Nickel-Molybdenum Catalyst Spatial Distribution for Selective Hydrogenation
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Solution Overview
Problem
Current catalysts for selective hydrogenation of gasolines from catalytic cracking processes face challenges in efficiently converting polyunsaturated compounds while minimizing hydrogenation of olefins and preventing gum formation, which leads to catalyst deactivation and increased sulfur content, making it difficult to meet stringent environmental standards.
Innovation Solution
A catalyst comprising a specific distribution of group VIB and group VIII metals on an alumina support, with the group VIB metal distributed at the periphery and group VIII metal homogeneously distributed, optimizing the molar ratios and calcination processes to enhance selectivity and activity for diolefin hydrogenation and sulfur compound conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional catalysts are used for selective hydrogenation, then diolefin conversion is achieved, but olefin hydrogenation increases and octane is lost
Solution Approach 1:
The patent applies local quality by creating distinct spatial zones within the catalyst structure: group VIB metals (Mo, W) are concentrated at the periphery to perform selective diolefin hydrogenation, while group VIII metals (Ni, Pd, Pt) are distributed homogeneously throughout the support to handle sulfur compound conversion. This spatial differentiation of metal functions resolves the contradiction by ensuring each metal type operates in its optimal location for its specific reaction.
Solution Approach 2:
The catalyst structure is segmented into functional zones with different metal compositions. The peripheral region contains primarily group VIB metals for selective hydrogenation, while the internal structure contains group VIII metals for desulfurization. This segmentation allows independent optimization of each function, maintaining high diolefin conversion while preserving olefin integrity.
2Productivity
If catalysts with high activity are used, then diolefin hydrogenation is enhanced, but gum formation increases and catalyst deactivates
Solution Approach 1:
The patent converts the potentially harmful effect of high catalyst activity (which causes gum formation and deactivation) into a benefit by carefully controlling the metal distribution. The peripheral concentration of group VIB metals provides high initial activity for diolefin conversion, while the homogeneous group VIII metal distribution throughout the support prevents gum accumulation by converting sulfur compounds, thereby maintaining long-term catalyst stability.
3Object-affected harmful factors
If sulfur content is reduced to meet environmental standards, then environmental compliance is achieved, but catalyst performance deteriorates
Solution Approach 1:
The patent merges two previously separate catalytic functions into a single integrated catalyst: selective hydrogenation (group VIB metals) and hydrodesulfurization (group VIII metals). This combination allows the catalyst to simultaneously reduce sulfur content to meet environmental standards while maintaining high productivity for diolefin conversion, resolving the contradiction between environmental compliance and catalyst performance.
4Ease of manufacture
If homogeneous metal distribution is used, then catalyst manufacturing is simplified, but selectivity for diolefin hydrogenation decreases
Solution Approach 1:
The patent implements local quality by deliberately creating non-uniform metal distribution: group VIB metals are concentrated at the periphery while group VIII metals are distributed homogeneously. This controlled heterogeneity optimizes selectivity for diolefin hydrogenation by placing the appropriate metal in the optimal location, while still being manufacturable through controlled impregnation and calcination processes.
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 improved selectivity and activity for diolefin hydrogenation and sulfur compound conversion, reducing gum formation and maintaining catalyst performance, allowing for effective desulfurization and increased molecular weight of mercaptans without loss of octane, thus meeting stringent environmental standards.
Implementation Method 1
selective hydrogenation of polyunsaturated compounds into monounsaturated compounds contained in gasolines
Implementation Method 2
catalyst for the selective hydrogenation of a gasoline
Implementation Method 3
increase the molecular weight of light sulfur compounds by reaction with unsaturated compounds
Data Source
AI summary
A selective hydrogenation catalyst contains an active phase having a group VIB metal and a group VIII metal, and a porous support containing alumina. The group VIB metal content is between 1 and 18% by weight relative to total weight of the catalyst, and the group VIII metal content of the active phase, measured in oxide form, is between 1 and 20% by weight relative to total weight of the catalyst. The molar ratio between the group VIII metal and the group VIB metal is between 1.0 and 3.0 mol/mol. The group VIII metal is homogeneously distributed in the porous support with a distribution coefficient R of between 0.8 and 1.2, measured using a Castaing microprobe, and the group VIB metal is distributed at the periphery of the porous support with a distribution coefficient R of less than 0.8.