Elimination Of Hydrogen Chloride Research Articles

A novel plumes treater for solid rocket motors during hot‐firing tests using ice tunnel structure

AbstractAiming at the perniciousness of the exhausted plumes from solid rocket motors during hot‐firing tests, a novel plume treater is proposed using the ice tunnel device. The feasibility and effectiveness of this ice tunnel treater were successfully verified by tests on two solid rocket motors, XX 127 and XX 500, with different fuel charges of about 1.5 and 700 kg, respectively. Results show that the plume temperature could be greatly reduced from around 2000 to below 100°C through the ice tunnel for both motors, and the effect of noise reduction as well as the elimination of gaseous hydrogen chloride was also measured to be available in the test of XX 500, indicating the new ice tunnel treater could quickly achieve the “three reductions” of high temperature, serious noise, and gas pollution of the solid rocket motor emissions. Besides, a numerical model considering the factors of air entrainment, afterburning, convective heat transfer, radiation heat transfer, and phase change was established to investigate the flow and heat transfer behaviors within the ice tunnel. The plume temperature at the outlet of the ice tunnel was in good agreement with the experimental data. The intensity of afterburning is mainly determined by the amount of entrained air and the CO concentration. The cooling capacity of the ice tunnel is mainly contributed by convection, air entrainment, and particle radiation. This work could provide new ideas and references for the technological upgrade of the ground test platforms for solid rocket motors.

Effect of SO2 on HCl removal over ethanol-hydrated CaO adsorbent: Mechanism of competitive adsorption and product layer shielding

The elimination of hydrogen chloride (HCl) is essential for wastewater sequestration and safe operation of equipment in coal-fired power plants. A new adsorbent of ethanol-hydrated CaO has been developed, which possesses a 100% HCl removal efficiency lasting 30 min in a fixed bed reactor being much superior to traditional dechlorinators. Nevertheless, SO2 in flue gas has instinctive and strong competition with HCl on the alkaline adsorbent that results in detrimental effects and makes the removal mechanisms confused and unclear. To solve this issue, a series of experiments were designed to evaluate how SO2 influences the performance of HCl adsorption over the adsorbent. Comprehensive characterizations and density functional theory (DFT) calculations further studied the mechanisms of the competition mechanism between SO2 and HCl. The results indicate that SO2 has a detrimental impact on HCl removal by consuming the active Ca site, diminishing the alkalinity and worsening the surface activity due to the product layer formation. DFT calculations reveal that the high adsorption energy of SO2 suppresses the active sites for HCl removal. The faded surface electrostatic potentials (ESP) around the sulfurized Ca active sites lead to apparent activity shielding on the absorbent surface. Besides, the frontier molecular orbital (FMO) theory unveils a narrow electronic transfer energy gap for SO2 adsorption. These findings contribute to elucidation of SO2 competition to HCl on the calcium-based adsorbent in coal-fired flue gas.

Damage function for poly(vinyl chloride) in heritage collections

Yellowing of plastic objects as a consequence of chemical degradation is a common heritage conservation challenge. In the case of poly(vinyl chloride) elimination of hydrogen chloride leads to the formation of polyene sequences that act as chromophores. The objective of this work was to quantitatively evaluate the rate of degradation observed as yellowing, as relevant to room conditions during long-term storage of heritage collections. Degradation was quantified as increase in the b* colour coordinate during accelerated degradation at 50 and 70 °C as a function of temperature, relative humidity, plasticizer content, and polymer molecular weight. The significance of each variable was investigated with multiple linear regression. Lower temperature, lower relative humidity, higher polymer molecular weight and higher plasticizer content were associated with lower degradation rates. The activation energy of 86 kJ/mol was calculated. The concept of ‘1- °C-equivalent’ is introduced to enable variable prioritisation from a heritage management aspect. The resulting model can be used to shape environmental management guidelines and identify the most vulnerable objects in heritage collections.

