Formation Of Hydrogen Chloride Research Articles

HYDROGENATION OF SILICON, ALUMINUM AND CHLORINE AS CONSTITUENTS OF TARFAYA OIL SHALE (MOROCCO) AT 550°C AND 750°C

The formation of hydrogen chloride as well as silicon hydrides and aluminum hydrides called silanes and alanes respectively are formed when oil shale are thermally treated with hydrogen. These elements are part of the constituents of this oil shale. This work was carried out by a thermobalance (Red Croft) in the dynamic regime for thermal hydrogenation at 550°C and 750°C. The quantitative identification of the elements was done by X-ray diffraction using a dispersive method, a technique that is coupled to the scanning microscope. This work being the continuation of the one already carried out at a temperature of 550°C (A.Attaoui and M. Hafid: 2022), we have extended this to higher temperatures where we have decompositions in addition to kerogen as well as mineral matter. Studies comparing the thermal decomposition of oil shale and kerogen have shown that the mineral matter in oil shale provides surfaces capable of cracking high molecular weight products by thermal or catalytic mechanisms (A.K. Burnham, A. K and J.A.Happe: 1984). These studies indicate that reactions involving the cleavage of carbon-carbon bonds and carbon-hydrogen bonds on mineral surfaces (R.A.Regtop et al: 1985). These authors demonstrated that the carbonized residue in spent shale can increase the magnitude of secondary reactions.

Insights into the HCl formation and volatilization mechanism from organochlorine in coal: A DFT study

The elimination of hydrogen chloride (HCl) in flue gas is crucial for pollutants control and equipment safe operation in coal-fired power plant. However, the evolution and volatilization mechanism of organochlorine (Clorg) in coal to flue gas HCl during coal combustion is currently ambiguous. To solve this issue, organochlorine existing forms in various possible circumstances upon coal molecule are constructed using cluster models. Based on these models, the reaction paths, the thermodynamic and kinetic parameters of HCl generation reactions are explored deeply by DFT. To explore the HCl volatilization mechanism, the natural binding of generated HCl with distinct chemical groups in coal is studied with the examination of binding energy, electron density difference, and interaction region indicator, etc. The volatilization order of HCl at different active site is discussed by the ab initio molecular dynamics. The results show that methyl chloride is the most stable occurrence form of Clorg, and most Clorg in coal could be converted to HCl with moderate energy barriers within 100 kJ/mol. Different active sites inside coal possess various affinity for HCl that arises from their diverse bonding types of van der Waals interaction, hydrogen bond, and chemical bond. The combination of binding analysis and AIMD analysis indicates that the chemical groups on the coal surface such as oxygen-containing groups, thiophene sulfur, and pyridine nitrogen enhance the affinity of coal to HCl, causing an increase of the HCl volatilization temperature from 300 to 400 K to 700–800 K, thus impelling the HCl release characteristics complex in coal combustion process.

Controllable synthesis of a carbonaceous pitch from molecular dimension by a novel method of chlorination-dechlorination

• Controllable synthesis of a carbonaceous pitch by chlorination–dechlorination. • The properties of carbonaceous pitch derived from CLR were studied. • The mechanism of chlorination–dechlorination was revealed. • The linear and cross-linked structure was obtained by chlorination–dechlorination. • The energy changes for different chlorination routes were calculated. The carbonaceous pitch derived from coal liquefaction residue was controllably synthesized from the molecular dimension with a novel method, chlorination–dechlorination. The factors affecting the qualities of chlorination–dechlorination derived pitch, including chlorine ratios, were studied. The qualities of the pitches prepared with chlorination–dechlorination and the conventional thermal condensation method are compared. The carbons in the prepared carbonaceous pitch mainly exist in aromatic structures, which are oligomerized to transform dimers and trimers by chlorination–dechlorination. The C/H ratio, average molecular weight, and carbon aromaticity are increased by chlorination–dechlorination. According to the result of the simulation, the hydrogen atoms on the side chain of aromatic compounds are easier to be mono-substituted by chlorine atoms during chlorination, and then the substituting chlorine atoms connect with other hydrogen atoms to form to escape out of the reactor in the formation of hydrogen chloride during dechlorination, making the aromatic compounds oligomerize with each other. Thus, the conclusion that the chlorinated pitch has a more linear and cross-linking molecular structure is demonstrated, which is also confirmed by the results of 13 C NMR. The pitch precursors exhibit better thermal stability and thermochemical property even when the softening point has been raised to around 230 ℃ owing to the linear and cross-linking molecular structure. In addition, the pitches synthesized by the method of chlorination–dechlorination shows a more homogeneous state, while the pitch produced by thermal condensation contains a small number of powdery coke particles, and they also possess more excellent spinnability and appropriate viscosity for the process of melt-spinning. Chlorination–dechlorination can be used to achieve the controllable synthesis of the carbonaceous pitch from the molecular dimension. The properties of derived pitches are better as the addition of chlorine increases.

