EU-1 Zeolite on Amorphous Core for C8 Isomerization
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Solution Overview
Problem
The existing methods for preparing EU-1 zeolite catalysts require shaping with a binder, which is a delicate process, and the direct deposition of zeolite crystals on a support during synthesis is more attractive, allowing for the preservation of intercrystalline porosity and eliminating the need for a binder.
Innovation Solution
A process involving the impregnation of a silicon oxide and aluminum oxide solid with a quaternary diammonium cation, followed by hydrothermal treatment in an autoclave with controlled water vapor, leading to the formation of EU-1 zeolite crystals dispersed on the surface of an amorphous core, which maintains the core's porosity and avoids direct contact with water to prevent surface gelation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If EU-1 zeolite is prepared by standard hydrothermal synthesis, then zeolite crystals form, but the product requires shaping with a binder which complicates the process and reduces porosity
Solution Approach 1:
The catalyst is segmented into two distinct parts: an amorphous porous core and surface-dispersed EU-1 zeolite crystals. This segmentation allows the core to maintain its porosity and structural integrity while the zeolite crystals provide catalytic activity, eliminating the need for binder-based shaping
Solution Approach 2:
The amorphous porous structure is prepared in advance with controlled porosity and surface properties before zeolite crystallization. This preliminary preparation ensures that when zeolite crystals form during hydrothermal treatment, they deposit only on the surface without requiring subsequent shaping operations
2Ease of manufacture
If zeolite crystals are deposited on support during synthesis, then binder is eliminated, but direct contact with water causes surface gelation which reduces porosity
Solution Approach 1:
The amorphous core possesses specific local properties: controlled porosity, appropriate surface area, and chemical composition that prevents excessive gelation. These localized qualities allow the core to serve as a stable support that enables zeolite deposition without suffering from the harmful gelation effect
Solution Approach 2:
The amorphous core is pre-prepared with properties that counteract the gelation tendency. By controlling the core's composition and porosity before hydrothermal treatment, the harmful gelation effect is preemptively mitigated, allowing water contact during synthesis without significant porosity loss
3Productivity
If complete conversion to EU-1 zeolite is achieved, then catalyst activity is maximized, but the amorphous core structure is lost and porosity is reduced
Solution Approach 1:
Instead of complete conversion to zeolite, the synthesis is controlled to achieve partial conversion (5-20% by weight). This partial action is sufficient to provide catalytic activity while preserving the amorphous core structure and its porosity, achieving an optimal balance between activity and pore accessibility
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 method results in a porous composite material with improved catalytic performance for isomerizing aromatic compounds, specifically enhancing xylene yield, as the EU-1 zeolite crystals are only present on the external surface, maintaining the core's amorphous nature and preserving its porosity.
Implementation Method 1
impregnation of a solid comprising at least one silicon oxide and at least one aluminum oxide with at least one aqueous solution comprising at least one quaternary diammonium cation
Implementation Method 2
A crystallization phenomenon first occurs on the external surface of the solid before progressing, depending on the synthesis time, towards the interior of the solid
Implementation Method 3
transformation into EU-1 zeolite of an amorphous and porous structure composed of one or more inorganic oxide(s). This transformation is carried out during a hydrothermal treatment
Data Source
AI summary
A process for preparing a porous composite material consisting of an amorphous core based on at least one silicon oxide on which EU-1 zeolite crystals are dispersed is described, said process comprising 1) impregnating a solid comprising a silicon oxide and an aluminum oxide with an aqueous solution comprising a hexamethonium cation, 2) hydrothermal treatment, carried out in an autoclave of volume V (ml) under steam and at a temperature T between 120 and 220°C, of said solid obtained from step 1), the quantity of water previously introduced into said autoclave being strictly greater than a volumetric quantity equal to V*[23.48*10-10*T3-48*10-8*T2+5*10-5*T-0.002] and less than or equal to 0.25*V, and is such that said solid is not in direct contact with it, 3) drying and then calcination of the solid from step 2).The preparation of a catalyst from said material for use in the isomerization of C8 aromatics is also described.