Decomposition Of Chloride Research Articles

Corrosion of Ni-based alloy coatings prepared by laser cladding in high-temperature chloride environment

Due to the complex incineration environment of waste incineration power generation boilers generates large amounts of acidic gases (such as Cl2 and HCl) and alkali metal chlorides (such as NaCl and KCl), leading to boiler corrosion failure. Herein, a new type of NiCrAlTi alloy coatings was deposited on 304 stainless steel surfaces by laser cladding technology. High-temperature corrosion experiments were then carried out at 650 °C for 64 h and the results were compared with those of traditional Inconel625 alloy coating. The high-temperature chloride corrosion mechanism and the corrosion resistance of alloy coatings were examined. The results revealed the decomposition of chlorides, such as HCl, NaCl, and KCl into Cl2 at high temperatures as the source of corrosion of high-temperature chlorides. The released C12 reacted with the metals present in the coating to form nonprotective metal chlorides. The low melting point and high vapor pressure of metal chlorides allowed their transition into a gaseous state to diffuse outward and oxidize into Cl2. In turn, the released Cl2 reacted with the metal to induce corrosion. During the corrosion process of NiCrAlTi alloy coating, a Cr depletion zone was induced, and a continuous Al2O3/TiO2/Cr2O3 three-layer protective film was formed on the coating surface, conducive to better alleviating the corrosion caused by the reaction between Cl2 passing through the film and the metal substrate. Under the conditions of this experiment, the corrosion resistance of NiCrAlTi alloy coating is 1.8 times that of the common material 304 stainless steel, and about 1.2 times that of Incon625 alloy coating. With the extension of the experiment, its corrosion resistance will be better. Overall, rich experimental data and theoretical guidance were provided for further research and development on high-temperature chloride corrosion-resistant alloys or coating materials for high-efficiency cost-effectiveness boilers.

Effects of laser pretreatment on the formation of nanostructured carbon on the surface of chlorinated polyvinyl chloride under high-power ion beam irradiation

The features of formation of surface morphology of chlorinated polyvinyl chloride (pure and with the addition of the catalyst - ferrocene) under the influence of a high-power ion beam of nanosecond duration after the preliminary pulsed laser treatment of the polymer surface have been investigated. It was found that the morphology of the irradiated surface of chlorinated polyvinyl chloride after pulsed laser surface pretreatment differs significantly from the morphology of the irradiated surface of chlorinated polyvinyl chloride after a preliminary stationary heat treatment. For pure chlorinated polyvinyl chloride, pulsed laser pretreatment with increasing power leads to an increase in the porosity of the surface layer after high-power ion beam irradiation, whereas different surface morphologies, including fibers (including polymer fibers) of different diameters, can be obtained for the pre-stationary post-irradiation thermal treatment of this polymer. Pre-stationary thermal pretreatment of chlorinated polyvinyl chloride with the addition of ferrocene (Fe(C5H5)2) leads to a decrease in the diameter of formed carbon nanofibers (with an increase in the treatment temperature). During the pulsed laser pretreatment, an increase in the porosity of the treated layer and a slight increase in the proportion of nanofibers of larger diameter are observed. To explain the obtained differences for pulsed laser and stationary thermal pretreatment, the effect of polymer heating rate on the features of chlorinated polyvinyl chloride decomposition was analyzed.

Solid phase synthesis of alkoxyl tin and the role of alkyl for Multi-stage thermal decomposition of polyvinyl chloride

To prepare an innovative thermal stabilizer for polyvinyl chloride (PVC), the micro-nano powders of alkoxyl tin (RxOSn) were synthesized via a solid phase reaction at room temperature, using the surfactant sodium benzene sulfonate (SBS) as a catalyst. Theoretical calculation of deprotonation reaction energy of monobasic alcohol and tin chloride was performed with the framework of DFT, and their structures were characterized by XRD, SEM, FT-IR, XPS, and its surface wetting performance was carried out by contact angle (CA). Meanwhile, the multi-stage thermal stability of PVC with 10% RxOSn sample, and the role of alkyl groups (Rx, x = 2 ∼ 5) in the RxOSn/PVC were investigated. The results show that the RxOSn samples exhibit a microstructure akin to the rutile of SnO2. Multi-stage kinetic studies of exothermic reactions has confirmed that the alkoxyl wetting performance of stabilizers becomes a determining factor, while the variation in activation energy (Ea) values seems to be mainly influenced by the Rx alkyl groups in the RxOSn samples. Besides, the differences in the lattice parameter a of RxOSn were validated to have a certain impact on the stabilizing effect of PVC, and the Ea of PVC degradation is closely related to the relative value of exposed crystal surfaces (D(110)/D(101)). This series of materials is easily synthesized and can effectively enhance the thermal stability of PVC, offering a wide range of potential applications.

