Liquid-full Reactor Hydroprocessing for LCO Diesel Yield
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Solution Overview
Problem
Current hydroprocessing methods for converting light cycle oil (LCO) to diesel-range products face challenges such as high sulfur and nitrogen content, which results in the production of lower value naphtha and lighter hydrocarbons, and require significant hydrogen usage and catalyst deactivation, failing to meet stringent diesel fuel standards like ultra-low-sulfur-diesel (ULSD).
Innovation Solution
A process involving two-stage hydroprocessing in liquid-full reactors, where LCO is first treated with hydrogen and a diluent to form a liquid feed, then contacted with hydrotreating and hydrocracking catalysts to reduce nitrogen and sulfur content, followed by recycling and separation to produce a high-quality diesel-range product with reduced aromatic content and density, minimizing naphtha production and hydrogen consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional trickle bed hydroprocessing is used to convert LCO to diesel, then sulfur and nitrogen removal is achieved, but significant amounts of light gas and naphtha are produced reducing diesel yield to about 50% or less
Solution Approach 1:
The patent changes the fundamental parameter of hydrogen phase from gas phase (trickle bed) to liquid phase (liquid-full reactor), which fundamentally alters the reaction behavior and product distribution. This parameter change enables selective hydrocracking that produces primarily diesel-range products while minimizing light gas and naphtha formation, achieving diesel yields exceeding 70%.
Solution Approach 2:
The patent introduces a liquid diluent as an intermediary substance that facilitates hydrogen dissolution and transfer to the hydrocarbon feed. This intermediary mechanism enables controlled hydrogenation and hydrocracking reactions that favor diesel product formation while suppressing unwanted light gas and naphtha production pathways.
2Manufacturing precision
If severe hydrocracking conditions are applied to remove nitrogen and sulfur, then purification is improved, but significant amounts of naphtha and lighter hydrocarbons are formed which are lower value products
Solution Approach 1:
The patent modifies the reaction conditions by transitioning to liquid-phase hydrogen transfer, which provides milder and more controlled hydrocracking conditions compared to conventional gas-phase severe hydrocracking. This parameter change enables effective nitrogen and sulfur removal while maintaining product selectivity toward diesel-range hydrocarbons and minimizing formation of lower-value naphtha and lighter products.
3Reliability
If traditional trickle bed reactors are used for hydroprocessing, then hydrogen transfer occurs at catalyst surface, but large quantities of hydrogen must be recycled through expensive hydrogen compressors
Solution Approach 1:
The patent introduces a liquid diluent as an intermediary carrier that dissolves hydrogen and facilitates its transfer to the hydrocarbon feed within the liquid phase. This eliminates the need for complex gas-phase hydrogen compression and recycling systems, simplifying the overall process while maintaining reliable hydrogen availability for the hydroprocessing reactions.
4Manufacturing precision
If conventional hydroprocessing is used to upgrade LCO, then sulfur and nitrogen removal is achieved, but catalyst deactivation occurs due to coke formation
Solution Approach 1:
The patent changes the hydrogen transfer mechanism from gas-phase surface reaction to liquid-phase dissolved hydrogen reaction. This parameter change results in milder reaction conditions that produce less coke on the catalyst surface, thereby reducing catalyst deactivation rates and extending catalyst life while maintaining effective sulfur and nitrogen removal performance.
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 effectively upgrades LCO to a high-quality diesel-range product with reduced sulfur and nitrogen content, achieving a higher yield and meeting stringent diesel fuel standards while minimizing catalyst deactivation and hydrogen usage.
Implementation Method 1
contacting the hydrocarbon feed with hydrogen and a first diluent to form a first liquid feed, wherein hydrogen is dissolved in said first liquid feed
Implementation Method 2
contacting the first liquid feed mixture with a first catalyst in a first liquid-full reaction zone to produce a first effluent
Implementation Method 3
contacting the second liquid feed with a second catalyst in a second liquid-full reaction zone to produce a third effluent
Data Source
AI summary
A process for the hydroprocessing of a low-value light cycle oil (LCO) hydrocarbon feed to provide a high-value diesel-range product. The process comprises a hydrotreatment stage followed by a hydrocracking stage, each of which is conducted under liquid-full reaction conditions wherein substantially all the hydrogen supplied to the hydrotreating and hydrocracking reactions is dissolved in the liquid-phase hydrocarbon feed. Ammonia and optionally other gases formed during hydrotreatment are removed in a separation step prior to hydrocracking. The LCO feed is advantageously converted to diesel in high yield with little loss of hydrocarbon to naphtha.