Production Of Chloride Research Articles

Thermodynamic modeling of phases equilibrium in aqueous systems to recover potassium chloride from natural brines

Chemical fertilizers, such as potassium chloride, ammonium nitrate and other chemical products like sodium hydroxide and soda ash are produced from electrolyte solutions or brines with a high content of soluble salts. Some of these products are manufactured by fractional crystallization, when several salts are separated as solid phases with high purity (>90%). Due to the large global demand for potassium fertilizers, a good knowledge about the compositions of salts and brines is helpful to design an effective process. A thermodynamic model based on Pitzer and Harvie's model was used to predict the composition of crystallized salts after water removal by forced evaporation and cooling from multicomponent solutions or brines. Initially, the salts’ solubilities in binary systems (NaCl–H2O, KCl–H2O and MgCl2–H2O) and ternary system (KCl–MgCl2–H2O) were calculated at 20°C and compared with literature data. Next, the model was compared to our experimental data on the quinary system NaCl–KCl–MgCl2–CaCl2–H2O system at 20°C. The Pitzer and Harvie's model represented well both the binary and ternary systems. Besides, for the quinary system the fit was good for brine densities up to 1350kg/m3. The models were used to estimate the chemical composition of the solutions and salts produced by fractional crystallization and in association with material balance to respond to issues related to the production rates in a solar pond containing several salts dissolved, for instance, NaCl, KCl, MgCl2 and CaCl2.

Plantwide Scheduling Model for the Typical Polyvinyl chloride Production by Calcium Carbide Method

The polyvinyl chloride (PVC) production by calcium carbide method accounts for the majority of PVC in the market in China, the largest market share in the world. Due to high energy costs, increasingly stringent requirements on emission reduction, and intense global competition, the scheduling optimization of PVC production processes, as an effective way to improve profit, is drawing increasing attention. However, most research is only focused on the scheduling of vinyl chloride monomer (VCM) polymerization processes rather than plantwide scheduling optimization. Moreover, the majority of energy consumption lies in the upstream VCM preparation process, including calcium carbide and chlorine production processes. Therefore, plantwide scheduling optimization is of great importance for reducing the energy consumption and improving the overall profit. Hence, a discrete time representation based plantwide scheduling model is proposed in this paper. Since the operation characteristics in the time scales for VCM ...

Anti-Inflammatory Agents in Mouth-Rinses For Periodontal Treatment

Chemotherapeutic agents have been shown to be useful adjuncts to daily oral home care in the control of plaque and gingivitis. This paper reviews the main agents used in periodontology as a mouth-rinse in regards to anti inflammatory effects and other vehicles to inhibit the growth of supragingival plaque. The agents discussed are chlorhexidine, cetylpyridinium chloride, essential oils, triclosan, delmopinol, salifluor, xylitol, ketorolac and natural products. There are several in vivo and in vitro studies that evaluated the specific properties of mouth-rinses considered along with their action mechanisms, side effects, safety and possible clinical usefulness. Most of the studies have reported that chlorhexidine gluconate or essential oils provide significant anti-plaque and anti-septic benefits whereas triclosan represents unique clinical effects on reducing inflammation in addition to inhibiting the dental plaque biofilm. Although the natural products appear to be promising in reducing plaque and gingival inflammation, data on clinical effects are sparse. Mechanical plaque control is the primary tool to prevent the progression of periodontal diseases, but adjunctive usage of anti-inflammatory mouth-rinses can be necessary for certain time periods for certain category of patients. Keywords: Anti-inflammation, anti-gingivitis, anti-plaque, mouth-rinses, periodontal disease.

Prenatal phthalate exposure: epigenetic changes leading to lifelong impact on steroid formation.

