Dual-Function Catalyst for FCC Off-Gas HCN and NOx Removal
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Solution Overview
Problem
There is a need to efficiently remove hydrogen cyanide (HCN) from off-gases generated in fluid catalytic cracking (FCC) units while avoiding undesirable levels of other pollutants such as ammonia (NH3), nitrogen oxides (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs).
Innovation Solution
A system comprising a catalytic article with a dual function catalyst (DFC) and/or a selective catalytic reduction (SCR) catalyst, which includes a catalyst substrate with a washcoat comprising platinum group metals, titanium oxide, and vanadium oxide. This system introduces ammonia and water into the off-gases to facilitate the removal of HCN through catalytic oxidation, hydrolysis, and denitrification pathways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional oxidation catalysts and SCR catalysts are used separately to remove VOCs/CO and NOx, then each pollutant can be addressed, but the system complexity increases and HCN removal is not effectively integrated
Solution Approach 1:
The patent combines oxidation catalyst functions and SCR catalyst functions into a single integrated dual-function catalyst. The catalyst includes both oxidation active components (Pt, Pd, Rh on alumina) and SCR active components (Fe, Cu, Ga on zeolite) in one device, allowing simultaneous removal of VOCs/CO and NOx while also addressing HCN removal, thereby reducing system complexity while maintaining comprehensive pollutant removal coverage
Solution Approach 2:
The dual-function catalyst is designed to perform multiple functions: oxidizing VOCs and CO, reducing NOx via SCR, and removing HCN. This multi-functional catalyst replaces the need for separate dedicated catalysts for each function, achieving versatile pollutant removal while simplifying the overall system structure
2Object-affected harmful factors
If HCN removal is prioritized through catalytic oxidation, then HCN levels decrease, but other pollutants like NOx and VOCs may not be adequately removed
Solution Approach 1:
The dual-function catalyst simultaneously performs oxidation of VOCs and CO, SCR reduction of NOx, and oxidation of HCN. By integrating all these functions into one catalyst system, the patent ensures that prioritizing HCN removal does not compromise the removal of other pollutants, as all functions operate concurrently rather than sequentially
3Productivity
If ammonia is introduced to facilitate HCN removal through hydrolysis and denitrification, then HCN conversion improves, but ammonia slip and secondary pollution may occur
Solution Approach 1:
The patent incorporates ammonia slip control mechanisms where the system monitors and adjusts ammonia introduction based on actual conditions. The dual-function catalyst design allows unreacted ammonia to be oxidized by the oxidation components, providing a feedback mechanism that prevents ammonia slip while maintaining high HCN conversion efficiency through hydrolysis and denitrification pathways
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 system effectively reduces HCN levels in FCC unit off-gases while simultaneously removing NOx, hydrocarbons, and VOCs, thereby meeting regulatory requirements and ensuring environmental safety.
Implementation Method 1
catalytic oxidation, hydrolysis, and denitrification pathways
Implementation Method 2
catalytic oxidation, hydrolysis, and denitrification pathways
Implementation Method 3
selective catalytic reduction (SCR) of nitrogen oxides (NOx)
Data Source
AI summary
Systems and methods directed at removing HCN from an FCC process flue gas (and/or generated in the catalyst system reactions themselves) such that the final HCN output is satisfactory; while, in so doing, avoiding undesirable levels of other pollutants contained in that exhaust gas such as NOx. A system includes an assembly having a fluid catalytic cracking (FCC) unit generating a flue gas with HCN and NOx and a catalyst device placed in the flue gas line to remove HCN and NOx. The catalyst device having one or more SCR catalytic articles, as in one free of platinum group metal material (PGM) or a dual functioning SCR catalyst with PGM, or a combination of each. The assembly can be provided with an ammonia supplier and optionally an H2O supplier with associated injection for supply into the flue gas upstream of a catalytic article(s).