Dosing method and apparatus for reductant urea solutions with catalyst precursors to assist selective catalytic reduction
AssigneeSouthwest Research Institute
InventorsCary A. Henry, Ryan C. Hartley
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Abstract
The present disclosure is directed at a dosing method and apparatus for treatment of reductant urea solutions with water soluble organometallic catalyst precursors which convert to active catalyst compounds in diesel exhaust gas systems. The active catalysts then promote hydrolysis of isocyanic acid into ammonia and/or decomposition of relatively high molecular weight deposits which deposits may otherwise reduce selective catalytic reduction efficiency.
Claims24
A method of reducing oxides of nitrogen in a diesel engine producing diesel exhaust comprising:
- providing a first reservoir of diesel emission fluid containing an aqueous based urea solution;
- providing a second reservoir of a catalyst precursor containing an organometallic compound dissolved in water;
- mixing said diesel emission fluid and said water soluble organometallic compound and introducing said mixture into said diesel exhaust wherein the urea converts to ammonia and isocyanic acid and said catalyst precursor converts to a catalyst;
- converting the isocyanic acid to ammonia with said catalyst wherein the ammonia is provided to a selective catalytic reduction system and reacts with the oxides of nitrogen and provides nitrogen and water.
A method of reducing oxides of nitrogen in a diesel engine producing diesel exhaust comprising:
- providing a first reservoir of diesel emission fluid containing an aqueous based urea solution;
- providing a second reservoir of a catalyst precursor containing an organo-titanium compound dissolved in water;
- mixing said diesel emissions fluid and said organo-titanium compound dissolved in water wherein the urea converts to ammonia and isocyanic acid and said organo-titanium compound converts to titanium dioxide catalyst;
- wherein said titanium dioxide catalyst converts said isocyanic acid to ammonia;
- and
- said selective catalyst reduction system contains one or more compounds of biuret, triuret, cyanuric acid, ammelide, ammeline or melamine and said titanium dioxide catalyst promotes thermal decomposition and removal of said one or more compounds from said selective catalytic reduction system.
An exhaust after-treatment system comprising:
- a first reservoir of diesel emission fluid containing an aqueous based urea solution;
- a second reservoir of a catalyst precursor containing an organometallic compound dissolved in water;
- a selective catalyst reduction system configured to convert urea to ammonia and reduce NOx to nitrogen and water;
- and
- a dosing unit comprising a liquid injector that combines and mixes said diesel emission fluid from said first reservoir and said catalyst precursor from said second reservoir wherein said dosing unit is configured to inject said mixture into said selective catalyst reduction system.
Dependencies are inferred from the claim text.