Theoretical Study of Platinum Doped Anatase (101) Surface on Detecting Decomposition Production of Polyvinyl Chloride

The gas sensitivity of platinum doped TiO2 (101) to two kinds on polyvinyl chloride decomposition production, CO and HCl, were explored based on density functional theory. The binding energy, adsorption distance, charge transfer, and density of states distribution were simulated and discussed. The results suggest that the O oriented mode is probably the best mode for the CO gas molecules adsorption on the Pt-TiO2 and H oriented mode for the HCl adsorption system. HCl and CO molecules obtain electrons from Pt doped TiO2 surface. At room temperature, the recovery time of CO and HCl is 1.9743 × 10-10, 1.2094 × 10-10 respectively. HCl is easier to dissociate from Pt doped TiO2 surface with a little lower energy barrier compared to CO. This work provides theoretical adsorption information of Pt-TiO2 as gas sensor material for HCl and CO detection in the application of online condition monitoring and defect diagnosis in the power cables.

Critical Role of Chlorinated Hydrocarbons in Propylene Epoxidation over K-Ag/CaCO3

Selective propylene epoxidation over K-promoted Ag/CaCO3 features promotion by surface-bound chlorine adatoms (Cl*) deposited by trace alkyl chlorides co-fed continuously in a fashion similar to ethylene epoxidation over promoted Ag/α-Al2O3 catalysts. Steady-state propylene epoxidation over K-Ag/CaCO3 in the presence of gaseous promoters (NO, CO2, and C2H5Cl) at varied contact times in flow reactors as well as transient, low-conversion batch epoxidation reveal allyl chloride, formed via propylene oxychlorination, to be a highly unstable intermediate. In situ allyl chloride formation and decomposition are in turn observed to control Cl* coverages and induce substantial bed-scale Cl* gradients during propylene epoxidation by (i) reducing Cl* coverage upstream in the catalyst bed via propylene oxychlorination and (ii) increasing downstream Cl* coverages by allyl chloride decomposition. This is supported by postreaction batch titrations of K-Ag/CaCO3 beds after steady state propylene epoxidation at varying contact times which reveals bed-average Cl* coverages increasing from ∼0.03 to ∼0.2 monolayers (moles Cl per surface Ag) with propylene conversion increasing from ∼0.05% to 2.3%. Control of Cl* coverages by in situ generated allyl chloride is highly consequential for selective epoxidation with epoxide selectivity (∼25 to 55%) and site-time yield (∼20 to 54 nmol gcat–1 s–1) increasing substantially with bed-averaged Cl* coverages as propylene conversion increases (∼0.05% to 2.3%). Results presented herein reveal a key difference in the mechanistic pathways dictating activity- and selectivity-salient Cl* coverages within propylene epoxidation compared with ethylene and 1,3-butadiene epoxidation directly related to the unique propensity of propylene to remove Cl* from Ag surfaces during epoxidation to generate allyl chloride.

PROTON-CONDUCTING MEMBRANES BASED ON MODIFIED POLYVINYLIDENE CHLORIDE

Polyvinylidene chloride was obtained by radical polymerization of vinylidene chloride and its sulfonation was carried out. When concentrated sulfuric acid is used as a sulfonating agent, the sulfonation process proceeds in the direction of dehydrochlorination of the vinylidene chloride units, and as a result, an insoluble black reaction product is formed. Therefore, sodium sulfite was chosen as the sulphurizing agent. The optimal conditions for the reaction of polyvinylidene chloride with sodium sulfite were found, while the maximum sulfur content in the modified polyvinylidene chloride, according to elemental analysis, was 3.2%. In the IR spectrum of the modified polyvinylidene chloride, the stretching vibrations of the C-Cl bond in the region of 660 cm-1 are preserved, but absorption bands appear characteristic of the sulfogroup (1250 and 1130 cm-1) and dehydrochlorinated units of polyvinylidene chloride (1630–1670 cm-1). This means that the reaction of polyvinylidene chloride with sodium sulfite is accompanied by dehydrochlorination of vinylidene chloride units. The temperature of the start of decomposition of polyvinylidene chloride containing sulfonic acid groups, according to thermogravimetric analysis, is 250 °С, which is 30 °С higher than for the original polymer. The theoretical total ion-exchange capacity of the modified polyvinylidene chloride, calculated from the sulfur content, is consistent with the experimental values and is 1.0 meq/g and is close to the similar value for the Nafion membrane. Based on polyvinylidene chloride containing sulfonic acid groups and polyvinyl alcohol, a membrane was obtained and the dependence of proton conductivity on temperature was studied. As the temperature rises from 30 °C to 80 °C, a monotonic increase in proton conductivity is observed from 6.7·10-3 S/cm to 1.8·10-2 S/cm with an activation energy of 17±1 KJ/mol. The mechanical properties of the membrane have been studied. For citation: Badanov S.V., Urumov A.V., Shaglaeva N.S. Proton-conducting membranes based on modified polyvinylidene chloride. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 3. P. 85-92. DOI: 10.6060/ivkkt.20236603.6734.

