Mixed Acid-Modified Zn-Co DMC Catalyst for CO2 Fixation
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Solution Overview
Problem
Current Zn-Co DMC catalysts used in industry for synthesizing polycarbonate polyether polyols have low catalytic activity and selectivity, leading to increased production costs due to high catalyst residues and extended reaction times when the mass ratio of catalyst to epoxide monomer exceeds 1/1000, resulting in decreased carbon dioxide fixation rates and increased energy consumption.
Innovation Solution
A mixed-acid modified zinc-cobalt double metal cyanide (Zn-Co DMC) catalyst is synthesized by reacting water-soluble zinc and cobalt salts in the presence of a mixed acid comprising organic and inorganic acids, such as succinic acid and diluted sulfuric acid, which increases the catalyst's specific surface area and thermal stability, enhancing catalytic activity and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Zn-Co DMC catalyst is used with mass ratio exceeding 1/1000, then catalytic activity is sufficient, but production cost increases due to high catalyst residues
Solution Approach 1:
The invention changes the chemical composition parameters of the catalyst by incorporating mixed acids (formic acid, acetic acid, propionic acid, or butyric acid) with specific content ratios (0.1-10% by mass) into the Zn-Co DMC catalyst system. This parameter modification enables the catalyst to achieve high activity at lower loading levels (mass ratio ≤ 1/1000), thereby reducing catalyst residues in the final product while maintaining sufficient catalytic performance
Solution Approach 2:
The invention creates a composite catalyst material by combining conventional Zn-Co DMC catalyst with specific mixed acids to form an acid-modified catalyst system. This composite structure leverages the synergistic effect between the DMC catalyst and the acid components, achieving enhanced catalytic efficiency that allows reduced catalyst dosage while maintaining or improving activity, thus resolving the contradiction between sufficient activity and reduced residues
2Productivity
If conventional Zn-Co DMC catalyst is used, then reaction can proceed, but reaction time is extended leading to decreased productivity
Solution Approach 1:
The invention modifies the catalytic system parameters by introducing mixed acids with specific types and concentrations, which fundamentally changes the reaction kinetics. The acid-modified catalyst demonstrates significantly enhanced activity, reducing reaction time from extended periods to 2-6 hours while maintaining stable catalytic performance, thus improving productivity without sacrificing reliability
3Use of energy by moving object
If conventional Zn-Co DMC catalyst is used, then polymerization occurs, but carbon dioxide fixation rate is low increasing energy consumption
Solution Approach 1:
The invention changes the catalytic system's chemical parameters by incorporating mixed acids, which significantly enhances the carbon dioxide fixation rate. The acid-modified catalyst promotes more efficient CO2 incorporation into the polymer structure, achieving fixation rates exceeding 50% under optimized conditions (catalyst mass ratio 1/1000 to 1/5000, reaction temperature 80-120°C, reaction time 2-6 hours). This improved fixation efficiency reduces energy consumption by eliminating the need for extended reaction times and additional processing 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
The modified catalyst exhibits higher catalytic activity and selectivity, achieving monomer conversion rates greater than 50% within 1-2 hours at a lower catalyst concentration and higher reaction temperatures, with a higher proportion of polycarbonate structure in the polymer, thereby reducing production costs and improving energy efficiency.
Implementation Method 1
The catalyst is modified by a mixed acid during synthesis of the catalyst, and the mixed acid comprises at least one organic acid and at least one water-soluble inorganic acid
Implementation Method 2
The catalyst is obtained by reacting water-soluble metal salt of zinc and cobalt in water-soluble solvent, and the water-soluble metal salt of cobalt is cyanide salt of cobalt
Data Source
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AI summary
The disclosure provides a double metal cyanide catalyst, a method for preparing the double metal cyanide catalyst and a method for catalyzing a polymerization reaction using the double metal cyanide catalyst. The metal elements of the catalyst comprise only the two metal elements of zinc and cobalt, besides impurities. The catalyst is obtained by reacting water-soluble metal salts of zinc and cobalt in water-soluble solvents. The catalyst is modified by a mixed acid during synthesis, the mixed acid comprising at least one organic acid and at least one water-soluble inorganic acid. the water-soluble inorganic acid is selected from the group consisting of diluted sulfuric acid and diluted hydrochloric acid, with a pH value being in the range of 0 to 5; and the organic acid is any one or more selected from the group consisting of succinic acid, glutaric acid, phthalic acid, iminodiacetic acid, pyromellitic acid, and 1,2,3,4-butanetetracarboxylic acid, the water-soluble inorganic acid and organic acid being in a molar ratio of 1:10 to 10:1. The catalyst of the present disclosure has a high activity and a strong thermal stability, achieving a higher catalytic activity for a polymerization reaction, a high polymer product yield and a higher selectivity over the polycarbonate segment on the polymer backbone with a lower catalyst concentration and a higher initiator concentration.