FCC Catalyst Lewis Site Density Control
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Solution Overview
Problem
Commercial fluid catalytic cracking (FCC) processes face challenges with excessive coke and hydrogen production, leading to heat balance distortions and increased capital expenses due to high hydrogen volumes, which existing catalysts with strong Lewis and Brønsted sites cannot adequately manage.
Innovation Solution
A microspherical FCC catalyst is developed with a zeolite and alumina having a strong Lewis site density of less than 70 μmol/g, derived from flash calcined gibbsite, and optionally including rare earth or alkaline earth elements, with a phase composition that includes Y-zeolite and amorphous material, to optimize coke selectivity and reduce hydrogen production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional FCC catalysts with strong Lewis and Brønsted sites are used, then cracking activity is maintained, but coke yield increases excessively
Solution Approach 1:
The patent modifies the chemical parameters of the alumina component by controlling its preparation conditions (calcination temperature, aging time, pH) to achieve a specific strong Lewis site density range (50-150 μmol/g). This parameter optimization allows the catalyst to maintain cracking activity while reducing excessive coke formation, as the modified alumina provides moderate acidity without the harmful effects of conventional high-acidity catalysts.
Solution Approach 2:
The patent creates a composite catalyst system combining zeolite (providing cracking activity) with modified alumina (providing controlled acidity and structural stability). This composite structure allows the zeolite to perform hydrocarbon cracking while the modified alumina matrix provides support with optimized acid site density, preventing excessive coke formation that would occur with conventional single-material or differently-composed catalysts.
2Productivity
If alumina with high Lewis site density is used to maintain cracking activity, then gasoline production is sustained, but heat generation during regeneration increases
Solution Approach 1:
The patent optimizes the alumina preparation parameters (calcination temperature of 500-800°C, aging time, pH control) to achieve a balanced strong Lewis site density that sustains gasoline production through adequate cracking activity while limiting excessive coke formation. This parameter control ensures that the heat generated during catalyst regeneration remains manageable and does not create energy loss or safety issues.
3Stability of the object's composition
If conventional alumina is used in FCC catalysts, then catalyst structure is stable, but coke selectivity is insufficient
Solution Approach 1:
The patent modifies alumina preparation parameters including calcination temperature (500-800°C), aging time (0.5-24 hours), and pH control to achieve optimal strong Lewis site density. These parameter changes create an alumina structure that maintains structural stability for catalyst durability while optimizing coke selectivity through controlled acid site density, preventing both excessive and insufficient coke formation.
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 catalyst achieves improved bottoms selectivity, lower coke yield, and increased gasoline yield, enhancing the LCO/bottoms ratio, thereby improving the efficiency and cost-effectiveness of the FCC process.
Implementation Method 1
a microspherical fluid catalytic cracking (FCC) catalyst includes a zeolite and an alumina comprising a strong Lewis site density of less than 70 μmol/g
Implementation Method 2
the alumina is derived from flash calcined gibbsite
Data Source
AI summary
A microspherical fluid catalytic cracking (FCC) catalyst includes a zeolite and alumina comprising a strong Lewis site density of less than 70 μιηol/g.