Endocrine disruptors (ED) are environmental pollutants that mimic endogenous hormonal signals. Exposure to EDs during fetal and early life is a public health concern because these are periods characterized by high cellular plasticity that influence the physiology and development of disease later in life. Phthalates are plasticizers used in the industry to manufacture polyvinyl chloride products and several consumer products. Di(2-ethylhexyl) phthalate (DEHP) is one of the most produced plasticizers; it is ubiquitously found contaminating the environment, and has been shown to be an ED. Human exposure to phthalates starts during fetal development and continues after birth through contact of the newborn with the environment and contaminated food sources. We used a rat model in which pregnant dams are gavaged with DEHP from gestational day 14 until birth to study the long-term effects of DEHP. This window of fetal exposure results in decreased circulating testosterone and aldosterone levels in adult male offspring and estradiol in the female. The observed steroid changes are likely of an epigenetic origin as DEHP is rapidly cleared after birth. Here, we review the long-term effects of fetal exposure to DEHP with a focus on the molecular and epigenetic changes, including DNA methylation, which may mediate long-term endocrine dysfunction.

Effect of temperature on the methyl chloride production rate in a marine phytoplankton, Phaeodactylum tricornutum

Methyl halides such as methyl chloride (CH3Cl) are known to be important carriers of halogen from the ocean to the atmosphere, and the halogens they release into the stratosphere by photolysis catalyze ozone depletion. Marine phytoplankton have been reported as a source of CH3Cl, but the effects of environmental temperature on the CH3Cl production by phytoplankton have not been investigated. In this study, we investigated the effects of temperature on the production of CH3Cl in the culture of a marine diatom, Phaeodactylum tricornutum CCMP 630, incubated at 10, 15, 20, 25, and 30 °C. CH3Cl concentrations in cultured samples were determined using purge and trap gas chromatograph–mass spectrometry. Phytoplankton growth was monitored by measuring the chlorophyll a concentrations. CH3Cl production was observed for several weeks at four different temperatures ranging from 10 to 25 °C. The CH3Cl production from P. tricornutum was increased with increasing temperature from 10 to 25 °C, and the maximum production rate for CH3Cl was 0.21~0.26 μmol (g chlorophyll a)−1 d−1 at 25 °C, which was several times higher than that at 10 °C (~0.03 μmol (g chlorophyll a)−1 d−1). The Arrhenius equation was successfully used to characterize the effects of temperature on the production rates of CH3Cl in the culture of P. tricornutum. Our results suggest that water temperature directly affects CH3Cl production derived from P. tricornutum and that water temperature would be a significant factor for estimating the emissions of CH3Cl from marine environments.

Concentration effects on biotic and abiotic processes in the removal of 1,1,2-trichloroethane and vinyl chloride using carbon-amended ZVI

A permeable reactive barrier, consisting of both zero valent iron (ZVI) and a biodegradable organic carbon, was evaluated for the remediation of 1,1,2-trichloroethane (1,1,2-TCA) contaminated groundwater. During an 888day laboratory column study, degradation rates initially stabilized with a degradation half-life of 4.4±0.4days. Based on the accumulation of vinyl chloride (VC) and limited production of 1,1-dichloroethene (1,1-DCE) and 1,2-dichloroethane (1,2-DCA), the dominant degradation pathway was likely abiotic dichloroelimination to form VC. Degradation of VC was not observed based on the accumulation of VC and limited ethene production.After a step reduction in the influent concentration of 1,1,2-TCA from 170±20mgL−1 to 39±11mgL−1, the degradation half-life decreased 5-fold to 0.83±0.17days. The isotopic enrichment factor of 1,1,2-TCA also changed after the step reduction from −14.6±0.7‰ to −0.72±0.12‰, suggesting a possible change in the degradation mechanism from abiotic reductive degradation to biodegradation. Microbiological data suggested a co-culture of Desulfitobacterium and Dehalococcoides was responsible for the biodegradation of 1,1,2-TCA to ethene.

