Nitration of Benzene at High-Concentrations of Sulfuric Acid

Abstract

Nitration of benzene was carried out at high-concentrations of sulfuric acid (77-92 %) in a 1 L batch reactor with the objective to study the conversion of the reactants, yield and distribution of the products. A low speed of stirring (110 rpm) was employed in these studies to maintain the liquid-liquid interface flat, which facilitated the analysis. The conversion of reactants and the yield of products were good even at room temperature and at low stirring-speed. The conversion of nitric acid showed a steady increase with the increase in concentration of sulfuric acid. This increase was attributed to the increase in conversion of nitric acid to nitronium ion, whose equilibrium was shifted to the lower concentrations of H₂SO₄ in presence of the reactants. It was observed that a significant amount of 1,3-dinitrobenzene formed when the sulfuric acid concentration was greater than 85 %. The formation of 1,3-dinitrobenzene increased with the increase in concentration of sulfuric acid and increase in temperature. The conversion of benzene and the yield of nitrobenzene decreased accordingly.