FCC Catalyst Pore Structure Control via Water-Soluble Porogens
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Solution Overview
Problem
Current fluid catalytic cracking (FCC) catalysts face challenges in accommodating high molecular weight hydrocarbons due to insufficient pore volume distribution, particularly in the size range necessary for cracking, which affects catalyst activity and selectivity, and existing methods for modifying porosity are not effective in achieving optimal pore distribution for heavy hydrocarbon cracking.
Innovation Solution
The use of water-soluble porogenic agents, such as volatile anions and cations, and organic compounds like urea and carbamates, is introduced into the zeolitic catalyst composition to enhance mesoporosity in the 10-1000 Å range, allowing for controlled pore distribution and accessibility without leaving residues, and can be added at various stages of catalyst preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If micropores provided by zeolite Y are used for cracking reactions, then catalyst activity is improved, but high molecular weight hydrocarbon diffusion is restricted due to insufficient pore size
Solution Approach 1:
The patent segments the pore structure into two distinct size ranges: micropores (from zeolite Y) for catalytic activity and mesopores (0.5-10 μm) for mass transport. This segmentation allows each pore type to fulfill its specific function - zeolite micropores provide acidic sites for cracking while larger mesopores enable diffusion of high molecular weight hydrocarbons.
Solution Approach 2:
The patent implements a nested pore structure where mesopores are embedded within the silica-alumina matrix containing zeolite Y crystallites. The mesoporous network is nested inside the catalyst particle, creating a hierarchical structure that allows molecules to access zeolite micropores through the mesoporous pathways.
2Ease of operation
If pore distribution is modified to accommodate high molecular weight hydrocarbons, then accessibility is improved, but catalyst selectivity for desirable products may be compromised
Solution Approach 1:
The patent applies local quality by creating different pore size regions within the catalyst particle. The outer regions contain larger mesopores for mass transport, while the inner regions contain zeolite Y micropores for selective catalysis. This spatial differentiation of pore sizes allows simultaneous optimization of accessibility and selectivity in different locations within the catalyst particle.
3Manufacturing precision
If conventional porosity modification methods are applied to inorganic oxide mixtures, then pore structure change is attempted, but effectiveness is reduced due to material complexity
Solution Approach 1:
The patent introduces water-soluble porogenic agents as intermediaries during catalyst preparation. These agents (such as sugars, starches, or synthetic polymers) are mixed with the inorganic oxide suspension, form a temporary porous template during drying, and are subsequently removed by calcination. This intermediary approach enables precise pore structure control without directly manipulating the complex inorganic oxide mixture.
4Manufacturing precision
If porogenic agents are added to increase mesoporosity, then pore volume distribution is improved, but residual chemicals may remain requiring treatment
Solution Approach 1:
The patent employs biodegradable or water-soluble porogenic agents that can be completely removed from the catalyst through washing with water or standard calcination procedures. These agents are designed to be discarded during the catalyst activation process, leaving no harmful residues in the final product. Examples include sugars, starches, or other organic compounds that decompose cleanly at catalyst preparation temperatures.
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
This approach results in catalysts with improved porosity and activity, increased accessibility, and enhanced conversion rates of high molecular weight hydrocarbons, leading to higher yields of desirable products and reduced coke production, while maintaining mechanical strength and attrition resistance.
Implementation Method 1
water-soluble chemicals are used, mixed with the catalyst precursor suspension which, when subjected to process conditions for the production of cracking catalysts are decomposed into volatile chemicals, leaving no residues that would require treatment to be removed from the catalyst
Implementation Method 2
The use of water-soluble porogenic agents, such as volatile anions and cations, and organic compounds like urea and carbamates, is introduced into the zeolitic catalyst composition to enhance mesoporosity in the 10-1000 Å range
Data Source
AI summary
The present invention relates to a process for preparing fluid catalytic cracking (FCC) catalysts having porosity and accessibility controlled by the activity of water-soluble porogens. The catalyst produced can be used as an additive for fluid cracking, as additives for SOx and NOx reduction, as a combustion promoter and reduction of sulfur in cracked naphtha. It can also be used in hydrocracking, as a support for hydrotreating catalysts, catalytic pyrolysis of post-consumer polymers (rubber tires, plastic films, and so on) and pyrolysis of biomass.