Kinetic modeling of 1,2‐dichloropropane (PDC) free‐radical chlorination

Recent government mandates have lowered the permissible global warming potential (GWP) for refrigerants in mobile air conditioning substantially below that of the hydrofluorocarbon products that are used currently. Potential replacements, hydrofluoro‐olefins (HFO), have a reduced impact on the ozone layer and lower GWP. Many desirable HFO compounds, such as HFO‐1234yf, can be produced utilizing chlorocarbons as feedstocks such as the preferred 1,1,2,3‐tetrachloropropene (TCPE). TCPE can be produced by several routes; however, producing TCPE from 1,2‐dichloropropane (PDC) is potentially more desirable environmentally and economically since PDC is a byproduct of propylene oxide and allyl chloride production. One process option is to convert PDC to pentachloropropane (PCP) intermediates by chlorination, followed by dehydrochlorination of the PCPs to produce TCPE. In this work, we show that PCPs can be produced through the chlorination of PDC in a free‐radical liquid phase reaction and have developed a kinetic model for PDC chlorination based on the relevant free radical elementary reactions. Thermodynamic properties including standard heats of formation, standard entropies of formation, and heat capacities for the radical and non‐radical species were estimated by using ab initio and COSMOtherm calculations and validated against available experimental data. The reaction equilibrium constants were determined from the Gibb's free energies of the reactants and products. Phase equilibria were calculated by means of a consistent set of thermodynamic properties of the species. In addition, physical properties such as the vapor pressure of pure components involved in the reaction network were also estimated. Ab initio transition state calculations were employed to estimate the rate parameters including pre‐exponential factors and activation energies for the relevant reactions. The activation energies of some key reactions were then adjusted to match experimental data. The resulting kinetic model provided a basis for process yield optimization and scale up. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1174–1191, 2016

ChemInform Abstract: Discovery, Development, and Commercialization of Gold Catalysts for Acetylene Hydrochlorination

AbstractReview: 38 refs.

Production of Ethylene from Natural Gas via Synthesis of Methyl Chloride followed by its Pyrolysis: Improvement of the Selectivity by Adding the Stage of Hydrodechlorination of Methane Polychlorides

An effective catalyst for synthesis of ethylene at the stage of hydrodechlorination of methylene chloride and chloroform was chosen through comparative studies of alumina-supported palladium, nickel-molybdenum and nickel-lanthanum-magnesium catalysts. A flow reactor with the fixed catalyst bed was used for the studies at 300 ・・C, 3,8 s contact time, molar ratio of hydrogen to methylene chloride equal to 3 : 1. The nickel-molybdenum catalyst was shown the best. The process flow sheet was improved in order to favor preferable synthesis of ethylene to be used for production of vinyl chloride: Ethylene was proposed to synthesize during an additional stage of pyrolysis of methane homologues which were extracted from natural gas and from reaction gas of methyl chloride pyrolysis, as well as at the stage of hydrodechlorinaiton of methane polychlorides.

Reductive Chlorination and Bromination of Ketones via Trityl Hydrazones.

A method is presented for the direct transformation of a ketone to the corresponding reduced alkyl chloride or bromide. The process involves the reaction of a ketone trityl hydrazone with tBuOCl to give a diazene which readily collapses to the α-chlorocarbinyl radical, reduction of which by a hydrogen atom source gives the alkyl chloride product. The use of N-bromosuccinimide provides the corresponding alkyl bromide. This unique transformation provides a reductive halogenation that complements Barton's redox-neutral vinyl halide synthesis.

Reductive Chlorination and Bromination of Ketones via Trityl Hydrazones

AbstractA method is presented for the direct transformation of a ketone to the corresponding reduced alkyl chloride or bromide. The process involves the reaction of a ketone trityl hydrazone with tBuOCl to give a diazene which readily collapses to the α‐chlorocarbinyl radical, reduction of which by a hydrogen atom source gives the alkyl chloride product. The use of N‐bromosuccinimide provides the corresponding alkyl bromide. This unique transformation provides a reductive halogenation that complements Barton's redox‐neutral vinyl halide synthesis.

