Palladium Catalyst Removal in Hydrocarbon Distillation
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Solution Overview
Problem
Distillative purification methods for producing aryl-, heteroaryl-, or alkenyl-substituted unsaturated hydrocarbons in large-scale industrial production often result in reduced yields due to decomposition of the coupling reaction products when heated for extended periods with residual palladium catalysts or its decomposition products.
Innovation Solution
Incorporating a compound with at least one NC=S group, such as dithiocarbamates or thioureas, during distillative purification to inhibit product decomposition and maintain high yields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If distillative purification is performed on large scale for industrial production, then productivity is improved, but yield of aryl-, heteroaryl- or alkenyl-substituted unsaturated hydrocarbons is reduced due to decomposition
Solution Approach 1:
A compound having at least one NC=S group (dithiocarbamate or thiourea) is introduced as an intermediary substance during distillative purification. This intermediary forms solvent-insoluble palladium complexes with residual catalysts, preventing product decomposition while allowing efficient distillation and purification of the coupling reaction product at industrial scale.
Solution Approach 2:
The harmful effect of residual palladium catalyst decomposition is converted into a beneficial effect. The NC=S group-containing compound reacts with residual palladium to form insoluble complexes, transforming the problematic catalyst residue into an inactive precipitate that can be removed, thereby protecting the product from decomposition during large-scale distillation.
2Manufacturing precision
If distillation is performed with residual palladium catalyst present, then purification is achieved, but product decomposition occurs due to extended heating
Solution Approach 1:
The NC=S group-containing compound is added to the reaction mixture before distillation begins. This preliminary action ensures that any residual palladium catalyst is already complexed and deactivated before the distillation process starts, preventing product decomposition during the heating phase while maintaining effective purification.
Solution Approach 2:
The compound with NC=S group acts as a mediator between the residual palladium catalyst and the product. It forms a solvent-insoluble complex with the catalyst, creating a physical barrier that prevents the catalyst from catalyzing product decomposition during the distillation process, thereby preserving product integrity while achieving purification.
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
The use of dithiocarbamates or thioureas in distillative purification processes prevents decomposition of the coupling reaction products, ensuring high yields even in large-scale industrial production by forming solvent-insoluble palladium complexes that reduce reaction activity.
Implementation Method 1
forming solvent-insoluble palladium complexes that reduce reaction activity
Implementation Method 2
the aryl-, heteroaryl- or alkenyl-substituted unsaturated hydrocarbons is subsequently recovered from said crude product by distillation
Data Source
AI summary
The present invention relates to a method for producing aryl-, heteroaryl- or alkenyl-substituted unsaturated hydrocarbons, containing: reacting aryl halides, heteroaryl halides or alkenyl halides with alkynes or alkenes in the presence of a palladium catalyst to obtain a crude product, and subsequently distillatively purifying the crude product in the presence of a compound having at least one NC=S group.