Purification of Hydrogen from CO with Cu/ZSM-5 Adsorbents

The transition to a hydrogen economy requires the development of cost-effective methods for purifying hydrogen from CO. In this study, we explore the possibilities of Cu/ZSM-5 as an adsorbent for this purpose. Samples obtained by cation exchange from aqueous solution (AE) and solid-state exchange with CuCl (SE) were characterized by in situ EPR and FTIR, H2-TPR, CO-TPD, etc. The AE samples possess mainly isolated Cu2+ cations not adsorbing CO. Reduction generates Cu+ sites demonstrating different affinity to CO, with the strongest centres desorbing CO at about 350 °C. The SE samples have about twice higher Cu/Al ratios, as one H+ is exchanged with one Cu+ cation. Although some of the introduced Cu+ sites are oxidized to Cu2+ upon contact with air, they easily recover their original oxidation state after thermal treatment in vacuum or under inert gas stream. In addition, these Cu+ centres regenerate at relatively low temperatures. It is important that water does not block the CO adsorption sites because of the formation of Cu+(CO)(H2O)x complexes. Dynamic adsorption studies show that Cu/ZSM-5 selectively adsorbs CO in the presence of hydrogen. The results indicate that the SE samples are very perspective materials for purification of H2 from CO.

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Hydrogen bonding steers the product selectivity of electrocatalytic CO reduction

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1900761116 ◽

2019 ◽

Vol 116 (19) ◽

pp. 9220-9229 ◽

Cited By ~ 20

Author(s):

Jingyi Li ◽

Xiang Li ◽

Charuni M. Gunathunge ◽

Matthias M. Waegele

Keyword(s):

Electrostatic Interactions ◽

Co Adsorption ◽

Product Selectivity ◽

Adsorption Sites ◽

Differential Electrochemical Mass Spectrometry ◽

Liquid Reaction ◽

Environment Control ◽

Adsorbed Co ◽

Co Reduction ◽

Alkyl Ammonium

The product selectivity of many heterogeneous electrocatalytic processes is profoundly affected by the liquid side of the electrocatalytic interface. The electrocatalytic reduction of CO to hydrocarbons on Cu electrodes is a prototypical example of such a process. However, probing the interactions of surface-bound intermediates with their liquid reaction environment poses a formidable experimental challenge. As a result, the molecular origins of the dependence of the product selectivity on the characteristics of the electrolyte are still poorly understood. Herein, we examined the chemical and electrostatic interactions of surface-adsorbed CO with its liquid reaction environment. Using a series of quaternary alkyl ammonium cations (methyl4N+, ethyl4N+, propyl4N+, and butyl4N+), we systematically tuned the properties of this environment. With differential electrochemical mass spectrometry (DEMS), we show that ethylene is produced in the presence of methyl4N+ and ethyl4N+ cations, whereas this product is not synthesized in propyl4N+- and butyl4N+-containing electrolytes. Surface-enhanced infrared absorption spectroscopy (SEIRAS) reveals that the cations do not block CO adsorption sites and that the cation-dependent interfacial electric field is too small to account for the observed changes in selectivity. However, SEIRAS shows that an intermolecular interaction between surface-adsorbed CO and interfacial water is disrupted in the presence of the two larger cations. This observation suggests that this interaction promotes the hydrogenation of surface-bound CO to ethylene. Our study provides a critical molecular-level insight into how interactions of surface species with the liquid reaction environment control the selectivity of this complex electrocatalytic process.

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IN-SITU CORE-LEVEL PHOTOELECTRON SPECTROSCOPY OF ADSORBATES ON SURFACES INVOLVING A MOLECULAR BEAM — GENERAL SETUP AND FIRST EXPERIMENTS

Surface Review and Letters ◽

10.1142/s0218625x0200297x ◽

2002 ◽

Vol 09 (02) ◽

pp. 797-801 ◽

Cited By ~ 80

Author(s):

R. DENECKE ◽

M. KINNE ◽

C. M. WHELAN ◽

H.-P. STEINRÜCK

Keyword(s):

High Resolution ◽

Photoelectron Spectroscopy ◽

Molecular Beam ◽

Co Adsorption ◽

Core Level ◽

Supersonic Molecular Beam ◽

Adsorption Sites ◽

Coverage Dependence ◽

Local Pressures

In this contribution we introduce a new apparatus combining high-resolution photoelectron spectroscopy and supersonic molecular beam techniques designed to follow simple surface reactions like adsorption, desorption or oxidation in situ in a time- and temperature-resolved manner. Using high brightness synchrotron radiation high resolution core-level spectra can be obtained in less than 3 s. The molecular beam allows for local pressures of up to 1 · 10-5 mbar and translational energies of the molecules of up to 2 eV in the case of CO. Preliminary examples of CO adsorption on Pt(111) are shown, where kinetic parameters can be derived from the coverage dependence of the different adsorption sites.

