Environmental Issues in AA Production

The maj or environmental concern for nitric acid oxidation of either cyclohexanol or the KA Oil is the emission of the greenhouse gas nitrous oxide, N2O. Theemission factor is estimated to be around 300 kg of N2O per ton of AA indeed, the real value is between 260 and 330 (around 0.75-1.2 mol of N2O per mole of AA), depending on the amount of catalyst used and the KA Oil composition. For a global AA production of 3.0 M-tonyr, the total amount of N2O produced is estimated to be about 0.9 M-tonyr. However, nowadays less than 5% of total emission of N2O into the atmosphere is from anthropogenic origin, and of this 5% only a small fraction is due to AA production, because almost all the AA producers have installed N2O decomposition units. 

HNO2 is an intermediate of the reduction of nitric acid the surplus HNO2 produced by various reactions eventually decomposes into NO and NO2, and leaves the reactors in the gas stream. However, NO and NO2 (about 1 mol NOx per mole of AA) can be almost completely recovered, yielding a nitric acid solution that can be reused in the oxidation process. Indeed, some companies simply co-feed the off-gas of the AA plant to a large existing nitric acid plant. 

Low temperature and pressure are the key factors in the adsorption process (owing to the poor solubility of nitrogen oxides, NO in particular), since they contribute considerably to operative and investment costs. Nowadays it is possible, with a proper 

To evaluate the impact of different greenhouse gases, the IPCC introduced the global warming potential [8c[ (GWP), which is a quantified measure of the impact of each gas compared to carbon dioxide, used as a reference, in a defined time and per unit of mass. The relationship between gigagrams of gas and teragrams of equivalent CO2 is the following  

According to this criterion, considering the lifetime of N2O in the atmosphere and a period of 100 years, it has a GWP 310-times higher than that of CO2. 

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