Cyclodextrin Catalyst for Selective Gasoline Hydrodesulphurization
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Solution Overview
Problem
Conventional hydrotreatment processes for catalytically cracked gasolines effectively reduce sulfur content but result in significant octane number loss, and the formation of refractory phases in hydrotreatment catalysts limits catalytic activity and selectivity, making it challenging to meet stringent environmental regulations.
Innovation Solution
A hydrodesulphurization process using a catalyst prepared with a support contacted with metal precursors and a cyclic oligosaccharide like cyclodextrin, followed by drying and sulphurization, to enhance catalytic activity and selectivity while minimizing octane number loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional hydrodesulphurization processes are used to reduce sulfur content in catalytically cracked gasolines, then sulfur content is reduced, but octane number drops significantly
Solution Approach 1:
The catalyst structure is designed with specific local properties: a porous support with controlled surface area and pore volume, and an active phase distributed in a specific manner. The cyclic oligosaccharide modification creates localized active sites that preferentially catalyze hydrodesulphurization reactions over hydrogenation reactions, enabling selective sulfur removal while preserving olefin content and octane number.
Solution Approach 2:
The catalyst is a composite material combining a porous oxide support (such as alumina or silica-alumina) with a metal active phase (such as cobalt-molybdenum or nickel-molybdenum) and a cyclic oligosaccharide modifier. This composite structure provides both the necessary catalytic activity for sulfur removal and the selectivity to maintain high octane number by preventing excessive olefin saturation.
2Productivity
If the quantity of active phase in sulphide form is increased to maximize catalytic activity, then catalytic activity is improved, but crystalline oxide phases form that are refractory to sulphurization
Solution Approach 1:
The cyclic oligosaccharide is introduced during the catalyst preparation stage, before the sulphurization step. This preliminary action of the cyclic oligosaccharide prevents the formation of refractory crystalline oxide phases during the deposition and drying stages, ensuring that the active phase remains in a form that can be effectively sulphurized and activated for catalysis.
Solution Approach 2:
The cyclic oligosaccharide acts as an intermediary substance during catalyst preparation. It mediates between the metal precursors and the support surface, controlling the deposition and distribution of the active phase. This intermediary作用 prevents direct formation of refractory crystalline phases and ensures the active phase remains dispersible and sulphurizable.
3Productivity
If the active phase content is increased to enhance catalytic performance, then catalytic activity may improve, but crystallites of MoO3, NiO, CoO, Co3O4 or CoMoO4 form that reduce the degree of sulphurization
Solution Approach 1:
The catalyst preparation parameters are optimized by introducing the cyclic oligosaccharide, which changes the physical and chemical parameters of the active phase deposition. This modification prevents the growth of crystallites that would otherwise form at higher active phase contents, maintaining a high degree of sulphurization and optimal catalytic performance.
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 process significantly improves the reduction of sulfur content in gasoline cuts with minimal octane number loss and maintains or enhances catalytic activity and selectivity, effectively addressing the limitations of conventional methods.
Implementation Method 1
a support formed from at least one oxide, said catalyst being prepared using a process comprising at least: i) at least one step for bringing at least said support into contact with at least one solution containing at least one precursor of at least said metal from group VIII and at least one precursor of at least said metal from group VIB; ii) at least one step for bringing at least said support into contact with at least one organic compound formed from at least one cyclic oligosaccharide
Implementation Method 2
iii) at least one drying step to obtain at least said metal from group VIII and at least said metal from group VIB in the oxide form
Implementation Method 3
iv) at least one sulphurization step such that said active phase is in the sulphide form
Implementation Method 4
The increasing severity of automobile pollution regulations in 2009 in the European Community is forcing refiners to reduce the sulphur content in gas oils and gasolines very substantially
Data Source
AI summary
Hydrodesulphurization of a gasoline cut containing hydrocarbons containing at least 2 carbon atoms per molecule and having an end point of 250° C. or less, by contacting the gasoline cut with at least one catalyst having an active phase of at least one metal from group VIII and at least one metal from group VIB deposited on a support, said catalyst being prepared using a process of:i) contacting support with precursors of group VIII and group VIB metals;ii) contacting support with at least one organic compound formed from at least one cyclic oligosaccharide composed of at least 6α-(1,4)-bonded glucopyranose subunits;iii) drying to obtain at least said metal from group VIII and at least said metal from group VIB in the oxide form; theniv) sulphurization such that said active phase is in the sulphide form;i) and ii) being carried out separately, in any order, or simultaneously.