Promotional Effect of Gold on the WGS Activity of Alumina-Supported Copper-Manganese Mixed Oxides

The water-gas shift (WGS) reaction is a well-known industrial process used for the production of hydrogen. During the last few decades, it has attracted renewed attention due to the need for high-purity hydrogen for fuel-cell processing systems. The aim of the present study was to develop a cost-effective and catalytically efficient formulation that combined the advantageous properties of transition metal oxides and gold nanoparticles. Alumina-supported copper- manganese mixed oxides were prepared by wet impregnation. The deposition-precipitation method was used for the synthesis of gold catalysts. The effect of the Cu:Mn molar ratio and the role of Au addition on the WGS reaction’s performance was evaluated. Considerable emphasis was put on the characterization of the as-prepared and WGS-tested samples by means of a number of physicochemical methods (X-ray powder diffraction, high-resolution transmission electron microscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and temperature-programmed reduction) in order to explain the relationship between the structure and the reductive and WGS behavior. Catalytic tests revealed the promotional effect of gold addition. The best performance of the gold-promoted sample with a higher Cu content, i.e., a Cu:Mn molar ratio of 2:1 might be related to the beneficial role of Au on the spinel decomposition and the highly dispersed copper particle formation during the reaction, thus, ensuring the presence of two highly dispersed active metallic phases. High-surface-area alumina that was modified with a surface fraction of Cu–Mn mixed oxides favored the stabilization of finely dispersed gold particles. These new catalytic systems are very promising for practical applications due to their economic viability because the composition mainly includes alumina (80%).

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A highly efficient and stable Ni/SBA-15 catalyst for hydrogen production by ethanol steam reforming

Progress in Reaction Kinetics and Mechanism ◽

10.1177/1468678319891842 ◽

2020 ◽

Vol 45 ◽

pp. 146867831989184

Author(s):

Xia An ◽

Jia Ren ◽

Weitao Hu ◽

Xu Wu ◽

Xianmei Xie

Keyword(s):

Steam Reforming ◽

Photoelectron Spectroscopy ◽

Nickel Nitrate ◽

Molar Ratio ◽

Linear Regression Method ◽

Impregnation Method ◽

X Ray ◽

Nickel Sulfamate ◽

Steam Reforming Of Ethanol ◽

Production Of Hydrogen

The production of hydrogen by steam reforming of ethanol was carried out on SBA-15-supported nano NiO catalyst synthesized by the equivalent-volume impregnation method with two different Ni sources (nickel nitrate and nickel sulfamate). The catalyst was characterized by N2 adsorption–desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy to examine the physical and chemical properties. The activity tests were performed with the steam, with water/ethanol molar ratio ranging from 2:1 to 15:1, the N2 flow rate from 20 to 120 mL min−1 to determine the space-time, and the temperature range from 623 to 923 K on the two different Ni source catalysts. A favorable operating condition was established at 823 K using water/ethanol = 6 molar ratio and carrier gas (N2) flow of more than 50 mL min−1 for nickel nitrate source, but for nickel sulfamate source, the optimum temperature changed to 773 K and other conditions were the same as for the nickel nitrate source. After eliminating the influence of internal and external diffusion factors, an empirical power-law kinetic rate equation was derived from the experimental data. The non-linear regression method was used to estimate the kinetic parameter. The activation energy of the catalyst was then calculated, and the supported nickel nitrate and nickel sulfamate catalysts were 25.345 and 41.449 kJ mol−1, respectively, which was in agreement with the experimental and model-predicted results.

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Zn-Al Mixed Oxides Decorated with Potassium as Catalysts for HT-WGS: Preparation and Properties

Catalysts ◽

10.3390/catal10091094 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1094 ◽

Cited By ~ 1

Author(s):

Katarzyna Antoniak-Jurak ◽

Paweł Kowalik ◽

Kamila Michalska ◽

Wiesław Próchniak ◽

Robert Bicki

Keyword(s):

