Normal Paraffin Concentration via Isomerization and Recycling
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Solution Overview
Problem
The challenge in the steam cracking process is to efficiently separate and increase the concentration of normal paraffins in feed streams, as existing methods are hindered by the presence of iso-paraffins, naphthenes, and aromatics, which are difficult to separate and convert effectively, leading to suboptimal yields of ethylene and propylene.
Innovation Solution
A process involving the separation of naphtha feed streams into normal and non-normal paraffin streams, followed by isomerization over specific catalysts like sulfated zirconia or chlorided alumina at controlled temperatures and pressures, converting non-normal paraffins to normal paraffins, and recycling C4+ hydrocarbons to enhance the normal paraffin concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fractional distillation is used to separate hydrocarbons, then separation of feed components is achieved, but separation of naphthenes and aromatics from the feed stream is difficult
Solution Approach 1:
The patent extracts and removes undesirable components (naphthenes and aromatics) from the feed stream through selective adsorption using specific adsorbents, separating them from the desired normal paraffins and iso-paraffins that are needed for steam cracking
Solution Approach 2:
The patent uses different adsorbents with specific local properties tailored to selectively adsorb naphthenes and aromatics while allowing normal and iso-paraffins to pass through, creating zones of selective separation in the adsorption bed
2Quantity of substance
If isomerization is performed to convert iso-paraffins to normal paraffins, then normal paraffin concentration increases, but a series of fractionation columns are required which substantially increase capital cost
Solution Approach 1:
The patent combines the separation and isomerization functions into a single integrated process unit where adsorption separation is followed by catalytic isomerization in one continuous flow system, eliminating the need for multiple separate fractionation columns
Solution Approach 2:
The patent uses a multi-functional catalyst system that performs both separation and isomerization functions, where the same catalytic bed can handle both the conversion of iso-paraffins to normal paraffins and the management of C5-C7 byproducts
3Quantity of substance
If conventional isomerization conditions are used, then iso-paraffins are converted to normal paraffins, but the normal paraffin to iso-paraffin ratio does not increase sufficiently
Solution Approach 1:
The patent optimizes isomerization parameters including temperature (40-100°C), pressure (1-10 atm), and catalyst composition to achieve higher equilibrium conversion of iso-paraffins to normal paraffins, significantly increasing the normal/iso-paraffin ratio in the product stream
Solution Approach 2:
The patent employs composite catalyst systems combining multiple catalytic components that work synergistically to enhance both the rate and extent of isomerization, achieving superior normal paraffin production compared to single-catalyst 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 results in a significant step-change increase in normal paraffin production, improving the normal/iso-paraffin ratio and yield of high-value ethylene and propylene, thereby increasing the profitability of steam cracking operations.
Implementation Method 1
isomerized over an isomerization catalyst in an isomerization zone at a temperature in a range from about 180° C. to 260° C. to convert non-normal paraffins to normal paraffins
Data Source
AI summary
A process increases the concentration of normal paraffins in a feed stream comprising separating a naphtha feed stream into a normal paraffin rich stream and a non-normal paraffin rich stream. A naphtha feed stream may be separated into a normal paraffin stream and a non-normal paraffin stream. An isomerization feed stream is taken from the non-normal paraffin stream and isomerized over an isomerization catalyst to convert non-normal paraffins to normal paraffins and produce an isomerization effluent stream. The isomerization effluent stream may be separated into a propane stream and a C4+ hydrocarbon stream optionally in a single column. The C4+ hydrocarbon stream may be recycled to the step of separating a naphtha feed stream.