Chromium Oxyfluoride Catalyst via Reactive Milling
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Solution Overview
Problem
Existing methods for producing chromium oxide-based catalysts, such as co-precipitation, are limited by solubility, lead to heterogeneous compositions, and consume significant water and energy, resulting in catalysts with poorly developed surfaces and reduced catalytic performance.
Innovation Solution
A method involving reactive grinding of chromium oxide compounds with specific second reactants, followed by a fluorination step using a fluorinating agent, to produce chromium oxyfluoride catalysts with controlled chromium oxidation states, allowing for flexible composition modulation and improved surface development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If co-precipitation method is used to prepare chromium oxide-based catalysts, then the catalyst composition can be adjusted, but the composition becomes heterogeneous and specific surface area is reduced
Solution Approach 1:
The patent replaces the chemical precipitation process with a mechanical grinding process (mechanochromism). The reactive milling mechanically activates the chromium oxide and reacts it with gaseous HF to form chromium oxyfluoride catalysts, eliminating the need for aqueous co-precipitation while achieving homogeneous composition and high specific surface area.
Solution Approach 2:
The patent changes the physical and chemical parameters of the preparation process by using solid-state reactive milling instead of aqueous precipitation. This involves changing from liquid-phase chemical reactions to solid-state mechanochemical reactions, controlling chromium oxidation states (Cr3+, Cr4+, Cr5+), and using gaseous HF instead of aqueous fluorine sources to achieve superior catalyst properties.
2Ease of manufacture
If traditional precipitation and calcination methods are used, then catalysts can be produced, but significant amounts of water and energy are consumed
Solution Approach 1:
The patent replaces thermal calcination with mechanical activation followed by low-temperature fluorination. Instead of high-temperature calcination of precipitates, the method uses reactive milling to mechanically activate chromium oxide and then reacts it with gaseous HF at lower temperatures, dramatically reducing energy consumption while eliminating water usage.
Solution Approach 2:
The patent uses gaseous HF delivered through a fluidized bed reactor instead of aqueous solutions. The gaseous fluorinating agent flows through the mechanically activated chromium oxide powder, enabling the reaction without liquid water and reducing the need for subsequent drying and washing steps that consume energy.
3Ease of manufacture
If conventional preparation methods are used, then catalysts can be produced, but the specific surface area is poorly developed limiting catalytic performance
Solution Approach 1:
The patent uses intensive mechanical vibration and impact during reactive milling to fracture and redisperse the chromium oxide particles. The high-energy milling process creates fresh surfaces and prevents particle agglomeration, resulting in catalysts with high specific surface area and well-developed porous structures that enhance catalytic activity.
Solution Approach 2:
The reactive milling process inherently creates porous structures in the chromium oxyfluoride catalyst by mechanical fracturing and preventing dense sintering. The resulting material has high porosity and large specific surface area, which are critical for catalytic performance, without requiring additional porous structure development steps.
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 enhances catalytic performance by achieving a higher degree of oxidation control, reducing energy consumption, and enabling the recycling of used catalysts, while avoiding aqueous waste and promoting industrial scalability.
Implementation Method 1
The invention relates to the mechanochromism of chromium oxide compounds
Implementation Method 2
a fluorination step is carried out by contacting the material with a fluorinating agent
Data Source
AI summary
The invention relates to a process for preparing a catalyst, comprising the reactive milling of a first reagent, which is a chromium oxide compound, with a second reagent, which is a compound of the formula MzM'1-zOxFy, M and M' each being an element having an oxidation state greater than or equal to 0, z being from 0 to 1, x being from 0 to 3, y being from 0 to 6, and 2x+y being greater than 0 and less than or equal to 6.