Gaseous Cl2 Research Articles

Improved Operation of Chloralkaline Reversible Cells with Mixed Metal Oxide Electrodes Made Using Microwaves.

This study focuses on the synthesis of mixed metal oxide anodes (MMOs) with the composition Ti/RuO2Sb2O4Ptx (where x = 0, 5, 10 mol) using hybrid microwave irradiation heating. The synthesized electrodes were characterized using scanning electron microscopy, X-ray energy-dispersive analysis, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. These electrodes were then evaluated in both bulk electrolytic and fuel cell tests within a reversible chloralkaline electrochemical cell. The configurations using the electrodes Ti/(RuO2)0.7-(Sb2O4)0.3 and Ti/(RuO2)66.5-(Sb2O4)28.5-Pt5 presented lower onset potential for oxygen and chlorine evolution reactions and reduced resistance to charge transfer compared to the Ti/(RuO2)63-(Sb2O4)27-Pt10 variant. These electrodes demonstrated notable performance in reversible electrochemical cells, achieving Coulombic efficiencies of up to 60% when operating in the electrolytic mode at current densities of 150 mA cm-2. They also reached maximum power densities of 1.2 mW cm-2 in the fuel cell. In both scenarios, the presence of platinum in the MMO coating positively influenced the process. Furthermore, a significant challenge encountered was crossover through the membranes, primarily associated with gaseous Cl2. This study advances our understanding of reversible electrochemical cells and presents possibilities for further exploration and refinement. It demonstrated that the synergy of innovative electrode synthesis strategies and electrochemical engineering can lead to promising and sustainable technologies for energy conversion.

Insights into Electrolytic Pre-Lithiation: A Thorough Analysis Using Silicon Thin Film Anodes.

Pre-lithiation via electrolysis, herein defined as electrolytic pre-lithiation, using cost-efficient electrolytes based on lithium chloride (LiCl), is successfully demonstrated as a proof-of-concept for enabling lithium-ion battery full-cells with high silicon content negative electrodes. An electrolyte for pre-lithiation based on γ-butyrolactone and LiCl is optimized using boron-containing additives (lithium bis(oxalato)borate, lithium difluoro(oxalate)borate) and CO2 with respect to the formation of a protective solid electrolyte interphase (SEI) on silicon thin films as model electrodes. Reversible lithiation in Si||Li metal cells is demonstrated with Coulombic efficiencies (CEff ) of 95-96% for optimized electrolytes comparable to 1 m LiPF6 /EC:EMC 3:7. Formation of an effective SEI is shown by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). electrolytic pre-lithiation experiments show that notable amounts of the gaseous product Cl2 dissolve in the electrolyte leading to a self-discharge Cl2 /Cl- shuttle mechanism between the electrodes lowering pre-lithiation efficiency and causing current collector corrosion. However, no significant degradation of the Si active material and the SEI due to contact with elemental chlorine is found by SEM, impedance, and XPS. In NCM111||Si full-cells, the capacity retention in the 100th cycle can be significantly increased from 54% to 78% by electrolytic pre-lithiation, compared to reference cells without pre-lithiation of Si.

Multi-Centered Solid-Phase Quasi-Intramolecular Redox Reactions of [(Chlorido)Pentaamminecobalt(III)] Permanganate—An Easy Route to Prepare Phase Pure CoMn2O4 Spinel

We synthesized and structurally characterized the previously unknown [Co(NH3)5Cl](MnO4)2 complex as the precursor of CoMn2O4. The complex was also deuterated, and its FT-IR, far-IR, low-temperature Raman and UV-VIS spectra were measured as well. The structure of the complex was solved by single-crystal X-ray diffraction and the 3D-hydrogen bonds were evaluated. The N-H…O-Mn hydrogen bonds act as redox centers to initiate a solid-phase quasi-intramolecular redox reaction even at 120 °C involving the Co(III) centers. The product is an amorphous material, which transforms into [Co(NH3)5Cl]Cl2, NH4NO3, and a todorokite-like solid Co-Mn oxide on treatment with water. The insoluble residue may contain {Mn4IIIMnIV2O12}n4n−, {Mn5IIIMnIVO12}n5n− or {MnIII6O12}n6n− frameworks, which can embed 2 × n (CoII and/or CoIII) cations in their tunnels, respectively, and 4 × n ammonia ligands are coordinated to the cobalt cations. The decomposition intermediates decompose on further heating via a series of redox reactions, forming a solid CoIIMIII2O4 spinel with an average size of 16.8 nm, and gaseous N2, N2O and Cl2. The CoMn2O4 prepared in this reaction has photocatalytic activity in Congo red degradation with UV light. Its activity strongly depends on the synthesis conditions, e.g., Congo red was degraded 9 and 13 times faster in the presence of CoMn2O4 prepared at 550 °C (in air) or 420 °C (under N2), respectively.