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Synthesis, Characterization and Application of Polypyrrole Functionalized Nanocellulose for the Removal of Cr(VI) from Aqueous Solution

Polymers ◽

10.3390/polym13213691 ◽

2021 ◽

Vol 13 (21) ◽

pp. 3691

Author(s):

Norah Salem Alsaiari ◽

Khadijah Mohammedsaleh Katubi ◽

Fatimah Mohammed Alzahrani ◽

Abdelfattah Amari ◽

Haitham Osman ◽

...

Keyword(s):

Heavy Metals ◽

Aqueous Solution ◽

Cost Effective ◽

Polymerization Reaction ◽

Maximum Adsorption Capacity ◽

Minor Effect ◽

Toxic Substances ◽

Excellent Thermal Stability ◽

Adsorption Sites ◽

Hydrolysis Of Cellulose

Heavy metals are toxic substances that pose a real danger to humans and organisms, even at low concentration. Therefore, there is an urgent need to remove heavy metals. Herein, the nanocellulose (NC) was synthesized by the hydrolysis of cellulose using sulfuric acid, and then functionalized using polypyrrole (ppy) through a polymerization reaction to produce polypyrrole/nanocellulose (ppy/NC) nanocomposite. The synthesized nanocomposite was characterized using familiar techniques including XRD, FT-IR, SEM, TEM, and TGA. The obtained results showed a well-constructed nanocomposite with excellent thermal stability in the nano-sized scale. The adsorption experiments showed that the ppy/NC nanocomposite was able to adsorb hexavalent chromium (Cr(VI)). The optimum pH for the removal of the heavy metal was pH 2. The interfering ions showed minor effect on the adsorption of Cr(VI) resulted from the competition between ions for the adsorption sites. The adsorption kinetics were studied using pseudo 1st order and pseudo 2nd order models indicating that the pseudo second order model showed the best fit to the experimental data, signifying that the adsorption process is controlled by the chemisorption mechanism. Additionally, the nanocomposite showed a maximum adsorption capacity of 560 mg/g according to Langmuir isotherm. The study of the removal mechanism showed that Cr(VI) ions were removed via the reduction of high toxic Cr(VI) to lower toxic Cr(III) and the electrostatic attraction between protonated ppy and Cr(VI). Interestingly, the ppy/NC nanocomposite was reused for Cr(VI) uptake up to six cycles showing excellent regeneration results. Subsequently, Cr(VI) ions can be effectively removed from aqueous solution using the synthesized nanocomposite as reusable and cost-effective adsorbent.

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Preparation and characterization of activated carbon from wheat straw to remove2, 4-dichlorophenoxy acetic acid from aqueous solutions

Current Chemistry Letters ◽

10.5267/j.ccl.2021.1.002 ◽

2021 ◽

pp. 175-186

Author(s):

Molla Tefera ◽

Mengistu Tulu

Keyword(s):

Aqueous Solution ◽

Acetic Acid ◽

Activated Carbon ◽

Wheat Straw ◽

Freundlich Isotherm ◽

Cost Effective ◽

Volatile Matter ◽

Adsorption Sites ◽

Adsorptive Behavior ◽

Dichlorophenoxy Acetic Acid

This study was focused to investigate the adsorptive behavior of activated carbon prepared from wheat straw treated with acid and base for the removal of 2, 4-dichlorophenoxy acetic acid (2,4-D). The morphology of the adsorbent was characterized using infrared spectroscopy and scanning electron microscopy. Compared with acid activated wheat straw, base activated wheat straw has provided lower ash content, moisture and volatile matter. However, it has higher iodine number than acid activated wheat straw. The removal of 2,4-D from aqueous solution was investigated at various physicochemical parameters such as pH (2–10), contact time (5–60 min), temperature (20-80 oC), amount of adsorbent (0.1-1.4 g) and initial concentration of 2,4-D (1.0-25 mg/L). The removal efficiency of 2,4-D in aqueous solution was found to be 92.02%. The equilibrium data were analyzed using Langmuir and Freundlich isotherm and the Langmuir model better describes that the active adsorption sites were homogeneously distributed on the surface of the adsorbent. Therefore, the activated carbon prepared from wheat straw treated with base can be used as efficient and cost-effective method to remove 2,4-D from aqueous solution.