Synthesis of MnSi1.7 nanosheet bundles from CaSi2 crystal powders using MnCl2 in molten salt

MnSi1.7 nanosheet bundles with an improved homogeneous composition were synthesized by annealing from CaSi2 crystal powders with MnCl2 in molten salt. The MnSi and Si phases were formed at the initial stage of the synthesis with an inhomogeneous Mn distribution within the nanosheet bundles. Subsequently, the phases were transformed into MnSi1.7 with an improved homogeneous Mn distribution within them for 10 h annealing in the molten salt. The formation of multiple Mn-silicide phases and remarkable improvement in the structural homogeneity of the MnSi1.7 nanosheet bundles were discussed in terms of the reactions of Mn or Si with chloride compounds, decomposition of chlorides at elevated temperatures, phase selection of multiple silicide phases, shrinkage of the volume from Si to MnSi1.7, and dominant diffusion species. Multiple growth variants of the MnSi1.7 domains were stacked in the nanosheets. For comparison, the growth in a deliquescent environment realized by NH4Cl addition was examined.

Thermodynamic, pyrolytic, and kinetic investigation on the thermal decomposition of polyvinyl chloride in the presence of franklinite

Thermal co-treatment of Electric Arc Furnace Dust (EAFD) and polyvinyl chloride (PVC) may provide a viable route for reprocessing these hazardous materials within the circular economy. To develop and optimise a commercial treatment process, the complex mechanistic pathway resulting from the reaction of these two wastes must be understood. Franklinite (ZnFe2O4) is a major zinc containing phase in EAFD and to date, little work has been undertaken on the decomposition of PVC in its presence. Herein, we present a thermodynamic, pyrolytic, and kinetic study of PVC degradation in the presence of ZnFe2O4. It was found that ZnFe2O4 decomposed to its associated halides. Additionally, the kinetics data confirmed the catalytic activity of ZnFe2O4, dropping the de-hydrochlorination onset temperature of PVC from 272 to 235 °C. The distribution of the activation energy with conversion suggests the presence of several competitive reactions each with a different energy barrier. In such a case, reaction channelling can take place leading to selective zinc chlorination. Moreover, since the reduction of Fe2O3 is slow at low temperatures, it is recommended to operate at a temperature as low as 235 °C which can promote the chlorination selectivity towards zinc leaving iron bearing compounds in their stable form (Fe2O3).

