Formation Of HBr Research Articles

Treatment of brominated epoxy resin waste in subcritical dimethylformamide wastewater: Upcycling of brominated epoxy resin and dimethylformamide degradation

The debromination and upcycling of brominated epoxy resin (BER) waste is important for the e-waste treatment, while the degradation and removal of N, N-dimethylformamide (DMF) is the critical step for the DMF wastewater treatment. In this study, a co-treatment strategy was proposed for the BER waste and DMF wastewater by the subcritical water process. The co-treatment was carried out using subcritical DMF wastewater (SDW) as the reaction medium. The results showed a significantly synergistic effect between the BER conversion and DMF degradation in the SDW process. The optimal reaction conditions were as follows: reaction temperature of 300 °C, solid-to-liquid ratio of 1:15 g/mL, DMF wastewater of 30000 mg/L and reaction time of 60 min. Under the optimal reaction conditions, the debromination ratio of the BER was 98.57 %, the degradation ratio of the DMF reached 99.59 %, and phenolic substances with a purity of 86.61 % were recovered. The formation of HBr from the debromination of the BER was the most significant factor affecting the pH of the system, which had a noticeable impact on the degradation of the DMF. The main degradation products of the DMF were dimethylamine (DMA), methylamine (MA), NH3, NH4+, and CO2. The products degraded from the DMF could significantly promote the debromination and conversion of the BER. Life cycle assessment (LCA) analysis showed that the SDW process had low CO2 emissions. It is believed that the SDW process proposed in this study is an efficient technology for the synergistic treatment of the BER waste and DMF wastewater.

A novel subcritical water synergistic co-treatment of brominated epoxy resin and copper-based spent catalysts: debromination, phenol production, and copper recovery

In this study, a high-efficiency co-treatment strategy for brominated epoxy resin (BER) and copper-based spent catalyst (CBSC) was developed by using subcritical water (SubCW) process. Multivalent species of copper released from CBSC could accelerate the electron transfer of the SubCW system and efficiently catalyze radical reactions to promote the debromination and decomposition of BER, and had an effect on the capture and binding of bromine species. Meanwhile, the formation of HBr by the BER debromination resulted in a decrease in the system pH and markedly enhanced the leaching/recovery of Cu from CBSC. The optimal conditions of the SubCW co-treatment process were as follows: reaction temperature of 350 °C, solid-to-liquid ratio of 1:30 g/mL, BER-to-CBSC mass ratio of 10:1 g/g, and reaction time of 60 min. Under the optimal conditions, 97.12 % of the Br could be removed from BER by the SubCW co-treatment process and a high-purity phenol (64.09 %) could be obtained in the oil phase product, and 86.44 % of Cu in the CBSC could be leached and recovered. The introduction of CBSC significantly changed the decomposition path of BER. Compared to the SubCW process without CBSC, bromine-free oils products could be obtained by the co-treatment process of BER and CBSC at low-temperature. This study provided a novel understanding of resource conversion mechanism of BER and CBSC in subcritical water medium via the synergistic effect between the two different waste streams to improve treatment efficiency and synchronously recover high-value products.

Synergistic flame retardancy of tris(1‐methoxy‐2,2,6,6‐tetramethyl‐piperidin‐4‐yl)phosphite and tris(2,4,6‐tribromophenoxy)‐1,3,5‐triazine/Sb2O3 in high‐impact polystyrene

SummarySynergistic flame retardancy of tris(1‐methoxy‐2,2,6,6‐tetramethyl‐piperidin‐4‐yl) phosphite (NORPM) and tris(2,4,6‐tribromophenoxy)‐1,3,5‐triazine (TTBPC)/Sb2O3 in high‐impact polystyrene (HIPS) was studied by limiting oxygen index (LOI) determination, UL‐94 test, and cone calorimetry test (CCT). NORPM has an exceptional synergistic effect in HIPS. When the dosage of TTBPC, Sb2O3, and NORPM was 12.8, 3.2, and 0.5 wt% respectively, flame retardant effectivity and synergistic effectivity were 0.424 and 1.15 respectively. Compared with the Flame retardant (FR)‐HIPS containing 16.0 wt% of TTBPC/Sb2O3, the LOI of FR‐HIPS increases from 23.8% to 25.4%, the flame‐retardant rating of FR‐HIPS can be improved from UL 94 V‐2 to V‐0, and the peak heat release rate and total heat release are significantly reduced by combining NORPM in 0.5 wt% concentration. NORPM induces the synergistic effect mainly through the following mechanisms: the active radicals produced by the pyrolysis of NORPM promote the release of bromine radicals from TTBPC and the formation of HBr, which improves the flame retardancy of TTBPC; the above active radicals, together with HBr, quench active free radicals, such as the hydroxyl radical (·OH) and decompose the free radical source, which interrupts the chain reaction during combustion and results in a more efficient flame retardant effect in gaseous phase.

