Dimeric Aluminum Salen Catalyst Synthesis of Cyclic Carbonates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for synthesizing cyclic carbonates from epoxides and carbon dioxide require elevated temperatures and high pressures, or involve long reaction times, making them inefficient and costly.
Innovation Solution
The use of dimeric aluminium(salen) complexes as catalysts, in combination with a co-catalyst capable of supplying Y− (such as Cl, Br, or I), allows for the synthesis of cyclic carbonates at room temperature and atmospheric pressure with short reaction times, using commercially viable amounts of catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional catalysts (metal halide and Lewis base) are used for synthesizing cyclic carbonates, then the reaction can proceed at room temperature and atmospheric pressure, but the reaction time is excessively long (3.5 to 93 hours)
Solution Approach 1:
The invention changes the chemical structure parameter of the catalyst from conventional metal halide/Lewis base combinations to dimeric aluminium(salen) complexes with specific molecular architecture. This structural parameter change enables the reaction to proceed 4-27 times faster than conventional catalysts while maintaining room temperature and atmospheric pressure conditions, directly resolving the contradiction between gentle reaction conditions and acceptable reaction time
Solution Approach 2:
The invention employs a composite catalytic system consisting of dimeric aluminium(salen) complex and a quaternary ammonium salt co-catalyst. This composite approach combines the advantages of both components: the dimeric aluminium(salen) provides high catalytic activity and selectivity, while the quaternary ammonium salt enhances the reaction efficiency. The synergistic effect of this composite system achieves dramatically reduced reaction times (3-24 hours) under mild conditions
2Temperature
If tetradentate Schiff-base aluminium complexes are used as catalysts, then the reaction proceeds at room temperature and about 6 atmospheres pressure, but the reaction time remains long and catalyst loading is high
Solution Approach 1:
The invention segments the catalyst structure by using dimeric aluminium(salen) complexes where two aluminium centers are bridged by a specific ligand framework. This segmentation creates active sites with optimized geometry and electronic properties that are more effective than monomeric or tetradentate Schiff-base complexes. The segmented dimeric structure enables higher turnover frequencies and lower catalyst loading (0.1-10 mol%), significantly improving productivity while maintaining room temperature operation
Solution Approach 2:
The invention introduces a quaternary ammonium salt as an intermediary co-catalyst that mediates the reaction between epoxide and carbon dioxide. This intermediary component facilitates the formation of the active catalytic species and enhances the overall reaction efficiency. The co-catalyst works synergistically with the dimeric aluminium(salen) complex to achieve high productivity under mild conditions, resolving the contradiction between gentle temperature conditions and reaction efficiency
3Productivity
If the reaction is conducted in supercritical carbon dioxide or at elevated temperatures and high pressures, then the reaction rate increases, but the process becomes less economical and more complex
Solution Approach 1:
The invention enables the catalyst system to be self-sufficient under ambient conditions (room temperature and atmospheric pressure), eliminating the need for complex pressurization equipment, temperature control systems, and safety infrastructure required for supercritical or high-pressure processes. The dimeric aluminium(salen) complex with quaternary ammonium salt co-catalyst maintains high activity and selectivity without external energy input or complex process conditions, thereby reducing device complexity and operational costs while achieving acceptable reaction rates (3-24 hours)
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 enables the efficient production of cyclic carbonates with yields of over 50% in short reaction times, typically 3 to 24 hours, at accessible temperatures and pressures, using dimeric aluminium(salen) catalysts and a co-catalyst, such as Bu4NBr, which is economically and environmentally beneficial.
Implementation Method 1
dimeric aluminium(salen) complexes are highly active catalysts for the reaction of epoxides with carbon dioxide to produce cyclic carbonates
Data Source
AI summary
A process for the production of cyclic carbonates comprising contacting an epoxide with carbon dioxide in the presence of a dimeric aluminum(salen) catalyst, and a co-catalyst capable of supplying Y−, where Y is selected from Cl, Br and I, where the dimeric aluminum(salen) catalyst is of formula I: