Adipic acid formation by oxidation of cyclohexanol and cyclohexanone with nitric acid: Measurements in a continuous stirred tank reactor reactor stability

Abstract

The reaction kinetics of the oxidation previously measured in batch experiments are completely confirmed by experiments carried out in a continuous stirred tank reactor, both during steady and unsteady operation (starting-up). The measurements have furnished some supplementary data about the rate of by-product formation and about the influence of the NH 4VO 3 and Cu(NO 3) 2 catalysts. The stability of the reactor is highly dependent on the concentration of the nitrous acid, which is initially formed during the conversion of cyclohexanol and is partially consumed in the course of the reaction. The production and consumption of HNO 2 can be controlled separately, and as HNO 2 is absolutely necessary for effecting the oxidation, conditions can be created under which the reaction in a continuous reactor dies out. After the analogy of the term “autothermic reactor”, the reactor we are concerned with here may be called an “autoconcentrative” reactor in which, in general, two stable steady states are possible: (1) HNO 2 concentration = O, conversion = O, and (2) both the conversion and the HNO 2 concentration have a fixed value. In between these two states there is mostly an unsteady state, characterized by an HNO 2 concentration which may be called the “ignition concentration”.