Butene Metathesis Cracking Propylene Production
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Solution Overview
Problem
The increasing demand for propylene cannot be met by existing production processes, particularly due to the lack of ethylene availability in some cases, which limits the feasibility of metathesis reactions requiring both butene and ethylene.
Innovation Solution
A process that splits a butene stream into two portions, where one portion undergoes metathesis and cracking to produce propylene and ethylene, and the other portion is combined with ethylene for further metathesis, allowing for propylene production without relying on external ethylene supplies by utilizing a parallel system arrangement of reactors with metathesis and cracking catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metathesis reactions requiring both butene and ethylene are used to produce propylene, then propylene production is achieved, but the process becomes infeasible when ethylene supply is insufficient or unavailable
Solution Approach 1:
The butene stream is divided into two portions: one portion undergoes metathesis with available ethylene to produce propylene, while the other portion undergoes cracking to generate additional ethylene in situ. This segmentation allows the process to operate independently of external ethylene supply while maintaining high propylene production.
Solution Approach 2:
The cracking unit acts as an intermediary that converts butene into ethylene, which then serves as the reactant for the metathesis reaction. This intermediary process eliminates the need for external ethylene supply by generating the required ethylene within the system itself.
2Productivity
If a single metathesis reactor is used with stoichiometric ratio of 1 butene to 1 ethylene, then high propylene yield is achieved, but the process requires precise ethylene supply matching butene availability
Solution Approach 1:
The cracking reactor and metathesis reactor are merged into an integrated system where the cracking unit generates ethylene that is directly fed to the metathesis unit. This combination eliminates the need for separate ethylene supply chains and external feedstock logistics.
Solution Approach 2:
The system produces its own ethylene requirement through the cracking of butene in the first reactor. The ethylene generated from butene cracking serves the metathesis reaction, making the process self-sufficient regarding ethylene supply.
3Quantity of substance
If existing propylene production processes such as steam cracking or FCC are used, then total propylene production is maintained, but these processes cannot respond adequately to rapid increase in propylene demand
Solution Approach 1:
The process changes the operational parameters by using butene as the primary feedstock for both cracking and metathesis reactions, operating at conditions optimized for propylene selectivity. This allows the plant to respond flexibly to propylene demand by adjusting feedstock flow rates rather than being constrained by fixed ethylene-based production capacities.
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 process efficiently converts butene to propylene, achieving high yields and eliminating the need for external ethylene, thus addressing the supply chain limitations of existing methods.
Implementation Method 1
at least partially metathesizing a first portion of a first stream to form a first metathesis-reaction product, the first stream comprising butene
Implementation Method 2
at least partially cracking the first metathesis-reaction product to form a cracking-reaction product, the cracking reaction product comprising propylene and ethylene
Data Source
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AI summary
According to one or more embodiments described herein, a process for producing propylene, the process comprising at least partially metathesizing a first portion of a first stream to form a first metathesis-reaction product, at least partially cracking the first metathesis-reaction product to form a cracking-reaction product, the cracking reaction product comprising propylene and ethylene, at least partially separating ethylene from at least the cracking reaction product to form a first recycle stream, combining the first recycle stream with a second portion of the first stream to a form a mixed stream, and at least partially metathesizing the mixed stream to from a second metathesis-reaction product. In embodiments, the second metathesis-reaction product may comprise propylene, the first stream may comprise butene, and the first recycle stream may comprise ethylene.