Isobutane Recycle Condensing for Stable Fluidized Bed Polymerization

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Solution Overview

Problem

Existing fluidized bed polymerization reactions face challenges with isopentane and heavier hydrocarbon-induced condensing agents, which decrease polymer melting points, leading to stickiness and reactor fouling, limiting temperature regulation and process stability.

Innovation Solution

Employing isobutane as an induced condensing agent in the recycle stream, either alone or in combination with isopentane, to maintain a condensed or super-condensed mode, allowing up to 3.2 times more isobutane by weight before stickiness occurs, enhancing thermal control and catalyst productivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If isopentane and heavier hydrocarbon-induced condensing agents are used, then temperature regulation is improved, but polymer melting point decreases leading to stickiness and reactor fouling

Engineering Contradiction:

Improvetemperature regulationVSAvoidpolymer stickiness and reactor fouling

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameter of the condensing agent from isopentane/heavier hydrocarbons to isobutane. This parameter change maintains the temperature regulation function while eliminating the harmful effect of polymer stickiness, as isobutane does not decrease polymer melting points like isopentane does

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses isobutane, a lighter and more volatile hydrocarbon that can be easily removed from the system. Isobutane serves as a temporary condensing agent that performs its cooling function and then can be readily separated, avoiding the accumulation problems associated with heavier hydrocarbons

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Use of energy by moving object

If isopentane and heavier hydrocarbons are used as condensing agents, then evaporative cooling effectiveness is improved, but catalyst productivity decreases due to stickiness issues

Engineering Contradiction:

Improveevaporative cooling effectivenessVSAvoidcatalyst productivity

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The patent changes the volatility parameter of the condensing agent by selecting isobutane over isopentane. Isobutane's higher volatility enables effective evaporative cooling while its molecular structure does not interact with the polymer to cause stickiness, thus maintaining catalyst productivity

Inventive Principle:

Principle #35Parameter changes

3Temperature

If condensed mode operation is implemented, then thermal control is improved, but process stability decreases due to polymer chunking and sheeting

Engineering Contradiction:

Improvethermal controlVSAvoidprocess stability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent changes the chemical composition parameter of the recycle stream by substituting isobutane for isopentane and heavier hydrocarbons. This change enables condensed mode operation with improved thermal control while maintaining process stability, as isobutane does not cause polymer chunking or sheeting

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Isobutane acts as an intermediary substance in the recycle stream that facilitates heat transfer through condensation and evaporation cycles. It mediates the thermal control function without directly interacting with the polymer to cause instability, unlike isopentane which acts as a harmful intermediary

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Isobutane alleviates melting point decrease and stickiness issues, enabling broader temperature control and increased catalyst productivity, facilitating more effective evaporative cooling and polymerization efficiency.

Implementation Method 1

returning continuously to the reactor a recycle stream comprising an induced condensing agent and the unreacted olefinically unsaturated monomers wherein the recycle stream is returned to the reactor under conditions suitable to form a condensed mode or a super-condensed mode in the recycle stream prior to re-entering the reactor

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 2

the condensed portion of the recycle stream (i.e., a liquid phase admixed with a gas phase) may undergo vaporization upon re-entering the reactor, thereby promoting more effective evaporative cooling than is possible with a circulating gas phase alone

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS12606658B2Isobutane-containing induced condensing agents in fluidized bed polymerization reactions

Publication Date: 2026.04.21 EXXONMOBIL CHEMICAL PATENTS INC

AI summary

Ethylene, alpha olefins, and other olefinically unsaturated monomers may be polymerized under fluidized bed polymerization reaction conditions in the presence of a Ziegler-Natta catalyst. A recycle stream featuring an induced condensing agent (ICA) comprising isobutane may increase catalyst productivity while maintaining quality of the polymer product, particularly when the recycle stream is delivered to a reactor containing the fluidized bed under conditions suitable to form a condensed or super-condensed mode in the recycle stream. The recycle stream may comprise unreacted olefinic monomers, and isobutane or a mixture of isobutane and isopentane.