Simulated Moving Bed Adsorptive Separation for Normal Paraffin Purification

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Solution Overview

Problem

The high cost and complexity of separating normal paraffins from broad boiling point range naphtha hydrocarbon fractions in steam cracking processes, due to the need for costly equipment and utilities in traditional desorbent separation methods, and the inefficiency of using desorbents with boiling points close to the process components.

Innovation Solution

A simulated moving bed adsorptive separation process using a hydrocarbon desorbent with 12 carbon atoms, operating at an A/Fn ratio of 0.90 to 0.92, which selectively retains normal paraffins and allows for their efficient recovery, reducing the amount of adsorbent required and lowering operational costs by simplifying the separation of desorbent from process components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional fractional distillation is used to separate normal paraffins from naphtha, then separation can be achieved, but the process becomes expensive and complicated requiring costly equipment and utilities

Engineering Contradiction:

Improveseparation purityVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical fractional distillation system with an adsorptive separation system using molecular sieves. The molecular sieves selectively adsorb normal paraffins based on their linear molecular structure, eliminating the need for complex distillation columns and associated utilities while achieving high separation purity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs molecular sieves with specific pore sizes that selectively accommodate linear normal paraffin molecules while excluding branched paraffins and aromatic hydrocarbons. This porous material approach enables selective separation based on molecular geometry rather than volatility differences, simplifying the overall separation process.

Inventive Principle:

Principle #31Porous materials

2Ease of manufacture

If desorbent with boiling point close to process components is used, then separation can be performed, but more costly equipment and utilities are required

Engineering Contradiction:

Improveseparation feasibilityVSAvoidequipment cost

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent changes the boiling point parameter of the desorbent to be significantly different from the process components. By selecting a desorbent with a boiling point well above the naphtha fraction, the separation becomes much easier, allowing for simpler equipment design and reduced utility requirements while maintaining effective desorption capability.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If standard A/Fn ratio is used in SMB process, then normal operation is maintained, but more adsorbent is required increasing operational costs

Engineering Contradiction:

Improveprocess stabilityVSAvoidadsorbent amount

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent optimizes the A/Fn ratio parameter to values below 1.0 (specifically 0.8-1.2), which is lower than conventional SMB operations. This parameter change reduces the amount of adsorbent required in the system while maintaining stable operation and effective separation, thereby reducing both capital and operational costs.

Inventive Principle:

Principle #35Parameter changes

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 significantly reduces capital and operational costs by minimizing adsorbent usage, simplifying the separation process, and enhancing the production of high-purity normal paraffins suitable for steam cracking, while also producing a desirable catalytic reforming feedstock.

Implementation Method 1

passing a feed stream comprising C5 to C9 hydrocarbons including C5 to C9 normal paraffins into an adsorption zone of a simulated moving bed adsorptive separation zone operating at an A/Fn ratio of from 0.90 to about 0.92 and selectively retaining normal paraffins on an adsorbent located in the adsorption zone

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

passing a hydrocarbon desorbent having 12 carbon atoms into a desorption zone in the adsorptive separation zone as at least part of a desorbent stream and removing normal paraffins from adsorbent present in the desorption zone to yield an extract stream comprising C5 to C9 normal paraffins and desorbent

Methodology Applied

Scientific EffectDesorption: Desorption

Data Source

PatentUS8283511B2Ethylene production by steam cracking of normal paraffins

Publication Date: 2012.10.09 UOP LLC

AI summary

A simulated moving bed adsorptive separation process for preparing the separate feed streams charged to naphtha reforming unit and a steam cracking unit has been developed. The feed stream to the overall unit is passed into the adsorptive separation unit. The desorbent in the adsorptive separation is C12 hydrocarbons. The simulated moving bed adsorptive separation separates the components of the feed stream into a normal paraffin stream, which is charged to the steam cracking process, and non-normal hydrocarbons which are passed into a reforming zone. The desorbent is readily separated from the normal paraffin stream and from the non-normal paraffin stream and the simulated moving bed adsorption zone is operated at an A/Fn ratio of from about 0.90 to about 0.92.