Selective Hydrogenation Catalyst via Molten Salt and Organic Additive
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Solution Overview
Problem
Existing catalysts for the selective hydrogenation of polyunsaturated compounds face challenges such as inadequate control over the amount of active phase deposited, unsuitability for slurry reactors, and safety concerns due to exothermic reactions, while also requiring handling of toxic precursors.
Innovation Solution
A new catalyst process involving a nickel-based active phase and an alumina support, where the alumina is treated with an organic additive and then contacted with a nickel metal salt, followed by heating and drying to control nickel particle size and distribution, thereby enhancing catalytic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If molten salt method is used to deposit metal phase, then the active phase localizes at the periphery of the support, but the amount of active phase deposited cannot be precisely controlled
Solution Approach 1:
The support is pre-treated with an organic additive (such as citric acid, oxalic acid, or other carboxylic acids) before metal salt impregnation. This preliminary treatment creates specific chemical sites on the support surface that control subsequent metal deposition, enabling both precise localization and controlled amount of active phase deposition.
Solution Approach 2:
The organic additive acts as an intermediary between the support and the metal salt. It mediates the interaction by providing functional groups that selectively bind metal ions, thereby controlling both where the metal deposits and how much accumulates on the support surface.
2Ease of manufacture
If conventional catalyst preparation methods are used, then the catalyst can be manufactured, but it requires multiple steps including solvent addition and calcination
Solution Approach 1:
The invention combines multiple preparation steps into a single operation. The support is impregnated with metal salt solution in the presence of the organic additive, and the entire mixture is directly heated to evaporate the solvent and form the catalyst precursor in one step, eliminating separate calcination and drying operations.
Solution Approach 2:
The organic additive serves multiple functions simultaneously: it acts as a dispersant for the metal salt, a structure-directing agent for particle formation, and a template for the final catalyst architecture. This multi-functionality reduces the need for multiple specialized treatment steps.
3Reliability
If high temperature molten salt treatment is used, then the metal phase reducibility is improved, but the reaction becomes highly exothermic and unsafe
Solution Approach 1:
The invention changes the temperature parameter from high temperature (molten salt conditions) to moderate temperature (below the melting point of the metal salt). This parameter change maintains the beneficial metal phase formation while avoiding the excessive exothermic reactions that occur at higher temperatures.
Solution Approach 2:
The organic additive serves as a thermal buffer and reaction mediator. It controls the release of metal ions from the salt and moderates the exothermic reduction reactions, preventing thermal runaways while still achieving the desired metal phase formation.
4Quantity of substance
If large amounts of toxic metal precursor are handled, then the active phase content is sufficient, but the safety and environmental issues increase
Solution Approach 1:
The organic additive creates local quality differences on the support surface, with specific regions having high affinity for metal ions. This localized binding enables achieving sufficient active phase content with much lower overall metal precursor amounts, reducing toxicity and handling requirements.
Solution Approach 2:
The organic additive molecules act as templates or copies that guide the deposition pattern of metal ions. This templating effect allows precise control over metal distribution, achieving high active phase content efficiency without requiring large quantities of toxic precursors.
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 achieves high intrinsic activity of the nickel active phase with nickel particle sizes less than 18 nm, maintaining or exceeding conventional catalyst performance levels while using less nickel and reducing the number of preparation steps.
Implementation Method 1
the alumina support is brought into contact with at least one organic additive comprising oxygen and/or nitrogen
Implementation Method 2
the alumina support is brought into contact with at least one nickel metal salt, at a temperature of less than the melting point of said nickel metal salt, in order to form a solid mixture
Implementation Method 3
the solid mixture obtained on conclusion of steps a) and b) is heated with stirring to a temperature between the melting point of said metal salt and 200° C.
Implementation Method 4
the catalyst precursor on conclusion of step c) is dried at a temperature of less than 250° C. in order to obtain a dried catalyst precursor
Implementation Method 5
a step of heat treatment of the dried catalyst precursor obtained on conclusion of step d) is carried out at a temperature of between 250 and 1000° C.
Data Source
AI summary
A selective hydrogenation catalyst that can be obtained by the process comprising at least the following steps:a) the alumina support is brought into contact with at least one organic additive;b) the alumina support is brought into contact with at least one nickel metal salt, the melting point of said metal salt of which is between 20° C. and 150° C.;c) the solid mixture obtained on conclusion of steps a) and b) is heated with stirring;d) the catalyst precursor on conclusion of step c) is dried;e) a step of heat treatment of the dried catalyst precursor obtained on conclusion of step d) is carried out.