Prompt Gamma Activation
Analysis and Related Topics
Detre Teschner Department of Inorganic Chemistry,
Fritz-Haber-Institut der Max-Planck-Gesellschaft
1
Modern Methods in Heterogeneous Catalysis Research
PGAA: the basics
2 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
3 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
PGAA: the basics
4 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
• Sample is irradiated by neutrons.
• We detect g-photos emitted by the nucleus after neutron capture.
• Energy: qualitative information,
Intensity: quantitative information.
• The signal is independent of the physical and chemical nature of the sample, and only depends on the structure of the nucleus.
PGAA: the basics
Question
5 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Name methods giving you the same type of
information as you can obtain by PGAA?
• ICP-MS, ICP-OES
• XRF
• EDX
• Gravimetry (dissolution and precipitation)
• CHN analysis by combustion
Outline
6 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
0) PGAA basics
1) Main properties, neutron capture
2) Setup
3) Related techniques
4) Application examples
5) Catalytic examples
PGAA detection limits
7 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
1 18
1
H 2 13 14 15 16 17 2
He
3
Li 4
Be 5
B 6
C 7
N 8
O 9
F 10
Ne
11
Na 12
Mg 3 4 5 6 7 8 9 10 11 12 13
Al 14
Si 15
P 16
S 17
Cl 18
Ar
19
K 20
Ca 21
Sc 22
Ti 23
V 24
Cr 25
Mn 26
Fe 27
Co 28
Ni 29
Cu 30
Zn 31
Ga 32
Ge 33
As 34
Se 35
Br 36
Kr
37
Rb 38
Sr 39
Y 40
Zr 41
Nb 42
Mo 43
Tc 44
Ru 45
Rh 46
Pd 47
Ag 48
Cd 49
In 50
Sn 51
Sb 52
Te 53
I 54
Xe
55
Cs 56
Ba 57
Laa 72
Hf 73
Ta 74
W 75
Re 76
Os 77
Ir 78
Pt 79
Au 80
Hg 81
Tl 82
Pb 83
Bi 84
Po 85
At 86
Rn
87
Fr 88
Ra 89
Acb 104
Rf 105
Db 106
Sg 107
Bk 108
Hs 109
Mt 110
Ds 111
Rg 112
Cn 113
Uut 114
Uuq 115
Uup 116
Uuh
a Lanthanoids 58
Ce 59
Pr 60
Nd 61
Pm 62
Sm 63
Eu 64
Gd 65
Tb 66
Dy 67
Ho 68
Er 69
Tm 70
Yb 71
Lu
b Actinoids 90
Th 91
Pa 92
U 93
Np 94
Pu 95
Am 96
Cm 97
Bk 98
Cf 99
Es 100
Fm 101
Md 102
No 103
Lr
>1 mg/g
100 – 1000 mg/g
10 – 100 mg/g
1 – 10 mg/g
< 1 mg/g
No data
courtesy of L. Szentmiklósi
Properties of PGAA
• nondestructive
• no sample preparation, sample in any form
• independent from chemical environment
• all elements, isotopes: panorama analysis
- light elements (H, B, N, Na, Cl, …)
• extremely different sensitivities
• complicated gamma spectrum
8 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
9
Properties of neutron capture
Strasbourg – 05.07.2011.
10-5 1 105 Energy (eV)
103
1
10-3
C.S
. (b
arn
s)
35Cl
Ec = ET - ER
v c = i v Pc
Pc,j i
i
/ = 1
ER =2mAc2
Ec2 E: gamma, transition and recoil
mA: mass of radiating atom
v c: partial gamma production C.S.
i : isotope abundance
Pc: emission probabil ity
v : capture C.S.
Energy
ZAX
ZA+ 1X*
Z+ 1A+ 1X
n
c 1
c 2
c 3
c 4
c 5
c 6
9 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Properties of neutron capture
10
Quantification
Strasbourg – 05.07.2011.
R= nv U
t c = f (Ec)nv c U
t c =M
n (r)
0
3
#V
# NA v c (En)U' (EN,r) f ' (Ec,r)dENdr
Reaction rate: n: number of atoms
U: neutron fluxCount rate of a gamma peak:
f (Ec): counting efficiency
A: net peak area
n2
n1 =A2 / (f 2 v c,2)A1/ (f 1v c,1)
n (r): mass density of the examined element
Quantification
10 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Setup: Budapest Neutron Centre
11 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Question
12 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
How can we produce neutrons?
