Hydrodesulfurization Catalyst Regeneration with Group VIb Impregnation
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Solution Overview
Problem
Current methods for rejuvenating hydrodesulfurization catalysts used in gasoline cuts fail to maintain or improve catalytic performance, particularly in terms of selectivity and activity, leading to increased sulfur content and reduced octane numbers in gasoline.
Innovation Solution
A process involving regeneration of spent catalysts in an oxygen-containing gas stream, followed by impregnation with metal compounds from group VIb and optionally group VIII, and phosphorus, along with organic additives, to enhance catalytic activity and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If hydrodesulfurization catalyst is used to remove sulfur from gasoline, then sulfur content is reduced, but octane number decreases due to hydrogenation of olefins
Solution Approach 1:
The catalyst is designed with spatially differentiated functions: the sulfide phase (CoMoS) provides hydrodesulfurization activity while the oxide support (alumina) provides olefin hydrogenation activity. This local quality differentiation allows the catalyst to selectively remove sulfur while controlling olefin hydrogenation, thereby maintaining octane number.
Solution Approach 2:
The invention uses a composite catalyst system combining two distinct phases: a sulfide phase (CoMoS) for hydrodesulfurization and an oxide support (alumina) for olefin hydrogenation. This composite structure enables simultaneous achievement of sulfur removal and controlled olefin processing, resolving the contradiction between sulfur content reduction and octane number maintenance.
2Duration of action of stationary object
If spent catalyst is regenerated by calcination, then it can be reused, but catalytic activity and selectivity are reduced
Solution Approach 1:
The invention performs preliminary impregnation of metal compounds (Co, Mo, W) and phosphorus onto the regenerated catalyst before final activation. This preliminary action restores and enhances the catalytic activity and selectivity that were lost during calcination, enabling the regenerated catalyst to achieve performance comparable to or better than the fresh catalyst.
Solution Approach 2:
The invention changes the chemical composition parameters of the regenerated catalyst by introducing additional metal compounds and phosphorus through impregnation. This parameter modification restores the catalytic activity and selectivity, transforming the degraded regenerated catalyst into a high-performance catalyst that meets or exceeds fresh catalyst performance.
3Quantity of substance
If catalyst replacement frequency is increased to meet sulfur specifications, then sulfur content in fuel is reduced, but cost and waste increase
Solution Approach 1:
The invention enables continuous useful action by developing a regeneration method that restores catalyst activity to levels comparable to or exceeding fresh catalyst performance. This allows the same catalyst to be repeatedly used across multiple cycles, eliminating the need for frequent replacement and reducing catalyst waste while maintaining sulfur removal effectiveness.
Solution Approach 2:
Instead of discarding spent catalyst after a single use, the invention recovers and regenerates it through calcination followed by impregnation with metal compounds and phosphorus. This recovery process restores the catalyst's catalytic properties, allowing it to continue serving its purpose of sulfur removal and significantly reducing waste generation.
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 rejuvenated catalysts exhibit improved activity and selectivity in hydrodesulfurization, effectively reducing sulfur content in gasoline while minimizing octane number loss.
Implementation Method 1
a) the at least partially spent catalyst is regenerated in an oxygen-containing gas stream at a temperature of between 350° C. and 550° C. so as to obtain a regenerated catalyst
Implementation Method 2
b) the regenerated catalyst is brought into contact with at least one impregnation solution containing at least one compound comprising a metal from group VIb
Implementation Method 3
the hydrodesulfurization of a sulfur-containing olefinic gasoline cut in the presence of hydrogen and of a heterogeneous catalyst
Implementation Method 4
the hydrogenation of the olefins present in this type of gasoline concomitantly with the hydrodesulfurization
Data Source
AI summary
A process for rejuvenating an at least partially spent catalyst resulting from a hydrodesulfurization process of a sulfur-containing olefinic gasoline cut, where the at least partially spent catalyst result is from a fresh catalyst a metal from group VIII, a metal from group VIb, and an oxide support, where the process includesa) regenerating the at least partially spent catalyst in an oxygen-containing gas stream at a temperature between 350° C. and 550° C.,b) the regenerated catalyst is brought into contact with an impregnation solution containing a compound containing a metal from group VIb, the molar ratio of the metal from group VIb added per metal from group VIb already present in the regenerated catalyst being between 0.15 and 2.5 mol/mol,c) a drying stage is carried out at a temperature of less than 200° C., andthe use of the rejuvenated catalyst in a hydrodesulfurization process.