Ethane Oxydehydrogenation Process for 1,2-Dichloroethane Production
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Solution Overview
Problem
Current processes for manufacturing 1,2-dichloroethane (DCE) and vinyl chloride (VC) using ethylene with purity below 99.8% face issues such as catalyst poisoning, high oxygen consumption, and increased production costs due to the presence of impurities, which complicates the oxychlorination process and leads to inefficient ethylene utilization and high heat management challenges.
Innovation Solution
A process involving catalytic oxydehydrogenation of ethane to produce a gas mixture containing ethylene, which is then purified and subjected to chlorination and oxychlorination reactions, with additional steps for separation and recycling to enhance ethylene conversion and reduce impurity effects, utilizing specific catalysts and conditions to optimize DCE production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ethylene with purity below 99.8% is used for oxychlorination, then production costs are reduced by simplifying separation operations, but catalyst poisoning occurs and conversion efficiency decreases
Solution Approach 1:
The process segments the conversion of ethylene to DCE into two distinct pathways: direct chlorination (which tolerates impurities) and oxychlorination (which requires pure ethylene). The direct chlorination step consumes impurities like hydrogen and heavy compounds without affecting the catalyst, while the oxychlorination step uses purified ethylene to maintain catalyst performance. This segmentation allows the use of lower purity ethylene overall while protecting the sensitive oxychlorination catalyst.
Solution Approach 2:
The patent introduces an intermediate purification step between direct chlorination and oxychlorination. The gas mixture from direct chlorination is purified to remove impurities before entering the oxychlorination reactor. This intermediary purification protects the oxychlorination catalyst from poisoning while still allowing the overall process to use lower purity feedstock, thus reducing initial separation costs.
2Productivity
If hydrogen in the ethylene stream is converted during oxychlorination, then the gas composition is adjusted, but high-purity oxygen is consumed and excessive heat is released limiting reactor capability
Solution Approach 1:
The process extracts and removes hydrogen from the ethylene stream before the oxychlorination step through the direct chlorination pathway. Hydrogen reacts with chlorine in the direct chlorination reactor to form HCl, effectively removing it from the mixture. This prevents the need to burn hydrogen during oxychlorination, avoiding excessive oxygen consumption and heat release that would limit reactor capacity.
Solution Approach 2:
The patent performs preliminary conversion of hydrogen to HCl in the direct chlorination step before the oxychlorination reaction. This preliminary action removes the problematic hydrogen component that would otherwise require high-purity oxygen and generate excessive heat during oxychlorination, thereby preserving reactor capability and reducing oxygen consumption in the main DCE production step.
3Ease of manufacture
If simplified cracking processes are used to produce lower purity ethylene, then separation costs are reduced, but impurities cause operating problems in oxychlorination reactors
Solution Approach 1:
The process segments the handling of impurities from the main oxychlorination reaction. Impurities such as heavy compounds and hydrogen are directed to the direct chlorination pathway where they are converted to useful products (HCl and DCE) without interfering with the oxychlorination catalyst. This segmentation allows simplified cracking to be used while maintaining smooth reactor operation in the oxychlorination unit.
Solution Approach 2:
The patent introduces an intermediary purification and conversion step between simplified cracking and oxychlorination. The direct chlorination reactor acts as an intermediary that converts impurities from the simplified cracking process into HCl and other manageable products. This intermediary step protects the oxychlorination reactor from operating problems caused by impurities while still allowing the use of cost-effective simplified cracking processes.
4Productivity
If a large amount of oxygen is used to burn hydrogen in a separate reactor, then hydrogen is removed, but ethylene consumption increases and safety problems arise
Solution Approach 1:
The patent uses the direct chlorination reactor as an intermediary to remove hydrogen without requiring a separate combustion reactor. Hydrogen reacts with chlorine in this intermediary step to form HCl, achieving hydrogen removal without consuming ethylene or requiring large amounts of oxygen. This eliminates the safety problems associated with large-scale hydrogen combustion while maintaining effective hydrogen removal.
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 reduces production costs by allowing the use of lower purity ethylene, minimizes hydrogen generation, and improves the efficiency of ethylene conversion, while avoiding catalyst poisoning and heat management issues, resulting in a more economical and effective production of DCE and VC.
Implementation Method 1
a) the stream of ethane is subjected to a catalytic oxydehydrogenation producing a gas mixture containing ethylene, unconverted ethane, water and secondary constituents
Implementation Method 2
c) after an optional additional purification step, said dry gas mixture is subjected to an absorption A1 which consists of separating said gas mixture into a fraction enriched with the compounds that are lighter than ethylene containing some of the ethylene (fraction A) and into a fraction F1
Implementation Method 3
d) fraction A is conveyed to a chlorination reactor in which most of the ethylene present in fraction A is converted to 1,2-dichloroethane
Implementation Method 4
g) fraction B is conveyed to an oxychlorination reactor in which most of the ethylene present in fraction B is converted into 1,2-dichloroethane
Implementation Method 5
f) fraction F1, optionally containing fraction F2 recovered in step e) of absorption A2, is subjected to a desorption D which consists of separating fraction F1 into a fraction enriched with ethylene (fraction B) and into a fraction F3
Data Source
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AI summary
Process for the manufacture of 1,2-dichloroethane starting from a stream of ethane according to which: a) the stream of ethane is subjected to a catalytic oxydehydrogenation producing a gas mixture containing ethylene, unconverted ethane, water and secondary constituents; b) said gas mixture is optionally washed and dried thus producing a dry gas mixture; c) after an optional additional purification step, said dry gas mixture is subjected to an absorption Al which consists of separating said gas mixture into a fraction enriched with the compounds that are lighter than ethylene containing some of the ethylene (fraction A) and into a fraction Fl; d) fraction A is conveyed to a chlorination reactor in which most of the ethylene present in fraction A is converted to 1,2-dichloroethane and optionally the 1,2-dichloroethane obtained is separated from the stream of products derived from the chlorination reactor; e) optionally the stream of products derived from the chlorination reactor, from which the 1,2-dichloroethane has optionally been extracted, is subjected to an absorption A2 which consists of separating said stream into a fraction enriched with ethane F2 which is then conveyed back to fraction Fl, and into a fraction enriched with compounds that are lighter than ethane F2'; f) fraction Fl, optionally containing fraction F2 recovered in step e) of absorption A2, is subjected to a desorption D which consists of separating fraction Fl into a fraction enriched with ethylene (fraction B) and into a fraction F3, optionally containing the 1,2-dichloroethane formed in the chlorination reactor then extracted if it has not been extracted previously, which is recycled to at least one of the absorption steps, optionally after an additional treatment intended to reduce the concentration of compounds that are heavier than ethane in fraction F3; g) fraction B is conveyed to an oxychlorination reactor in which most of the ethylene present in fraction B is converted into 1,2-dichloroethane, the 1,2- dichloroethane obtained is separated from the stream of products derived from the oxychlorination reactor and is optionally added to the 1,2-dichloroethane formed in the chlorination reactor; and h) the stream of products derived from the oxychlorination reactor, from which the 1,2-dichloroethane has been extracted, optionally containing an additional stream of ethane previously introduced in one of steps b) to g), is optionally recycled to step a) after having been optionally purged of gases and/or after an optional treatment in order to eliminate the chlorinated products contained therein.