Single-Step Alkylated Aromatics Production Using CO2 and Methylcyclohexane
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Solution Overview
Problem
Current methods for producing alkylated aromatics using CO2 as an alkylation reagent require energy-intensive hydrogenation processes with molecular hydrogen, leading to inefficient greenhouse gas mitigation and low selectivity for alkylated products, while existing processes using CO2 and methylcyclohexane as hydrogen donors have negligible alkylation selectivity.
Innovation Solution
A single-step catalytic process utilizing metal functionalized zeolite-based catalysts to dehydrogenate methylcyclohexane, reduce CO2 to form active alkylating species, and alkylate toluene, achieving significant alkylation of aromatics using CO2 or species derived from CO2 as the alkylation reagent, with methylcyclohexane serving as both a hydrogen donor and source of toluene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If molecular hydrogen is used for CO2 hydrogenation to form alkylating species, then the alkylation reaction can proceed, but the process requires energy-intensive enhanced pressure and temperature conditions and consumes valuable molecular H2
Solution Approach 1:
The patent changes the physical state of the hydrogen donor from gaseous molecular hydrogen to liquid methylcyclohexane, enabling the reaction to proceed under milder conditions (323-423 K, 1-10 atm) compared to conventional high-pressure hydrogenation processes
Solution Approach 2:
The patent introduces methylcyclohexane as an intermediary hydrogen donor that releases hydrogen in situ through dehydrogenation, mediating between the CO2 hydrogenation and toluene alkylation steps without requiring external molecular hydrogen supply
2Productivity
If conventional alkylation reagents like methanol, dimethylether, or olefins are used, then the alkylation of aromatics can be achieved, but the process does not utilize CO2 as a carbon source and is not environmentally benign
Solution Approach 1:
The patent converts CO2, a harmful greenhouse gas, into a beneficial alkylation reagent through in situ hydrogenation to form methylating species, thereby utilizing waste CO2 for productive chemical synthesis and reducing greenhouse gas emissions
Solution Approach 2:
The patent makes methylcyclohexane serve multiple functions: as a hydrogen donor for CO2 hydrogenation and as an in situ source of toluene through dehydrogenation, eliminating the need for separate reagent and substrate supply streams
3Use of energy by moving object
If methylcyclohexane is used as a hydrogen donor for CO2 hydrogenation, then the process conditions become milder and net GHG mitigation improves, but the alkylation selectivity remains negligible
Solution Approach 1:
The patent employs a composite catalytic system combining metal nanoparticles (Pt, Pd, Ni, or Cu) with zeolite support (HZSM-5, Hβ, or HY), where the metal component facilitates CO2 hydrogenation and the zeolite provides acid sites for toluene alkylation, achieving synergistic enhancement of alkylation selectivity
Solution Approach 2:
The patent creates different functional zones within the catalyst structure, with metal sites localized for hydrogenation reactions and zeolite acid sites localized for alkylation reactions, enabling selective product formation through spatial differentiation of catalytic functions
4Ease of manufacture
If the dehydrogenated product of the H2-donor is not utilized in-situ, then the H2-donor can serve its primary function, but the process becomes less atom-economical and creates additional separation requirements
Solution Approach 1:
The patent merges the dehydrogenation of methylcyclohexane with the alkylation of toluene in a single integrated process, where the toluene generated in situ immediately participates in the alkylation reaction, combining multiple transformations into one unified reaction system
Solution Approach 2:
The system achieves self-service by generating its own substrate (toluene) from the hydrogen donor (methylcyclohexane) through dehydrogenation, eliminating the need for external toluene supply and improving overall process efficiency
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 process achieves a yield of 19.5-21 wt% alkylated aromatics, with 9-9.5 wt% mix xylenes, enhancing atom economy and reducing greenhouse gas emissions by utilizing CO2 as a carbon source and alkylation reagent, and providing a more efficient and environmentally benign route for alkylated aromatic production.
Implementation Method 1
dehydrogenation of methylcyclohexane to produce toluene and hydrogen
Implementation Method 2
hydrogenation of CO2 to form an active alkylating species
Implementation Method 3
alkylation of toluene using CO2 and molecular H2
Data Source
AI summary
Utilization of CO2 for the alkylation of aromatic hydrocarbons is one of the green and sustainable routes for the production of valuable alkylated aromatics like xylenes. Aspects of the present invention deal with the development of single-step catalytic process for the production of alkylated aromatics using CO2 as a carbon source and alkylation reagent and methylcyclohexane as a hydrogen atom donor as well as source of toluene. In presence of the metal functionalized zeolite catalyst, methylcyclohexane undergoes dehydrogenation to produce toluene and hydrogen; hydrogen reacts with CO2 to form active alkylating species which triggers the alkylation of toluene. Additionally, a novel process is disclosed for the production of xylene-rich alkylated aromatics from methylcyclohexane and CO2 using single multi-functional catalyst possessing dehydrogenation, hydrogenation and acid functionalities.