Emissions control system and method

Abstract

A system comprising a fuel converter comprising a catalyst composition capable of converting a fuel into a selected one or both of a syngas reductant and a short chain hydrocarbon reductant, wherein the catalyst composition comprises: cracking sites that perform a cracking function when a temperature of an exhaust fluid is greater than a predetermined threshold temperature, wherein the cracking function converts long chain hydrocarbon molecules to short chain hydrocarbon molecules; and partial oxidation sites that perform a catalytic partial oxidation function when the temperature of the exhaust fluid is less than the predetermined threshold temperature, wherein the catalytic partial oxidation function oxidizes the fuel to produce the syngas reductant; and a selective catalytic reduction catalyst reactor in fluid communication with the fuel converter and the exhaust fluid.

1 . A system comprising:
 a fuel converter comprising a catalyst composition capable of converting a fuel into a selected one or both of a syngas reductant and a short chain hydrocarbon reductant, wherein the catalyst composition comprises:
 cracking sites that perform a cracking function when a temperature of an exhaust fluid is greater than a predetermined threshold temperature, wherein the cracking function converts long chain hydrocarbon molecules to short chain hydrocarbon molecules; and 
 partial oxidation sites that perform a catalytic partial oxidation function when the temperature of the exhaust fluid is less than the predetermined threshold temperature, wherein the catalytic partial oxidation function oxidizes the fuel to produce the syngas reductant; and 
   a selective catalytic reduction catalyst reactor in fluid communication with the fuel converter and the exhaust fluid.   
   
   
       2 . The system of  claim 1 , further comprising an engine in fluid communication with a fuel tank and the selective catalytic reduction catalyst reactor, wherein the engine is located downstream of the fuel tank and upstream of the selective catalytic reduction catalyst reactor. 
   
   
       3 . The system of  claim 1 , further comprising a controller operable to control a flow of the exhaust fluid to the fuel converter. 
   
   
       4 . The system of  claim 3 , wherein the controller permits the flow of the exhaust fluid to the fuel converter when the temperature of the exhaust fluid is less than the predetermined threshold temperature. 
   
   
       5 . The system of  claim 3 , wherein the control of exhaust fluid flow is effective to change an oxygen to carbon molar ratio in the fuel in the fuel converter. 
   
   
       6 . The system of  claim 1 , further comprising a controller operable to control the flow of fuel to the fuel converter and thus control the production of the syngas reductant and/or the short-chain hydrocarbon reductant. 
   
   
       7 . The system of  claim 1 , wherein the cracking sites comprise a zeolite and the partial oxidation sites comprise a dispersed noble metal. 
   
   
       8 . The system of  claim 1 , wherein the catalyst composition comprises a platinum group metal dispersed on a catalyst support. 
   
   
       9 . The system of  claim 8 , wherein the platinum group metal comprises platinum, rhodium, palladium, iridium, osmium, ruthenium, or a combination comprising at least one of the foregoing. 
   
   
       10 . The system of  claim 8 , wherein the catalyst composition comprises about 0.1 weight percent to about 20 weight percent of the platinum group metal. 
   
   
       11 . The system of  claim 9 , wherein the platinum group metal further comprises one or more base metals from Group VIII, Group IB, Group VB or Group VIB of the Periodic Table of Elements. 
   
   
       12 . The system of  claim 8 , wherein the catalyst support comprises a monolith, wherein the monolith comprises foam, metal foil, fibers, or a combination comprising at least one of the foregoing. 
   
   
       13 . The system of  claim 1 , wherein the catalyst composition is trimetallic. 
   
   
       14 . The system of  claim 13 , wherein the trimettalic catalyst composition is rhodium-platinum-iridium in proper stoichiometry. 
   
   
       15 . The system of  claim 13 , wherein the catalyst composition further comprises a promoter configured to enhance the dispersion of the platinum group metal. 
   
   
       16 . The system of  claim 15 , wherein the promoter comprises rhenium, rhodium, palladium, ruthenium, iridium, platinum, lanthanum, cerium, chromium, gallium, or a combination comprising at least one of the foregoing. 
   
   
       17 . The system of  claim 1 , wherein the syngas reductant and/or the short-chain hydrocarbon reductant control a nitrogen oxide content of the exhaust fluid in the selective catalytic reduction catalyst reactor. 
   
   
       18 . A vehicle or stationary generator employing the system of  claim 1 . 
   
   
       19 . A locomotive employing the system of  claim 1  on board. 
   
   
       20 . A method, comprising:
 determining a measured temperature of an exhaust fluid;   performing a catalytic partial oxidation of a fuel to a syngas reductant when the measured temperature is less than a predetermined threshold value, or   converting a long chain hydrocarbon molecules into a short chain hydrocarbon reductant, in the presence of a catalyst composition, when the measured temperature is greater than the predetermined threshold value;   reacting the syngas reductant and/or the short chain hydrocarbon reductant with the exhaust fluid in the presence of a selective catalytic reduction catalyst; and   controlling a concentration of a component of the exhaust fluid based on the measured temperature.   
   
   
       21 . The method of  claim 20 , wherein the converting occurs in a fuel converter, and wherein the fuel converter comprises a ratio of oxygen to carbon (O 2 /C) in a range of from about 0.10 to about 0.75. 
   
   
       22 . The method of  claim 20 , wherein controlling the concentration comprises reducing a nitrogen oxide content in the exhaust fluid. 
   
   
       23 . The method of  claim 20 , further comprising regenerating the catalyst composition by diverting a portion of the exhaust fluid to the catalyst composition when the measured temperature is less than the predetermined threshold value.