Pressure Of HCl Research Articles

Identification of oxidized platinum single atoms on chlorinated γ–alumina support by density functional theory calculations and X-ray absorption spectroscopy

The existence and nature of oxidized Pt single atoms (SA) are unraveled on two γ-Al2O3 supported Pt catalysts (0.3 wt%) containing two chlorine contents (0.1 and 1.4 wt%) characterized by HR-HAADF-STEM and HERFD-XANES/EXAFS after a calcination treatment at 520 °C. Pt SA are revealed as PtOxCly complexes where the number of oxygen (x) and chlorine (y) ligands directly depends on the chlorine content. In order to interpret these experimental observations and provide coherent atomic structures for these PtOxCly complexes, the thermodynamic stability of the oxidized Pt SA species supported on the (100) surface model of γ-Al2O3 is determined by density functional theory (DFT) calculations as a function of the calcination conditions determined by the temperature, and partial pressures of H2O, HCl and O2. It is shown that various ligands such as Cl, OH, O (from the alumina surface or as extra-ligands) and H2O are coordinated to Pt depending on the conditions and chlorine content. Various square planar and square-based pyramidal PtOxCly species such as PtO2, PtOCl2, PtCl4 are found to be stable in calcination conditions, while octahedral Pt(OH)xCl4-x(H2O) are stabilized in XAS recording conditions. The features of these DFT simulated octahedral Pt SA species are successfully compared to XAS data. On one hand, based on thermodynamics arguments, we proposed models of supported complexes in agreement with EXAFS coordination numbers and distances (Pt-O, Pt-Cl and Pt-Al). On the other hand, the simulated XANES spectra at the Pt L3-edge for these complexes match well with the experimental HERFD-XANES and reveal that the bump feature observed between 11575 eV and 11585 eV (post-edge signal) is a tracer of the amount of Cl coordinated to Pt SA.

Comparative study of the gas phase reaction of SiCl4, SiHCl3, SiH2Cl2, and SiH3Cl by thermodynamic analysis

Thermodynamic analyses based on first-principles calculations were performed for SiHxCl4−x (x = 0 ∼ 3) to compare the characteristics of these chlorosilanes. In the range of 600 °C–1100 °C, SiCl4 almost does not decompose, while SiHCl3, SiH2Cl2, and SiH3Cl decompose and generate SiCl2 as the main radical species. SiHCl3 and SiH2Cl2 have 3.8 and 4.5 times higher SiCl2 equilibrium partial pressure than SiH3Cl at 600 °C, respectively. SiH3Cl has a lower equilibrium partial pressure of HCl than SiHCl3 and SiH2Cl2 by order level. Thus, it is expected that CVD using SiH3Cl gas is less affected by the HCl reaction.

Recovery of Ag, Au, and Pt from Printed Circuit Boards by Pressure Leaching

Reclamation of printed circuit boards (PCBs) to recover metals is gaining growing attention due to minerals being non-renewable resources. Currently, metals extraction from PCBs through an efficient and green method is still under investigation. The present investigation concerns the recycling of printed circuit boards using hydrometallurgical processes. First, the basic metals (Cu, Ni, Zn and Fe) were separated using a sulfuric acid solution at moderate temperatures. The remaining solids were characterized by SEM-EDS, whereby a high content of precious metals (Au, Ag and Pt) was observed. In the second stage, solids were leached with a solution of HCl and NaClO in a 1-L titanium reactor with varied oxygen pressure (0.2, 0.34 and 0.55 MPa), temperature (40, 50 and 80 °C) and concentration of HCl (2 and 4 M), obtaining extractions above 95% at [HCl] = 4 M, P = 0.34 MPa and T = 40 °C. The extraction increased depending on the concentration of HCl. Eh–pH diagrams for Ag–Cl–H2O, Au–Cl–H2O and Pt–Cl–H2O were constructed to know the possible species in the solution.

Thermodynamic analysis of the gas phase reaction of Mg-doped GaN growth by HVPE using MgO

The halide vapor phase epitaxy (HVPE) of Mg-doped GaN using solid MgO is investigated. Thermodynamic analysis of the reactions amongst MgO, HCl and N2 is performed based on first-principles calculations. It is found that the equilibrium partial pressure of MgCl2 is the highest amongst magnesium related molecules at 900 °C. By increasing the input partial pressure of HCl, the pressure of MgCl2 is increased, which agrees well with recently reported experiments. From these results, it is concluded that MgCl2 is the key molecule which plays the most important role for Mg-doping in fabricating p-type GaN using HVPE with MgO.

