Cobalt Catalyst Precipitation via pH Control
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Solution Overview
Problem
Current Fischer-Tropsch catalysts face limitations in achieving high cobalt loading and activity, particularly in commercial-scale production, due to restricted pore volume and solubility of cobalt salts, which necessitates multiple impregnation steps and compromises on catalyst performance.
Innovation Solution
A process involving the mixing of aqueous solutions containing carbonate ions and cobalt ions, with optional promoter metal compounds, to form a precipitate of crystalline Co(OH)(CO3)0.5, maintaining pH between 6.5 and 8.5 and temperature between 50 and 85°C, which is then used to create a catalyst with a high surface area, allowing for improved cobalt distribution and activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pore impregnation of a porous carrier with soluble cobalt salts is used, then the catalyst preparation is simple, but the maximum cobalt loading is restricted by pore volume and solubility
Solution Approach 1:
The invention changes the chemical parameters of the impregnation process by using soluble carbonate salts and controlling pH to form cobalt carbonate precipitates in situ. This allows cobalt loading to exceed the pore volume limitation of traditional solubility-based impregnation, achieving up to 50 wt% or higher cobalt content while maintaining a simple one-step preparation process.
Solution Approach 2:
The invention utilizes phase transition from soluble carbonate salts to insoluble cobalt carbonate precipitates during the impregnation process. By controlling pH and temperature, cobalt carbonate forms as a precipitate that can be loaded at high concentrations without being limited by the pore volume of the carrier, thus resolving the contradiction between preparation simplicity and cobalt loading quantity.
2Quantity of substance
If multiple impregnation steps are used to achieve desired cobalt quantity, then cobalt loading increases, but process complexity and time increase
Solution Approach 1:
The invention merges multiple impregnation steps into a single step by using a carbonate salt solution that simultaneously provides both the cobalt source and the precipitating agent. This one-step process achieves high cobalt loading without requiring sequential impregnation cycles, thereby reducing process complexity while maintaining high cobalt quantity.
Solution Approach 2:
The invention performs preliminary action by pre-adjusting the pH of the carbonate salt solution to the optimal range (6.5-8.5) before impregnation. This ensures that cobalt carbonate precipitates form immediately and uniformly during the single impregnation step, eliminating the need for multiple steps to achieve desired cobalt quantity.
3Quantity of substance
If multiple impregnation steps are used to achieve desired cobalt quantity, then cobalt loading increases, but production time increases
Solution Approach 1:
The invention combines multiple impregnation operations into a single impregnation step using carbonate salt solutions. This reduces the total processing time and increases catalyst production rate while achieving the desired high cobalt quantity through in situ precipitate formation.
Solution Approach 2:
The invention ensures continuous useful action by maintaining optimal pH and temperature conditions throughout the single impregnation step, allowing cobalt carbonate to precipitate and load continuously onto the carrier. This continuous process eliminates idle time between multiple impregnation steps, thereby increasing productivity while achieving high cobalt loading.
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 resulting catalyst exhibits enhanced activity and selectivity for C5+ hydrocarbons, with small needle-shaped crystals providing a high surface area for effective reactant contact, surpassing the performance of prior art catalysts.
Implementation Method 1
A process involving the mixing of aqueous solutions containing carbonate ions and cobalt ions, with optional promoter metal compounds, to form a precipitate of crystalline Co(OH)(CO3)0.5
Implementation Method 2
the pH of the mixture of step (a) during mixing is maintained within the range of 6.5 to 8.5 and the temperature of the water, first and second aqueous solution and the mixture obtained in step (a) is maintained within the range of 50 and 85 degrees Celsius
Data Source
AI summary
The present invention is directed to the preparation of a cobalt containing catalyst, a precipitate as an intermediate product, a Fischer-Tropsch catalyst and a process for producing normally gaseous, normally liquid and optionally normally solid hydrocarbons from synthesis gas. The precipitate and catalyst comprise crystalline Co(OH)(CO3)0.5, the crystals are needle shaped and have a surface area of at least 80 m2/g dry precipitate.