HCC-240fa Production By-product Mitigation via Segmented Catalyst Addition
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Solution Overview
Problem
The existing process for manufacturing 1,1,1,3,3-pentachloropropane (HCC-240fa) generates substantial by-products such as hexachloroethane, tetrachloroethene, chloroform, and hexachlorobutadiene during start-up, reducing selectivity, and later produces undesirable vinyl chloride originating by-products like 1,1,3,5,5-hexachloropentane, leading to yield loss.
Innovation Solution
Modifying the process by minimizing or omitting ferric chloride during start-up and introducing chelated or pre-chelated ferric chloride after the start-up phase to suppress the formation of undesirable by-products, using iron powder and tributylphosphate as catalysts, and recycling pre-chelated ferric chloride to maintain high HCC-240fa selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ferric chloride is used during start-up phase, then the reaction proceeds efficiently, but substantial amounts of CCl4 by-products such as hexachloroethane, tetrachloroethene, chloroform, and hexachlorobutadiene are generated, reducing HCC-240fa selectivity
Solution Approach 1:
The patent divides the catalytic process into two distinct phases: start-up phase and steady-state phase. During start-up phase, only iron powder and TBP are used as catalysts to minimize CCl4 by-products. During steady-state phase, pre-chelated ferric chloride is introduced to suppress vinyl chloride by-products. This temporal segmentation of catalyst usage resolves the contradiction between reaction efficiency and by-product formation.
Solution Approach 2:
The patent employs pre-chelated ferric chloride that has been pre-treated with TBP before introduction to the reactor. This preliminary chelation action prepares the ferric chloride to function effectively as a catalyst in suppressing vinyl chloride by-products during steady-state operation, preventing harmful by-product formation before they can occur.
2Productivity
If fresh catalyst consisting of iron powder and TBP is introduced after HCC-240fa accumulation, then the reaction continues, but VCM preferentially reacts with HCC-240fa to form undesirable vinyl chloride by-products such as 1,1,3,3,5,5-hexachloropentane, causing substantial yield loss
Solution Approach 1:
The patent employs pre-chelated ferric chloride that has been pre-treated with TBP before introduction to the reactor. This preliminary chelation action prepares the ferric chloride to function effectively as a catalyst in suppressing vinyl chloride by-products during steady-state operation, preventing harmful by-product formation before they can occur.
Solution Approach 2:
The patent uses pre-chelated ferric chloride as an intermediary catalyst that mediates between VCM and HCC-240fa during steady-state operation. This intermediary catalyst directs the reaction to produce desired products while suppressing the formation of vinyl chloride by-products, resolving the contradiction between reaction continuity and by-product formation.
3Productivity
If the reaction is conducted as continuous operation with high HCC-240fa concentration in the reactor, then productivity increases, but the selectivity decreases due to preferential reaction of VCM with HCC-240fa
Solution Approach 1:
The patent changes the catalytic parameters during different operational phases. During start-up, only iron powder and TBP are used. During continuous steady-state operation, pre-chelated ferric chloride is introduced to alter the catalytic behavior and suppress vinyl chloride by-products. This parameter change enables maintaining high productivity while improving selectivity.
Solution Approach 2:
The patent divides the catalytic process into two distinct phases: start-up phase and steady-state phase. During start-up phase, only iron powder and TBP are used as catalysts to minimize CCl4 by-products. During steady-state phase, pre-chelated ferric chloride is introduced to suppress vinyl chloride by-products. This temporal segmentation of catalyst usage resolves the contradiction between reaction efficiency and by-product formation.
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
Significantly reduces the formation of undesirable by-products, improving the selectivity and yield of HCC-240fa to above 90% by minimizing hexachloroethane and vinyl chloride by-products, enhancing the overall manufacturing efficiency.
Implementation Method 1
reacting carbon tetrachloride (CCl4) and vinyl chloride (VCM) in the presence of a catalyst mixture comprising organophosphate, e.g., tributylphosphate (TBP), metallic iron and ferric chloride
Implementation Method 2
introducing chelated or pre-chelated ferric chloride after the start-up phase to suppress the formation of undesirable by-products
Data Source
AI summary
Disclosed is a process for the manufacture of haloalkane compounds, and more particularly, an improved process for the manufacture of the compound 1,1,1,3,3-penta-chloropropane (HCC-240fa), which mitigates the formation of by-products from vinyl chloride (CH2═CHCl). The present invention is also useful in the manufacture of other haloalkane compounds such as HCC-250 and HCC-360. One embodiment of the invention comprises a method for mitigating 1,1,3,3,5,5-hexachloropentane and 1,1,1,3,5,5-hexachloropentane formation in the HCC-240fa manufacturing process, in which FeCl3, is introduced to a reactor only after the start-up phase has ended and a continuous operation has started. In a preferred embodiment, “pre-chelated” FeCl3, which is concentrated in a catalyst recovery column, is introduced to reactor after the continuous operation has started.