Low Micropore Zeolite Catalyst for Methyl Acetate Carbonylation
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Solution Overview
Problem
Zeolite catalysts used in carbonylation processes for producing methyl acetate by carbonylating dimethyl ether with carbon monoxide exhibit an induction period during which undesirable hydrocarbon materials are generated instead of the desired product, reducing catalyst selectivity and efficiency.
Innovation Solution
A zeolite catalyst with a micropore volume of 0.01 ml/g or less, specifically a mordenite-based catalyst in an ion-exchanged form, is used, where the organic structure directing agent is not removed, allowing for improved access to active sites and enhanced selectivity to methyl acetate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the organic structure directing agent is removed by calcining at high temperature, then the catalyst structure is formed, but the induction period increases and selectivity decreases
Solution Approach 1:
The patent extracts only the essential function of the structure directing agent (forming the zeolite framework) while removing its harmful effect (causing long induction period). This is achieved by using a minimal amount of structure directing agent during synthesis, then completely removing it through calcination, thereby eliminating the source of the induction period while maintaining catalyst selectivity.
Solution Approach 2:
The zeolite catalyst is pre-treated by calcination at high temperature (500-600°C) before use in the carbonylation reaction. This preliminary action completely removes the organic structure directing agent from the catalyst pores, preventing it from causing the induction period during the actual reaction while maintaining the zeolite's selective catalytic properties.
2Reliability
If the micropore volume is reduced to 0.01 ml/g or less, then selectivity to methyl acetate increases, but access to active sites may be restricted
Solution Approach 1:
The patent creates a highly selective local environment within the zeolite pores by reducing micropore volume to 0.01 ml/g or less. This localized confinement effect enhances selectivity to methyl acetate by restricting the transition state geometry, while the extr framework porosity ensures adequate mass transport of reactants and products.
Solution Approach 2:
The patent addresses the access problem by developing a hierarchical pore structure that combines micropores (for selectivity) with mesopores or macropores (for transport). This multi-dimensional pore architecture allows reactants to access active sites through larger pores while the micropore regions provide the selective environment needed for high methyl acetate selectivity.
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 use of a zeolite catalyst with reduced micropore volume significantly shortens the induction period, increasing selectivity to methyl acetate and decreasing by-product formation, particularly during the initial stages of the carbonylation reaction.
Implementation Method 1
Solid crystalline aluminosilicate zeolite catalysts have been known to be effective for the carbonylation of dimethyl ether with carbon monoxide to form methyl acetate
Implementation Method 2
Structure directing agents may be inorganic or organic. Typically, structure directing agents are removed from a resultant zeolite prior to its use as a catalyst. A variety of methods are known to remove structure directing agents, including by calcining at high temperature.
Data Source
AI summary
A catalyst and process for the production of methyl acetate by contacting dimethyl ether and carbon monoxide in the presence of a catalyst which is a zeolite of micropore volume of 0.01 ml/g or less.