MCM-22 Catalyst Pore Structure for Monoalkylation Selectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing catalysts for the alkylation of aromatic hydrocarbons produce undesired polyalkylated impurities alongside the desired monoalkylated compounds, necessitating a catalyst composition that enhances selectivity to monoalkylated aromatic compounds while maintaining equivalent activity.
Innovation Solution
A catalyst composition comprising a crystalline MCM-22 family molecular sieve and a binder, characterized by a cumulative extra-molecular sieve pore volume greater than or equal to 0.122 ml/g for pores between 2 nm and 8 nm, along with a second molecular sieve having a Constraint Index of less than 12, is used in the alkylation or transalkylation process to increase monoalkylated aromatic compound selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional zeolite catalysts are used for alkylation of aromatic hydrocarbons, then catalytic activity is achieved, but polyalkylated impurities are produced reducing selectivity to monoalkylated compounds
Solution Approach 1:
The patent employs a catalyst composition with controlled porosity, specifically using MCM-22 molecular sieve combined with a binder to create a hierarchical pore structure. The extra-molecular sieve pore volume is optimized to greater than or equal to 0.122 ml/g for pores between 2-8 nm, allowing selective diffusion of reactants and products while preventing polyalkylation reactions that would generate harmful impurities.
Solution Approach 2:
The invention creates a composite catalyst system combining MCM-22 family molecular sieve with a binder material. This composite structure integrates the shape-selective properties of the molecular sieve with the mechanical stability and additional porosity provided by the binder, achieving both high activity and enhanced selectivity to monoalkylated products while minimizing polyalkylated impurity formation.
2Manufacturing precision
If catalyst composition is optimized for high selectivity to monoalkylated compounds, then polyalkylated impurities are reduced, but catalytic activity may be compromised
Solution Approach 1:
The patent optimizes critical parameters including the extra-molecular sieve pore volume (greater than or equal to 0.122 ml/g), pore diameter distribution (2-8 nm range), and the ratio of molecular sieve to binder. These parameter optimizations enable the catalyst to maintain high catalytic activity through adequate pore accessibility while simultaneously achieving high selectivity through controlled molecular diffusion pathways that favor monoalkylation.
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 composition significantly enhances the selectivity to monoalkylated aromatic compounds, such as ethylbenzene and cumene, by optimizing the pore structure and molecular sieve combination, thereby reducing polyalkylated impurities and maintaining activity levels.
Implementation Method 1
a catalyst composition comprising: (a) a crystalline MCM-22 family molecular sieve; and (b) a binder, wherein the catalyst composition is characterized by a cumulative extra-molecular sieve pore volume greater than or equal to 0.122 ml/g for pores having a pore diameter ranging from about 2 nm to about 8 nm
Implementation Method 2
the catalyst composition is characterized by a cumulative extra-molecular sieve pore volume greater than or equal to 0.122 ml/g for pores having a pore diameter ranging from about 2 nm to about 8 nm, wherein the pore volume is measured by N2 porosimetry
Implementation Method 3
The alkylation of aromatic hydrocarbon compounds employing zeolite catalysts is known and understood in the art
Implementation Method 4
The hydrocarbon conversions comprise alkylation and/or transalkylation of alkylatable aromatics
Data Source
AI summary
A catalyst composition comprises a crystalline MCM-22 family molecular sieve and a binder, wherein the catalyst composition is characterized by an extra-molecular sieve porosity greater than or equal to 0.122 ml/g for pores having a pore diameter ranging from about 2 nm to about 8 nm, wherein the porosity is measured by N2 porosimetry. The catalyst composition may be used for the process of alkylation or transalkylation of an alkylatable aromatic compound with an alkylating agent. The molecular sieve may have a Constraint Index of less than 12, e.g., less than 2. Examples of molecular sieve useful for this disclosure are a MCM-22 family molecular sieve, zeolite Y, and zeolite Beta.