Liquid Phase Isomerization for Propylene Yield in Metathesis
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Solution Overview
Problem
The growing demand for propylene has outpaced the demand for ethylene, and existing processes for producing propylene from steam crackers and fluid catalytic cracking units are not sufficient to meet this demand, necessitating improved methods for increasing propylene yield from C4 olefin streams at low cost and low energy.
Innovation Solution
The process involves isomerizing a hydrocarbon stream under liquid phase conditions in an isomerization reactor to convert 1-butene to 2-butene, followed by a metathesis reaction with ethylene, optimizing the pentene content in the recycle stream to reduce side reactions and increase the availability of 2-butene for propylene production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional metathesis processes are used to produce propylene from C4 olefin streams, then propylene can be produced, but the propylene yield is insufficient to meet growing demand and energy consumption is high
Solution Approach 1:
The process performs preliminary isomerization of 1-butene to 2-butene in a first-stage auto-metathesis reaction before the main metathesis reaction with ethylene. This preliminary conversion of 1-butene to 2-butene optimizes the feed composition for the subsequent metathesis reaction, thereby increasing propylene yield and reducing energy consumption by minimizing the need for additional processing steps.
Solution Approach 2:
The process implements continuous recycling of unreacted C4 olefins and other streams back to the metathesis reactor. This continuous circulation ensures that all feed materials are fully utilized for propylene production, maximizing productivity and minimizing energy waste by avoiding repeated processing of unconverted materials.
2Productivity
If 1-butene is directly used in metathesis reaction, then the process is simple, but 2-butene availability is limited reducing propylene production efficiency
Solution Approach 1:
A first-stage auto-metathesis reactor is introduced to preliminarily convert 1-butene to 2-butene before the main metathesis reaction with ethylene. This preliminary action ensures adequate 2-butene availability for efficient propylene production while maintaining overall process simplicity through integrated reactor design.
Solution Approach 2:
The isomerization and metathesis functions are merged into an integrated two-stage process where the first-stage auto-metathesis serves both as a reaction step and as a source of 2-butene for the main reaction. This combining of functions achieves the desired 2-butene availability without significantly increasing process complexity.
3Manufacturing precision
If pentene content in recycle stream is not optimized, then side reactions increase reducing selectivity, but optimizing pentene content requires additional process control
Solution Approach 1:
The process implements feedback control by recycling unreacted C4 olefins and optimizing pentene content in the recycle stream based on its impact on side reactions. By monitoring and adjusting pentene levels in the recycle stream, the process maintains high selectivity for propylene production while managing process control complexity through systematic feedback mechanisms.
Solution Approach 2:
The process optimizes selectivity by controlling the pentene content parameter in the recycle stream. By adjusting this specific parameter within optimal ranges, side reactions are minimized and propylene selectivity is maximized, achieving manufacturing precision through parameter optimization rather than complex process modifications.
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 enhances propylene yield by optimizing the 2-butene content in the metathesis reaction, reducing equipment size and energy consumption by at least 15% and 10%, respectively, while extending metathesis catalyst life and improving selectivity and conversion.
Implementation Method 1
isomerizing under liquid phase conditions a hydrocarbon stream in an isomerization reactor, and isomerized hydrocarbon stream is provided to a metathesis reactor
Implementation Method 2
metathesis reaction with ethylene
Data Source
AI summary
The present disclosure relates to processes for improved yields of propylene via metathesis, primarily from the conversion of C4 and C5+ olefins obtained from steam or fluid catalytic cracking of hydrocarbons. In particular, the present disclosure relates to processes for preparing propylene by improved isomerization of 1-butene to 2-butene relative to the metathesis reaction.