Halogenated Alkene Preparation via Chlorinated Catalyst
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Solution Overview
Problem
The preparation of (hydro)(chloro)fluoroalkenes via catalytic dehydrochlorination is hindered by competing dehydrofluorination reactions, leading to lower selectivity and yield of the desired products due to the formation of unwanted by-products.
Innovation Solution
A process involving the use of a catalyst selected from metal oxide, metal halide, zero-valent metal, or carbon-based catalysts, where the catalyst is chlorinated prior to contact with the hydrochlorofluoroalkane, and/or a HCl co-feed is present during dehydrochlorination, with periodic regeneration through oxyfluorination and oxychlorination to enhance selectivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If catalytic dehydrochlorination is used to prepare (hydro)(chloro)fluoroalkenes, then the reaction can proceed under milder conditions compared to thermal pyrolysis, but competing dehydrofluorination reactions occur leading to lower selectivity
Solution Approach 1:
The invention changes the chemical state of the catalyst by chlorinating it before use, transforming it from a generic catalyst to a specifically activated chlorinated catalyst. This parameter change in the catalyst's chemical composition enables high selectivity for dehydrochlorination while suppressing dehydrofluorination, even at lower temperatures where competing reactions would otherwise occur.
Solution Approach 2:
The chlorinated catalyst acts as a selective intermediary that mediates between the hydrochlorofluoroalkane substrate and the desired (hydro)(chloro)fluoroalkene product. By introducing chlorine onto the catalyst surface, it creates specific active sites that preferentially catalyze dehydrochlorination over dehydrofluorination, thereby controlling selectivity.
2Productivity
If strong bases are used for chemical dehydrochlorination, then the reaction proceeds efficiently, but the process becomes more complex and requires additional handling steps
Solution Approach 1:
The invention replaces the chemical mechanism of strong base-mediated dehydrochlorination with a catalytic mechanism using chlorinated metal oxides or metal halides. This substitution eliminates the need for stoichiometric amounts of strong bases and their associated handling, filtration, and waste disposal steps, thereby reducing process complexity while maintaining high productivity.
Solution Approach 2:
The catalytic process allows for easier recovery and reuse of the active component compared to stoichiometric strong bases. The chlorinated catalyst can be regenerated and reused multiple times, reducing waste and simplifying the overall process compared to single-use strong base systems that require complex separation and treatment steps.
3Ease of manufacture
If conventional catalysts are used without pre-chlorination, then the process is simpler, but the catalyst stability and selectivity are insufficient
Solution Approach 1:
The invention applies preliminary chlorination to the catalyst before the main dehydrochlorination reaction. This preliminary action of introducing chlorine onto the catalyst surface creates the necessary active sites and stabilizes the catalyst structure, ensuring high selectivity and stability during subsequent use. The simple one-step chlorination treatment adds minimal complexity while dramatically improving reliability.
4Ease of operation
If dehydrochlorination is performed without suppressing dehydrofluorination, then the reaction conditions can be less restrictive, but unwanted by-products are formed that require removal or recycling
Solution Approach 1:
The invention changes the chemical parameter of the catalyst by chlorinating it, which fundamentally alters the reaction pathway selectivity. This parameter change suppresses dehydrofluorination while maintaining dehydrochlorination, allowing flexible operating conditions without generating unwanted by-products that would require removal or recycling.
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 significantly increases the selectivity and yield of (hydro)(chloro)fluoroalkenes by suppressing dehydrofluorination reactions, thereby improving the productivity of the reaction and extending catalyst stability.
Implementation Method 1
contacting a reagent stream comprising a C 3-7 hydrochlorofluoroalkane with a catalyst in a reactor to dehydrochlorinate at least a portion of the C 3-7 hydrochlorofluoroalkane
Implementation Method 2
the catalyst is chlorinated prior to contacting it with the reagent stream comprising the C 3-7 hydrochlorofluoroalkane
Implementation Method 3
dehydrochlorinate at least a portion of the C 3-7 hydrochlorofluoroalkane to produce a product stream comprising the C 3-7 (hydro)(chloro)fluoroalkene and hydrogen chloride (HCl)
Implementation Method 4
the catalyst is periodically regenerated by regenerative oxidation or regenerative oxyfluorination
Implementation Method 5
then regenerative oxychlorination
Data Source
AI summary
The present invention provides a process for the preparation of a C3-7 (hydro)(chloro)fluoroalkene, the process comprising contacting a reagent stream comprising a C3-7 hydrochlorofluoroalkane with a catalyst in a reactor to dehydrochlorinate at least a portion of the C3-7 hydrochlorofluoroalkane to produce a product stream comprising the C3-7 (hydro)(chloro)fluoroalkene and hydrogen chloride (HCl), wherein the catalyst is selected from metal oxide catalysts, metal halide catalysts, zero-valent metal catalysts, carbon-based catalysts and mixtures thereof, wherein: (i) the catalyst is chlorinated prior to contacting it with the reagent stream comprising the C3-7 hydrochlorofluoroalkane; and/or (ii) the contacting step is carried out in the presence of a HCl co-feed; and wherein the catalyst is periodically regenerated by regenerative oxidation or regenerative oxyfluorination, and then regenerative chlorination.