What is the Eley-Rideal mechanism and how does it differ from other surface reaction mechanisms?

The Eley-Rideal mechanism involves a reaction between a gas-phase molecule and a species adsorbed on a surface, directly forming products. It differs from other surface reaction mechanisms, like the Langmuir-Hinshelwood mechanism, where both reactants are adsorbed on the surface before reacting.

What are the practical applications of the Eley-Rideal mechanism in modern technology?

The Eley-Rideal mechanism, involving direct reaction of gas-phase species with adsorbed atoms on surfaces, is utilized in industrial catalysis processes, notably in the synthesis of ammonia (Haber-Bosch process), catalytic combustion, and in surface reactions for semiconductor manufacturing. It aids in improving reaction efficiency and reducing energy consumption.

What are the key factors affecting the efficiency of the Eley-Rideal mechanism in catalytic reactions?

The key factors affecting the efficiency of the Eley-Rideal mechanism in catalytic reactions include the surface coverage of adsorbates, the reactivity of the gas-phase reactants, the surface energy of the catalyst, and the ability of the catalyst to facilitate direct interactions between gaseous reactants and adsorbed species.

How does the Eley-Rideal mechanism influence reaction rates in heterogeneous catalysis?

The Eley-Rideal mechanism influences reaction rates in heterogeneous catalysis by allowing gas-phase reactants to directly collide with and react at active sites on the catalyst surface. This can increase reaction rates as it bypasses the adsorption step required in other mechanisms, like Langmuir-Hinshelwood, under certain conditions.

Who were the scientists behind the discovery of the Eley-Rideal mechanism, and what was their contribution to the field?

The Eley-Rideal mechanism was discovered by Sir D. D. Eley and Eric Rideal. Their contribution provided a model for gas-surface reactions where a gas-phase atom or molecule directly reacts with an adsorbed species on a surface, offering significant insights into heterogeneous catalysis processes.

What is the main feature of the Eley-Rideal mechanism?

Direct interaction between a gas-phase and adsorbed molecule.

Which of the following is an example of the Eley-Rideal mechanism?

Catalytic assistance without involving gas-phase molecules

What does the rate law for the Eley-Rideal mechanism describe?

The diffusion process of gas molecules on a surface.

In which industry does the Eley-Rideal mechanism play a significant role?

Telecommunications industry for signal enhancement

What common mistake may occur in the derivation of the Eley-Rideal mechanism?

Focusing only on the forward reaction neglects intermediate species formation.

Eley-Rideal Mechanism: Rate Law & Derivation

Eley-Rideal mechanism

The Eley-Rideal mechanism is a unique reaction pathway in surface chemistry where a gas-phase reactant directly interacts with an adsorbed species on a solid surface to form a product. This allows for a single-step process, distinct from the Langmuir-Hinshelwood mechanism, and often involves reactions on catalysts such as metal surfaces. Understanding the Eley-Rideal mechanism is crucial for optimizing industrial catalytic processes and designing efficient catalyst materials.

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Eley-Rideal Mechanism Definition

Eley-Rideal mechanism is a type of catalytic reaction that is key in the study of heterogeneous catalysis. This mechanism involves a reaction occurring directly between a gas-phase atom or molecule and an adsorbed atom or molecule on a surface.

Understanding the Eley-Rideal Mechanism

To gain a comprehensive understanding of the Eley-Rideal mechanism, you need to consider its unique approach to reactions on surfaces. The process can be simplified as: - A gas-phase molecule approaches a surface where it encounters an adsorbed molecule or atom. - The gas-phase molecule directly reacts with this adsorbed species, often leading to the formation of a new molecule. - The newly formed molecule is then either released into the gas phase or stays adsorbed on the surface. This mechanism is unique because it does not require the gas-phase molecule to first become adsorbed on the surface, which simplifies reaction dynamics. The mathematical expression of the Eley-Rideal reaction rate can be given by the formula: \[ R = k \theta_A P_B \] where: - R is the reaction rate. - k is the rate constant. - \(\theta_A\) represents the coverage of adsorbate A. - \(P_B\) is the partial pressure of the gas-phase species B.This formula highlights that the reaction rate depends on both the surface coverage and the partial pressure of the gas-phase molecule.

The Eley-Rideal mechanism is different from the Langmuir-Hinshelwood mechanism, where both reactants get adsorbed on the surface before reacting.

Key Features of the Eley-Rideal Mechanism

Key features of this mechanism make it pivotal in various applications. Understanding these aspects strengthens your grasp of surface chemistry:

Direct Interaction: The most highlighting feature is the direct reaction between a gas-phase species and an adsorbed species on a surface, which bypasses the need for both molecules to be adsorbed.
Surface Dynamics: The mechanism is sensitive to the nature of the surface and the adsorbed species, often leading to varied reaction pathways.
Speed and Efficiency: Since it does not necessitate adsorption-desorption equilibria for both reactants, reactions can proceed at a faster rate under suitable conditions.
Applications: This mechanism is crucial in fields such as catalysis involving gases, like in some types of synthetic ammonia production or automotive exhaust catalysis.