The Adjustability of Physicochemical Properties: Comparison of 1-Vinyl-5H-tetrazole and 1-Allyl-5H-tetrazole as Ligands in 3d Metal Energetic Coordination Compounds

Energetic coordination compounds (ECCs) show promising properties to be used as potential substitutes for highly toxic lead-containing primary explosives. The concept is to combine the three building blocks: (i) ligand, (ii) transition metal, and (iii) anion, acting as (i) fuel, (ii) matrix, and (iii) oxidizer (e.g., ClO4-, NO3-, ClO3-) or energetic component (e.g., DN-, N3-, picrate, styphnate, trinitrophloroglucinate). By variation of the ligands, the complexes' properties can be adjusted toward their desired performance and sensitivities. In the present study, 1-vinyl-5H-tetrazole (1-VTZ, 1) and 1-allyl-5H-tetrazole (1-ATZ, 2) were used as nitrogen-rich endothermic ligands to form 3d metal (Mn2+, Fe2+, Cu2+, Zn2+, Co2+, Ni2+)-based ECCs. The influence of the introduction of an unsaturated C-C bond (1-ETZ vs 1-VTZ and 1-PTZ vs 1-ATZ) on the performance and sensitivity of the complexes is discussed, as is the lengthening of the alkenyl chain (1-VTZ vs 1-ATZ). For further insights, the novel complexes were compared to literature-known complexes based on N1-substituted C2- and C3-derived tetrazole ligands, respectively. The ligand 1-VTZ (1) was prepared by elimination of hydrogen chloride from 1-(2-chloroethyl)-5H-tetrazole in methanolic KOH solution. 1-ATZ (2) was obtained by a heterocyclization reaction of allylamine with triethyl orthoformate and sodium azide in an acetic acid medium. All compounds were intensively characterized with analytical methods such as XRD, IR, EA, DTA, TGA, and sensitivity measurements (IS and FS). The energetic performances were visibly evaluated in fast heating experiments. Furthermore, PETN initiation and laser ignition experiments were carried out for promising ECCs.

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.

Development of retinoic acid receptor antagonists bearing trans-SF4-alkynyl structure as a linear linker

transTetrafluoro-λ6-sulfane (tetrafluorosulfanyl, SF4) compounds possess unique properties, including a linear structure and high electronegativity. Here, to investigate the utility of the trans-SF4 moiety as a structural element of bioactive compounds, we designed and synthesized novel retinoids containing a trans-SF4-alkynyl group as a linear linker. The radical addition reaction of aryltetrafluorosulfanyl chloride and arylethyne, followed by elimination of hydrogen chloride, afforded the target compounds 1a – 1c. Cell differentiation-inducing activity assay and reporter gene assay revealed that the trans-SF4-alkynyl derivatives 1b and 1c exhibit antagonistic activity towards retinoid acid receptors (RARs). Docking studies suggested that the long and linear linker alters the binding mode of 1b with the RARα ligand-binding domain.

Dechlorination of landfill poly(vinyl chloride) waste and estimation of recovered chlorine

The wet treatment process was used for the dechlorination of poly(vinyl chloride) (PVC) landfill waste plastic, and the process has shown dependence on concentration of alkali. The process of dechlorination of PVC has shown dependence on the concentration of the alkaline solution and the type of organic solvent used in the preparation of the alkaline solution. Ethylene glycol (EG), diethylene glycol (DEG), and tetraethylene glycol (TEG) are the diols that have been investigated. Moreover, the temperature of the PVC dechlorination process and the time of the PVC solution reflux showed effects on the final degree of the dechlorination (DD%). These were calculated using the Mohr method, where the chloride ions were titrated with a standard solution of silver nitrate in the presence of chromate ions. The study shows that 1 M NaOH/TEG alkaline solution was the best to dechlorinate PVC waste with the wet treatment process at 160 ̊c and for 3 h reflux and the process reclaimed poly(vinyl alcohol) PVA as the main product according to the hydroxyl group substitution mechanism (SN2), besides a few units according to the hydrogen chloride elimination mechanism (E2) with a few remaining chlorinated chains after analysis.

