Ethane Oxidative Dehydrogenation Acetic Acid Recycling
Solution Overview
Problem
The oxidative dehydrogenation of ethane to produce ethylene often results in the formation of unwanted by-products such as acetic acid, which complicates downstream separation processes and increases costs.
Innovation Solution
Incorporating acetic acid into the feed stream, along with ethane and oxygen, and using an oxidative dehydrogenation catalyst in a reactor under specific conditions to produce a product stream that includes ethylene, unreacted ethane, water, and acetic acid, while minimizing the production of acetic acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oxidative dehydrogenation of ethane is performed to produce ethylene, then ethylene production is improved, but acetic acid by-product formation increases
Solution Approach 1:
The patent applies the principle of converting harm into benefit by feeding acetic acid back into the reactor along with ethane and oxygen. The acetic acid serves a dual function: it acts as a catalyst promoter to enhance ethylene production while simultaneously suppressing its own formation through feedback inhibition. This transforms the harmful by-product into a useful process component that improves overall selectivity.
Solution Approach 2:
The patent implements feedback control by monitoring acetic acid concentration in the product stream and adjusting the feed composition accordingly. Acetic acid is separated from the product stream and recycled to the reactor inlet, where it modulates the catalytic activity to maintain optimal ethylene production while minimizing further acetic acid generation. This closed-loop feedback mechanism dynamically balances the competing reactions.
2Productivity
If acetic acid is produced as a by-product, then downstream separation process complexity increases
Solution Approach 1:
By recycling acetic acid back to the reactor, the patent converts what would be a harmful by-product requiring complex separation into a useful catalyst promoter that simplifies the overall process. The acetic acid feeds back into the reaction zone where it enhances ethylene production, thereby reducing the need for extensive downstream separation infrastructure.
Solution Approach 2:
Instead of discarding acetic acid as waste or requiring complex separation, the patent recovers and reuses it by feeding it back into the reactor. This recovery approach transforms the separation problem into a recycling opportunity, where acetic acid serves as both a product and a catalyst, thereby simplifying downstream processing requirements.
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 the selectivity of acetic acid production, simplifies downstream separation processes, and decreases the complexity and size of the separation infrastructure, thereby enhancing the efficiency and cost-effectiveness of the ethane to ethylene conversion process.
Implementation Method 1
contacting a feed stream including ethane, oxygen, and acetic acid with an oxidative dehydrogenation catalyst in a oxidative dehydrogenation reactor
Implementation Method 2
the exothermic oxidation of hydrogen to produce water
Implementation Method 3
the endothermic removal of hydrogen from ethane
Data Source
AI summary
The present disclosure relates to limiting the production of acetic acid in an oxidative dehydrogenation process to convert ethane to ethylene. The process of oxidative dehydrogenation includes feeding acetic acid, along with ethane and oxygen into an oxidative dehydrogenation reactor where contact with a catalyst leads to conversion of the ethane into ethylene and acetic acid. By including acetic acid in the feed, the amount of acetic acid produced may be limited and the ratio of ethylene produced to ethane consumed may increase.