Oxidative Dehydrogenation Coproduction via Two-Reactor Series
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Solution Overview
Problem
Current oxidative dehydrogenation (ODH) processes for converting ethane to ethylene face challenges in achieving high selectivity and efficiency, particularly in producing valuable coproducts like ethanol and acetaldehyde, with existing catalysts often requiring high temperatures and being limited in product diversification.
Innovation Solution
A method involving a system with two ODH reactors in series, where the first reactor converts ethane to ethylene and carbon dioxide, and the second reactor converts ethylene into ethanol and acetaldehyde, using a low-temperature catalyst that operates at less than 450°C, with oxygen removal from the first reactor effluent to prevent oxidation of ethanol and acetaldehyde to acetic acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional ODH processes operate at high temperatures to achieve good conversion, then ethylene production is improved, but catalyst deactivation and coke formation increase
Solution Approach 1:
The patent changes the operating temperature parameter from traditional high temperatures (>500°C) to low temperatures (200-450°C), which fundamentally alters the reaction pathway and catalyst behavior. This parameter change enables sustained catalyst activity while maintaining ethylene production through a different mechanistic route involving oxygenated species
Solution Approach 2:
The patent introduces oxygen or oxygen-containing compounds as reactants to create an oxidative dehydrogenation environment. This strong oxidizing condition prevents coke formation by oxidizing carbon deposits and maintains catalyst activity through controlled oxidation reactions, resolving the contradiction between productivity and catalyst stability
2Productivity
If ODH process is optimized for high ethylene selectivity, then ethylene production is improved, but coproduct formation (ethanol, acetaldehyde) is limited
Solution Approach 1:
The patent designs the ODH process to serve multiple functions simultaneously: it produces ethylene as the primary product while also generating valuable coproducts (ethanol, acetaldehyde, acetic acid) through controlled oxidation reactions. The same reactor system and catalyst perform both ethylene synthesis and coproduct formation, enabling product diversification without sacrificing ethylene selectivity
Solution Approach 2:
The patent employs dynamic control of reaction conditions (temperature, oxygen partial pressure, contact time) to adjust the product distribution. By varying these parameters, the process can be tuned to produce different ratios of ethylene and coproducts based on market demands, providing versatility while maintaining high ethylene production
3Productivity
If oxygen is present in the second reactor to continue oxidation reactions, then coproduct formation is improved, but over-oxidation to acetic acid increases
Solution Approach 1:
The patent applies partial oxidation by carefully controlling the oxygen quantity and reaction conditions in the second reactor. Instead of complete oxidation to CO2 and H2O, the process stops at intermediate products (ethanol, acetaldehyde) by using limited oxygen amounts and optimized residence times, preventing over-oxidation to acetic acid while still achieving coproduct formation
Solution Approach 2:
The patent uses a two-reactor continuous process where the first reactor produces ethylene and the second reactor continuously converts ethylene to coproducts. This continuous action allows precise control of oxidation extent by maintaining steady-state conditions, ensuring coproduct formation without excessive oxidation to acetic acid
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 enhances the production of ethylene, ethanol, and acetaldehyde, improving the profitability of the ODH reactor system by adjusting the balance of products based on market needs and maintaining efficient low-temperature operations, thereby overcoming the limitations of traditional ODH processes.
Implementation Method 1
contacting ethane with an ODH catalyst in presence of oxygen in a first reactor to dehydrogenate ethane to ethylene
Implementation Method 2
contacting the first-reactor effluent with an ODH catalyst in the second reactor to form at least ethanol and acetaldehyde
Implementation Method 3
contacting ethane with an ODH catalyst in presence of oxygen at a temperature of less than 450° C. in a first ODH reactor
Data Source
AI summary
A system and method for coproduction in the production of ethylene, including contacting ethane with an oxidative dehydrogenation (ODH) catalyst in presence of oxygen in a first reactor to dehydrogenate ethane to ethylene, and contacting a first-reactor effluent with an ODH catalyst in a second reactor to form ethanol and acetaldehyde.