Hydrogen Chloride Acid Research Articles

Processing Properties and Thermal Stability of Poly(vinyl chloride‐co‐vinyl acetate) by Experiments and Molecular Dynamics Simulations

AbstractThe effects of copolymerized monomer vinyl acetate (VAc) on processing properties and thermal stability of poly(vinyl chloride‐co‐vinyl acetate) (PVCA) are investigated via experiment and molecular dynamics simulation. Experimental results showed that PVCA with higher VAc content has larger loss tangent (tanδ), lower complex viscosity (η*), and glass transition temperature (Tg), which improved the processing properties of PVCA. A series of PVCA models are constructed to study the microstructure on the processing properties of PVCA, and the results showed the PVCA with higher VAc content exhibits larger molecular chain mobility and free volume fraction (FFV), smaller intermolecular interactions, and the mean square end‐to‐end distance (<Ree2>). Furthermore, the IR spectra of gas products indicated that thermal degradation of PVCA mainly generated hydrogen chloride (HCl), carboxylic acid, and aliphatic hydrocarbons between 200 and 500 °C, and the removal of HCl and carboxylic acid is almost simultaneous. The degradation models of PVCA chains demonstrated the CCl bond in vinyl chloride (VC) and CO bond in VAc have similar thermal stability, which corresponded to the experimental results. In a word, the work provides a promising technique to study the structure and property of PVCA at molecular dynamic level.

Modeling Hydrogen Chloride and Aluminum Surface Interactions for Spacecraft Fire Safety Applications

Experiments and modeling were performed to determine the surface kinetics of gaseous hydrogen chloride (HCl) with aluminum surfaces subjected to various treatments. HCl and other acid gases are a spacecraft fire safety concern because they are commonly found in products from electrical wire pyrolysis. Three types of aluminum surfaces were considered: surface with chromate conversion coating (iridite), anodized, and untreated. A test cell made of polytetrafluoroethylene was used to measure the difference in the HCl concentration from the inlet to the outlet. A simple one-step global surface reaction model that accounts for active surface sites was proposed. The kinetic constants were calibrated using the measured data. The calibrated model was validated against experiments with different flow rates and HCl inlet concentrations. The results showed that anodized aluminum had the most HCl uptake, followed by the iridite, and then the untreated aluminum. The amount of HCl uptake appeared to correlate well with the thickness of the oxide layer on aluminum. The relevance of these findings is discussed with respect to the design of large-scale fire safety experiments in space and various fire safety application scenarios.

Inhibition Efficiency of Eco-friendly Green Inhibitors (Ocimum tenuiflorum Phytocompounds) on Corrosion of High Carbon Steel in HCl Environment using Thermometric and Electrochemical Methods

Corrosion inhibition behavior of crude alkaloids and flavonoids extracts of Ocimum tenuiflorum roots on the corrosion of high carbon steel in hydrogen chloride acid environment was studied using thermometric, electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The phytocompounds showed excellent corrosion retardation ability on the high carbon steel metal in HCl acid environment. The alkaloids demonstrated a more reliable inhibition efficacy compared to flavonoids extracts with maximum inhibition efficiency of 98.1% and 93.6% respectively at a maximum concentration of 2.0 g/L. There was a noticeable increase in inhibition mitigation potential of the inhibitors with increasing concentration of extracts. A physical adsorption mechanism was recorded by the inhibitor and the Langmuir adsorption isotherm was well obeyed with correlation coefficient (R2) at approximately 0.999. Results of electrochemical impedance spectroscopy and potentiodynamic polarization confirmed the strong adsorption of the inhibitors on the steel surface through the values of charge transfer resistance and corrosion current densities. The inhibitors proved to be stable ones on the metal and a spontaneous reaction process was recorded from the data derived from the Gibbs free energy of adsorption.

