Alkali-Treated Zeolite Catalyst for Heavy Feedstock Cracking
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Solution Overview
Problem
Current methods for cracking heavy feedstocks, such as vacuum gas oils and heavy oils from tar sands and shale oils, do not efficiently produce high amounts of lower olefins while minimizing coking and producing gasoline and diesel cuts as co-products.
Innovation Solution
A modified zeolite catalyst is developed by alkaline treatment of zeolites to increase meso-large pore BET surface area, combined with phosphorus and metal compounds, and used in fluid bed catalytic cracking to enhance olefin selectivity and reduce coke formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional zeolite catalysts are used for cracking heavy feedstocks, then the process is simple and well-established, but the yield of lower olefins is low and coking is excessive
Solution Approach 1:
The patent applies parameter changes by treating zeolite catalysts with alkali solutions to modify their chemical composition and physical structure. This treatment changes the Si/Al ratio, creates mesopores, and modifies acid site distribution, thereby transforming the catalyst's cracking behavior to produce higher olefin yields and reduce coking
Solution Approach 2:
The patent uses composite materials by combining modified zeolite catalysts with specific matrix materials and promoters. The composite catalyst system integrates zeolites with controlled pore structures, matrix materials for stability, and metallic promoters for enhanced activity, achieving superior performance in olefin production and coke reduction
2Manufacturing precision
If zeolite pore size is reduced to improve selectivity, then cracking specificity increases, but access to heavy feedstock molecules is limited
Solution Approach 1:
The patent applies segmentation by creating a hierarchical pore structure with multiple size levels. The catalyst possesses both micropores for selective cracking reactions and mesopores for feedstock molecule access, effectively segmenting the pore system to fulfill both selectivity and accessibility requirements
Solution Approach 2:
The patent transitions from a single-dimensional micropore structure to a multi-dimensional hierarchical pore system by introducing mesopores. This dimensional expansion allows simultaneous accommodation of large heavy feedstock molecules and maintenance of selective micropore environments for controlled cracking
3Productivity
If alkali treatment is applied to increase mesopore surface area, then olefin selectivity improves, but catalyst preparation complexity increases
Solution Approach 1:
The patent applies preliminary action by performing alkali treatment on zeolite precursors or crystalline zeolites before final catalyst formulation. This pre-modification establishes the desired mesopore structure and chemical properties early in the catalyst development process, simplifying subsequent steps and improving overall efficiency
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 higher yields of C2-4 olefins, gasoline, and diesel cuts with reduced coke production, making it suitable for cracking heavy feedstocks effectively.
Implementation Method 1
the NaOH-treatment of MFI zeolite brought about the increases in total surface area and external surface area. The increase in the surface areas was due to the formation of the supermicropores having about 1.8 nm in diameter
Implementation Method 2
a catalyst suitable for cracking a hydrocarbon feedstock having a boiling point above 300° C. at a temperature from 500° C. to 800° C. and a pressure from 103.3 kPa to 6.89×10³ kPa to produce more than 15% of C2-4 olefins
Implementation Method 3
impregnating said zeolite with a phosphorus compound to provide from 0.2 to 15 weight % calculated as P2O5 based on the weight of the zeolite
Data Source
AI summary
The present invention provides a catalyst and a process for its preparation and its use in cracking heavy feedstocks. The catalyst comprises one or more zeolites having a controlled silica to alumina ratio and preferably treated with alkali in the presence of a matrix component selected from the group consisting of clays, synthetic matrix other than pillared clay, and mixtures thereof. The catalyst are particularly useful in treating heavy feedstock such as residues from oil sands processing.