Two-Stage Light Olefin Upgrading for Diesel Yield
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Solution Overview
Problem
Current commercial processes for upgrading light paraffins to liquid transportation fuels are inefficient and costly, requiring separation of ethane prior to upgrading and having high capital expenses, making them unattractive for converting a mixture of C2-C7 light olefins into usable fuel.
Innovation Solution
A two-stage conversion process using a zeolite catalyst in a system that cracks and quenches light hydrocarbon feedstocks, optimizing temperature and pressure conditions in each stage to produce a higher yield of diesel-range hydrocarbons, allowing for the efficient conversion of a mixture of C2-C7 light olefins into liquid transportation fuels without initial separation of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional one-stage processes are used to upgrade light olefins, then the process is simpler, but the yield of liquid transportation fuels and diesel-range hydrocarbons is lower
Solution Approach 1:
The upgrading process is divided into two distinct stages: a first stage operating at lower temperature (450-650°C) to produce diesel-range hydrocarbons (C10-C20), and a second stage operating at higher temperature (650-850°C) to convert remaining light olefins to gasoline-range hydrocarbons (C5-C10). This segmentation allows each stage to be optimized for specific product ranges, thereby increasing overall liquid fuel yield while maintaining manageable process complexity through systematic division of functions.
2Adaptability or versatility
If commercial upgrading options like Oleflex or START are used, then propane and heavier paraffins can be upgraded, but ethane must be removed prior to upgrading which increases process complexity and capital expense
Solution Approach 1:
The two-stage process is designed to handle a universal feedstock range of C2-C7 light olefins including ethane, propane, butanes, and natural gasoline without requiring pre-separation. The first stage converts heavier components to diesel-range products while the second stage converts lighter components including ethane to gasoline-range products. This multi-functional capability eliminates the need for ethane removal units and associated complex separation infrastructure, reducing capital expense while maintaining versatility across the entire NGL spectrum.
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
The process maintains or increases overall yield of liquid transportation fuels, particularly diesel-range hydrocarbons, while improving the yield of hydrocarbons in the diesel boiling-point range, making it more efficient and cost-effective compared to conventional single-stage processes.
Implementation Method 1
cracking and quenching the light hydrocarbon feedstock to produce a raw cracked olefins stream
Implementation Method 2
cracking and quenching the light hydrocarbon feedstock
Implementation Method 3
contacting the raw cracked olefins stream with a first stage catalyst, where the catalyst, temperature and pressure in the first stage conversion reactor are configured to produce a first stage effluent comprising at least 10 wt % of hydrocarbons that are characterized by a boiling point ranging from 193°C. to 360°C. at 1 atm.
Implementation Method 4
converting the uncondensed gas-phase hydrocarbons in a second stage reactor at a second temperature that is at least 20°C. higher than the first temperature, to produce a second stage effluent
Implementation Method 5
separating the first stage effluent in a first separator to produce a first condensed liquid hydrocarbons comprising at least five carbon atoms, and an unconverted light olefin stream comprising four or less carbon atoms
Data Source
AI summary
The present disclosure relates generally processes and systems for converting a mixture of light hydrocarbons to liquid transportation fuels by first cracking the light hydrocarbons to an intermediate comprising olefins, which is converted by contacting with a catalyst comprising at least one zeolite in two separate conversion stages with an intervening recovery of liquid product. The first stage conversion favors oligomerization of larger olefins to form diesel range products that are collected prior to directing unconverted smaller olefins to be oligomerized in a second stage conversion conducted at a higher temperature and lower pressure.