Hafnium-Doped Mesoporous Silica as Efficient Lewis Acidic Catalyst for Friedel–Crafts Alkylation Reactions

The development of an efficient solid catalyst for Friedel–Crafts (FC) reactions is of great importance to organic synthetic chemistry. Herein, we reported the hafnium-doped mesoporous silica catalyst Hf/SBA-15 and its first use for Friedel–Crafts alkylation reactions. Catalysts with different Si/Hf ratios were prepared and characterized, among which Hf/SBA-15(20) (Si/Hf = 20:1) was the most active catalyst, offering up to 99.1% benzylated product under mild reaction conditions. The influences of reaction conditions on the product were systematically investigated and compared. Pyridine-IR characterization of the catalyst showed that Lewis acid formed the primary active sites for the Friedel–Crafts alkylation reaction. X-ray photoelectron spectroscopy (XPS) characterization revealed that the electron shift from the Hf center to the silica framework resulted in a more active Lewis metal center for FC reactions. Moreover, the catalyst was successfully applied to the alkylation reaction with different alcohols and aromatic compounds. Finally, the Hf/SBA-15(20) catalyst also showed good recyclability in the recycling runs, demonstrating its high potential of being used for large scale FC reactions in the industry.

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Diffuse Reflectance FT-IR Characterization of Active Sites under Reaction Conditions: The Production of Oxygenates in the CO/H2 Reaction

Applied Spectroscopy ◽

10.1366/0003702944027345 ◽

1994 ◽

Vol 48 (10) ◽

pp. 1208-1212 ◽

Cited By ~ 7

Author(s):

J. J. Benítez ◽

I. Carrizosa ◽

J. A. Odriozola

Keyword(s):

Infrared Spectra ◽

Active Sites ◽

Diffuse Reflectance ◽

Reaction Conditions ◽

In Situ Drifts ◽

Ft Ir

The reactivity of a Lu2O3-promoted Rh/Al2O3 catalyst in the CO/H2 reaction is reported. Methane, heavier hydrocarbons, methanol, and ethanol are obtained. In situ DRIFTS has been employed to record the infrared spectra under the actual reaction conditions. The structure of the observed COads DRIFTS bands has been resolved into its components. The production of oxygenates (methanol and ethanol) has been correlated with the results of the deconvolution calculation. Specific sites for the production of methanol and ethanol in the CO/H2 reaction over a Rh,Lu2O3/Al2O3 catalyst are proposed.

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Supported Gold Nanoparticles as Catalysts in Peroxidative and Aerobic Oxidation of 1-Phenylethanol under Mild Conditions

Nanomaterials ◽

10.3390/nano10010151 ◽

2020 ◽

Vol 10 (1) ◽

pp. 151 ◽

Cited By ~ 3

Author(s):

Ekaterina Pakrieva ◽

Ana P. C. Ribeiro ◽

Ekaterina Kolobova ◽

Luísa M. D. R. S. Martins ◽

Sónia A. C. Carabineiro ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Active Sites ◽

Density Functional ◽

Aerobic Oxidation ◽

Reaction Conditions ◽

Tert Butyl Hydroperoxide ◽

Temperature Programmed ◽

Pretreatment Atmosphere ◽

Supported Gold Nanoparticles ◽

Supported Gold

The efficiency of Au/TiO2 based catalysts in 1-phenylethanol oxidation was investigated. The role of support modifiers (La2O3 or CeO2), influence of gold loading (0.5% or 4%) and redox pretreatment atmosphere, catalyst recyclability, effect of oxidant: tert-butyl hydroperoxide (TBHP) or O2, as well as the optimization of experimental parameters of the reaction conditions in the oxidation of this alcohol were studied and compared with previous studies on 1-octanol oxidation. Samples were characterized by temperature-programmed oxygen desorption (O2-TPD) method. X-ray photoelectron spectroscopy (XPS) measurements were carried out for used catalysts to find out the reason for deactivation in 1-phenylethanol oxidation. The best catalytic characteristics were shown by catalysts modified with La2O3, regardless of the alcohol and the type of oxidant. When O2 was used, the catalysts with 0.5% Au, after oxidative pretreatment, showed the highest activity in both reactions. The most active catalysts in 1-phenylethanol oxidation with TBHP were those with 4% Au and the H2 treatment, while under the same reaction conditions, 0.5% Au and O2 treatment were beneficial in 1-octanol oxidation. Despite the different chemical nature of the substrates, it seems likely that Au+(Auδ+) act as the active sites in both oxidative reactions. Density functional theory (DFT) simulations confirmed that the gold cationic sites play an essential role in 1-phenylethanol adsorption.

