Isomerization Catalyst for Trans-HFO-1234ze Selectivity
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Solution Overview
Problem
Existing methods for producing trans-1,3,3,3-tetrafluoropropene (HFO-1234ze) result in low concentrations of the trans-isomer due to significant formation of the cis-isomer, making them economically inefficient and less productive.
Innovation Solution
A process involving dehydrofluorination of pentafluoropropane (HFC-245fa) with a caustic solution followed by isomerization using a metal-based catalyst, such as fluorinated chromia or aluminum fluoride, to convert the cis-isomer to trans-isomer, achieving high selectivity and yield of trans-HFO-1234ze.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If dehydrofluorination of HFC-245fa is performed using alkaline solution or chromium-based catalyst, then HFO-1234ze is produced, but the product contains significant amounts of cis-isomer (17.7%-23.9%) resulting in low trans-isomer concentration (74%-80.5%)
Solution Approach 1:
The patent divides the isomerization process into multiple sequential stages with different catalysts and conditions. The first stage uses a chromium-based catalyst at higher temperature to achieve partial conversion, while the second stage uses a different catalyst system at lower temperature to complete the conversion and maximize trans-isomer selectivity. This segmented approach allows optimization of each stage for specific objectives.
Solution Approach 2:
The patent systematically varies multiple parameters including temperature, pressure, catalyst composition, and residence time across different reaction stages. By changing these parameters sequentially, the process achieves high trans-isomer concentration (95%+). Specifically, the temperature is reduced from the first to second stage, and catalyst composition is modified to enhance selectivity.
2Productivity
If known processes are used to produce HFO-1234ze, then production is achieved, but the process is economically inefficient due to low product yield and formation of undesired cis-isomer
Solution Approach 1:
The patent converts the harmful byproduct (cis-isomer) formed during dehydrofluorination into a beneficial intermediate. Instead of discarding or separately processing the cis-isomer, the invention uses it as feedstock for the isomerization stage, where it is converted to the desired trans-isomer. This transforms a waste stream into a valuable resource, improving overall atom economy and reducing losses.
Solution Approach 2:
The patent performs preliminary dehydrofluorination to generate both cis and trans isomers, then uses this mixture as feedstock for the subsequent isomerization step. This preliminary action ensures that all carbon atoms from the starting material are utilized, and the cis-isomer formed is immediately put to productive use in the second stage, maximizing overall yield.
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 method produces compositions with at least 85% trans-HFO-1234ze, improving economic efficiency and yield compared to prior art, by effectively converting a substantial portion of cis-HFO-1234ze to trans-HFO-1234ze, thereby enhancing the commercial viability of the process.
Implementation Method 1
contacting at least a portion, preferably substantially portion, and in certain embodiments substantially all of said reaction product with at least one isomerization catalyst to convert at least a portion, and preferably at least a substantial portion, of cis-HFO-1234ze in said reaction product to trans-HFO-1234ze
Implementation Method 2
converting, preferably by dehydrofluorination, pentafluorpropane (HFC-245), preferably 1,1,1,3,3- pentafluorpropane (HFC-245fa), preferably by contact with a caustic solution, to a reaction product comprising cis-HFO-1234ze and trans-HFO-1234ze
Data Source
Figure 1
AI summary
Disclosed is a method for forming HFO-1234ze, and for forming compositions comprising HFO-1234ze, by (a) converting, preferably by dehydrofluorination, pentafluorpropane (HFC-245), preferably 1,1,1,3,3- pentafluorpropane (HFC-245fa), preferably by contact with a caustic solution, to a reaction product comprising cis-HFO-1234ze and trans-HFO-1234ze; and (b) contacting at least a portion, preferably substantially portion, and in certain embodiments substantially all of said reaction product with at least one isomerization catalyst to convert at least a portion, and preferably at least a substantial portion, of cis-HFO-1234ze in said reaction product to trans-HFO-1234ze.