Selective Hydroprocessing of Cracked Naphtha to Preserve Octane
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Solution Overview
Problem
Current methods for desulfurizing cracked naphtha, such as hydrodesulfurization, often result in significant octane loss due to the hydrogenation of high-octane olefins, which is undesirable for producing low-sulfur gasoline and ultra-low sulfur diesel, as they convert olefins to lower-octane alkanes, reducing the economic value of the product.
Innovation Solution
A method involving two catalytic distillation columns and three stripping columns, with specific catalysts and reaction zones, is used to selectively convert mercaptans to sulfides, hydrogenate diolefins, and perform hydrodesulfurization, minimizing olefin hydrogenation while achieving low sulfur concentrations in naphtha and diesel products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrodesulfurization is used to remove organic sulfur from cracked feedstocks, then sulfur concentration is reduced, but olefin concentration is reduced due to hydrogenation to alkanes
Solution Approach 1:
The process segments the desulfurization operation into two distinct stages: a first catalytic distillation column for selective sulfur removal, and a second catalytic distillation column for further purification. This segmentation allows each stage to be optimized for specific functions, preventing excessive olefin hydrogenation while achieving low sulfur concentrations in the final naphtha product.
Solution Approach 2:
The invention applies local quality by using different catalysts in different zones and columns. The first column uses a catalyst selective for sulfur compound conversion, while the second column uses a different catalyst optimized for further desulfurization. This localized catalytic activity ensures sulfur removal without excessive olefin saturation, preserving octane value in specific product streams.
2Manufacturing precision
If olefins are hydrogenated to alkanes, then sulfur compounds are removed, but octane value is reduced
Solution Approach 1:
The first catalytic distillation column performs preliminary desulfurization by converting mercaptans to sulfides and removing them from the feedstock before the second column processes the material. This preliminary action removes a significant portion of sulfur compounds early in the process, reducing the burden on subsequent hydrodesulfurization steps and minimizing the need for extensive olefin hydrogenation that would reduce octane value.
Solution Approach 2:
The process utilizes parameter changes by operating the two catalytic distillation columns at different temperatures, pressures, and catalyst activities. The first column operates under conditions optimized for mercaptan conversion, while the second column operates under conditions optimized for further sulfur removal. These parameter optimizations enable effective desulfurization while controlling olefin hydrogenation to preserve octane value.
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 effectively produces low-sulfur naphtha and ultra-low sulfur diesel with minimal octane loss, suitable for blending into gasoline and jet fuel, meeting stringent sulfur specifications while preserving high octane values.
Implementation Method 1
a first catalytic distillation column providing for the conversion of mercaptans contained in the cracked feed to sulfides and providing for the selective hydrogenation of diolefins contained in the cracked feed
Implementation Method 2
providing for the selective hydrogenation of diolefins contained in the cracked feed
Implementation Method 3
A second catalytic distillation column providing for the selective hydrodesulfurization of sulfur compounds contained in the heavy bottoms product
Implementation Method 4
catalytic distillation column providing for the conversion... A light overhead product and a heavy bottoms product are yielded from the first catalytic distillation column
Data Source
AI summary
A method providing for the selective hydroprocessing of cracked naphtha feedstock to make blending components for low-sulfur gasoline and either ultra-low sulfur diesel or ultra-low sulfur jet fuel. The method includes the use of two catalytic distillation stages in combination with three stripping columns and two fixed-bed reactors integrated in a novel arrangement so as to provide for the treatment of cracked naphtha feedstock that has a high sulfur concentration to yield exceptionally low-sulfur light cracked naphtha and heavy cracked naphtha products and low-sulfur diesel or jet fuel. The desulfurized light and heavy cracked naphtha are produced with a minimal amount of hydrogenation of the olefin content and may suitably be used as gasoline, jet fuel, and diesel blending components.