Catalytic CO2 Carboxylation of Ethene Using Constrained Ligands
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Solution Overview
Problem
The direct addition of CO2 onto ethylene to form acrylic acid is industrially unattractive due to thermodynamic limitations and unfavorable equilibrium, and the formation of nickelalactones does not spontaneously decompose to yield α,β-ethylenically unsaturated carboxylic acid, requiring a catalytic process to shift the equilibrium.
Innovation Solution
A catalytic process involving a transition metal complex with a structurally constrained bidentate P,P ligand, reacting ethene and carbon dioxide in the presence of a base to form α,β-ethylenically unsaturated carboxylic acid salt, where the ligand is selected from specific phosphorous ligands and the transition metal complex activates CO2 and ethene to form a C-C bond, potentially forming a metallalactone intermediate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If direct addition of CO2 onto ethylene is performed, then acrylic acid can be formed, but the reaction is thermodynamically unfavorable and equilibrium lies completely to the side of reactants
Solution Approach 1:
The patent introduces a metallalactone intermediate formed through catalytic cycloaddition of CO2 and ethylene. This intermediate serves as a mediator that enables the reaction to proceed despite unfavorable thermodynamics, as the intermediate can be subsequently hydrolyzed to release acrylic acid and regenerate the catalyst, effectively bypassing the thermodynamic barrier of direct addition
Solution Approach 2:
The patent employs parameter changes by conducting the reaction under elevated pressure conditions and using specific catalyst systems that alter the reaction pathway. The high pressure shifts the equilibrium toward the intermediate, while the catalyst enables the formation and subsequent decomposition of the metallalactone, transforming the thermodynamically unfavorable direct addition into a feasible multi-step process
2Reliability
If nickelalactone is formed by stoichiometric coupling, then the intermediate can be isolated, but it does not spontaneously decompose to yield α,β-ethylenically unsaturated carboxylic acid
Solution Approach 1:
The patent performs preliminary action by forming the metallalactone intermediate under controlled catalytic conditions, then subsequently adding water to trigger its decomposition. This two-stage approach allows the stable intermediate to be formed first, then converted to the desired product when the reaction conditions are changed, ensuring both reliability of intermediate formation and productivity of final product generation
Solution Approach 2:
The patent employs periodic action through the catalytic cycle where the nickel complex repeatedly forms and decomposes the metallalactone. The catalyst enables periodic formation of the stable intermediate followed by its decomposition to release acrylic acid, maintaining continuous productivity while utilizing the stability of the intermediate structure
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 process efficiently converts ethene and carbon dioxide into α,β-ethylenically unsaturated carboxylic acid salt, overcoming thermodynamic limitations and achieving high yields of sodium acrylate, with the use of a base to deprotonate the metallalactone and shift the equilibrium, and the ligands provide structural constraints for enhanced catalytic activity.
Implementation Method 1
reacting ethene and carbon dioxide in the presence of a base to form α,β-ethylenically unsaturated carboxylic acid salt, where the ligand is selected from specific phosphorous ligands and the transition metal complex activates CO2 and ethene to form a C-C bond, potentially forming a metallalactone intermediate
Implementation Method 2
the base deprotonates the metallalactone and shift the equilibrium
Data Source
AI summary
Catalytic process for preparing an α,β-ethylenically unsaturated carboxylic acid salt, comprising reacting an alkene and carbon dioxide in the presence of a carboxylation catalyst and releasing the α,β-ethylenically unsaturated carboxylic acid salt with a base, the carboxylation catalyst being a transition metal complex, which comprises a structurally constrained bidentate P,X ligand, wherein X is selected from the group consisting of P, N, O, and carbene, the P and X atom are separated by 2 to 4 bridging atoms, and wherein the bridging atoms are part of at least one 5- to 7-membered cyclic substructure. A further catalytic processes for preparing α,β-ethylenically unsaturated carboxylic acid derivatives from CO2 and an alkene is provided.