Diaryl Carbonate Synthesis via Catalyst Crystallization
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Solution Overview
Problem
Existing processes for producing diaryl carbonates from monophenols and phosgene generate significant wastewater and require complex processing steps, with inadequate catalyst recycling and low product purity, failing to meet economic and ecological requirements.
Innovation Solution
A process using optionally substituted pyridine or its hydrochloride salt as a catalyst, where the reaction is conducted in the liquid phase without additional solvents, allowing for catalyst separation and recycling via crystallization, and hydrogen chloride is purified for reuse, avoiding aqueous solutions and neutralization steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aqueous solutions and neutralization steps are used to separate catalyst from reaction mixture, then catalyst separation is achieved, but significant wastewater is generated and processing complexity increases
Solution Approach 1:
The patent changes the physical state parameter of the reaction system by conducting the reaction in the melt phase rather than aqueous solution, and uses temperature-controlled crystallization to separate the catalyst as a solid hydrochloride salt. This parameter change eliminates the need for aqueous neutralization steps and prevents wastewater generation while achieving effective catalyst separation.
Solution Approach 2:
The patent utilizes phase transitions of the catalyst: during the reaction the catalyst is in liquid phase dissolved in the melt, then during workup it transitions to solid phase through crystallization of its hydrochloride salt. This phase transition enables simple filtration and separation without requiring aqueous solutions, thereby eliminating wastewater generation.
2Productivity
If additional solvents are used in the reaction, then reactant solubility and reaction efficiency are improved, but product purification complexity and processing costs increase
Solution Approach 1:
The patent removes the additional solvent from the reaction system entirely, using only the melt of reactants and catalyst. This extraction of the unnecessary component (additional solvent) simplifies the system and eliminates the need for complex solvent removal and purification steps, while the reaction proceeds efficiently in the melt phase.
Solution Approach 2:
The patent achieves a homogeneous reaction mixture using only the melt of phenol and catalyst without additional solvents. The homogeneity of this simplified system facilitates easier product purification compared to multi-solvent systems, reducing processing complexity while maintaining reaction efficiency.
3Ease of manufacture
If catalyst is not recycled, then process simplicity is maintained, but operational costs increase and environmental impact worsens
Solution Approach 1:
The patent implements catalyst recovery by crystallizing the catalyst hydrochloride salt from the reaction mixture, filtering it out, and converting it back to the active catalyst form. This recovery process prevents catalyst loss and enables recycling, reducing operational costs and environmental impact while maintaining process simplicity through an efficient separation method.
4Ease of operation
If phase interface process with inert solvent is used, then reaction between monophenol and phosgene is facilitated, but separation of diaryl carbonate from solvent and reprocessing requirements increase
Solution Approach 1:
The patent changes the reaction medium from inert solvent to reactant melt, fundamentally altering the system parameters. This eliminates the need for product separation from solvent, as the reaction occurs in the melt of the reactants themselves, and product purification is achieved through simple crystallization without complex reprocessing steps.
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 approach achieves high-purity diaryl carbonates with efficient catalyst recycling, reducing wastewater and operational costs, and enabling the production of high-purity polycarbonates while minimizing environmental impact.
Implementation Method 1
reacting a monophenol with phosgene and/or at least one aryl chloroformate in the presence of at least one optionally substituted pyridine, in free form and/or in the form of its hydrochloride salt, as a catalyst
Implementation Method 2
the reaction mixture is transferred from the reactor into an apparatus suitable for suspension crystallization, c) suspension crystallization is initiated in the apparatus by lowering the temperature, d) the resulting crystals are separated from the remaining catalyst-containing mother liquor
Implementation Method 3
suspension crystallization is initiated in the apparatus by lowering the temperature
Data Source
Figure 1
AI summary
The invention concerns a method for producing diaryl carbonates from monophenols and phosgene or chloroformic acid aryl esters in the presence of an optionally substituted pyridine or the hydrochloride salt thereof as catalyst, and the recovery and reinjection thereof back into the method. The method is carried out at least partially in a liquid phase without the use of an additional solvent, the catalyst being separated by means of crystallisation and recovered.