Metal-Enriched Colloidal Silica via Preliminary Action
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Solution Overview
Problem
Conventional methods for incorporating metals into siliceous colloidal compositions face challenges such as inefficient dispersion, stability issues over a wide pH range, and difficulties in recycling catalysts, leading to decreased catalytic activity and increased synthesis time.
Innovation Solution
A method involving mixing metal salts with a silicic acid solution, followed by addition to a basic heel solution to form colloidal silica particles, with subsequent concentration and reduction of metal particles using a reducing agent, such as hydrazine or hydrogen gas, to achieve homogeneous dispersion and enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal salts are added to porous silica support via impregnation, then metal particles are incorporated onto the support, but metal particles migrate and sinter during reduction, decreasing catalytic activity
Solution Approach 1:
The patent applies preliminary action by incorporating metal particles into the silica support during the colloidal synthesis process itself, before the support structure is fully formed. This is achieved by adding metal salts to the silicic acid solution prior to addition of the basic heel solution, ensuring metal particles are trapped within the forming colloidal matrix rather than being added afterward where they would migrate and sinter
Solution Approach 2:
The patent uses the colloidal silica formation process as an intermediary mechanism to disperse metal particles. The silicic acid solution and basic heel solution react to form colloidal particles that incorporate metal salts during their formation, acting as a mediator that distributes metal particles uniformly throughout the support structure during synthesis rather than through subsequent impregnation
2Productivity
If synthesis time is reduced for immobilized catalyst production, then productivity increases, but metal particle dispersion becomes non-uniform, decreasing catalytic efficiency
Solution Approach 1:
The patent merges the catalyst synthesis and support formation processes into a single integrated colloidal synthesis step. By combining metal salt incorporation with silica colloidal particle formation, the method eliminates separate impregnation and drying steps required by conventional methods, achieving both high productivity and uniform dispersion simultaneously through one process
3Quantity of substance
If conventional silica colloid coating with metal oxide is performed, then metal coating is achieved, but particle size distribution broadens and stability over pH range decreases
Solution Approach 1:
The patent applies preliminary action by incorporating metal particles into the colloidal particles during the synthesis process itself, rather than coating them afterward. This ensures metal particles are embedded within the colloidal matrix from the beginning, creating a more stable structure that maintains narrow particle size distribution and pH stability compared to post-synthesis coating methods
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 metal-rich colloidal silica particles with a narrow particle size distribution and improved stability, facilitating efficient catalyst recycling and cost-effective production.
Implementation Method 1
reducing the incorporated metal particles with a reducing agent
Implementation Method 2
The blend is added to a basic heel solution for form colloidal silica particles in a suspension
Data Source
AI summary
A modified sol-gel method to create metal-rich siliceous material, such as colloidal silica or aluminosilicate particles is disclosed. Initially, the metal salt of choice is added to a silicic acid solution or a silicic acid solution containing aluminum salt. The aluminum is added to vary the metal-support interaction as it forms Al-O-Si linkages within the silica matrix. Besides aluminum, other metals can be added that form M-O-Si (M = Ti, B, etc.) linkages, which do not become reduced when treated with a reducing agent. Once the metal, silicic acid and/or aluminum salt is generated, it is subjected to colloidal growth by addition to a basic heel. Upon colloidal synthesis, the metal salt containing colloidal particle is left as is to maximize colloidal stability or is reduced with hydrazine to produce the zero valence metal-containing colloidal particle. Keeping a particle colloidal before use may be an effective method of forming a catalyst material as it can be easily spray-dried or mixed with other materials for extruded catalyst particles.