Different Reactivities of (5-Ph2P-Ace-6-)2MeSiH toward the Rhodium(I) Chlorides [(C2H4)2RhCl]2 and [(CO)2RhCl]2. Hirshfeld Atom Refinement of a Rh–H···Si Interaction

The reaction of (5-Ph2P-Ace-6-)2MeSiH with [(C2H4)2RhCl]2 proceeded via elimination of ethylene and oxidative addition of the Si–H bond at rhodium and provided the rhodium(III) complex (5-Ph2P-Ace-6-)2MeSiRh(H)Cl (1) possessing a reverse agostic interaction of the type Rh–H···Si, which was characterized by Hirshfeld atom refinement (HAR) of single-crystal X-ray diffraction data. This technique allows the precise and accurate determination of hydrogen positions also for heavier transition-metal hydrides. The bonding situation in the Rh–H···Si interaction was further analyzed using a set of complementary bonding indicators, such as the compliance matrix analysis or real-space bonding indicators derived from the electron and electron pair densities. The reaction of (5-Ph2P-Ace-6-)2MeSiH with [(CO)2RhCl]2 occurred via elimination of hydrogen chloride and produced the rhodium(I) complex (5-Ph2P-Ace-6-)2MeSiRh(CO)2 (2).

Synthesis and Crystal Structures of 4,5-Dihydroimidazo[1,5-b]pyrazol-6-ones

AbstractThe synthesis of previously unattainable 2,5-disubstituted 4,5-dihydroimidazo[1,5-b]pyrazol-6-ones has been developed. Electrochemical reductions of readily available 2,2,2-trichloroethylideneacetophenones were followed by reaction with hydrazine, leading to 3-aryl-5-dichloromethyl-2-pyrazolines. These were treated with isocyanates to obtain the corresponding aminocarbonyl derivatives, which were found to be able to form an otherwise almost inaccessible imidazo[1,5-b]pyrazole ring system via a one-step reaction involving internal condensation followed by hydrogen chloride elimination and aromatization. The molecular­ structures of 2-(4-methylphenyl)-5-tosyl-4,5-dihydro­imidazo[1,5-b]pyrazol-6-one, 5-dichloromethyl-N-(4-chlorophenyl)-4,5-dihydro-3-p-tolylpyrazole-1-carboxamide, and 5-(4-bromophenyl)-2-p-tolyl-4,5-dihydroimidazo[1,5-b]pyrazol-6-one were determined by X-ray crystallographic analysis.

Efficient Methods for the Synthesis of Novel Arylazothiazoles Based on Acetylferrocene or Adamantane.

Hydrazonoyl halides are convenient for the synthesis of arylazothiazoles. A series of novel arylazothiazoles were efficiently synthesized from the reaction of hydrazonoyl chlorides with 2-(adamantan-2-ylidene)hydrazinecarbothioamide or 2-(ferrocenyl-1-ylidene)hydrazinecarbo-- thioamide in dioxane used as an aprotic solvent because of its lower toxicity and higher boiling point (101 °C) and triethylamine at reflux. The reaction mechanistic pathway proceeded by the nucleophilic substitution reaction by the elimination of hydrogen chloride to give thiohydrazonates as intermediate, which in situ undergo intramolecular cyclization and loss of water molecule to afford the final product of novel arylazothiazoles. This method is simple with good yield and excellent purities. The synthetic schemes for the final products are proposed and discussed. The chemical structures of the final products were identified by different techniques, such as elemental analysis, Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and mass spectrometry (MS). In this article, we prepared arylazothiazoles from the reaction of 2-(adamantan-2-ylidene)hydrazinecarbothioamide or 2-(ferrocenyl-1-ylidene)hydrazinecarbothioamide with hydrazonoyl halides.

