The improvement of activity and stability of precipitated silica (silicon dioxide) as a catalyst support mainly depends on surface chemical modification and structural engineering. Based on existing research, the core strategies can be summarized into the following technical approaches:

Activity Enhancement Mechanisms
Surface Silanization Modification: Through the condensation reaction between silane coupling agents (such as KH550, Si69) and the silanol groups (Si–OH) on the surface of precipitated silica, polar hydroxyl groups are eliminated, reducing surface energy, thereby improving the impregnation uniformity and dispersion of active metal precursors, and increasing the number of effective active centers.
Composite Oxide Support Design: Constructing composite supports such as SiO₂-TiO₂ and SiO₂-Al₂O₃, utilizing the acidity, basicity, or electronic effects of metal oxides to regulate the electronic structure of active components (such as Pt, Ru), and enhancing the adsorption and activation capabilities of reactants. For example, lithium ion doping can significantly improve the dispersion of Ru and the CO₂ methanation activity on Ru/SiO₂ catalysts.
Pore Structure and Specific Surface Area Optimization: Using template methods or sol-gel methods to control the mesoporous structure, improving mass transfer efficiency, making it easier for reactants to contact active sites, and indirectly improving intrinsic activity.
Stability Enhancement Strategies
Anti-sintering and Thermal Stability Improvement:
Surface Coating: Using polydimethylsiloxane (PDMS) or silazanes (such as hexamethyldisilazane) to hydrophobically coat the surface of precipitated silica, forming a physical barrier to inhibit the migration and aggregation of metal particles at high temperatures.
Core-Shell Structure Construction: Coating a dense SiO₂ or metal oxide shell layer on the precipitated silica core to physically isolate the active components and effectively block the sintering pathway.
Chemical Bonding Stabilization: Using silane coupling agents to form a stable Si–O–Si network on the support surface, enhancing the mechanical strength and corrosion resistance of the support, suitable for acidic or hydrothermal reaction environments. High-Stability Inhibitor Modification: Functional modification of fumed silica with alkynyl alcohol compounds can serve as a highly effective inhibitor in platinum-based catalytic systems, significantly improving the storage stability and long-term catalytic durability of silicone rubber systems.
Comparison of Mainstream Modification Technologies
Modification Method | Example of Modifying Agent | Mechanism of Action | Advantages | Limitations
Silane Coupling Agent Modification | KH550, Si69, A151 | Chemical bonding replaces Si–OH, reducing surface polarity | Significant modification effect, industrially mature | High cost, requires precise control of dosage
Organic Halosilane Treatment | Trimethylchlorosilane | Chlorosilane hydrolysis and condensation to form a hydrophobic layer | Simple process, strong hydrophobicity | May leave residual chloride ions, affecting catalytic selectivity
Surface Grafted Polymers | Polystyrene, Polycaprolactone | Grafting polymer brushes onto the surface, steric hindrance stabilization | Precise control of surface properties | Complex synthesis, cumbersome steps
Composite Oxide Loading | TiO₂, Al₂O₃ | Construction of heterogeneous interface, electronic modulation | Synergistic improvement of activity and thermal stability | Complex preparation process, requires control of molar ratio
Industrial Application Trends
Currently, the industry prioritizes dry silanization processes because they are compatible with the gas-phase fumed silica production process, easy to scale up, and have simple post-processing. In high-end catalytic fields, such as hydrogenation, dehydration, and photocatalytic reactions, core-shell structured SiO₂ carriers and inhibitor-functionalized fumed silica are becoming key directions for improving catalyst lifespan.