Bromine is used in a wide range of industries. For example, bromine is used in the manufacture of flameproofing agents, 1,2-dibromoethane (CH2BrCH2Br) (which is used as a petrol additive to prevent lead being deposited in cylinders), compounds used in photography (e.g. silver bromide, AgBr, which is the light sensitive material in film), dyestuffs and drugs; in the analytical laboratory in testing for unsaturation in organic compounds, where bromine adds across the multiple bonds of unsaturated compounds, as a disinfectant; and in making fumigants, water purification compounds, dyes, medicinals; and sanitizers. Bromine can be produced by oxidation of bromides using hydrogen peroxide as the oxidant. For example, the following reaction is suitable: H2O2+2HBrBr2+2H2O (Reaction (1)). Bromine can also be produced by oxidation of bromides using chlorine as the oxidant. For example, the following reaction is suitable: 2NaBr+Cl2Br2+2NaCl (Reaction (2)).
U.S. Pat. No. 5,266,295 describes use of a strong acid, such as sulfuric or phosphoric acid, to improve effectiveness when hydrogen bromide is oxidized to bromine using hydrogen peroxide as the oxidant. However, process economics are affected by the addition of an acid; and in some cases an add source is not readily available. Each of Reactions (1) and (2) could benefit from the addition of catalysts to increase the percent conversion of bromide to bromine. Ammonium molybdate ((NH4+)2MoO4−) is a known oxidation catalyst to allow iodometric titration of H2O2. However, NH4+ is not a cation of choice for use as an additive in a commercial bromine tower.
Thus in spite of currently available technologies, a need remains for commercially feasible methods that provide increased percent conversion when oxidizing bromides to produce bromine, and catalysts for use therein.