Ternary HNO₃–H₂SO₄–H₂O Mixtures: A Simplified Approach for the Calculation of the Equilibrium Composition

Abstract

Concentrated ternary mixture of nitric acid, sulfuric acid, and water are often used in the chemical industry for a wide range of applications. Among these, nitrations of organic substrates are the most common. Nevertheless, there is still a poor understanding of speciation of the acids in the mixtures, and different simplified or semiempirical approaches have been found in the literature to model nitration kinetics by mixed acids. Most of the found investigations are relevant in restricted ranges of experimental conditions, resulting in a fragmentary vision. In this work, most of the approaches found in the literature were reviewed in order to define their limits of validity, and new empirical equations for the estimation of nitronium ion concentration are proposed. Moreover, on the basis of original experimental data, a simplified model is proposed to calculate the dissociation of acids at varying experimental conditions, and the main assumptions reported in the literature were verified. Adopted simplifying assumptions were verified at sulfuric acid concentrations higher than 2.1 mol•L −1 and nitric acid concentrations ranging from 2.0 to 11 mol•L −1 .

Determination of the kinetics of chlorobenzene nitration using a homogeneously continuous microflow

“…A nitrating agent is a macroscopic concept, and there are numerous ions and groups in its system. For instance, there are NO 2 + , NO 3 − and unionized, molecular nitric acid in mixed acids 37 . It can be seen from the structural formula of nitric acid that the most easily broken bonds are the H‐O bond and N‐O bond, by which H + and NO 2 + are generated via acidic ionization and basic ionization, respectively.…”

Reaction of Organic Matter with Nitronium Ion as a Source of Organic Nitrate Esters in Proxies for Organic Aerosols

“…36 First, 10 mg of the humic or fulvic acid sample was placed in a 15 mL centrifuge tube and dissolved in 0.1 mL of water. To this mixture was added 0.05 mL of concentrated (90 wt %) HNO 3 to bring the approximate concentration of HNO 3 in the reaction mixture to 7 M. The following speciation of HNO 3 in this solution was estimated using the method of Russo et al: 28 + . The tubes were then capped tightly with Teflon-covered stoppers and gently agitated in a vortexer at 150 rpm for 3 days.…”

“…26 For simplicity we will refer to nitronium as NO 2 + , although it is more accurately described by its hydrated form. 24 From Russo et al, 28 the expected NO 2 + concentrations derived from N 2 O 5 uptake are on the order of 10 −9 to 10 −11 M under typical aerosol conditions. At low pH conditions, the reverse of reactions R7 and R6 are promoted, leading to a larger budget of NO 2 + and N 2 O 5 .…”

“…From Russo et al, the expected NO 2 + concentrations derived from N 2 O 5 uptake are on the order of 10 –9 to 10 –11 M under typical aerosol conditions. At low pH conditions, the reverse of reactions and are promoted, leading to a larger budget of NO 2 + and N 2 O 5 .…”

Determination of the kinetics of chlorobenzene nitration using a homogeneously continuous microflow

“…For instance, there are , and unionized, molecular nitric acid in mixed acids. [37][38][39] It can be seen from the structural formula of nitric acid that the most easily broken bonds are the H-O bond and N-O bond, by which H + and are generated via acidic ionization and basic ionization, respectively. Sulfuric acid is referred to as a nitration activator.…”