Mesoporous Catalyst for NOx Reduction and Sulfur Desulfation
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Solution Overview
Problem
Current catalysts for reducing NOx emissions in exhaust gas streams are limited by their temperature range and efficiency, particularly for lean burn engines, which produce higher NOx concentrations and are affected by sulfur species, requiring complex regeneration processes.
Innovation Solution
A catalyst composition with a catalytic metal secured to a mesoporous substrate, where sulfur species are oxidized and desulfated using a regeneration fuel and heat source, allowing for NOx reduction across a wide temperature range without altering the air-fuel ratio and facilitating simultaneous regeneration of diesel particulate filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalytic converter is used to reduce NOx emissions in lean burn engines, then NOx conversion is achieved, but sulfur species accumulate on the catalyst causing deactivation
Solution Approach 1:
The patent applies preliminary action by performing desulfation regeneration before the catalyst becomes completely deactivated. The control system monitors catalyst performance and initiates regeneration cycles proactively, introducing hydrocarbon fuel and oxygen to oxidize sulfur species before they fully poison the catalyst sites, thereby maintaining continuous NOx conversion efficiency
Solution Approach 2:
The patent implements discarding and recovering by periodically discarding accumulated sulfur species through controlled oxidation during regeneration cycles. The sulfur is converted to sulfur dioxide and removed from the catalyst, allowing the catalyst to recover its NOx conversion capability without permanent deactivation
2Reliability
If the catalyst temperature is increased to improve NOx reduction, then conversion efficiency increases, but the temperature range for effective operation becomes more limited
Solution Approach 1:
The patent applies parameter changes by utilizing the exothermic oxidation of hydrocarbons and carbon monoxide on the catalyst surface to generate heat in situ. This self-heating mechanism raises the catalyst temperature to optimal levels for NOx reduction without requiring external heating, while the control system adjusts the air-fuel ratio and regeneration timing to maintain operation across varying temperature conditions
Solution Approach 2:
The patent implements periodic action through alternating between normal NOx reduction mode and regeneration mode. During regeneration, the catalyst is exposed to hydrocarbon-rich conditions that generate heat and oxidize sulfur, then returns to NOx reduction mode, creating periodic temperature and chemical environment changes that maintain both efficiency and adaptability
3Reliability
If a complex regeneration process is used to remove sulfur species, then catalyst performance is restored, but the system complexity increases
Solution Approach 1:
The patent applies self-service by enabling the catalyst to perform its own regeneration using exhaust gases and hydrocarbon fuel already present in the system. The control system simply needs to adjust the air-fuel ratio and timing, allowing the exothermic oxidation reactions to automatically generate the necessary heat and chemical environment for sulfur removal without external heating devices or complex intervention systems
Solution Approach 2:
The patent implements universality by designing the catalyst to perform multiple functions: NOx reduction during normal operation, self-heating through exothermic oxidation, and autonomous desulfation during regeneration. The same catalyst structure and active sites are used for all these functions, eliminating the need for separate regeneration equipment or additional catalyst components
4Loss of time
If the light-off time is reduced by preheating the catalyst, then emissions control improves, but the system requires additional energy input
Solution Approach 1:
The patent converts the harmful unburned hydrocarbons and carbon monoxide in the exhaust into a beneficial heating source. These components, which would otherwise be pollutants, are utilized during regeneration to generate exothermic heat that raises the catalyst temperature rapidly, reducing light-off time without requiring external energy input while simultaneously removing sulfur species
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 catalyst composition effectively reduces NOx emissions across a broader temperature range, maintains efficiency despite sulfur exposure, and enables simultaneous desulfation and particulate filter regeneration, improving overall engine emissions control.
Implementation Method 1
catalytic metal secured to a substrate... reduce NOx emissions
Implementation Method 2
oxidation catalysts... oxidation reactions occurring at the catalyst
Implementation Method 3
heat source positioned upstream relative to the catalytic converter that is activated when the injector mechanism is introducing the regeneration fuel into the exhaust stream to heat the temperature of the exhaust stream above a range of exhaust temperatures
Implementation Method 4
introducing into the exhaust stream, upstream from the catalytic converter a predetermined amount of a regeneration fuel for a resident time period in order to oxidize the sulfur species
Data Source
AI summary
A catalyst composition is provided that includes a catalytic metal secured to a substrate, and the substrate is mesoporous and has pores that are templated. A catalyst composition includes a catalytic metal secured to a mesoporous substrate. The mesoporous substrate is a reaction product of a reactive solution, a solvent, a modifier, and a templating agent. A method for controlling nitrous oxide emissions including the catalyst composition comprising introducing a regeneration fuel into an exhaust stream upstream relative to the catalyst composition and heating the exhaust stream upstream relative to the catalyst composition. When the regeneration fuel is introduced the air/fuel ratio λ of an air/fuel mixture of a lean burn exhaust is greater than 1.