Synergistic Fire Retardancy of Bis(1‐methoxy‐2,2,6,6‐tetramethylpiperidin‐4‐yl)sebacate and Tris(2,4,6‐tribromophenoxy)‐1,3,5‐triazine/Sb2O3 in HIPS

Bis(1‐methoxy‐2,2,6,6‐tetramethylpiperidin‐4‐yl)sebacate (NORSM) was found to perform an exceptional synergistic effect with tris(2,4,6‐tribromophenoxy)‐1,3,5‐triazine (TTBPC)/Sb2O3 in HIPS. The LOI of fire retardant HIPS (FR‐HIPS) with 16 wt% of TTBPC/Sb2O3 increased from 23.8% to 25.2%, the flame retardant rating of FR‐HIPS was improved from UL 94 V‐2 to UL 94 V‐0, and various heat release parameters such as peak heat release rate, total heat release, and mean effective heat of combustion were greatly lowered by combining NORSM of 0.50 wt%. The Py‐GC/MS results revealed that NORSM induced the role of synergistic effect; the main mechanisms were as follows: the active radicals such as methoxy radicals and aminyl radicals produced by the pyrolysis of NORSM promote the release of bromine radicals from TTBPC and the formation of HBr and CO2, which improves the flame retardancy of TTBPC/Sb2O3; the above active radicals, together with HBr, quench active free radicals, such as the hydroxyl radical (OH), and decompose the free radical source, which interrupts the chain reaction during combustion and results in a more efficient flame retardant effect in gaseous phase.

New methods to synthesize phthalaldehyde and its diacetals

A new synthesis of phthalaldehyde that avoided formation of HBr involved treatment of 1,2-bis(dibromomethyl)benzene with trimethyl orthoformate (1: 6, 90 °C, 10 mol.% ZnCl2) to obtain acyclic diacetal without admixture of cyclic one (1,3-dimethoxy-1,3-dihydrobenzo-[c]furan) followed by hydrolysis to give the target dialdehyde. Phthalaldehyde reacted with CH(OMe)3 in the presence of trifluoroacetic acid to yield exclusively cyclic diacetal. Acyclic diacetal was phosphorylated by treatment with secondary chlorophosphines and by the reaction with PCl3 followed by treatment with PIII acid ester.

First Evidence of Vibrationally Driven Bimolecular Reactions in Solution: Reactions of Br Atoms with Dimethylsulfoxide and Methanol.

We present evidence for vibrational enhancement of the rate of bimolecular reactions of Br atoms with dimethylsulfoxide (DMSO) and methanol (CH3OH) in the condensed phase. The abstraction of a hydrogen atom from either of these solvents by a Br atom is highly endoergic: 3269 cm-1 for DMSO and 1416 or 4414 cm-1 for CH3OH, depending on the hydrogen atom abstracted. Thus, there is no thermal abstraction reaction at room temperature. Broadband electronic transient absorption shows that following photolysis of bromine precursors Br atoms form van der Waals complexes with the solvent molecules in about 5 ps and this Br•-solvent complex undergoes recombination. To explore the influence of vibrational energy on the abstraction reactions, we introduce a near-infrared (NIR) pump pulse following the photolysis pulse to excite the first overtone of the C-H (or O-H) stretch of the solvent molecules. Using single-wavelength detection, we observe a loss of the Br•-solvent complex that requires the presence of both photolysis and NIR pump pulses. Moreover, the magnitude of this loss depends on the NIR wavelength. Although this loss of reactive Br supports the notion of vibrationally driven chemistry, it is not concrete evidence of the hydrogen-abstraction reaction. To verify that the loss of reactive Br results from the vibrationally driven bimolecular reaction, we examine the pH dependence of the solution (as a measure of the formation of the HBr product) following long-time irradiation of the sample with both photolysis and NIR pump beams. We observe that when the NIR beam is on-resonance, the hydronium ion concentration increases fourfold as compared to that when it is off-resonance, suggesting the formation of HBr via a vibrationally driven hydrogen-abstraction reaction in solution.

