Selective Hydrotreating via Aromatic Fractionation
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Solution Overview
Problem
Existing hydrotreating processes struggle to efficiently reduce sulfur content in hydrocarbon fuels to ultra-low levels, particularly in existing facilities designed for milder conditions, due to the difficulty in desulfurizing refractory sulfur-containing aromatic compounds, which are costly to remove and require significant capital investments for upgrading.
Innovation Solution
A method involving the separation of hydrocarbon feeds into aromatic-lean and aromatic-rich fractions, with the aromatic-lean fraction treated under mild conditions and the aromatic-rich fraction under severe conditions, using specific hydrotreating zones and catalysts to effectively reduce sulfur content, thereby achieving ultra-low sulfur levels in hydrocarbon fuels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If existing facilities operating at mild conditions are used for hydrotreating, then operational simplicity is maintained, but sulfur content cannot be reduced to ultra-low levels below 15 ppmw
Solution Approach 1:
The hydrotreating process is divided into two separate stages: a first hydrotreating stage operating at mild conditions to remove easily desulfurized sulfur compounds, and a second hydrotreating stage operating at severe conditions to remove refractory sulfur compounds. This segmentation allows each stage to be optimized for its specific function, maintaining operational simplicity while achieving ultra-low sulfur content below 15 ppmw.
2Manufacturing precision
If severe hydrotreating conditions are applied to remove refractory sulfur compounds, then sulfur content is reduced to ultra-low levels, but capital investment and operational costs increase significantly
Solution Approach 1:
The first hydrotreating stage is performed as a preliminary action under mild conditions to remove the majority of sulfur compounds (including aliphatic sulfur compounds and some aromatic sulfur compounds) before the second stage. This preliminary removal reduces the burden on the second stage, allowing it to operate more efficiently and reducing the overall capital investment and operational costs required to achieve ultra-low sulfur content.
3Manufacturing precision
If severe hydrotreating conditions are used to treat all sulfur compounds, then complete desulfurization is achieved, but hydrogen consumption increases
Solution Approach 1:
The process applies partial severe action only to the aromatic-rich fraction in the second hydrotreating stage, rather than subjecting the entire feedstock to severe conditions. The first stage handles the bulk of sulfur removal under mild conditions, and the second stage applies severe conditions selectively to the remaining refractory compounds in the aromatic fraction, thereby achieving complete desulfurization while minimizing overall hydrogen consumption.
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 approach allows for efficient and cost-effective desulfurization of hydrocarbon fuels by targeting different classes of sulfur-containing compounds, reducing the need for extensive facility upgrades and minimizing hydrogen consumption, while achieving sulfur levels below 15 ppmw, even in existing facilities.
Implementation Method 1
hydrotreating processes to efficiently reduce the sulfur content of hydrocarbons
Implementation Method 2
utilization of more active catalyst compositions
Data Source
AI summary
A selective mid-distillate hydrotreating process is provided for production of hydrocarbon fuels with an ultra-low level of sulfur in which the initial hydrocarbon feedstock is introduced into to an aromatic extraction zone to produce an aromatic-lean fraction and an aromatic-rich fraction, which contain different classes of organosulfur compounds having different reactivities when subjected to hydrotreating reactions. The aromatic-lean fraction contains primarily labile heteroatom-containing compounds, and is passed to a first hydrotreating zone operating under mild conditions to remove the sulfur heteroatom from organosulfur hydrocarbon compounds. The aromatic-rich fraction contains primarily refractory heteroatom-containing compounds, including aromatic molecules such as certain benzothiophenes (e.g., long chain alkylated benzothiophenes), dibenzothiophene and alkyl derivatives, such as sterically hindered 4,6-dimethyldibenzothiophene, and is passed to a hydrotreating zone operating under relatively severe conditions to remove the heteroatom from sterically hindered refractory compounds.