduction of the anthropogenic pollutant, 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The physico-chemical properties of the nanocatalysts were characterized by XRD, TEM, BET surface area, pore size distribution, XPS and UV–Vis spectroscopy techniques. Gold nanoparticles (Au NPs) with high percentage of dispersion on a high surface area activated carbon (AC) support, show excellent catalytic performance in terms of activity and selectivity for 4-NP reduction. The reaction rate was measured to be pseudo-first-order with respect to 4-NP. The pseudo-first-order rate constant and the activation energy were estimated to be 1.2–4.2 × 10−3 s−1 at 25 °C and 26.38 kJ mol−1, respectively. Moreover, the catalytic activity was found to increase with increase in Au content of the catalyst. The reusability of the nanocatalyst showed a better reduction of 4-NP to 4-AP even after 5 successive re-cycles. The foregoing study clearly suggests that synthesis of Au/AC nanocatalysts by HDP method is efficient towards the development of a newer and a novel catalyst.

Influence of co-catalyst amount/size for selective hydrogenation of 1,3-dinitrobenzene over Au-mTiO2 nanocomposites under visible light

This study demonstrates the co-catalytic effect for selective hydrogenation of a particular group in a multifunctional organic compound. Transmission electron microscopy (TEM) studies revealed that Au loaded nanoparticles were found to be of ∼3.89 nm and ∼8.86 nm with 1 wt% and 3 wt% metal loading respectively by homogeneous deposition precipitation (HDP) method over synthesized mesoporous titanium dioxide (m-TiO2) nanoparticles. The Au particles were deposited in the metallic state which was confirmed from X-ray photoelectron spectroscopy (XPS) with a binding energy of 84.0 eV and 87.7 eV credited to 4f5/2 and 4f7/2 spin states respectively. In this Au-mTiO2 heterojunction, metal particles found to be decisive for 100% selective hydrogenation of 1,3-dinitrobenzene under visible light. Predominantly, m-nitroaniline formed when 1,3-dinitrobenzene was treated with 1 wt% Au-mTiO2 whereas 100% photoreduction of both nitro groups occurred with 3 wt% Au-mTiO2. Hence, 1,3-dinitrobenzene exhibited particle size sensitive photocatalytic hydrogenation under mild conditions without using any reducing agent.

Synthesis and Evaluation of Copper-Supported Titanium Oxide Nanotubes as Electrocatalyst for the Electrochemical Reduction of Carbon Oxide to Organics

Carbon dioxide (CO2) is considered as the prime reason for the global warming effect and one of the useful ways to transform it into an array of valuable products is through electrochemical reduction of CO2 (ERC). This process requires an efficient electrocatalyst with high faradaic efficiency at low overpotential and enhanced reaction rate. Herein, we report an innovative way of reducing CO2 using copper-metal supported on titanium oxide nanotubes (TNT) electrocatalysts. The TNT support material was synthesized using alkaline hydrothermal process with Degussa (P-25) as a starting material. Copper nanoparticles were anchored on the TNT by homogeneous deposition-precipitation method (HDP) with urea as precipitating agent. The prepared catalysts were tested in a home-made H-cell with 0.5 M NaHCO3 aqueous solution in order to examine their activity for ERC and the optimum copper loading. Continuous gas-phase ERC was carried out in a solid polymer electrolyte (SPE) reactor. The 10% Cu/TNT catalysts were employed in the gas diffusion layer (GDL) on the cathode side with Pt-Ru/C on the anode side. Faradaic efficiencies for the three major products namely methanol, methane, and CO were found to be 4%, 3%, and 10%, respectively at −2.5 V with an overall current density of 120 mA/cm2. The addition of TNT significantly increased the catalytic activity of electrocatalyst for ERC. It is mainly attributed to their better stability towards oxidation, increased CO2 adsorption capacity and stabilization of the reaction intermediate, layered titanates, and larger surface area (400 m2/g) as compared with other support materials. Considering the low cost of TNT, it is anticipated that TNT support electrocatalyst for ECR will gain popularity.