ChemInform Abstract: Convenient Synthesis of Glycosyl Bromide from 1‐O‐Acetyl Sugars by Photo‐Irradiative Phase‐Vanishing Reaction of Molecular Bromine.

AbstractA bottom phase of molecular bromine, overlaid with perfluorohexane and again overlaid with ethylacetate containing a monosaccharide gives rise to formation of HBr upon UV irradiation to furnish glycosyl bromide.

Infrared fluorescence from multiphoton dissociation of vinyl bromide: Emission from the products and the parent molecule

Abstract A time-resolved study of the infrared fluorescence emission produced in the infrared multiphoton dissociation of vinyl bromide at different experimental conditions has been carried out. Two different regimes, namely unimolecular and collisional, have been identified and characterized through the parent vinyl bromide and the HBr and C 2 H 2 photoproducts emissions. In the pressure interval studied, the formation of HBr has been determined to be mainly unimolecular, while the C 2 H 2 is produced through a collisionally assisted photodecomposition process. The collisional regime is explained in terms of the 3-centre elimination channel while the unimolecular regime is ascribed to the 4-centre mechanism. Relaxation rate constants for both the vibrationally excited HBr by vinyl bromide and by Ar and for vibrational excited VBr by unexcited VBr, are reported.

Effects of metals on the transformation of hexabromocyclododecane (HBCD) in solvents: Implications for solvent-based recycling of brominated flame retardants

The management of electronic wastes (e-wastes) has become a global issue as it may release large quantities of hazardous materials such as heavy metals and brominated flame retardants (BFRs) to the environment. Solvent-based recycling is a newly developed, efficient and environmentally beneficial technology for the removal or recovery of BFRs from e-wastes. However, little is known about the behavior of BFRs in the solvents and to what extent they may be affected by co-existing heavy metals. This study quantified the rates of transformation of hexabromocyclododecane (HBCD), a widely used BFR, in the presence of different solvents (i.e. acetone, methanol or toluene) and metals (i.e. Ni, Cu, Zn, Fe or Al). Our experimental results showed that less than 20% of HBCD was transformed in all pure solvent systems within 24 h at 50 °C. The presence of Ni greatly increased the transformation of HBCD (45–99%) in these solvent systems, whereas other metals had little or no effect on extraction process. The kinetics study showed that transformation of HBCD in Ni-containing systems followed pseudo-first-order kinetics and that the highest transformation rate constant (1.2 ± 0.1 h −1) of HBCD was recorded in the Ni + acetone system. The formation of HBr and pentabromocyclododecene in the acetone + Ni system suggested that transformation of HBCD proceeded via dehydrobromination. Collectively, these results indicated that acetone should not be applied in the recycling or extraction of HBCD from Ni-rich e-wastes, as debromination of HBCD may occur during these processes, even at mild extraction temperatures.

Desolvation-induced non-linearity in the analysis of bromine using an ultrasonic nebulizer with membrane desolvation and inductively coupled plasma mass spectrometry

Ultrasonic nebulization coupled with a membrane desolvator is used for the introduction of bromine containing samples in inductively coupled plasma mass spectrometry. Severe non-linearity (R2 = 0.9317) is observed when ammonium bromide (NH4Br, 0–100 ng mL−1) solution is nebulized, suggesting the loss of bromide ions at the desolvation stage. It is proposed that the primary reason for this phenomenon is the formation of gaseous HBr and its subsequent removal in the desolvation unit. In order to preserve the linearity in the calibration curve, excess NaCl (1 μg mL−1 of Na) is added to the solutions, resulting in a perfectly linear (R2 = 0.9999) calibration curve. However, in the presence of a strong acid (2% HNO3), no significant improvement in the linearity is observed with the addition of NaCl. Bromine signal enhancement and improved linearity are also observed when 1 μg mL−1 of Na is added to KBr solutions. Also, addition of 2% HNO3 to KBr solutions results in signal suppression through the formation of HBr.

