Olefin Production Reactor Feed Distribution for Extended Catalyst Life
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Solution Overview
Problem
Existing processes for producing short-chain olefins like ethylene and propylene from oxygenates in multi-stage fixed-bed reactors have short catalyst life and require frequent regenerations, leading to increased operating costs and reduced reactor availability for olefin production.
Innovation Solution
The process involves varying the distribution of the educt mixture to the catalyst zones by reducing the educt mixture partial stream to the last catalyst zones, allowing for increased methanol conversion and extended reaction cycles without negatively impacting propylene yield, thereby reducing the frequency of regenerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If uniform distribution of educt mixture to all catalyst zones is used, then complete utilization of catalyst volume is achieved, but reaction cycle duration is limited due to excessive carbon deposition in later zones
Solution Approach 1:
The patent applies local quality by varying the educt mixture distribution across different catalyst zones. Specifically, the first catalyst zone receives a higher proportion of the educt mixture (e.g., 60-80%) while subsequent zones receive progressively lower proportions (e.g., 10-20% each). This non-uniform distribution optimizes carbon deposition control in each zone, extending the reaction cycle duration before regeneration is required, thereby improving catalyst utilization and olefin production availability.
2Duration of action of moving object
If educt mixture partial stream to last catalyst zones is reduced, then carbon deposition is controlled and reaction cycle is extended, but methanol conversion may be impacted
Solution Approach 1:
The patent applies parameter changes by systematically adjusting the educt mixture distribution parameters across catalyst zones. The first zone operates with higher educt mixture concentration (60-80% of total) to maximize methanol conversion, while subsequent zones receive progressively lower concentrations (10-20% each). This parameter optimization ensures that sufficient methanol conversion occurs in the first zone while later zones experience controlled carbon deposition, extending the reaction cycle without sacrificing overall conversion efficiency.
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 extends the duration of reaction cycles, reduces the number of regenerations, and maintains constant carbon deposition, leading to increased catalyst life and improved process economy by minimizing regeneration costs and maintaining high propylene yields.
Implementation Method 1
conversion of an educt mixture containing steam and oxygenates, for example methanol and/or dimethyl ether (DME), in a multi-stage fixed-bed reactor. The individual stages or reaction zones of the fixed-bed reactor are covered with beds of a granular, form-selective zeolite catalyst.
Implementation Method 2
the increase in temperature in the exothermal reaction of the oxygenates to hydrocarbons in each of the succeeding reaction zones is limited to a maximum of 150 °C
Implementation Method 3
the steam is required as dilution medium and to prevent excessive carbon deposits on the catalyst
Implementation Method 4
A slow deposition of carbon on the catalyst during the synthesis operation, however, is inevitable. When the same exceeds a tolerable maximum, the production operation must be interrupted and the carbon deposits must be removed for example by controlled burning off.
Implementation Method 5
the carbon deposits must be removed for example by controlled burning off. The catalytic activity of the catalyst thereby can largely be restored, i.e. regenerated.
Data Source
Figure 1
AI summary
There is proposed a process for producing short-chain olefins by conversion of oxygenates in a multi-stage fixed-bed reactor, in which the individual stages or reaction zones are covered with beds of a granular, form-selective zeolite catalyst and the feed mixture containing oxygenates is added distributed over the reaction stages. An increase of the availability of the fixed-bed reactor for the olefin production with the same or an increased yield of short-chain olefins is achieved in that one or more reaction zones are charged with a distinctly reduced mass flow of the feed mixture containing oxygenates, wherein the reduced mass flow fraction is distributed over the other reaction zones.