Such distinctive features rely on the kinetic energies and orientations of the involved molecules, making the Eley-Rideal mechanism highly valuable for theoretical and experimental research in surface and catalytic chemistry.

An example is the reaction of hydrogen gas (H2) with an adsorbed oxygen atom (O) on a metal surface, forming water (H2O). In this case, H2 approaches the surface, collides directly with O, and produces H2O.

Eley-Rideal Mechanism Rate Law

The Eley-Rideal mechanism rate law is an essential aspect of understanding the kinetics of surface reactions where a gas-phase molecule directly reacts with an adsorbed species. The rate law provides insights into how different factors influence the speed of these reactions.

Deriving Eley-Rideal Mechanism Rate Law

Deriving the rate law for the Eley-Rideal mechanism involves considering the interactions at the surface and the gas-phase. The formulation is straightforward, hinging on the interaction between a gas-phase molecule and an adsorbed species.To derive the rate law:

Identify the adsorbed species as \( A_s \)
Identify the gas-phase molecule as \( B_g \)
React to form a product: \( A_s + B_g \rightarrow C \)

The rate can be represented as: \[ R = k \theta_A P_B \]Here, \( \theta_A \) represents the surface coverage of the adsorbed species, and \( P_B \) is the partial pressure of the gas-phase molecule. The constant \( k \) is the rate constant, influenced by the temperature and the nature of the catalyst's surface.

Understanding the molecular dynamics and energy transfer in the Eley-Rideal mechanism can also involve Monte Carlo simulations or molecular dynamics, where computational models simulate the actual pathways of molecules during the reaction.

Factors Affecting Eley-Rideal Mechanism Rate Law

Several factors influence the rate of reactions in the Eley-Rideal mechanism, affecting both the surface coverage and the interaction rate. Consider these key factors:

Surface Coverage: The rate depends on \( \theta_A \), the fraction of surface covered by the adsorbed species. Greater coverage can lead to higher reaction rates, as more sites are available for interaction.
Partial Pressure: The gas-phase reactant's partial pressure \( P_B \) is crucial. Increased pressure generally enhances the probability of collision and reaction with the adsorbed species.
Temperature: Higher temperatures often increase the rate constant \( k \), leading to faster reactions. However, optimal temperatures vary depending on the specific reaction and catalyst involved.
Catalyst Surface: The nature of the catalyst's surface affects adsorption energy and orientation of the adsorbed molecules, significantly impacting reaction rates.

To understand these influences quantitatively, consider the rate equation and its components as a function of temperature through the Arrhenius equation:\[ k = A e^{-\frac{E_a}{RT}} \]Where:

\( A \) is the pre-exponential factor.
\( E_a \) is the activation energy.
\( R \) is the universal gas constant.
\( T \) is the temperature in Kelvin.

Eley-Rideal Mechanism Derivation

The derivation of the Eley-Rideal mechanism is crucial for understanding the dynamics of surface reactions where gas-phase molecules interact directly with adsorbed species. This reaction mechanism bypasses the need for the gas molecule to first adsorb onto the surface before reacting.

Step-by-Step Eley-Rideal Mechanism Derivation

To derive the mechanism of the Eley-Rideal process, follow these steps:

Identify a reactant A adsorbed on a surface and a gas-phase molecule B.
Consider the main reaction: \( A_s + B_g \rightarrow C \)
Recognize that the rate of reaction is proportional to the surface coverage \( \theta_A \) and the partial pressure \( P_B \).
The rate law can be expressed as: \[ R = k \theta_A P_B \]
Here, \( k \) is the rate constant that encompasses the surface's catalytic properties and reaction conditions.
The temperature dependence of \( k \) can be described by the Arrhenius equation: \[ k = A e^{-\frac{E_a}{RT}} \]

Understanding each component in this derivation helps explain how such reactions occur without the adsorption equilibrium that is typical in other surface reactions.

In a typical research scenario, the derivation and validation of an Eley-Rideal mechanism are supported by spectroscopic techniques such as infrared or Raman spectroscopy. These techniques provide insight into surface-adsorbed species and reaction intermediates, validating theoretical models with experimental data.

Pay attention to the environmental conditions in which Eley-Rideal reactions occur, as they often differ from those favoring other catalytic mechanisms.

