Hexene-1 Separation via Recirculation Heat Integration
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Solution Overview
Problem
Current processes for separating hexene-1 from ethylene trimerization reaction mixtures are inefficient in terms of selectivity and energy efficiency, leading to high costs and operational challenges in producing hexene-1 with sufficient purity for use as a co-monomer in polyethylene manufacturing.
Innovation Solution
A multi-step distillation process involving multiple columns, where the effluent from the ethylene trimerization reaction is separated into fractions, with recirculation loops to optimize the separation of hexene-1 and butene-1, and the use of a recirculation loop to cool and reboil the distillation columns, reducing energy consumption and improving separation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple distillation columns operating in series are used to separate hexene-1 from the trimerization effluent, then the purity of hexene-1 is improved, but the energy consumption and operational complexity increase
Solution Approach 1:
The patent implements a recirculation loop where a portion of the bottoms fraction from the second distillation column is returned to the column to provide reflux, improving separation efficiency and hexene-1 purity while optimizing energy utilization of the reboiler and condenser systems
Solution Approach 2:
The bottoms fraction from the second distillation column serves multiple functions: it provides reflux for the same column to enhance separation, acts as cooling medium for the reaction zone, and maintains the distillation column's thermal balance, thereby reducing external energy requirements
2Manufacturing precision
If multiple distillation columns operating in series are used to separate hexene-1 from the trimerization effluent, then the purity of hexene-1 is improved, but the device complexity increases
Solution Approach 1:
The recirculation loop creates a feedback mechanism where the bottoms fraction is continuously returned to the second distillation column, automatically maintaining optimal reflux conditions and separation efficiency without requiring complex external control systems
Solution Approach 2:
The patent combines the reflux function with the product separation function by using the bottoms fraction from the second column as the reflux stream, merging what would otherwise be separate streams and simplifying the overall process configuration
3Use of energy by moving object
If the bottoms fraction from the second distillation column is recycled to the reaction zone, then the energy efficiency is improved, but the separation selectivity may be compromised
Solution Approach 1:
The patent applies partial recirculation by returning only a portion of the bottoms fraction to the reaction zone while directing another portion to the recirculation loop of the second distillation column, thereby balancing energy efficiency improvements with maintenance of separation selectivity
Solution Approach 2:
The recirculation stream is specifically targeted to the second distillation column where it provides localized reflux to enhance hexene-1 separation, while the reaction zone receives a controlled amount of recycled material to maintain optimal reaction conditions without compromising overall selectivity
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
The process achieves improved selectivity and energy efficiency in separating hexene-1, reducing the need for additional energy inputs and lowering installation costs by effectively recycling heat and using solvent recirculation to enhance separation and reboiling processes.
Implementation Method 1
the separation of the oligomerization products can be carried out with separation means, such as distillation columns, operating in series and based on the differences in boiling points of the compounds to be separated
Implementation Method 2
said recirculation loop making it possible to cool the reaction section and to reboil said column of step b)
Data Source
AI summary
A process for separating hexene-1 from a mixture from a reaction section of ethylene trimerization is described, the process comprising at least the following steps: a) the mixture from the ethylene trimerization reaction is separated in a first distillation column into a head fraction comprising ethylene and a bottom fraction; b) at least a portion of the effluent from the bottom fraction from step a) is separated in at least one other distillation column into a head fraction comprising hexene-1 and butene-1 and a bottom fraction.(c) In a final distillation column, at least a portion of the fraction comprising 1-hexene and 1-butene from step (b) is separated into a head fraction comprising mainly 1-butene and a bottom fraction comprising mainly 1-hexene; and in said process: at least a portion of an effluent from the bottom fraction from step (b) is returned to the reaction section and at least another portion of said bottom fraction from step (b) is used in at least one recirculation loop connecting the reaction section and the column of said step (b), said recirculation loop serving to cool the reaction section and to reboil said column of step (b).