Stable Ferrous Ferric Nitrate Solutions for Fischer-Tropsch Catalysts
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Solution Overview
Problem
The challenge in Fischer-Tropsch synthesis is the instability of ferrous nitrate solutions and the difficulty in maintaining a desired ratio of ferrous to ferric iron, which affects the production of stable iron catalysts, leading to catalyst breakdown and reduced activity and selectivity in slurry bubble column reactors.
Innovation Solution
A method is developed to produce stable ferrous and ferric nitrate solutions by dissolving iron in nitric acid at specific concentrations and temperatures, maintaining the solutions for defined periods, and combining them to achieve a desired Fe(II)/Fe(III) nitrate ratio, which enhances catalyst stability and reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferrous nitrate solution is used for catalyst preparation, then catalyst activity and selectivity are improved, but the solution is unstable and the Fe(II)/Fe(III) ratio cannot be maintained
Solution Approach 1:
The patent applies preliminary action by preparing the ferrous nitrate solution with controlled oxidation conditions before catalyst formation. The solution is prepared with a specific Fe(II)/Fe(III) ratio and then used immediately for catalyst precipitation, ensuring the desired ratio is locked in before any instability can occur during storage.
Solution Approach 2:
The patent changes the concentration parameters of the nitrate solution to achieve stability. Specifically, it uses a total iron concentration of 0.5-2.0 M with a controlled Fe(II)/Fe(III) ratio, and adjusts the nitric acid concentration to maintain solution stability while preserving catalyst activity.
2Strength
If iron catalyst is strengthened to prevent breakdown, then catalyst strength is improved, but activity and selectivity are compromised
Solution Approach 1:
The patent applies local quality by adding structural promoters at specific locations within the catalyst structure. The structural promoters are incorporated during the precipitation process to provide localized strengthening without affecting the overall catalyst composition and activity.
Solution Approach 2:
The patent uses composite materials by combining iron oxide with structural promoters to create a strengthened catalyst. The composite structure provides both the mechanical strength needed to prevent breakdown and the catalytic activity required for high performance.
3Stability of the object's composition
If time is extended to achieve stable Fe(II)/Fe(III) solution, then solution stability is improved, but manufacturing time and costs increase
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the oxidation conditions and Fe(II)/Fe(III) ratio during solution preparation. This ensures the solution achieves the desired stability quickly without requiring extended aging or waiting periods, thereby reducing manufacturing time.
Solution Approach 2:
The patent changes the concentration parameters to achieve rapid stabilization. By controlling the total iron concentration at 0.5-2.0 M and the nitric acid concentration appropriately, the solution reaches stable conditions faster, reducing the time required for catalyst manufacturing.
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 method results in a stable iron catalyst with improved resistance to breakdown, maintaining high activity and selectivity for high molecular weight hydrocarbons, and reduces the time and costs associated with catalyst manufacturing.
Implementation Method 1
dissolving iron in nitric acid to form a ferrous nitrate solution
Implementation Method 2
dissolving iron in nitric acid at specific concentrations and temperatures, maintaining the solutions for defined periods
Implementation Method 3
precipitating iron from an acid solution comprising a desired ratio of ferrous iron to ferric iron
Data Source
AI summary
A method of producing stable ferrous nitrate solution by dissolving iron in nitric acid to form a ferrous nitrate solution and maintaining the solution at a first temperature for a first time period, whereby the Fe(II) content of the ferrous nitrate solution changes by less than about 2% over a second time period. A method of producing stable Fe(II)/Fe(III) nitrate solution comprising ferrous nitrate and ferric nitrate and having a desired ratio of ferrous iron to ferric iron, including obtaining a stable ferrous nitrate solution; dissolving iron in nitric acid to form a ferric nitrate solution; maintaining the ferric nitrate solution at a second temperature for a third time period; and combining amounts of stable ferrous nitrate solution and ferric nitrate solution to produce the stable Fe(II)/Fe(III) nitrate solution. A method of preparing an iron catalyst is also described.