Liquid-full Hydrotreating for LCO Diesel Yield
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Solution Overview
Problem
Conventional hydroprocessing methods for upgrading light cycle oil (LCO) to diesel fuel face challenges such as high hydrogen consumption, catalyst deactivation, and significant production of lower-value naphtha and lighter hydrocarbons, due to high nitrogen and sulfur content, and require complex gas separation processes, which are inefficient and costly.
Innovation Solution
A liquid-full process involving a two-stage hydroprocessing system where LCO is contacted with a diluent and hydrogen to create a liquid feed, then treated with a hydrotreating catalyst followed by a zeolite or amorphous ring-opening catalyst, with hydrogen recycling to minimize gas phase presence and maximize diesel production, achieving high yield and quality diesel with reduced sulfur and nitrogen content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional three-phase hydroprocessing units (trickle bed reactors) are used for hydrotreating and hydrocracking, then sulfur and nitrogen can be removed from hydrocarbon feeds, but large quantities of hydrogen are required and significant coke formation occurs on the catalyst surface leading to catalyst deactivation
Solution Approach 1:
The patent changes the phase state parameter of hydrogen from gas phase to dissolved liquid phase by saturating the hydrocarbon feed with hydrogen under pressure. This parameter change eliminates the need for large quantities of gaseous hydrogen while preventing catalyst deactivation, as the dissolved hydrogen is delivered directly to the catalyst surface without forming coke-prone gas-liquid interfaces.
Solution Approach 2:
The patent utilizes the phase transition of hydrogen from gas to dissolved state by pressurizing and saturating the liquid hydrocarbon feed with hydrogen. This phase transition allows hydrogen to be transported in the liquid phase and delivered to the catalyst surface without forming the gas-liquid interfaces that lead to coke formation in conventional trickle bed reactors.
2Quantity of substance
If hydrocracking is performed to crack heavy hydrocarbons into lighter products, then lower density products are produced, but significant amounts of naphtha and lighter hydrocarbons are produced which are considered lower value products
Solution Approach 1:
The patent applies local quality by using different catalysts with specific functions in different zones: a hydrotreating catalyst for sulfur and nitrogen removal, and a selective ring opening catalyst for converting polyaromatics to diesel-range hydrocarbons. This localized catalytic action ensures high diesel yield with minimal naphtha production, as each catalyst performs its specific function optimally.
Solution Approach 2:
The patent segments the hydroprocessing function into two distinct catalytic stages: hydrotreating followed by selective ring opening. This segmentation allows each catalyst to be optimized for its specific function, with the selective ring opening catalyst specifically targeting polyaromatic conversion to diesel-range products while minimizing excessive cracking to naphtha.
3Reliability
If traditional trickle bed reactors are used for LCO upgrading, then sulfur and nitrogen can be removed, but large process equipment such as large gas compressors are required and significant amounts of light gas and naphtha are produced
Solution Approach 1:
The patent extracts the gas phase hydrogen from the system by using dissolved liquid-phase hydrogen. This eliminates the need for large gas compressors and gas handling equipment, simplifying the process while maintaining hydrotreating effectiveness. The hydrogen is introduced as a liquid under pressure and remains dissolved throughout the process.
Solution Approach 2:
The patent uses the liquid hydrocarbon feed itself as an intermediary medium to transport hydrogen to the catalyst. Instead of using gaseous hydrogen that requires compression and gas-liquid contact equipment, the hydrogen is dissolved in the liquid feed, which then delivers the hydrogen directly to the catalyst surface, eliminating the need for complex gas handling equipment.
4Reliability
If hydrogen is added well above the hydrogen saturation limit of the liquid in conventional processes, then hydrogen is available as the liquid is consumed, but hydrogen gas is lost from the reactor effluent which may be significant
Solution Approach 1:
The patent implements feedback by recycling the liquid product effluent back to the reactor inlet. This creates a closed loop where any unreacted dissolved hydrogen in the product stream is recovered and reused, eliminating hydrogen loss. The recycle stream maintains hydrogen saturation while preventing gas phase hydrogen escape.
Solution Approach 2:
The patent maintains continuous hydrogen availability through the recycle stream, which keeps the liquid phase saturated with hydrogen throughout the process. This continuous circulation ensures hydrogen is always available at the catalyst surface without requiring excess hydrogen that would otherwise be lost as gas in the effluent.
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 effectively converts LCO to high-quality diesel with reduced density and increased cetane index, minimizing naphtha production and maintaining hydrogen efficiency, thus overcoming the limitations of traditional methods by eliminating the need for gas separation and reducing hydrogen consumption.
Implementation Method 1
contacting the hydrocarbon feed with (i) a diluent and (ii) hydrogen, to produce a feed/diluent/hydrogen mixture, wherein the hydrogen is dissolved in the mixture to provide a liquid feed
Implementation Method 2
contacting the feed/diluent/hydrogen mixture with a first catalyst in a first liquid-full reaction zone, to produce a first product effluent
Implementation Method 3
Hydroprocessing, such as hydrodesulfurization and hydrodenitrogenation, have been used to remove sulfur and nitrogen, respectively from hydrocarbon feeds
Implementation Method 4
Hydroprocessing, such as hydrodesulfurization and hydrodenitrogenation, have been used to remove sulfur and nitrogen, respectively from hydrocarbon feeds
Implementation Method 5
contacting the first product effluent with a second catalyst in a second liquid-full reaction zone, to produce a second product effluent
Implementation Method 6
An alternative hydroprocessing operation is hydrocracking, which has been used to crack heavy hydrocarbons (high density) into lighter products (lower density) with hydrogen addition
Implementation Method 7
hydrocracking, which has been used to crack heavy hydrocarbons (high density) into lighter products (lower density) with hydrogen addition
Data Source
AI summary
This disclosure relates to liquid-full processes for hydroprocessing a light cycle oil (LCO). The processes involve hydrotreatment followed by selective ring opening in the presence of hydrotreating catalyst and selective ring opening catalyst respectively. The selective ring opening catalyst can be either zeolite ring opening catalyst or amorphous ring opening catalyst. In aspects of zeolite ring opening catalyst, the volume ratio of the total amount of the zeolite ring opening catalyst to the total amount of the hydrotreating catalyst is from about 0.2 to about 1.5. In aspects of amorphous ring opening catalyst, the volume ratio of the total amount of the amorphous ring opening catalyst to the total amount of the hydrotreating catalyst is from about 0.2 to about 3.