Ruthenium Catalyst NOx Reduction Selectivity
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Solution Overview
Problem
Current selective catalytic reduction (SCR) systems for NOx reduction in internal combustion engines are not efficient enough, particularly in achieving high selectivity and conversion of NOx to nitrogen using hydrogen and carbon monoxide as reductants.
Innovation Solution
A ruthenium-based catalyst supported on an inorganic oxide, such as Al2O3, is used in a dedicated exhaust gas recirculation system where carbon monoxide and hydrogen act as reductants to reduce NOx to nitrogen with a selectivity of greater than or equal to 90%, utilizing a configuration that includes a dedicated EGR cylinder and a ruthenium-based catalyst positioned in the exhaust gas recirculation loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional SCR systems are used for NOx reduction, then NOx conversion is achieved, but selectivity and conversion efficiency are insufficient
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by using ruthenium-based catalysts with specific inorganic supports (alumina, magnesia, or silica) and controlling the oxidation state of ruthenium. The catalyst maintains Ru in a partially oxidized state (RuO2) under reducing conditions, which is achieved by careful control of the reduction process and operating conditions. This parameter change enables high selectivity (≥90%) and conversion efficiency for NOx reduction to N2
Solution Approach 2:
The patent employs composite catalyst materials consisting of ruthenium metal particles supported on inorganic oxide materials (alumina, magnesia, or silica). This composite structure combines the catalytic activity of ruthenium with the structural stability and surface properties of the inorganic support, creating a material that maintains high selectivity and activity under the reducing conditions present in exhaust gases containing CO and H2
2Reliability
If ruthenium catalyst is used under reducing conditions, then catalytic activity is maintained, but ruthenium may be reduced to metallic form which affects performance
Solution Approach 1:
The patent applies beforehand cushioning by pre-oxidizing the ruthenium catalyst and controlling the reduction conditions to prevent complete reduction to metallic ruthenium. The inorganic support materials (alumina, magnesia, silica) are selected to provide structural stability and control the reduction environment. The catalyst is designed to maintain a partially oxidized state (RuO2) even under reducing conditions, cushioning against the adverse effect of complete reduction
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The ruthenium-based catalyst system achieves NOx reduction to nitrogen with a selectivity of 90% or higher, significantly improving upon existing SCR systems by maintaining the catalytically active form of ruthenium under reducing conditions, thus enhancing the efficiency of NOx conversion across a range of temperatures.
Implementation Method 1
A method for selective catalytic reduction of exhaust gases from hydrocarbon combustion comprising providing a ruthenium based catalyst on an inorganic support and introducing to the ruthenium based catalyst a mixture of an exhaust gas containing NOx in combination with carbon monoxide and hydrogen
Implementation Method 2
reducing the NOx to nitrogen wherein carbon monoxide and hydrogen act as reductants and the NOx is reduced to nitrogen at a selectivity of greater than or equal to 90%
Data Source
AI summary
The present disclosure is directed at a ruthenium based catalyst for NOx reduction. More specifically, ruthenium based catalysts are used for NOx reduction in an internal combustion engine to reduce NOX to nitrogen, at relatively high conversion and selectivity, using carbon monoxide and hydrogen as reductants. The ruthenium based catalyst has particular utility in exhaust gas recirculation such as in dedicated exhaust gas recirculation (D-EGR) systems.