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XPS-Characterization of Heterometallic Coordination Compounds with Optically Active Ligands

Journal of Chemistry ◽

10.1155/2013/370637 ◽

2013 ◽

Vol 2013 ◽

pp. 1-9 ◽

Cited By ~ 10

Author(s):

Yenny Ávila-Torres ◽

Lázaro Huerta ◽

Noráh Barba-Behrens

Keyword(s):

Photoelectron Spectroscopy ◽

Coordination Compounds ◽

Metal Ion ◽

Magnetic Behaviour ◽

Optically Active ◽

Triangular Array ◽

Antiferromagnetic Coupling ◽

Xps Characterization ◽

Alcohol Derivative

The heterometallic optical complexes [Cu2Co(S,S(+)cpse)3(H2O)3]·4H2O (1) and [Cu2Ni(S,S(+)cpse)3(H2O)3]·10H2O (2) were obtained from the mononuclear copper(II) compound by the addition of nickel(II) or cobalt(II) chlorides, where (H2cpse) is the acetyl amino alcohol derivative N-[2-hydroxy-1(R)-methyl-2(R)-phenylethyl]-N-methylglycine. In comparison with the homotrinuclear copper(II) compound [Cu3(S,S(+)cpse)3(H2O)3]·8H2O reported previously, the substitution of a copper(II) atom by one cobalt(II) ion gave place to a heterotrinuclear compound1, which presents ferromagnetic-antiferromagnetic behaviour. When substituting a copper(II) by a nickel(II) ion, the trinuclear compound2showed an antiferromagnetic coupling. The magnetic behaviour of the heterotrinuclear compounds is driven by the nature of the metal ion which was introduced in the copper(II) triangular array. The ligand and its coordination compounds were characterized by IR, UV-Vis-NIR. Their chemical was confirmed by photoelectron spectroscopy (XPS).

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Mesoporous Silica Sol-Gel as Catalyst for the Synthesis of Alkylpolyglucosides

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.620.446 ◽

2012 ◽

Vol 620 ◽

pp. 446-452 ◽

Cited By ~ 3

Author(s):

Izazi Azzahidah Amin ◽

Mohd Ambar Yarmo ◽

Nik Idris Nik Yusoff ◽

Mohd Zahid Yusoff ◽

Alifee Ayatillah

Keyword(s):

Binding Energy ◽

Mesoporous Silica ◽

Surface Area ◽

Photoelectron Spectroscopy ◽

Sol Gel ◽

Silica Sol ◽

Area Measurement ◽

Bet Surface Area ◽

Solid Catalyst ◽

Positive Mode

The synthesis of alkylpolyglucosides involves condensation of decanol with dextrose in the presence of mesoporous silica sol-gel as a catalyst. In this study, mesoporous silica was produced using sol-gel technique by converting tetraethyl orthosilicate (TEOS) into silica. The mesoporous silica was characterized using BET surface area measurement and X-ray Photoelectron Spectroscopy surface analysis. The specific BET surface area was 794m2/g. From the XPS analysis, the Si2p binding energy is 103.7 eV while the O1s binding energy is 532.8eV indicating the formation of Si-O-Si bond which attributed to SiO2. Mesoporous silica has been found efficient to be solid catalyst for synthesis alkylpolyglucosides and easy to be separated. The reaction was carried out 8 hours at 110°C-120°C under vacuum condition. The mass determination of alkylpoluglucosides has been achieved by ESI LC-MS/MS (ToF) positive-mode giving a mass peak at m/z = 343.21 corresponding to [M++ of alkylmonoglucoside peak at retention time 11.0 min.

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GIAXD and XPS Characterization of sp3C Doped SiC Superhard Nanocomposite Film

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.512-515.971 ◽

2012 ◽

Vol 512-515 ◽

pp. 971-974

Author(s):

Jian Yi ◽

Xiao Dong He ◽

Yue Sun ◽

Zhi Peng Xie ◽

Wei Jiang Xue ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Physical Vapor Deposition ◽

Grazing Incidence ◽

Nanocomposite Films ◽

Second Phase ◽

X Ray ◽

Xps Characterization ◽

Ss Substrates ◽

Sic Film

The sp3C doped SiC superhard nanocomposite films had been deposited on stainless steel (SS) substrates at different temperature by electron beam-physical vapor deposition (EB-PVD). The sp3C doped SiC film was studied by grazing incidence X-ray asymmetry diffraction (GIAXD), and X-ray photoelectron spectroscopy (XPS). The results of GIAXD showed that the sp3 doped SiC nanocomposite films were not perfect crystalline, which was composed with fine SiC nanocrystals, and a second phase very similar with diamond like carbon (DLC). XPS analysis showed that the excess C existing in films and turned from diamond into DLC from the surface to inner of film.