Novel process for the exergetically efficient recycling of chlorine by gas phase electrolysis of hydrogen chloride

Due to the steadily increasing production capacities of polycarbonates and polyurethanes, the volume of hydrogen chloride (HCl), which emerges as byproduct from these processes, is experiencing a significant growth. Owing to the oversaturation of the market for HCl and hydrochloric acid, the question on how to utilize this byproduct in a sustainable and energy-efficient way is becoming more and more important. The oxidation of HCl to chlorine, which can be redirected as an educt to these above mentioned processes, offers a feasible solution to this problem and can be carried out either heterogeneously catalyzed at high temperatures or through electrolysis. Up to now, the most energy-efficient industrially employed electrochemical variant is the Bayer UHDENORA process, based on aqueous hydrochloric acid as a feed stock. The major objective of this work is to propose a novel electrochemical process utilizing HCl as a gaseous reactor feed in order to significantly reduce the electrical energy demand of the reactor combined with new and more energy-efficient subsequent separation sequences. For this purpose, flowsheet simulations of the Bayer UHDENORA process and two novel process variants based on the gas phase reactor and two different separation sequences were carried out and followed by a detailed exergy analysis. The analysis shows significant exergetic savings of up to 38% in this novel process variants compared to the Bayer UHDENORA process, including not only the electrochemical reactor but also the subsequent separation steps. The novel process therefore allows for a more sustainable and energy-efficient production of the base chemical chlorine and, contrary to the heterogeneously catalyzed high temperature process, for the utilization of electrical energy from advancing renewable sources like wind and sun.

The effect of thermal treatment on the acid neutralizing capacity of newberyite: structural assessment and kinetics of the HCl neutralization reaction

The newberyite MgHPO4·3H2O antacid activity has never been investigated before. Crystalline and heated Newberyite, at 200 °C, was tested as a neutralizing of hydrogen chloride acid (HCl 0.1 M to simulate gastric juice). Results show that the substrate has a basic behavior and may be used as an active ingredient in the antacid formulation. HCl Neutralization 0.1 M depends of newberyite concentration and pH1 was reached when 0.5 M was used. The crystalline and heated newberyite antacid power was compared with that of some commercial antacids. The newberyite heated pushed pH to 4 after 4 min when the crystalline product was brought it to 3 after 15 min. The antacid neutralizing capacity (ANC) was evaluated using direct and reverse titration methods. ANC values increased when particle sizes decreased. The heated product at 200 °C increased strongly the ANC and the maximum value reached was 13 meq/g. The kinetic study of neutralization reaction was carried out by pHmetry. The rate constants are depending of newberyite quantity and the optimal neutralization of HCl 0.1 M was obtained for 0.5 g. The resulting structural transformations have been investigated. XRD showed that the product became amorphous after heating at 200 °C. FT-IR and Raman spectroscopy agree on departure of the three crystallization water molecules, when MgHPO4·3H2O was heated. Surface area measurement was determined by Brunauer, Emmett and Teller and indicates that the product hasn’t an important porosity. Scanning electron microscopy coupled with energy dispersive spectrometry elementary analysis was also carried out and confirmed FT-IR and Raman spectroscopy results.

Acid Mist Cyclone Separation Experiment on the Hydrochloric Acid Regeneration System of a Cold Rolling Steel Plant

In the hydrochloric acid regeneration system of a cold rolling steel plant, the large amounts of hydrochloric acid droplets and iron oxide dust in the flue gas at the absorption column outlet cause serious air pollution. To reduce pollution, a high-precision cyclone separator is utilized to recycle hydrogen chloride acid mist and iron oxide dust simultaneously. The key factors of the high-precision cyclone separator, such as pressure drop, separation efficiency, and fluid density, are investigated to determine the optimal operation parameters under practical working conditions. Results show that the separation efficiency of the cyclone separator increases rapidly initially and then decreases gradually with an increase in pressure drop. Pressure drop and separation efficiency increase slightly with an increase in inlet fluid concentration. When the velocities of the inlet gas are 4.8-10 m s^(-1) and 5.0-9.2 m s^(-1), the separation efficiencies of hydrochloric acid and iron oxide are both higher than 80%. When the velocity of the inlet gas is 6.67 m s^(-1), the separation efficiencies of hydrochloric acid and iron oxide reach the highest values of 92% and 89%, respectively.