Facile preparation and properties of porous carbon from chlorinated polymer with high chlorine content

Chlorinated polypropylene(CPP), chlorinated polyethylene(CPE) and chlorinated polyvinyl chloride(CPVC) with high chlorine content were used to prepare porous carbons under inert gas and air atmosphere, respectively. Due to their flame retardance, carbon materials were both prepared from two atmosphere through thermal dehydrochlorination. The microstructure and porous textures of the obtained carbons were characterized by BET, XPS, SEM, TEM, XRD and Raman, respectively. The results show that the dehydrochlorination of all precursors is more efficient in air than nitrogen, because the oxygen molecular in air atmosphere accelerates the elimination of hydrogen chloride(HCl). Moreover, CPP-derived carbons display apparent higher surface area than that derived from CPE and CPVC. Furthermore, the carbonization condition is optimized and porous carbon with a surface area of 1035 m2/g is prepared in mild carbonization condition and without any activation.

Dechlorination of PVC wastes by hydrothermal treatment using alkaline additives

ABSTRACTSome chemicals were usually utilized in the hydrothermal dechlorination (HTD) of chlorine-containing wastes without revealing their roles. This work intends to investigate the role of chemical additives in the HTD of PVC (polyvinyl chloride). Several chemicals, including Na2CO3, KOH, NaOH, NH3·H2O, CaO and NaHCO3, were added into the PVC HTD process, which was conducted in subcritical Ni2+-containing water at 220°C for 30 min. The results show the alkalinity of additives had notable effects on the dechlorination efficiency (DE) of PVC due to the neutralization between HCl and additives. The most effective additive is Na2CO3, with the maximum DE of 65.12% at a Na2CO3 concentration of 0.025 M in this study. According to SEM, the hydrochar obtained from the HTD with Na2CO3 become more porous and looser than the others did, which contributed to the acceleration of PVC dechlorination. The DE vibration with the concentration of additives was different. For Na2CO3, it was firstly increased and then decreased with Na2CO3 concentration increasing from 0.01 to 0.04 M. For KOH and NaOH, it kept reducing with the concentration increasing from 0.02 to 0.08 M. The drop in DE was ascribed to surface poisoning and a loss in the supported active phase resulting from the formation of metal chloride species. FTIR analysis shows that the elimination of hydrogen chloride was the main route for HTD of PVC. All the results provide some fundamental data to find some cheap but efficient chemicals with aim to recycle the chlorinated organic wastes effectively.

Aminopyridine stabilized group-IV metal complexes and their applications

During the last two decades, group-IV metals-based aminopyridinato complexes have attracted a tremendous research interest because of immense industrial needs for the catalyst which would be of higher activity and selectivity with lower toxicity and lower cost. Chemistry of titanium (Ti) and zirconium (Zr) complexes was more extensively explored as compared to hafnium (Hf) complexes. Direct synthesis, salt metathesis, amine elimination, alkane elimination, silyl chloride elimination, hydrogen chloride elimination and toluene elimination protocols have been used for the synthesis of group-IV metal complexes. Changes in ligand and complex design were made to optimize these catalysts for olefin polymerization. Most of these complexes have shown good catalytic activities when activated with dry methyl aluminoxane. Ligand transfer to aluminum was found in these complexes, particularly with less bulky ligands, and this ligand transfer problem was overcome by tridentate ligands but the activities of these complexes were not competitive to complexes with bidentate aminopyridinato ligands. Majority of these complexes produce high-molecular-weight polymers with broader molecular weight distributions, and Hf-complexes produce longer chain polymers than their comparative Ti and Zr aminopyridinato complexes. It could be deduced that group-IV metals inherit the potential for optimal polymerizing catalysts probably, because of their almost vacant d-orbitals, these act as hard acids which on combination with soft bases carry the opportunity to design and develop polymerization catalysts which could overcome the problems associated with existing systems.

A quantum chemical study of unexpected reaction of α-chloroacyl chlorides with 1,2-dichloroethylene in the presence of aluminum chloride

The reactions of acetyl chloride and chloroacetyl chloride with 1,2-dichloroethylene in the presence of aluminum chloride have been mechanistically studied at the M06/6-311+G(d,p) level of theory. The reaction with acetyl chloride proceeds via the classical channel to afford the expected 1,2-dichlorovinyl ketone. The reaction with chloroacetyl chloride occurs through the alternative channel delivering dichloromethyl-2-chlorovinylketone instead of anticipated chloromethyl-1,2-dichlorovinylketone. The quantum-chemical calculations have shown that the difference between classical and alternative channels is due to the competitive processes occurring at the first stage of the reaction, namely formation of adducts and elimination of hydrogen chloride. In the reaction involving acetyl chloride, the first channel is kinetically more favorable, whereas in the reaction with participation of chloroacetyl chloride, the second channel becomes preferable.