Experimental Depth Profiles of Surfactants, Ions, and Solvent at the Angstrom Scale: Studies of Cationic and Anionic Surfactants and Their Salting Out.

Neutral impact ion scattering spectroscopy (NICISS) is used to measure the depth profiles of ionic surfactants, counterions, and solvent molecules on the angstrom scale. The chosen surfactants are 0.010 m tetrahexylammonium bromide (THA+/Br-) and 0.0050 m sodium dodecyl sulfate (Na+/DS-) in the absence and presence of 0.30 m NaBr in liquid glycerol. NICISS determines the depth profiles of the elements C, O, Na, S, and Br through the loss in energy of 5 keV He atoms that travel into and out of the liquid, which is then converted into depth. In the absence of NaBr, we find that THA+ and its Br- counterion segregate together because of charge attraction, forming a narrow double layer that is 10 Å wide and 150 times more concentrated than in the bulk. With the addition of NaBr, THA+ is "salted out" to the surface, increasing the interfacial Br- concentration by 3-fold and spreading the anions over a ∼30 Å depth. Added NaBr similarly increases the interfacial concentration of DS- ions and broadens their positions. Conversely, the dissolved Br- ions are significantly depleted over a depth of 0-40 Å from the surface because of charge repulsion from DS- ions within the interfacial region. These different interfacial Br- propensities correlate with previously measured gas-liquid reactivities: gaseous Cl2 readily reacts with Br- ions in the presence of THA+ but drops 70-fold in the presence of DS-, demonstrating that surfactant headgroup charge controls the reactivity of Br- through changes in its depth profile.

Control of Interfacial Cl2 and N2O5 Reactivity by a Zwitterionic Phospholipid in Comparison with Ionic and Uncharged Surfactants.

Gas-liquid scattering experiments reveal that charge-separated but neutral (zwitterionic) surfactants catalyze the oxidation of dissolved Br- to Br2 by gaseous Cl2 at the surface of a 0.3 M NaBr/glycerol solution. Solutions of NaBr dissolved in glycerol with no surfactant were compared with solutions coated with zwitterionic, cationic, and anionic surfactants at dilute surface concentrations of 1.1 to 1.5 × 1014 cm-2 (less than 65% of maximum chain packing). The zwitterionic phospholipid enhances Cl2 conversion of Br- to Br2 by a factor of 1.61 ± 0.15, in comparison with a 14-fold enhancement by a cationic surfactant (tetrahexylammonium) and a five-fold suppression by an anionic surfactant (dodecyl sulfate). Further studies indicate that even an uncharged surfactant, monododecanoylglycerol, enhances Cl2 → Br2 production. Similar behavior is observed for the oxidation of Br- to Br2 by N2O5; it is just slightly suppressed by the phospholipid and strongly enhanced by the cationic surfactant. Collectively, these results suggest that attractions and repulsions between the negative Br- ions and the positive and negative charges of the surfactant headgroups draw Br- ions to the surface or repel them away. At low coverages, ion-induced dipole and dispersion interactions between the CH2 groups and Br- or Cl2 may also enhance reactivity. These results demonstrate that the hydrocarbon chains of loosely packed surfactants do not necessarily block gas-liquid reactions but that positively charged, and even uncharged, groups can instead facilitate reactions by bringing gas-phase and solution-phase reagents together in the interfacial region.

