Fischer-Tropsch Base Oil Yield via Fractional Hydroisomerization

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Solution Overview

Problem

Existing processes for producing base oils from Fischer-Tropsch synthesis products have limitations in yield, particularly for oils with kinematic viscosity at 100° C. between 2 and 8 cSt, as they convert potential base oil molecules to middle distillate molecules and recycle heavy fractions, reducing base oil yield.

Innovation Solution

A process involving the separation of Fischer-Tropsch synthesis products into middle distillate, heavy ends, and intermediate base oil precursor fractions, followed by selective isomerization and dewaxing of these fractions to minimize conversion to middle distillates and maximize base oil yield, using catalysts like ZSM-12 and platinum-based systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the Fischer-Tropsch synthesis product is subjected to hydrocracking/hydroisomerizing step followed by dewaxing, then excellent quality base oils are obtained, but the yield of base oils relative to the Fischer-Tropsch synthesis product is reduced

Engineering Contradiction:

Improvequality of base oilVSAvoidyield of base oil

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The process segments the Fischer-Tropsch synthesis product into three distinct fractions based on boiling range: middle distillate fraction (boiling below 370°C), base oil precursor fraction (boiling between 370-540°C), and heavy ends fraction (boiling above 540°C). This segmentation allows each fraction to be processed differently, with the base oil precursor fraction being directly dewaxed to maximize yield while the other fractions undergo different treatments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of the conventional approach where the entire Fischer-Tropsch product is subjected to hydrocracking/hydroisomerization followed by dewaxing, the invention inverts the sequence by first separating the product into fractions and then selectively dewaxing only the base oil precursor fraction. This avoids the conversion of potential base oil molecules to middle distillate molecules that occurs in the conventional approach.

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If heavy fraction is recycled to hydrocracking/hydroisomerizing step, then conversion is improved, but more potential base oil molecules are converted to middle distillate molecules

Engineering Contradiction:

Improveconversion efficiencyVSAvoidamount of base oil molecules

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The invention extracts the base oil precursor fraction (boiling between 370-540°C) from the hydrocracking/hydroisomerization process before it can be further converted to middle distillate molecules. By taking out this fraction at the appropriate stage and directing it to dewaxing, the process preserves the quantity of base oil molecules that would otherwise be converted to unwanted middle distillates.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The process performs preliminary separation of the Fischer-Tropsch synthesis product into distinct boiling range fractions before the hydrocracking/hydroisomerization step. This preliminary action allows the base oil precursor fraction to be identified and protected from excessive conversion to middle distillates during subsequent processing.

Inventive Principle:

Principle #10Preliminary action

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 enhances the yield of base oils relative to the Fischer-Tropsch synthesis product, achieving higher viscosity grades with reduced gaseous by-products and increased gas oil production, while maintaining low pour points and volatility requirements.

Implementation Method 1

subjecting the base oil precursor fraction (ii) to a catalytic hydroisomerisation and catalytic dewaxing process

Methodology Applied

Scientific EffectHydroisomerisation: Catalysis

Implementation Method 2

subjecting the base oil precursor fraction (ii) to a catalytic hydroisomerisation and catalytic dewaxing process to yield one or more base oil grades

Methodology Applied

Scientific EffectCatalytic dewaxing: Catalysis

Implementation Method 3

separating the Fischer-Tropsch synthesis product into a fraction (i) boiling in the middle distillate range and below, a heavy ends fraction (iii) and an intermediate base oil precursor fraction (ii)

Methodology Applied

Scientific EffectDistillation: Distillation

Data Source

PatentUS7727376B2Process to prepare base oil from a Fisher-Tropsch synthesis product

Publication Date: 2010.06.01 SHELL USA INC

AI summary

A process to prepare base oils from a Fischer-Tropsch synthesis product by(a) separating the Fischer-Tropsch synthesis product into a fraction (i) boiling in the middle distillate range and below, a heavy ends fraction (iii) and an intermediate base oil precursor fraction (ii) boiling between fraction (i) and fraction (iii),(b) subjecting the base oil precursor fraction (ii) to a catalytic hydroisomerisation and catalytic dewaxing process to yield one or more base oil grades,(c) subjecting the heavy ends fraction (iii) to a conversion step to yield a fraction (iv) boiling below the heavy ends fraction (iii) and(d) subjecting the high boiling fraction (v) of fraction (iv) to a catalytic hydroisomerisation and catalytic dewaxing process to yield one or more base oil grades.