Membrane Separator for Xylene Desorbent Purification

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Commercial simulated moving bed (SMB) systems for separating paraxylene from xylene isomers face inefficiencies due to high non-aromatic content in the desorbent, leading to increased energy consumption and reduced throughput, as existing methods for managing non-aromatic contaminants are inefficient.

Innovation Solution

Implementing a membrane separator to process a desorbent stream, which separates non-aromatics from the desorbent, reducing the need for toluene purge and makeup, thereby improving paraxylene product purity and reducing energy consumption by processing a feed stream and desorbent in an SMB, followed by fractionation and membrane separation to produce a permeate stream lean in non-aromatics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If desorbent purge and make-up is used to manage non-aromatic contaminants, then non-aromatic accumulation is controlled, but energy consumption increases and throughput decreases

Engineering Contradiction:

Improvenon-aromatic contaminant controlVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent extracts non-aromatic contaminants from the desorbent stream using a membrane separator that selectively separates non-aromatics from aromatics. This allows the desorbent to be recycled without purge and make-up, eliminating the energy consumption and throughput reduction associated with traditional contaminant management methods.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the physical-chemical parameters of the separation process by using a membrane separator with specific selectivity for non-aromatics. This enables continuous removal of contaminants at low concentrations, maintaining desorbent purity without the need for energy-intensive purge and make-up operations.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If desorbent purge and make-up is used to manage non-aromatic contaminants, then non-aromatic accumulation is controlled, but system throughput is reduced

Engineering Contradiction:

Improvenon-aromatic contaminant controlVSAvoidsystem throughput

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The membrane separator continuously extracts non-aromatic contaminants from the recycled desorbent stream, allowing near-100% desorbent recycling. This eliminates the throughput reduction caused by purge and make-up operations while maintaining strict control over non-aromatic accumulation in the system.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If membrane separator is added to the SMB system, then non-aromatic removal efficiency increases, but device complexity increases

Engineering Contradiction:

Improvenon-aromatic removal efficiencyVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The membrane separator acts as an intermediary device that integrates into the existing SMB system's desorbent recycle loop. It provides sophisticated non-aromatic removal without requiring fundamental changes to the SMB architecture, balancing enhanced reliability with acceptable complexity through strategic placement in the process flow.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Device complexity

If traditional SMB operation is used, then system simplicity is maintained, but non-aromatic content in desorbent increases over time

Engineering Contradiction:

Improvesystem simplicityVSAvoiddesorbent purity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The membrane separator enables continuous removal of non-aromatic contaminants from the desorbent stream during normal operation. This maintains desorbent purity consistently over time without interrupting the SMB process, whereas traditional methods require periodic purge and make-up operations that break the continuity of useful action.

Inventive Principle:

Principle #20Continuity of useful 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 approach reduces non-aromatic content in the desorbent, increases paraxylene production, decreases the desorbent rate, and lowers energy consumption in distillation towers, enhancing the overall efficiency of the SMB system.

Implementation Method 1

introducing a supply stream comprising at least a portion of one or both of the first desorbent-rich stream, the second desorbent-rich stream, or a combination thereof to a membrane separator to produce a permeate stream and a retentate stream

Methodology Applied

Scientific EffectPermeation: Permeation

Implementation Method 2

adsorption, using an adsorbent solid which preferentially adsorbs paraxylene over metaxylene and orthoxylene in a simulated moving bed (SMB) apparatus

Methodology Applied

Scientific EffectAdsorption: Adsorption

Data Source

PatentUS11673848B2Xylene separation processes using a membrane separator

Publication Date: 2023.06.13 EXXONMOBIL CHEMICAL PATENTS INC

AI summary

A process and system for separating paraxylene from a mixture of paraxylene, metaxylene, orthoxylene, and ethylbenzene in a simulated moving bed apparatus using a membrane to separate non-aromatics from a desorbent stream. The lower nonaromatics content in the desorbent improves paraxylene product purity, increases paraxylene production at the same desorbent rate, reduces the desorbent rate, and/or reduces energy consumption in the product tower.