MCM-22 Catalyst Selectivity in Cyclohexylbenzene Hydroalkylation
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Solution Overview
Problem
Current processes for producing cyclohexylbenzene, such as hydroalkylation over zeolite catalysts, suffer from low selectivity to cyclohexylbenzene and high production of unwanted by-products like cyclohexane and methylcyclopentane, making them economically unviable.
Innovation Solution
A bifunctional catalyst system comprising an aluminosilicate molecular sieve of the MCM-22 family and a hydrogenation metal, with an acid-to-metal molar ratio of 75 to 750, is used for hydroalkylation of benzene, enhancing selectivity to monocyclohexylbenzene and reducing selectivity to dicyclohexylbenzene and cyclohexane, followed by oxidation and cleavage to produce phenol and cyclohexanone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydroalkylation is conducted over conventional zeolite catalysts (zeolites X, Y, or beta) to produce cyclohexylbenzene, then benzene conversion can be achieved, but the selectivity to cyclohexylbenzene is low and large quantities of unwanted by-products (cyclohexane and methylcyclopentane) are produced
Solution Approach 1:
The patent applies parameter changes by modifying the catalyst's acid-to-metal molar ratio to a specific range (75-750), which fundamentally alters the reaction selectivity. This parameter optimization transforms the catalyst's performance to achieve high cyclohexylbenzene selectivity while minimizing by-product formation, directly resolving the technical contradiction between conversion and selectivity.
Solution Approach 2:
The patent employs a composite catalyst system combining aluminosilicate molecular sieve (MCM-22 family) with hydrogenation metal. This composite material integrates the shape-selective properties of the molecular sieve with the hydrogenation activity of the metal, creating a synergistic effect that enhances cyclohexylbenzene selectivity and reduces harmful by-products through the combined functions of both materials.
2Productivity
If benzene conversion is increased to improve productivity, then more cyclohexylbenzene can be produced, but selectivity decreases and by-product formation increases
Solution Approach 1:
The patent resolves this contradiction by optimizing the acid-to-metal molar ratio parameter (75-750 range), which enables the catalyst to maintain high selectivity even at elevated benzene conversion rates. This parameter tuning allows the system to achieve both high productivity and high manufacturing precision simultaneously, breaking the traditional trade-off between conversion and selectivity.
Solution Approach 2:
The patent utilizes the MCM-22 molecular sieve structure with its specific pore geometry and acid site distribution, which copies the optimal catalytic environment found in natural zeolites but with enhanced controllable properties. This structural copying and optimization enables high selectivity maintenance at high conversion rates by providing uniform active sites that favor the desired reaction pathway.
3Ease of manufacture
If conventional catalysts are used for hydroalkylation, then the process can proceed, but economically viable operation is not achieved due to low selectivity and high by-product production
Solution Approach 1:
The patent achieves economic viability by changing the catalyst composition parameters, specifically the acid-to-metal molar ratio (75-750). This parameter modification dramatically improves selectivity to cyclohexylbenzene, reducing by-product formation and subsequent separation costs, thereby making the manufacturing process economically viable while maintaining high manufacturing precision.
Solution Approach 2:
The patent employs a composite catalyst system that combines the shape-selective MCM-22 molecular sieve with hydrogenation metal, creating a material with enhanced catalytic performance. This composite approach improves both selectivity and process economics by minimizing by-product formation and maximizing desired product yield, directly addressing the economic viability challenge.
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 significantly increases the selectivity to cyclohexylbenzene and reduces by-product formation, making the process more economically viable and efficient in producing phenol and cyclohexanone.
Implementation Method 1
contacting the benzene and hydrogen in said at least one reaction zone under hydroalkylation conditions with a catalyst system comprising an aluminosilicate molecular sieve having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstrom, and at least one hydrogenation metal to produce an effluent containing cyclohexylbenzene
Implementation Method 2
oxidation of cyclohexylbenzene (analogous to cumene oxidation) could offer an alternative route for phenol production
Implementation Method 3
cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone
Data Source
AI summary
In a process for producing cyclohexylbenzene, benzene and hydrogen are fed to at least one reaction zone. The benzene and hydrogen are then contacted in the at least one reaction zone under hydroalkylation conditions with a catalyst system comprising a molecular sieve having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstrom, and at least one hydrogenation metal to produce an effluent containing cyclohexylbenzene. The catalyst system has an acid- to-metal molar ratio of from about 75 to about 750.