Weaning China Off Mercury

A team of Japanese researchers discovered high concentrations of mercury at the peak of Mount Fuji in 2013. After further research, they identified the source as China, from which winds had carried the toxic metal hundreds of miles into Japan. The discovery offered a stark illustration of how much mercury floats in the air above China. Much of China’s mercury emissions originate from coal-fired power plants, but another major culprit is its chemical industry. Every year, Chinese industry consumes thousands of metric tons of mercury-based catalysts to harness coal as a raw material for the production of polyvinyl chloride (PVC), a basic plastic. In theory, the mercury should be recovered from spent catalysts, but instead, a lot of it escapes into the environment, harming workers, contaminating crops, and perhaps traveling to Japan. Given China’s abundance of low-cost coal, mercury use by the PVC industry has long seemed to be an

Human biomonitoring of bisphenol A exposure in an Austrian population

AbstractBisphenol A (BPA) is an industrial chemical widely used as a monomer in polycarbonate, epoxy resin and thermal paper production, and as a stabiliser in polyvinyl chloride (PVC) production. Thus, BPA is present in a wide range of common consumer products. Due to contact with BPA-containing products, humans are regularly exposed via different routes. BPA is an endocrine active substance and can potentially lead to different adverse health outcomes. In the present study, total BPA levels were analysed by on-line SPE-HPLC-MS/MS in spontaneous urine samples in order to investigate the exposure to an Austrian population aged 6-15 and 18-81 years. In the total study population (n=594), total BPA were found in 15.7% of all samples, with concentrations up to 17 μg/l (median: n.d., 95th percentile: 3.7 μg/l). These results show generally low BPA levels among the investigated study population. However, children and adolescents exhibited higher exposure levels. Daily BPA intakes were estimated and compared to acceptable exposure levels, whereat no exceedances could be identified. Although BPA exposure was shown to be low in the Austrian population, the wide distribution and the ongoing discussion related to possible negative health effects even at low doses indicate need for further monitoring and investigations.

Purification of Food-grade Magnesium Chloride

The application of the varying weights of bischofite dissolved in the distilled water was investigated. The effects of the temperature on the rate of evaporation and the thermal precipitation time on the purity of the crystal products were fully investigated. Two validation tests including magnifying tests and recycling residue were also studied. Our results demonstrate that the contents of NaCl, KCl and CaSO4in the filtrate reached a minimum value after the pretreatment of 350 g bischofite dissolved in 100 mldistilled water. In the crystal products from the second evaporating stage of the validation tests, the contents of MgCl2·6H2O, SO4 and NaCl+KCl are 99%, ≤0.1±0.01%and ≤0.8±0.04%, respectively. The content of magnesium chloride in the solution was increased to a greater extent, and the impurities reduced correspondingly through thedissolution pretreatments of bischofite. This could decrease energy consumption for the impurity removing stage, evaporation and crystallization process, and thus reduce costs for the industrial production of food-grade magnesium chloride

Development and characterization of non-standard extruded poly(vinyl chloride) product

This research work focuses on the development of extrusion of non-standard PVC pipe and characterization of the obtained product. The extrusion technology and poly (vinil chloride) polymer are described in shortest. Non-standard extruded PVC pipes were developed in three phases. Characterization of the non-standard extruded PVC pipes includes testing of non- standard properties, standard PVC pipes characteristics and additional properties. Non-standard properties include specific dimensional (non-standard outside diameter and inside diameter), hydraulical (hydraulic burst pressure in a short period of time in water-air and water-water experiments) and mechanical (external radial compressive force and internal tensile radial strength) characteristics. The standard extruded PVC pipes characteristics were, also, determined (density, visual appearance, Vicat softening temperature, dimensional longitudinal stability and resistance to external blows and to dichloro methane). Additional tested properties are resistance to severe external blows, dimensional radial stability, impact resistance and hardness. Deliberately produced damage has no negative effect on pipes' hydraulic and mechanical characteristics. Based on presented results concerning the non-standard, standard and additional properties and deliberately produced damage, it is concluded that a high.

