Vinyl Aromatic Hydrocarbon Production Purification System
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Solution Overview
Problem
The existing processes for producing vinyl aromatic hydrocarbons, such as styrene, face challenges in managing impurities from recycled aromatic hydrocarbons, which lead to rapid deterioration of zeolite-based catalysts in alkylation and transalkylation reactors, resulting in short catalyst life and inefficient recycling of benzene by-products.
Innovation Solution
An integrated process that involves recycling benzene from the dehydrogenation section through a purification system using a polar solvent and molecular sieves or acid earth to remove impurities, followed by selective hydrogenation, allowing the purified benzene to be fed back into the alkylation/transalkylation guard unit, thereby extending catalyst life and improving product purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If benzene is recycled from the dehydrogenation section to the alkylation section, then the aromatic hydrocarbon is efficiently reused, but impurities in the recycled benzene cause rapid deterioration of zeolite-based catalysts
Solution Approach 1:
The patent applies preliminary action by implementing a purification train (extractive distillation with polar solvent followed by adsorption on molecular sieves or acid earth) before the recycled benzene is fed to the alkylation section. This preliminary purification removes impurities that would otherwise poison the catalyst, thereby extending catalyst life while maintaining recycling efficiency
Solution Approach 2:
The patent uses polar solvents (intermediary substance 1) for extractive distillation and molecular sieves or acid earth (intermediary substance 2) for adsorption as intermediary materials. These intermediaries selectively remove impurities from the recycled benzene stream without affecting the benzene itself, allowing efficient catalyst protection while maintaining the recycling loop
2Reliability
If impurities are removed from recycled benzene through extensive purification, then catalyst life is extended, but the process complexity and cost increase
Solution Approach 1:
The patent extracts impurities from the recycled benzene stream using two sequential extraction mechanisms: first through extractive distillation with polar solvents that selectively solvate impurities, and second through adsorption on molecular sieves or acid earth that selectively adsorb remaining impurities. This targeted extraction approach removes only the harmful components while maintaining process simplicity
Solution Approach 2:
The patent employs porous materials (molecular sieves or acid earth) as the final purification step. These porous materials provide high surface area for adsorption while maintaining a relatively simple equipment configuration, effectively removing trace impurities without requiring complex purification systems
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 significantly extends the life cycle of zeolite-based catalysts and achieves vinyl aromatic hydrocarbons with a purity higher than 99.7%, effectively managing impurities and enhancing the economic viability of the production process.
Implementation Method 1
percolating the stream comprising the aromatic hydrocarbon coming from step (h) through at least one fixed bed consisting of molecular sieves or acid earth
Implementation Method 2
feeding a stream of polar solvent to the head of the distillation column of the aromatic hydrocarbon of step (e)
Implementation Method 3
the synthesis of alkyl aromatic compounds, such as ethyl benzene or isopropyl benzene (cumene) by the reaction between an aromatic hydrocarbon, such as benzene, and an olefin, such as ethylene or propylene, in the presence of a Beta Zeolite
Data Source
AI summary
An integrated process for the production of vinyl aromatic hydrocarbons which comprises : a) synthesis of an alkyl aromatic hydrocarbon, starting from a C2-C3 olefin and an aromatic compound, in an alkylation section; b) dehydrogenation of the alkyl aromatic hydrocarbon in a dehydrogenation section with the recovery of the vinyl aromatic compound and the aromatic compound, reaction by-product of the dehydrogenation, recycled; c) treatment of the aromatic compound, before the recycling, with one or more washings with a polar solvent and with percolation through a bed of molecular sieves or acid earth.