Modified Y Zeolite Catalyst for FCC Coke Reduction
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Solution Overview
Problem
The catalytic cracking process faces challenges with increasing coke yield and decreasing heavy oil conversion due to the influence of inferior raw heavy oil, leading to inefficient petroleum resource utilization, as existing catalysts struggle with maintaining stability and selectivity over time.
Innovation Solution
A modified Y-type zeolite with a specific unit cell size, phosphorus, and rare earth content is developed, combined with a three-exchange-and-three-calcination process, to create a catalytic cracking catalyst that reduces coke yield and enhances heavy oil utilization by improving the zeolite's stability and activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the conversion is increased to achieve high yield of light oils and LPG, then the productivity is improved, but the coke yield is remarkably increased leading to waste of petroleum resource
Solution Approach 1:
The patent modifies the zeolite's structural parameters by controlling the unit cell size to 2.428-2.438 nm through specific synthesis conditions and ion exchange processes. This parameter change optimizes the balance between cracking activity and hydrogen transfer reaction, enabling high conversion while reducing coke formation
Solution Approach 2:
The patent creates a composite catalyst system combining modified Y-type zeolite with specific matrix materials and promoters. The zeolite is modified with controlled aluminum content and pore structure, creating a composite material that synergistically improves conversion while suppressing excessive hydrogen transfer reactions that lead to coke
2Productivity
If the acid site density of the zeolite is increased to improve cracking activity, then the productivity is improved, but the hydrogen transfer reaction becomes intenser leading to higher coke yield
Solution Approach 1:
The patent creates local quality differences within the zeolite structure by introducing specific aluminum distribution patterns and pore size variations. The unit cell size is precisely controlled to create optimal local environments for cracking while minimizing sites favorable for hydrogen transfer, achieving selective activity enhancement
Solution Approach 2:
The patent changes the zeolite's structural parameters including unit cell size (2.428-2.438 nm), aluminum content, and Si/Al ratio to optimize the balance between cracking activity and hydrogen transfer. These parameter changes modify the acid site characteristics to favor cracking over hydrogen transfer
3Productivity
If the fresh catalyst with larger unit cell size is used to maintain high cracking activity, then the productivity is improved, but the coke selectivity increases and heavy oil utilization decreases
Solution Approach 1:
The patent performs preliminary modification of the zeolite during catalyst preparation, controlling the unit cell size to the optimal range of 2.428-2.438 nm before the catalyst enters service. This preliminary action ensures the catalyst starts with optimized structural parameters that balance activity and selectivity, avoiding the need for larger unit cells that would increase coke formation
4Object-generated harmful factors
If the spent catalyst with lower unit cell size is used to reduce coke selectivity, then the coke yield is reduced, but the cracking activity decreases and heavy oil utilization is unfavorable
Solution Approach 1:
The patent performs preliminary modification during catalyst synthesis to achieve the optimal unit cell size range of 2.428-2.438 nm, which is smaller than conventional catalysts but larger than fully aged spent catalysts. This preliminary sizing ensures the catalyst maintains high cracking activity while having reduced coke selectivity compared to conventional fresh catalysts
5Object-generated harmful factors
If the zeolite is subjected to hydrothermal aging to reduce coke selectivity, then the coke yield is reduced, but the structure collapses and cracking activity decreases
Solution Approach 1:
The patent performs preliminary structural stabilization during catalyst preparation by controlling synthesis conditions and ion exchange to achieve the optimal unit cell size of 2.428-2.438 nm with enhanced hydrothermal stability. This preliminary stabilization prevents structure collapse during aging while maintaining reduced coke selectivity, eliminating the need for aggressive hydrothermal aging treatments
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 catalyst achieves stable activity and reduced coke selectivity, leading to improved heavy oil utilization and increased yields of diesel oil, gasoline, and lower olefins, while maintaining crystallinity and hydrothermal stability.
Implementation Method 1
Coke is composed of various hydrogen-deficient compounds having different hydrogen deficiency degrees. It is a product of the hydrogen transfer reaction.
Implementation Method 2
the zeolite is subjected to skeleton dealumination and structural collapse under the hydrothermal condition
Implementation Method 3
maintaining crystallinity and hydrothermal stability
Data Source
AI summary
The present invention discloses a catalytic cracking catalyst and a preparation process therefor. The catalytic cracking catalyst comprises a cracking active component, 10 wt %-70 wt % of a clay on the dry basis, and 10 wt %-40 wt % of an inorganic oxide binder (as oxide), relative to the weight of the catalytic cracking catalyst, wherein said cracking active component contains, relative to the weight of the catalytic cracking catalyst, 10 wt %-50 wt % of a modified Y-type zeolite on the dry basis and 0-40 wt % of other zeolite on the dry basis, wherein said modified Y-type zeolite is characterized by having a unit cell size of 2.420-2.440 nm; as percent by weight of the modified Y-type zeolite, a phosphorus content of 0.05-6%, a RE2O3 content of 0.03-10%, and an alumina content of less than 22%; and a specific hydroxy nest concentration of less than 0.35 mmol/g and more than 0.05 mmol/g.