Experimental and numerical investigations of desulfurization wastewater evaporation in a lab-scale flue gas duct: evaporation and HCl release characteristics

ABSTRACT The evaporation of desulfurization wastewater using flue gas has been considered as a promising technique. However, the release of HCl during the evaporation hinders the application of this technique. Herein, we investigated the evaporation in a laboratory-scale flue duct through experimental and numerical methods. The influences of operating parameters on characteristics of evaporation and HCl release were experimentally explored. The results show that when inlet gas temperature increases from 200°C to 350°C, gaseous HCl concentration significantly increases from 5.02 ppm to 70.96 ppm and HCl release ratio accordingly increases from 1.57% to 17.32%. However, when the wastewater only contains CaCl2, the HCl release is effectively inhibited. Subsequently, the established CFD model was validated with the experiments. It was found that relative deviations between predicted and experimental outlet gas temperatures mostly locate within the range of −10%∼0%. The negative deviations are attributed to the neglect of the crust formation. Numerical studies also reveal that droplet evaporation temperature is close to the wet-bulb temperature of the inlet gas ranging from 321.47 K to 337.85 K. Moreover, thermodynamic analysis shows that when the wastewater contains equimolar MgCl2 and CaCl2, MgCl2·6H2O first crystalizes at about d/d0 = 0.3. However, when the wastewater only contains CaCl2, CaCl2·2H2O begins to crystallize at about d/d0 = 0.25. Before crystallization, the equilibrium partial pressure of HCl is close to 0 Pa, indicating the HCl is mainly released at the particle drying stage. Further analysis suggests HCl should be mainly released from the decomposition of MgCl2·6H2O into MgOHCl.

Simple Acid Vapor Method for Production of HCl and DCl Gas for IR Spectroscopy

We report here a method that utilizes the vapor pressure of HCl(g) above a concentrated HCl(aq) solution as an extremely simple and safe method to produce small amounts of HCl vapor in an IR gas cell. This vapor pressure approach can also be used to produce DCl(g) by introducing a few drops of concentrated DCl(aq) into the gas cell.

United in Nitride: The Highly Condensed Boron Phosphorus Nitride BP3 N6.

Owing to intriguing materials properties non-metal nitrides are of special interest for both, solid-state chemistry and materials science. Mixed ternary non-metal nitrides, however, have only been sparsely investigated, as preparative chemistry lacks a systematic access, yet. Herein, we report on the highly condensed boron phosphorus nitride BP3 N6 , which was synthesized from (PNCl2 )3 , NH4 N3 and h-BN in a high-pressure high-temperature reaction. By increasing partial pressure of HCl during synthesis using NH4 Cl, single-crystals of BP3 N6 up to 80 μm in length were obtained. The unprecedented framework-type structure determined by single-crystal XRD blends structural motifs of both, α-P3 N5 and c-BN, rendering BP3 N6 a double nitride. The compound was further investigated by Rietveld refinement, EDX, temperature-dependent PXRD, FTIR and solid-state NMR spectroscopy. The formation of BP3 N6 through use of reactive precursors exemplifies an innovative access to mixed non-metal nitrides.

United in Nitride: The Highly Condensed Boron Phosphorus Nitride BP3N6

AbstractOwing to intriguing materials properties non‐metal nitrides are of special interest for both, solid‐state chemistry and materials science. Mixed ternary non‐metal nitrides, however, have only been sparsely investigated, as preparative chemistry lacks a systematic access, yet. Herein, we report on the highly condensed boron phosphorus nitride BP3N6, which was synthesized from (PNCl2)3, NH4N3 and h‐BN in a high‐pressure high‐temperature reaction. By increasing partial pressure of HCl during synthesis using NH4Cl, single‐crystals of BP3N6 up to 80 μm in length were obtained. The unprecedented framework‐type structure determined by single‐crystal XRD blends structural motifs of both, α‐P3N5 and c‐BN, rendering BP3N6 a double nitride. The compound was further investigated by Rietveld refinement, EDX, temperature‐dependent PXRD, FTIR and solid‐state NMR spectroscopy. The formation of BP3N6 through use of reactive precursors exemplifies an innovative access to mixed non‐metal nitrides.

