scholarly journals Evolution of the pore and framework structure of NaY zeolite during alkali treatment and its effect on methanol oxidative carbonylation over a CuY catalyst

2020 ◽  
Vol 44 (11-12) ◽  
pp. 710-720
Author(s):  
Lifei Yan ◽  
Tingjun Fu ◽  
Jiajun Wang ◽  
Nilesh Narkhede ◽  
Zhong Li
Keyword(s):  
Catalytic Activity ◽  
Surface Area ◽  
Photoelectron Spectroscopy ◽  
Dimethyl Carbonate ◽  
Alkali Treatment ◽  
Oxidative Carbonylation ◽  
Framework Structure ◽  
Y Zeolite ◽  
Cage Structure ◽  
X Ray

Alkali treatment is widely used on aluminosilicate zeolites with high Si/Al ratios in order to fabricate mesopores in the framework. However, for zeolites with low Si/Al ratios, the effect of alkali treatment on the pore and framework structure needed further study. In this work, Y zeolite is treated with NaOH solutions of different concentrations and is used as the support for Cu-based catalysts for oxidative carbonylation of methanol to dimethyl carbonate. The physicochemical properties of the supports and corresponding catalysts are characterized by N2 adsorption–desorption, X-ray diffraction, X-ray fluorescence, transmission electron microscopy, inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, and H2-temperature-programmed reduction analyses. The results show that no obvious mesopores are formed under alkali treatment, even at high NaOH concentration. However, amorphous species present in the micropores of Y zeolite are removed, which increases the micropore surface area as well as the crystallinity. Simultaneously, the cage structure is partially destroyed, which also leads to a slight increase of the pore volume and surface area. The altered micropore structure eventually increases the content and accessibility of the exchanged Cu species, which is beneficial to the catalytic activity. When the concentration of NaOH is 0.6 M, the space time yield of dimethyl carbonate for the corresponding catalyst was 151.4 mg g−1 h−1 which is 3.3-fold higher than that of the untreated-Y-zeolite-supported Cu catalyst. However, further increasing the alkali treatment strength can seriously destroy the basic aluminosilicate structure of the Y zeolite and decrease its intrinsic ion-exchange capacity. This results in the formation of agglomerated CuO on the catalyst surface, which was not conducive to catalytic activity.

scholarly journals Catalytic activity of nanostructured Au: Scale effects versus bimetallic/bifunctional effects in low-temperature CO oxidation on nanoporous Au

2013 ◽  
Vol 4 ◽  
pp. 111-128 ◽  
Author(s):  
Lu-Cun Wang ◽  
Yi Zhong ◽  
Haijun Jin ◽  
Daniel Widmann ◽  
Jörg Weissmüller ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Low Temperature ◽  
Co Oxidation ◽  
Surface Area ◽  
Photoelectron Spectroscopy ◽  
Scale Effects ◽  
Structural Parameters ◽  
Kinetic Measurements ◽  
X Ray ◽  
Low Temperature Co Oxidation

The catalytic properties of nanostructured Au and their physical origin were investigated by using the low-temperature CO oxidation as a test reaction. In order to distinguish between structural effects (structure–activity correlations) and bimetallic/bifunctional effects, unsupported nanoporous gold (NPG) samples prepared from different Au alloys (AuAg, AuCu) by selective leaching of a less noble metal (Ag, Cu) were employed, whose structure (surface area, ligament size) as well as their residual amount of the second metal were systematically varied by applying different potentials for dealloying. The structural and chemical properties before and after 1000 min reaction were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The catalytic behavior was evaluated by kinetic measurements in a conventional microreactor and by dynamic measurements in a temporal analysis of products (TAP) reactor. The data reveal a clear influence of the surface contents of residual Ag and Cu species on both O2 activation and catalytic activity, while correlations between activity and structural parameters such as surface area or ligament/crystallite size are less evident. Consequences for the mechanistic understanding and the role of the nanostructure in these NPG catalysts are discussed.

scholarly journals Eco-Friendly Cavity-Containing Iron Oxides Prepared by Mild Routes as Very Efficient Catalysts for the Total Oxidation of VOCs