Simultaneous removal of NO and Hg0 from oxy-fuel combustion flue gas over CeO2-modified low-V2O5-based catalysts

CeO2-doped low-V2O5-based catalysts (V0.5WCe/Ti) were investigated and showed outstanding stability for the simultaneous removal of NO (92.5%) and Hg0 (75%) from oxy-fuel combustion flue gas in 50h compared to a normal V1.0W/Ti catalyst. The good NH3-SCR performance of the V0.5WCe/Ti catalyst was due to the enhancement in acidity that arose from the introduced vanadium oxide, the better redox capability and greater amount of surface adsorbed oxygen species (O2−, O− and O2−) by Ce-modification, which generated a large amount of NO2, conducting the “fast SCR reaction”. Hg0 oxidation was strongly affected by surface adsorbed oxygen and CO functional groups in the absence of HCl in CO2-enriched flow conditions, while the reaction was mostly between Hg0(ad)/HgO(ad) and gaseous Cl⁎ or Cl2 in the presence of both HCl and O2. In addition, a high concentration of CO2 inhibited NO conversion, because of the rate of diffusion, but promoted Hg0 removal. Furthermore, while a high concentration of HCl prohibited NO conversion due to the formation of VCl and CeCl on the catalyst surface, Hg0 adsorption and catalytic oxidation were inhibited when SO2 and H2O coexisted in the flue gas.

Simple Process for Sidewall Modification of Multi-Walled Carbon Nanotubes with Polymer Side Chain Radicals Generated by Ultraviolet-Induced C–Cl Bond Dissociation of Polystyrene Derivatives

In this work, we investigated a simple one-step process for the formation of chemical bonds between multi-walled carbon nanotubes (MWCNTs) and benzyl-type side chain radicals generated by UV photolysis of polystyrene derivatives containing the chloromethyl (–CH2Cl) group. Poly(4-chloromethyl)styrene, or styrene/4-(chloromethyl)styrene random copolymer, was mixed with MWCNTs in 1-methyl-2-pyrrolidone and irradiated with ultraviolet (UV) light. Films of polymer/MWCNT mixtures before and after UV irradiation were fabricated, and then examined by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. According to the XPS analysis, the amount of Cl atoms in the mixture was found to decrease upon UV irradiation, indicating that the Cl atoms generated by photolysis of chloromethyl groups escaped from the reaction system in the form of gaseous Cl2. The structural change of CNTs after UV irradiation was also observed by comparing the G/D ratios (the intensity ratio of the G to D bands) of the Raman spectra obtained before and after UV irradiation. Similar phenomena were also confirmed in the case of the polymer/MWCNT mixture containing hydroxylammonium chloride as a dispersant of MWCNTs. These results confirmed the UV-induced covalent bond formation between polymer side chains and MWCNTs.

Ash deposition behaviours upon the combustion of low-rank coal blends in a 3 MWth pilot-scale pulverised coal-fired furnace

This paper aims to clarify the characteristics of ash deposits formed upon the blending of two low-rank lignites that have distinctively different properties, i.e. one has a low ash melting point, rich in Na and S, while another has a higher ash melting point, rich in Ca and Cl. A 3 MWth pilot-scale furnace has been used for the combustion, with a variety of cooling oil-jacketed probes installed along the furnace for ash deposit sampling. As have been confirmed, there are strong synergetic interactions between the ash-forming elements of the two lignites. At the mass fractions of 50% and 70% for the high-Cl coal, the ash fusion temperatures are even higher than the two single coals. The synergetic interactions between two coals enhanced the formation of crystallised species such as hematite, sulfates and carbonates that are mixed with Ca-Si-O matrix to reduce its stickiness and slagging propensity in the burner vicinity. The blending of up to 50wt% high-Cl coal resulted in the enhanced emission of gaseous HCl and Cl2, whereas the high-Cl coal mass fraction above 50wt% enhanced the formation of NaCl in super-heater ash deposits, via the chlorination of sodium from low-Cl coal, which are detrimental to tube corrosion. The Cl chemistry is complicated for the lignite blending combustion. The emission of gaseous Cl2 is remarkable, accounting for 6–8% of the total chorine that is far higher than the predicted values based on the thermodynamic equilibrium. The Cl2 emitted at high temperatures is also stable, with almost all the consumption reactions being frozen upon the rapid quenching of flue gas. The blending of up to 50wt% high-Cl coal is viable in minimising ash slagging and fouling. However, special materials and/or coating technologies should be employed to minimise the Cl2-related corrosion for the water tubes.

Bent Carbon Surface Moieties as Active Sites on Carbon Catalysts for Phosgene Synthesis.

Active sites in carbon-catalyzed phosgene synthesis from gaseous CO and Cl2 have been identified using C60 fullerene as a model catalyst. The carbon atoms distorted from sp(2) coordination in non-planar carbon units are concluded to generate active Cl2 . Experiments and density functional theory calculations indicate the formation of a surface-bound [C60 ⋅⋅⋅Cl2 ] chlorine species with radical character as key intermediate during phosgene formation. It reacts rapidly with physisorbed CO in a two-step Eley-Rideal-type mechanism.

Bent Carbon Surface Moieties as Active Sites on Carbon Catalysts for Phosgene Synthesis

AbstractActive sites in carbon‐catalyzed phosgene synthesis from gaseous CO and Cl2 have been identified using C60 fullerene as a model catalyst. The carbon atoms distorted from sp2 coordination in non‐planar carbon units are concluded to generate active Cl2. Experiments and density functional theory calculations indicate the formation of a surface‐bound [C60⋅⋅⋅Cl2] chlorine species with radical character as key intermediate during phosgene formation. It reacts rapidly with physisorbed CO in a two‐step Eley–Rideal‐type mechanism.

ChemInform Abstract: Synthesis and Structural Characterization of Ammonio/Hydroxo Undecachloro‐closo‐Dodecaborates [B12Cl11NH3]‐/ [B12Cl11OH]2‐ and Their Derivatives.

AbstractThe [B12Cl11NH3]‐ anion in (IV) and [B12Cl11OH]2‐ in (VIII) are prepared by chlorination of the corresponding hydride precursors with SO2Cl2 instead of SbCl5 or gaseous Cl2.

Chlorination of RuO2 with gaseous Cl2 between 998 and 1123 K

Employing methods of separation based on selective chlorination it is possible to separate valuable components, such as metals and rare earths, from ores and / or solid wastes. In this paper we study the chlorination reaction of ruthenium oxide. This element is among nuclear fission products, also part of many electronic wastes and numerous catalysts in the chemical industry. The study of the chlorination reaction of ruthenium oxide will allow to analyze in which conditions it is possible to apply gaseous chlorination for ruthenium recovery. No systematic studies on the kinetics and chemical mechanism of ruthenium oxide chlorination are available in the literature. In the present study, we performed a thermodynamic analysis of possible reaction pathways. The reaction products were identified by scanning electron microscopy (SEM) and x-ray Diffraction (xrd), and the experimental conditions for obtaining stable α-RuCl3 by RuO2 chlorination and subsequent heating in Cl2 were established. The starting temperature for the chlorination was determined at 983K. The observed mass loss is due to formation of volatile products. We analyzed the effects of gas flow rate, crucible geometry, and sample mass on the kinetics of the reaction, in order to establish the corresponding experimental reaction conditions for chemical kinetic control. The effect of temperature was analyzed and an apparent activation energy of 173 ± 8kJ.mol-1 was obtained for the chlorination reaction.

Lithium extraction from β-spodumene through chlorination with chlorine gas

The extraction of lithium by means of the chlorination roasting of β-spodumene has been studied in the temperature range from 1000 to 1100 °C for periods of time from 0 to 180 min. The roasting was carried out in a fixed bed reactor using pure gaseous Cl2 as chlorinating agent. The reactants and products were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), atomic absorption spectrometry (AAS), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The roasting of β-spodumene with pure Cl2 at 1100 °C for the period of 150 min led to quantitative extraction of lithium as lithium chloride. The solid products of the reaction of β-spodumene with Cl2 were found to be Al6Si2O13 (mullite), and Si2O (cristobalite).

