Crust-Phase Hydrodesulfurization Catalyst for Octane Retention
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Solution Overview
Problem
Existing hydrotreating processes for gasoline cuts from fluidized-bed catalytic cracking units face challenges in reducing sulfur content without significantly lowering the octane number, due to the hydrogenation of olefins.
Innovation Solution
A catalyst comprising a specific distribution of group VIB, group VIII elements, and phosphorus as a crust on a porous alumina support, optimized to maintain high selectivity and activity for hydrodesulfurization while minimizing olefin hydrogenation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hydrotreating catalysts are used to reduce sulfur content, then sulfur removal efficiency is improved, but octane number decreases due to olefin hydrogenation
Solution Approach 1:
The catalyst employs a core-shell structure where the active phase (CoMoS) is distributed as a crust at the periphery of the support, creating local concentration differences. This peripheral distribution ensures that hydrodesulfurization occurs primarily at the catalyst surface, minimizing olefin hydrogenation while maximizing sulfur removal efficiency
Solution Approach 2:
The catalyst combines multiple components (group VIB elements, group VIII elements, phosphorus, and alumina support) in a composite structure. This composite material approach creates synergistic effects where the specific combination and distribution of components enhance hydrodesulfurization activity while maintaining selectivity against olefin hydrogenation
2Productivity
If catalyst activity for hydrodesulfurization is increased, then sulfur content reduction is improved, but selectivity against olefin hydrogenation decreases
Solution Approach 1:
The active phase is concentrated at the periphery of the catalyst support rather than being uniformly distributed. This local quality differentiation ensures high hydrodesulfurization activity at the surface while limiting bulk hydrogenation reactions, thereby maintaining high selectivity
Solution Approach 2:
The catalyst optimizes the thickness of the active phase crust (100-1200 μm) and the specific surface area of the support (100-250 m²/g). These parameter changes create the optimal balance between activity and selectivity by controlling the accessibility of reactants to active sites
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 achieves enhanced hydrodesulfurization activity and selectivity, maintaining the octane number of gasoline cuts while effectively reducing sulfur content, even at higher sulfur levels.
Implementation Method 1
a catalyst comprising an active phase containing at least one group VIB element, at least one group VIII element and phosphorus, and a porous support containing at least alumina
Data Source
AI summary
Catalyst containing an active phase which contains a group VIB element, at least one group VIII element and phosphorus, and a support containing alumina, the catalyst being characterized in that at least 80% by weight of the group VIB elements, of the group VIII elements and of the phosphorus are distributed in the form of a crust at the periphery of said support, the thickness of said crust being between 100 and 1200 μm, the content of group VIB element being between 1% and 8% by weight relative to the total weight of the catalyst, the content of group VIII element being between 0.5% and 5% by weight relative to the total weight of the catalyst, and the content of phosphorus being between 0.2% and 3% by weight relative to the total weight of the catalyst, and the support having a specific surface area of between 100 m2/g and 250 m2/g.