Optical Properties of Hydrothermally Grown ZnO Nanoflowers

Abstract: A simple hydrothermal method has been successfully employed to synthesize flower-like ZnO nanostructure. X-ray diffraction data confirm the formation of ZnO with a Wurtzite structure. FESEM images show the flower-like morphology of the synthesized nanostructures. The energy dispersive X-ray spectroscopic analysis confirms the stoichiometric composition.. X-ray fluorescence spectrum shows no impurity element in the synthesized ZnO. The synthesized ZnO exhibits low absorption in the visible region of wavelength. Band gap enhancement was also observed owing to the quantum confinement effect. The synthesized ZnO nanoflowers exhibit strong room-temperature photoluminescence with a broad emission peak at 429 nm arising due to the recombination of electrons at zinc interstitials and holes in the valence band. This defect-related photoluminescence is very important in the context of understanding the defect dynamics in ZnO. Background: Zinc oxide (ZnO) is a well-known multifunctional material possessing unique structural, electrical, and optical properties that are very useful in various device applications. Being a high and direct band gap semiconductor, it is potentially being used in various UV light sources and detectors fabrication. However, the emission and absorption properties strongly depend on the size of the ZnO nanoparticles which in turn depends on the morphology of the nanostructure. Therefore, it is very much important to understand the structure-property relationship for a predictable device performance. Objectives: Our objective of this work is to synthesize flower-like ZnO nanostructures using a simple hydrothermal method. The flower-like ZnO morphology offers a large surface area that will be very suitable for designing gas and chemical sensor devices. Another objective of this work is to study the crystallography of ZnO. Next, the optical properties (emission and absorption) have been investigated to understand the defect-related photoluminescence mechanism. Method: A simple hydrothermal method has been deployed to synthesize flower-like ZnO nanostructures. A chloride decomposition scheme has been used to produce zinc hydroxide ions that will produce ZnO nuclide. At the onset of saturation, ZnO nanocrystals start to grow. The entire reaction was performed inside a Teflon cell stainless steel autoclave. The autoclave was placed in a horizontal tube furnace and maintained at 150 °C for 2 hr. resulting in the formation of white powder-like material. Results: The X-ray diffraction data confirm the formation of polycrystalline ZnO having a Wurtzite structure. Flower-like morphology was clearly observed in FESEM images. The EDS data confirm the composition of ZnO with proper stoichiometry. Gibb’s free energy calculation favors the reaction under the experimental condition. The absorption spectrum was used to calculate the band gap of the synthesized ZnO nanoflowers. The Tauc plot revealed the band gap of the synthesized ZnO to be~ 3.69 eV. This enhancement of band gap compared to bulk ZnO occurs due to the quantum confinement effect. The synthesized ZnO nanoflowers exhibit broad photoluminescence peaked at 429 nm owing to the presence of interstitial zinc. Conclusion: A hydrothermal method has been successfully used to synthesize well-crystalline ZnO nanoflowers of proper stoichiometry. The flower-like nanostructure exhibits band gap enhancement due to the quantum confinement effect. Room temperature visible photoluminescence was observed from the ZnO nanoflowers with a board emission peak at 429 nm. This emission arises due to the presence of deep-level zinc interstitial states. This finding will be very useful in understanding the role of defects in the visible emission from ZnO nanostructures.

Characterization of Galvanizing Flue Dust and Recycling Possibilities

Waste generation is a part of every technological process, including galvanizing. The presented paper deals with the characterization of flue dust generated in the process of hot-dip galvanizing, and proposes possible methods for zinc recycling. The flue dust is released into the atmosphere as a white fume above the zinc bath, which is caused by the decomposition of ammonium chloride and zinc chloride present in the flux. This dust is classified as hazardous waste and is a material with a particle size below 90 µm. In addition to zinc and iron compounds, it contains water vapor and oils. The presented elemental, phase, and other characteristic methods of flue dust are important for the subsequent selection of a suitable method for processing the material. At present, this waste is not processed separately due to its low production, which is approximately 0.3 kg per 1 tonne of galvanized steel. The proposed hydrometallurgical recycling method enables the processing of flue dust on a small scale and enables the recovery of high-purity zinc in the form of metallic zinc or zinc oxide.

Properties and Potential Applications of Manganese‐doped Ceria Gained by Mechanochemical Synthesis

AbstractManganese doped nanosized ceria samples were prepared by mechanochemical synthesis. Characterization was done using X‐ray diffraction (XRD), UV‐Vis diffuse reflectance spectroscopy (UV‐Vis DRS), X‐ray photoelectron spectroscopy (XPS) and others. Different conditions of synthesis were tried. Beside cerium carbonate, cerium chloride and amorphous phase remain in the product. Cerium carbonate decomposes around 250 °C, while the decomposition process centered at 330 °C was attributed to cerium chloride decomposition. Along with ceria, birnessite occurs in doped samples after thermal treatment and washing. Ceria lattice constant is reduced from 5.405 Å for pure sample to 5.401 Å for the 30 % doped sample as a consequence of manganese entrance in the ceria lattice. Ceria bandgap is significantly reduced with doping. Particle size was far greater than crystallite size due to a strong tendency toward agglomeration. All prepared powders proved to be efficient catalysts for toluene oxidation with the 30 % doped sample being the most promising.

Oxidation State and Local Structure of Chromium Ions in LaOCl.

LaOCl doped with 0–10 mol% Cr was synthesized by thermal decomposition of chlorides. X-ray diffraction (XRD) analysis revealed that incorporation of chromium results in a decrease of the lattice parameter a and a simultaneous increase of the lattice parameter c. The local structure of chromium ions was studied with X-ray photoelectron (XPS), X-ray absorption (XANES), multifrequency electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy techniques. It was determined that synthesis in oxidizing atmosphere promotes the incorporation of chromium ions predominantly in the 5+ oxidation state. Changes of chromium oxidation state and local environment occur after a subsequent treatment in reducing atmosphere. Spin-Hamiltonian (SH) parameters for a Cr5+ and two types of Cr3+ centers in LaOCl were determined from the EPR spectra simulations.

