Benzene Recycle Purification via Acidic Adsorbent Bed
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Solution Overview
Problem
The production of styrene results in a benzene by-product contaminated with high levels of basic nitrogen impurities, which deactivates the molecular sieve catalyst in the alkylation reactor, making it impractical to recycle the benzene back into the process due to catalyst poisoning.
Innovation Solution
Passing the benzene by-product through a dedicated adsorbent bed comprising acidic clay, alumina, or an acidic ion exchange resin to remove basic nitrogen compounds, reducing their concentration to less than 50 ppb, allowing the purified benzene to be recycled back to the alkylation reactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If benzene by-product is recycled to the alkylation reactor, then resource efficiency is improved, but catalyst activity deteriorates due to nitrogen impurity accumulation
Solution Approach 1:
The patent extracts and removes basic nitrogen impurities from the benzene by-product stream using an acidic adsorbent bed before recycling the purified benzene to the alkylation reactor. This separation allows the beneficial recycling of benzene while eliminating the harmful nitrogen compounds that would otherwise poison the catalyst.
Solution Approach 2:
The patent introduces an acidic adsorbent bed as an intermediary treatment unit between the distillation column and the alkylation reactor. This intermediary component captures basic nitrogen impurities through acid-base interactions, enabling the benzene recycle stream to be compatible with the catalyst while maintaining resource efficiency.
2Object-affected harmful factors
If corrosion inhibitor is added to control corrosion, then equipment protection is improved, but nitrogen impurity concentration in benzene by-product worsens
Solution Approach 1:
The patent introduces an acidic adsorbent bed as an intermediary treatment unit between the distillation column and the alkylation reactor. This intermediary component captures basic nitrogen impurities through acid-base interactions, enabling the benzene recycle stream to be compatible with the catalyst while maintaining resource efficiency.
Solution Approach 2:
The patent extracts and removes basic nitrogen impurities from the benzene by-product stream using an acidic adsorbent bed before recycling the purified benzene to the alkylation reactor. This separation allows the beneficial recycling of benzene while eliminating the harmful nitrogen compounds that would otherwise poison the catalyst.
3Reliability
If benzene by-product is sent to transalkylation reactor instead, then catalyst poisoning is reduced, but process complexity increases
Solution Approach 1:
The patent extracts and removes basic nitrogen impurities from the benzene by-product stream using an acidic adsorbent bed before recycling the purified benzene to the alkylation reactor. This separation allows the beneficial recycling of benzene while eliminating the harmful nitrogen compounds that would otherwise poison the catalyst.
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 effectively purifies the benzene stream, preventing catalyst deactivation and enabling its safe recycling, thereby optimizing styrene production by maintaining catalyst activity and reducing corrosion issues.
Implementation Method 1
Passing the benzene by-product through a dedicated adsorbent bed comprising acidic clay, alumina, or an acidic ion exchange resin to remove basic nitrogen compounds
Implementation Method 2
passing at least part of the benzene/toluene fraction, without prior fractionation to remove toluene, through a bed of an adsorbent comprising at least one of an acidic clay, alumina, and an acidic ion exchange resin to remove basic nitrogenous impurities therefrom
Data Source
AI summary
In a process for producing styrene, benzene is alkylated with ethylene to produce ethylbenzene and at least some of the ethylbenzene is dehydrogenated to produce styrene, together with benzene and toluene as by-products. At least part of the benzene by-product is passed through a bed of an adsorbent comprising at least one of an acidic clay, alumina, an acidic ion exchange resin and an acidic molecular sieve to remove basic nitrogenous impurities therefrom and produce a purified benzene by-product, which is then recycled to the alkylation step.