Photoelectron Spectroscopy ◽

Mixed Oxides ◽

Catalyst Activity ◽

Molar Ratio ◽

X Ray ◽

Molar Ratios ◽

Mixed Oxide Catalysts ◽

Wgs Reaction ◽

Temperature Programmed ◽

Co Precipitation

A set of ex-ZnAl-LDHs catalysts with a molar ratio of Zn/Al in the range of 0.3–1.0 was prepared using co-precipitation and thermal treatment. The samples were characterized using various methods, including X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy FT-IR, N2 adsorption, Temperature-programmed desorption of CO2 (TPD-CO2) as well as Scanning electron microscopy (SEM-EDS). Catalyst activity and long-term stability measurements were carried out in a high-temperature water–gas shift (HT-WGS) reaction. Mixed oxide catalysts with various Zn/Al molar ratios decorated with potassium showed high activity in the HT-WGS reaction within the temperature range of 330–400 °C. The highest activity was found for the Zn/Al molar ratio of 0.5 corresponding to spinel stoichiometry. However, the catalyst with a stoichiometric spinel molar ratio of Zn/Al (ZnAl_0.5_K) revealed a higher tendency for surface migration and/or vaporization of potassium during overheating at 450 °C. The correlation of the activity results and TPD-CO2 data show that medium basic sites enhance the progress of the HT-WGS reaction.

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Selective Hydrogenation of Benzene to Cyclohexene over Ru-Zn Catalysts: Investigations on the Effect of Zn Content and ZrO2 as the Support and Dispersant

Catalysts ◽

10.3390/catal8110513 ◽

2018 ◽

Vol 8 (11) ◽

pp. 513 ◽

Cited By ~ 2

Author(s):

Haijie Sun ◽

Zhihao Chen ◽

Lingxia Chen ◽

Huiji Li ◽

Zhikun Peng ◽

...

Keyword(s):

Catalytic Activity ◽

Selective Hydrogenation ◽

Photoelectron Spectroscopy ◽

Supported Catalyst ◽

Precipitation Method ◽

Molar Ratio ◽

Impregnation Method ◽

X Ray ◽

Zn Content ◽

Co Precipitation

m-ZrO2 (monoclinic phase) supported Ru-Zn catalysts and unsupported Ru-Zn catalysts were synthesized via the impregnation method and co-precipitation method, respectively. The catalytic activity and selectivity were evaluated for selective hydrogenation of benzene towards cyclohexene formation. Catalyst samples before and after catalytic experiments were thoroughly characterized via X-ray diffraction (XRD), X-ray Fluorescence (XRF), transmission electron microscopy (TEM), N2-sorption, X-ray photoelectron spectroscopy (XPS), H2-temperature programmed reduction (H2-TPR), and a contact angle meter. It was found that Zn mainly existed as ZnO, and its content was increased in Ru-Zn/m-ZrO2 by enhancing the Zn content during the preparation procedure. This results in the amount of formed (Zn(OH)2)3(ZnSO4)(H2O)3 increasing and the catalyst becoming more hydrophilic. Therefore, Ru-Zn/m-ZrO2 with adsorbed benzene would easily move from the oil phase into the aqueous phase, in which the synthesis of cyclohexene took place. The generated cyclohexene then went back into the oil phase, and the further hydrogenation of cyclohexene would be retarded because of the high hydrophilicity of Ru-Zn/m-ZrO2. Hence, the selectivity towards cyclohexene formation over Ru-Zn/m-ZrO2 improved by increasing the Zn content. When the theoretical molar ratio of Zn to Ru was 0.60, the highest cyclohexene yield of 60.9% was obtained over Ru-Zn (0.60)/m-ZrO2. On the other hand, when m-ZrO2 was utilized as the dispersant (i.e., employed as an additive during the reaction), the catalytic activity and selectivity towards cyclohexene synthesis over the unsupported Ru-Zn catalyst was lower than that achieved over the Ru-Zn catalyst with m-ZrO2 as the support. This is mainly because the supported catalyst sample demonstrated superior dispersion of Ru, higher content of (Zn(OH)2)3(ZnSO4)(H2O)3, and a stronger electronic effect between Ru and ZrO2. The Ru-Zn(0.60)/m-ZrO2 was reused 17 times without any regeneration, and no loss of catalytic activity and selectivity towards cyclohexene formation was observed.

