Sulfonated Triorganophosphine Ligands for Hydroformylation
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Solution Overview
Problem
Current hydroformylation processes using aryl-phosphorus ligands suffer from alkyl-aryl exchange reactions, leading to ligand consumption, insoluble non-ionic ligands, and sodium benzenesulfonate accumulation, which affects catalyst stability and reactor fouling.
Innovation Solution
Development of sulfonated triorganophosphine compounds without aryl-phosphorus bonds, featuring bulky alkyl groups for improved stability and solubility, allowing for efficient separation and reduced alkyl-aryl exchange, thereby stabilizing the ligand and enhancing rhodium recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aryl-phosphorus ligands are used in hydroformylation processes, then catalyst activity is maintained, but alkyl-aryl exchange reactions occur leading to ligand consumption and sodium benzenesulfonate accumulation
Solution Approach 1:
The invention extracts and removes the problematic aryl-phosphorus bond from the ligand structure. By designing ligands based on Formula I that contain only alkyl-phosphorus bonds and no aryl-phosphorus bonds, the source of alkyl-aryl exchange reactions is eliminated while retaining the catalytic functionality.
Solution Approach 2:
The invention changes the chemical parameter of the phosphorus substituents from aryl groups to bulky alkyl groups. This parameter change prevents alkyl-aryl exchange reactions while the sulfonate group maintains water solubility and catalytic activity. The bulky alkyl groups provide steric protection that enhances ligand stability.
2Productivity
If aryl-phosphorus ligands are used, then hydroformylation catalysis is effective, but non-ionic ligands become insoluble and remain in the non-polar phase with product
Solution Approach 1:
The invention changes the ionic character parameter of the ligand by incorporating a sulfonate group (SO3M) where M is an alkali metal. This creates a permanently charged ionic ligand that maintains water solubility throughout the reaction, enabling easy phase separation. The ligand remains in the polar aqueous phase while products are in the non-polar phase.
3Productivity
If conventional ligands are used, then catalysis proceeds, but sodium benzenesulfonate accumulates in the polar phase and precipitates causing reactor fouling
Solution Approach 1:
The invention extracts and eliminates the source of sodium benzenesulfonate formation by removing the aryl group from the phosphorus ligand. Without the aryl-phosphorus bond, alkyl-aryl exchange cannot occur, and therefore no benzenesulfonate is generated to cause fouling.
Solution Approach 2:
The invention converts the potential harm of sulfonate accumulation into a benefit by designing the ligand with a sulfonate group from the outset. The sulfonate group provides water solubility and ionic character that prevent phase separation issues and reactor fouling, turning a problematic byproduct into a desirable ligand feature.
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 novel sulfonated triorganophosphine compounds provide comparable olefin conversion and product selectivity to prior art catalysts while preventing alkyl-aryl exchange, ensuring stable catalyst performance and easy separation of reaction products.
Implementation Method 1
transition metal-organophosphorus ligand complex catalyst... capable of catalyzing hydroformylation processes
Implementation Method 2
water-soluble ionic ligand, preferably, an alkali metal salt of a dihydrocarbylarylphosphine monosulfonate compound
Implementation Method 3
addition of water, as disclosed for example in US 5,180,854, under conditions sufficient to obtain a non-polar phase containing one or more aldehyde products and any non-polar solvent(s) as may be present and a polar phase containing the rhodium-ligand catalyst
Data Source
Figure 1
AI summary
A compound comprising a class of sulfonated triorganophosphine compounds of formula R1R2P-R3[-O-(CH2)n-(SO3M)]m, wherein the R1 and R2 are selected individually from alkyl, aralkyl, and alicyclic groups, wherein R3 represents a divalent or polyvalent alkylene or alicyclic radical that is bonded to the phosphorus atom and to one or more sulfonate substituents via an alkylether link, and further wherein R3 does not contain any aryl moieties; n is an integer reflecting a number of methylene groups in the alkylether link; M represents a monovalent cation; and m is an integer representing a total number of sulfonated alkylether substituents. The compound is useful as a ligand in transition metal-ligand complex catalysts that are capable of catalyzing the hydroformylation of an olefinically-unsaturated compound with carbon monoxide and hydrogen to form one or more corresponding aldehyde products. The ligand is incapable of alky-aryl exchange, thereby leading to reduced ligand usage and improving ligand and rhodium recovery and recycling.