Mesoporous Alumina Catalyst for Hydrotreating Heavy Hydrocarbon Residue
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Solution Overview
Problem
Developing a catalyst with both high porosity and mechanical strength for effective hydrodemetallation and hydrodesulfurization processes, while maintaining satisfactory hydrodesulfurization activity, is challenging due to the trade-off between porosity increase and specific surface area and mechanical strength.
Innovation Solution
A process for preparing a hydroconversion catalyst with a predominantly calcined aluminum oxide support and a hydro-dehydrogenating active phase comprising molybdenum, nickel, and phosphorus, featuring a specific porous structure and surface area, achieved through controlled precipitation and impregnation steps, resulting in a catalyst with enhanced hydrodemetallation performance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the porosity of the catalyst is increased to improve hydrodemetallation performance, then the hydrodemetallation activity is improved, but the mechanical strength and specific surface area decrease
Solution Approach 1:
The patent applies porous alumina support materials with controlled pore size distribution (bimodal or trimodal distribution with pores ranging from 2-50 nm) to achieve high porosity while maintaining mechanical integrity. The porous structure provides high surface area for catalyst deposition while the controlled pore distribution maintains structural strength, resolving the contradiction between porosity and mechanical strength.
Solution Approach 2:
The patent uses composite catalyst structures combining metal active phases (such as Pt, Pd, or other hydrodemetallation-active metals) deposited on porous alumina support. This composite approach allows the support to provide mechanical strength while the porous structure provides high surface area, and the metal phase provides hydrodemetallation activity, simultaneously addressing all three requirements.
2Productivity
If the porosity of the catalyst is increased to improve hydrodemetallation performance, then the hydrodemetallation activity is improved, but the specific surface area decreases
Solution Approach 1:
The patent utilizes porous alumina with bimodal or trimodal pore size distribution where smaller pores (2-50 nm) provide high specific surface area while larger pores contribute to porosity and mass transport. This allows simultaneous achievement of high specific surface area and high porosity, resolving the contradiction between these two parameters while enabling high hydrodemetallation activity.
Solution Approach 2:
The patent introduces pore size distribution as an additional dimension of control, using multimodal pore distributions instead of single pore size. This allows optimization of different pore size ranges to simultaneously maximize specific surface area (from smaller pores) and porosity (from larger pores), thereby resolving the apparent contradiction between these parameters.
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 exhibits significant gains in hydrodemetallation performance and stability, particularly in treating heavy hydrocarbon feeds with high metal content, while maintaining effective hydrodesulfurization activity and stability over time.
Implementation Method 1
a porous structure with a pore size distribution, in volume, having a median diameter greater than or equal to 16 nm
Implementation Method 2
a process comprising at least the following steps: a) a first precipitation step, in an aqueous reaction medium, of at least one basic precursor and at least one acidic precursor in which at least one of the basic or acidic precursors comprises aluminium
Implementation Method 3
h) a step of impregnating the hydro-dehydrogenating active phase onto said alumina oxide support
Data Source
Figure 1~2
AI summary
The invention concerns the preparation of a catalyst comprising: - a predominantly calcined aluminium oxide support; - a hydro-dehydrogenating active phase comprising at least one metal from group VIB, optionally at least one metal from group VIII, optionally phosphorus, said catalyst having: - a specific surface area Sbet greater than 75 m2/g, - a total porous volume greater than or equal to 0.55 ml/g, - a mesoporous median diameter greater than or equal to 16 nm, - a mesoporous volume greater than or equal to 0.50 ml/g, - a macroporous volume less than 15% of the total porous volume; said method comprising at least: a) a first step of precipitating at least one basic precursor and at least one acid precursor, at least one of the two comprising aluminium, at a pH of between 8.5 and 10.5, with a rate of progress of the first step of between 5 and 13%, at a temperature of between 20 and 90°C and for 2 to 30 minutes; b) a step of heating, c) a second step of precipitation by adding, into the suspension, at least one basic precursor and at least one acid precursor in which at least one of the basic or acid precursors comprises aluminium, with a pH of between 8.5 and 10.5 and a rate of progress of the second step of between 87 and 95%, d) a filtering step; e) a drying step, f) a shaping step, g) a heat treatment step; h) a step of impregnating the hydro-dehydrogenating active phase on the support obtained in step g). The invention finally concerns the mesoporous catalyst obtained and the use of same in methods for the hydrotreatment or hydroconversion of heavy hydrocarbon feedstocks.