Nitric Acid

Abstract

Nitric acid is a strong acid, a powerful oxidizing compound, and a nitrating agent. These properties make it an important basic chemical compound that is used in the production of many important chemicals such as fertilizers, polyurethanes, organic chemical intermediates, pharmaceuticals, synthetic fibers, dyes, insecticides, fungicides, and explosives. Nitric acid is produced through the oxidation of ammonia to nitrogen oxides, which are then absorbed by water to produce nitric acid. Weak nitric acid processes produce nitric acid in the concentration range of 50–65 wt %. The two main types of weak acid process are the monopressure process and the dual‐pressure process. The monopressure process operates at either moderate (0.3–0.6 MPa) or high pressure (0.7–1.2 MPa). The dual‐pressure process performs the conversion of ammonia at atmospheric or moderate pressures (0.3–0.6 MPa) and the absorption of nitrogen oxides at high pressure (1.1–1.5 MPa). Nitrogen oxides in the tail gas leaving the process are reduced to below environmental regulatory limits by either extended absorption or catalytic abatement. Strong nitric acid of 98–99 wt % is produced by either extractive distillation or direct strong nitric acid process. The extractive distillation process uses either magnesium nitrate or sulfuric acid as a dehydrating agent to surpass the maximum boiling azeotrope of nitric acid. The direct strong nitric acid process is similar to the weak nitric acid process, but has additional processing steps that bypass the azeotrope to produce strong nitric acid. Information on the chemical and physical properties, manufacturing processes, materials of construction, uses, safety and health, analytical methods, and producers of nitric acid is included.

Effective Utilization of the Catalytically Active Phase: NH3 Oxidation Over Unsupported and Supported Co3O4

“…This process typically uses platinum-rhodium gauze as a catalyst for the ammonia oxidation being active (conversions in excess of 90 % can easily be achieved at temperatures between 810 and 940°C and pressures between 1 and 10 bar) and highly selective [1]. Higher reaction pressures are used for the production of concentrated nitric acid, whereas low pressures can be used for the production of dilute nitric acid.…”

“…Operation at high pressure comes at the cost of lower NO yield and shorter catalyst life time [2]. In particular, the platinum loss during the process due to platinum volatilization contributes to the high operating costs [1].…”