Mathematical modeling and simulations on massive hydrogen yield using functionalized nanomaterials

In this paper, we adopt the mathematical modeling and MD simulation to investigate the possibility of using functionalized nanomaterials, in particular carbon nanotubes and graphene to yield hydrogen from an acidic solution by the mean of reverse osmosis. Positively charged nanomaterials are found to be a necessary condition for such phenomenon to happen. For hydrogen chloride acid under certain external forces, only hydrogen ions could gain sufficient work done to overcome the energy barrier induced by the functionalized nanomaterials, resulting in sole hydrogen ions in the permeate side. Hydrogen could then be produced from hydrogen ions by a chemical reduction. Our numerical results indicate that for the two proposed nanomaterials, functionalized graphene turns out to be the better candidate for the current purpose.

Improvement of haze ratio of DC (direct current)-sputtered ZnO:Al thin films through HF (hydrofluoric acid) vapor texturing

The textured ZnO:Al films are used to enhance light trapping in thin film solar cells. The wet etch process is used to texture ZnO:Al films by dipping in diluted acidic solutions such as HCl (hydrogen chloride acid) or HF (hydrofluoric acid). During this process, the acidic solution can damage the glass substrate, which could then be difficult to apply for the inline mass production process since this process needs to be performed outside the chamber. In this paper we report a new technique to control the surface morphology of DC-sputtered ZnO:Al films. The ZnO:Al films are textured with vaporized HF formed by mixing the HF with an H2SiO3 solution. We achieved a high haze value of 74.6% at a 540 nm wavelength by increasing the etching time and HF concentration. A haze value of about 58% was achieved at a 800 nm wavelength when vapor texturing was used. The ZnO:Al film texture by HCl had a haze ratio of about 9.5% at 800 nm and less than 40% at 540 nm. In addition to a low haze ratio, in the texturing by HCl it was very difficult to control etching and to keep reproducibility due to its very fast etching speed.

Effect of temperature and hydrochloric acid on the intrinsic viscosity of poly(acrylic acid) in aqueous solutions

In this work, the intrinsic viscosities of poly(acrylic acid) were measured in water and aqueous hydrogen chloride solutions from (288.15 to 313.15) K. Poly(acrylic acid) are ionized in water and hence intensification of the intramolecular repulsive interactions was arising between ionized groups along the polymer chain and polymer chains were expanded. Whereas adding hydrogen chloride acid in PAA solutions suppressed the ionization of ionizable groups and PAA became as neutral polymers; therefore polymer chains were shrunk. The expansion factors of the polymer chains were calculated from the intrinsic viscosity data. The thermodynamic parameters (entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer–solvent interaction parameter and second osmotic virial coefficient) were derived by the temperature dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that aqueous hydrogen chloride solutions are changed to the good solvents for poly(acrylic acid) by increasing temperature.

Suicide With Hydrogen Sulfide

This presentation will address the recent rise of suicide deaths resulting from the asphyxiation by hydrogen sulfide (H2S) gas.Hydrogen sulfide poisoning has been an infrequently encountered cause of death in medical examiner practice. Most H2S deaths that have been reported occurred in association with industrial exposure.More recently, H2S has been seen in the commission of suicide, particularly in Japan. Scattered reports of this phenomenon have also appeared in the United States.We have recently observed 2 intentional asphyxial deaths in association with H2S. In both cases, the decedents committed suicide in their automobiles. They generated H2S by combining a sulfide-containing tree spray with toilet bowl cleaner (with an active ingredient of hydrogen chloride acid). Both death scenes prompted hazardous materials team responses because of notes attached to the victims' car windows indicating the presence of toxic gas. Autopsy findings included discoloration of lividity and an accentuation of the gray matter of the brain. Toxicology testing confirmed H2S exposure with the demonstration of high levels of thiosulfate in blood.In summary, suicide with H2S appears to be increasing in the United States.

Efficiency Improvement of Dye-Sensitized Solar Cell with Ultraviolet and Hydrogen Chloride Treatments

The porous titanium dioxide electrode plays an important role for the adsorption of dye in dye-sensitized solar cells. Two kinds of treatment used to improve the adsorption of the dye on titanium dioxide were investigated in this study. Before the dye adsorption, the titanium dioxide electrode was illuminated under ultraviolet light to result in self-cleaning by photocatalysis and then immersed in hydrogen chloride acid for surface protonation. The adsorption of dye is enhanced from Fourier-transform infrared spectrometer examination. The efficiency of dye-sensitized solar cell with the titanium dioxide electrode treated by ultraviolet light was improved from 6.29 to 6.71% and to 7.39% with both treatments.