Interaction of ethylenechlorophosphite with hydroxyl-containing azomethines

The reaction of imine I with ethylenechlorophosphite II afforded cyclic phosphonate III as a mixture of diastereomers (δP 15.92, 16.13 ppm) in the 70:30 ratio. Hydrolysis of III gave aminophosphonate IV (δP 10.41 ppm). The reaction proceeded via phosphorylation of imine I at the hydroxyl group with elimination of hydrogen chloride. The latter protonated the imine nitrogen atom, increasing electrophilicity of the C=N bond. Attack of the trivalent phosphorus atom was accompanied by formation of an activated imino spirocyclic moiety which was converted into III as a result of attack of chloride anion at the carbon atom of dioxaphospholane fragment (Scheme 1).

Iridium-Catalyzed Annulative Coupling of 2-Arylbenzoyl Chlorides with Alkynes: Selective Formation of Phenanthrene Derivatives

2-Arylbenzoyl chlorides undergo annulative coupling with internal alkynes in the presence of a catalyst system of [IrCl(cod)]2/P(t-Bu)3 to selectively afford the corresponding phenanthrene derivatives accompanied by elimination of carbon monoxide and hydrogen chloride. The reaction occurs without addition of any external base. Deuterium-labeling experiments using 2-(d5-phenyl)benzoyl chloride suggest that the rate-determining step does not involve the C2'-H bond cleavage. Formation of a [(t-Bu)3PH][(biphenyl-2,2'-diyl)Ir(CO)Cl2] complex dimer, of which the structure was determined by single-crystal X-ray analysis, from a stoichiometric reaction at 60 °C without addition of alkyne also supports the facile C-H cleavage.

Synthesis, structure, and antibacterial activity of aminobenzofuroxan and aminobenzofurazan

The amination of 4,6-dichloro-5,7-dinitrobenzofuroxan and 4,6-dichloro-5,7-dinitrobenzofurazan with dibenzylamine followed the aromatic nucleophilic substitution pattern (SNAr) and gave products of replacement of both chlorine atoms in the six-membered ring with elimination of hydrogen chloride. Regardless of the reactant ratio, 4,6-dichloro-5,7-dinitrobenzofuroxan was converted into 4,6-bis(dibenzylamino)-5,7-dinitrobenzofuroxan, whereas 4,6-dichloro-5,7-dinitrobenzofurazan under analogous conditions gave rise to unusual bisammonium derivative which lost proton from the amino group on C4 and benzyl group from the amino group on C6; as a result, the corresponding diamine with secondary and tertiary nitrogen atoms was obtained. The structure of the isolated compounds was determined by IR and NMR spectroscopy, elemental analysis, and X-ray analysis; their thermal stability was studied by simultaneous thermogravimetry and differential scanning calorimetry.

Rapid photoassisted access to N,O,S-polyheterocycles with benzoazocine and hydroquinoline cores: intramolecular cycloadditions of photogenerated azaxylylenes.

o-Azaxylylenes have been known for half a century, but remained in relative synthetic obscurity until a decade ago, when Corey and Steinhagen reported their first preparation under simple mild conditions by base-induced elimination of hydrogen chloride from derivatives of o-chloromethylaniline. It was noted that “Surprisingly, simplest method possible for o-azaxylylene production ... has never been reported.” Synthetically useful reactions of o-xylylenes (i.e. allcarbon o-quinodimethanes) are plentiful, and their generation from aromatic o-alkyl ketones by an intramolecular photoinduced hydrogen abstraction is well documented. Given this fact, it was surprising to us that the equally simple photogeneration of o-azaxylylenes from o-aminoketones by an excited-state intramolecular proton transfer (ESIPT) has never been utilized in synthetic chemistry. It is conceivable that such implementation was attempted but failed due to the fast back proton transfer successfully competing with bimolecular cycloadditions. Intramolecular proton transfers from one heteroatom to another (and back) are fast; a typical example is the much studied photophysics of salicylaldehyde or o-hydroxyacetophenone, although the elusive tautomeric form is not impossible to characterize. We, however, found that the intramolecular cycloaddition reactions of o-azaxylylenes photogenerated by excited-state proton transfer can successfully compete with the back proton transfer. Herein, we report the first example of [4+ 2] and [4+ 4] cycloaddition reactions of photogenerated azaxylylenes with unsaturated pendant groups; this reaction offers expeditious access to a diverse array of N,S,O-polyheterocycles with mostly unprecedented topologies (Scheme 1). As the azaxylylenes are expected to act as acceptors in the inverse-electron-demand cycloaddition reactions, we synthesized photoactive azaxylylene precursors 1 and 4 by coupling o-aminoketones with furanor thiophenepropionic acid chlorides. These o-acylamido precursors have broad UV Scheme 1. Photogeneration of azaxylylenes and their intramolecular photocyclizations.

Expedient synthesis of (E)‐3‐methylcyclopentadec‐2‐en‐1‐one, an important precursor for (R)‐(−)muscones

ABSTRACTAn expedient synthesis of (E)‐3‐methylcyclopentadec‐2‐en‐1‐one, an important precursor for (R)‐(−)‐muscone, was developed. The key steps were vapour‐phase intramolecular aldol condensation catalysed by zinc oxide at 360 °C followed by double bond isomerization by the addition–elimination of hydrogen chloride. Copyright © 2011 John Wiley & Sons, Ltd.

Dynamics of Cl (2Pj) Atom Formation in the Photodissociation of Fumaryl Chloride (ClCO − CH = CH − COCl) at 235 nm: A Resonance Enhanced Multiphoton Ionization (REMPI) Time-of-Flight (TOF) Study

The photodissociation dynamics of fumaryl chloride (ClCO-CH═CH-COCl) has been studied in a supersonic molecular beam around 235 nm using resonance enhanced multiphoton ionization (REMPI) time-of-flight (TOF) technique by detecting the nascent state of the primary chlorine atom. A single laser has been used for excitation of fumaryl chloride and the REMPI detection of chlorine atoms in their spin-orbit states, Cl ((2)P(3/2)) and Cl* ((2)P(1/2)). We have determined the translational energy distribution, the recoil anisotropy parameter, β, and the spin-orbit branching ratio for chlorine atom elimination channels. To obtain these, measured polarization-dependent and state-specific TOF profiles are converted into kinetic energy distributions, using a least-squares fitting method, taking into account the fragment recoil anisotropies, β(i). The TOF profiles for both Cl and Cl* are found to be independent of laser polarization; i.e., β is well characterized by a value of 0.0, within the experimental uncertainties. Two components, namely, the fast and the slow, are observed in the translational energy distribution, P(E(T)), of Cl and Cl* atoms, and assigned to be formed from different potential energy surfaces. The average translational energies for the fast components of the Cl and Cl* channels are 14.9 ± 1.6 and 16.8 ± 1.6 kcal/mol, respectively. Similarly, for the slow components, the average translational energies of the Cl and Cl* channels are 3.4 ± 0.8 and 3.1 ± 0.8 kcal/mol, respectively. The energy partitioning into the translational modes is interpreted with the help of various models, such as impulsive and statistical models. Apart from the chlorine atom elimination channel, molecular hydrogen chloride (HCl) elimination is also observed in the photodissociation process. The HCl product has been detected, using a REMPI scheme in the region of 236-237 nm. The observation of the molecular HCl in the dissociation process highlights the importance of the relaxation process, in which the initially excited parent molecule relaxes to the ground state from where the molecular (HCl) elimination takes place.