Thermal behavior of brominated and polybrominated compounds I: closed vessel conditions

Israel is one of the leading manufacturers of organic brominated compounds, hence the very intensive manufacturing of such compounds creates both, hazardous industrial refuge and large amounts of brominated byproducts. Environmentally the storage of these huge amounts of materials may lead to major hazards: (a) water reservoirs contamination; (b) land contamination. It is suggested to incinerate the accumulated and presently produced organic wastes by the existing organic hazardous wastes incineration plants, one should take into account the fact that polybrominated compounds are fire retardants! The thermal behavior of the CBr bond was scantly investigated up-to-date. In the present work and those to follow we report on our examinations of various brominated organics pyrolysis experiments e.g. bromohexane (BH) bromocyclohexane (BCH), bromonaphthalene, 4,4′-isopropylidene bis(2,6-dibromophenol) measurements were carried out only for the solid and polybrominated compounds whereas time and temperature experiments were conducted under closed vessel conditions (quartz ampoules). The analyses of the pyro-products were initially monitored by gas, extractables and solids using both selective detectors (FID, ECD), GC and GC/MS (for gases and liquids). Experiments were conducted between 400 and 1000°C, and pyrolysis exposure times from 10 s to 1 h. We present the results obtained for single compound and hydrogen donor mixed with compound. The conclusions drawn as presented in the concluding remarks are: (1) most of the released bromine is in HBr form and probably the reason for retardation; (2) At 1000°C the organic products are low molecular weight gases and char; (3) The amounts of dibenzodioxins and dibenzofurans are minute and thermally unstable; (4) the aliphatic brominated compounds are thermally less stable than the aromatics; (5) Under oxygen conditions the formation of large amounts of HBr is acting as retardant even in the presence of excess hydrogen donors; (6) the presence of hydrogen donors is conducive to the formation of HBr, increase of rate and quantity.

An ab initio study of the hydrogen abstraction reaction of methane by bromine atoms and bromine monoxide radicals

The structures, vibrational spectra, and relative energetics for the transition states of the hydrogen abstraction reactions of methane by bromine (Br) atoms and bromine monoxide (BrO) radicals have been examined by using the quadratic configuration interaction method in conjunction with different basis sets. From the calculated energetics of the CH 4+Br→CH 3+HBr and CH 4+BrO→CH 3+HOBr reactions, we find that the energy barrier for the formation of HOBr is higher than that for the formation of HBr. The endothermicity of the CH 4+Br→CH 3+HBr reaction is 7.9 kcal mol −1 higher than that for the CH 4+BrO→CH 3+HOBr reaction.

Studies of HBr Uptake on Ice Films at 188 K

The interaction of HBr with ice films has been studied in a fast-flow reactor, and the formation of HBr·3H2O and HBr·2H2O near the ice film surface was determined at 188 K. The existence of the hydrates was further verified by the construction of a low-temperature HBr−ice phase diagram under the experimental conditions. Hydrate formation is a critical process in understanding the higher HBr uptake on ice films and the heterogeneous reaction mechanism involving HBr on the ice surface. The effects of total pressure and ice film thickness on HBr uptake were also investigated. The co-uptake of HBr and HCl showed that the HBr uptake was in general more efficient than that of HCl. This study provides the detailed thermodynamic properties of HBr on ice at the pressure range of 10-8 −10-5 Torr and 180−220 K.

5422578 Magnetic resonance probehead

A time-resolved study of the infrared fluorescence emission produced in the infrared multiphoton dissociation of vinyl bromide at different experimental conditions has been carried out. Two different regimes, namely unimolecular and collisional, have been identified and characterized through the parent vinyl bromide and the HBr and C2H2 photoproducts emissions. In the pressure interval studied, the formation of HBr has been determined to be mainly unimolecular, while the C2H2 is produced through a collisionally assisted photodecomposition process. The collisional regime is explained in terms of the 3-centre elimination channel while the unimolecular regime is ascribed to the 4-centre mechanism. Relaxation rate constants for both the vibrationally excited HBr by vinyl bromide and by Ar and for vibrational excited VBr by unexcited VBr, are reported.

Half-collision dynamics in the penning ionization of HBr

The ionization of HBr by metastable helium and neon to give HBr +(A 2Σ +) was studied in crossed molecular beams, by measuring the A 2Σ + → X 2H 32,1/2 emission spectrum. Vibrational distributions of HBr + (A) were calculated from the spectrum, and compared with those determined by Penning ionization electron spectroscopy. With Ne* + HBr the final-state interaction [NeHBr +(A) — Ne + HBr +(A)] results in vibrational relaxation of HBr +(A), which is accompanied by rotational excitation, indicating that formation of HBr +(A) occurs predominantly by a close-range repulsive interaction with Ne* at the hydrogen end of the molecule.

