Deep Catalyst Bed Oxidative Dehydrogenation Process
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Solution Overview
Problem
Existing butadiene production processes face limitations due to shallow catalyst beds, leading to oxygen breakthrough, reduced catalyst life, and lower butadiene purity, primarily because of restricted bed depth and inadequate control over oxidative dehydrogenation reactions.
Innovation Solution
A method involving a multilayer catalyst bed with a deeper oxidative dehydrogenation catalyst layer, controlled oxygen feed, and temperature management using thermocouples to ensure reactions occur in the lower layers, preventing oxygen breakthrough and extending catalyst life, while maintaining high butadiene purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the catalyst bed depth is increased to improve butadiene yield and prevent oxygen breakthrough, then the reactor complexity and pressure drop increase
Solution Approach 1:
The catalyst bed is segmented into multiple functional layers with distinct purposes: the first layer (60-90 cm depth) contains oxidative dehydrogenation catalyst for butene conversion, the second layer (30-60 cm depth) contains aldehyde and alkyne removal catalyst for product purification, and an inert support layer at the bottom. This segmentation allows each layer to optimize its specific function while collectively achieving high butadiene yield and preventing oxygen breakthrough without excessive reactor complexity.
2Productivity
If the oxidative dehydrogenation catalyst bed depth is increased to improve reaction efficiency, then the risk of oxygen breakthrough to the AAR catalyst increases
Solution Approach 1:
A bed depth of 60-90 cm for the oxidative dehydrogenation catalyst is selected as an optimal intermediary value that balances reaction efficiency and oxygen consumption. This depth is sufficient to ensure complete oxygen consumption before the effluent reaches the AAR catalyst, preventing oxygen breakthrough and catalyst damage, while not being so deep as to cause excessive pressure drop or reactor complexity.
3Device complexity
If the catalyst bed depth is limited to shallow depths to reduce reactor complexity, then oxygen breakthrough occurs and catalyst life decreases
Solution Approach 1:
The oxidative dehydrogenation catalyst bed is designed with sufficient depth (60-90 cm) to preliminarily consume all oxygen from the feed stream before the effluent reaches the AAR catalyst. This preliminary oxygen consumption action prevents oxygen breakthrough that would otherwise damage the AAR catalyst and shorten its life, thereby extending the operational life of the catalyst system without excessive reactor complexity.
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 allows for longer catalyst life, higher butadiene yield, and improved purity by preventing oxygen breakthrough and optimizing reaction zones within the catalyst bed, thereby enhancing process efficiency and productivity.
Implementation Method 1
the butenes were converted to butadiene accompanied by the liberation of a great deal of heat
Implementation Method 2
oxidatively dehydrogenating said reactor feed stream over a catalyst
Implementation Method 3
heat a mixture of hydrocarbons, preferably butenes, oxygen and steam to a temperature in excess of 260°C
Implementation Method 4
a plurality of remotely readable thermocouples are inserted into the oxidation/dehydrogenation portion of the bed to monitor the temperature therein
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
Butadiene is made from a butene rich feed, passing a superheated butene rich feed including superheated steam and oxygen at a temperature of at least about 343°C (650° F) over a catalyst bed having a depth of over about 69 cm (27 inches) of granules of ferritic oxidative dehydrogenation catalyst. Inlet conditions being controlled such that the oxidative dehydrogenation reactions initially occur in the lower most layers of catalyst. Process control includes monitoring the temperature throughout the bed and increasing the inlet temperature in response to a drop in the temperature in the active layer, when the active layer of oxidative dehydrogenation catalyst begins to become deactivated so that the reaction zone moves upwardly in the oxidative dehydrogenation bed.