Surfactant-Promoted Reactions of Cl2 and Br2 with Br– in Glycerol

Gas-liquid scattering experiments are used to explore reactions of gaseous Cl2 and Br2 with a 0.03 M solution of the surfactant tetrahexylammonium bromide (THABr) dissolved in glycerol. At thermal collision energies, 79 ± 2% of incident Cl2 molecules react with Br(-) to form Cl2Br(-) in the interfacial region. This reaction probability is three times greater than the reactivity of Cl2 with 3 M NaBr-glycerol, even though the interfacial Br(-) concentrations are similar in each solution. We attribute the high 79% uptake to the presence of surface THA(+) ions that stabilize the Cl2Br(-) intermediate as it is formed in the charged, hydrophobic pocket created by the hexyl chains. Cl2Br(-) generates the single exchange product BrCl in a 1% yield close to the surface, while the remaining 99% desorbs as the double exchange product Br2 over >0.1 s after diffusing deeply into the bulk. When NaCl is added to the surfactant solution in a 20:1 Cl(-)/Br(-) ratio, the Cl2 reaction probability drops from 79% to 46 ± 1%, indicating that Cl(-) in the interfacial region only partially blocks reaction with Br(-). In parallel, we observe that gaseous Br2 molecules dissolve in 0.03 M THABr for 10(4) times longer than in 3 M NaBr. We attribute this change to formation of stabilizing interfacial and bulk-phase THA(+)Br3(-) ion pairs, in analogy with the capture of Cl2 and formation of THA(+)Cl2Br(-) pairs. The THA(+) ion appears to be a powerful interfacial catalyst for promoting reaction of Cl2 and Br2 with Br(-) and for ferrying the resultant ions into solution.

Experimental Study for the Identification of the Nascent Product of OH Heterogeneous Reaction with NaCl using Chemical Ionization Mass Spectrometry

An experimental study on the nascent product of the OH heterogeneous reaction with NaCl was performed under dryand wet conditions using a bead-filled flow tube system coupled to a high-pressure chemical ionization mass spectrometer. Theozone concentration in the flow tube for the atomic hydrogen removal was varied in order to control the conversion reaction ofmolecular chlorine into HCl for the identification of the nascent product. The mass spectrometric observation was that the O3introduction reduced the concentration HCl, while it increased the concentration of Cl2 and ClO. Based on the experimentalresults, we suggest that the nascent product of the titled reaction is gaseous Cl2, which is followed by fast conversion into HCl inpresence of H. No significant difference in the concentration profile between under dry and wet (RH = 2%) conditions wasobserved.

AsS2Cl—an Arsenic(v) Compound? Formation, Stability and Structure of gaseous AsSCl and AsS2Cl—a combined experimental and theoretical study

By reaction of solid As(4)S(4) with gaseous Cl(2) at a temperature of 410 K gaseous AsSCl and AsS(2)Cl are formed. Unexpectedly in AsS(2)Cl the arsenic is not of formal oxidation state +V but +III: the molecular structure of AsS(2)Cl is arranged as a 1-chloro-dithia-arsirane and comprises an hitherto unknown AsS(2) three-membered ring. Thermodynamic data on AsSCl and AsS(2)Cl are obtained by mass spectrometry (MS). The experimental data are extended and confirmed by ab initio quantum chemical calculations (QC). The following values are given: Δ(f)H(0)(298)(AsSCl) = -5.2 kJ mol(-1) (MS), Δ(f)H(0)(298)(AsSCl) = 1.7 kJ mol(-1) (QC), S(0)(298)(AsSCl) = 296.9 J K(-1) mol(-1) (QC) and c(p)(0)(T)(AsSCl) = 55.77 + 3.97 × 10(-3)T- 4.38 × 10(5)T(-2)- 1.83 × 10(-6)T(2) and Δ(f)H(0)(298)(AsS(2)Cl) = -39.0 kJ mol(-1) (MS), Δ(f)H(0)(298)(AsS(2)Cl) = -20.2 kJ mol(-1) (QC), S(0)(298)(AsS(2)Cl) = 321.3 J K(-1) mol(-1) (QC) and c(p)(0)(T)(AsS(2)Cl) = 80.05 + 5.09 × 10(-3)T- 7.61 × 10(5)T(-2)- 2.35 × 10(-6)T(2) (298.15 K < T < 1000 K) (QC). The ionization energies are determined (IP(AsSCl) = 10.5, IP(AsS(2)Cl) = 10.2 eV). The IR spectrum of AsSCl is detected by means of matrix isolation spectroscopy. The estimated force constant f(As=S) = 4.47 mdyn·Å(-1) gives rise to an As=S double bond.