Synthesis of 5-S-cysteamine-6-hydroxythymine and evidence of its formation in the ? radiolysis of aqueous solutions of thymine and cysteamine

1. The hydrolysis of 5-bromo-6-hydroxythymine at pH 5.5–7.5 proceeds as a first-order reaction with the formation of HBr and 5,6-dihydroxythymine. As the pH is raised from 5.8 to 7.6, the hydrolysis rate constant increases from 3·10−3 to 12·10−3 sec−1. 2. As a result of the reaction of 5-bromo-6-hydroxythymine with cysteamme, 5-S-cysteamme-6-hydroxythymine is formed. 3. In the radiolysis of aqueous solutions of thymine and cysteamine, cross-linked products are formed, one of which has been identified as 5-S-cysteamine-6-hydroxythymine.

Ionisation von Triphenylmethylbromid in Nitromethan

Ionisation of Triphenylmethylbromide in NitromethaneDissolving triphenylmethylbromide in nitromethane leads to the formation of HBr which complicates conductivity and spectroscopic measurements of carbenium ion absorption. As a result of addition of bromide ions (as tetraethylammonium bromide = Et4NBr) the triphenylmethylabsorption totally disappeares. It can be concluded that Ph3CBr in nitromethane is partially present in form of free (solvated) ions. The carbenium ion concentration has been determined as a function of gross concentration and temperature.

Phase effects in the radiation chemistry of orientationally disordered crystals—I: 1-Bromoadamantane

In the investigation of the radiolysis of 1-bromoadamantane, three gaseous and six solid products were observed as a function of total dose. Although the same products were found in both the α- and β-phases of solid 1-bromo-adamantane, the G-values of these products were markedly different in the two phases, e.g. an efficient abstraction reaction for the formation of HBr in the β-phase was found to be absent in the α-phase. The results obtained in this study are discussed in terms of mechanisms based on the diffusional mobility of the reactive intermediates in the two mesophases, with the diffusional mobility of the reactive intermediates in the two mesophases being related to the entropy release in the formation of each mesophase.

γ-Radiolyse von 4-Nitrophenol in Wässriger HBr-Lösung

In the γ-radiolysis of aqueous solutions of 4-nitrophenol, 4-nitropyrocatechol ( G= 2·95) and 4-aminophenol ( G = 1·1) are formed. The addition of HBr in concentrations up to 0·5 mol dm −3 HBr has a protective effect. The G-value for the disappearance of 4-nitrophenol is strongly reduced (Fig. 2). At 0·5 mol dm −3 HBr G(4-nitro-pyrocatechol) is lowered to 0·1, and G(4-aminophenol) to 0·15. This effect is explained by assuming that the OH radicals react with Br − giving Br . atoms which further react to Br 2 −. An explanation of this protective effect is based on the assumption that Br . or Br 2 − may either dehydrogenate the 4-nitrophenol-H atom adduct, or that, alternatively, the 4-nitrophenol-Br atom adduct may react with the H atom adduct resulting in the formation of HBr and two molecules of 4-nitrophenol. With HBr concentrations above 0·5 mol dm −3 the G value for the disappearance of the substrate increases again owing to loss through bromination. In a 9 mol dm −3 HBr solution 2-bromo-4-nitrophenol ( G = 4,9) and 4-aminophenol ( G = 1·37) are formed. Some possible mechanisms of bromination are discussed. A satisfactory material balance was obtained for all HBr concentrations investigated.

Infrared chemiluminescence in the systems H+Br 2 and H+HBr

In an earlier qualitative study of partially resolved infrared chemiluminescence from H+Br 2 , it was reported that HBr was formed in levels up to and including v =6. In the present work (despite a reduction in pressure to ca. 0.03 mm Hg, and in mean residence time in the vessel to 0.005 sec), the vibrational-rotational band structure was resolved and the stationary-state distribution N v in levels v =1–6 was measured. Relative rate constants k v for the direct formation of HBr in levels v =3–6 as a product of the reaction H+Br 2 → HBr v + Br are reported for the first time. These resemble the corresponding k v 's for H+Cl 2 qualitatively, but differ quantitatively. The difference is in the rate of decrease of the function k v (v) toward higher v : the function falls significantly less steeply for H+Br 2 than for H+Cl 2 . The same applies to the function k f (f) in which the variable v has been replaced by f , the fraction of the energy-of-reaction entering vibration. In both systems, H+Br 2 and H+HBr, infrared chemiluminescent emission was observed at ca. 2.71 μ due to the forbidden Br * ( 2 P 1/2 )→Br( 2 P 3/2 ) electronic transition. Evidence is presented which indicates that Br * is formed most efficiently in some binary process, other than the H+Br 2 reaction. This could be the reaction H+HBr → H 2 +Br * (the relative concentration of Br * is markedly greater in the H+HBr system), or it could be an energy transfer process.