HFO-1234ze and HFO-1234yf Synthesis via Dechlorination
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Solution Overview
Problem
Current methods for preparing hydrofluoroolefins (HFOs) like 1,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropene face challenges such as expensive and difficult-to-access reaction materials, harsh conditions, and the use of environmentally unfriendly catalysts, leading to inefficiencies and safety concerns in industrial production.
Innovation Solution
A three-step process involving fluorination, dechlorination, and gas phase fluorination using Fe—Al—Mg—F and Al—Co—Zn—F catalysts, with starting materials like CCl2═CCl—CHCl2, which are inexpensive and easily accessible, and zero-valent transition metals like Zn or Cu, to produce HFO-1234ze and HFO-1234yf under mild reaction conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chromium-based catalysts are used in the preparation of HFO-1234yf, then the reaction can proceed effectively, but the catalyst causes serious harm to people and the environment due to carcinogenic effects
Solution Approach 1:
The patent replaces expensive and harmful chromium-based catalysts with inexpensive, environmentally friendly alternative catalysts such as iron-based, aluminum-based, or zinc-based catalysts. These catalysts achieve the same dehydrochlorination function without the carcinogenic effects, effectively resolving the contradiction between reaction effectiveness and environmental safety.
Solution Approach 2:
The patent changes the chemical composition parameters of the catalyst system, transitioning from chromium-based catalysts to alternative metal-based catalysts (Fe, Al, Zn, etc.). This parameter change maintains catalytic activity while eliminating harmful effects, thus resolving the contradiction between productivity and environmental harm.
2Productivity
If HCFC-1233xf and HCFC-244bb intermediates are used in the preparation process, then HFO-1234yf can be synthesized, but the intermediates form azeotropes that are difficult to separate effectively
Solution Approach 1:
The patent eliminates the problematic intermediate compounds (HCFC-1233xf and HCFC-244bb) from the synthesis pathway. By using a direct dehydrochlorination route from HFC-245eb without forming these azeotrope-prone intermediates, the patent removes the separation difficulty while maintaining synthesis capability.
3Productivity
If a four-step reaction process is used to synthesize HFO-1234yf from HFP, then the product can be obtained, but the process requires stoichiometric or excessive hydrogen which increases safety risks and cost
Solution Approach 1:
The patent simplifies the complex four-step hydrogenation-dehydrofluorination process into a single direct dehydrochlorination step. This segmentation reduces the number of reaction stages and eliminates the need for stoichiometric hydrogen, thereby reducing both material consumption and safety risks associated with hydrogen handling.
Solution Approach 2:
The patent converts the harmful chlorinated intermediate (HFC-245eb) directly into the desired product through dehydrochlorination, avoiding the need for hydrogenation steps that require excessive hydrogen. This approach transforms a potentially harmful process into a safer, more efficient route.
4Productivity
If telomerization followed by continuous fluorination is used to prepare HFO-1234ze, then the product can be synthesized, but the catalyst is expensive and prone to coking and deactivation
Solution Approach 1:
The patent replaces expensive telomerization catalysts that are prone to coking and deactivation with cheaper, more stable alternative catalysts. The use of iron-based, aluminum-based, or zinc-based catalysts in the fluorination step provides cost-effective and durable catalytic activity without the coking problems associated with traditional telomerization routes.
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 process enables the effective and environmentally friendly joint preparation of 1,3,3-tetrafluoropropene and 2,3,3-tetrafluoropropene, using commercially available starting materials and avoiding hazardous catalysts, with reaction temperatures not exceeding 240°C, thus improving safety and industrial viability.
Implementation Method 1
starting materials comprising at least one compound having the structures of formula I, II or III undergo fluorination reaction with hydrogen fluoride in the presence of a fluorination catalyst
Implementation Method 2
1,2,3-trichloro-3,3-difluoropropene, 1,2,3-trichloro-1,1,2-trifluoropropane and 1,2,3-trichloro-1,1,3-trifluoropropane undergo dechlorination in a reaction solvent under the action of zero-valent transition metal and organic nitrogen-containing ligand
Implementation Method 3
3-chloro-3,3-difluoropropyne, 3-chloro-2,3,3-trifluoropropene and 3-chloro-1,3,3-trifluoropropene undergo gas phase fluorination reaction with hydrogen fluoride in the presence of a gas phase fluorination catalyst
Data Source
AI summary
A process for the joint preparation of 1,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropene, comprising: (a) starting materials comprising at least one compound having the structure of formula I, II or III are reacted with hydrogen fluoride, producing 1,2,3-trichloro-3,3-difluoropropene, 1,2,3-trichloro-1,1,2-trifluoropropane, and 1,2,3-trichloro-1,1,3-trifluoropropane; in the compounds of said formulae CF2-mClm═CCl—CHF2-nCln (Formula I), CF3-pClpCHCl═CH2Cl (Formula II), and CF3-xClxCF2-yClyCHF2-zClz (Formula III), m=0, 1, 2; n=1, 2; p=2, 3; x=1, 2, 3; y=1, 2; z=1, 2 and 4≦x+y+z≦6; (b) the 1,2,3-trichloro-3,3-difluoropropene, 1,2,3-trichloro-1,1,2-trifluoropropane and 1,2,3-trichloro-1,1,3-trifluoropropane undergo dechlorination, producing 3-chloro-3,3-difluoropropyne, 3-chloro-2,3,3-trifluoropropene and 3-chloro-1,3,3-trifluoropropene; and (c) the 3-chloro-3,3-difluoropropyne, 3-chloro-2,3,3-trifluoropropene and 3-chloro-1,3,3-trifluoropropene are reacted with hydrogen fluoride, simultaneously yielding 1,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropen.