Precise Equilibrium Constants from Spectrophotometric Data: BrCl in Br2/Cl2 Gas Mixtures

Phosgene Synthesis Catalysis: The Influence of Small Quantities of Bromine in the Chlorine Feedstream

The effect of relatively low concentrations of Br2(g) in the Cl2(g) feedstock for phosgene synthesis catalysis via the reaction of CO(g) and Cl2(g) over activated carbon (Donau Supersorbon K40) is explored. Under the stated reaction conditions and in the absence of a catalyst, BrCl(g) forms from the reaction of Cl2(g) and Br2(g). Phosgene synthesis over the catalyst at 323 K is investigated for Br2(g):Cl2(g) molar flow ratios in the range 0-1.52% (0-15,190 ppm) and shows enhanced rates of phosgene production. Maximum phosgene production is observed at a Br2(g):Cl2(g) molar flow ratio of 1.52% (15,190 ppm), which corresponds to an enhancement in the rate of phosgene production of ∼227% with respect to the phosgene flow rate observed in the absence of an incident bromine co-feed. A reaction model is proposed to account for the experimental observables, where BrCl(g) is highlighted as a significant intermediate. Specifically, enhanced rates of phosgene production are associated with the dissociative adsorption of BrCl(g) that indirectly increases the pool of Cl(ad) available for reaction.

Bromine chloride as an oxidant to improve elemental mercury removal from coal-fired flue gas

The equilibria and kinetics of the reaction between bromine (Br(2)) and chlorine (Cl(2)) to form bromine chloride (BrCl) at various temperatures were determined. BrCl was employed to oxidize elemental mercury (Hg(0)) under simulated flue gas conditions. The removal of Hg(0) from the gas phase by a homogeneous gas-phase oxidation reaction and the heterogeneous reactions involving flyash were investigated. The second-order gas phase rate constant was determined to be 2.3(+/-0.2) x 10(-17) cm(3).molecules(-1).s(-1) at 373K. The reaction of Hg(0)/BrCl was significantly accelerated in the presence of flyash, and the estimated Hg(0) removal efficiency in the presence of 0.6 ppmv BrCl and 20 g/m(3) flyash was up to 90%. Unexpectedly, the major product was found to be HgCl(2), rather than HgBr(2), indicating that bromine in part acted as the accelerant in Hg(0) oxidation in BrCl/Br(2)/Cl(2) system by facilitating the formation of intermediates. As a result, bromine consumption is much less than if only bromine gas is utilized alone. These results were helpful not only for understanding the mechanism of Hg(0) removal in coal-fired flue gas but also in any atmosphere in which bromine and chlorine species coexist.

Chemically Accurate Thermochemistry of Cadmium: An ab Initio Study of Cd + XY (X = H, O, Cl, Br; Y = Cl, Br)

Using a composite coupled cluster method employing sequences of correlation consistent basis sets for complete basis set (CBS) extrapolations and with explicit treatment of core-valence correlation and scalar and spin-orbit relativistic effects, the 0 K enthalpies of a wide range of cadmium-halide reactions, namely, Cd + (HCl, HBr, ClO, BrO, Cl2, BrCl, Br2) have been determined to an estimated accuracy of +/-1 kcal/mol. In addition, accurate equilibrium geometries, harmonic frequencies, and dissociation energies have been calculated at the same level of theory for all the diatomic (e.g., CdH, CdO, CdCl, CdBr) and triatomic (CdHCl, CdHBr, CdClO, CdBrO, CdCl2, CdBrCl, CdBr2) species involved in these reactions, some for the very first time. Like their mercury analogues, all of the abstraction reactions are predicted to be endothermic, while the insertion reactions are strongly exothermic with the formation of stable linear, Cd-centric complexes. With the exception of CdH and the reactions involving this species, the present results for the remaining Cd-containing systems are believed to be the most accurate to date.

Imaging the dynamics of gas phase reactions

Ion imaging methods are making ever greater impact on studies of gas phase molecular reaction dynamics. This article traces the evolution of the technique, highlights some of the more important breakthroughs with regards to improving image resolution and in image processing and analysis methods, and then proceeds to illustrate some of the many applications to which the technique is now being applied--most notably in studies of molecular photodissociation and of bimolecular reaction dynamics.

Monte Carlo Simulation of Equilibrium Reactions at Vapor−Liquid Interfaces

Chemical reactions are known to behave differently, depending upon their local environment. While the interactions with neighboring molecules may alter both the kinetics of chemical reactions and the overall equilibrium conversion, we have performed simulations of the latter. The particular environment that we address is the vapor-liquid interface, since only a few, limited studies have explored the influence of an interface on equilibrium reaction behavior. Simple dimerization reactions are modeled, as well as more complex multicomponent reactions, using the reactive Monte Carlo (RxMC) simulation technique. We find that the conversion of a reaction can be markedly different at an interface as compared to the bulk vapor and liquid phases, and these trends are analyzed with respect to specific intermolecular interactions. In conjunction, we calculate the surface tension of the reacting fluids at the interface, which is found to have unusual scaling behavior, with respect to the system temperature.