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US 4,626,417 AGranted
Methods for chemically reducing nitrogen oxides
AssigneeUnion Oil Company of California
InventorDonald C. Young
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AssigneeUnion Oil Company of California
InventorDonald C. Young
Estimating the term…
Methods are provided for chemically reducing one or more oxides of nitrogen by contacting the nitrogen oxides with a composition containing a urea-sulfuric acid component having a urea-sulfuric acid molar ratio below 2. The urea-sulfuric acid component can be either solid or molten, or it can be dissolved in a suitable solvent. Particularly preferred compositions are those which have relatively low water concentrations and which are characterized by H.sub.2 O/(urea+H.sub.2 SO.sub.4) molar ratios below about 2.5. These methods can be employed to prevent or reduce the emission of nitrogen oxides from liquid systems and to convert nitrogen oxides contained in vapor streams to non-toxic materials, e.g. elemental nitrogen and water. Solutions of the urea-sulfuric acid components which are employed to remove nitrogen oxides from vapor streams may also contain surfactants which facilitate gas-liquid contacting.
A method for reducing an oxide of nitrogen which comprises contacting said oxide of nitrogen with a composition comprising urea and sulfuric acid in which the urea/sulfuric acid molar ratio is below 2 and wherein at least a portion of said urea and sulfuric acid is present as the monourea adduct of sulfuric acid.
A method for removing an oxide of nitrogen from a gas containing said oxide of nitrogen which method comprises contacting said gas with a composition comprising urea and sulfuric acid in which the urea/sulfuric acid molar ratio is below 2 and wherein at least a portion of said urea and sulfuric acid is present as the monourea adduct of sulfuric acid.
A method for reducing the emission of an oxide of nitrogen from a solution which otherwise emits said oxide of nitrogen, which method comprises maintaining in said solution urea and sulfuric acid in proportions corresponding to a urea/sulfuric acid molar ratio below 2 and wherein at least a portion of said urea and sulfuric acid is present as the monourea adduct of sulfuric acid.
A method for converting an oxide of nitrogen to molecular nitrogen, CO.sub.2 and water, which method comprises reacting said oxide of nitrogen with a composition comprising urea and sulfuric acid in which composition the molar ratio of said urea to said sulfuric acid is below 2 and wherein at least a portion of said urea and sulfuric acid is present as the monourea adduct of sulfuric acid.
A method for reducing an oxide of nitrogen, which method comprises contacting said oxide of nitrogen with a composition containing urea and sulfuric acid in which the molar ratio of said urea to said sulfuric acid is within the range of about 1 to about 2 and wherein at least a portion of said urea and sulfuric acid is present as the monourea adduct of sulfuric acid.
A method for reducing an oxide of nitrogen, which method comprises the step of contacting said oxide of nitrogen with a composition containing urea and sulfuric acid in which the molar ratio of said urea to said sulfuric acid is within the range of about 1 to about 2, and said urea and said sulfuric acid, in combination, constitute at least about 60 weight percent of said composition and wherein at least a portion of said urea and sulfuric acid is present as the monourea adduct of sulfuric acid.
A method for reducing an oxide of nitrogen, which method comprises contacting said oxide of nitrogen with a composition comprising urea and sulfuric acid in which the molar ratio of said urea to said sulfuric acid is below 2, and said composition is characterized by an H.sub.2 O/(urea+H.sub.2 SO.sub.4) molar ratio below 2.5 and wherein at least a portion of said urea and sulfuric acid is present as the monourea adduct of sulfuric acid.
A method for reducing an oxide of nitrogen, which method comprises the step of contacting said oxide of nitrogen with a composition comprising urea and sulfuric acid, in which composition the molar ratio of said urea to said sulfuric acid is below 2, said composition contains less than about 1 weight percent water based on the combined weight of said urea and said sulfuric acid, said urea and said sulfuric acid, in combination, constitute at least about 5 weight percent of said composition, and said oxide of nitrogen is contacted with said composition at a temperature of at least about 90.degree. C. and wherein at least a portion of said urea and sulfuric acid is present as the monourea adduct of sulfuric acid.
Dependencies are inferred from the claim text.