Semi-Batch Dehydrohalogenation for Hydrofluoroolefin Production
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Solution Overview
Problem
Conventional liquid phase dehydrohalogenation reactions for producing hydrofluoroolefins result in long batch times and excessive moisture in the crude product due to the batch process and high concentration of aqueous base, leading to reduced product yield and selectivity.
Innovation Solution
A semi-batch process where an alkali-metal hydroxide feed stream is continuously added to a reactor precharged with a halogenated propane, allowing simultaneous reaction and vapor phase product separation, thereby maintaining low aqueous base concentration and optimizing reaction kinetics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a batch process with high concentration of aqueous base is used for dehydrohalogenation, then the reaction can proceed to completion, but the batch time becomes long and excessive moisture is incorporated into the crude product
Solution Approach 1:
The halogenated alkane is precharged into the reactor before the aqueous base is introduced. This preliminary action allows the organic substrate to be in place and ready for reaction, enabling immediate steam stripping of the dehydrohalogenation product as soon as the base is added, thus reducing overall batch cycle time while maintaining complete conversion
Solution Approach 2:
The invention implements continuous steam stripping of the dehydrohalogenation product during the reaction period. This continuous removal of product drives the equilibrium forward, maintaining high reaction rates and complete conversion without requiring extended batch times, thereby resolving the contradiction between yield and time
2Quantity of substance
If a batch process with high concentration of aqueous base is used for dehydrohalogenation, then the reaction can proceed to completion, but excessive moisture is incorporated into the crude product reducing product selectivity
Solution Approach 1:
The invention extracts the dehydrohalogenation product from the reaction mixture continuously via steam stripping during the reaction period. This continuous extraction removes the product from the aqueous environment, preventing moisture incorporation and maintaining high product selectivity while still achieving complete conversion
Solution Approach 2:
The invention utilizes phase transition by stripping the dehydrohalogenation product into the vapor phase using steam. This phase transition from liquid to vapor separates the organic product from the aqueous reaction medium, preventing moisture contamination and maintaining high selectivity while achieving complete conversion
3Ease of operation
If the order of reactant addition is not optimized, then the process is simple to operate, but product yield and composition are suboptimal
Solution Approach 1:
The halogenated alkane is precharged into the reactor before the aqueous base is introduced. This simple preliminary step optimizes the reaction by ensuring the organic substrate is in place to immediately react with the base upon addition, maximizing product yield while maintaining operational simplicity
Solution Approach 2:
Continuous steam stripping is implemented during the reaction period, creating a continuous useful action that drives the reaction forward and maximizes product yield. This additional simple operational step significantly improves yield without complicating the overall process
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 approach reduces batch cycle time, minimizes water content in the product, improves yield, and reduces the formation of undesirable by-products, resulting in a more efficient and economical production of hydrofluoroolefins.
Implementation Method 1
reacting, in a liquid phase, said halogenated propane with said an aqueous base in said reactor to produce a halogenated propene
Implementation Method 2
removing at least a portion of said halogenated propene from said reactor as a vapor product stream
Data Source
AI summary
A process for the manufacture of halogenated olefins in semi-batch mode by dehydrohalogenation of halogenated alkanes in the presence of an aqueous base such as KOH which simultaneously neutralizes the resulting hydrogen halide. During the process, aqueous base is continuously added to the haloalkane which results in better yields, lower by-product formation and safer/more controllable operation.