Dealkylation-Transalkylation Process for Xylenes Production

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Solution Overview

Problem

Petrochemical refiners face challenges in utilizing heavy reformate streams due to environmental regulations limiting C6+ aromatics in gasoline fuel, and existing methods are inefficient in converting C9+ alkyl aromatic compounds into valuable products like mixed xylenes, leading to waste of processing energy and increased capital expenditure.

Innovation Solution

A dealkylation-transalkylation system that uses a hydrodealkylation catalyst to convert methyl ethyl benzenes into toluene and ethane, followed by a transalkylation stage with a separate catalyst to convert tri-methyl benzenes into mixed xylenes, optimizing the production of p-xylene and other valuable chemicals from heavy reformate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If heavy reformate is processed using conventional single-stage transalkylation, then xylenes production is achieved, but processing energy is wasted and capital expenditure increases

Engineering Contradiction:

Improvexylenes production efficiencyVSAvoidprocessing energy consumption

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The process is divided into two distinct stages: dealkylation stage followed by transalkylation stage. The dealkylation stage converts heavy reformate (C9+ aromatics) into lighter aromatics (toluene, C8 aromatics), while the transalkylation stage converts these lighter aromatics into xylenes. This segmentation allows each stage to be optimized for its specific function, improving overall energy efficiency and avoiding the energy waste associated with conventional single-stage processes.

Inventive Principle:

Principle #1Segmentation

2Productivity

If heavy reformate is processed using conventional single-stage transalkylation, then xylenes production is achieved, but capital expenditure increases

Engineering Contradiction:

Improvexylenes production efficiencyVSAvoidprocessing system complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

3Ease of operation

If toluene is added back into heavy reformate stream, then transalkylation can proceed, but processing energy is wasted and capital expenditure increases

Engineering Contradiction:

Improvetransalkylation process feasibilityVSAvoidprocessing energy consumption

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The dealkylation stage serves the transalkylation stage by producing toluene and C8 aromatics in situ from the heavy reformate feed. This eliminates the need to add external toluene to the transalkylation stage, thereby avoiding the energy consumption and capital expenditure associated with toluene recovery and re-injection operations. The system is self-sufficient, generating its own required feedstock for the second stage.

Inventive Principle:

Principle #25Self-service

4Reliability

If C6+ aromatics are used in gasoline fuel, then octane rating is improved, but environmental regulations are violated

Engineering Contradiction:

Improvefuel qualityVSAvoidenvironmental compliance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The process changes the molecular weight parameters of the aromatic compounds. It converts heavy reformate (C9+ aromatics) into lighter aromatic products (C7-C8 xylenes, toluene) through dealkylation and transalkylation reactions. The resulting xylenes can be used as high-octane fuel additives that meet environmental specifications, thus maintaining fuel quality while achieving environmental compliance.

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 method maximizes the yield of mixed xylenes from low-value heavy reformates, reduces the need for prior-processed BTEX chemicals, and improves the economics of petrochemical processing by generating valuable chemicals like toluene and xylenes, while minimizing energy consumption and capital expenditure.

Implementation Method 1

The dealkylation stage contains a hydrodealkylation catalyst. The hydrodealkylation catalyst is operable to selectively convert methyl ethyl benzenes and hydrogen into toluene and a non-aromatic product gas.

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

The transalkylation stage contains a transalkylation catalyst. The transalkylation catalyst is operable to selectively convert tri-methyl benzenes and toluene into mixed xylenes.

Methodology Applied

Scientific EffectCatalysis: Catalysis

Data Source

PatentEP2838870B1Combined heavy reformate dealkylation-transalkylation process for maximizing xylenes production

Publication Date: 2019.10.30 SAUDI ARABIAN OIL CO

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AI summary

A method of forming mixed xylenes from a heavy reformate using a dealkylation- transalkylation system includes the step of introducing both a heavy reformate containing methyl ethyl benzenes and tri-methyl benzenes and that is sufficiently free of toluene and a hydrogen-containing material into the dealkylation stage such that the heavy reformate and the hydrogen -containing material intermingle and contact the hydrodealkylation catalyst. The dealkylation-transalkylation system includes dealkylation, non-aromatic product gas separations and transalkylation stages. Toluene forms from the reaction of methyl ethyl benzenes and hydrogen in the presence of the hydrodealkylation catalyst. The method also includes the step of introducing a dealkylated heavy reformate into the transalkylation stage such that the dealkylated. heavy reformate contacts a transalkylation catalyst, forming a transalkylation stage product mixture includes mixed xylenes.