Effect of kaolinite on control of hard deposit formation and alteration of fine particles in a commercial circulating fluidized bed boiler burning solid refuse fuel

Solid refuse fuels (SRF) and biomass contain significant amounts of KCl and NaCl which result in operation problems such as hard deposit formation in combustion. The effect of kaolinite in the decomposition of mineral chlorides in a commercial SRF-burning CFBC boiler is investigated. The injection of kaolinite with SRF in a commercial CFBC shows its effect on mineral chloride decomposition thus softens the hardness of the deposit on the heat exchanger tubes in the convection pass. By the reaction of molten salt with kaolinite, particles under 5 μm in the flue gas is significantly reduced. After 37 days operation with kaolinite use the PM 10 particle in flue gas is reduced originally 86 mg/Nm3 to 16 mg/Nm3, which is 81% reduction. The reaction of physical and chemical adsorption of metallic oxide component to kaolinite particle is also monitored by SEM images. This result is reflected to the particle side distribution of the fly ash in that the shift of the abundant particle size peak to a larger size cut after the use of the kaolinite.

Mechanistic study on the role of oxygen vacancy for methylene chloride oxidation over La-Mn perovskite

Oxygen vacancy (OV) has a close relationship with chlorinated volatile organic compounds catalytic oxidation. The role of OV for methylene chloride (DCM) decomposition over defective La-Mn perovskite catalyst was investigated using Density Functional Theoretical calculations. The adsorption characteristics and dissociation processes of reactants (DCM, O2 and H2O) on perfect and defective surfaces were comparatively studied. In DCM dechlorination process, the unoccupied orbitals of OV interact with binding orbitals of Cl atoms, and thus facilitate Cl abstraction. The dissociated Cl atoms are trapped by the OV on the defective surface. The activation energy of HCl formation (144.31 kJ/mol) with the assistant of hydroxyl groups is lower than that of Cl2 formation (250.86 kJ/mol) over defective LaMnO3 surface. OV (Lewis acid) and its proximal surface hydroxyls (Lewis base) tend to form the frustrated Lewis acid-base pairs, which can capture the dissociated Cl atoms with the assistance of protons into HCl. The surface hydroxyls can be regenerated readily from H2O dissociation at OV sites, thus achieving a sustainable Cl remove. Molecular O2 is easily activated and dissociated into O atoms by OV on defective surface. The atomic O adsorbed on surface Mn sites are the primary oxygen active species for DCM deep oxidation.

One-pot green synthesis of Ag@AgCl nanoparticles with excellent photocatalytic performance

Ag@AgCl composites are effective photocatalysts used for degrading organic pollutants, but the limitations of their large-scale production hinder them from having a broad scope of applications. In this study, Ag@AgCl nanoparticles (NPs) with efficient photocatalytic performance were synthesized using a simple and straightforward strategy. Excess chloride (Cl−) ions were added into a silver nitrate (AgNO3)/N,N-dimethylacetamide solution to form [AgCl2]−. The solution of [AgCl2]− was slowly dropped into a 0.5 wt. % polyvinylpyrrolidone solution to obtain silver chloride (AgCl). Neutral silver ions (silver (0) (Ag0)) were produced by the partial decomposition of silver chloride and formed Ag@AgCl under irradiation with visible light. The experimental analysis showed that Ag@AgCl NPs had strong absorption within the range of visible light. They exhibited excellent photocatalytic activity with recyclability for the degradation of methyl orange dyes under visible-light irradiation. The photocatalyst prepared in this study can have practical application in wastewater treatment through the significant degradation of organic pollutants.

Pd doped SnO2 based room temperature operable resistive sensor for the detection of ethanol vapors

The present paper reports a highly sensitive room temperature operable ethanol vapor sensor based on the electrical properties of nanostructured Pd-doped SnO2. Pd-doped SnO2 thin films were prepared on the glass substrate (1.2 cm2) using single-step thermal decomposition of stannous chloride (SnCl2) and palladium chloride (PdCl2). The resultant films were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction spectroscopy (XRD), and UV–Vis spectroscopy. The doping of SnO2 with Pd was found to enhance the ethanol sensing response operating at room temperature. The 5% Pd-doped SnO2 sensor showed higher ethanol-sensing performance than the 0, 1, and 3% Pd-doped SnO2 with the sensing range of 10–190 ppm. The response and recovery time at 40 ppm of ethanol gas were ∼107 s and ∼378 s. The effect of Pd doping on the optical, structural properties of SnO2 and its ethanol vapor sensing behavior was studied and discussed.