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Palladium-Incorporated α-MoC Mesoporous Composites for Enhanced Direct Hydrodeoxygenation of Anisole

Catalysts ◽

10.3390/catal11030370 ◽

2021 ◽

Vol 11 (3) ◽

pp. 370

Author(s):

Yue Yang ◽

Xiaochen Liu ◽

Yuanjie Xu ◽

Xing Gao ◽

Yihu Dai ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Rational Design ◽

Bond Activation ◽

Molar Ratio ◽

X Ray ◽

Transmission Electron ◽

Model Molecule ◽

Highly Dispersed ◽

Mesoporous Composites ◽

Temperature Programmed

Hydrodeoxygenation (HDO) is one of the promising catalytic routes for converting biomass derived molecules to high value products. A key step of HDO is the cleavage of an aromatic C–O bond to accomplish the deoxygenation step, however, which is energetically unfavorable. Herein, we report a series of palladium (Pd)-incorporated α-phase of molybdenum carbide (α-MoC) mesoporous composites for enhanced HDO activity of a biomass model molecule, anisole. The catalysts, x%Pd/α-MoC (x% is the molar ratio of Pd/Mo), were investigated by X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD), Brunauer–Emmett–Teller (BET), Raman, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques. Pd is highly dispersed on α-MoC when x% ≤ 1%, but aggregate to form nanoparticles when x% = 5%. The x%Pd/α-MoC catalysts (x% ≤ 1%) show enhanced HDO activity in terms of turnover frequency (TOF) and apparent activation energy barrier (Ea) compared with α-MoC and β-Mo2C catalysts. The TOF of 1%Pd/α-MoC catalyst at 160 °C is 0.115 h−1 and the Ea is 48.2 kJ/mol. Moreover, the direct cleavage of aromatic C–O bond is preferred on 1%Pd/α-MoC catalyst. The enhanced HDO activity is attributed to superior H2 dissociation ability by the highly dispersed Pd sites on carbide. This work brings new insights for rational design of the catalyst for selective C–O bond activation.

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Effect of Aging Methods on CuZnAl Catalysts for Methyl Acetate Hydrogenation

Australian Journal of Chemistry ◽

10.1071/ch18534 ◽

2019 ◽

Vol 72 (6) ◽

pp. 417

Author(s):

Changna Gan ◽

Yunhao Wang ◽

Chenliang Ye ◽

Cuili Guo

Keyword(s):

Photoelectron Spectroscopy ◽

Inductively Coupled Plasma ◽

Methyl Acetate ◽

Copper Particle ◽

Atomic Emission ◽

Catalytic Performance ◽

Precipitation Method ◽

Molar Ratio ◽

X Ray ◽

Temperature Programmed

A series of CuZnAl catalysts derived from layered double hydroxide precursors with different Cu/Zn molar ratios were synthesised by a co-precipitation method for methyl acetate hydrogenation. The best catalytic performance was obtained when the Cu/Zn molar ratio reached 0.25:1. After fixing the Cu/Zn molar ratio at 0.25:1, the effect of aging methods, including ultrasound, high shear mixer stirring, and magnetic stirring, were investigated, which showed that 0.25CuZnAl-u and 0.25CuZnAl-h exhibited a higher conversion and selectivity than that of 0.25CuZnAl-m, especially under low reaction temperatures. The physicochemical properties of the CuZnAl catalysts were characterised by X-ray diffraction, inductively coupled plasma–atomic emission spectroscopy, N2 physisorption, N2O chemisorption, transmission electron microscopy, H2-temperature-programmed reduction, X-ray photoelectron spectroscopy, and H2-temperature-programmed desorption. It was found that compared with 0.25CuZnAl-m, 0.25CuZnAl-u and 0.25CuZnAl-h possessed a stronger interaction between Cu and the support, smaller copper particle size, and higher copper dispersion, which improved the catalytic performance.