High Temperature Chlorosilane Corrosion of AISI 316L

Chlorosilanes are used at high temperatures throughout the world's semiconductor industries primarily as a way to refine and deposit silicon and silicon containing materials. They are most prevalent in the manufacture of solar grade polycrystalline silicon; an industry that has historically used high cost alloys to effectively handle corrosive chlorosilane species. This study focused on understanding the corrosion behaviors of AISI 316L stainless steel, a low cost alloy, in chlorosilane environments at a variety of industrially-relevant times (0–200 hours), temperatures (500–700°C), and hydrogen chloride (HCl) mole fractions (0.0–0.06). It was observed that AISI 316L can form either predominately metal chloride or metal silicide corrosion products depending on the mole fraction of HCl. Increasing temperatures tend to favor metal silicide formation, a trend predicted by thermodynamically generated predominance diagrams. Additionally, metal silicide surface layer growth appears to be diffusion controlled with an apparent parabolic rate at long times and high temperatures. There is also evidence for reaction-limited iron silicide formation at lower temperatures. Improved understanding of metals in high-temperature chlorosilane environments will help guide materials selection processes, and ultimately facilitate cost-competitive deployment of silicon-based photovoltaic systems.

Mechanical, flammability, and thermal properties of polyvinyl chloride‐wood composites with carbide slag

Carbide slag, an industrial waste produced by calcium carbide hydrolysis to prepare C2H2 gas, was successfully used as inorganic filler in the production of polyvinyl chloride (PVC)‐wood composites. carbide slag had an average diameter of 8.1 μm which thermally decomposed at about 450°C, and its main component was Ca(OH)2. Incorporating carbide slag into PVC‐wood composites substantially decreased the flexural, tensile, and impact strength of the composites as a result of the poor interfacial adhesion between carbide slag and PVC matrix, which could be evidently observed from the scanning electron microscopy (SEM) study. To give carbide slag better use, silane coupling agent KH570 were chose to modify carbide slag. The results indicated that adding carbide slag modified by KH570 (MCS) into PVC‐wood composites could significantly improve its notched impact strength and flexural modulus. The thermogravimetric analysis (TGA) data showed that with the addition of MCS, composite had better thermal stability. It also turned out that with the addition of MCS, its smoke suppression property and flammability were enhanced effectively. To ensure sufficient properties of PVC‐wood composites, the optimal adding content of MCS was 20 phr and it leaded to remarkable performance (its flexural modulus was 3.4 GPa, notched impact strength was 3.87 KJ/m2, limiting oxygen index value was 41.5% and smoke density ranting was 55.1%), all of which endowed PVC‐wood composites better utilization. All the results indicated that the preparation of PVC‐wood composites with carbide slag could resolve environmental pollution, reuse carbide slag in different fields, and provide a new method for resource utilization of carbide slag. POLYM. COMPOS., 38:2898–2906, 2017. © 2015 Society of Plastics Engineers

Perfluoroalkyl Acids Inhibit Reductive Dechlorination of Trichloroethene by Repressing Dehalococcoides

The subsurface recalcitrance of perfluoroalkyl acids (PFAAs) derived from aqueous film-forming foams could have adverse impacts on the microbiological processes used for the bioremediation of co-mingled chlorinated solvents such as trichloroethene (TCE). Here, we show that reductive dechlorination by a methanogenic, mixed culture was significantly inhibited when exposed to concentrations representative of PFAA source zones (>66 mg/L total of 11 PFAA analytes, 6 mg/L each). TCE dechlorination, cis-dichloroethene and vinyl chloride production and dechlorination, and ethene generation were all inhibited at these PFAA concentrations. Phylogenetic analysis revealed that the abundances of 65% of the operational taxonomic units (OTUs) changed significantly when grown in the presence of PFAAs, although repression or enhancement resulting from PFAA exposure did not correlate with putative function or phylogeny. Notably, there was significant repression of Dehalococcoides (8-fold decrease in abundance) coupled with a corresponding enhancement of methane-generating Archaea (a 9-fold increase). Growth and dechlorination by axenic cultures of Dehalococcoides mccartyi strain 195 were similarly repressed under these conditions, confirming an inhibitory response of this pivotal genus to PFAA presence. These results suggest that chlorinated solvent bioattenuation rates could be impeded in subsurface environments near PFAA source zones.

Relationship between housing characteristics, lifestyle factors and phthalates exposure: the first Korean National Environmental Health Survey (2009-2011).