Is Weak Acid Beneficial for Addressing Checkpoint Inhibitor-Triggered Cancer Hyper Progression in Anti-PD1/PD-L1 Immunotherapies?

Numerous cases of checkpoint inhibitor–triggered cancer hyperprogression have been documented. A previous hypothesis attributes cancer onset to the local buildup of hydrogen chloride, jointly mediated by hydrogen bond donors and acceptors and basic amino acids. The anti-PD1/PD-L1 immunotherapies may have caused a surge of protons or chloride ions for the effective treatment of neoplasm, thus giving rise to the local formation of hydrogen chloride and subsequently cancer hyperprogression in some susceptible individuals. It was postulated that the local strength of acidity is critical for tumor growth and metastasis, as the intake of weak organic acids reduces cancer risks. The anti-PD1/PD-L1 immunotherapies can be integrated with weak organic acids to reduce adverse reactions and generate better anticancer outcomes.

Controlling generation of benzenes and polycyclic aromatic hydrocarbons in thermolysis of polyvinyl chloride in CO2

This study emphasizes the control of benzene derivatives and polycyclic aromatic hydrocarbons (PAHs) in thermolysis of polyvinyl chloride (PVC) using CO2. To this end, the generation of benzenes and PAHs from the thermolysis of PVC in N2 was characterized and all experimental findings from the thermolysis of PVC in N2 were used as the reference value to configure the role of CO2 in the thermolysis of PVC. The formation of hydrogen chloride (HCl) followed by the subsequent dechlorination in the thermolysis of PVC in N2 resulted in the high yield of charring compounds, providing a favorable condition for forming benzene derivatives and PAHs. However, the thermal degradation of PVC in CO2 showed the genuine thermal degradation patterns. For instance, despite the presence of the source for oxygen, the formation of CO at temperatures higher than 600 °C was observed in the thermolysis of PVC in CO2, suggesting that some unknown reactions between hydrocarbons from the thermolysis of PVC and CO2 are initiated to form CO. In addition to these unknown reactions, the enhanced thermal cracking induced by CO2 was observed. Two identified roles of CO2 during the thermolysis of CO2 was only limited at temperatures higher than 600 °C. However, despite no precise description for the mechanistic role of CO2 at this stage of study, the formation of benzene derivatives and PAHs was effectively controlled in the presence of CO2 at temperatures higher than 480 °C. Thus, these empirical findings in this study are necessary to further be investigated in the future, which offers a great venue offering a new means for modifying and/or controlling the harmful chemical species.

Inhibition of C[sbnd]Cl formation during the combustion of MSW gasification syngas: An experimental study on the synergism and competition between oxidation and chlorination

For the safe disposal of MSW, a four-step gasification-combustion conversion process is proposed in this work, consisting of material gasification, ash melting, syngas conversion and combustion. Based on the control method of dioxin in gasification process which has been studied previously, experiments of tar chlorination process under oxidative atmospheres were carried out in a homogeneous flow reaction system, using benzene as the tar model compound, to find a way for the inhibition of CCl formation during the syngas combustion process. Results indicated that Cl2 reacts with benzene more easily than O2 under low temperatures, and has a positive effect on both oxidative cracking and polymerization. For chlorination reactions, high temperature enhances the chlorination degree and leads to the formation of perchlorinated hydrocarbons, but also promotes the rupture of the weak CCl bonds. With the rise of temperature, hexachlorobenzene became the major product, the amounts of all chlorinated hydrocarbons decreased rapidly, and the conversion direction depended on the amount of O2. O2 generally promotes the formation of hydrogen chloride, and inhibits the chlorination of hydrocarbons. At a temperature above 900 °C, the total amount of chlorinated hydrocarbons was very low under oxidative atmospheres, even only with a equivalence ratio of 0.2. However, during the oxidation process under low temperatures, CCl can also be formed on cyclopentadienyl and 1,3-butadienyl radicals, whose chlorination products were observed. The synergistic and competitive effects between oxidation and chlorination are concluded and the major benzene conversion pathways are summarized according to the products detected.