Effect of preparation methods on the performance of CuFe-SSZ-13 catalysts for selective catalytic reduction of NOx with NH3

CuFe-SSZ-13 catalyst showed excellent performance in the selective catalytic reduction of NOx with NH3 (NH3-SCR) for diesel engine exhaust purification. To investigate the effect of preparation methods on NH3-SCR performance, Fe was loaded into one-pot synthesized Cu-SSZ-13 catalysts through solid-state ion-exchange (SSIE), homogeneous deposition precipitation (HDP) and liquid ion-exchange (IE), respectively. Three CuFe-SSZ-13 catalysts showed similar SO2 resistance, which was better than that of Cu-SSZ-13. The improvement was attributed to the protection of Fe species. Hydrothermal stability of three CuFe-SSZ-13 catalysts was significantly different, which was attributed to the state of active species caused by different preparation methods. Compared with the other two catalysts, more active species existed inside the zeolite pores of CuFe-SSZ-13SSIE. During hydrothermal aging, the aggregation of these active species in the pores caused the collapse of catalyst structure, ultimately leading to the deactivation of CuFe-SSZ-13SSIE. In contrast, Fe species was dispersed better on the surface over CuFe-SSZ-13IE, enhancing the hydrothermal stability of catalysts. Consequently, Fe loading effectively improved the resistance of SO2 and H2O over Cu-SSZ-13. For CuFe-SSZ-13, large amounts of active species located inside the zeolite pores are not beneficial for the hydrothermal stability.

Hydroxyapatite supported gold nanocatalyst for base-free oxidative esterification of 5-hydroxymethyl-2-furfural to 2,5-furan dimethylcarboxylate with air as oxidant

A series of gold (Au) nanocatalysts has been prepared for base-free protocol-oxidative esterification of lignocellulosic biomass derived 5-hydroxymethyl-2-furfural (HMF) to 2,5-furan dimethylcarboxylate (FDMC) in the presence of air. The prepared Au-based nanocatalysts are thoroughly characterized by various analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2-physisorption (adsorption–desorption) method, inductive coupled plasma-atomic emission (ICP-AES) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Moreover, the surface properties of Au-based nanocatalysts were investigated by temperature-programmed desorption of carbon dioxide (CO2-TPD) technique. For a comparison point of view, the activity tests of various prepared metal-based nanocatalysts have also been carried out. Among all, hydroxyapatite (HAP) supported Au nanocatalyst (Au/HAP) prepared by homogeneous deposition–precipitation (HDP) method was found to be the best to give 89.3% yield of FDMC from oxidative esterification of HMF in the presence of air. The excellent yield of FDMC could be attributed to stronger basic sites on the surface of the catalyst. Furthermore, Au/HAP nanocatalyst was simply recovered and reused, which retained its original activity even after five consecutive times without significant loss of original activity, supporting its reusability and stability.

Effect of alkali metals on the performance of CoCu/TiO2 catalysts for CO2 hydrogenation to long-chain hydrocarbons

CoCu/TiO2 catalysts promoted using alkali metals (Li, Na, K, Rb, and Cs) were prepared by the homogeneous deposition-precipitation method followed by the incipient wetness impregnation method. The influences of the alkali metals on the physicochemical properties of the CoCu/TiO2 catalysts and the catalytic performance for CO2 hydrogenation to long-chain hydrocarbons (C5+) were investigated in this work. According to the characterization of the catalysts based on X-ray photoelectron spectroscopy, X-ray diffraction, CO2 temperature-programmed desorption (TPD), and H2-TPD, the introduction of alkali metals could increase the CO2 adsorption and decrease the H2 chemisorption, which could suppress the formation of CH4, enhance the production of C5+, and decrease the hydrogenation activity. Among all the promoters, the Na-modified CoCu/TiO2 catalyst provided the maximum C5+ yield of 5.4%, with a CO2 conversion of 18.4% and C5+ selectivity of 42.1%, because it showed the strongest basicity and a slight decrease in the amount of H2 desorption; it also exhibited excellent catalytic stability of more than 200 h.

Two-dimensional mica nanosheets supported Fe nanoparticles for NH3 decomposition to hydrogen

Two-dimensional mica nanosheets (MS) are employed as support for preparation of Fe/MS catalysts by three different methods namely homogeneous precipitation (HP), impregnation (IM), and deposition precipitation (DP) methods. Their catalytic performances for ammonia decomposition are tested, and their physicochemical properties are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, hydrogen temperature-programmed reduction, X-ray photoelectron spectroscopy, ammonia/hydrogen temperature-programmed desorption, and N2 sorption techniques. The catalytic results show that the preparation methods would remarkably affect the catalytic performance of Fe/MS catalysts, and the Fe/MS catalysts prepared by HP method exhibit the highest catalytic activity. It is revealed that the coexistence of three types of Fe species including Fe3+, Fe2+ and Fe0 in the reduced Fe/MS catalysts are responsible for the ammonia decomposition. The excellent catalytic performance of Fe/MS-HP catalyst is attributed to the highly dispersed Fe species, layered structure of mica, and strong metal-support interactions between Fe and mica. Stability testing shows that the 5%Fe/MS-HP catalyst exhibits high catalytic stability, suggesting a very promising catalyst in ammonia decomposition.

