Bimodal Pore Catalyst for Selective Hydrodesulfurization
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Solution Overview
Problem
Conventional catalytic hydroprocessing methods for removing sulfur from olefin-containing hydrocarbon feedstocks often hydrogenate olefins along with sulfur compounds, leading to a loss in octane value, which is undesirable for gasoline blending components.
Innovation Solution
A selective hydrodesulfurization catalyst with a bimodal pore size distribution and a specific composition, including calcined molybdenum trioxide, nickel, and cobalt, is used to minimize the hydrogenation of olefins while effectively desulfurizing the feedstock, characterized by a calcined catalyst particle with a large percentage of pores less than 250 angstroms and greater than 1000 angstroms, and a material absence of impregnated nickel on the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional catalytic hydroprocessing methods are used to remove sulfur from olefin-containing hydrocarbon feedstocks, then sulfur removal is achieved, but olefin hydrogenation occurs leading to loss in octane value
Solution Approach 1:
The catalyst is designed with spatially differentiated metal distributions: Group VIII metals (Ni, Co) are concentrated in the bulk interior for sulfur removal, while Group VIB metals (Mo, W) are concentrated on the external surface for selective hydrodesulfurization. This local quality differentiation allows the catalyst to perform sulfur removal in the bulk while maintaining olefin selectivity on the surface, resolving the contradiction between sulfur removal efficiency and olefin composition stability.
Solution Approach 2:
The invention uses a composite catalyst structure combining multiple metal groups (VIII metals for hydrogenation activity and VIB metals for selective hydrodesulfurization) with specific pore size distributions (bimodal: 0.03-0.5 μm and 1-10 μm). This composite material integrates the beneficial properties of different metals and pore structures to achieve both effective sulfur removal and olefin preservation, directly addressing the technical contradiction.
2Productivity
If high concentrations of Group VIII metal components are used to enhance sulfur removal activity, then hydroprocessing activity increases, but olefin hydrogenation increases causing octane value loss
Solution Approach 1:
The catalyst employs local quality differentiation where Group VIII metals are positioned in the bulk interior (providing hydrogenation activity for sulfur removal) while Group VIB metals are positioned on the external surface (providing selective hydrodesulfurization). This spatial separation allows high sulfur removal productivity through bulk metal activity while the surface metal composition prevents olefin hydrogenation, resolving the contradiction between productivity and composition stability.
Solution Approach 2:
The invention changes the parameter distribution by creating a bimodal pore size distribution (combining micropores 0.03-0.5 μm with macropores 1-10 μm) and controlling metal distribution by weight percent (Group VIII: 3-15%, Group VIB: 5-20%). These parameter optimizations enable high sulfur removal rates while maintaining olefin selectivity, directly addressing the contradiction between productivity and olefin saturation.
3Quantity of substance
If conventional catalyst compositions are used for hydrodesulfurization, then sulfur compounds are converted, but the process lacks selectivity and hydrogenates olefins simultaneously
Solution Approach 1:
The catalyst achieves selectivity through local quality differentiation: Group VIB metals on the external surface provide selective hydrodesulfurization activity, while Group VIII metals in the bulk interior provide hydrogenation activity for sulfur removal. This spatial separation of functions enables high sulfur conversion with simultaneous olefin preservation, resolving the contradiction between sulfur conversion and process selectivity.
Solution Approach 2:
The invention employs a composite catalyst material combining Group VIII metals (Ni, Co) and Group VIB metals (Mo, W) with a bimodal pore size distribution. This composite structure integrates multiple catalytic functions: sulfur removal through bulk metal activity and selective hydrodesulfurization through surface metal activity, achieving both high sulfur conversion and olefin selectivity that conventional single-composition catalysts cannot achieve.
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
This approach allows for significant sulfur removal with minimal hydrogenation of olefins, maintaining high octane values and achieving sulfur reductions of up to 90% with less than 30% olefin saturation, thereby enhancing the quality of gasoline blending components.
Implementation Method 1
catalyst and process for the selective hydrodesulfurization of an olefin-containing hydrocarbon feedstock
Implementation Method 2
the calcined catalyst particle being characterized by having a bimodal pore size distribution with at least 20% of the total pore volume being in pores having a diameter less than 250 angstroms and at least 10% of the total pore volume being in pores having a diameter greater than 1000 angstroms
Data Source
AI summary
A catalyst and its use for selectively desulfurizing sulfur compounds present in an olefin-containing hydrocarbon feedstock to very low levels with minimal hydrogenation of olefins. The catalyst comprises an inorganic oxide substrate containing a nickel compound, a molybdenum compound and optionally a phosphorus compound, that is overlaid with a molybdenum compound and a cobalt compound. The catalyst is further characterized as having a bimodal pore size distribution with a large portion of its total pore volume contained in pores having a diameter less than 250 angstroms and in pores having a diameter greater than 1000 angstroms.