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A Single Turnover (STO) Characterization of Supported Palladium Catalysts

MRS Proceedings ◽

10.1557/proc-111-453 ◽

1987 ◽

Vol 111 ◽

Author(s):

Robert L. Augustine ◽

David R. Baum

Keyword(s):

Palladium Catalysts ◽

Active Sites ◽

Pt Catalyst ◽

Catalyst Characterization ◽

Pt Catalysts ◽

Ambient Conditions ◽

Reaction Conditions ◽

Pd Catalysts ◽

Supported Pt Catalysts

AbstractWhile the STO catalyst characterization procedure has been applied to a variety of supported Pt catalysts, application of this technique to the characterization of supported Pd catalysts showed that there were several significant differences between the Pt and the Pd catalysts. Under STO reaction conditions each surface site on a Pt catalyst reacts only once so there is a 1:1 relationship between the product composition and the densities of the various types of active sites present. With Pd catalysts under these same conditions, alkene isomerization takes place so readily that the amount of isomerized product formed depends on the contact time of the reactant pulse with the catalyst so there is no direct relationship between the amount of isomerization and the number of isomerization sites present. On Pt there are some direct saturation sites present on which H2 is rather weakly held. Such sites are not present on Pd catalysts. The reactive surface of supported Pt catalysts remains constant on long exposure to air. With Pd catalysts exposure to air results in a decrease in saturation site densities which can be reversed by re-reduction of the surface with H2 under ambient conditions but not completely under what can be termed “reaction conditions” where the extent of surface re-reduction decreases with catalyst age.

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XPS Characterization of Mixed Carbides Obtained from Polymer Precursors

MRS Proceedings ◽

10.1557/proc-180-811 ◽

1990 ◽

Vol 180 ◽

Cited By ~ 1

Author(s):

Gaetano Granozzi ◽

Antonella Glisenti ◽

Gian D. Soraru

Keyword(s):

Photoelectron Spectroscopy ◽

Structural Evolution ◽

Metal Alkoxides ◽

Pyrolysis Process ◽

X Ray ◽

Polymer Precursors ◽

Xps Characterization

ABSTRACTPolymer precursors for Si-C, Si-Ti-C-O and Si-Al-C-O systems have been obtained from polycarbosilane and the corresponding metal alkoxides. X-ray Photoelectron Spectroscopy (XPS) has been used to follow the structural evolution of these preceramic compounds during the pyrolysis process.

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Characterization of Ge1-x-ySixSny Ternary Alloy Surfaces and Ni/Ge1-x-ySixSny Bilayer Reactions by X-Ray Techniques

MRS Proceedings ◽

10.1557/opl.2015.553 ◽

2015 ◽

Vol 1770 ◽

pp. 19-24 ◽

Cited By ~ 1

Author(s):

Gordon J. Grzybowski ◽

Arnold Kiefer ◽

Bruce Claflin

Keyword(s):

Photoelectron Spectroscopy ◽

Chemical Shifts ◽

Surface Oxidation ◽

Device Fabrication ◽

Ternary Alloys ◽

Ambient Conditions ◽

X Ray ◽

Wide Range ◽

Xps Characterization

ABSTRACTInterest in next generation devices that integrate photonic and electronic functionality is focused on extending the capability of existing group IV material systems while maintaining compatibility with existing processing methods and procedures. One such class of materials which has been recently developed, Ge1-x-ySixSny ternary alloys, is being investigated for integrated Si photonics, solar cell materials, telecommunication applications, and for IR photodetectors. These alloys afford the opportunity to decouple the band gap energies and lattice constants over a wide range of values, potentially yielding direct and indirect character that can be coupled with a variety of different substrates dependent on composition.In the present work, we report X-ray photoelectron spectroscopy (XPS) characterization of Ge1-x-ySixSny alloys grown by gas-source molecular beam epitaxy (GS-MBE) and investigate Ni- Ge1-x-ySiySny bilayer reactions with x-ray diffraction (XRD). The surface oxidation of samples stored in ambient conditions were measured with XPS. High resolution spectra showed chemical shifts of Ge, Si and Sn peaks consistent with Ge-O, Si-O and Sn-O bond formation. Depth profiling indicates a homogeneous composition throughout the bulk of the sample with surface oxidation confined to the top few nanometers. A highly tin-enriched layer was indicated at the surface of the material, while silicon was observed to be either enriched or depleted at the surface depending on the sample.To study the interaction of the ternary with an ohmic contact commonly used in device fabrication processes today, nickel layers 30 nm thick were evaporated onto the alloys and were annealed in nitrogen up to 400 °C for periods as long as 1 hour. The XRD data show that the Ni2(Ge1-x-ySixSny) phase forms first followed by Ni(Ge1-x-ySixSny).