Dehydrochlorination of PVC Compositions During Thermal Degradation

The polyvinylchloride (PVC) differs from other polymer materials by low thermostability. The process of dehydrochlorination takes place even at low temperatures. The purpose of this investigation was to<br />determine the influence of different PVC additives on formation of hydrogen chloride (HCl) from thermal degradation in different gaseous fluids. It has been established that the HCl formation takes place more in<br />nitrogen as a medium than in air medium at a given temperature, especially for the high temperature region. Dibutyl phthalate (as a plasticizer) in 25 mass % w.r.t. PVC, reduces the mass loss due to HCl<br />formation by about 5%, which is the result of two interaction processes - between HCl and plastifier degradation products. It has been found that the addition of 5 mass % of stabilizer in PVC slows down the<br />process of dehydrochlorination and as a result the loss of mass is 2-5% less, compared to non-stabilized samples. Calcium carbonate as a filler was found to be active above 400-500 °C and reduction in mass loss<br />was found to be up to 15% at a temperature range of 800-900 °C. Calculation of kinetic parameters shows that the rate of dehydrochlorination depends on the composition of PVC. The activation energy of formation of HCl in air, in a temperature range of 400-600°C has been found to be 12.7, 13.3, 16.1 kJ/mol for pure, plasticized and stabilized PVC, respectively. The results reported here shall be useful for development of methods for waste utilization and their influence on the environment.

1-4.石炭の昇温熱分解過程における塩化水素の発生挙動に及ぼす支配因子((1)石炭熱分解・コークス,Session 1 石炭・重質油等)

1-4.石炭の昇温熱分解過程における塩化水素の発生挙動に及ぼす支配因子((1)石炭熱分解・コークス,Session 1 石炭・重質油等)

Thermal degradation of sucralose: a combination of analytical methods to determine stability and chlorinated byproducts.

In the late years, much attention has been brought to the scientific community regarding the safety of sucralose and its industrial applications. Although it is the most used artificial sweetener in foods and pharmaceuticals, many questions still arise on its potential to form chlorinated byproducts in high temperatures, as demonstrated by several recent studies. In the present contribution, we use a combination of differential scanning calorimetry and thermogravimetric analysis coupled with infrared spectroscopy (DSC/TGA/IR), Hot-stage microscopy (HSM) and high-resolution mass spectrometry (HRMS) on samples submitted to water bath at mild temperatures to evaluate a broad spectrum of hazardous compounds formed in the degradation of this product. TGA/IR has revealed that there is effective decomposition in form of CO2 along with the formation of hydrogen chloride and other minor compounds. HSM results have provided accurate information, where the melting of the crystals was observed, followed by decomposition. Chlorinated derivatives, including polychlorinated aromatic hydrocarbons (PCAHs) were also confirmed by HRMS. These findings not only corroborate the suspected instability of sucralose to high temperatures, but also indicate that even exposed to mild conditions the formation of hazardous polychlorinated compounds is observed.

Chlorination of Benzylic and Allylic Alcohols with Trimethylsilyl Chloride Enhanced by Natural Sodium Montmorillonite

A new and practical method for the efficient chlorination of tertiary, secondary, and primary benzylic and allylic alcohols is described. The method is characterized by the formation of hydrogen chloride from trimethylsilyl chloride and trace water, the formation of a carbenium ion through the protonation of an alcohol and subsequent dehydration, and the chlorination of the carbenium ion. During the process, sodium ion-exchanged montmorillonite plays a crucial role in capturing the generated hydrogen chloride, stabilizing the carbenium intermediate as well as promoting the chlorination.

Experimental study of the heterogeneous reactivity between atomic chlorine and palmitic acid films

The present study focuses on the heterogeneous reaction between gaseous atomic chlorine and solid palmitic acid films, used as a proxy of the fatty acids detected in atmospheric airborne particles. This reaction is investigated in a coated wall flow tube reactor coupled to a molecular beam mass spectrometer. The reactive surfaces were prepared by coating the inner surface of the reactor. The initial Cl˙ and Cl2 uptake coefficient measured for these heterogeneous reactions is found to be fast: γoCl = 0.07. The rapid formation of hydrogen chloride corresponding with the disappearance of atomic chlorine is highlighted. Furthermore, the formation of new chlorinated species on the solid substrate has been detected by TOF SIMS analysis leading to an ageing process of the surface. A heterogeneous recombination of Cl atoms to Cl2 molecules was observed for aged surfaces.