Nanoparticles based on copper deposited on carbon spheres. Preparation, characterization and application for CO2 photo-electrochemical reduction

In this study, we have examined the performance of copper nanoparticles deposited on carbon spheres with a mass weigh of 10wt% (labeled 10Cu-CSs) via photo-electrochemical reduction of carbon dioxide (CO2). The carbon spheres (CSs) were prepared by a chemical vapor deposition method and 10Cu-CSs was made via a homogeneous deposition precipitation method. The materials were characterized by different physico-chemical techniques such as X-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR) and diffuse reflectance (DR) spectroscopy, electrical conductivity and photo-electrochemical studies. The 10Cu-CSs material was studied for the photo-electrochemical reduction of CO2 under visible light illumination. The synthesized material exhibited a single phase monoclinic structure of CuO deposited on CSs as confirmed by XRD, Raman and FTIR spectroscopies results. The semi-conductor property was established by electrical conductivity, and the activation energy obtained was ca. 0.04eV. The UV–visible absorption spectrum showed a direct band gap transition with gap energy of 1.22eV. The material synthesized was a cathode semi-conductor with p-type conductivity. The deposition of copper nanoparticles enhanced the CO2 photo-conversion to formic acid under the reaction conditions. In particular, 10Cu-CSs demonstrated gave formic acid, which was at a higher potential than standard redox potentials of copper. Furthermore, the photo-electrochemical characterization showed that the deposition of the copper onto CSs used as electrode effectively generated photo-induced electron/hole pairs under visible light irradiation leading an enhancement of photo-reduction under visible light in a NaHCO3 electrolyte.

Comparative Study of the Support Role on the Activity of Copper Species for Nitric Oxide Reduction

In this work three different supports (γ-Al2O3, ZSM-5, and SAPO-34) of varying degree of acid sites and textural properties were used to evaluate the influence of support specifics in the Cu/supported nanocatalysts on NO conversion. The nanocatalysts were prepared by homogeneous deposition precipitation (HDP) method and characterized by N2 pore size distribution, TEM, H2-TPR for investigation the reducibility of the copper species and acidity measurement by NH3 adsorption. The Cu/ZSM-5 and Cu/SAPO-34 catalysts were more active for NO conversion than Cu/γ-Al2O3 catalyst. The characterization and conversion differences in the copper supported on different types of support indicated that these differences arise from the differences in surface area, pore size distribution, and acidity of the supports. The higher SCR-DeNO activity of Cu/ZSM-5 and Cu/SAPO-34 nano-catalysts can be explained by higher surface area and acidity of ZSM-5 and SAPO-34 supports. These catalysts also have larger amount of reducible Cu species compared to Cu/γ-Al2O3 which correlates with the structure of the support used. Considering these findings, the NO conversion ability of Cu/supported catalysts has been correlated with support structure and acidity.

Potential of an Alumina-Supported Ni3Fe Catalyst in the Methanation of CO2: Impact of Alloy Formation on Activity and Stability

A promising bimetallic 17 wt % Ni3Fe catalyst supported on γ-Al2O3 was prepared via homogeneous deposition–precipitation for the application in the methanation of CO2 to gather more detailed insight into the structure and performance of the catalyst compared to state-of-the-art methanation systems. X-ray diffraction (XRD) analysis, detailed investigations using scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy analysis (EDX) of single particles as well as larger areas, high-resolution transmission electron microscopy (HRTEM) imaging, temperature-programmed reduction (H2-TPR), and in-depth interpretation of Raman bands led to the conclusion that a high fraction of the Ni and Fe formed the desired Ni3Fe alloy resulting in small and well-defined nanoparticles with 4 nm in size and a dispersion of 24%. For comparison, a monometallic catalyst with similar dispersion using the same preparation method and analysis was prepared. Using a fixed-bed reactor, the Ni3F...

