Cobalt Catalyst Preparation Using Cyclic Oligosaccharides
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Solution Overview
Problem
Catalysts used in Fischer-Tropsch synthesis exhibit poor catalytic activity due to high and poorly controlled metal oxide crystallite sizes, particularly cobalt oxide, leading to suboptimal performance in producing hydrocarbons.
Innovation Solution
A process involving a catalyst with a metal from Group VIII, preferably cobalt, deposited on an oxide support, prepared by contacting the support with a precursor solution and a cyclic oligosaccharide like cyclodextrin, followed by calcination, resulting in smaller metal oxide crystallites and increased dispersion, enhancing catalytic activity and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional methods such as dry impregnation are used to prepare catalysts, then the preparation process is simple and easy to manufacture, but the metal oxide crystallite size becomes high and poorly controlled, resulting in poor catalytic activity
Solution Approach 1:
A macrocyclic ligand is introduced as an intermediary substance during catalyst preparation. The ligand coordinates with metal ions to form stable complexes that control crystallite growth, ensuring smaller and more uniform metal oxide crystallites while maintaining preparation simplicity
Solution Approach 2:
The preparation method is modified by changing chemical parameters - specifically by adding macrocyclic ligands and controlling their concentration and type. This parameter change transforms the crystallization process to produce smaller, more controlled crystallite sizes without complicating the overall manufacturing process
2Reliability
If organic compounds such as polyols or sugars are introduced to increase metal dispersion, then the catalytic activity improves, but the catalyst preparation process becomes more complex
Solution Approach 1:
Instead of using complex mixtures of polyols or sugars, the invention changes the chemical parameter by selecting specific macrocyclic ligands with defined structures. This simplifies the preparation process while maintaining the ability to control crystallite size and improve catalytic activity
Solution Approach 2:
The macrocyclic ligand provides localized coordination sites around metal ions, creating uniform local environments that control crystallite growth. This localized action achieves better dispersion and activity without requiring complex overall process design
3Manufacturing precision
If chelating compounds like EDTA or citric acid are used to reduce Co3O4 crystallite size, then the dispersion of cobalt improves, but the catalytic performance remains suboptimal
Solution Approach 1:
Macrocyclic ligands serve as superior intermediaries compared to conventional chelating agents. Their rigid ring structures and multiple coordination sites provide better control over metal ion arrangement, leading to both smaller crystallites and enhanced catalytic performance
Solution Approach 2:
The catalyst is prepared as a composite system combining metal precursors with macrocyclic ligands. This composite approach during preparation creates a synergistic effect where the ligand structure directs the formation of highly active metal oxide phases with optimized crystallite sizes
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 improved catalytic activity and productivity for the synthesis of linear and saturated C5+ hydrocarbons, with increased active sites and higher yields of middle distillates like diesel and kerosene.
Implementation Method 1
it has been discovered that a catalyst, the active phase of which comprises at least one metal from group VIII, particularly cobalt, and prepared in the presence of at least one organic compound formed of at least one cyclic oligosaccharide compound of at least 6 glucopyranose subunits linked in α-(1,4), preferably of a cyclodextrin, presents a dispersion of said group VIII metal significantly greater than that presented by catalysts prepared in the absence of cyclic oligosaccharide
Implementation Method 2
iii) at least one calcination step to obtain at least said metal of said group VIII under oxide form
Implementation Method 3
The subject of the present invention is a process for the synthesis of essentially linear and saturated C5+ hydrocarbons consisting of bringing a feed comprising synthesis gas into contact with at least one catalyst whose active phase comprises at least one metal from group VIII
Data Source
AI summary
The invention relates to a method for synthesizing C5+ hydrocarbons, consisting of contacting a synthesis gas with a catalyst including at least one group VIII metal deposited onto a substrate made of at least one oxide, said catalyst being prepared according to a method including at least: i) one step of contacting at least said substrate with at least one solution containing at least one precursor of said group VIII metal; ii) one step of contacting at least said substrate with at least one organic compound consisting of at least one cyclic oligosaccharide consisting of at least six glucopyranose subunits having α-(1,4) bonds; and iii) one calcination step for obtaining at least said group VIII metal in the form of an oxide, wherein steps i) and ii) can be carried out separately in any order, or simultaneously.