Layered Double Hydroxide Modification via Organic Solvent Treatment
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Solution Overview
Problem
Conventionally synthesized layered double hydroxides (LDHs) exhibit high aggregation, leading to non-porous, large particle sizes, and low specific surface areas, which limits their effectiveness in applications requiring high surface areas and mass transport efficiency.
Innovation Solution
A process involving the use of a water-miscible organic solvent, such as acetone, to treat water-wet LDHs, reducing particle aggregation and increasing surface area and pore volume, resulting in highly dispersed and porous LDHs with improved thermal characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional synthesis methods are used to produce LDHs, then the particles form aggregated stone-like bodies with large particle sizes, but the specific surface area becomes low (5 to 15 m2/g)
Solution Approach 1:
The patent applies parameter changes by controlling the synthesis conditions (pH, temperature, mixing rate) and post-synthesis treatment (drying temperature, solvent type) to transform the physical state of LDH particles from aggregated to dispersed. This results in achieving both high specific surface area and reduced particle aggregation simultaneously
Solution Approach 2:
The patent uses an intermediary substance (solvent such as acetone or ethanol) during the drying process to prevent particle aggregation. The solvent acts as a mediator that maintains particle dispersion while removing water, thereby preserving high surface area and preventing the formation of dense stone-like aggregates
2Area of stationary object
If LDHs are synthesized with high surface area, then more active sites are available, but mass transport from surface to bulk becomes more difficult
Solution Approach 1:
The patent creates porous structures within the LDH particles by controlling the drying process and using organic solvents. This introduces internal porosity that facilitates mass transport from the surface to the bulk while maintaining high specific surface area. The porous structure provides channels for reactant and product diffusion
3Shape
If LDH particles are kept wet during synthesis, then aggregation is reduced, but the particles require additional drying steps that may increase aggregation
Solution Approach 1:
The patent uses an organic solvent (acetone or ethanol) as an intermediary during the drying process. This solvent replaces water in the particle structure and prevents aggregation during drying. The solvent is then removed through evaporation, leaving behind dispersed particles with maintained surface area and reduced aggregation
Solution Approach 2:
The patent utilizes phase transitions of the drying process (liquid to vapor) to remove water and organic solvent from the particle structure. By controlling the phase change conditions (temperature, pressure), the patent prevents particle aggregation while maintaining high surface area and particle dispersion
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 modified LDHs demonstrate significantly increased specific surface areas and pore volumes, up to 301 m2/g and 2.15 cc/g respectively, along with reduced particle density, making them suitable for applications like catalyst supports and adsorbents.
Implementation Method 1
contacting the water-wet layered double hydroxide with at least one solvent, the solvent being miscible with water
Implementation Method 2
The role of the organic solvent is to strip the surface bound water from the water wet LDH particles
Data Source
AI summary
The present invention relates to a process for modifying a layered double hydroxide (LDH), the process comprising,a. providing a water-wet layered double hydroxide of formula:[Mz+1-xM′y+x(OH)2]a+(Xn−)a/r.bH2O (1)wherein M and M′ are metal cations, z=1 or 2; y=3 or 4, x is 0.1 to 1, preferably x<1, more preferably x=0.1-0.9, b is 0 to 10, X is an anion, r is 1 to 3, n is the charge on the anion X and a is determined by x, y and z, preferably a=z(1−x)+xy−2;b. maintaining the layered double hydroxide water-wet, andc. contacting the water-wet layered double hydroxide with at least one solvent, the solvent being miscible with water and preferably having a solvent polarity (P′) in the range 3.8 to 9,as well as to a layered double hydroxide prepared according to that process.