Core-Shell Catalyst for Simultaneous HCN and AsH3 Removal
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Solution Overview
Problem
Current methods for purifying industrial waste gases, particularly those containing hydrogen cyanide (HCN) and arsine (AsH3), are inefficient, costly, and often result in secondary pollution, with no effective technology available for simultaneous removal of both gases with stability and low environmental impact.
Innovation Solution
A core-shell structured catalyst is developed, comprising a metal oxide-molecular sieve core and porous silica shell, utilizing oxides of metals like Fe, Cu, Ti, Ni, or Mn combined with Ce or La, which facilitates catalytic hydrolysis-oxidation coupling for simultaneous removal of HCN and AsH3, preventing secondary pollution through the use of common metals and inexpensive silica.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If absorption method using alkaline solution is used to remove HCN, then HCN removal is achieved, but CN- transferred to liquid phase increases environmental risk and effect becomes unstable
Solution Approach 1:
The patent replaces the liquid-phase absorption mechanism with a solid-catalyst surface reaction mechanism. The catalyst core-shell structure provides active sites for HCN decomposition on its surface, converting HCN to N2 and CO without generating soluble CN- ions, thereby eliminating the environmental risk associated with liquid-phase cyanide transfer.
Solution Approach 2:
The patent changes the chemical environment from liquid alkaline solution to solid catalyst surface with specific metal oxide compositions (Fe, Cu, Ti, Ni, Mn combined with Ce or La). This parameter change transforms the reaction pathway from absorption to catalytic decomposition, achieving stable HCN removal without secondary pollution.
2Object-affected harmful factors
If adsorption method is used to remove HCN, then HCN gas emission is reduced, but adsorbent cannot decompose HCN causing secondary pollution
Solution Approach 1:
The patent replaces physical adsorption with catalytic decomposition on metal oxide surfaces. The catalyst actively breaks down HCN molecules into harmless N2 and CO through surface reactions, rather than merely trapping them on adsorbent surfaces, thereby preventing secondary pollution from saturated adsorbents.
Solution Approach 2:
The patent employs a composite catalyst structure combining metal oxides (Fe, Cu, Ti, Ni, or Mn) with Ce or La on a molecular sieve support. This composite material provides both high HCN decomposition activity and structural stability, ensuring complete conversion without secondary pollution while maintaining cost-effectiveness.
3Object-affected harmful factors
If combustion method using precious metal catalyst is used, then HCN removal is achieved, but preparation cost increases and nitrogen oxides are produced causing photochemical smog
Solution Approach 1:
The patent replaces expensive precious metal catalysts with abundant, inexpensive metal oxides (Fe, Cu, Ti, Ni, Mn combined with Ce or La). These non-precious metal catalysts achieve comparable HCN decomposition performance without producing nitrogen oxides, significantly reducing both material cost and environmental impact.
Solution Approach 2:
The patent changes the catalyst composition from precious metals to non-precious metal oxides with specific catalytic properties. This parameter change modifies the reaction pathway to favor complete decomposition into N2 and CO rather than combustion producing NOx, while maintaining cost-effectiveness.
4Object-affected harmful factors
If catalytic oxidation method is used to treat HCN, then HCN is converted to NOx and COx, but products still cause environmental pollution
Solution Approach 1:
The patent transforms the harmful HCN molecule into completely harmless products (N2 and CO) through catalytic decomposition, rather than converting it to less harmful but still polluting substances like NOx and COx. This approach fully eliminates environmental risk by producing benign end products.
5Object-affected harmful factors
If chemical absorption method is used to remove AsH3, then AsH3 is removed by redox reaction, but equipment corrosion and absorption liquid pollution occur
Solution Approach 1:
The patent replaces liquid-phase chemical absorption with solid-catalyst surface oxidation. The catalyst provides active sites for AsH3 oxidation to As2O3 on its surface, avoiding contact between corrosive reagents and equipment, and eliminating liquid waste disposal issues while achieving complete AsH3 removal.
6Object-affected harmful factors
If direct combustion method is used to remove AsH3, then AsH3 is combusted, but large amount of methane and propane are required and combustion energy cannot be recycled
Solution Approach 1:
The patent replaces thermal combustion with catalytic oxidation at lower temperatures. The catalyst enables AsH3 oxidation to proceed at reduced temperatures, eliminating the need for large amounts of combustion aids like methane and propane, and allowing for potential energy recovery from the exothermic reaction.
7Object-affected harmful factors
If conventional catalysts are used, then single pollutant removal may be achieved, but simultaneous removal of HCN and AsH3 with stability and low cost is not possible
Solution Approach 1:
The patent designs a universal catalyst with dual functionality: the metal oxide core (Fe, Cu, Ti, Ni, or Mn combined with Ce or La) catalyzes both HCN decomposition and AsH3 oxidation reactions simultaneously. The porous silica shell provides structural support and enhances stability, enabling one catalyst to handle multiple toxic gases without requiring separate treatment systems.
Solution Approach 2:
The patent employs a composite core-shell structure combining metal oxides on molecular sieve support with porous silica outer shell. This composite architecture integrates multiple functions: the metal oxide provides dual catalytic activity for HCN and AsH3, the molecular sieve offers structural stability and porosity, and the silica shell enhances chemical stability and prevents sintering, achieving simultaneous removal of both pollutants with high stability and cost-effectiveness.
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 stable and efficient removal of HCN and AsH3 with no secondary pollution, maintaining high removal efficiency over time and reducing costs by utilizing abundant and inexpensive materials.
Implementation Method 1
The catalytic hydrolysis method refers to a hydrolysis reaction of HCN in the presence of water vapor and catalyst within a certain range of temperature, which generates NH3 and CO
Implementation Method 2
The catalytic oxidation method refers to oxidation of AsH3 to As2O3 in the presence of O2 and catalyst
Implementation Method 3
The adsorption method mainly uses an adsorbent to absorb a HCN gas, thereby reducing HCN gas emission
Data Source
AI summary
The present disclosure relates to the technical field of industrial waste gas purification, in particular to a core-shell structured catalyst, a preparation method and use thereof. The present disclosure provides a core-shell structured catalyst including a metal oxide-molecular sieve as a core and porous silica (SiO2) as a shell, where the metal oxide-molecular sieve includes a molecular sieve and a metal oxide loaded on the molecular sieve, the metal oxide includes an oxide of a first metal and an oxide of a second metal, the first metal is Fe, Cu, Ti, Ni or Mn, and the second metal is Ce or La. The core-shell structured catalyst of the present disclosure can enable effective removal of HCN and AsH3 at the same time with a stable effect, and no secondary pollution.