Effects of boron compounds on decomposition of chlorides to control clinkers under solid refuse fuel combustion conditions

The chlorides of sodium and potassium and other mineral salts are often present in solid refuse fuel (SRF) in concentrations of at least 1–2%. These salts can generate clinker during combustion and cause serious operational problems, such as blocking of the gas passage, reduction in boiler operational efficiency, and corrosion of the heat exchanger tubes in the boiler. Although many solutions have been proposed to control clinker formation in boilers, herein we investigated the effects of boron compounds (boric acid and borax) on the decomposition of the mineral salts present in SRF to control the formation of fly ash. Using a laboratory-scale reactor, isothermal reactions between the boron compounds and the chlorides were performed at 900 °C for 10 h. HCl gas was released during the decomposition reactions, indicating that a chemical reaction had occurred on the surfaces of the boron compounds. Peaks related to sodium and potassium borates were observed in X-ray diffraction patterns, suggesting that these compounds had been formed during the reactions. Scanning electron microscopy images of the reaction products showed clusters of the mineral salts on the matrix of the borax particles, indicating that changes in the morphology owing to physical adsorption had also occurred during the reactions.

Particle formation and heat transfer in a gas-solid hydrolysis reactor with cupric chloride conversion to copper oxychloride

This paper presents a new predictive heat and mass transfer model of the gas-solid reaction in a cupric chloride decomposition and hydrolysis reactor during thermochemical water splitting in a copper-chlorine (Cu-Cl) cycle. The hydrated cupric chloride droplets descend in a narrow vessel through a reactor which forms a more coherent flow than a traditional hydrolysis spray reactor. The reactor operates based on falling solid particles and the gas-solid flow behavior in the reactor is analyzed to predict the total relative velocity of steam in its interaction with the CuCl2 (s). Aspen plus software and past literature are used for the thermodynamic and kinetic parameter evaluation. The present model reveals new physical insights into the gas/solid hydrodynamics in the hot zone of the hydrolysis reactor. From the analysis and results, the total relative velocity of steam through the height of the furnace varies from 0.32 m/s at the bottom to 0.12 m/s at the top. Furthermore, at the steam/CuCl2 molar ratio of 15 for an increase of cupric chloride volumetric flow rate from 8 ml/min into 25 ml/min, the average net heat transfer rate increases from 1.85 kW into 5.45 kW.

The study of ZnAl and ZnFe layered double hydroxide on the catalytic dechlorination and fire safety of polyvinyl chloride

The effect of OZnAl-LDH and OZnFe-LDH on the catalytic dechlorination, thermal decomposition and smoke suppression of polyvinyl chloride (PVC) during pyrolysis processes was investigated and compared. The thermal degradation and combustion behavior of the PVC composites were investigated by thermogravimetric analysis and cone calorimetry, respectively. The results indicate that the addition of LDHs brought about the improved thermal stability and reduced heat release of PVC composites at high temperature. The smoke suppression properties of the composites are investigated by steady-state tube furnace. The results revealed that the toxic gases such as CO, CH4, NOx and N2O were inhibited by both two LDHs, but the OZnAl-LDH has better effect on the smoke suppression. Subsequently, the char layer was investigated by scanning electron microscopy–energy-dispersive spectrometry and Raman analysis. The results indicated that the LDHs can promote the dechlorination of PVC and form graphitized structures. Generally, OZnAl-LDH and OZnFe-LDH can be potential catalysts for waste disposal and improve the fire safety of PVC.

Theoretical Foundations of Technology for the Production of Lithium Carbonate by the Ammonia Method

Theoretical foundations of technology for producing lithium carbonate of battery quality by the ammonia method have been developed. This technology is based on the precipitation of lithium carbonate from an aqueous solution of lithium chloride by its direct contact with a gaseous mixture of NH3 and CO2 in a 2 : 1 ratio, followed by NH3 reproduction by the decomposition of ammonium chloride with calcium hydroxide, which is a byproduct of interactions in the LiCl−NH3–CO2−H2O system. The applicability of the ammonia method for obtaining battery-quality Li2CO3 from sulfate, nitrate, and mixed lithium solutions has been shown.