Hydrodemetallization Catalyst Bimodal Pore Structure
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Solution Overview
Problem
Heavy crude oil processing faces challenges due to high asphaltene and metal content, leading to rapid catalyst deactivation and decreased efficiency in hydrodemetallization (HDM) processes, particularly in residue hydroprocessing where coke and metal depositions significantly reduce catalyst activity.
Innovation Solution
A hydrodemetallization (HDM) catalyst with an alumina and carbon extrudate support having a 1:1 weight ratio, bimodal pore size distribution, and impregnated with hydrogenation active metals like Mo, W, and Fe, along with promoter metals such as Co, Ni, and Fe, and optionally ethylene diamine tetra acetic acid (EDTA), which maintains activity for at least 1200 hours and has a high metal retention capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hydrodemetallization catalysts are used for heavy crude oil processing, then initial metal removal activity is achieved, but catalyst activity decreases rapidly due to coke and metal depositions
Solution Approach 1:
The patent employs a support with bimodal pore size distribution (micropores <2 nm and mesopores 2-50 nm) to facilitate both metal adsorption and diffusion of large asphaltene molecules. The micropores provide high surface area for metal retention while mesopores enable access for bulky asphaltene species, preventing rapid deactivation and extending catalyst lifespan.
Solution Approach 2:
The catalyst uses a composite support structure combining alumina and carbon materials in specific ratios (1:1 to 4:1 weight ratios). This composite approach leverages the high surface area and metal affinity of alumina alongside the hydrophobic properties and pore structure of carbon, creating synergistic effects that enhance both activity stability and lifespan.
2Quantity of substance
If catalysts with high metal retention capacity are designed, then metal removal efficiency improves, but coke deposition increases and blocks active sites
Solution Approach 1:
The catalyst design creates different functional zones within the pore structure: micropores (<2 nm) serve as metal trapping sites with high retention capacity, while mesopores (2-50 nm) facilitate asphaltene diffusion and reduce coke formation. This spatial differentiation of pore functions allows high metal retention without excessive coke deposition blocking active sites.
Solution Approach 2:
The patent optimizes the pore size distribution parameters and support composition ratios to balance metal retention and coke resistance. By controlling the proportion of micropores versus mesopores and adjusting alumina-to-carbon ratios, the catalyst achieves optimal metal capacity while minimizing harmful coke deposition that would block active sites.
3Productivity
If the catalyst processes high asphaltene content feedstock, then conversion of heavy fractions improves, but catalyst deactivation accelerates
Solution Approach 1:
The catalyst extends the effective pore size range by incorporating both micropores and mesopores, creating a multi-dimensional pore network. This allows asphaltene molecules (which are too large for conventional micropores alone) to access active sites through mesopores while still achieving high conversion efficiency, all while maintaining reliability by preventing rapid deactivation.
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 effectively removes metals and sustains activity over a long period, minimizing coke and metal depositions on catalytic sites, enhancing stability and conversion of asphaltene molecules through optimized textural properties and metal storage capacity.
Implementation Method 1
The catalyst typically has a high metal retention capacity, e.g., about 40% to about 50 weight %
Implementation Method 2
The support can be impregnated with at least one hydrogenation active metal and at least one promoter metal from the transition metals of Groups 6, 8, 9, and 10 of the Periodic Table
Data Source
AI summary
A hydrodemetallization (HDM) catalyst includes an alumina and carbon extrudate support having a weight ratio of about 1:1 alumina to carbon and bimodal type pore size distribution, i.e., both meso-porosity and macro-porosity. The support can be impregnated with at least one hydrogenation active metal and, optionally, at least one promoter metal from the transition metals of Groups 6, 8, 9, and 10 of the Periodic Table. The hydrogenation active metal can be, for example, Mo, W, and Fe. The promoter metal can be, for example, Co, Ni, and Fe. The catalyst may further include ethylene diamine tetra acetic acid (EDTA).