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Interaction of CO with Gold in an Electrochemical Environment

10.26434/chemrxiv.13138988.v2 ◽

2021 ◽

Author(s):

Sudarshan Vijay ◽

Thomas Vagn Hogg ◽

Johan Ehlers ◽

Henrik Høgh Kristoffersen ◽

Yu Katayama ◽

...

Keyword(s):

Gas Phase ◽

Co Adsorption ◽

Underpotential Deposition ◽

Attenuated Total Reflection ◽

Adsorption Sites ◽

Surface Enhanced ◽

Adsorption Of Co ◽

Dynamics Simulations ◽

Explicit Water

<div> <div> <div> <p> </p><p>We present a joint theoretical-experimental study of CO coverage and facet selectivity on Au and under electrochemical conditions. With <i>in situ </i>attenuated total reflection surface enhanced IR spectroscopy (ATR-SEIRAS), we investigate the CO binding in an electrochemical environment. At 0.2V vs. SHE, we detect a CO band that disappears upon facet selective partial Pb underpotential deposition, suggesting that Pb blocks certain CO adsorption sites. With Pb underpotential deposition on single crystals and theoretical surface Pourbaix analysis, we eliminate (111) terraces as a possible adsorption site of CO. <i>Ab initio</i> molecular dynamics simulations of explicit water at the Au surface, shows the adsorption of CO on (211) steps to be significantly weakened relative to the (100) terrace due to competitive water adsorption. This result suggests that CO is more likely to bind to the (100) terrace<i> </i>than (211) steps in an electrochemical environment, even though Au steps in gas phase conditions bind CO* more strongly. The competition between water and adsorption can result in different binding sites for CO* on Au in gas phase and electrochemical environments. </p> <p>@font-face {font-family:"MS Mincho"; panose-1:2 2 6 9 4 2 5 8 3 4; mso-font-alt:"ＭＳ明朝"; mso-font-charset:128; mso-generic-font-family:modern; mso-font-pitch:fixed; mso-font-signature:-536870145 1791491579 134217746 0 131231 0;}@font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-536870145 1107305727 0 0 415 0;}@font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-469750017 -1073732485 9 0 511 0;}@font-face {font-family:"\@MS Mincho"; panose-1:2 2 6 9 4 2 5 8 3 4; mso-font-charset:128; mso-generic-font-family:modern; mso-font-pitch:fixed; mso-font-signature:-536870145 1791491579 134217746 0 131231 0;}p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Calibri",sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Calibri; mso-fareast-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;}.MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-family:"Calibri",sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Calibri; mso-fareast-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;}div.WordSection1 {page:WordSection1;}</p> </div> </div> </div>

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Synergistic Effects of Bimetallic AuPd and La2O3 in the Catalytic Reduction of NO with CO

Catalysts ◽

10.3390/catal11080916 ◽

2021 ◽

Vol 11 (8) ◽

pp. 916

Author(s):

Xianwei Wang ◽

Nobutaka Maeda ◽

Daniel M. Meier

Keyword(s):

Diffuse Reflectance ◽

Catalytic Reduction ◽

Synergistic Effects ◽

Co Adsorption ◽

Reduction Of No ◽

No Conversion ◽

Adsorption Sites ◽

Diffuse Reflectance Infrared ◽

Modulation Excitation

Bimetallic AuPd nanoparticles supported on TiO2 are known to catalyze the reduction of NO with CO. Here, we investigated the effects of the addition of lanthanum oxide to a AuPd/TiO2 catalyst with a AuPd particle size of 2.1–2.2 nm. The addition of La2O3 enhanced the catalytic activity; for example, at 250 °C, there was 40.9% NO conversion and 49.3% N2-selectivity for AuPd/TiO2, and 100% NO conversion and 100% N2-selectivity for AuPd-La (1:1)/TiO2. The temperature requiring 100% NO conversion dropped from 400 °C to 200 °C by the simple post-impregnation of La2O3 onto AuPd/TiO2. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) combined with modulation excitation spectroscopy (MES) demonstrated that CO adsorption occurs first on Au atoms and then, within 80 s, moves onto Pd atoms. This transformation between two adsorption sites was facilitated by the addition of La2O3.

