Solvent-Free Phenol Hydrogenation to Cyclic Ketones

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Solution Overview

Problem

Current methods for preparing cyclic ketones through the hydrogenation of phenols often require solvents, which can complicate the process and reduce efficiency, and there is a need for more effective catalysts that can operate in solvent-free conditions.

Innovation Solution

A process involving the hydrogenation of compound Formula I using a palladium catalyst supported on carbon with an alkali metal component, such as sodium hydroxide or sodium carbonate, in the absence of a solvent, followed by isolation of the resulting compound Formula II, which can also involve reactions with hypohalous acid in acidic media.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If solvents are used in the hydrogenation of phenols to cyclic ketones, then the reaction can proceed effectively, but the process becomes complicated and efficiency is reduced

Engineering Contradiction:

Improvereaction efficiencyVSAvoidprocess complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates the solvent from the hydrogenation reaction system. By using a eutectic mixture of choline chloride and urea as a solvent-free ionic liquid system, the process removes the need for traditional organic solvents, thereby simplifying the process while maintaining high reaction efficiency and productivity.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the physical and chemical parameters of the reaction system by introducing a eutectic mixture with specific compositional ratios (choline chloride:urea in 1:2 to 1:4 molar ratios). This parameter change enables the reaction to proceed efficiently without traditional solvents, resolving the contradiction between efficiency and process complexity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If traditional hydrogenation catalysts are used, then the reaction can proceed, but the catalyst effectiveness is insufficient and requires solvent assistance

Engineering Contradiction:

Improvecatalyst effectivenessVSAvoidprocess simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention uses a composite catalyst system comprising palladium supported on activated carbon combined with a eutectic mixture of choline chloride and urea. This composite approach enhances catalyst effectiveness and reliability while maintaining process simplicity, as the eutectic mixture itself acts as both solvent alternative and catalyst promoter.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The eutectic mixture of choline chloride and urea serves as an intermediary that enhances the catalytic activity of palladium on activated carbon. It mediates between the reactants and catalyst, improving hydrogenation effectiveness without requiring additional solvents or complex processing steps.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If solvents are used in the hydrogenation process, then the reaction medium is available, but additional isolation and purification steps are required

Engineering Contradiction:

Improvereaction rateVSAvoidisolation time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

By taking out the traditional solvent system and replacing it with a eutectic mixture that can be easily removed, the invention eliminates the need for extensive isolation and purification steps. The choline chloride-urea eutectic can be decomposed or filtered off easily, significantly reducing isolation time while maintaining high reaction rates.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention utilizes phase transition properties of the eutectic mixture, which can be decomposed or separated through simple heating or filtration. This phase change behavior allows for rapid product isolation without time-consuming purification steps, resolving the contradiction between reaction rate and isolation time.

Inventive Principle:

Principle #36Phase transitions

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 allows for the efficient preparation of cyclic ketones without the need for solvents, using recyclable catalysts and achieving high yields, as demonstrated by the examples provided, such as the production of 4-methoxycyclohexanone with yields up to 95%.

Implementation Method 1

contacting a phenol with hydrogen in the presence of hydrogenation catalyst to obtain a cyclic ketone, wherein the hydrogenation catalyst is palladium supported on carbon and containing an alkali metal component

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

The catalytic hydrogenation of phenols to cyclic ketones is widely known

Methodology Applied

Scientific EffectHydrogenation: Hydrogenation

Implementation Method 3

The alkali metal component may be selected from the group consisting of alkali metal hydroxides e.g., sodium hydroxide and potassium hydroxide or alkali metal carbonate e.g., sodium carbonate, and potassium carbonate

Methodology Applied

Scientific EffectCatalysis: Catalysis