Dividing Wall Column for Cumene Separation
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Solution Overview
Problem
Current cumene production processes face challenges with the formation of dialkylated benzenes and propylene oligomers, which reduce yield and purity, and require multiple distillation columns, leading to high energy consumption and capital costs.
Innovation Solution
A process utilizing a dividing wall distillation column to separate cumene from reaction mixtures, replacing traditional benzene and cumene columns, which allows for more efficient separation and reduced energy requirements by integrating two parallel fractionation zones within a single column.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional three distillation columns are used for separation, then complete separation of benzene, cumene, and polyisopropylbenzene is achieved, but energy consumption and capital costs increase significantly
Solution Approach 1:
The patent combines the functions of two distillation columns (benzene column and cumene column) into a single dividing wall column. The dividing wall creates two distinct separation zones within one column, allowing simultaneous separation of benzene from the overhead and cumene from the side draw, while maintaining the separation purity of traditional multiple columns but reducing energy consumption and capital costs.
2Manufacturing precision
If traditional three distillation columns are used for separation, then complete separation of benzene, cumene, and polyisopropylbenzene is achieved, but capital costs and equipment count increase
Solution Approach 1:
The patent merges multiple distillation columns into a single dividing wall column structure. By incorporating a dividing wall that creates separate fractionation zones, the system achieves the separation capabilities of multiple columns while using fewer physical equipment units, thereby reducing capital costs and equipment count.
Solution Approach 2:
The dividing wall column performs multiple separation functions simultaneously within a single piece of equipment. It separates benzene from the overhead, cumene from the side draw, and allows polyisopropylbenzene to be recovered from the bottoms, making the single column as versatile as the traditional three-column system.
3Manufacturing precision
If large molar excess of benzene is used to minimize dialkylated products, then dialkylation is reduced, but propylene oligomerization increases
Solution Approach 1:
The patent employs a transalkylation catalyst with specific properties (strong acidity and appropriate pore structure) that changes the reaction parameters to favor transalkylation over oligomerization. This catalyst enables the system to process the necessary benzene excess while converting dialkylated benzenes back to cumene without significant propylene oligomerization.
Solution Approach 2:
The transalkylation reactor acts as an intermediary step between the alkylation reactor and the distillation system. It processes the dialkylated benzenes formed in the alkylation step and converts them back to cumene, serving as a mediator that prevents these unwanted by-products from entering the separation system.
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 results in higher cumene purity, reduced benzene loss, lower capital costs, and decreased energy consumption, while minimizing the formation of unwanted by-products like propylene oligomers, thereby enhancing overall process efficiency.
Implementation Method 1
The alkylation zone effluent and the transalkylation zone effluent are passed into a dividing wall fractionation column which is operated at fractionation conditions
Data Source
AI summary
This cumene process involves contacting, in an alkylation zone, a first benzene recycle stream and a propylene feed stream with an alkylation catalyst to form cumene. In a transalkylation zone, a polyisopropyl benzene recycle stream and a second benzene recycle stream are contacted with a transalkylation catalyst to form additional cumene. The effluents are passed into a dividing wall distillation column. A cumene stream is removed from an intermediate point of the dividing wall fractionation column; a first benzene recycle stream is removed from a first end and a heavy aromatics stream is removed from a second end. A second benzene recycle stream is removed from an intermediate point located between the first end and the cumene stream. A polyisopropyl benzene stream is removed from an intermediate point of located between the second end and the cumene stream.