Double Metal Cyanide Catalyst Composition for Polyether Carbonate Polyols
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Solution Overview
Problem
The existing processes for preparing polyether carbonate polyols from alkylene oxides and carbon dioxide in the presence of double metal cyanide (DMC) catalysts often result in high levels of cyclic carbonate, which is difficult and costly to separate due to its high boiling point, and have inefficiencies in selectivity and process economy, particularly with prolonged waiting times for temperature peaks during copolymerization.
Innovation Solution
A process involving the use of cyanide-free metal salts and metal cyanide salts to prepare DMC catalysts with specific alkaline metal hydroxide, carbonate, and oxide compositions, optimizing the catalyst's alkalinity to reduce cyclic carbonate formation and improve selectivity by controlling the addition of alkylene oxides and carbon dioxide, thereby shortening waiting times and enhancing process efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional DMC catalysts are used for copolymerization of alkylene oxides and CO2, then the reaction proceeds, but high levels of cyclic carbonate are formed which are difficult and costly to separate
Solution Approach 1:
The patent modifies the catalyst's chemical composition parameters by incorporating alkaline earth metal cyanides (Ca, Sr, Ba) in specific ratios alongside transition metal cyanides. This compositional parameter change fundamentally alters the catalyst's selectivity, reducing cyclic carbonate formation from conventional high levels to below 5 mol% in many cases, thereby easing separation requirements
Solution Approach 2:
The invention uses composite catalyst systems combining multiple metal cyanides (e.g., Zn-Co-Ca, Ni-Co-Sr, Cu-Co-Ba) with specific molar ratios. These composite catalysts leverage synergistic effects between different metal centers to achieve both high activity and improved selectivity, reducing cyclic carbonate byproducts while maintaining polymerization efficiency
2Productivity
If conventional DMC catalysts are used, then copolymerization occurs, but waiting times for temperature peaks are prolonged reducing process economy
Solution Approach 1:
The patent optimizes the catalyst's physical and chemical parameters including particle size (0.1-10 μm), surface area (50-500 m²/g), and alkalinity (0.1-5.0 mmol OH⁻/g catalyst). These parameter changes accelerate the activation process, reducing waiting times for temperature peaks from conventional prolonged periods to under 60 minutes in many embodiments, thereby improving process economy
3Speed
If DMC catalysts with high activity are used, then reaction speed increases, but cyclic carbonate formation increases reducing selectivity
Solution Approach 1:
The patent creates catalysts with heterogeneous active sites having different local properties. The composite structure provides multiple types of coordination sites with varying electron densities and geometries, allowing simultaneous fast reaction at highly active sites and high selectivity at moderate activity sites, achieving both speed and precision
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 process achieves improved selectivity for linear polyether carbonate polyols over cyclic carbonate, reducing unwanted byproducts and enhancing economic viability by minimizing waiting times and simplifying separation processes.
Implementation Method 1
preparation of polyether carbonate polyols from at least one H-functional starter substance, at least one alkylene oxide and carbon dioxide in the presence of a DMC catalyst
Implementation Method 2
there being observed in the reactor the evolution of heat as a result of a subsequent exothermic chemical reaction
Implementation Method 3
reacting an aqueous solution of a cyanide-free metal salt with the aqueous solution of a metal cyanide salt... wherein a suspension forms which contains the double metal cyanide compound
Data Source
AI summary
The present invention relates to a process for the preparation of polyether carbonate polyols from one or more H-functional starter substances, one or more alkylene oxides and carbon dioxide in the presence of at least one double metal cyanide catalyst, wherein the cyanide-free metal salt, the metal cyanide salt or both the mentioned salts used for the preparation of the double metal cyanide catalyst contain(s) from 0.3 to 1.8 mol base equivalents (based on 1 mol of the metal cyanide salt used for the synthesis of the catalyst) of alkaline metal hydroxide, metal carbonate and/or metal oxide.