C8 Aromatics Isomerization Catalyst with Low Hydrogen Co-Feed
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Solution Overview
Problem
Current processes for isomerizing C8 aromatics, such as xylene isomerization, face challenges in achieving high para-xylene yield while minimizing aromatic losses and reducing processing costs, particularly due to high hydrogen requirements and associated cyclic C8 losses.
Innovation Solution
A process utilizing a zeolitic aluminosilicate catalyst with specific crystal-size characteristics, a metal component, and an inorganic oxide binder, operating at controlled temperature, pressure, and hydrogen ratios on a once-through basis to isomerize C8 aromatics, thereby increasing para-xylene concentration and reducing aromatic saturation and processing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the isomerization process operates close to equilibrium to maximize para-xylene yield, then the para-xylene yield is improved, but the cyclic C8 loss increases due to side reactions
Solution Approach 1:
The patent changes the chemical environment by introducing a specific co-feed composition (hydrogen, carbon dioxide, and water in controlled ratios) to modify the reaction conditions. This alters the equilibrium and reaction pathways to favor para-xylene formation while suppressing cyclic C8 side reactions, resolving the contradiction between high yield and low loss.
Solution Approach 2:
The patent uses carbon dioxide and water as intermediary substances that interact with the catalyst and reactants. These intermediaries help control the reaction selectivity, enabling the system to achieve high para-xylene yield while minimizing unwanted cyclic C8 formation through modified reaction mechanisms.
2Productivity
If a substantial quantity of hydrogen is circulated in the isomerization process, then ethylbenzene conversion is improved, but the investment and operating cost increases due to recycle-gas compressor and hydrogen purging
Solution Approach 1:
The patent extracts the essential function of hydrogen (aiding ethylbenzene conversion) while removing the harmful aspect (need for costly compression and purging). By using a co-feed system with hydrogen at low partial pressure combined with carbon dioxide and water, the process achieves ethylbenzene conversion without requiring substantial hydrogen circulation, thereby eliminating compression costs.
Solution Approach 2:
The patent replaces expensive recycled hydrogen with a cheaper co-feed mixture where hydrogen is used in small amounts and not recycled. The carbon dioxide and water serve as bulk carriers that are less costly to handle, allowing the process to maintain ethylbenzene conversion activity without the infrastructure costs of hydrogen recycling.
3Productivity
If high hydrogen partial pressure is used in the isomerization process, then ethylbenzene conversion is improved, but aromatic saturation and loss increases
Solution Approach 1:
The patent changes the partial pressure parameters by introducing carbon dioxide and water to dilute the hydrogen concentration. This maintains the total pressure needed for ethylbenzene conversion while keeping hydrogen partial pressure low enough to prevent aromatic saturation, thus resolving the contradiction between conversion and loss.
Solution Approach 2:
The patent creates different local chemical environments within the reactor by using a multi-component co-feed. Hydrogen is present at low concentrations to provide necessary catalytic activity for ethylbenzene conversion, while carbon dioxide and water dominate the local environment to prevent excessive hydrogenation and aromatic saturation.
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 effectively increases the proportion of para-xylene in the product while minimizing aromatic losses and lowering processing costs by optimizing catalyst composition and operating conditions, resulting in improved efficiency and cost savings.
Implementation Method 1
contacting the feedstock with a catalyst comprising a zeolitic aluminosilicate having a median particle size greater than 1 micron, a metal component, and an inorganic oxide binder in an isomerization zone
Implementation Method 2
Hydrogen generally is present in the isomerization process reactants to aid in the reaction and maintain catalyst stability
Implementation Method 3
conversion to and reconversion from naphthenes in the presence of a solid acid catalyst with a hydrogenation-dehydrogenation function
Data Source
AI summary
This invention is drawn to a process for isomerizing a non-equilibrium mixture of xylenes and ethylbenzene using a catalyst comprising a zeolite having specific particle-size characteristics, a platinum-group metal and a silica binder. A relatively minimal amount of hydrogen is supplied to the process on a once-through basis, resulting in low saturation of aromatics while achieving effective xylene isomerization with reduced processing costs.