Modified Y-Type Molecular Sieve for Hydrogenated LCO Cracking
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Solution Overview
Problem
Conventional catalytic cracking catalysts are ineffective in processing hydrogenated light cycle oils (LCOs) due to poor cracking ability and high hydrogen transfer capacity, which limits the production of BTX light aromatics.
Innovation Solution
A modified Y-type molecular sieve with a rare earth content of 4-11% by weight, sodium content of 0.5% or less, zinc content of 0.5-5% by weight, and phosphorus content of 0.05-10% by weight, combined with a specific framework silica-alumina ratio and pore structure, is used to create a catalytic cracking catalyst. This catalyst is prepared through a multi-step process involving ion-exchange, hydrothermal stabilization, gas phase ultra-stabilization, acid treatment, phosphorus modification, and zinc impregnation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional catalytic cracking catalysts are used to process hydrogenated LCOs, then the catalyst structure is simple and easy to manufacture, but the cracking ability is poor and hydrogen transfer capacity is too high, resulting in low BTX production
Solution Approach 1:
The patent uses a composite molecular sieve structure comprising a core Y-type molecular sieve and a shell mesoporous molecular sieve, creating a core-shell composite catalyst. This composite structure combines the advantages of both molecular sieve types: the Y-type core provides cracking activity while the mesoporous shell provides accessibility for large molecules, thereby improving BTX production efficiency without excessive complexity
Solution Approach 2:
The patent creates different functional zones within the catalyst particle: the core region contains Y-type molecular sieve with specific pore structure for cracking reactions, while the shell region contains mesoporous molecular sieve with larger pores for reactant access. This local differentiation of properties optimizes both cracking ability and accessibility, resolving the contradiction between simple structure and high performance
2Ease of operation
If the pore size of Y-type molecular sieve is increased to improve accessibility of polycyclic compounds, then the cracking capability for residual oils improves, but the selectivity for light aromatics production may be affected
Solution Approach 1:
The patent divides the catalyst into two distinct pore structure segments: the Y-type molecular sieve core with small pores (0.74 nm) for shape-selective cracking to light aromatics, and the mesoporous shell with larger pores (2-10 nm) for easy access of polycyclic compounds. This segmentation allows each segment to optimize its function without compromising the other, improving both accessibility and selectivity
3Adaptability or versatility
If hydrogenation is applied to saturate polycyclic aromatics into heavy monocyclic aromatics, then the feedstock becomes more suitable for catalytic cracking, but the hydrogen transfer ability increases making conventional catalysts ineffective
Solution Approach 1:
The patent changes the key parameter of pore size distribution in the catalyst structure. By incorporating mesopores with 2-10 nm diameter in the shell region, the catalyst can accommodate the altered molecular structure of hydrogenated LCOs while maintaining appropriate hydrogen transfer capacity. This parameter change makes the catalyst reliable for processing hydrogenated feedstocks
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 Y-type molecular sieve-based catalyst exhibits higher conversion efficiency of hydrogenated LCOs, lower coke selectivity, and increased yields of BTX-rich gasoline and ethylene/propylene, enhancing the production of light aromatics.
Implementation Method 1
contacting a NaY molecular sieve with a rare earth salt solution for ion-exchange reaction
Implementation Method 2
subjecting the ion-exchanged molecular sieve to a hydrothermal ultra-stabilization treatment
Implementation Method 3
subjecting the hydrothermally ultra-stabilized molecular sieve to a gas phase ultra-stabilization treatment by contacting and reacting with gaseous SiCl4
Implementation Method 4
subjecting the gas phase ultra-stabilized molecular sieve to an acid treatment by contacting with an acid solution
Implementation Method 5
subjecting the acid-treated molecular sieve to phosphorus modification by contacting with a phosphorus compound
Implementation Method 6
impregnating the phosphorus-modified molecular sieve with a zinc salt solution
Data Source
AI summary
A modified Y-type molecular sieve has a rare earth content of about 4-11% by weight on the basis of rare earth oxide, a sodium content of no more than about 0.5 wt % by weight on the basis of sodium oxide, a zinc content of about 0.5-5% by weight on the basis of zinc oxide, a phosphorus content of about 0.05-10% by weight on the basis of phosphorus pentoxide, a framework silica-alumina ratio of about 7-14 calculated on the basis of SiO2/Al2O3 molar ratio, a percentage of non-framework aluminum content to the total aluminum content of no more than about 10%, and a percentage of the pore volume of secondary pores having a pore size of 2-100 nm to the total pore volume of about 20-40%. The modified Y-type molecular sieve has a high crystallinity and a high thermal and hydrothermal stability, and is rich in secondary pores.