Possible roles of uterine PGRMC1 in the implantation and decidualization

In this study, we have examined the performance of copper nanoparticles deposited on carbon spheres with a mass weigh of 10 wt% (labeled 10Cu-CSs) via photo-electrochemical reduction of carbon dioxide (CO2). The carbon spheres (CSs) were prepared by a chemical vapor deposition method and 10Cu-CSs was made via a homogeneous deposition precipitation method. The materials were characterized by different physico-chemical techniques such as X-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR) and diffuse reflectance (DR) spectroscopy, electrical conductivity and photo-electrochemical studies. The 10Cu-CSs material was studied for the photo-electrochemical reduction of CO2 under visible light illumination. The synthesized material exhibited a single phase monoclinic structure of CuO deposited on CSs as confirmed by XRD, Raman and FTIR spectroscopies results. The semi-conductor property was established by electrical conductivity, and the activation energy obtained was ca. 0.04 eV. The UV–visible absorption spectrum showed a direct band gap transition with gap energy of 1.22 eV. The material synthesized was a cathode semi-conductor with p-type conductivity. The deposition of copper nanoparticles enhanced the CO2 photo-conversion to formic acid under the reaction conditions. In particular, 10Cu-CSs demonstrated gave formic acid, which was at a higher potential than standard redox potentials of copper. Furthermore, the photo-electrochemical characterization showed that the deposition of the copper onto CSs used as electrode effectively generated photo-induced electron/hole pairs under visible light irradiation leading an enhancement of photo-reduction under visible light in a NaHCO3 electrolyte.

Selective catalytic reduction of NO with NH3 over the SAPO-34 supported transition metal nanocatalysts

A series of M/SAPO-34 (M=Cu, Fe, Co, and Mn) nanocatalysts was prepared via homogeneous deposition precipitation (HDP) using urea as the precursor for the precipitating agent, and further characterized by N2 adsorption, TEM, H2-TPR and NH3-TPD. The catalytic activity of these nanocatalysts was evaluated for the selective catalytic reduction (SCR) of NO with NH3 as reductant in the presence of excess oxygen. The highest catalytic activity was obtained for the Cu/SAPO-34 nanocatalyst. The TEM and BET results indicated that M/SAPO-34 nanocatalysts have a well-dispersed state of metal species on support and the loaded metal species presenting in nanoscale caused an increase in external surface area of SAPO-34. According to H2-TPR and NH3-TPD profiles, the catalysts’ behavior for NO conversion depends mainly on the redox properties of the metal species and also acidity of catalysts. The high SCR activity on the Cu/SAPO-34 nanocatalyst is attributed to better low-temperature redox properties of copper species and its high acidity.

Comparative study of ZSM‐5 supported transition metal (Cu, Mn, Co, and Fe) nanocatalysts in the selective catalytic reduction of NO with NH3

H‐ZSM‐5 was modified with transition metals (including Fe, Cu, Mn, and Co) by homogeneous deposition precipitation (HDP) method and tested as catalyst for the selective reduction of NO with ammonia (NH3‐SCR). The selectivity to N2 was higher than 95% in all the nanocatalysts and the NO conversion over nanocatalysts decreased in the following sequence Cu‐ZSM‐5 > Mn‐ZSM‐5 > Co‐ZSM‐5 > Fe‐ZSM‐5 at 200‐300°C. The Cu‐ZSM‐5 catalyst showed the highest catalytic activity, 95% of NO conversion at 300°C, among the catalysts investigated. The nature of the active sites was characterized by BET, TEM, H2‐TPR, and NH3‐TPD. Characterization results revealed that acidity and the redox properties of the catalysts play an important role in achieving high activity for NH3‐SCR reaction. The highest catalytic activity of Cu/ZSM‐5 can be correlated to easy reducibility of Cu species and strong acidic sites created by the Cu species. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1049–1055, 2017

Activity of $\gamma $-Al$_{2}$O$_{3}$-based Mn, Cu, and Co oxide nanocatalysts for selective catalytic reduction of nitric oxide with ammonia

Our studies on the selective catalytic reduction of NO (SCR-deNO) properties of M/$\gamma $-Al$_{2}$O$_{3}$ (M = Mn, Co, Cu) nanocatalysts are presented. All catalysts were prepared by homogeneous deposition precipitation using urea as the precursor for the precipitating agent. The SCR activity followed the order Mn/$\gamma $-Al$_{2}$O$_{3} >$ Cu/$\gamma $-Al$_{2}$O$_{3} >$ Co/$\gamma $-Al$_{2}$O$_{3}$. The nanocatalysts were characterized with respect to their texture (N$_{2}$-BET), particle size (TEM), reducibility (H$_{2}$-TPR), and acidity (NH$_{3}$-TPD). The TEM analysis revealed that the metal species have superior dispersion with less agglomeration and sintering on $\gamma $-Al$_{2}$O$_{3}$ support. The H$_{2}$-TPR results confirmed that the Mn/$\gamma $-Al$_{2}$O$_{3}$ nanocatalyst contains various oxidation states of manganese, which is useful for the catalyst to maintain the DeNO activities. The NH$_{3}$-TPD studies indicated that the addition of transition metal can significantly increase the surface acidity and Mn/$\gamma $-Al$_{2}$O$_{3}$ showed the most adsorbed sites of NH$_{3}$. Characterization results indicated that the acidity and the redox properties of the catalyst play important roles in the final catalytic activity in the SCR-NO process.

