Rare Earth Modified ZSM-5 FCC Additive for LPG Yield
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Solution Overview
Problem
Current FCC processes face challenges in maximizing medium-distillate production while maintaining LPG and propene yield, as high silica-alumina ratio zeolite additives like ZSM-5 reduce LCO yield and increase aromatics at low severity operations, contrary to the desired outcome.
Innovation Solution
A method involving the precipitation of rare earths onto ZSM-5 zeolite to partially block pores, preventing molecular cracking in the LCO range while maintaining activity for smaller molecules, thus enhancing LPG and propene production at low reaction temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ZSM-5 additive is used in low-severity FCC operations, then LPG and propene production is increased, but LCO yield is reduced and aromaticity increases
Solution Approach 1:
The patent applies local quality by modifying the ZSM-5 additive to have non-uniform pore blockage - rare earth metals are deposited to partially block only the smaller pores while leaving larger pores open. This creates different functional zones within the same catalyst structure, allowing selective cracking of light hydrocarbons (improving LPG/propene) while preserving LCO molecules with different dimensional characteristics.
Solution Approach 2:
The patent changes the physical-chemical parameters of the ZSM-5 additive by introducing rare earth metal deposits that modify pore size distribution and acidity. This parameter modification allows the catalyst to maintain high activity for light hydrocarbon cracking while reducing excessive cracking of LCO, thereby simultaneously improving LPG/propene production and preserving LCO yield.
2Quantity of substance
If reaction temperature is reduced to maximize LCO yield, then medium-distillate production increases, but LPG and propene production decreases
Solution Approach 1:
The patent changes the catalyst's active site distribution and pore characteristics through rare earth metal deposition, enabling the system to maintain high cracking activity for light hydrocarbons at lower temperatures without excessive LCO cracking. This parameter modification allows decoupling of temperature effects on different product ranges.
3Productivity
If catalyst activity is increased to maximize gasoline and LPG production, then light hydrocarbon yield increases, but LCO aromaticity increases and quality deteriorates
Solution Approach 1:
The patent creates local quality differences within the catalyst by selectively depositing rare earth metals in pores of specific sizes. This results in different functional regions: some pores remain highly active for light hydrocarbon cracking (improving LPG yield) while other regions with modified pore structures reduce aromatic formation in LCO, thereby improving LCO quality.
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 additive effectively minimizes LCO cracking and maintains LPG and propene yield, optimizing medium-distillate production and gasoline octane in low-severity FCC operations.
Implementation Method 1
a method involving the precipitation of rare earths onto ZSM-5 zeolite to partially block pores
Implementation Method 2
maintaining activity for smaller molecules, thus enhancing LPG and propene production
Data Source
AI summary
A process for the preparation and modification of additives, with a zeolite base and a high silica alumina ratio (SAR) like the ZSM-5, to increase the yield of propene and LPG in low severity FCC operations, that seeks to maximize the production of medium-distillates with low aromaticity and to minimize molecular cracking in the LCO range. The additives involved guarantee an increase in light olefin yields without altering the yield or the quality of the LCO produced. The innovative process includes surprising actions from rare earths (RE) on the active sites of zeolite, that at once partially block their pores and, in this way, make molecular cracking in the medium-distillate range difficult, which preferably occur at low reaction temperatures and keeps the remaining sites quite active. These sites are sufficiently active to crack smaller molecules in the gasoline range, guaranteeing an overall increase in light olefins and allowing the additive involved to be used industrially in operations to maximize medium-distillates in an FCC unit. This new additive may be obtained by modifying any commercial ZSM-5 zeolite additive.