Butadiene Production via Multi-Stage Adiabatic Fixed Bed
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Solution Overview
Problem
The existing processes for producing butadiene by oxidative dehydrogenation of butylene using an adiabatic fixed bed face challenges such as high energy consumption, increased compressor power, and higher loads on the oil absorption unit due to high steam requirements and nitrogen content in the feed.
Innovation Solution
A multi-stage adiabatic fixed bed process is optimized by controlling the molar ratio of a separately fed diluent to oxygen in subsequent stages, using nitrogen or carbon dioxide as diluents, and employing an iron-based catalyst to reduce steam consumption and enhance energy efficiency, while maintaining high conversion and selectivity of butadiene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a multi-stage adiabatic fixed bed is used with high steam requirements to control temperature in the catalyst bed, then the oxidative dehydrogenation reaction can proceed, but the energy consumption increases significantly
Solution Approach 1:
The patent changes the chemical composition parameter of the feed by introducing a diluent (nitrogen or carbon dioxide) to replace part of the steam. This parameter change allows temperature control through dilution rather than through steam heat capacity, thereby reducing energy consumption while maintaining catalyst bed temperature within suitable ranges.
Solution Approach 2:
The patent uses nitrogen or carbon dioxide as a substitute (copy) for steam in the feed. These diluents serve the same temperature control function as steam but with lower energy requirements, as they do not need to be heated to high temperatures like steam does.
2Productivity
If oxygen-enriched air is used to improve butylene conversion, then the conversion increases, but the nitrogen content decreases which requires more steam to control temperature
Solution Approach 1:
The patent changes the feed composition by introducing a separate diluent stream that can be nitrogen or carbon dioxide. This allows the use of oxygen-enriched air for improved conversion while the diluent compensates for reduced nitrogen content, maintaining temperature control without requiring additional steam.
Solution Approach 2:
The diluent acts as an intermediary substance that mediates between the oxygen-enriched air (which improves conversion) and the temperature control requirement. By adding the diluent separately, it balances the composition to maintain suitable temperature control conditions without relying on excess steam.
3Ease of manufacture
If air is used as the oxygen-comprising gas in the feed, then the process is simple, but the nitrogen content is high which increases the load on the oil absorption unit
Solution Approach 1:
The patent extracts or removes excess nitrogen from the feed by using oxygen-enriched air instead of normal air, and further compensates with a controlled amount of diluent. This takes out the harmful excess nitrogen that would otherwise increase the load on the oil absorption unit, while maintaining process feasibility.
Solution Approach 2:
The patent changes the oxygen content parameter of the oxygen-comprising gas from normal air (21% oxygen) to oxygen-enriched air (higher oxygen content). This parameter change reduces the nitrogen content in the feed, thereby reducing the load on the oil absorption unit while maintaining process simplicity through the addition of a diluent.
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
The optimized process significantly reduces total energy consumption and maintains high conversion and selectivity of butadiene, improving the overall economy of the process without increasing compressor power or oil absorption unit loads.
Implementation Method 1
butylene is oxidized and dehydrogenated with oxygen to form butadiene in the presence of a catalyst
Implementation Method 2
butylene is oxidized and dehydrogenated with oxygen to form butadiene
Data Source
AI summary
The present invention provides a process for producing butadiene by oxidative dehydrogenation of butylene, comprising: a reaction stage, wherein a multi-stage adiabatic fixed bed in series is used, wherein butylene, oxygen-comprising gas and water are reacted in the presence of a catalyst in each stage of the adiabatic fixed bed with the first stage of the adiabatic fixed bed being further separately fed a diluent, being nitrogen and/or carbon dioxide, and the molar ratio between this separately fed diluents and the oxygen of all the oxygen-comprising gases fed in the subsequent stage(s) of the adiabatic fixed bed being controlled, wherein the oxygen-comprising gas is air, oxygen-enriched air or oxygen, and at least one of all the oxygen-comprising gases fed in the subsequent stage(s) of the adiabatic fixed bed is oxygen-enriched air having a specific oxygen concentration or oxygen; and a post treatment stage, wherein the effluent from the last stage of the adiabatic fixed bed is treated to obtain a product butadiene. The present invention has an advantage that the whole process is with reduced total energy consumption.