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1387 ◽  
Author(s):  
Rut Sanchis ◽  
Daniel Alonso-Domínguez ◽  
Ana Dejoz ◽  
María Pico ◽  
Inmaculada Álvarez-Serrano ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Surface Area ◽  
Iron Oxides ◽  
Photoelectron Spectroscopy ◽  
Specific Activity ◽  
High Surface ◽  
Superior Performance ◽  
Porous Iron ◽  
Total Oxidation ◽  
X Ray

Iron oxides (FeOx) are non-toxic, non-expensive and environmentally friendly compounds, which makes them good candidates for many industrial applications, among them catalysis. In the present article five catalysts based on FeOx were synthesized by mild routes: hydrothermal in subcritical and supercritical conditions (Fe-HT, Few200, Few450) and solvothermal (Fe-ST1 and Fe-ST2). The catalytic activity of these catalysts was studied for the total oxidation of toluene using very demanding conditions with high space velocities and including water and CO2 in the feed. The samples were characterized by X-ray diffraction (XRD), scanning and high-resolution transmission electron microscopy (SEM and HRTEM), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption-desorption isotherms. It was observed that the most active catalyst was a cavity-containing porous sample prepared by a solvothermal method with a relatively high surface area (55 m2 g−1) and constituted by flower-like aggregates with open cavities at the catalyst surface. This catalyst displayed superior performance (100% of toluene conversion at 325 °C using highly demanding conditions) and this performance can be maintained for several catalytic cycles. Interestingly, the porous iron oxides present not only a higher catalytic activity than the non-porous but also a higher specific activity per surface area. The high activity of this catalyst has been related to the possible synergistic effect of compositional, structural and microstructural features emphasizing the role of the surface area, the crystalline phase present, and the properties of the surface.

Property of Cu2O-CuO/ZSM-5 nanocomposite and degradation process of azo dye AO7 without sacrificial agent (H2O2)

2016 ◽  
Vol 73 (11) ◽  
pp. 2747-2753 ◽  
Author(s):  
Wusong Kong ◽  
Hongxia Qu ◽  
Peng Chen ◽  
Weihua Ma ◽  
Huifang Xie
Keyword(s):  
Catalytic Activity ◽  
Aqueous Solutions ◽  
Photoelectron Spectroscopy ◽  
Oxygen Demand ◽  
Operating Conditions ◽  
Surface Element ◽  
Impregnation Method ◽  
X Ray ◽  
Initial Ph ◽  
Sacrificial Agent

In this study, Cu2O-CuO/ZSM-5 nanocomposite was synthesized by the impregnation method, and its catalytic performance for the destruction of AO7 in aqueous solutions was investigated. The morphology, structure and surface element valence state of Cu2O-CuO/ZSM-5 were characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The operating conditions on the degradation of AO7 by Cu2O-CuO/ZSM-5, such as initial pH values, concentration of AO7 and catalyst dosage were investigated and optimized. The results showed that the sample had good catalytic activity for destruction of AO7 in the absence of a sacrificial agent (e.g. H2O2): it could degrade 91% AO7 in 140 min at 25 °C and was not restricted by the initial pH of the AO7 aqueous solutions. Cu2O-CuO/ZSM-5 exhibited stable catalytic activity with little loss after three successive runs. The total organic carbon and chemical oxygen demand removal efficiencies increased rapidly to 69.36% and 67.3% after 120 min of treatment by Cu2O-CuO/ZSM-5, respectively.

scholarly journals Organosilane-functionalization of nanostructured indium tin oxide films

2016 ◽  
Vol 6 (6) ◽  
pp. 20160056 ◽  
Author(s):  
R. Pruna ◽  
F. Palacio ◽  
M. Martínez ◽  
O. Blázquez ◽  
S. Hernández ◽  
...  
Keyword(s):  
Surface Area ◽  
Indium Tin Oxide ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Annealing Treatment ◽  
Electrochemical Analysis ◽  
Cyclic Voltammograms ◽  
X Ray ◽  
Chip Technology ◽  
Significant Difference