Induction of Shiga Toxin-Encoding Prophage by Abiotic Environmental Stress in Food.

The prophage-encoded Shiga toxin is a major virulence factor in Stx-producing Escherichia coli (STEC). Toxin production and phage production are linked and occur after induction of the RecA-dependent SOS response. However, food-related stress and Stx-prophage induction have not been studied at the single-cell level. This study investigated the effects of abiotic environmental stress on stx expression by single-cell quantification of gene expression in STEC O104:H4 Δstx2::gfp::ampr In addition, the effect of stress on production of phage particles was determined. The lethality of stressors, including heat, HCl, lactic acid, hydrogen peroxide, and high hydrostatic pressure, was selected to reduce cell counts by 1 to 2 log CFU/ml. The integrity of the bacterial membrane after exposure to stress was measured by propidium iodide (PI). The fluorescent signals of green fluorescent protein (GFP) and PI were quantified by flow cytometry. The mechanism of prophage induction by stress was evaluated by relative gene expression of recA and cell morphology. Acid (pH < 3.5) and H2O2 (2.5 mM) induced the expression of stx2 in about 18% and 3% of the population, respectively. The mechanism of prophage induction by acid differs from that of induction by H2O2 H2O2 induction but not acid induction corresponded to production of infectious phage particles, upregulation of recA, and cell filamentation. Pressure (200 MPa) or heat did not induce the Stx2-encoding prophage (Stx2-prophage). Overall, the quantification method developed in this study allowed investigation of prophage induction and physiological properties at the single-cell level. H2O2 and acids mediate different pathways to induce Stx2-prophage.IMPORTANCE Induction of the Stx-prophage in STEC results in production of phage particles and Stx and thus relates to virulence as well as the transduction of virulence genes. This study developed a method for a detection of the induction of Stx-prophages at the single-cell level; membrane permeability and an indication of SOS response to environmental stress were additionally assessed. H2O2 and mitomycin C induced expression of the prophage and activated a SOS response. In contrast, HCl and lactic acid induced the Stx-prophage but not the SOS response. The lifestyle of STEC exposes the organism to intestinal and extraintestinal environments that impose oxidative and acid stress. A more thorough understanding of the influence of food processing-related stressors on Stx-prophage expression thus facilitates control of STEC in food systems by minimizing prophage induction during food production and storage.

Napelline-type C20-diterpenoid alkaloid iminiums from an aqueous extract of “fu zi”: Solvent-/base-/acid-dependent transformation and equilibration between alcohol iminium and aza acetal forms

Abstract Three new napelline-type C 20 -diterpenoid alkaloids, named aconicarmichinium A and B trifluoroacetates ( 1 and 2 ) and aconicarmichinium C chloride ( 3 ), were isolated from an aqueous extract of “fu zi”, the lateral roots of Aconitum carmichaelii . Their structures were elucidated by extensive spectroscopic data analysis. Compounds 1 – 3 represent the first examples of napelline-type C 20 -diterpenoid alkaloid alcohol iminiums, of which the structures were fully characterized. In addition, transformation and equilibration between the alcohol iminiums ( 1 – 3 ) and the aza acetals 1a – 3a were investigated by measurements of the NMR spectra in protic and aprotic deuterium solvents including alkali pyridine- d 5 , along with evaporation under reduced pressure and gradual additions of TFA, AcOH, and HCl. The results demonstrated that the transformation and equilibration were solvent-, base-, and acid-dependent. Especially, in aqueous biological fluid, these C 20 -diterpenoid alkaloids would more likely exist as the alcohol iminiums accompanied by anion counterparts in biosystems to increase their solubility, bioavailability, transportations, and functions. The absolute configurations of 1 – 3 were confirmed by X-ray crystallographic analysis of 2a .