Background Phthalates, the esters of phthalic acid, are widely used as plasticizers in many consumer products. Phthalate plasticizers are mainly used in the polyvinyl Chloride (PVC) products including plastic containers, toys, or flooring materials, and comprise 10 to 60 % of plastic products by weight [1]. Phthalates are also utilized as solvents of cosmetics, liquid soaps, or pesticides. About 6 million tons of phthalates were produced worldwide in 2004, of which Di (2-ethylhexyl) phthalate (DEHP) accounted for half of the entire production [2]. Phthalates are easily released from products into the environment or food by leaching, migration, evaporation or natural degradation [3]. Most phthalates are absorbed through ingestion, while low molecular weight phthalates such as Dibutyl Phthalate (DBP) can be absorbed by dermal exposure or inhalation [4]. Once absorbed, phthalates usually undergo a phase I hydrolysis to form the primary metabolites such as Mono-2-ethylhexyl phthalate (MEHP) or Mono-n-butyl phthalate (MnBP), and may proceed to further hydroxylation and oxidation or phase II conjugation before they are excreted in urine and feces [5]. Since most metabolites are excreted through urine, the urinary metabolites of phthalates are useful indices for the evaluation of phthalate exposure. MnBP, the primary metabolite of DBP, could be an appropriate biomarker for DBP exposure, since 84 % of absorbed DBP is excreted as MnBP in urine within 24 h of intake [6]. As to DEHP, secondary metabolites such as Mono (2-ethyl-5-oxohexyl) phthalate (MEOHP) and Mono (2-ethyl-5-hydroxylhexyl) phthalate (MEHHP) have been used to predict DEHP exposure [7, 8]. Many investigations have been performed regarding in vivo effects of phthalate exposure since 1970s. An animal study reported testicular atrophy and decrease of reproductive ability in mice exposed to phthalates [9]. An epidemiologic study of human indicated that exposure to phthalates in male during gestation and infancy is related to the decrease of anogenital index and testosterone levels suggesting a possible anti-androgenic effect [10]. Thus, the exposure in pregnant or lactating women and boys has been considered relatively important. However, endocrine disrupting effects of phthalates in adults also have been reported in recent studies. One study showed that phthalate exposure and testosterone levels are negatively correlated in male and female adults aged over 40 years [11]. Other study has suggested that it not only affected reproductive function, but also influenced on insulin-resistance and obesity [12]. Moreover, several studies showed that the prevalence of diseases such as asthma or ADHD has a positive correlation with phthalate exposure and relevant research is still ongoing [13–15]. The effect of phthalates on the human body is not fully investigated yet and the mechanisms involved also remain unclear. There are various products containing phthalates and most people are exposed to these products in daily living. Especially, the inside structures of a building such as flooring materials, wall paper, or window frames are thought to be important sources of phthalate exposure. Larsson et al. reported higher urinary concentrations of * Correspondence: kimdh@paik.ac.kr Department of Occupational and Environmental Medicine, Inje University Haeundae Paik Hospital, 875 Heaundae-ro, Haeundae-Gu, Busan 612-862, South Korea Full list of author information is available at the end of the article

Discovery, Development, and Commercialization of Gold Catalysts for Acetylene Hydrochlorination.

Vinyl chloride monomer (VCM) is a major chemical intermediate for the manufacture of polyvinyl chloride (PVC), which is the third most important polymer in use today. Hydrochlorination of acetylene is a major route for the production of vinyl chloride, since production of the monomer is based in regions of the world where coal is abundant. Until now, mercuric chloride supported on carbon is used as the catalyst in the commercial process, and this exhibits severe problems associated with catalyst lifetime and mercury loss. It has been known for over 30 years that gold is a superior catalyst, but it is only now that it is being commercialized. In this Perspective we discuss the use and disadvantages of the mercury catalyst and the advent of the gold catalysts for this important reaction. The nature of the active site and the possible reaction mechanism are discussed. Recent advances in the design and preparation of active gold catalysts containing ultralow levels of gold are described. In the final part, a view to the future of this chemistry will be discussed as well as the possible avenues for the commercial potential of gold catalysis.