Sol-Gel Mixed Oxide Hydrotreatment Catalysts
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Solution Overview
Problem
Current hydrotreatment catalysts face challenges in achieving accurate stoichiometry control and high activity for decomposing sterically hindered dibenzothiophenes and compounds containing nitrogen, which are difficult to treat, especially under stringent emission regulations.
Innovation Solution
A sol-gel process is developed to prepare mixed oxides with specific compositions of Ni, Co, Mo, W, Si, and Al, which are then sulfided to create catalysts with high surface areas and pore volumes, enabling effective hydrotreatment, particularly in hydrodesulfurization and hydrodenitrogenation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional coprecipitation techniques are used to prepare catalysts, then the preparation process is relatively simple, but accurate control on the stoichiometry of the final material cannot be achieved
Solution Approach 1:
The patent employs sol-gel process parameters (pH, temperature, aging time, composition ratios) to precisely control the stoichiometry of the final catalyst material. By adjusting parameters such as the SiO2/Al2O3 molar ratio (30-500) and the composition of transition metals, the method achieves accurate compositional control that conventional coprecipitation cannot provide.
Solution Approach 2:
The sol-gel process introduces intermediate steps (gel formation, drying, calcination) between the initial mixing and final catalyst formation. These intermediate stages allow for controlled precipitation and uniform distribution of metal oxides, enabling precise stoichiometry control while managing process complexity through systematic step-by-step transformation.
2Productivity
If catalysts are designed for high activity in hydrotreatment, then sulfur and nitrogen removal efficiency improves, but the catalyst structure becomes more complex requiring multiple metals and promoters
Solution Approach 1:
The patent combines multiple functional components (Ni or Co promoters, Mo or W base metals, SiO2-Al2O3 support) into a single integrated catalyst system prepared by sol-gel. This merging of components during the gel formation stage ensures uniform distribution and synergistic interaction, achieving high hydrotreatment activity while managing compositional complexity through a unified preparation approach.
Solution Approach 2:
The invention creates composite catalyst materials with a core-shell or interpenetrating structure where transition metal sulfides (MoS2, WS2) are dispersed on a SiO2-Al2O3 mixed oxide support. This composite structure provides both the high activity needed for breaking sterically hindered dibenzothiophenes and the structural stability required for industrial application.
3Productivity
If the surface area and pore volume of catalysts are increased to treat sterically hindered compounds, then access to active sites improves, but the mechanical strength of the catalyst may decrease
Solution Approach 1:
The patent utilizes the inherent porosity of the SiO2-Al2O3 mixed oxide support created during the sol-gel process. The gel structure forms a network with controlled pore sizes and high surface area (typically 200-500 m²/g), providing excellent access to active sites for bulky dibenzothiophene molecules while the cross-linked oxide network maintains mechanical strength.
Solution Approach 2:
The catalyst design provides different local properties: the external surface and pore walls provide high surface area for catalytic activity, while the bulk oxide structure provides mechanical strength. The transition metal sulfides are localized within the porous network, creating regions of high catalytic activity without compromising the overall structural integrity of the catalyst pellet.
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 sulfided catalysts exhibit enhanced activity and stability in hydrotreatment processes, effectively reducing sulfur and nitrogen impurities in hydrocarbon feeds, meeting stringent emission standards and maintaining mechanical integrity.
Implementation Method 1
suitable methods are also described for the preparation of said sol-gel precursors
Implementation Method 2
EP 340868 describes a sol-gel process for the preparation of a micro-mesoporous silica and alumina gel
Implementation Method 3
possibly containing a nitrogenated compound or an organic residue coming from the partial calcination of the nitrogenated compound
Implementation Method 4
The sulfided metal compounds, called (A)S, containing a metal X selected from Ni, Co and mixtures thereof, a metal Y selected from Mo, W and mixtures thereof
Implementation Method 5
The catalysts obtained by the sulfidation of these precursors can be used as hydrotreatment catalysts
Implementation Method 6
The sulfided catalysts exhibit enhanced activity and stability in hydrotreatment processes, effectively reducing sulfur and nitrogen impurities in hydrocarbon feeds
Data Source
AI summary
New sulfided metal catalysts are described, containing a metal X selected from Ni, Co and mixtures thereof, a metal Y selected from Mo, W and mixtures thereof, an element Z selected from Si, Al and mixtures thereof, and possibly an organic residue, obtained by the sulfidation of mixed oxide precursors, also new, having general formula (A) Xa Yb Zc Od. pC (A) possibly shaped without a binder, or by sulfidation of mixed oxides having formula (A), in shaped form with a binder, wherein X is selected from Ni, Co and mixtures thereof, Y is selected from Mo, W and mixtures thereof, Z is selected from Si, Al and mixtures thereof, 0 is oxygen, C is selected from: a nitrogenated compound N, an organic residue deriving from the partial calcination of the nitrogenated compound N, said nitrogenated compound N, when present, being selected from: a) an alkyl ammonium hydroxide having formula (I) RIRIIRIIIRIVNOH ( I ) wherein the groups RI-RIV, the same or different, are aliphatic groups containing from 1 to 7 carbon atoms, b) an amine having formula (II) R1R2R3N (II) wherein R1 is a linear, branched or cyclic alkyl, containing from 4 to 12 carbon atoms, and R2 and R3, the same or different, are selected from H and a linear, branched or cyclic alkyl, containing from 4 to 12 carbon atoms, said alkyl being equal to or different from R1, a, b, c, d are the number of moles of the elements X, Y, Z, O, respectively, p is the weight percentage of C with respect to the total weight of the precursor having formula (A), a, b, c, d are higher than 0 a/b is higher than or equal to 0.3 and lower than or equal to 2, (a+b) /c is higher than or equal to 0.3 and lower than or equal to 10, preferably varying from 0.8 to 10 d = (2a+6b+Hc)/2 wherein H = 4 when Z = Si H = 3 when Z = Al and p is higher than or equal to 0 and lower than or equal to 40%. Said catalysts can be used as hydrotreating catalysts.