Fabrication and organosilane-functionalization and characterization of nanostructured ITO electrodes are reported. Nanostructured ITO electrodes were obtained by electron beam evaporation, and a subsequent annealing treatment was selectively performed to modify their crystalline state. An increase in geometrical surface area in comparison with thin-film electrodes area was observed by atomic force microscopy, implying higher electroactive surface area for nanostructured ITO electrodes and thus higher detection levels. To investigate the increase in detectability, chemical organosilane-functionalization of nanostructured ITO electrodes was performed. The formation of 3-glycidoxypropyltrimethoxysilane (GOPTS) layers was detected by X-ray photoelectron spectroscopy. As an indirect method to confirm the presence of organosilane molecules on the ITO substrates, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were also carried out. Cyclic voltammograms of functionalized ITO electrodes presented lower reduction-oxidation peak currents compared with non-functionalized ITO electrodes. These results demonstrate the presence of the epoxysilane coating on the ITO surface. EIS showed that organosilane-functionalized electrodes present higher polarization resistance, acting as an electronic barrier for the electron transfer between the conductive solution and the ITO electrode. The results of these electrochemical measurements, together with the significant difference in the X-ray spectra between bare ITO and organosilane-functionalized ITO substrates, may point to a new exploitable oxide-based nanostructured material for biosensing applications. As a first step towards sensing, rapid functionalization of such substrates and their application to electrochemical analysis is tested in this work. Interestingly, oxide-based materials are highly integrable with the silicon chip technology, which would permit the easy adaptation of such sensors into lab-on-a-chip configurations, providing benefits such as reduced size and weight to facilitate on-chip integration, and leading to low-cost mass production of microanalysis systems.

scholarly journals Amino-Modified Silica as Effective Support of the Palladium Catalyst for 4-Nitroaniline Hydrogenation

Catalysts ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 375
Author(s):  
Adele R. Latypova ◽  
Maxim D. Lebedev ◽  
Evgeniy V. Rumyantsev ◽  
Dmitry V. Filippov ◽  
Olga V. Lefedova ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
Electron Donor ◽  
Photoelectron Spectroscopy ◽  
Functionalized Silica ◽  
Amino Groups ◽  
Modified Silica ◽  
Pulse Technique ◽  
X Ray ◽  
Transmission Electron

The article describes the synthesis of aminoorgano-functionalized silica as a prospective material for catalysis application. The amino groups have electron donor properties which are valuable for the metal chemical state of palladium. Therefore, the presence of electron donor groups is important for increasing catalysts’ stability. The research is devoted to the investigation of silica amino-modified support influence on the activity and stability of palladium species in 4-nitroaniline hydrogenation process. A series of catalysts with different supports such as SiO2, SiO2-C3H6-NH2 (amino-functionalized silica), γ-Al2O3 and activated carbon were studied. The catalytic activity was studied in the hydrogenation of 4-nitroaniline to 1,4-phenylenediamine. The catalysts were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and chemisorption of hydrogen by the pulse technique. The 5 wt.% Pd/SiO2-C3H6-NH2 catalyst exhibited the highest catalytic activity for 4-nitroaniline hydrogenation with 100% conversion and 99% selectivity with respect to 1,4-phenylenediamine.

scholarly journals Aerobic Oxidation of 5-Hydroxymethylfurfural over Ag Nanoparticle Catalysts Stabilized by Polyvinylpyrrolidone with Different Molecular Weights

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1624
Author(s):  
Haian Xia ◽  
Jiahuan An ◽  
Weizi Zhang
Keyword(s):  
Catalytic Activity ◽  
Photoelectron Spectroscopy ◽  
Catalytic Properties ◽  
Aerobic Oxidation ◽  
Ag Nps ◽  
Oxidation Activity ◽  
X Ray ◽  
Remarkable Effect ◽  
Molecular Weights ◽  
Metal Support Interaction

The metal–support interaction (MSI) has a remarkable effect on the catalytic properties, but how to precisely modulate its degree remains a huge challenge. Herein, polyvinylpyrrolidone (PVP) with three different molecular weights (MWs) (24, 58, and 130 kDa) was used as a capping agent to fabricate Ag nanoparticles (NPs) supported on ZrO2. The physiochemical properties of the catalysts were characterized by X-ray diffraction (XRD), Transmission Electron Microscope (TEM), X-ray Photoelectron Spectroscopy (XPS), and Fourier transform infrared (FT-IR) techniques. The impacts of MSI on the catalytic activity and reaction kinetics for aerobic oxidation of 5-hydroxymethylfurfural (HMF) were investigated. The results showed that the introduction of PVP with various MWs could efficiently tailor the interfacial interactions and charge transfers (CT) among PVP, the support, and Ag NPs, thereby affecting the oxidation activity of HMF. The turnover number (TON) for HMF oxidation decreases in the order of unsupported colloidal Ag clusters > Ag/ZrO2 (58,000) > Ag/ZrO2 (130,000) > Ag/ZrO2 (24,000) > Ag/ZrO2. The reason for this large difference in the catalytic activity for HMF oxidation is that various MWs of PVP result in a change of MSI, thereby facilitating CT from PVP to Ag metal sites. This study offers a new strategy for modulating MSI by varying the MW of capping agents, thereby tuning the catalytic properties in the oxidation of HMF.

