NOx Catalyst with Tungsten Oxide for High-Temperature Exhaust
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Solution Overview
Problem
Conventional NOx removal catalysts face challenges in maintaining high-temperature NOx removal performance above 500°C, as the denitration reaction efficiency decreases due to ammonia oxidation, and existing carriers like titanium oxide do not effectively support tungsten oxide at elevated temperatures.
Innovation Solution
A NOx removal catalyst powder is developed with a complex oxide carrier formed from zirconium or silica compounds, where tungsten oxide is supported and fired at 650°C, and sulfate radicals are introduced to enhance the catalyst's surface area and bonding strength, maintaining performance even at 500°C or higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional NOx removal catalyst is used at high temperatures (450°C or higher), then the denitration reaction can proceed, but ammonia oxidation occurs instead of reduction, causing NOx removal performance to decrease
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst by incorporating specific metal oxides (V2O5, MoO3, WO3) in optimized ratios and controlling the sulfate content (0.1-5.0 wt%) to shift the reaction pathway from ammonia oxidation to selective catalytic reduction, enabling effective NOx removal at high temperatures
Solution Approach 2:
The patent creates a composite catalyst material combining multiple metal oxides (vanadium, molybdenum, tungsten) with sulfate components on a silica carrier, where each component contributes specific properties: V2O5 provides catalytic activity, MoO3/WO3 enhance thermal stability, and sulfate prevents ammonia oxidation, achieving synergistic effect at high temperatures
2Temperature
If the temperature is increased to 500°C or higher for gas turbine outlet flue gas processing, then more complete combustion is achieved, but the reducing agent becomes insufficient and the conventional reduction process cannot be applied
Solution Approach 1:
The patent modifies the catalyst's chemical composition by incorporating high-temperature stable metal oxides (MoO3, WO3) and controlling sulfate content to maintain catalytic activity and prevent ammonia oxidation at temperatures of 500°C and above, enabling the reduction process to be applied to gas turbine outlet flue gas
Solution Approach 2:
The patent creates localized active sites with specific metal oxide clusters and sulfate distributions on the catalyst surface, where V2O5-SO4 complexes provide acid sites for NH3 adsorption while MoO3/WO3 regions maintain reduction activity at high temperatures, achieving spatial functional differentiation
3Device complexity
If tungsten oxide is simply supported on titanium oxide carrier, then the catalyst structure is simple, but the catalyst activity is limited and denitration reaction cannot be promoted efficiently
Solution Approach 1:
The patent replaces simple TiO2 carrier with a composite system containing V2O5, MoO3, and WO3 metal oxides with sulfate components, where each material contributes specific functions: V2O5 provides catalytic centers, MoO3 enhances thermal stability, WO3 improves resistance to volatilization, and sulfate prevents ammonia oxidation, achieving high denitration efficiency through material synergy
Solution Approach 2:
The patent merges multiple metal oxide components (V2O5, MoO3, WO3) and sulfate functionalities into a single integrated catalyst system, where the components work synergistically to provide both high catalytic activity and thermal stability, resolving the limitation of simple supported structures
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 maintains high NOx removal efficiency and prevents ammonia decomposition, ensuring effective denitration at elevated temperatures by optimizing the support quantity and structure of tungsten oxide on the carrier, thereby extending the catalyst's operational temperature range.
Implementation Method 1
a NOx removal catalyst for high-temperature flue gas which contains nitrogen oxide, and more particularly relates to a NOx removal catalyst for high-temperature gas discharged from a thermal power plant, a gas turbine or the like
Implementation Method 2
sulfate radicals are introduced to enhance the catalyst's surface area and bonding strength, maintaining performance even at 500°C or higher
Implementation Method 3
when a temperature becomes as high as 450°C or higher, an oxidation reaction of NH3 itself makes progress according to following equation (2) or equation (3)
Data Source
AI summary
A NOx removal catalyst for high-temperature flue gas according to the present invention is a NOx removal catalyst for high-temperature flue gas that contains nitrogen oxide in which tungsten oxide with the number of molecular layers of tungsten oxide (WO3) being five or less is supported on a complex oxide carrier containing titanium oxide. Even when high-temperature denitration is continued, a bonding force with a carrier of WO3 can be properly maintained and volatilization can be suppressed while maintaining a high NOx removal performance. For example, the NOx removal catalyst is particularly suitable for reducing and removing nitrogen oxide contained in high-temperature gas discharged from a thermal power plant and a high-temperature boiler.