Rectification Column for Unsaturated Anhydride Production

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Solution Overview

Problem

Existing processes for preparing unsaturated carboxylic anhydrides face challenges such as incomplete conversion due to stoichiometric excess of reactants, contamination by catalysts, formation of by-products, and polymerization issues, which hinder high-purity product attainment and efficient space-time yield.

Innovation Solution

A continuous process utilizing a rectification column with distinct regions, where reactants are fed in stoichiometric ratios, unconverted reactants are recycled, and products are drawn off between the middle and lower regions, employing an inert boiling oil to prevent polymerization and achieve complete conversion and high purity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If stoichiometric excess of acetic anhydride is used to achieve complete conversion, then conversion completeness is improved, but product purity deteriorates due to mixture formation and catalyst contamination

Engineering Contradiction:

Improveconversion completenessVSAvoidproduct purity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The rectification column is divided into distinct regions (upper, middle, lower) with different functions: the upper region removes acetic acid, the middle region handles the reaction, and the lower region draws off the product. This segmentation allows stoichiometric excess reactants to be used for complete conversion while maintaining product purity through spatial separation of purification functions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An inert boiling oil is introduced as an intermediary substance in the lower column region to prevent polymerization of the unsaturated anhydride product. This mediator allows the product to be drawn off in high purity without catalyst contamination or polymerization, resolving the contradiction between complete conversion and product purity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If reactants are kept in the column for long residence times to ensure complete reaction, then conversion is improved, but polymerization increases

Engineering Contradiction:

Improveconversion completenessVSAvoidpolymerization

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The product is extracted and drawn off from the lower column region as soon as it is formed, minimizing its residence time in the reactive environment. This rapid extraction prevents polymerization while the continuous circulation ensures complete conversion of reactants.

Inventive Principle:

Principle #2Taking out (Extraction)

3Loss of substance

If stoichiometric ratios are used to avoid excess reactant, then material efficiency is improved, but conversion completeness deteriorates

Engineering Contradiction:

Improvereactant utilization efficiencyVSAvoidconversion completeness

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

Unreacted starting materials are continuously circulated back into the reaction zone from the lower column region, creating a feedback loop that ensures complete conversion. This allows stoichiometric ratios to be used initially while still achieving complete conversion through the feedback mechanism of continuous recycling.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The continuous circulation and recycling of unreacted materials maintains continuous reaction action, ensuring that all reactants are eventually converted to product. This continuous process eliminates the need for stoichiometric excess while achieving complete conversion.

Inventive Principle:

Principle #20Continuity of useful action

4Productivity

If continuous process is used to increase productivity, then space-time yield is improved, but process complexity increases

Engineering Contradiction:

Improvespace-time yieldVSAvoidprocess structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The rectification column performs multiple functions simultaneously: it serves as the reaction vessel, the separation column, and the circulation system. This multi-functionality increases productivity through continuous operation while avoiding the need for separate reactors, separators, and recycling systems that would increase device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8084640B2Method for the continuous production of unsaturated carboxylic acid anhydrides

Publication Date: 2011.12.27 EVONIK OPERATIONS GMBH

AI summary

Process for continuously preparing unsaturated carboxylic anhydrides of the general formula IR—C(O)—O—C(O)—R (I)in which R is an unsaturated organic radical having 2 to 12 carbon atomsby transanhydridization of an aliphatic carboxylic anhydride with a carboxylic acid of the general formula IIR—COOH (II)in which R is as defined abovein a rectification column having an upper, middle and lower region, characterized in thatf) an inert boiling oil is initially charged in the bottom of the column,g) the reactants are fed into a reaction region in stoichiometric ratios,h) the carboxylic acid formed as the by-product is withdrawn at the top of the column,i) the unconverted reactants are recycled into the reaction region andj) the product of the formula I is obtained via a side draw, preferably between the middle and lower column region.