Kinetics of catalytic hydrogen reduction of SiCl4 in the presence of nickel chloride

We have studied the reduction of silicon tetrachloride in the presence of a nickel-chloride-based catalyst. The kinetics of the process have been analyzed and the order and activation energy of the reaction have been determined. One of the main reactions on the catalyst surface is the transfer of a chlorine atom from a chlorosilane molecule to a hydrogen molecule, resulting in the formation of hydrogen chloride. The proposed reaction mechanism is supported by X-ray diffraction and chemical analysis data.

1-14 アルゴンヌ標準炭の熱分解過程における塩素の形態変化と塩化水素の生成挙動((5)熱分解・ガス化,Session 1 石炭・重質油等)

1-14 アルゴンヌ標準炭の熱分解過程における塩素の形態変化と塩化水素の生成挙動((5)熱分解・ガス化,Session 1 石炭・重質油等)

An integrated model for halide chemical vapor deposition of silicon carbide epitaxial films

Halide chemical vapor deposition emerges as a potent technique for growing silicon carbide epitaxial layers with a high deposition rate in the range of 50–300 μm/h. Experimental studies suggest that the gas composition in the reactor has profound influence on the deposition rate, the quality, and the properties of the as-deposited films. In this study, a comprehensive model was developed for halide chemical vapor deposition process including gas dynamics, heat and mass transfer, gas phase and surface chemistry, and radio-frequency induction heating. Numerical simulations of the deposition process in a horizontal hot-wall reactor using silicon tetrachloride, propane, and hydrogen as precursors were performed over a wide range of operational parameters to quantify the effects of deposition temperature, precursor flow rate, and reactor configuration. Special attention was directed to the etching of silicon carbide films by hydrogen chloride and its impact on the film deposition rate at different processing conditions. Improved gas delivery method was proposed for controlling the formation of hydrogen chloride and the associated etching effect.

The effects of calcium hydroxide on hydrogen chloride emission characteristics during a simulated densified refuse-derived fuel combustion process

This study investigated the effects of different calcium hydroxide (Ca(OH) 2) addition methods on the potential for hydrogen chloride (HCl) formation in a simulated densified refuse-derived fuel (RDF-5) with single metal combustion system. These experiments were conducted at 850 °C with the Ca(OH) 2 spiked in the RDF-5 production or injection in the flue gas treatment system. The results indicated that the potential for HCl formation was decreased significantly by Ca(OH) 2 spiked in the RDF-5 production or injection in the flue gas treatment system. However, the Ca(OH) 2 injection method in the flue gas for HCl emission reduction was better than other method. According to the relationship between the HCl emission and amount of Ca(OH) 2 injected or spiked, it is interesting to find that when the Ca(OH) 2 injected or spiked ranged from 0% to 5%, the potential for HCl formation in the single metal combustion system decreases significantly with increasing Ca(OH) 2 injected or spiked ratio. A corresponding increase in the amount of CaCl 2 partitioned to the fly ash was observed. However, with the ratio of Ca(OH) 2 higher than 5%, the amount of HCl formation showed that no further significant variation occurred with increasing Ca(OH) 2 spiked ratio.

Formations and controls of HCl and PAHs by different additives during waste incineration

This study employed a laboratory-scale fluidized bed incinerator to investigate the formations and controls of hydrogen chloride (HCl) and polycyclic aromatic hydrocarbons (PAHs) by adding different additives in the feedstock during waste incineration. The effects of different organic and inorganic chlorides on the formation and control of HCl and PAHs were also studied. Additionally, the thermodynamic equilibrium modeling was also carried out to interpret and compare with the experimental results. Experimental results showed that the formation of HCl was related to the potential of chlorine released from the combustion of different chlorides. Organic chloride PVC had greater potential to form HCl than inorganic chloride NaCl. The performances of additives were affected by incineration temperature. Increasing temperature decreased the control efficiency of additives because the emission yields of HCl and Cl 2 were increased with temperature. The control efficiencies for HCl and Cl 2 by calcium based additives (Ca(OH) 2, CaO, CaCO 3) were better than that by magnesium based additive (Mg(OH) 2) and CaO was the best additive. The control efficiencies of PAHs by adding CaO in the feedstock were not apparent because the fluidization quality in the fluidized bed incinerator was decreased.

