Modified Zeolite Catalyst Mesoporosity Coking Resistance
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Solution Overview
Problem
Zeolites with one-dimensional micropore structures, such as ZSM-12 and TON types, are prone to deactivation by coking mechanisms due to their needle-like morphology, which blocks the internal micropore structure, limiting their effectiveness in hydrocarbon and alcohol conversion processes.
Innovation Solution
Introducing mesoporosity into the zeolite crystallites by treating them with an alkaline solution, which increases access to the interior and enhances resistance to deactivation, characterized by a pore volume range of 0.09 to 0.25 cc/g measured by nitrogen adsorption at 77° K, and modifying the crystallite morphology to be dimensionally isotropic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zeolites with one-dimensional micropore structure are used as catalysts, then selectivity for oligomerization is improved, but catalyst deactivation by coking occurs rapidly
Solution Approach 1:
The patent introduces mesoporosity (30-70 nm pores) into the zeolite crystallites, adding a third dimension of porosity to the existing micropore structure. This hierarchical pore system allows reactants and products to access the internal micropores through larger mesopores, reducing diffusion limitations and preventing coking blockage while maintaining the shape-selective oligomerization function of the original micropores.
2Ease of operation
If alkaline treatment is applied to introduce mesoporosity, then access to crystallite interior is improved, but structural integrity may be compromised
Solution Approach 1:
The patent carefully controls the alkaline treatment parameters (concentration, temperature, time) to achieve the desired mesoporosity without excessive structural damage. By optimizing these parameters, the treatment creates beneficial mesopores while preserving the crystalline zeolite framework and its catalytic properties.
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 modified zeolites exhibit improved resistance to deactivation and increased selectivity to higher hydrocarbons, maintaining high activity over extended periods at elevated temperatures and pressures, with enhanced access to the interior of the crystallites.
Implementation Method 1
treating them with an alkaline solution, which increases access to the interior and enhances resistance to deactivation
Implementation Method 2
as measured by nitrogen adsorption at 77° K and calculated by the BJH method
Data Source
AI summary
A modified zeolite catalyst derived from a zeolite of a structural type which consists of a one-dimensional micropore structure of channels made from rings containing between 8 and 12 silicon/aluminum atoms is disclosed. It consists substantially of a plurality of crystallites having additional mesoporosity whose volume is in the range 0.09 to 0.25 cc/g as mentioned by nitrogen adsorption at 77° K and calculated by the BJH method. The mesoporosity may be introduced into the crystallites by e.g. treatment with aqueous sodium hydroxide at a pH at 25° C. in excess of 8 for an extended period at elevated temperature. The catalyst shows improved resistance to catalyst deactivation and greater selectivity to higher hydrocarbons when used to e.g. oligomerize light alkenes e.g. propene or the butenes.