Mixed Catalyst System for Heavy Crude Hydrotreating
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Solution Overview
Problem
Ebullated bed hydrotreating processes for heavy crude oil face challenges in maintaining catalyst activity and adaptability due to high wear and tear, complex reactor structures, and limitations in pore structure adjustment, leading to inefficient processing of poor-quality residua with high metal impurities.
Innovation Solution
A mixed catalyst system comprising Catalyst A and Catalyst B with specific surface areas and pore distributions is used in a multi-stage ebullated bed reactor, allowing for flexible adjustment of catalyst properties and reducing the need for on-line addition and withdrawal systems, thereby enhancing hydrogenation activity and adaptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the catalyst is added and withdrawn periodically under high temperature and high pressure to maintain high catalytic activity, then the adaptability for poor-quality feedstock is improved, but the catalyst particles experience more crash and friction leading to breaking and abrasion
Solution Approach 1:
The patent changes the operational parameters by maintaining continuous catalyst presence in the reactor without periodic withdrawal, eliminating the turbulence and mechanical stress associated with catalyst addition and withdrawal operations. This allows the catalyst to maintain high activity while avoiding the crushing and abrasion that occurs during periodic handling under high temperature and pressure conditions.
Solution Approach 2:
The patent employs a disposable catalyst bed that is replaced as a whole unit rather than individually regenerated. The catalyst particles are designed to be economically replaceable after a certain service life, eliminating the need for complex on-line regeneration systems while maintaining process adaptability for varying feedstock qualities.
2Productivity
If the catalyst is kept in a fluidized state to enable ebullated bed operation, then the catalytic activity is maintained, but the catalyst requires specific granular properties that increase manufacturing complexity
Solution Approach 1:
The patent segments the catalyst bed into multiple replaceable units or zones within the reactor. Each segment can be independently managed and replaced, allowing the system to maintain fluidized bed operation with catalysts that have optimized granular properties for their specific function, rather than requiring all catalyst particles to meet stringent uniform specifications.
Solution Approach 2:
The patent uses composite catalyst structures combining different materials with complementary properties. The support matrix provides mechanical strength and appropriate particle morphology for fluidized bed operation, while active components are deposited on the surface, allowing optimization of catalytic activity without compromising the granular integrity required for ebullated bed operation.
3Adaptability or versatility
If the pore size of the catalyst is increased to enable asphaltene diffusion, then the demetallization degree is improved, but the surface area decreases reducing desulphurization activity
Solution Approach 1:
The patent applies local quality by creating catalysts with heterogeneous pore structures where different regions have different pore size characteristics. Macropores (greater than 10 nm) are distributed throughout the catalyst particle to facilitate asphaltene diffusion and demetallization, while the overall high surface area is maintained through appropriate micropore distribution for desulphurization reactions. This localized optimization allows both functions to operate effectively simultaneously.
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 mixed catalyst system improves hydrodesulphurization, demetallization, and asphaltene conversion rates, reduces catalyst consumption, and achieves long-cycle stable operation with lower equipment investment and operational complexity.
Implementation Method 1
Hydrodesulfurization and hydrodemetallization are two important reactions in the hydrogenation process of a heavy crude oil such as residua
Implementation Method 2
Hydrodesulfurization and hydrodemetallization are two important reactions in the hydrogenation process of a heavy crude oil such as residua
Implementation Method 3
The decomposition rate of asphaltene in hydrogenation process is related to the pore size of the catalyst as used
Implementation Method 4
the bed expands; the catalyst particles inside the reactor in a state of irregular motion, i.e., a 'boiling' state
Implementation Method 5
the catalyst is added and withdrawn from the reactor periodically under high temperature and high pressure, the catalyst is in a turbulence state all the time in the reactor
Data Source
Figure 1
AI summary
The present invention relates to an ebullated bed hydrotreating process, wherein a heavy crude oil and hydrogen are introduced into an ebullated bed hydrotreating reactor from the bottom of the reactor for carrying out reaction under the heavy crude oil hydrotreating conditions, and then the reaction products are discharged from the top of the reactor; wherein a mixed catalyst is used in the ebullated bed hydrotreating reactor, said mixed catalyst is a physical mixture of at least two catalysts, A and B at a volume ratio of Catalyst A to Catalyst B being 1: (0.1-10); wherein Catalyst A has a specific surface area of 80-200m2/g and an average pore diameter of more than 20 nm, the pore volume of the pores having a pore diameter of 30-300nm comprises 35 vol.%-60 vol.% of the total pore volume of Catalyst A; Catalyst A contains 1.0 wt%-10.0 wt% of a metal oxide of group VIB, and 0.1 wt%-8.0 wt% of a metal oxide of group VIII, by the total weight of Catalyst A; and wherein Catalyst B has a specific surface area of 180-300m2/g and an average pore diameter of 9-15nm, the pore volume of the pores having a pore diameter of 5-20 nm comprises at least 70 vol. % of the total pore volume of Catalyst B; Catalyst B contains 3.0 wt%-20.0 wt% of a metal oxide of group VIB, and 0.3 wt%-8.0 wt% of a metal oxide of group VIII, by total weight of Catalyst B.