Hydrogen peroxide critical pressure

Values reproduced or converted from a tabulation by Tsykalo and Tabacbnikov in V A. Rabinovich (ed.), Theimophysical Propeities of Gases and Liquids, Stan-dartov, Moscow, 1968 NBS-NSF transl. TT 69-55091, 1970. Tbe reader may be reminded that very pure hydrogen peroxide is very difficult to obtain owing to its decomposition or instability, c = critical point. Tbe FMC Corp., Philadelphia, PA tech. bull. 67, 1969 (100 pp.) contains an enthalpy-pressure diagram to 3000 psia, 1100 K. 

Early experiments in liquids were quite variable for many reasons. The conductivity technique, which was used in the gas phase to measure dose, was not applicable to the liquid phase. Reactions were measured using dissolved radium salts or radon gas as the ionization source. Some thought the chemistry was due to the reactions with radium however, it was soon recognized that it was the emitted rays that caused the decomposition. Both radium and radon could cause radiation damage. Because the radon would be partitioned between the gas and liquid phase, the amount of energy that was deposited in the liquid depended critically on the experimental conditions such as the pressure and amount of headspace above the liquid. In addition, because the sources were weak, long irradiation times were necessary and products, such as hydrogen peroxide, could decompose. 

Direct measurements have not been made, to my knowledge, regarding the lower limit of partial pressure of H2O in air necessary for formation of hydrogen peroxide. One can reason, however, that the limiting partial pressure ought to be the same as that necessary for a metal to corrode. Based on corrosion information, the critical lower limit for the partial pressure is more properly expressed in terms of relative humidity rather than absolute pressure. The critical relative humidity for corrosion is that which allows moisture to condense on the surface of a metal. This value, in turn, depends on the nature and concentration of hygroscopic impurities present both in the atmosphere and on the metal surface. For commercial steels in ordinary urban air, the critical relative humidity is about 50%, but for high purity metals in filtered air, the critical value is undoubtedly much lower. 

Gas— Utilized for systems that cannot withstand either the temperatures or pressures employed in steam sterilization. Critical parameters for sterilization are time, temperature, relative humidity, and gas concentration. Gases in widespread use include ethylene oxide, peracetic acid, and hydrogen peroxide. Gas sterilization is most often encountered... 

A batch SCWO unit is conceptually similar to a pressure cooker. Material to be destroyed is mixed with an oxidizer (such as hydrogen peroxide) and introduced into a pressure vessel, which is heated to a reaction temperature above the critical point of water (374°C, 3,204 psia) and then cooled. Organic materials are mineralized to produce carbon dioxide, nitrogen, and aqueous salts. 

Piqueras, C., Garcia-Serna, J. and Cocero, M. (2011). Estimation of lower flammability limits in high-pressure systems. Application to the direct synthesis of hydrogen peroxide using snpercritical and near-critical CO2 and air as diluents, J. Supercrit. Fluid, 56, pp. 33 40. 

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