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Moessbauer Spectroscopic and Related Characterization of Fischer-Tropsch Catalysts, Annual Report - 1981

Melay, L. N.

Pennsylvania State University

In this pdf format, this document has 101 pages and is 2.79MB.

Table of Contents

Abstract iii
List of Tables vi
List of Figures vii
Acknowledgements ix
 

I

 Introduction 1
 

A

 General Background 1

B

 Research Objectives 2

C

 Outline of the Thesis 2

II

 Theoretical Aspects 4
 

A

 Mossbauer Spectroscopy 4
 

1

 History 4

2

 Isomer Shift 13

3

 Quadrupole 14

4

 Hyperfine Interaction 16

5

 Combined Magnetic and Electric Hyperfine Interaction 19

B

 Magnetic Study 19
 

1

 Diamagnetism 20

2

 Paramagnetism 21

3

 Magnetic Order 25

4

 Superparamagnetism 31

III

 Experimental Procedures 34
 

A

 Preparation of Samples 34

B

 Catalysis Reaction Studies 35

C

 Mossbauer Appartus 35

D

 Calibration and Measurements 38

E

 Analysis of Mossbauer Data 39

F

 Characterization by X-Ray Diffraction 39

G

 Magnetic Measurements 41

IV

 Results and Discussion 44
 

A

 General Introduction 44

B

 Mossbauer and Magnetic Studies on Bifunctional Medium Pore Zeolite-Fe Catalysts Used in Synthesis Gas Conversion 44
 

1

 Introduction 44

2

 Experimental 48

3

 Results and Discussion 49
 

a

 Mossbauer Studies 49

b

 Magnetic Measurements 65

4

 Conclusions 68
References 70
 

List of Tables

1

Interplanar d-spacing (A) of ZSM-5 43
2 Comparison of ZSM-5 and Silicalite 47
3 Summary of Mossbauer Results of Various Catalysts 50
4 Product compositions from the catalysts ZSM-5 (11.1% Fe) and ZSM05 (5.6% Fe, 4.5% Co), in a Berty reactor, showing the influence of cobalt addition to the catalyst 69
(I) The background information and the research objectives have been presented above
(II) Theoretical aspects of Mossbauer spectroscopy and magnetic measurements;
(III) Experimental techniques
(IV) Discussion of results obtained.
 

List of Figures
1 Nuclear resonance absorption of y-rays 6
2 Recoil of momentum Pn and energy Er imparted to an isolated nucleus upon Y-ray emission 6
3 The decay of 57 Co to stable 57 Fe 8
4 Resonant absorption is not possible since there is no overlap between emission and adsorption line 9
5 AE-T-h/T is the energy width of the excited state with a mean lifetime T due to Heisenberg uncertainty relation 10
6 Energy levels and resulting spectrum of quadrupole splitting for 57Fe 15
7 Energy levels and resulting spectrum of hyperfine magnetic interactions for 57Fe 17
8 Combined magnetic and quadrupole interaction along with resulting spectrum 18
9 Vector relations between the spin, orbital and total angular moments and their associated magnetic moments 23
10 The spontaneous magnetization as a function of reduced temperatuer for J= 1/2, 1, 00. The value of J = 00 corresponds to the classical case where J can take cn an infinite number of values 28
11 Block diagram of the Mossbauer spectrometer 36
12 Pulse height distribution for 14 Key Y-ray and K X-ray using a Kr filled proportional counter 37
13 Calibration plot of velocity versus channel number for the size peaks of 57Fe. The slope of this line gives the velocity calibration (mm/sec/channel) 40
14 X-Ray Diffraction patterns of ZSM-5 and Silicalite 42
15 Possible model of the pore-structure of ZSM and Silicate 46
16 Mossbauer spectrum of Silicate impregnated with 13.6% using Fe(NO3)3 52
17 Mossbauer spectrum of reduced ZSM-5 (14.7% Fe) 53
18 Mossbauer spectrum of reduced ZSM-5 (5.4% Fe, 1.3% Cc) 55
19 Mossbauer spectrum of reduced Silicate (4.4% Fe, 3% Co) 56
20 Mossbauer spectrum of carbided ZSM-5 (14.7% Fe) 57
21 Mossbauer spectrum of carbided ZSM-5 (5.4% Fe, 1.3% Co) 59
22 Mossbauer spectrum of used ZSM-5 (14.7% Fe) 60
23 Mossbauer spectrum of used ZSM-5 (5.4% Fe, 4.5% Co) 61
24 Mossbauer spectrum of used Silicate (13.6%) 63
25 Mossbauer spectrum of used Silicate (4.4% Fe, 3% Co) 64
26 Magnetization (Bohr Magenetons per Fe atom) as a function of temperature for ZSM-5 (11.1% Fe) 66
27 Magnetization as a function of temperature for ZSM-5 (5.6% Fe, 4.5% Co). The Bohr Magneton number represents the weighted average of the two components present. 67