MeAPO Molecular Sieve Blends for Olefin Conversion Stability
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Solution Overview
Problem
Small pore zeolitic catalysts used in the conversion of oxygenates to olefins tend to deactivate rapidly, leading to a suboptimal C3/C2 ratio and reduced catalyst stability, which limits the efficiency and duration of the XTO process.
Innovation Solution
A mixture comprising 0.01 to 28% of medium or large pore crystalline silicoaluminate, silicoaluminophosphate, or silicoaluminate mesoporous molecular sieves blended with small pore MeAPO molecular sieves, enhancing the C3/C2 ratio and stability by facilitating the in-situ formation of aromatics and reducing coke selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If small pore MeAPO molecular sieves are used as catalysts in XTO process, then the conversion of oxygenates to olefins can be achieved, but the catalyst deactivates rapidly leading to reduced stability and suboptimal C3/C2 ratio
Solution Approach 1:
The patent combines small pore MeAPO molecular sieves (0.01-28 wt%) with medium or large pore crystalline silicoaluminate, silicoaluminophosphate, or silicoaluminate mesoporous molecular sieves to create a blended catalyst system. This merging of different pore size catalysts allows the small pore MeAPO to maintain its olefin selectivity while the medium/large pore components provide enhanced stability and reduced deactivation, thereby resolving the contradiction between achieving conversion and maintaining long-term catalyst stability.
Solution Approach 2:
The invention creates a composite catalyst material by blending MeAPO with other molecular sieves having different pore structures. This composite approach leverages the shape selectivity of small pore MeAPO for olefin production while incorporating the structural stability and coke resistance of medium/large pore molecular sieves, thus extending catalyst on-stream time and maintaining reliability throughout extended operation periods.
2Productivity
If small pore MeAPO molecular sieves are used, then olefin conversion can proceed, but coke formation increases leading to catalyst deactivation
Solution Approach 1:
By merging small pore MeAPO with medium/large pore molecular sieves, the catalyst system maintains high olefin production efficiency through the shape-selective pores of MeAPO while the medium/large pore components provide pathways that reduce coke formation by facilitating alternative reaction pathways and improving mass transfer, thus resolving the contradiction between productivity and harmful coke generation.
3Quantity of substance
If small pore MeAPO molecular sieves are used, then the XTO process can operate, but the C3/C2 ratio becomes suboptimal
Solution Approach 1:
The blended catalyst system merges the propylene-selective properties of small pore MeAPO with the ethylene-modulating effects of medium/large pore molecular sieves. This combination allows simultaneous optimization of both C3 (propylene) and C2 (ethylene) production, achieving an optimal C3/C2 ratio while maintaining high overall olefin production quantities.
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 blended catalysts exhibit increased stability, allowing for higher flow rates, extended on-stream time, and reduced coke formation, thereby improving the C3/C2 ratio and overall efficiency of the XTO process.
Implementation Method 1
A mixture comprising 0.01 to 28% of medium or large pore crystalline silicoaluminate, silicoaluminophosphate, or silicoaluminate mesoporous molecular sieves blended with small pore MeAPO molecular sieves, enhancing the C3/C2 ratio and stability by facilitating the in-situ formation of aromatics
Implementation Method 2
The blended catalysts exhibit increased stability, allowing for higher flow rates, extended on-stream time, and reduced coke formation, thereby improving the C3/C2 ratio and overall efficiency of the XTO process
Data Source
AI summary
The present invention is a mixture comprising by weight 0.01 to 28% of at least one medium or large pore crystalline silicoaluminate, silicoaluminophosphate materials or silicoaluminate mesoporous molecular sieves (co-catalyst) (A) for respectively 99.99 to 72% of at least a MeAPO molecular sieve.Preferably the proportion of (A) is 1 to 15% for respectively 99 to 85% of MeAPO molecular sieves.MeAPO molecular sieves having CHA (SAPO-34) or AEI (SAPO-18) structure or mixture thereof are the most preferable. Si is the most desirable metal in MeAPO.The present invention also relates to catalysts consisting of the above mixture or comprising the above mixture.The present invention also relates to a process (hereunder referred as “XTO process”) for making an olefin product from an oxygen-containing, halogenide-containing or sulphur-containing organic feedstock wherein said oxygen-containing, halogenide-containing or sulphur-containing organic feedstock is contacted with the above catalyst (in the XTO reactor) under conditions effective to convert the oxygen-containing, halogenide-containing or sulphur-containing organic feedstock to olefin products (the XTO reactor effluent).The present invention also relates to a process (hereunder referred as “combined XTO and OCP process”) to make light olefins from an oxygen-containing, halogenide-containing or sulphur-containing organic feedstock comprising:contacting said oxygen-containing, halogenide-containing or sulphur-containing organic feedstock in the XTO reactor with the above catalyst at conditions effective to convert at least a portion of the feedstock to form an XTO reactor effluent comprising light olefins and a heavy hydrocarbon fraction;separating said light olefins from said heavy hydrocarbon fraction;contacting said heavy hydrocarbon fraction in the OCP reactor at conditions effective to convert at least a portion of said heavy hydrocarbon fraction to light olefins.