Common Mistakes in Eley-Rideal Mechanism Derivation

When deriving the Eley-Rideal mechanism, several errors can arise. Understanding these helps in correctly applying the principles to various reaction systems:

Ignoring Surface Coverage: Failing to account for the importance of \( \theta_A \) can lead to inaccurate calculations of the reaction rate.
Misusing Partial Pressure: Overlooking the role of \( P_B \), or assuming it remains constant without considering the reaction environment, can skew results.
Overlooking Temperature Effects: Underestimating how temperature variations affect \( k \) can significantly impact the understanding of reaction kinetics.
Assuming All Reactions Are Eley-Rideal: Confusing this mechanism with others like Langmuir-Hinshelwood can result in incorrect application.
Ignoring Reverse Reactions: Some systems may also have significant backward reactions, which should be considered in comprehensive kinetic modeling.

Recognizing these common mistakes ensures more precise modeling and prediction of reaction behaviors using the Eley-Rideal mechanism.

Eley-Rideal Mechanism Examples and Applications

The Eley-Rideal mechanism provides a fascinating perspective on direct interactions in catalytic reactions. Understanding practical examples and industrial applications can deepen your knowledge of how this mechanism plays a vital role in various processes.

Practical Examples of Eley-Rideal Mechanism

Practical examples of the Eley-Rideal mechanism illustrate its unique approach to heterogeneous catalysis. Here are some elucidated cases:

The reaction between hydrogen gas (H₂) and adsorbed oxygen (O) on a metal surface to form water (H₂O) is a classic example where the gas-phase hydrogen directly reacts with the adsorbed oxygen.
In respiratory catalysis, gas-phase nitric oxide (NO) can react with adsorbed oxygen on a platinum surface to produce NO₂, playing a part in exhaust emission control.
The interaction of gaseous ethylene (C₂H₄) with adsorbed chlorinated species on certain catalysts opens pathways for the synthesis of valuable chlorinated compounds.

These examples showcase how direct interactions significantly affect reaction kinetics and product formation.

Consider the interaction between gaseous nitrogen monoxide (NO) and adsorbed oxygen on rhodium surfaces. The reaction forms nitrogen dioxide (NO₂), crucial in automotive catalytic converters for reducing harmful emissions.

Applications of Eley-Rideal Mechanism in Industry

The Eley-Rideal mechanism finds extensive applications across various industries, particularly where surface-mediated reactions are pivotal.

Automotive Industry: This mechanism is instrumental in designing catalytic converters that reduce vehicle emissions. It facilitates rapid conversion of pollutants like NO_x into less harmful substances.
Chemical Manufacturing: In synthetic ammonia production, using Haber processes, the Eley-Rideal mechanism aids in the effective breaking of N₂ bonds on metal catalysts.
Environmental Engineering: It plays a role in designing processes for detoxifying industrial effluents by catalytically reacting gas-phase pollutants with surface-bound species.

Industrial catalysts leveraging the Eley-Rideal mechanism are designed for specific reactions, enhancing their efficiency and desired outcomes.

The exploration of Eley-Rideal reactions at the nanoscale includes the study of single-atom catalysts. These catalysts, capable of performing high-efficiency reactions at low temperatures, offer exciting prospects in energy storage and conversion technologies.

Eley-Rideal Mechanism Assumptions and Their Implications

Certain assumptions underlie the functioning of the Eley-Rideal mechanism, affecting its theoretical and practical application in catalytic science.

Direct Interaction Assumption: It is presumed that the gas-phase molecule reacts directly with the adsorbed species, which simplifies kinetic models but may not account for intermediate adsorption steps in some systems.
Constant Surface Condition: Assumes uniform surface conditions, which may overlook variations in surface energy impacting reaction rates.
Ideal Gas Interactions: The model typically assumes ideal behavior, which can differ from real-world scenarios involving complex multicomponent systems.

The implications of these assumptions are profound, as they guide the development of reaction models and influence the design of industrial catalysts.

Understanding the Eley-Rideal mechanism helps in developing new materials with tailored surface properties for enhanced catalytic performance.

Eley-Rideal mechanism - Key takeaways

Eley-Rideal Mechanism Definition: A catalytic mechanism involving direct reactions between gas-phase and adsorbed species, bypassing gas adsorption.
Rate Law: Expressed as R = k θ_A P_B, where R is the reaction rate, k is the rate constant, θ_A is adsorbate coverage, and P_B is gas-phase species pressure.
Mechanism Derivation: Involves deriving the reaction rate from the interaction between an adsorbed species and a gas-phase molecule.
Key Assumptions: Assumes direct interaction, constant surface condition, and ideal gas interactions.
Examples: Reaction of hydrogen gas with adsorbed oxygen on metal surfaces, used in synthetic ammonia production and exhaust catalysis.
Applications: Utilized in automotive catalytic converters, chemical manufacturing, and environmental engineering for pollutant reduction.

Eley-Rideal mechanism

StudySmarter Editorial Team