Carbon nanotube-supported Cu-based catalysts for oxidative carbonylation of methanol to methyl carbonate: effect of nanotube pore size

2020 ◽  
Vol 10 (8) ◽  
pp. 2615-2626 ◽  
Author(s):  
Dan Zhao ◽  
Guoqiang Zhang ◽  
Lifei Yan ◽  
Lingqi Kong ◽  
Huayan Zheng ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Carbon Nanotube ◽  
Pore Size ◽  
Dimethyl Carbonate ◽  
Oxidative Carbonylation ◽  
Inner Diameter ◽  
Methyl Carbonate

The inner diameter of CNTs significantly affected the location, dispersion, autoreduction and stability of Cu species and thus the catalytic activity and stability for oxidative carbonylation of methanol to dimethyl carbonate.

scholarly journals Ambient Temperature CO Oxidation Using Palladium–Platinum Bimetallic Catalysts Supported on Tin Oxide/Alumina

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1223
Author(s):  
James K. Aldridge ◽  
Louise R. Smith ◽  
David J. Morgan ◽  
Albert F. Carley ◽  
Mandy Humphreys ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Ambient Temperature ◽  
Co Oxidation ◽  
Tin Oxide ◽  
Photoelectron Spectroscopy ◽  
Bimetallic Catalysts ◽  
Moisture Resistance ◽  
X Ray ◽  
Sodium Stannate ◽  
Palladium Platinum

A series of Pt-based catalysts were synthesised and investigated for ambient temperature CO oxidation with the aim to increase catalytic activity and improve moisture resistance through support modification. Initially, bimetallic PtPd catalysts supported on alumina were found to exhibit superior catalytic activity compared with their monometallic counterparts for the reaction. Following an investigation into the effect of Pt/Pd ratio, a composition of 0.1% Pt/0.4% Pd was selected for further studies. Following this, SnO2/Al2O3 supports were synthesised from a variety of tin oxide sources. Catalytic activity was improved using sodium stannate and tin oxalate precursors compared with a traditional tin oxide slurry. Catalytic activity versus tin concentration was found to vary significantly across the three precursors, which was subsequently investigated by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX).

scholarly journals A modified ionic liquid clay to remove heavy metals from water: investigating its catalytic activity

2019 ◽  
Vol 17 (4) ◽  
pp. 2043-2058
Author(s):  
S. Kakaei ◽  
E. S. Khameneh ◽  
M. H. Hosseini ◽  
M. M. Moharreri
Keyword(s):  
Heavy Metal ◽  
Catalytic Activity ◽  
Photoelectron Spectroscopy ◽  
Metal Ion ◽  
Kinetic Studies ◽  
Heavy Metal Ion ◽  
Ambient Conditions ◽  
X Ray ◽  
Metal Ion Adsorption ◽  
Map Analysis

Abstract The new clay modified with triazole and triazolium ligands was prepared in this research. These materials were applied as abundant and eco-friendly adsorbents for removal of heavy metal ions such as Pb(II), Co(II) and Zn(II) ions. The adsorption efficiency of these materials was calculated by relevant equations such as Langmuir and Freundlich as well as kinetic studies with pseudo-first-order and pseudo-second-order models. These adsorbents proved to be very active on heavy metal ion adsorption. The characterization of these new materials was carried out by various techniques such as X-ray diffraction, thermogravimetric analysis, scanning electron microscope (SEM), X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy as well as SEM-map analysis. Eventually, the catalytic activity of the adsorbents which treated with heavy metal ion solutions was studied in the reduction of nitroarenes to its corresponding amines. The prepared adsorbent–catalyst materials indicated efficient catalytic activity in the reduction of nitroarenes to amines in ambient conditions. Graphic abstract

Sign in / Sign up

Export Citation Format

Share Document