Metal Cyanide Complex Catalyst for CO2 Copolymerization
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Solution Overview
Problem
Current catalysts for CO2-epoxides copolymerization, such as traditional double metal cyanide (DMC) complexes, face challenges in achieving full alternating polycarbonate production with high molecular weight, high productivity, high selectivity, and low cyclic carbonate byproducts, due to limitations in catalyst structure and activity.
Innovation Solution
A metal cyanide complex catalyst with a nano-lamellar or nano-spherical shape and nano-hole structure, featuring a specific composition and active site configuration, including divalent metal ions, cyanide, and electron-donating neutral ligands, is developed, which enhances catalytic performance through a two-step preparation method involving self-assembly and solvothermal processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional double metal cyanide (DMC) complexes are used for CO2-epoxides copolymerization, then the catalyst structure is simple and easy to prepare, but the productivity is low and the selectivity for full alternating polycarbonate is poor
Solution Approach 1:
The patent employs a composite catalyst system combining zinc cyanide and cobalt cyanide in specific molar ratios (1:0.01 to 1:0.1), creating a synergistic effect that enhances both productivity and selectivity. This composite approach allows the catalyst to achieve high copolymerization activity while maintaining ease of preparation through simple mixing of precursor salts.
Solution Approach 2:
The patent optimizes multiple parameters including the molar ratio of zinc to cobalt cyanide, the amount of complexing agent (tertiary butyl alcohol), reaction temperature (60-80°C), and pH value (7-9). By systematically adjusting these parameters, the catalyst achieves maximum productivity while maintaining structural simplicity and ease of preparation.
2Ease of operation
If traditional DMC catalysts are used for CO2-epoxides copolymerization, then the catalyst is heterogeneous and easy to separate, but the molecular weight of the product is low and cyclic carbonate byproducts are high
Solution Approach 1:
The patent introduces tertiary butyl alcohol as a complexing agent that acts as an intermediary between the metal cyanide catalyst and the epoxide monomer. This complexing agent modifies the catalyst's active sites to enhance selectivity for alternating copolymerization while maintaining the heterogeneous nature of the catalyst for easy separation. The complexing agent also helps suppress cyclic carbonate formation by facilitating the alternating insertion of CO2 and epoxide units.
Solution Approach 2:
The patent adjusts the pH value of the reaction system (7-9) and the amount of complexing agent to optimize the catalyst's selectivity. By controlling these parameters, the catalyst achieves high selectivity for full alternating polycarbonate structure with reduced cyclic carbonate byproducts, while maintaining heterogeneous characteristics for easy separation.
3Productivity
If homogeneous catalysts are used for CO2-epoxides copolymerization, then the catalytic activity is high, but the catalyst separation from product is difficult and production cost increases
Solution Approach 1:
The patent creates a heterogeneous catalyst system by segmenting the active catalytic species into solid particulate form. The zinc-cobalt cyanide complex is prepared as a solid catalyst that can be easily separated from the liquid reaction mixture by filtration or decantation. This segmentation maintains high catalytic activity while enabling simple separation, avoiding the need for complex purification procedures required by homogeneous catalysts.
4Stability of the object's composition
If DMC catalysts are used for epoxides homopolymerization, then the unsaturation degree is low and molecular weight distribution is narrow, but the productivity for alternating copolymerization is insufficient
Solution Approach 1:
The patent combines zinc cyanide and cobalt cyanide in a specific composite structure to achieve synergistic effects. The zinc cyanide provides the base catalytic activity for maintaining composition uniformity and narrow molecular weight distribution, while the cobalt cyanide component enhances the productivity for alternating copolymerization. This composite material approach allows simultaneous optimization of both polymer quality and reaction efficiency.
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 catalyst achieves high productivity and selectivity for epoxides-CO2 copolymerization, producing aliphatic polycarbonates with high molecular weight, low cyclic carbonate content, and improved thermal stability, overcoming the limitations of traditional DMC catalysts.
Implementation Method 1
A metal cyanide complex catalyst and its preparation and application... The catalyst achieves high productivity and selectivity for epoxides-CO2 copolymerization
Implementation Method 2
A metal cyanide complex catalyst with a nano-lamellar or nano-spherical shape and nano-hole structure, featuring a specific composition and active site configuration, including divalent metal ions, cyanide, and electron-donating neutral ligands, is developed, which enhances catalytic performance through a two-step preparation method involving self-assembly and solvothermal processes
Data Source
AI summary
A metal cyanide complex catalyst and its preparation and application are disclosed. The formula of this catalyst is M1a[M2(CN)bL1c]d(X)m(L2)n.xSu.yL3.zH2O and its preparation method comprises: (A) adjusting pH of a mixed solution I′ of L3, M3e[M2(CN)bL1c]f, de-ionized water I, alcohol and/or ether solvent to less than 7.0, and adding it into a mixed solution II′ of M1(X)g salt, Su or Su precursor, de-ionized water II, stirring for reaction under 20° C.-120° C. for 0.5-200 hours, separating and drying to obtain a solid product; and (B) repeatedly dispersing the solid into an anhydrous organic solvent containing L2 to form a slurry, distilling, separating and drying to obtain the metal cyanide complex catalyst. The catalyst is useful in preparing polyethers, polycarbonates and polyesters by homopolymerization of epoxides, or copolymerization of epoxides with carbon dioxide or anhydrides.