Vanadium SCR Catalyst with Promoter Oxides for Low-Temperature NOx Conversion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Vanadium-based selective catalytic reduction (SCR) catalysts face challenges in achieving high NOx conversion at low temperatures while maintaining thermal stability, as increasing vanadia loading compromises thermal stability and Cu-zeolite based SCR catalysts offer better performance only at high temperatures.
Innovation Solution
A vanadium-based SCR catalyst with a coating comprising vanadium oxide supported on titania, mixed with oxides of iron, erbium, bismuth, and antimony, and impregnated with tungsten or silicon oxide, providing enhanced NOx conversion and thermal stability across a range of temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If vanadia loading is increased to improve low temperature deNOx performance, then NOx conversion at low temperatures is improved, but thermal stability during aging deteriorates
Solution Approach 1:
The patent uses a composite material system consisting of vanadium oxide dispersed on a titania support, with additional metal oxides (WO3, SiO2, Nb2O5) as promoters. This composite structure allows the vanadium to provide low-temperature deNOx activity while the titania support and promoter oxides maintain thermal stability during aging, resolving the contradiction between improving low-temperature performance and maintaining thermal stability.
Solution Approach 2:
The patent optimizes the composition parameters of the catalyst, specifically controlling the weight ratios of vanadium oxide to titania (0.5-10%), and the amounts of promoter oxides (WO3: 0.1-5%, SiO2: 0.1-5%, Nb2O5: 0.1-5%). By precisely adjusting these compositional parameters, the catalyst achieves both high low-temperature deNOx conversion and maintained thermal stability after aging.
2Stability of the object's composition
If vanadium-based SCR catalysts are used to achieve thermal stability, then thermal stability is maintained, but low temperature deNOx performance deteriorates compared to Cu-zeolite catalysts
Solution Approach 1:
The patent modifies the compositional parameters of traditional vanadium-based catalysts by adding specific promoter oxides (WO3, SiO2, Nb2O5) in optimized amounts. These compositional changes enable the catalyst to achieve low-temperature deNOx conversion performance comparable to Cu-zeolite catalysts while retaining the inherent thermal stability of vanadium-based systems.
Solution Approach 2:
The promoter oxides (WO3, SiO2, Nb2O5) act as intermediaries that facilitate low-temperature deNOx reactions on the vanadium-titania catalyst surface. These intermediary substances enable the catalyst to perform low-temperature conversions effectively without compromising the thermal stability provided by the vanadium-titania base structure.
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 high NOx conversion at low temperatures while maintaining or improving thermal stability, outperforming traditional vanadium-based SCR catalysts and comparable to Cu-zeolite based catalysts at higher temperatures.
Implementation Method 1
selective catalytic reduction catalyst for the treatment of an exhaust gas of a diesel engine
Implementation Method 2
maintaining or increasing its thermal stability
Data Source
AI summary
The present invention relates to a selective catalytic reduction catalyst for the treatment of an exhaust gas of a diesel engine comprising (i) a flow-through 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 flow-through substrate extending therethrough; (II) a coating disposed on the surface of the internal walls of the substrate, where-in the surface defines the interface between the passages and the internal walls, wherein the coating comprises a vanadium oxide supported on an oxidic material comprising titania, 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.