ChemInform Abstract: Formation and Stability of Gaseous WS2Cl2, WS2Br2 and WS2I2 — A Combined Experimental and Theoretical Study.

AbstractThe reactions of solid WS2 with gaseous Cl2, Br2 and I2 are monitored by mass spectrometry.

Experimental and Theoretical Study of Centrifugal Flow Singlet Oxygen Generator

We designed and realized a novel centrifugal flow singlet oxygen generator (CFSOG) that was originally proposed by Emanuel [Proc. SPIE 5448 (2004) 233]. In this device, singlet oxygen O2(1Δ) is generated by the reaction of gaseous Cl2 with aqueous basic hydrogen peroxide (BHP) that flows rapidly along an arc-shaped concave to form a rotating liquid layer, so that the nascent O2(1Δ) generated in the liquid phase will be separated from it quickly to suppress the collision quenching loss of O2(1Δ) with the help of the enormous centrifugal force produced by the rotating fluid. Our preliminary experiment shows that, because the specific reactive surface area of this novel singlet oxygen generator (SOG) is much larger than that of the jet-type SOG normally used in current chemical oxygen–iodine laser (COIL), enhanced performance of O2(1Δ) yield ∼60%, O2(1Δ) partial pressure ∼31 Torr, and an extremely high chlorine utilization within 96–98% have been realized.

Preliminary study of a centrifugal-flow singlet oxygen generator

By using the concept of a high-pressure, gravity-independent singlet oxygen generator (SOG) proposed by Emanuel and based on the principle that a rotating fluid is capable of producing an enormous centrifugal force, a novel-type centrifugal-flow singlet oxygen generator (CFSOG) was designed and constructed. In this device, O2(1Δ) was generated in the reaction of gaseous Cl2 with a rotating basic hydrogen peroxide (BHP) liquid flow and then was removed from the BHP liquid phase by the centrifugal force. Meanwhile, the microdroplets formed during the Cl2+BHP reaction were removed from the O2(1Δ) gas flow by the centrifugal force produced by the high-speed flow along an arc-shaped channel. Preliminary investigations showed that, because the specific reactive surface area of this SOG was noticeably larger than that of the jet-SOG normally used in current chemical oxygen–iodine lasers (COILs), the O2(1Δ) yield of ∼60%, the O2(1Δ) partial pressure as high as 31 Torr, and chlorine utilisation higher than 96% were realised. Moreover, steady operation was obtained.

Density Functional Theory Calculations of Solid Solutions of Fluor- and Chlorapatites

Electronic structure calculations based on density functional theory are employed to investigate the uptake and distribution of chloride ions into the fluorapatite structure. The calculated structural parameters of the two minerals are in good agreement with the experimental hexagonal structures. Electron density contour plots show the apatite structure to be an ionic crystal, where the phosphate groups behave as polyanions. The replacement of F- ions in fluorapatite by Cl- from gaseous Cl-2 is a highly endothermic process at all partial concentrations (similar to250 kJ mol(-1)), which is in line with the high stability and dominance of the fluorapatite form of these materials. The replacement of F- ions from chlorapatite with the formation of fluorapatite is much less endothermic (<8 kJ mol-1). The most stable structure with a F--to-Cl- ratio of 1:1 contains complete columns of F- and Cl- ions in the c direction. The low calculated excess heats of solid solution of chlor- and fluorapatite (<8 kJ mol-1) are in agreement with the widespread occurrence of Cl- in both geological and biological apatites, as well as with the ease of synthesis of mixed chlorfluorapatites, and indicate that Cl- could easily be absorbed into fluorapatite when both materials are present.