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XPS Characterization of a Commercial Cu/ZnO/Al2O3 Catalyst: Effects of Oxidation, Reduction, and the Steam Reformation of Methanol

Applied Spectroscopy ◽

10.1366/0003702884429148 ◽

1988 ◽

Vol 42 (5) ◽

pp. 754-760 ◽

Cited By ~ 32

Author(s):

Brian E. Goodby ◽

Jeanne E. Pemberton

Keyword(s):

Photoelectron Spectroscopy ◽

Surface Region ◽

Peak Fitting ◽

Oxidation Reduction ◽

Xps Characterization ◽

Fitting Procedures ◽

Cu Oxidation ◽

Al2o3 Catalyst ◽

Oxidative State

X-ray photoelectron spectroscopy (XPS) is used to characterize the surface region of a commercial Cu/ZnO/Al2O3 (33/66/1 wt %) catalyst. A systematic study of the effects of oxidation, reduction, and the steam reformation of methanol on the oxidative state of the Cu component is presented. The Zn XPS features show no changes due to the various treatments. Peak fitting procedures were developed to quantitate the Cu oxidation states on the basis of the XPS Cu 2P3/2 main and satellite features. After oxidation in pure O2 at 300°C, all Cu exists as Cu+2. The Cu/Zn ratio changes from 0.28 to 0.37 as a result of this oxidation, in comparison to the ratio in the catalyst as-received. The reduction studies involved different H2/N2 mixtures (15 to 100% H2) and temperatures (250 to 300°C). The catalyst always contains Cu+1 (7.0 ± 5.0%) and Cu° (93.0 ± 5.0%) sifter reduction. The Cu/Zn ratio decreases from approximately 0.37 in the oxidized catalyst to 0.13 after reduction. After methanol-steam reformation with a 50/50 vol % mixture, the Cu 2P3/2 and Auger features are indicative of complete reduction of all Cu in the catalyst to a reduced Cu° state not seen previously. Changes in the Cu/ Zn ratio of the surface are interpreted in terms of changes in surface morphology of the Cu species.

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Precise Identification and Characterization of Catalytically Active Sites on the Surface of γ-Alumina

10.26434/chemrxiv.11829576 ◽

2020 ◽

Author(s):

Konstantin Khivantsev ◽

Nicholas R. Jaegers ◽

Ja-Hun Kwak ◽

János Szanyi ◽

Libor Kovarik

Keyword(s):

Active Sites ◽

Large Scale ◽

High Surface ◽

High Surface Area ◽

Carbonyl Complexes ◽

True Nature ◽

Catalytically Active ◽

Active Research ◽

First Time

γ-alumina is one of the oldest and most important commercial catalytic materials with high surface area and stability. These attributes enabled its use as the first commercial large-scale heterogeneous catalyst for ethanol dehydration. Despite progress in materials characterization and over a hundred years of active research, the nature of the specific sites on the surface of γ-alumina which are responsible for its unique catalytic properties has remained obscure and controversial. Herein, we identify for the first time using combined infrared spectroscopy, electron microscopy and solid-state nuclear magnetic resonance measurements that the octahedral amphoteric (O)5Al(VI)-OH sites on the massively restructured (110) facets on typical rhombus-platelet γ-alumina as well as (100) segments of irrational surfaces (invariably always present in all γ-alumina samples) are largely responsible for its unique catalytic activity. Such (O)5Al(VI)-OH sites are also present on macroscopically defined (100) facets γ-alumina of different, more elongated/rod-like geometry. They anchor organometallic fragments and isolated metal atoms. The exact mechanism by which these sites lose -OH group upon thermal dehydroxylation is clarified, resulting in coordinatively unsaturated penta-coordinate Al+3O5 sites that can activate nitrogen. These coordinatively unsaturated Al penta-coordinate sites demonstrate new chemistry, producing the first well-defined thermally stable Al-carbonyl complexes. Our findings reunite and successfully clarify the contradictory findings in the literature over the last century, illuminating the true nature and the relationship between the catalytically active and coordinatively unsaturated Al sites on the surface of γ-alumina.

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