key term - Supported catalysts

Definition

Supported catalysts are catalysts that are dispersed on a support material, enhancing their activity and stability while providing a larger surface area for reactions to occur. The support material, often an inert substance, serves to improve the distribution of the active catalytic sites, allowing for more effective interaction with reactants. This setup is crucial for various catalytic mechanisms, including those that involve surface reactions.

5 Must Know Facts For Your Next Test

1. Supported catalysts typically consist of metal nanoparticles dispersed on a high-surface-area support like alumina or silica, which helps in stabilizing the catalyst.
2. The effectiveness of supported catalysts is often evaluated by their turnover frequency (TOF), which measures the rate at which a catalyst converts reactants into products.
3. Supported catalysts can facilitate complex reactions through both Langmuir-Hinshelwood and Eley-Rideal mechanisms, influencing how reactants interact on the catalyst surface.
4. The choice of support material can significantly affect the electronic and structural properties of the catalyst, thereby impacting its activity and selectivity.
5. Regeneration of supported catalysts can be achieved through various methods, including thermal treatment or chemical leaching, to restore their activity after deactivation.

Review Questions

• How do supported catalysts improve the efficiency of catalytic reactions compared to unsupported ones?
  • Supported catalysts enhance the efficiency of catalytic reactions by providing a larger surface area for reactants to interact with active sites. The support material helps to stabilize the catalyst and can improve its thermal and mechanical properties. This results in better dispersion of the active sites and more effective access for reactants, ultimately leading to higher reaction rates.
• Discuss how supported catalysts can participate in both Langmuir-Hinshelwood and Eley-Rideal mechanisms and what implications this has for their design.
  • Supported catalysts can participate in both Langmuir-Hinshelwood and Eley-Rideal mechanisms depending on how reactants adsorb onto the catalyst surface. In Langmuir-Hinshelwood, both reactants adsorb onto the catalyst before reacting, while in Eley-Rideal, one reactant adsorbs and the other reacts in the gas phase. Understanding these mechanisms is crucial for designing effective supported catalysts as it influences factors like active site density, pore structure, and overall catalytic performance.
• Evaluate the role of porosity in supported catalysts and how it affects catalytic activity in industrial applications.
  • Porosity plays a critical role in supported catalysts by providing an increased surface area that enhances catalytic activity. In industrial applications, highly porous supports allow for better diffusion of reactants into the catalyst structure, leading to improved accessibility to active sites. This is particularly important in large-scale processes where mass transfer limitations can affect overall reaction rates. Evaluating porosity also aids in optimizing catalyst designs for specific reactions to maximize efficiency and yield.

Related terms

Heterogeneous Catalysis: A type of catalysis where the catalyst is in a different phase than the reactants, often solid catalysts interacting with gaseous or liquid reactants.

Active Sites:

Specific locations on the catalyst surface where reactant molecules can bind and undergo chemical transformations.

Porosity: The property of a material that indicates the presence of voids or pores, which can enhance the surface area available for catalytic reactions.