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Title of Thesis

Transient Non-Thermal Mobility In Surface Subsurface Heterogeneous Catalytic Reaction: Computer Simulation

Author(s)

ABAID ULLAH QAISRANI

Institute/University/Department Details
Department Of Physics / Gomal University, Dera Ismail Khan
Session
2008
Subject
Physics
Number of Pages
130
Keywords (Extracted from title, table of contents and abstract of thesis)
Transient, Non-Thermal, Mobility, Surface, Subsurface, Heterogeneous, Catalytic Reaction, Computer Simulation, Langmuir-Hinshelwood

Abstract
To study the effect of transient non-thermal mobility in surface-subsurface heterogeneous catalytic reaction, simulation work has been done for CO-O2 and CO-NO catalytic reaction on different surfaces. One class of transient non-thermal mobility of species includes Ely-Rideal (ER) mechanism. The first simple lattice gas model was introduced by Ziff, Gulari and Barshad, as a computer simulation model and is known as the ZGB model, which was used to study CO- O2 reaction system. It has been found through simulation that ER mechanism generates features in the ZGB model that brings it closer to the real system. The Consideration of ER mechanism annihilates second order phase transition of the ZGB model and the reaction rate begins to increase as soon as feed concentration CO departs from zero, which is consistent with the experimental results. The other class of transient non-thermal mobility is precursor mechanism. This mechanism adds some additional features in the phase diagram of a particular catalytic reaction, which could not be observed by considering the Langmuir-Hinshelwood mechanism. In the precursor mechanism, three different ranges of the surface environment have been investigated. Each environment consists of specific pattern for set of sites around the striking site. It is observed that the reactive window depends on the mobility of the precursors. It is also observed that when the probability of the precursor is increased, the production rates increases. Furthermore, the simulation is also performed to investigate the effect of diffusion of CO on the ZGB model. It has been found that the effect of diffusion of CO on the ZGB model is to increase the mobility of CO on the surface and hence the reaction rate increases with the result that the transition point y2 shifts towards higher concentration of CO. However, the effect of diffusion of CO has no effect on the second order phase transition point y1. The effect of diffusion of CO and N (atom) for CO-NO catalytic reaction has also been studied on BCC lattice. The effect of diffusion of CO and N on the production rates is found in the high concentration of CO. This mechanism is found responsible for slight increase in the window width where the concentration of CO is high. Through these models some experimental results have been reproduced of the real system.

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1,089 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 CONTENTS

 

viii
86 KB
2

1

INTRODUCTION

1.1 Role of computer simulation

1.2 Importance of heterogeneous catalytic reaction (HCR)
1.3 History of the project
1.4 Aim of the project
1.5 References

1
176 KB
3 2 MONTE CARLO SIMULATION AND CATALYTIC SURFACE REACTIONS

2.1 Introduction

2.2 The Monte Carlo simulation method
2.3 References
 

15
127 KB
4 3 SURFACE CATALYTIC REACTIONS (SCR)

3.1 Introduction

3.2 Elementary steps in surface reaction
3.3 Catalytic Reaction mechanisms
3.4 Basic Modelling of SCR
3.5 Variants of ZGB Model

3.6 References

23
212 KB
5 4 SIMULATION OF CO-O2 REACTION

4.1 Introduction

4.2 Simulation on simple cubic lattice (SCL) with ER
4.3 Simulation on BCC with ER

4.4 Simulation on SCL with Ballistic-Type Hot Atom

4.5 References

39
415 KB
6 5 SIMULATION OF CO-NO REACTION

5.1 Introduction

5.2 Simulation on square surface with Precursor mechanism
5.3 Simulation on square surface with Precursor and diffusion mechanism

5.4 Simulation on BCC for CO-N0 with Precursor mechanism

5.5 Simulation on BCC with Eley Rideal and diffusion mechanism

5.6 References

63
623 KB
7 6 RESULTS AND CONCLUSION

6.1 Conclusion

6.2 Future Research Work
 

109
93 KB