EMM-12 Molecular Sieve Hydroalkylation Selectivity
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Solution Overview
Problem
Existing hydroalkylation processes for producing cyclohexylbenzene suffer from low selectivity and high production of unwanted by-products, such as cyclohexane and methylcyclopentane, due to the inefficiency of conventional catalysts like nickel- and rare earth-treated zeolites.
Innovation Solution
A hydroalkylation process using a bifunctional catalyst system comprising a molecular sieve EMM-12 and at least one hydrogenation metal, which includes an inorganic oxide support for the hydrogenation metal, optimizing the X-ray diffraction pattern to enhance the production of monocycloalkyl-substituted aromatic compounds like cyclohexylbenzene while minimizing di-cycloalkyl-substituted by-products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional catalysts like nickel- and rare earth-treated zeolites are used for hydroalkylation, then the process can proceed, but selectivity is low and unwanted by-products such as cyclohexane and methylcyclopentane are produced in high amounts
Solution Approach 1:
The patent changes the fundamental parameters of the catalyst system by using a bifunctional catalyst comprising EMM-12 molecular sieve with specific XRD characteristics (d-spacing maxima at 12.33±0.23 Å and 13.18±0.25 Å) combined with hydrogenation metals (Ru, Rh, Ir, Pd, Pt, Ni, Co, or Cu). This parameter change in catalyst composition and structure achieves high selectivity for cyclohexylbenzene while minimizing by-products like cyclohexane and methylcyclopentane.
Solution Approach 2:
The invention employs a composite catalyst system combining EMM-12 molecular sieve with specific hydrogenation metals. The EMM-12 provides the framework structure with defined pore geometry and acidity, while the hydrogenation metals provide catalytic activity for hydrogenation and hydroalkylation. This composite approach enables simultaneous control of reaction pathways to achieve high selectivity and minimize unwanted by-products.
2Manufacturing precision
If conventional catalysts are used for hydroalkylation of benzene, then the reaction can occur, but the ratio of monocycloalkyl-substituted to di-cycloalkyl-substituted aromatic compounds is unfavorable
Solution Approach 1:
The patent optimizes reaction parameters including temperature (50-350°C, preferably 100-250°C), pressure (100-7000 kPa, preferably 500-5000 kPa), and benzene to hydrogen molar ratio (0.01-100, preferably 0.1-10) to achieve favorable product distribution. The EMM-12 catalyst with its specific pore structure and acidity enables selective formation of monocycloalkyl-substituted compounds while suppressing di-cycloalkyl-substituted by-products, achieving ratios greater than 10:1 in many cases.
Solution Approach 2:
The invention replaces conventional catalyst systems with a specifically designed bifunctional catalyst system where the EMM-12 molecular sieve provides shape-selective catalysis through its unique pore structure. The catalyst's acidic sites and metal hydrogenation sites work synergistically to control the reaction mechanism, favoring mono-substitution over di-substitution and eliminating the need for complex process control mechanisms.
3Productivity
If conventional catalysts are used, then hydroalkylation can proceed, but the overall efficiency and selectivity of cyclohexylbenzene production are poor
Solution Approach 1:
The patent achieves both high productivity and high selectivity by using EMM-12 molecular sieve with hydrogenation metals under optimized conditions. The catalyst enables the reaction to proceed efficiently at moderate temperatures and pressures while maintaining selectivity for cyclohexylbenzene. The synergistic action of the molecular sieve's acidic sites and the metals' hydrogenation activity creates an efficient catalytic cycle that maximizes product formation while minimizing side reactions.
Solution Approach 2:
The EMM-12 molecular sieve acts as an intermediary that facilitates the hydroalkylation reaction by providing a controlled environment within its pores. The catalyst mediates between the reactants (aromatic compound and hydrogen) and the desired product (cyclohexyl-substituted aromatic compound), controlling the reaction pathway to achieve both high efficiency and high selectivity simultaneously.
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 process achieves a favorable ratio of monocycloalkyl-substituted to di-cycloalkyl-substituted aromatic compounds, reducing unwanted by-products and improving the selectivity and efficiency of cyclohexylbenzene production.
Implementation Method 1
a process for the hydroalkylation of benzene to produce cyclohexylbenzene, using a molecular sieve composition designated as EMM-12 which is an MCM-22 family material having unique XRD features
Implementation Method 2
a bifunctional catalyst system comprising a molecular sieve EMM-12 and at least one hydrogenation metal
Data Source
AI summary
This disclosure relates to a process for manufacturing a mono-cycloalkyl-substituted aromatic compound, said process comprising contacting a feedstock comprising an aromatic compound and hydrogen under hydroalkylation reaction conditions with a catalyst system comprising a molecular sieve and at least one metal with hydrogenation activity, wherein said molecular sieve has, in its as-synthesized form and in calcined form, an X-ray diffraction pattern including peaks having a d-spacing maximum in the range of 14.17 to 12.57 Angstroms, a d-spacing maximum in the range of 12.1 to 12.56 Angstroms.