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In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113913 ◽

1975 ◽

Vol 33 ◽

pp. 58-59

Author(s):

F. H. Louchet ◽

L. P. Kubin

Keyword(s):

Electron Microscope ◽

Transition Temperature ◽

Low Temperature ◽

Slip System ◽

Low Temperatures ◽

Tensile Axis ◽

Image Intensifier ◽

Screw Dislocations ◽

Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

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“In-Situ Raman Spectroscopy of Electronic Processes in Fullerene Thin Films

MRS Proceedings ◽

10.1557/proc-725-p10.8 ◽

2002 ◽

Vol 725 ◽

Author(s):

S.B. Phelan ◽

B.S. O'Connell ◽

G. Farrell ◽

G. Chambers ◽

H.J. Byrne

Keyword(s):

Thin Film ◽

Indium Tin Oxide ◽

Low Temperatures ◽

In Situ Raman Spectroscopy ◽

State Reduction ◽

In Situ Raman ◽

Linear Behavior ◽

Current Voltage ◽

Solid State Reduction

AbstractThe current voltage characteristics of C60 thin film sandwich structures fabricated by vacuum deposition on indium tin oxide (ITO) with an aluminium top electrode are presented and discussed. A strongly non-linear behavior and a sharp increase in the device conductivity was observed at relatively low voltages (∼2V), at both room and low temperatures (20K). At room temperature the system is seen to collapse, and in situ Raman measurements indicate a solid state reduction of the fullerene thin film to form a polymeric state. The high conductivity state was seen to be stable at elevated voltages and low temperatures. This state is seen to be reversible with the application of high voltages. At these high voltages the C60 film was seen to sporadically emit white light at randomly localized points analogous to the much documented Electroluminescence in single crystals.

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High-Entropy Alloys as Catalysts for the CO2 and CO Reduction Reactions

10.26434/chemrxiv.9850997.v1 ◽

2019 ◽

Author(s):

Jack Pedersen ◽

Thomas Batchelor ◽

Alexander Bagger ◽

Jan Rossmeisl

Keyword(s):

Density Functional ◽

Rational Design ◽

Hydrogen Adsorption ◽

Co Adsorption ◽

Reduction Reaction ◽

Supervised Machine Learning ◽

High Entropy Alloys ◽

High Entropy ◽

Co Reduction ◽

Disordered Alloy

Using the high-entropy alloys (HEAs) CoCuGaNiZn and AgAuCuPdPt as starting points we provide a framework for tuning the composition of disordered multi-metallic alloys to control the selectivity and activity of the reduction of carbon dioxide (CO2) to highly reduced compounds. By combining density functional theory (DFT) with supervised machine learning we predicted the CO and hydrogen (H) adsorption energies of all surface sites on the (111) surface of the two HEAs. This allowed an optimization for the HEA compositions with increased likelihood for sites with weak hydrogen adsorption{to suppress the formation of molecular hydrogen (H2) and with strong CO adsorption to favor the reduction of CO. This led to the discovery of several disordered alloy catalyst candidates for which selectivity towards highly reduced carbon compounds is expected, as well as insights into the rational design of disordered alloy catalysts for the CO2 and CO reduction reaction.

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Fabrication of a liquid cell for in situ transmission electron microscopy

Microscopy ◽

10.1093/jmicro/dfaa076 ◽

2020 ◽

Author(s):

Xiaoguang Li ◽

Kazutaka Mitsuishi ◽

Masaki Takeguchi

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Cost Effective ◽

Production Method ◽

Microscopy Imaging ◽

Transmission Electron ◽

In Situ Electron Microscopy ◽

Liquid Cell ◽

Si Wafer

Abstract Liquid cell transmission electron microscopy (LCTEM) enables imaging of dynamic processes in liquid with high spatial and temporal resolution. The widely used liquid cell (LC) consists of two stacking microchips with a thin wet sample sandwiched between them. The vertically overlapped electron-transparent membrane windows on the microchips provide passage for the electron beam. However, microchips with imprecise dimensions usually cause poor alignment of the windows and difficulty in acquiring high-quality images. In this study, we developed a new and efficient microchip fabrication process for LCTEM with a large viewing area (180 µm × 40 µm) and evaluated the resultant LC. The new positioning reference marks on the surface of the Si wafer dramatically improve the precision of dicing the wafer, making it possible to accurately align the windows on two stacking microchips. The precise alignment led to a liquid thickness of 125.6 nm close to the edge of the viewing area. The performance of our LC was demonstrated by in situ transmission electron microscopy imaging of the dynamic motions of 2-nm Pt particles. This versatile and cost-effective microchip production method can be used to fabricate other types of microchips for in situ electron microscopy.

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