The use of a steady state flow reactor in the study of rapid gas phase reactions

"The demonstration of the feasibility of rocket propelled devices for various purposes within the past few years has initiated an intensive search for suitable reactants for use as rocket fuels. Consequently, the investigation of the properties of chemical reactions which rapidly liberate large quantities of energy has assumed major importance. In order that such reactions may be adapted to practical use as rocket propellants knowledge of the characteristics of these reactions is required. Properties such as+ the mechanism of the reaction, the speed of the reaction under varied conditions of temperature, pressure and concentrations, the conditions required for the initiation of the reaction, and the energy to mass ratio of the reaction system are of prime importance.A reaction typical of the type used as rocket propellants, the reaction between ammonia and nitrogen dioxide, was selected for investigation at the Missouri School of Mines and Metallurgy. This particular reaction was chosen because of the ready availability of the materials commercially, their relatively low cost, the ease and safety of their storage, their high theoretical heat of reaction and their rapid rate of reaction in the gas phase.Crocker instigated the study of the reaction using a constant volume, constant temperature reactor, following the reaction by pressure measurements and determining the probable net reaction by analysis of the products of the completed reaction. Burch and Dillender carried on an extension of this work using similar methods. This method proved inadequate in that the actual temperatures of the reaction at the observed pressures were not known. Therefore, little could be determined of either the order of reaction or of the reaction velocity constant.Burch further explored the possibilities of following the progress of the reaction optically in a continuous flow system- the reactants being diluted with an inert gas to minimize the temperature rise during the reaction and the progress of the reaction followed by observation of the changes in transmittancy of the colored gas NO₂. It was found that the solid substances formed in the reaction, even at very low concentrations, obscured the optical measurements and this method for following the reaction proved infeasible.In view of the above it was decided to approach the problem in a different manner. It was felt that an essentially adiabatic, continuous flow reactor operating at a steady state would permit use of the high heat of reaction for following the progress of the reaction. By operating at steady state temperature conditions the reaction progress could be followed by observation of temperatures at specific distances in the reactor. Time intervals of contact of the reactants could be determined from the distance and rate of flow in the reactor and from this information the reaction velocity constant calculated.This study concerns the design of a reactor and its accessories to achieve this end. Further to develop a method for determination of the reaction velocity constant for the gas phase reaction between ammonia and nitrogen dioxide at atmospheric pressure from the data obtained"--Introduction, pages 1-3.