Ethane Oxidative Dehydrogenation CFB Reactor
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Solution Overview
Problem
Current oxidative dehydrogenation processes for converting alkanes to olefins face challenges such as low conversion per pass and selectivity due to operating below oxidative combustion limits, which results in high costs and potential decomposition issues, limiting industrial adoption.
Innovation Solution
A process involving a supported catalyst with a formula such as VxMo y Nb z Te m Me n O p, where Me is a metal like Ta, Ti, or W, is used in a fluidized bed reactor with a unique regeneration system, allowing for operation above the upper flammability limit of oxygen, achieving high conversion and selectivity of alkanes to alkenes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxidative dehydrogenation is operated below the lower oxidative combustion limits, then selectivity is maintained, but conversion per pass becomes low
Solution Approach 1:
The patent inverts the conventional operating approach by operating above the upper oxidative combustion limits rather than below the lower limits. This reversal enables both high conversion and high selectivity to be achieved simultaneously, resolving the traditional trade-off between these two parameters.
Solution Approach 2:
The patent changes the operating parameters by operating at temperatures and oxygen concentrations above the upper combustion limits, which is a fundamental parameter change from conventional ODH processes. This parameter change enables the reaction to proceed with both high conversion and high selectivity.
2Productivity
If oxidative dehydrogenation is operated above the upper oxidative combustion limits, then conversion and selectivity are high, but the process requires very short dwell times
Solution Approach 1:
The patent applies the 'rushing through' principle by implementing very short dwell times (less than 0.1 seconds) in the reactor. This allows the reaction to complete the high conversion process before unwanted side reactions can occur, enabling operation above combustion limits while maintaining selectivity.
Solution Approach 2:
The patent uses a regenerative catalyst that is pre-loaded with oxygen in a separate regeneration zone. This preliminary action of pre-oxidizing the catalyst eliminates the need for direct oxygen contact with the hydrocarbon feed, allowing the reaction to proceed above combustion limits without immediate combustion.
3Temperature
If conventional ODH processes are used, then operating temperatures are lower than steam cracking, but decomposition risks increase
Solution Approach 1:
The patent segments the process into two distinct zones: a regeneration zone where the catalyst is oxidized at controlled temperatures, and a reaction zone where the ODH occurs with very short contact time. This segmentation allows temperature control that minimizes decomposition while maintaining effectiveness.
Solution Approach 2:
The patent implements a continuous regenerative process where the catalyst is constantly cycled between oxidation and reduction states. This continuous action maintains high catalyst activity without requiring high temperatures that would increase decomposition risk, as the catalyst is continuously replenished with oxygen.
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 enables a one-pass process with alkane conversion not less than 50% and selectivity to alkenes not less than 90%, overcoming the limitations of previous methods by maintaining high selectivity and reducing the risk of decomposition.
Implementation Method 1
oxidative dehydrogenation of one or more alkanes selected from the group consisting of ethane, propane and mixtures thereof to produce alpha olefins
Implementation Method 2
contacting the feed with a mixed oxide catalyst containing vanadium, molybdenum, tantalum and tellurium
Implementation Method 3
passing through an oxidative dehydrogenation reactor containing a fluidized bed of said catalyst
Implementation Method 4
feeding said reduced catalyst to a regeneration reactor and passing a stream of air optionally with additional nitrogen at a temperature from 250°C to 400°C and pressures from 3.447 to 689.47 kPa through said bed to oxidize said catalyst
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
Ethane may be catalytically oxidatively dehydrogenated to ethylene at high conversions and high selectivity in a circulating fluidized bed (CFB) reactor in the presence of oxygen in the feed in an amount above the flammability limit. The reactor has an attached regeneration reactor to regenerate the catalyst and cycle back to the CFB.