Large-Pore Zeolitic Catalysts for Heavy Hydrocarbon Cracking
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Solution Overview
Problem
Existing hydrocracking catalysts with zeolites have pores that are too small to effectively convert larger hydrocarbons, limiting the conversion of heavier vacuum gasoil distillate-range hydrocarbons into valuable fuel distillate-range products.
Innovation Solution
The use of large pore zeolitic catalysts with pores greater than 8 Å, defined by rings of more than twelve tetrahedral atoms, to convert hydrocarbon feedstocks into fuel distillate-range products by catalytic cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional zeolite catalysts with small pores (≤1 nm) are used, then high catalytic activity is achieved, but large hydrocarbon molecules cannot effectively diffuse into the pores for conversion
Solution Approach 1:
The patent applies parameter changes by modifying the pore size parameter of zeolite catalysts from conventional ≤1 nm to >1 nm (specifically 1-5 nm), enabling large hydrocarbon molecules to diffuse into the pores while maintaining high catalytic activity. This is achieved through selecting specific zeolite structures (MOR, FAU, BEA, OFF, TON frameworks) with inherently larger pore dimensions, directly resolving the contradiction between pore size and conversion efficiency of large molecules.
2Length of moving object
If amorphous silica-alumina with large pores (>10 nm) is used, then access for large molecules is improved, but catalytic activity is significantly reduced
Solution Approach 1:
The patent applies local quality by creating a hierarchical pore structure with different pore sizes serving different functions: larger pores (1-5 nm) provide access for large hydrocarbon molecules, while smaller active sites within these pores maintain high catalytic activity. This is achieved through selecting zeolite frameworks with specific local structural characteristics that concentrate acid sites in favorable locations, thus resolving the contradiction between pore size and catalytic activity.
Solution Approach 2:
The patent applies composite materials by combining zeolite crystals with specific pore structures (MOR, FAU, BEA, OFF, TON frameworks) that inherently possess both the desired pore size (>1 nm) and high catalytic activity. These zeolite-based composite catalysts integrate the benefits of ordered porous structures with high surface area and active site density, overcoming the limitations of both conventional small-pore zeolites and amorphous silica-alumina.
3Productivity
If zeolite pore size is increased to accommodate large molecules, then conversion of heavy hydrocarbons improves, but mass diffusion efficiency may be reduced
Solution Approach 1:
The patent applies segmentation by dividing the pore structure into hierarchical levels: macro-pores (1-5 nm) for molecule access and meso-pores/channels for efficient mass transport. The segmented pore architecture allows large hydrocarbon molecules to enter through larger pores while maintaining efficient diffusion pathways through interconnected smaller channels, thus resolving the contradiction between accommodating large molecules and maintaining diffusion efficiency.
Solution Approach 2:
The patent applies dimensionality change by utilizing three-dimensional pore networks with multiple transport dimensions. The zeolite frameworks (MOR, FAU, BEA, OFF, TON) possess complex 3D pore systems that provide multiple diffusion pathways, allowing molecules to reach active sites through optimal routes that minimize diffusion time while accommodating large hydrocarbon structures.
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 large pore zeolitic catalysts achieve higher conversion efficiency and stability, producing hydrocarbon product streams with a lower T95 distillation temperature than the feedstock, maximizing the production of valuable distillate fuels and lubricating oils.
Implementation Method 1
Catalytic cracking utilizes a catalyst to facilitate hydrocarbon cracking. A cracking catalyst typically includes a metal function and an acid function.
Implementation Method 2
The selectivity and activity of a zeolitic catalyst are highly dependent on the mass diffusion of the hydrocarbons from the hydrocarbon feed stream into and out of the pores of the zeolite.
Implementation Method 3
Chemically, hydrocracking may be considered a combination of hydrogenation and catalytic cracking where high-boiling hydrocarbons are to lower boiling fractions and olefinic and aromatic hydrocarbons are hydrogenated to generate paraffins and naphthenes.
Data Source
AI summary
A hydrocarbon feed stream, particularly one comprising heavier hydrocarbons, may be converted to valuable products such as motor gasoline and/or lubricating oil by employing one or more large pore zeolitic catalysts, which may be prepared from a precursor zeolite. In some examples, a large pore zeolitic catalyst may be utilized to selectively reduce the endpoint of a hydrocarbon composition.