Cobalt Catalyst Drying for Fischer-Tropsch Synthesis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cobalt-based Fischer-Tropsch catalysts suffer from poor cobalt distribution and the formation of a crust, leading to reduced selectivity and activity in hydrocarbon synthesis, particularly in slurry processes where mechanical stress and attrition are significant, and in fixed bed processes where reagent accessibility is limited.
Innovation Solution
A catalyst preparation process involving impregnation, drying at a temperature below 100°C with a controlled temperature ramp, and calcination at specific temperatures and ramp rates to ensure homogeneous cobalt distribution and prevent crust formation, using a silica-alumina support with a spinel structure and additional elements like ruthenium or rhenium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional impregnation and drying methods are used, then the catalyst preparation is simple, but cobalt distribution becomes non-homogeneous with crust formation
Solution Approach 1:
The patent applies parameter changes by precisely controlling drying temperature (60-100°C) and temperature ramp rate (0.3-1.2°C/min) to achieve homogeneous cobalt distribution. This controlled parameter approach prevents crust formation while maintaining preparation simplicity, directly resolving the contradiction between manufacturing precision and process complexity.
2Reliability
If cobalt is aggregated on the surface to increase active sites density, then surface activity is improved, but reagent accessibility is reduced
Solution Approach 1:
The patent applies local quality by achieving homogeneous cobalt distribution throughout the catalyst grain rather than concentrating it on the surface. This creates uniform catalytic activity throughout the catalyst volume while maintaining good reagent accessibility, resolving the contradiction between catalyst activity and reagent accessibility.
3Strength
If cobalt is strongly aggregated at the periphery, then mechanical strength is improved, but selectivity is reduced due to steric constraints
Solution Approach 1:
The patent applies homogeneity by distributing cobalt uniformly throughout the catalyst grain structure. This homogeneous distribution prevents steric constraints that would limit hydrocarbon chain growth, maintaining high C5+ selectivity while providing sufficient mechanical strength through uniform metal distribution.
4Productivity
If drying is performed at higher temperature to remove water faster, then drying time is reduced, but cobalt crust formation is promoted
Solution Approach 1:
The patent applies parameter changes by optimizing the combination of drying temperature (60-100°C) and time (2-15h) with controlled ramp rates. This parameter optimization achieves sufficient water removal while preventing crust formation, resolving the contradiction between drying speed and cobalt distribution homogeneity.
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 results in improved cobalt distribution and selectivity for C5+ and alpha paraffin activity, reducing the formation of crust and enhancing the catalyst's performance in both slurry and fixed bed reactors by maintaining cobalt homogeneity and preventing aggregation.
Implementation Method 1
a drying step carried out at a temperature below 100°C, with a temperature ramp of between 0.3°C/min and 1.2°C/min, a gas flow rate of between 0.5 and 6 Nl/(h.g of catalyst), a pressure equal to 0.1 MPa and for a period of between 2h and 15h
Implementation Method 2
a calcination step
Implementation Method 3
a step of impregnation of the support
Data Source
Figure 1a~2b
Figure 3a~3b
AI summary
The present invention relates to a catalyst for carrying out the synthesis of hydrocarbons from a mixture comprising carbon monoxide and hydrogen, the active phase of which comprises at least one metal from group VIII deposited on a support formed of at least one oxide, wherein said group VIII metal is selected from the group consisting of cobalt, nickel, ruthenium or iron, and said catalyst has an atomic ratio measured by X-ray photoelectron spectroscopy: (Co/Al)unground / (Co/Al)ground of between 1 and 12. The invention also relates to the process of preparing the catalyst and its use.