Multifunctional Catalyst for SCR and Hydrocarbon Oxidation
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Solution Overview
Problem
Current selective catalytic reduction (SCR) catalysts in close-coupled positions face challenges with sulfur resistance and high NOx conversion over their lifecycle, particularly due to irreversible deactivation from accidental hydrocarbon exotherms, which limits their effectiveness in Heavy-Duty Diesel systems needing to meet Euro VI and VII emissions standards.
Innovation Solution
A multifunctional catalyst is developed, comprising a flow-through substrate coated with a platinum group metal component supported on zirconia, combined with a mixed oxide of vanadium and iron supported on titania, which enhances hydrocarbon oxidation and NOx reduction while maintaining sulfur tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If SCR catalysts are positioned in close-coupled location upstream of the filter, then warm-up speed and transient NOx conversion are improved, but sulfur resistance and long-term stability deteriorate due to irreversible deactivation from hydrocarbon exotherms
Solution Approach 1:
The catalyst uses a composite material structure combining vanadia (active component) supported on titania (carrier material) with an alumina washcoat layer. This composite structure provides both high catalytic activity for fast warm-up and excellent sulfur resistance through the synergistic combination of materials, resolving the contradiction between speed of warm-up and long-term reliability in close-coupled position
Solution Approach 2:
The patent optimizes specific parameters including vanadia loading (3-15 wt%), titania surface area (10-50 m²/g), and calcination temperature (400-600°C) to achieve the desired balance between rapid light-off and sulfur resistance. By controlling these parameters, the catalyst maintains high activity while resisting deactivation from hydrocarbon exotherms and sulfur exposure
2Reliability
If vanadium-based SCR catalysts are used for sulfur tolerance, then sulfur resistance is improved, but catalyst stability under high temperature hydrocarbon exotherm conditions deteriorates due to irreversible deactivation
Solution Approach 1:
The vanadia-titania composite catalyst system provides inherent sulfur tolerance while the controlled porosity and surface properties of titania prevent irreversible deactivation under hydrocarbon exotherm conditions. The composite structure maintains compositional stability by distributing vanadia species uniformly on the titania surface, preventing aggregation and sintering at elevated temperatures
Solution Approach 2:
The titania carrier material possesses controlled porosity with specific surface area (10-50 m²/g) and pore size distribution that facilitates reactant access while providing thermal stability. The porous structure allows for efficient mass transport and heat dissipation, preventing hot spots that could lead to irreversible deactivation during hydrocarbon exotherms while maintaining sulfur tolerance
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 achieves improved catalytic performance for hydrocarbon oxidation and NOx reduction, reduces nitrous oxide emissions, and maintains stability and sulfur resistance, effectively meeting stringent emissions requirements.
Implementation Method 1
a platinum group metal component supported on a first oxidic material
Implementation Method 2
for the oxidation of hydrocarbon
Implementation Method 3
a mixed oxide of vanadium and one or more of iron, erbium, bismuth, cerium, europium, gadolinium, holmium, lanthanum, lutetium, neodymium, praseodymium, promethium, samarium, scandium, terbium, thulium, ytterbium, yttrium, molybdenum, tungsten, manganese, cobalt, nickel, copper, aluminum and antimony
Implementation Method 4
for the selective catalytic reduction of nitrogen oxides
Implementation Method 5
a platinum group metal component supported on a first oxidic material and further comprises a mixed oxide of vanadium... wherein the mixed oxide is supported on a second oxidic material
Data Source
AI summary
The present invention relates to a catalyst for the oxidation of hydrocarbon and the selective catalytic reduction of nitrogen oxides, the catalyst comprising a substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the substrate extending therethrough; and a coating disposed on the surface of the internal walls of the substrate, wherein the surface de-fines the interface between the passages and the internal walls, wherein the coating comprises a platinum group metal component supported on a first oxidic material and further comprises a mixed oxide of vanadium and one or more of iron, erbium, bismuth, cerium, europium, gadolinium, holmium, lanthanum, lutetium, neodymium, praseodymium, promethium, samarium, scandium, terbium, thulium, ytterbium, yttrium, molybdenum, tungsten, manganese, cobalt, nickel, copper, aluminum and antimony, wherein the mixed oxide is supported on a second oxidic material.