Cobalt Catalyst Preparation via Two-Step Decomposition
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Solution Overview
Problem
Existing cobalt-containing catalysts for the Fischer-Tropsch hydrocarbon synthesis process face challenges in achieving highly dispersed, small particle-size cobalt with homogeneous nanoscale distribution, often requiring expensive promoter metals like rhenium and relying on NO and He gases for particle formation.
Innovation Solution
A method involving a two-step decomposition protocol for cobalt nitrate on a titania or silica support, with partial decomposition at 160°C in an oxygen-containing atmosphere followed by hydrolysis and reduction, achieves highly dispersed cobalt crystallites with a surface-volume-averaged diameter of 11 nm or less, using minimal rhenium (0.01 wt % to 0.2 wt %) without NO and He gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional incipient wetness method with rhenium promoter is used, then cobalt dispersion and catalytic activity are improved, but catalyst cost increases due to expensive rhenium
Solution Approach 1:
The patent extracts and eliminates the need for expensive rhenium promoter by using a two-step decomposition protocol that achieves cobalt dispersion through controlled thermal decomposition of cobalt nitrate at 160°C followed by reduction, achieving similar catalytic performance without the costly promoter metal
Solution Approach 2:
The patent replaces expensive rhenium promoter with a cost-effective two-step decomposition process using common reagents (cobalt nitrate, water, hydrogen atmosphere), achieving the desired cobalt dispersion and catalytic activity through a disposable, low-cost preparation method
2Manufacturing precision
If NO and He gases are used for nitrate decomposition, then small cobalt particle formation is achieved, but process complexity and cost increase
Solution Approach 1:
The patent removes the complex NO and He gas mixture requirement by implementing a simpler two-step decomposition protocol: first step decomposes cobalt nitrate to cobalt oxide at 160°C in air, second step reduces cobalt oxide to metallic cobalt in hydrogen atmosphere, achieving precise particle size control without complex gas systems
Solution Approach 2:
The patent segments the decomposition process into two distinct steps: oxidation step (cobalt nitrate to cobalt oxide) and reduction step (cobalt oxide to metallic cobalt), allowing independent control of each step and simplifying the overall process compared to single-step decomposition requiring NO and He gases
3Quantity of substance
If cobalt crystallite size is reduced below 6 nm, then surface cobalt sites increase, but site activity decreases
Solution Approach 1:
The patent optimizes the cobalt crystallite size parameter by controlling the two-step decomposition process to achieve particle sizes in the optimal range (6-11 nm), balancing the number of surface sites with the activity of each site, and avoiding the detrimental effects of particles that are too small (<6 nm) or too large
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
This approach results in a highly active cobalt catalyst with improved nanoscale homogeneity and reduced rhenium content, suitable for the Fischer-Tropsch process, enhancing catalytic performance while minimizing costs and environmental impact.
Implementation Method 1
heating in an oxygen-containing, substantially water-free atmosphere to about 160° C. to partially decompose the cobalt nitrate
Implementation Method 2
the intermediate product is hydrolyzed
Implementation Method 3
followed by reduction in a hydrogen atmosphere
Data Source
AI summary
A method is provided for preparing a supported cobalt-containing catalyst having substantially homogeneously dispersed, small cobalt crystallites. The method comprises depositing cobalt nitrate on a support and then subjecting the support to a two-step decomposition protocol. In the first step, the support is heated in an oxygen-containing, substantially water-free atmosphere to about 160° C. to form an intermediate decomposition product. This intermediate product is then or hydrolyzed and reduced, or hydrolyzed, calcined and reduced.