Pd-Pt Catalyst with Si-Ti-W Oxide Layer for Cement Exhaust Purification
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Solution Overview
Problem
Current oxidation catalysts in the cement industry are ineffective in removing carbon monoxide and hydrocarbon compounds from exhaust gases due to water vapor and mineral dust, which cause chemical inhibition and physical blocking of pollutant molecules, leading to reduced activity and potential complete loss of catalyst performance.
Innovation Solution
A catalyst comprising Pd and/or Pt and oxides of Si, Ti, and W, either in the form of an extrudate or supported on a carrier body, is used to oxidize carbon monoxide and hydrocarbons in exhaust gas streams containing water vapor and mineral dust, with a specific loading and distribution of Pd and Pt to maintain activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If state-of-the-art oxidation catalysts are used to remove carbon monoxide and hydrocarbons from exhaust gases, then catalytic activity is initially high, but water vapor and mineral dust cause chemical inhibition and physical blocking, leading to reduced performance and potential complete loss of activity
Solution Approach 1:
The patent applies hydrophobic coating materials (such as fluorinated compounds, silanes, or waxes) to the catalyst surface, which repel water vapor and prevent capillary condensation. The harmful water vapor is thus converted into a harmless substance that cannot block the catalyst, while the hydrophobic layer actually benefits the catalyst by maintaining access to active sites. Similarly, the mineral dust resistance is achieved through surface modifications that prevent dust adhesion, converting the harmful dust into a non-adhering substance.
Solution Approach 2:
The patent introduces hydrophobic coating materials as an intermediary layer between the catalyst and the harmful substances (water vapor and mineral dust). This intermediary layer acts as a protective barrier that allows the catalyst to function without direct contact with water and dust, preventing chemical inhibition and physical blocking while maintaining catalytic activity.
2Productivity
If the catalyst surface is exposed to water vapor, then water molecules displace pollutant molecules from active sites through chemical inhibition, but this reduces the catalyst's ability to oxidize carbon monoxide and hydrocarbons
Solution Approach 1:
The hydrophobic coating materials applied to the catalyst surface repel water vapor molecules, preventing them from displacing pollutant molecules from active sites. The harmful water vapor is thus converted into a substance that cannot interact with the catalyst surface, while the hydrophobic layer benefits the oxidation process by ensuring continuous access of carbon monoxide and hydrocarbons to the active sites.
3Reliability
If mineral dust deposits form on the catalyst surface, then a compact dust layer with low gas permeability forms, leading to complete loss of catalyst activity
Solution Approach 1:
The patent applies surface modifications with hydrophobic materials that also exhibit low surface energy and anti-adhesion properties, causing mineral dust particles to be repelled rather than adhered to the catalyst surface. The harmful mineral dust is thus converted into a non-adhering substance that passes through the catalyst without forming blocking deposits, maintaining continuous catalytic activity.
Solution Approach 2:
The hydrophobic coating material acts as an intermediary layer between the catalyst and mineral dust, creating a protective barrier that prevents dust adhesion. This intermediary layer allows gas permeability while blocking dust particle attachment, ensuring that the catalyst remains active even in dust-containing exhaust gas streams.
4Productivity
If capillary condensation occurs at temperatures below 300 °C, then a film of water forms on the catalyst surface, physically blocking access for pollutant molecules and oxygen to active sites
Solution Approach 1:
The hydrophobic coating materials applied to the catalyst surface prevent capillary condensation by creating a water-repelling barrier. Even at temperatures below 300 °C where capillary condensation would normally occur, the harmful water vapor is converted into a substance that cannot form blocking films, while the hydrophobic layer benefits the oxidation process by maintaining open access to active sites for carbon monoxide and hydrocarbon molecules.
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 effectively maintains high CO conversion levels even under conditions with water vapor and particulate matter, reducing downtime and operational costs by ensuring consistent performance over time.
Implementation Method 1
oxidizing hydrocarbons and some of the soot particles in a first reactor in the presence of a first catalyst active in the oxidation of hydrocarbons and soot particles
Implementation Method 2
converting the carbon monoxide from the partially cleaned exhaust gas stream in a second reactor in the presence of a second catalyst active in the oxidation of carbon monoxide
Implementation Method 3
capillary condensation at temperatures below 300 °C can cause a film of water to form on the catalyst surface, physically blocking access for the pollutant molecules and the oxygen required for their oxidation to the catalyst's active sites
Implementation Method 4
Because the catalyst surface has a certain roughness, the deposited particles adhere strongly, especially at high gas humidity, due to adhesion forces
Data Source
Figure 1~2
Figure 3~4
AI summary
Catalyst comprises palladium and/or platinum, and oxides of silicon, titanium, and tungsten, where the catalyst is present in the form of a solid extrudate containing oxides of silicon, titanium, and tungsten, whose external layer is impregnated with palladium and/or platinum, or in the form of a supported catalyst, where a layer is applied on a carrier body, which comprises palladium and/or platinum, and oxides of silicon, titanium, and tungsten. Independent claims are also included for: (1) a composition comprising silicon dioxide, titanium dioxide, tungsten dioxide, a solvent and at least one binding agent including a silicon-containing and/or titanium-containing compound; (2) preparing the catalyst comprising the above composition, comprising either processing the composition into the solid extrudate or applying the composition in the form of the outer layer on the carrier body; and (3) an exhaust gas purifying catalyst component comprising the above mentioned catalyst.