Reactions of SiCl groups in amorphous SiO2 with mobile interstitial chemical species: Formation of interstitial Cl2 and HCl molecules, and role of interstitial H2O molecules

Reactions of the network-bound chloride (SiCl) groups in amorphous SiO2 (a-SiO2 or SiO2 glass) with mobile interstitial oxygen (O2), water (H2O), and hydrogen (H2) molecules thermally loaded from ambient atmosphere and with mobile radicals created by exposure to F2 laser light (λ=157nm,hν=7.9eV) were investigated. Reactions of the SiCl groups with O2 and H2O produce interstitial chlorine (Cl2) and hydrogen chloride (HCl) molecules, respectively. An infrared-absorption band appearing at ∼2815cm−1 is assigned to the interstitial HCl. The SiCl groups do not react with H2 below 400°C. However, sequential gas loading first with O2, then with H2 leads to the production of interstitial H2O, which decomposes the SiCl groups into HCl. Furthermore, the formation of the interstitial HCl with exposure to F2 laser light, most likely due to the cracking of the Si–Cl bonds with photogenerated hydrogen atoms (H0), was demonstrated. These findings yield a general picture of the reactions of the chlorine-related species in a-SiO2 and demonstrate the significant influence of even minor amounts (<1018cm−3) of interstitial H2O on defect formation and annihilation processes.

Formation of Hydrogen Chloride during Temperature-Programmed Pyrolysis of Coals with Different Ranks

The evolution of HCl during pyrolysis of 16 coals with different ranks at a heating rate of 10 °C/min has been studied with an online monitoring method. Approximately 50%−95% of total chlorine is converted to HCl up to 800 °C, and the remainder is mostly retained in the char, which leads to a strong reverse correlation between the two. As the sum of Na and Ca naturally present in coal increases, the amount of HCl tends to decrease. The temperature dependence of the rate of HCl evolved differs with each coal and shows at least four peaks at 280, 360, 480, and 580 °C. The former two peaks are present for two coals alone, whereas the higher temperature HCl formation at ≥450 °C is common for almost all of the coals. The HCl peaks at 280 and 360 °C are considerably small by water washing. When model chlorine compounds added to activated carbon, such as hydrated NaCl, hydrated CaCl2, and organic hydrochlorides, are pyrolyzed in the same manner as above, HCl formation occurs dominantly between 250 and 450 °C in ...

Effects of chlorides on emissions of hydrogen chloride formation in waste incineration

This study investigates the effects of chlorides on the potential for hydrogen chloride (HCI) formation in a single heavy metal incineration system, using simulated municipal solid waste (MSW) with spiked organic and inorganic chlorides. The experiments were conducted at 900°C with the chlorine content varying from 0% to 1.6% (wlw as Cl The spiked chlorides include ionic and molecular bound compounds, such as PVC, C 2Cl 4, NaCl, KCI, and FeCl 3. The results indicate that an increase in the chlorine content enhances the potential for HCI formation in the flue gas and this potential is mainly affected by the characteristics of the chlorides, the presence of alkaline metals (Na and K) and the hydrogen content in the wastes.Furthermore, the HCI formation potential due to the presence of various organic and inorganic chlorides is found to be influenced in decreasing order as: PVC, C 2Cl 4, FeC1 3, NaCl, and KCI. The consistence is confirmed between the above experimental results and model predictions based on thermodynamic equilibrium analysis.

The influence of heavy metals on the formation of organics and HCl during incinerating of PVC-containing waste

The heavy metal, organic pollutants and HCl emissions from incineration pose a grave threat to human health. However, submicro metal particles and organics in gas phase are removed with difficulty by conventional air pollution control apparatus, and could be released into the atmosphere along with the flue gas. This research studied the formation of organics and HCl (hydrogen chloride) during incineration when the feedstock contained different amounts of PVC and heavy metals. The experiments were performed in a bubbling fluidized bed incinerator with two cyclones and scrubbers. Experimental results indicated that the greatest amount of organic compounds produced were aromatic compounds. The amount of organic compounds and HCl increased when the feedstock contained PVC (polyvinyl chloride), and decreased when the feedstock contained heavy metals.