Acidic Hydrocarbon Trap for Cold-Start Emission Reduction
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Solution Overview
Problem
Current hydrocarbon traps using zeolites are ineffective in absorbing low molecular weight hydrocarbons during cold-start engine emissions due to limited thermal durability and early release of stored emissions at lower temperatures, which reduces their absorptive capacity and requires higher conversion temperatures.
Innovation Solution
A hydrocarbon trap incorporating acidic absorption materials with multiple Bronsted acid sites, such as alumina, silica-alumina, sulfated zirconia, or silica-supported heteropolyacids, enhances the absorption and thermal durability by maintaining hydrocarbon retention until sufficient temperatures for catalytic conversion are reached, eliminating the need for added metal ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If zeolites are used as absorption materials in hydrocarbon traps, then hydrocarbon absorption capacity is improved, but thermal durability deteriorates due to alumina leaching at high temperatures
Solution Approach 1:
The patent extracts and removes alumina from the zeolite structure to create alumina-free zeolite absorption materials. This eliminates the source of thermal degradation while preserving the hydrocarbon absorption capacity through alternative zeolite compositions and structures that do not contain leachable alumina.
Solution Approach 2:
The patent employs composite material strategies by combining alumina-free zeolites with other materials that provide both absorption capacity and thermal stability. The composite structure maintains hydrocarbon trapping effectiveness while resisting thermal degradation through synergistic material properties.
2Reliability
If zeolites with high SiO2/Al2O3 ratio are used, then thermal durability is improved, but absorptive capacity for low molecular weight hydrocarbons deteriorates
Solution Approach 1:
The patent changes the compositional parameters of the zeolite material by precisely controlling SiO2/Al2O3 ratios, crystal structure types, and pore size distributions. These parameter adjustments optimize both thermal durability and absorptive capacity for low molecular weight hydrocarbons simultaneously.
Solution Approach 2:
The patent applies local quality principles by creating zeolite structures with specific regional characteristics - certain zones optimized for high thermal stability while other regions provide enhanced absorption sites for low molecular weight hydrocarbons. This spatial differentiation of properties resolves the contradiction between durability and capacity.
3Productivity
If metal ions such as Cu, Fe, or Ag are added to enhance hydrocarbon absorption, then absorption efficiency is improved, but thermal durability and storage stability deteriorate
Solution Approach 1:
The patent removes metal ion additives from the hydrocarbon trap system entirely. Instead of adding Cu, Fe, or Ag ions that cause thermal degradation, the invention achieves enhanced absorption efficiency through intrinsic zeolite properties, alternative absorption materials, or organic modifiers that do not compromise thermal stability.
4Productivity
If conventional zeolites are used during cold-start, then hydrocarbon trapping is attempted, but low molecular weight hydrocarbons are released at temperatures below catalytic conversion requirements
Solution Approach 1:
The patent changes the thermal parameters of the absorption materials by selecting zeolite types with higher thermal stability and adjusting compositional parameters to raise the desorption temperature of low molecular weight hydrocarbons. This ensures hydrocarbons are retained until catalytic conversion temperatures are achieved.
Solution Approach 2:
The patent applies preliminary action by pre-heating the hydrocarbon trap or pre-activating the catalytic converter before cold-start conditions occur. This preliminary thermal preparation ensures that when low molecular weight hydrocarbons are trapped, the system is already at sufficient temperature to prevent premature release and enable immediate catalytic conversion.
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 hydrocarbon trap effectively absorbs and retains low molecular weight hydrocarbons until elevated temperatures, ensuring efficient catalytic conversion and prolonged thermal durability, thereby reducing cold-start emissions and extending the trap's lifespan.
Implementation Method 1
Hydrocarbon traps have been developed for reducing emissions during cold-start by trapping hydrocarbon (HC) emissions at low temperatures
Implementation Method 2
releasing them at sufficiently elevated temperatures through a catalyzed overlayer
Implementation Method 3
passing the emissions to downstream catalysts for complete oxidation
Data Source
AI summary
A hydrocarbon trap is provided for reducing cold-start hydrocarbon emissions. The trap contains an acidic absorption material for improving absorption of low molecular weight hydrocarbons. The acidic absorption materials may be used either alone or in combination with zeolites which are integrated into and/or supported on a monolithic substrate. The hydrocarbon trap may be positioned in the exhaust gas passage of a vehicle such that hydrocarbons are adsorbed on the trap and stored until the engine and exhaust reach a sufficient temperature for desorption.