Chromium Fluorination Catalyst Zinc Distribution
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Solution Overview
Problem
The stability of chromium-containing catalysts used in the production of fluorinated hydrocarbons is improved by ensuring that zinc is evenly distributed throughout the catalyst, particularly at the surface region where it contacts hydrogen fluoride and organic reactants, enhancing the catalyst's activity and stability.
Innovation Solution
The catalyst comprises chromium compounds, including chromium oxides, fluorides, and oxyfluorides, with zinc evenly distributed across the surface and bulk, promoting catalyst activity and stability through controlled zinc distribution and calcination processes, and can be supported on materials like activated carbon or alumina.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If zinc is added to chromium-containing catalyst to promote activity, then catalyst activity is improved, but zinc distribution uniformity deteriorates leading to reduced stability
Solution Approach 1:
The patent applies preliminary action by incorporating zinc into the catalyst structure during the preparation phase through controlled coprecipitation and calcination processes. This ensures zinc is evenly distributed throughout the chromium oxide matrix before the catalyst is put into service, preventing later aggregation and maintaining both high activity and stability throughout the catalyst's operational life.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the zinc-to-chromium ratio, calcination temperature, and precipitation conditions during catalyst synthesis. These parameter optimizations ensure zinc is incorporated uniformly at the molecular level within the catalyst structure, achieving both high catalytic activity through sufficient zinc content and uniform distribution for long-term stability.
2Productivity
If zinc content is increased to enhance activity, then catalyst activity is improved, but catalyst stability deteriorates due to aggregation
Solution Approach 1:
The patent applies parameter changes by optimizing the zinc content within a specific range (0.1-10 wt%) and controlling calcination temperature (400-800°C) to prevent zinc aggregation. This balanced approach maintains sufficient zinc for high catalytic activity while preventing excessive zinc content that would lead to aggregation and stability loss.
Solution Approach 2:
The patent creates a composite catalyst material where zinc is integrated into the chromium oxide matrix through coprecipitation. This composite structure distributes zinc atoms uniformly within the chromium oxide framework, allowing high zinc content for activity while the chromium oxide matrix prevents aggregation, thereby maintaining long-term stability.
3Reliability
If zinc is uniformly distributed to improve stability, then catalyst stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating zinc uniformly during the initial coprecipitation step of catalyst synthesis. By performing the zinc incorporation and uniform distribution action during the preparation phase rather than as a separate post-processing step, the method achieves uniform zinc distribution for stability while avoiding additional complex manufacturing steps.
Solution Approach 2:
The patent merges the zinc incorporation step with the catalyst synthesis process through coprecipitation. Instead of adding zinc as a separate post-synthesis treatment, zinc is introduced simultaneously with chromium during precipitation, combining multiple functions (catalyst formation and zinc distribution) into a single integrated process step, thereby reducing manufacturing complexity.
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
This distribution of zinc improves the catalyst's activity and stability, allowing for more efficient production of fluorinated hydrocarbons by maintaining performance over multiple reaction cycles and reducing the need for frequent regeneration.
Implementation Method 1
adding zinc and chromium (III) salts to water and then co-precipitating the hydroxides of zinc and chromium (III)
Implementation Method 2
The mixture of zinc and chromium hydroxides is then collected, e.g., by filtration, washed and calcined to convert the hydroxides to their oxides
Implementation Method 3
chromium-containing fluorination catalyst and to a process for the production of fluorinated hydrocarbons that uses the catalyst
Data Source
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AI summary
A new chromium-containing fluorination catalyst is described. The catalyst comprises an amount of zinc that promotes activity. The zinc is contained in aggregates which have a size across their largest dimension of up to 1 micron. The aggregates are distributed throughout at least the surface region of the catalyst and greater than 40 weight % of the aggregates contain a concentration of zinc that is within ±1 weight % of the modal concentration of zinc in those aggregates.