Comparative Study of Reactive Flash Distillation vs Semibatch Reactor Technologies for the Glycerol Hydrochlorination with Gaseous HCl

The present work provides a systematic comparison of solvent-free glycerol hydrochlorination with semibatch and reactive flash distillation technologies. All the experiments were performed at atmospheric pressure and constant flow rate of gaseous HCl in the temperature range of 70 to 120 °C. Both acetic acid and adipic acid were used as homogeneous catalysts, separately, at a concentration of 12% by moles of each. In addition, a series of noncatalytic experiments was investigated. A comparative analysis between reactive flash distillation and semibatch operation suggested that reactive flash distillation only increases the production rate of the desired product 1,3-dichloropropan-2-ol (αγ-DCP) for the highest temperature, i.e. 120 °C. Many aspects of the HCl liquid uptake were also exposed once water was allowed to leave the liquid phase, revealing that water also has a positive influence on the reaction rate because it promotes HCl solubility and hydrolysis. Such an important effect was not predicted by ...

The Absorption Breakthrough Characteristics of Hydrogen Chloride Gas Mixture on Potassium-Based Solid Sorbent at High Temperature and High Pressure

In this study, the hydrogen chloride gas mixture absorption breakthrough behaviors of potassium (K)-based solid sorbents (K2CO3/Al2O3, KEPCO-RI, Korea) were studied with varying inlet HCl concentration (175–700 ppmv), temperature (200–500 °C), and pressure (1–20 bar) in a fixed-bed reactor (15 cm tall bed with 0.5 cm i.d.). The sorption capacity increases with increasing temperature and increasing pressure, whereas it was not affected by the inlet concentration. KCl crystals are formed on the sorbent surface when K+ ions from the K2CO3/Al2O3 sorbent are reacted with the Cl– ion from HCl. Its optical, physical, and chemical characterizations were examined by SEM, EDAX, BET, TGA, and XRD before and after the breakthrough tests. The main purpose of this study is to provide basic information of HCl sorption characteristics on K2CO3/Al2O3 solid sorbents for developing a high temperature and high pressure halogenide halide removal process.

The adsorption of HCl on volcanic ash

Understanding the interaction between volcanic gases and ash is important to derive gas compositions from ash leachates and to constrain the environmental impact of eruptions. Volcanic HCl could potentially damage the ozone layer, but it is unclear what fraction of HCl actually reaches the stratosphere. The adsorption of HCl on volcanic ash was therefore studied from −76 to +150 °C to simulate the behavior of HCl in the dilute parts of a volcanic plume. Finely ground synthetic glasses of andesitic, dacitic, and rhyolitic composition as well as a natural obsidian from Vulcano (Italy) served as proxies for fresh natural ash. HCl adsorption is an irreversible process and appears to increase with the total alkali content of the glass. Adsorption kinetics follow a first order law with rate constants of 2.13⋅10−6 s−1 to 1.80⋅10−4 s−1 in the temperature range investigated. For dacitic composition, the temperature and pressure dependence of adsorption can be described by the equation ln⁡c=1.26+0.27ln⁡p−715.3/T, where c is the surface concentration of adsorbed HCl in mg/m2, T is temperature in Kelvin, and p is the partial pressure of HCl in mbar. A comparison of this model with a large data set for the composition of volcanic ash suggests that adsorption of HCl from the gas phase at relatively low temperatures can quantitatively account for the majority of the observed Cl concentrations. The model implies that adsorption of HCl on ash increases with temperature, probably because of the increasing number of accessible adsorption sites. This temperature dependence is opposite to that observed for SO2, so that HCl and SO2 are fractionated by the adsorption process and the fractionation factor changes by four orders of magnitude over a temperature range of 250 K. The assumption of equal adsorption of different species is therefore not appropriate for deriving volcanic gas compositions from analyses of adsorbates on ash. However, with the experimental data provided here, the gas compositions in equilibrium with the ash surfaces can be calculated. In particular, for dacitic composition, the molar ratio of S/Cl adsorbed to the ash surface is related to the molar S/Cl ratio in the gas phase according to the equation ln⁡(S/Cl)adsorbed=2855T−1+0.28ln⁡(S/Cl)gas−11.14. Our data also show that adsorption on ash will significantly reduce the fraction of HCl reaching the stratosphere, only if the initial HCl content in the volcanic gas is low (<1 mol%). For higher initial HCl concentrations, adsorption on ash has only a minor effect. While HCl scavenging by hydrometeors may remove a considerable fraction of HCl from the eruption column, recent models suggest that this process is much less efficient than previously thought. Our experimental data therefore support the idea that the HCl loading from major explosive eruptions may indeed cause severe depletions of stratospheric ozone.