Synthesis of Thiosemicarbazone Derivatives of Benzo-15-crown-5 and Their Anion Recognition Properties

A series of thiosemicarbazone derivatives of benzo-15-crown-5 were synthesized efficiently at room temperature using hydrogenchloride acid (HCl) as catalyst. Their anion recognition properties of a, b and c were studied, the result show they exhibit highly selective binding and sensing of F−, MeCO2 − and n-C3H7CO2 − in CH3CN (F− > n-C3H7CO2 − > MeCO2 − > > Cl−, Br− and I−). Especially receptor c shows different UV-Vis spectrum of F− from MeCO2 −and C3H7CO2 −, in addition to the color of the solution change from colorless to yellow upon the addition of F−, these two points make it suitable to be used as colorimetric anion sensor to identify fluoride anion from other halide anions and carboxylate anions by naked-eye. The connection between receptor and anion is by hydrogen bonding interactions, the binding ratio is 1:1, which have been confirmed by UV-vis inspection spectra in CH3CN and 1HMR in DMSO-d6.

The airborne lava–seawater interaction plume at Kīlauea Volcano, Hawaiʻi

Lava flows into the sea at Kīlauea Volcano, Hawaiʻi, and generates an airborne gas and aerosol plume. Water (H 2O), hydrogen chloride (HCl), carbon dioxide (CO 2), nitrogen dioxide (NO 2) and sulphur dioxide (SO 2) gases were quantified in the plume in 2004–2005, using Open Path Fourier Transform infra-red Spectroscopy. The molar abundances of these species and thermodynamic modelling are used to discuss their generation. The range in molar HCl / H 2O confirms that HCl is generated when seawater is boiled dry and magnesium salts are hydrolysed (as proposed by [T.M. Gerlach, J.L. Krumhansl, R.O. Fournier, J. Kjargaard, Acid rain from the heating and evaporation of seawater by molten lava: a new volcanic hazard, EOS (Trans. Am. Geophys. Un.) 70 (1989) 1421–1422]), in contrast to models of Na-metasomatism. Airborne droplets of boiled seawater brine form nucleii for subsequent H 2O and HCl condensation, which acidifies the droplets and liberates CO 2 gas from bicarbonate and carbonate. NO 2 is derived from the thermal decomposition of nitrates in coastal seawater, which takes place as the lava heats droplets of boiled seawater brine to 350–400 °C. SO 2 is derived from the degassing of subaerial lava flows on the coastal plain. The calculated mass flux of HCl from a moderate-sized ocean entry significantly increases the total HCl emission at Kīlauea (including magmatic sources) and is comparable to industrial HCl emitters in the United States. For larger lava ocean entries, the flux of HCl will cause intense local environmental hazards, such as high localised HCl concentrations and acid rain.

Durability of Very-Early-Strength Latex-Modified Concrete Against Freeze-Thaw and Chemicals

This study focused on the durability of very-early-strength latex-modified concrete against freeze-thaw and chemical exposure by using water absorption, freeze-thaw resistance, deicer salt scaling, and chemical resistance tests. The experimental variables were latex content (latex solids and cement as percentages) and water-cement ratio (w/c). This study examined five levels of latex content (0%, 5%, 10%, 15%, and 20%) at a constant slump and three w/c's (0.36, 0.38, and 0.40) at a constant latex content of 15%. The results were as follows: the water absorption at 15% latex content was less than 50% at 0% latex content and supported the theory of a continuous polymer film that hinders the penetration of water. Within the range of this study, both the latex-modified and nonmodified concrete exhibited good freeze-thaw performance, although the latex-modified exhibited superior properties. In both the weight loss and visual evaluations, the deicer salt scaling test indicated improved performance as the latex content increased. In the chemical resistance tests, the weight loss of latex-modified concrete decreased as the latex content increased for both sulfuric and hydrogen chloride acid exposures. However, in the calcium chloride solution test, the weight change varied from a slight gain with no latex to a slight loss at 20%.