TiO2/ZrO2 Catalyst for NOx Reduction
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Solution Overview
Problem
Current SCR catalysts for reducing NOx emissions, particularly those using vanadium pentoxide, face challenges due to toxicity and volatility concerns, and existing alternatives like zeolite-supported transition metals are costly and limited in performance.
Innovation Solution
A porous TiO2/ZrO2 support material with a crystalline phase and an amorphous phase, comprising a molar ratio of titanium to zirconium between 60:40 to 95:5, and a small amount of titanium dioxide, is used to deposit active catalyst components like manganese, iron, or cerium, enhancing catalytic activity and selectivity without vanadium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If vanadium pentoxide is used as the active catalyst component, then catalytic activity for NOx reduction is improved, but toxicity and volatility concerns arise
Solution Approach 1:
The patent replaces toxic vanadium pentoxide with alternative metal oxides (manganese, iron, cerium) that are less toxic and more environmentally friendly. These alternative catalysts achieve comparable catalytic activity for NOx reduction without the harmful effects of vanadium, effectively substituting a harmful substance with a benign one.
2Object-affected harmful factors
If zeolite-supported transition metals are used as alternative catalysts, then toxicity is reduced, but cost increases significantly
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst support system by using titanium-zirconium mixed oxides with specific molar ratios (60:40 to 95:5) instead of conventional zeolite supports. This parameter change results in a catalyst that is both less toxic and more cost-effective, as the mixed oxide support is cheaper than zeolite while maintaining the desired catalytic performance.
3Productivity
If conventional SCR catalysts are used, then NOx removal efficiency is improved, but ammonia selectivity deteriorates at high temperatures
Solution Approach 1:
The patent employs a composite catalyst system consisting of multiple metal oxides (manganese, iron, and/or cerium) supported on titanium-zirconium mixed oxide. This composite material structure synergistically combines the properties of different metals to maintain high ammonia selectivity across a wide temperature range, preventing ammonia slip at high temperatures while preserving NOx removal efficiency.
4Productivity
If vanadium-based catalysts are used, then catalytic performance is improved, but N2O formation increases
Solution Approach 1:
The patent substitutes vanadium-based catalysts with alternative metal oxide catalysts (manganese, iron, cerium) that achieve comparable or superior catalytic performance for NOx reduction while significantly reducing nitrogen oxide (N2O) byproduct formation. This substitution eliminates the harmful side effect associated with vanadium catalysts.
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 catalysts exhibit superior NOx conversion at both low and high temperatures, improved ammonia selectivity, and reduced N2O formation, addressing the limitations of existing vanadium-based and zeolite-supported catalysts.
Implementation Method 1
A porous TiO2/ZrO2 support material with a crystalline phase and an amorphous phase, comprising a molar ratio of titanium to zirconium between 60:40 to 95:5, and a small amount of titanium dioxide, is used to deposit active catalyst components like manganese, iron, or cerium
Implementation Method 2
The selective catalytic reduction (SCR) process consists of the reduction of NOx, (NO, N2O and NO2) species using ammonia as a reductant in the presence of oxygen and a catalyst to produce nitrogen and water
Data Source
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AI summary
DeNOx catalysts for the reduction of NOx compounds and porous catalyst support materials are provided. The inventive catalysts comprise an active metal catalyst component and mixed TiO2/ZrO2 porous support particles that comprise a) a crystalline phase comprising titanium dioxide and/or a titanium/zirconium mixed oxide, b) an amorphous phase comprising zirconium, and c) a small amount of one or more metal oxide(s) or metalloid oxide(s) deposited on the amorphous outer layer. The inventive catalysts exhibit superior activity and ammonia selectivity.