Naphtha to Paraffins Conversion with Hydrocracked Pyrolysis Gasoline Recycling
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Solution Overview
Problem
The global demand for ethylene and propylene exceeds supply, particularly in regions lacking ethane resources, necessitating a more efficient and economical conversion process for naphtha to light olefins.
Innovation Solution
A process involving the conversion of naphtha to ethane and propane using a molecular sieve catalyst, followed by thermal cracking of ethane to ethylene and propylene, with recycling of pyrolysis gasoline for further processing to enhance yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If naphtha steam cracking is used to produce ethylene, then ethylene can be produced in regions lacking ethane supply, but the production cost is higher and ethylene yield is only 30%-35%
Solution Approach 1:
The process segments the naphtha cracking process into two distinct stages: first converting naphtha to paraffins (ethane/propane) in a reactor, then thermally cracking the separated ethane stream to ethylene. This segmentation allows optimization of each stage independently, achieving higher ethylene yield from the ethane cracking step while the paraffin conversion step can be optimized for efficiency.
Solution Approach 2:
The process performs preliminary conversion of naphtha to paraffins before the final ethylene production step. By pre-converting naphtha to ethane/propane in the first reactor stage, the system prepares the feedstock in a form that is more efficiently converted to ethylene in the subsequent thermal cracking step, thereby increasing overall yield.
2Productivity
If naphtha steam cracking is used to meet growing ethylene demand, then supply can be increased, but environmental concerns and carbon dioxide emissions increase
Solution Approach 1:
The process changes the operational parameters by conducting paraffin conversion at lower temperatures (300-600°C) compared to conventional high-temperature steam cracking. This parameter change reduces energy consumption and associated carbon dioxide emissions while maintaining high ethylene production capacity through the two-stage process efficiency.
Solution Approach 2:
The process converts the typically low-value by-products (pyrolysis gasoline, pyrolysis oil) into beneficial feedstocks by recycling them back to the paraffin conversion reactor. This converts waste streams into useful materials that can be further converted to ethane and propane, then to ethylene, thereby increasing overall productivity while reducing waste disposal emissions.
3Quantity of substance
If conventional steam cracking with steam mixing is used, then olefin yield is enhanced and carbon deposition is reduced, but process complexity and energy consumption increase
Solution Approach 1:
The process extracts and removes steam from the reaction system entirely, replacing it with hydrogen as the reaction medium. This extraction of steam eliminates the need for steam injection infrastructure and associated process complexity while maintaining high olefin yields through the hydrogen-rich environment that prevents carbon deposition.
Solution Approach 2:
The process changes the chemical environment by using hydrogen instead of steam as the reaction medium. This parameter change eliminates carbon deposition issues inherent in steam cracking without requiring steam mixing equipment, thereby reducing process complexity while maintaining high ethylene and propylene yields.
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
Significantly increases the production of ethylene and propylene while reducing carbon dioxide emissions and operational costs, achieving yields of over 80% light olefins from naphtha feedstock.
Implementation Method 1
contacting a naphtha stream with a catalyst and hydrogen to produce a light paraffinic stream
Implementation Method 2
contacting a naphtha stream with a catalyst and hydrogen to produce a light paraffinic stream
Implementation Method 3
thermally cracking the ethane stream to produce a pyrolysis gasoline stream
Implementation Method 4
thermally cracking the ethane stream to produce ethylene, propylene and a pyrolysis gasoline stream
Implementation Method 5
The pyrolysis gasoline stream is hydrocracked to provide a cracked naphtha stream
Data Source
AI summary
A process for converting naphtha is disclosed. The process comprises contacting a naphtha stream with a catalyst and hydrogen to produce a light paraffinic stream. The light paraffinic stream is separated into an ethane stream and a propane stream. The ethane stream is thermally cracked to produce ethylene and a pyrolysis gasoline by-product stream. The pyrolysis gasoline stream is hydrocracked to provide a cracked naphtha stream. The cracked naphtha stream may be contacted with a catalyst and hydrogen with the naphtha stream.