Ethylene Production via Catalytic Oxychlorination and Cracking
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Solution Overview
Problem
Current methods for producing ethylene from ethane, such as thermal cracking, result in low yields and require extensive processing to separate high-purity ethylene due to the formation of numerous byproducts, leading to high capital investment and average operating efficiencies.
Innovation Solution
A two-step process using an oxychlorination catalyst containing copper, lead, and alkali metal chlorides to convert ethane to ethyl chloride, followed by cracking ethyl chloride over a catalyst like zinc chloride or silica alumina to produce ethylene, with optional recycling of hydrogen chloride, optimizing operating conditions for temperature and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermal cracking is used to produce ethylene from ethane, then ethylene can be produced, but numerous byproducts are formed limiting the yield to about 80 percent
Solution Approach 1:
The patent changes the reaction parameters from thermal cracking (high temperature, no catalyst) to catalytic oxychlorination followed by catalytic dehydrochlorination. The first reaction uses an oxychlorination catalyst at 350-400°C to convert ethane to ethyl chloride with water as byproduct, then the second reaction uses a cracking catalyst at 325-375°C to convert ethyl chloride to ethylene. This parameter change eliminates the formation of various byproducts (hydrogen, methane, butane, higher molecular weight hydrocarbons) that occur in thermal cracking, achieving higher ethylene yield and purity.
Solution Approach 2:
The patent introduces ethyl chloride as an intermediary substance to facilitate the conversion of ethane to ethylene. Instead of directly cracking ethane to ethylene (which produces many byproducts), the process first converts ethane to ethyl chloride through oxychlorination, then converts ethyl chloride to ethylene through dehydrochlorination. This intermediary approach allows for cleaner reaction pathways and higher product purity.
2Manufacturing precision
If thermal cracking is used to produce ethylene from ethane, then ethylene production is achieved, but extensive processing is needed to separate high-purity ethylene
Solution Approach 1:
The patent changes the chemical reaction pathway to produce ethylene with higher inherent purity. By using catalytic oxychlorination followed by catalytic dehydrochlorination, the process produces ethylene with minimal byproducts, reducing the need for extensive separation processing. The reaction conditions (temperature ranges of 350-400°C for oxychlorination and 325-375°C for cracking, pressures of 1-10 atmospheres) are optimized to maximize ethylene purity.
3Productivity
If thermal cracking is used to produce ethylene from ethane, then ethylene can be produced, but capital investment is substantial and operating efficiencies are average
Solution Approach 1:
The patent changes the process parameters to use lower temperatures (350-400°C for oxychlorination, 325-375°C for cracking) compared to thermal cracking temperatures, and introduces catalytic systems that operate more efficiently. The oxychlorination catalyst contains copper, lead, and alkali metal chlorides, while the cracking catalyst uses zinc chloride, activated carbon, or silica alumina. These parameter changes result in higher operating efficiencies and reduced capital investment requirements.
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 enhances ethylene yield and purity while minimizing byproduct formation, achieving favorable economics and robust operational efficiency by maintaining catalyst activity and reducing byproduct formation, with no net consumption of hydrogen chloride.
Implementation Method 1
a stream comprising ethane, oxygen and hydrogen chloride is passed over an oxychlorination catalyst to produce ethyl chloride and water
Implementation Method 2
ethane, oxygen and hydrogen chloride are passed over a catalyst to produce ethyl chloride and water
Implementation Method 3
The second reaction converts ethyl chloride in the presence of a second catalyst to ethylene and hydrogen chloride
Implementation Method 4
cracking ethyl chloride over a catalyst like zinc chloride or silica alumina to produce ethylene
Data Source
AI summary
Ethylene is produced from ethane in three steps: first, ethane is oxychlorinated to produce ethyl chloride and water; second, ethyl chloride from the first step is cracked to produce ethylene and hydrogen chloride; and third, the hydrogen chloride from the second step is recycled to the front step.