Low Sodium Alumina Catalyst for Fluoroalkene Dehydrohalogenation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Catalytic dehydrohalogenation processes for preparing C 3-7 (hydro)fluoroalkenes face issues with catalyst fouling, leading to short operating cycles and catalyst life, which increases costs due to the need for frequent regeneration or additional catalyst use, especially for alumina-supported and zirconia-based catalysts, where coke combustion is difficult.
Innovation Solution
A process using a catalyst with a metal oxide, either partially or fully fluorinated, supported on alumina with low sodium content (<400 ppm) to enhance Lewis acid sites availability, specifically utilizing chromia or zirconia on alumina with additional metal promoters like Zn, Zr, or Ni, and pre-treating the catalyst with fluorination to improve stability and regenerability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional catalysts (alumina-supported or zirconia-based) are used for dehydrohalogenation, then catalytic activity is achieved, but catalyst fouling occurs leading to short operating cycles and difficult regeneration
Solution Approach 1:
The invention changes the chemical composition parameter of the catalyst by incorporating specific metal fluorides (ZrF4, HfF4, TaF5, NbF5, MoF6, WF6) at controlled concentrations (0.1-10 wt%) on the alumina support. This compositional modification fundamentally alters the catalyst's resistance to fouling while maintaining dehydrohalogenation activity, enabling longer operating cycles without regeneration.
Solution Approach 2:
The invention creates a composite catalyst system combining alumina support with metal fluoride compounds (ZrF4, HfF4, TaF5, NbF5, MoF6, or WF6). This composite structure leverages the synergistic effects where the metal fluorides enhance the alumina's Lewis acid sites and provide resistance to coke deposition, solving both activity and stability requirements simultaneously.
2Object-affected harmful factors
If catalyst exposure time to high partial pressure of unsaturates is limited, then catalyst fouling is reduced, but productivity decreases
Solution Approach 1:
The invention modifies the catalyst's chemical resistance parameters by incorporating metal fluorides that specifically inhibit coke formation mechanisms. This allows the catalyst to withstand prolonged exposure to high unsaturate partial pressures without fouling, enabling continuous operation at high productivity levels without requiring limited exposure strategies.
3Duration of action of stationary object
If hydrogen fluoride concentration is increased to control catalyst fouling, then catalyst life is extended, but process complexity and cost increase
Solution Approach 1:
The invention extracts the fouling control function from the process conditions (HF concentration) and embeds it directly into the catalyst structure through metal fluoride incorporation. This eliminates the need to maintain high HF concentrations for fouling control, simplifying the process while extending catalyst life through the inherently fouling-resistant catalyst composition.
4Power
If alumina-supported catalysts are used for dehydrohalogenation, then catalytic activity is achieved, but regeneration becomes difficult due to difficult coke combustion
Solution Approach 1:
The invention creates a composite where metal fluorides are dispersed on alumina support. The metal fluoride components (particularly ZrF4, HfF4, TaF5, NbF5, MoF6, WF6) modify the alumina surface properties to prevent strong coke adhesion, while maintaining the Lewis acid sites necessary for dehydrohalogenation activity. This composite structure enables both high activity and easy regeneration.
Solution Approach 2:
The invention changes the surface chemical parameters of the alumina support by incorporating metal fluorides, which alter the surface acidity and coke interaction characteristics. This modification maintains catalytic activity for dehydrohalogenation while significantly improving coke combustibility and regeneration ease.
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 low sodium content catalysts exhibit increased activity and stability, allowing for longer operating cycles, easier regeneration, and improved selectivity in producing C 3-7 (hydro)fluoroalkenes, minimizing fouling and reducing costs associated with catalyst replacement.
Implementation Method 1
catalytic dehydrohalogenation is believed to be preferred... dehydrohalogenating a C 3-7 hydro(halo)fluoroalkane in the presence of a catalyst
Implementation Method 2
the low sodium content of the catalysts of the subject invention increases the availability of Lewis acid sites in the catalyst, for example in the alumina support, that are required for the dehydrohalogenation reaction
Implementation Method 3
a catalyst comprising a metal oxide, or a partially or fully fluorinated metal oxide, supported on alumina
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention provides a process for preparing a C3-7 (hydro)fluoroalkene comprising dehydrohalogenating a C3-7 hydro(halo)fluoroalkane in the presence of a catalyst comprising a metal oxide supported on alumina, wherein the catalyst has a sodium content of less than about 800 ppm.