Palladium Crust Catalyst for C3 Hydrocarbon Selective Hydrogenation
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Solution Overview
Problem
Catalysts for selective hydrogenation of C3 hydrocarbon cuts from steam cracking and catalytic cracking face challenges in maintaining selectivity and activity due to issues like intragranular material transfer and oligomerization, particularly when using palladium-based catalysts with high metallic dispersion.
Innovation Solution
A palladium catalyst with less than 20% metallic dispersion, where at least 80% of the palladium is distributed in a crust at the periphery of a porous refractory oxide support, such as silica or alumina, is developed using a colloidal impregnation and hydrothermal treatment process, enhancing selectivity and reducing oligomerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If palladium-based catalysts with high metallic dispersion are used, then catalytic activity is improved, but selectivity deteriorates due to intragranular material transfer and oligomerization
Solution Approach 1:
The patent applies local quality by creating a crust structure where palladium is concentrated at the periphery of the support particles (at least 80% in a crust of 25-450 μm thickness) rather than being uniformly distributed. This peripheral concentration ensures that reactions occur primarily at the external surface, preventing intragranular material transfer and maintaining high selectivity while preserving catalytic activity through the use of a porous support with specific surface area of 70-160 m²/g
2Productivity
If metallic dispersion of palladium is increased, then catalytic activity is enhanced, but oligomerization and polymerization reactions increase leading to catalyst deactivation
Solution Approach 1:
By concentrating palladium in a peripheral crust rather than distributing it throughout the particle interior, the invention limits the volume where oligomerization can occur. The crust structure with thickness of 25-450 μm ensures that reactive sites are confined to the external surface region, reducing polymerization reactions that lead to catalyst deactivation while maintaining sufficient activity through the porous support structure
Solution Approach 2:
The patent employs a porous support with specific surface area of 70-160 m²/g that provides a controlled environment for the palladium crust. The porous structure allows reactant access to the catalytic sites while the specific surface area ensures adequate dispersion of the crust material, maintaining catalytic activity without promoting excessive oligomerization that would deactivate the catalyst
3Reliability
If bimetallic palladium-silver catalysts are used to improve selectivity, then metallic dispersion of palladium is reduced but particle size distribution remains unchanged
Solution Approach 1:
The patent extracts the silver component from the bimetallic system and uses only pure palladium in the active phase. By removing the silver additive, the invention simplifies the catalyst composition while achieving the desired selectivity through the crust distribution pattern and porous support structure, avoiding the complexity of controlling bimetallic interactions and particle size distributions
4Productivity
If palladium is distributed throughout the support, then catalytic activity is maintained, but intragranular material transfer causes loss of selectivity
Solution Approach 1:
The invention resolves this contradiction by creating a non-uniform distribution where palladium is concentrated in a peripheral crust (at least 80% in a crust of 25-450 μm thickness) rather than being uniformly distributed throughout the support. This local concentration at the periphery maintains catalytic activity through the porous support's surface area while preventing intragranular material transfer by confining reactions to the external surface region
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 high selectivity in hydrogenating acetylenic and diolefinic compounds while limiting total hydrogenation of mono-olefins, reducing propylene yield loss and catalyst deactivation, thereby improving process efficiency.
Implementation Method 1
a preparation process comprising a step for colloidal impregnation
Implementation Method 2
a specific hydrothermal treatment step, bringing about sintering of the catalyst, having the effect of reducing the metallic dispersion of the palladium in the catalyst
Implementation Method 3
The selective hydrogenation process can be used to transform the polyunsaturated compounds of oil cuts by conversion of the most unsaturated compounds into the corresponding alkenes, avoiding complete saturation and thus the formation of the corresponding alkanes
Data Source
AI summary
A catalyst comprises an active phase constituted by palladium, and a porous support comprising at least one refractory oxide selected from the group constituted by silica, alumina and silica-alumina, in which:the palladium content in the catalyst is in the range 0.0025% to 1% by weight with respect to the total weight of catalyst;at least 80% by weight of the palladium is distributed in a crust at the periphery of the porous support, the thickness of said crust being in the range 25 to 450 μm;the specific surface area of the porous support is in the range 70 to 160 m2/g;the metallic dispersion D of the palladium is less than 20%.