Modeling and optimization of NH3-SCR performance of MnOx/γ-alumina nanocatalysts by response surface methodology

To model and optimize the NH3-SCR performance of MnOx/γ-alumina nanocatalysts, the response surface methodology (RSM) based on a central composite design (CCD) was employed. The MnOx/γ-alumina nanocatalysts were prepared by homogeneous deposition precipitation and characterized by XRD, H2-TPR, N2 adsorption and TEM. The effect of process variables, including Mn loading, calcination temperature, concentration of O2, NH3/NO ratio and reaction temperature on NOx conversion and N2 selectivity was studied. Analysis of variance confirmed the accuracy and precision of generating quadratic models. The calcination temperature and reaction temperature had the most pronounced effects on NOx conversion and N2 selectivity, respectively. The maximum NH3-SCR performance (94.6% NOx conversion and 93.7% N2 selectivity) was predicted and experimentally validated at the optimum conditions: Mn loading 6.7wt. %, calcination temperature 507.5°C, concentration of O2 4.5 (vol. %), NH3/NO ratio 0.94 and reaction temperature 269.8°C.

Effect of the preparation method on activity of Cu-ZSM-5 nanocatalyst for the selective reduction of NO by NH3

ABSTRACTThe selective catalytic reduction of NO with ammonia (NH3–SCR) was studied over Cu-ZSM-5 nanocatalysts which were prepared by several methods, including conventional ion-exchange (IE), conventional impregnation (IM), ultrasound-enhanced impregnation (UIM), and conventional deposition–precipitation (DP) using NaOH and homogeneous deposition–precipitation (HDP) using urea. The nanocatalysts were subsequently characterized by Fourier transform infrared spectroscopy, temperature-programmed reduction with hydrogen (H2-TPR), ammonia temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscope, and Brunauer–Emmett–Teller. The catalytic activity of the Cu-ZSM-5 nanocatalysts for NO removal decreased in the following order: Cu-ZSM-5 (HDP) > Cu-ZSM-5 (UIM) > Cu-ZSM-5 (IM) > Cu-ZSM-5 (IE) > Cu-ZSM-5 (DP). The effect of various preparation methods for Cu-ZSM-5 on the activity of NO conversion was compared and catalytic experiments revealed a strong correlation between the acid sites’ strength and easily reducible isolated Cu2+ with NO conversion. Catalyst (HDP) (which showed excellent deNO activity) mainly contains easy reducibility of isolated Cu2+ ions, more strong acid sites, and higher specific surface area when compared with other catalysts.

Gold Nanoparticles Grafted Mesoporous Silica: A Highly Efficient and Recyclable Heterogeneous Catalyst for Reduction of 4-Nitrophenol

Synthesis of gold nanoparticles dispersed uniformly on mesoporous silica (mAu/SiO2) by homogeneous deposition–precipitation (HDP) method is used as an effective catalyst for reduction of 4-nitrophenol to 4-aminophenol. Silica provides support and surface area to increase the catalytic activity of gold. X-ray photon spectroscopy revealed binding energy of Au 4[Formula: see text] ([Formula: see text]84.0[Formula: see text]eV) and Au 4[Formula: see text] ([Formula: see text]87.7[Formula: see text]eV) which support the formation of Au0 on SiO2 surface. Au/SiO2 showed Langmuir type-IV isotherms which are the characteristic features of mesoporous materials furthermore, pore size decreases with incorporation of Au NP’s on SiO2 surface. The enhancement is due to the strong interaction of Au0 with silica support. The catalytic conversion was studied by UV-Visible spectroscopy and high performance liquid chromatography (HPLC) quantification method, which shows conversion of nitro group into amino group. In addition, the catalyst was easily separated and reused. The reusability of the catalyst exhibited better reduction of the 4-nitrophenol to 4-aminophenol even after 10 consecutive cycles. In comparison to trisodium citrate capped pure gold nanoparticles mAu/SiO2 catalysts showed very good catalytic activity toward nitrophenol reduction. Here we conclude that embedment of metal catalysts like Au into high surface area support like silica is a positive step toward development of novel heterogeneous catalysts.