Chlorination roasting of laterite using salt chloride

This paper introduces an application of chlorination roasting process followed by hot-acidulous water leaching that could cause a high extraction selectivity of Ni, Co and Mn over Fe and Mg which can concentrate Ni and Co in laterite ores. Thermodynamic analysis of possible chlorination reactions in roasting process was calculated and the Predominance Area Diagram of Ni–Co–Cl–H–O was shown to indicate the effect of partial pressure of HCl and H2O on the stability of NiCl2 and CoCl2. The mixture of NaCl and MgCl2·6H2O was selected as chloride agent and the chlorination mechanism was discussed comprehensively. The results show that the leaching rates of Ni, Co, Mn, Fe and Mg are 87%, 58%, 53%, 3.2% and 5.4% respectively at the optimal conditions, which showed that Ni, Co and Mn could be extracted effectively and the extraction of Fe and Mg was suppressed simultaneously. The Ni/Fe ratio and Ni/Mg ratio can reach 0.97% and 0.25% in leaching solution which can increase 15 times and 8 times respectively in comparison with the Ni/Fe and Ni/Mg ratio in raw ore.

Infrared Laser Spectroscopy of the L-Shaped Cl-HCl Complex Formed in Superfluid (4)He Nanodroplets.

Chlorine atoms, generated through the thermal decomposition of Cl2, are solvated in superfluid helium nanodroplets and clustered with HCl molecules. The H-Cl stretching modes of these clusters are probed via infrared laser spectroscopy. A band centered at ∼2880.8 cm(-1) is assigned to the binary Cl-HCl complex on the basis of HCl pressure dependence and difference mass spectra. The band lies in the "free" HCl stretching region, implying that the complex is not hydrogen bound. Furthermore, the breadth of the band (∼2 cm(-1) fwhm) is consistent with an assignment to a predominantly b-type component of the H-Cl stretch, as the dominant b-type selection rules and A rotational constant allow for high energy rotational excitations that efficiently couple to droplet excitations, resulting in fast rotational deactivation. Despite the lack of rotational fine structure, which would verify the assignment, the observed band is consistent with the stabilization of a weakly bound complex having an approximately L-shaped geometry. Frequency computations for a rigid, L-shaped complex reveal that the transition dipole moment vector points almost entirely along the b inertial axis; indeed, the signal-to-noise ratio in our experiment precluded the observation of an a-type component of the HCl stretching band for the complex. No bands were observed that could be assigned to a linear H-bonded Cl-HCl complex. Additionally, we located bands that are consistent with the formation of Cl2-HCl, Cl2-(HCl)2, and Cl-(HCl)2. Two vibrations of the Cl-(HCl)2 complex were found, and harmonic frequencies and intensities computed for a cyclic structure are consistent with the observations.

A DFT based equilibrium study on the hydrolysis and the dehydration reactions of MgCl2 hydrates

Magnesium chloride hydrates are characterized as promising energy storage materials in the built-environment. During the dehydration of these materials, there are chances for the release of harmful HCl gas, which can potentially damage the material as well as the equipment. Hydrolysis reactions in magnesium chloride hydrates are subject of study for industrial applications. However, the information about the possibility of hydrolysis reaction, and its preference over dehydration in energy storage systems is still ambiguous at the operating conditions in a seasonal heat storage system. A density functional theory level study is performed to determine molecular structures, charges, and harmonic frequencies in order to identify the formation of HCl at the operating temperatures in an energy storage system. The preference of hydrolysis over dehydration is quantified by applying thermodynamic equilibrium principles by calculating Gibbs free energies of the hydrated magnesium chloride molecules. The molecular structures of the hydrates (n = 0, 1, 2, 4, and 6) of MgCl2 are investigated to understand the stability and symmetry of these molecules. The structures are found to be noncomplex with almost no meta-stable isomers, which may be related to the faster kinetics observed in the hydration of chlorides compared to sulfates. Also, the frequency spectra of these molecules are calculated, which in turn are used to calculate the changes in Gibbs free energy of dehydration and hydrolysis reactions. From these calculations, it is found that the probability for hydrolysis to occur is larger for lower hydrates. Hydrolysis occurring from the hexa-, tetra-, and di-hydrate is only possible when the temperature is increased too fast to a very high value. In the case of the mono-hydrate, hydrolysis may become favorable at high water vapor pressure and at low HCl pressure.