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Effect of Ti on dibenzothiophene hydrodesulfurization performance over bulk Ni2P

Progress in Reaction Kinetics and Mechanism ◽

10.1177/1468678319825693 ◽

2019 ◽

Vol 44 (1) ◽

pp. 45-54

Author(s):

Chunbao Han ◽

Hua Song ◽

Nan Jiang ◽

Yanguang Chen ◽

Feng Li ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Molar Fraction ◽

P System ◽

Temperature Programmed Reduction ◽

X Ray Diffraction ◽

X Ray ◽

Highly Dispersed ◽

Temperature Programmed ◽

Hydrodesulfurization Activity

A series of Ti-incorporated bulk Ni2P catalysts was prepared by means of temperature-programmed reduction, and the role of metallic Ti on the structure and catalytic activity of the Ni2P catalysts was studied. For this purpose, bulk Ni2P catalysts with metal Ti contents of 0.005 wt%, 0.01 wt%, and 0.02 wt% were synthesized. X-ray diffraction, CO uptake, Brunauer–Emmett–Teller measurements, and X-ray photoelectron spectroscopy were utilized to characterize the catalysts. Addition of titanium could increase the surface area and promote the formation of small, highly dispersed Ni2P particles. The Ti0.02-Ni2P system with a Ti molar fraction of 0.02 showed the highest hydrodesulfurization activity of 99.6%, which was an increase of 44% compared with that found for the bulk Ni2P.

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Zn Promoted Mg-Al Mixed Oxides-Supported Gold Nanoclusters for Direct Oxidative Esterification of Aldehyde to Ester

International Journal of Molecular Sciences ◽

10.3390/ijms22168668 ◽

2021 ◽

Vol 22 (16) ◽

pp. 8668

Author(s):

Jie Li ◽

Shiyi Wang ◽

Huayin Li ◽

Yuan Tan ◽

Yunjie Ding

Keyword(s):

Photoelectron Spectroscopy ◽

Mixed Oxides ◽

Physical Adsorption ◽

Gold Nanoclusters ◽

Precipitation Method ◽

Esterification Reaction ◽

X Ray ◽

Oxidative Esterification ◽

Molar Ratios ◽

Supported Gold

The synthesis of ester compounds is one of the most important chemical processes. In this work, Zn-Mg-Al mixed oxides with different Zn2+/Mg2+ molar ratios were prepared via co-precipitation method and supported gold nanoclusters to study the direct oxidative esterification of aldehyde and alcohol in the presence of molecular oxygen. Various characterization techniques such as N2-physical adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and CO2 temperature programmed desorption (TPD) were utilized to analyze the structural and electronic properties. Based on the results, the presence of small amounts of Zn2+ ions (~5 wt.%) provoked a remarkable modification of the binary Mg-Al system, which enhanced the interaction between gold with the support and reduced the particle size of gold. For oxidative esterification reaction, the Au25/Zn0.05MgAl-400 catalyst showed the best performance, with the highest turnover frequency (TOF) of 1933 h−1. The active center was believed to be located at the interface between metallic gold with the support, where basic sites contribute a lot to transformation of the substrate.

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Photocatalytic Reduction of CO2 to Methanol Using a Copper-Zirconia Imidazolate Framework

Catalysts ◽

10.3390/catal11030346 ◽

2021 ◽

Vol 11 (3) ◽

pp. 346

Author(s):

Sonam Goyal ◽

Maizatul Shima Shaharun ◽

Ganaga Suriya Jayabal ◽

Chong Fai Kait ◽

Bawadi Abdullah ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Catalyst Support ◽

Oxidation Potential ◽

Molar Ratio ◽

X Ray Diffraction ◽

X Ray ◽

Molar Ratios ◽

Optimum Parameters ◽

Reduction Of Co2 ◽

Enhanced Yield

A set of novel photocatalysts, i.e., copper-zirconia imidazolate (CuZrIm) frameworks, were synthesized using different zirconia molar ratios (i.e., 0.5, 1, and 1.5 mmol). The photoreduction process of CO2 to methanol in a continuous-flow stirred photoreactor at pressure and temperature of 1 atm and 25 °C, respectively, was studied. The physicochemical properties of the synthesized catalysts were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The highest methanol activity of 818.59 µmol/L.g was recorded when the CuZrIm1 catalyst with Cu/Zr/Im/NH4OH molar ratio of 2:1:4:2 (mmol/mmol/mmol/M) was employed. The enhanced yield is attributed to the presence of Cu2+ oxidation state and the uniformly dispersed active metals. The response surface methodology (RSM) was used to optimize the reaction parameters. The predicted results agreed well with the experimental ones with the correlation coefficient (R2) of 0.99. The optimization results showed that the highest methanol activity of 1054 µmol/L.g was recorded when the optimum parameters were employed, i.e., stirring rate (540 rpm), intensity of light (275 W/m2) and photocatalyst loading (1.3 g/L). The redox potential value for the CuZrIm1 shows that the reduction potential is −1.70 V and the oxidation potential is +1.28 V for the photoreduction of CO2 to methanol. The current work has established the potential utilization of the imidazolate framework as catalyst support for the photoreduction of CO2 to methanol.

