Gasoline Desulfurization via Intermediate Cut Fractionation
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Solution Overview
Problem
Current methods for producing gasoline with low sulfur content, particularly from catalytic cracking processes, face challenges in maintaining octane number and efficiency due to high hydrogen consumption and the formation of recombinant mercaptans during hydrodesulphurization, which can be costly when mercaptan levels are high.
Innovation Solution
A process involving the fractionation of gasoline to recover an intermediate cut, followed by selective hydrodesulphurization and subsequent fractionation to separate low-sulfur and mercaptan-containing cuts, using specific temperature ranges and hydrodesulphurization conditions to minimize hydrogenation of olefins and separate recombinant mercaptans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional hydrodesulphurization processes are used to reduce sulfur content, then sulfur content is reduced, but octane number drops substantially and hydrogen consumption increases
Solution Approach 1:
The process segments the gasoline fractionation into multiple stages: initial fractionation to separate light ends, selective hydrodesulphurization of the intermediate cut, and final fractionation to separate recombinant mercaptans. This segmentation allows targeted sulfur removal without treating the entire gasoline pool with harsh hydrodesulphurization conditions that would hydrogenate olefins and reduce octane number.
Solution Approach 2:
The process applies local quality by treating only the intermediate gasoline cut (not the entire gasoline pool) with hydrodesulphurization. This intermediate cut contains the sulfur compounds that will form recombinant mercaptans, while the light ends and heavy ends are handled differently. This localized treatment minimizes the volume of material exposed to conditions that cause olefin hydrogenation.
2Quantity of substance
If traditional hydrodesulphurization processes are used to reduce sulfur content, then sulfur content is reduced, but octane number drops substantially
Solution Approach 1:
The process performs preliminary fractionation to remove light ends (C4 and lighter) before hydrodesulphurization. This preliminary action concentrates the sulfur compounds in the intermediate cut, allowing selective treatment. Additionally, the process anticipates the formation of recombinant mercaptans and plans for their subsequent removal through a second fractionation step, thereby protecting the final gasoline product's octane number.
Solution Approach 2:
The process converts the harmful effect of H2S formation during hydrodesulphurization into a manageable byproduct. Instead of allowing H2S to react with olefins and form mercaptans that would require expensive elimination, the process deliberately forms these mercaptans in the intermediate cut, then uses a second fractionation to separate them. This converts an uncontrolled harmful side reaction into a controlled process step with a clear separation and removal strategy.
3Stability of the object's composition
If selective hydrogenation of diolefins is performed before hydrodesulphurization, then diolefins are hydrogenated and light sulphur compounds are made heavier, but process complexity increases
Solution Approach 1:
The process applies partial action by performing selective hydrogenation only on the diolefins in the intermediate cut, not on all olefins. This partial hydrogenation is sufficient to stabilize the composition and prevent gum formation, while avoiding excessive hydrogenation that would reduce octane number. The process then applies partial hydrodesulphurization only to the intermediate cut rather than the entire gasoline pool, further reducing overall process intensity and complexity.
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 produces gasoline with low sulfur and mercaptan content while preserving octane number, reducing hydrogen consumption, and avoiding costly mercaptan elimination methods.
Implementation Method 1
a) fractionating the gasoline in a manner such as to recover at least one intermediate gasoline cut, MCN
Implementation Method 2
desulphurizing the intermediate gasoline cut MCN alone and in the presence of a hydrodesulphurization catalyst and hydrogen
Implementation Method 3
in the presence of a hydrodesulphurization catalyst
Implementation Method 4
c) fractionating, in a splitter, the partially desulphurized intermediate gasoline cut MCN which has not undergone catalytic treatment subsequent to step b)
Data Source
AI summary
A process for the treatment of a gasoline containing sulphur-containing compounds, olefins and diolefins, comprising the following steps:a) fractionating the gasoline in a manner such as to recover at least one intermediate gasoline cut, MCN, comprising hydrocarbons and wherein the temperature difference (ΔT) between the 5% and 95% by weight distillation points is less than 60° C.;b) desulphurizing the intermediate gasoline cut MCN alone and in the presence of a hydrodesulphurization catalyst and hydrogen in a manner such as to produce a partially desulphurized intermediate gasoline cut MCN; andc) fractionating, in a splitter, the at least partially desulphurized intermediate gasoline cut MCN which has not undergone catalytic treatment subsequent to step b), in a manner such as to recover an intermediate gasoline with low sulphur and mercaptans contents from the column head and a cut of hydrocarbons containing sulphur-containing compounds including mercaptans from the column bottom.