Synthesis of the Clathrate-I Phase Ba8−xSi46 via Redox Reactions

The clathrate-I phase Ba(8-x)Si(46) (space group Pm3̅n) was synthesized by oxidation of Ba(4)Li(2)Si(6) with gaseous HCl. Microcrystalline powders of the clathrate phase were obtained within a few minutes. The reaction temperature and the pressure of HCl were optimized to achieve good-quality crystalline products with a composition range of 1.3 < x < 1.9. The new preparation route presented here provides an alternative to the high-pressure synthesis applied so far.

Analysis and Improvement of an Experiment on Diffusion Rate of Gases Introduced in High School Chemistry Textbooks

This study is to analyze the problems observed in the experiment on ‘diffusion rate of gases’ in high school Chemistry II text books and investigate the reason followed by suggestion of an improved experimental method. As typically introduced in textbooks, a few drops of HCl(aq) and NH3(aq) were dropped at both ends of a glass tube, and then the position of ammonium chloride white ring created by the reaction with HCl(g) and NH3(g) was measured. The position of the white ring changed with time. In order to investigate the reason of such change, the experiment was repeated using HCl and NH3 gases, and the position of white ring did not changed with time. Meanwhile, the relative diffusion distance did not match with the theoretical expectation of the Graham's diffusion experiment but did with that of the Loschmidt's diffusion experiment. Based on this result experimental condition allowing equal partial pressure of HCl and NH3 gases in hydrochloric acid and aqueous ammonia solution, respectively was found, and under the obtained condition the position of white ring did not change and was consistent with the theoretical expectation. This study is anticipated to help learners to understand the scientific concept of diffusion through the improved experiment.

New Process for Producing Epichlorohydrin via Glycerol Chlorination

The strong growth of biodiesel production occurring in the last years has determined the availability of a great amount of the byproduct glycerol. Many researches in the world are therefore oriented to find new possible uses for glycerol also with the aim of reducing the cost of biodiesel. In this paper the chlorination of glycerol with gaseous hydrochloric acid to obtain 1,3-dichlorohydrin and then epichlorohydrin will be described. All the advantages of this process will be examined and discussed. The behavior of the different proposed catalysts (normally compounds containing carboxylic acid groups), the reaction kinetics, the effect of the catalyst concentration, the effect of HCl pressure, the vapor−liquid phase equilibria of the reaction products in the reaction environment, and the most convenient operative conditions have been studied, concluding with useful suggestions for the design of the industrial plants.

Oxychlorination of CO to phosgene in a three-step reaction cycle and corresponding catalytic mechanism

An improved procedure, three-step reaction cycle procedure, for the continuous preparation of phosgene from CO, air and HCl catalyzed by CuCl 2 was reported for the first time. The corresponding catalytic mechanism of each step was preliminarily disclosed with the powder X-ray diffraction (XRD) analysis: the first step is the oxychlorination of CO to phosgene and simultaneous reduction of CuCl 2 to CuCl; the second step is the oxidation of CuCl with air to Cu 2OCl 2, and the third step is the neutralization of Cu 2OCl 2 with HCl to CuCl 2. The regeneration of catalyst consists of steps 2 and 3, which is called the two-step regeneration of catalyst. The no-simultaneous existence of Cu (I) chloride and water in this three-step reaction procedure prevented effectively copper (I) chloride from the disproportionation. The influence of regeneration conditions, including reaction time, pressure of air or HCl on morphologies and recovery degree of catalyst were investigated and discussed. The degree of recovery for the single-run yield and cumulative yield of phosgene from the two-step regenerated oxychlorination agent can reach, respectively, 87.0% and 97.0% whereas the single-run yield and cumulative yield of phosgene with the one-step regenerated catalyst only can be recovered to 58.8% and 80.5%, respectively. The two-step regeneration method also can result in a higher dispersion of CuCl 2/KCl on silica gel than that of the one-step regeneration. These results not only can offer a quite promising potential for the industrial use, but also can promote our deeply understanding of this important industrial reaction.