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Improved Water–Gas Shift Performance of Au/NiAl LDHs Nanostructured Catalysts via CeO2 Addition

Nanomaterials ◽

10.3390/nano11020366 ◽

2021 ◽

Vol 11 (2) ◽

pp. 366

Author(s):

Margarita Gabrovska ◽

Ivan Ivanov ◽

Dimitrinka Nikolova ◽

Jugoslav Krstić ◽

Anna Maria Venezia ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Nanostructured Catalysts ◽

Water Gas Shift ◽

Precipitation Method ◽

Conversion Degree ◽

Pure Hydrogen ◽

Medium Temperature ◽

X Ray ◽

Supported Gold ◽

Water Gas

Supported gold on co-precipitated nanosized NiAl layered double hydroxides (LDHs) was studied as an effective catalyst for medium-temperature water–gas shift (WGS) reaction, an industrial catalytic process traditionally applied for the reduction in the amount of CO in the synthesis gas and production of pure hydrogen. The motivation of the present study was to improve the performance of the Au/NiAl catalyst via modification by CeO2. An innovative approach for the direct deposition of ceria (1, 3 or 5 wt.%) on NiAl-LDH, based on the precipitation of Ce3+ ions with 1M NaOH, was developed. The proposed method allows us to obtain the CeO2 phase and to preserve the NiAl layered structure by avoiding the calcination treatment. The synthesis of Au-containing samples was performed through the deposition–precipitation method. The as-prepared and WGS-tested samples were characterized by X-ray powder diffraction, N2-physisorption and X-ray photoelectron spectroscopy in order to clarify the effects of Au and CeO2 loading on the structure, phase composition, textural and electronic properties and activity of the catalysts. The reduction behavior of the studied samples was evaluated by temperature-programmed reduction. The WGS performance of Au/NiAl catalysts was significantly affected by the addition of CeO2. A favorable role of ceria was revealed by comparison of CO conversion degree at 220 °C reached by 3 wt.% CeO2-modified and ceria-free Au/NiAl samples (98.8 and 83.4%, respectively). It can be stated that tuning the properties of Au/NiAl LDH via CeO2 addition offers catalysts with possibilities for practical application owing to innovative synthesis and improved WGS performance.

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Low-temperature route to nanoscale P3N5 hollow spheres

Journal of Materials Research ◽

10.1557/jmr.2003.0330 ◽

2003 ◽

Vol 18 (10) ◽

pp. 2359-2363 ◽

Cited By ~ 23

Author(s):

Hongzhou Gu ◽

Yunle Gu ◽

Zhefeng Li ◽

Yongcheng Ying ◽

Yitai Qian

Keyword(s):

Photoelectron Spectroscopy ◽

Hollow Spheres ◽

Molar Ratio ◽

Visible Absorption ◽

X Ray ◽

Transmission Electron ◽

Influence Of Temperature On ◽

Wide Gap ◽

20 Nm ◽

High Degree

Nanoscale hollow spheres of amorphous phosphorus nitride (P3N5) were synthesized by reacting PCl3 with NaN3 at 150–250 °C. Transmission electron microscope images show that the hollow spheres have a diameter of 150–350 nm, and the thickness of the shell is 20 nm. A very small amount of curly films were also found in the sample prepared at 150 °C. The infrared spectrum indicates a high degree of purity. X-ray photoelectron spectroscopy indicates the presence of P and N, with a molar ratio of 1:1.62 for P:N. Ultraviolet-visible absorption spectroscopy shows an absorption band at 265–315 nm. Under photoluminescent excitation at 230 nm, the P3N5 emits ultraviolet light at 305 nm. With a band gap of 4.28 eV, the products may be a wide gap semiconductor. A possible mechanism and the influence of temperature on the formation of the hollow spheres are also discussed.

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