• spallation neutron source (accelerated protons hit Ta, W, Hg target)
• nuclear reactor (induced fission; highly enriched 235U)
• spontaneous fission (252Cf)
• neutron generator (fusion)
• isotopic neutron source (Pu-Be)
Setup: Cold neutron source
13 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
FRM II
Spallation: >10 MeV
Fission: 1-10 MeV
Thermalized: ~0.025 eV
Cold: 10-5 – 0.025 eV
Elastic scattering for
thermalizing/cooling n0
Setup: Budapest Neutron Centre
10 MW research reactor with a L-H2 cold neutron source
Curved neutron guides
PGAA facility: Flux (@sample):107-108 cm-2s-1 Compton-suppressed HPGe
14 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Setup: Compton-suppressed HPGe detector
160
30
19
BUDAPEST COMPTON-SUPPRESSED / PAIR-MODE GAMMA SPECTROMETER
8 x BGO
PM
PM
PM
PM
HPGe200
366
BGOcatcher
180
65,5
PM
BGO
HPGe
15 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Setup: Compton suppression
16 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
2000 4000 6000 8000 10000 12000 14000 160001
10
100
1k
10k
100k
1M
Co
un
ts/C
ha
nn
el
Channel number
2000 4000 6000 8000 10000
1
10
100
1k
10k
100k
1M
E (keV)
Unsuppressed
Compton-suppressed
Spectrum
17 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Spectrum, library
18 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Z El A MW # E dE s ds% RI Area cps/g
1 H 1 1.01 1 2223.259 0.019 0.3326 0.2 100.00 100.00 64.183
1 H 2 1.01 2 6250.204 0.098 0.000492 5.0 0.15 5.00 0.0286
3 Li 6 6.94 5 477.586 0.050 0.001399 5.9 3.52 10.14 0.1218
3 Li 7 6.94 2 980.559 0.046 0.004365 5.1 10.97 18.74 0.2251
3 Li 7 6.94 3 1051.817 0.048 0.004364 5.1 10.97 17.83 0.2141
3 Li 7 6.94 1 2032.310 0.070 0.0398 5.0 100.00 100.00 1.2007
3 Li 6 6.94 6 6769.633 0.263 0.001354 6.5 3.40 0.84 0.0101
3 Li 6 6.94 4 7246.800 0.275 0.002106 8.4 5.29 1.17 0.014
4 Be 9 9.01 4 853.631 0.011 0.00165 8.9 26.69 100.00 0.0723
4 Be 9 9.01 3 2590.014 0.025 0.00188 8.9 30.41 49.08 0.0355
4 Be 9 9.01 2 3367.484 0.035 0.002924 8.9 47.30 58.96 0.0427
4 Be 9 9.01 5 3443.421 0.036 0.000993 8.9 16.06 19.54 0.0141
4 Be 9 9.01 6 5956.602 0.092 0.000146 9.1 2.36 1.41 0.001
4 Be 9 9.01 1 6809.579 0.099 0.006181 9.0 100.00 48.52 0.0351
5 B 10 10.81 1 477.600 5.000 712.5 0.3 100.00 100.00 39806
6 C 12 12.01 2 1261.708 0.057 0.00123 2.7 45.58 100.00 0.0306
6 C 12 12.01 3 3684.016 0.069 0.001175 3.5 43.53 38.02 0.0116
6 C 12 12.01 1 4945.302 0.066 0.002699 2.9 100.00 60.55 0.0186
7 N 14 14.01 22 583.567 0.031 0.000429 3.3 1.81 6.93 0.0159
7 N 14 14.01 12 1678.244 0.029 0.006254 1.5 26.34 47.15 0.1085
7 N 14 14.01 18 1681.174 0.043 0.001296 2.7 5.46 9.76 0.0225
7 N 14 14.01 21 1853.944 0.052 0.000474 4.5 2.00 3.31 0.0076
7 N 14 14.01 5 1884.853 0.031 0.0145 1.3 61.07 100.00 0.2301
7 N 14 14.01 24 1988.532 0.077 0.000294 5.8 1.24 1.94 0.0045
7 N 14 14.01 15 1999.693 0.032 0.003208 1.7 13.51 21.12 0.0486
7 N 14 14.01 13 2520.446 0.039 0.004246 1.8 17.88 22.98 0.0529
courtesy of L. Szentmiklósi
Question
19 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Count rate of a peak =
(n,g) reaction rates emission probability
detection efficiency
How would you measure the counting efficiency of
the gamma detector?
• Use radioactive materials emitting in a broad enough energy range.
Question
20 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
How would you measure the counting efficiency of
the gamma detector?
Question
21 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
How would you measure the counting efficiency of
the gamma detector?
PGAA: the basics
Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner 22
Question
23 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Assume you have a PGAA setup. What
modification you would do to be able to distinguish
between prompt and decay gamma radiation?
• Use chopper of neutron beam.
• Filter detected gammas during chopped beam (open/closed).
Question
24 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
What modification you would do to be able to
distinguish between prompt and decay gamma
radiation?
Question
25 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
What modification you would do to be able to
distinguish between prompt and decay gamma
radiation?
Related techniques
26 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
• NAA/NIPS
• PGAI
• Radiography/Tomography-driven PGAI
Most real objects are made of some distinct, by themself homogeneous parts
Visualize and locate the interesting regions first, prompt gamma measurement only where it
is needed for the conclusive result
NAA vs. PGAA
27 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
sample
preparation
irradiation
detection
time requirement
detection limit
element detectable
remaining activity
1 g
no, teflon bag
at endstations
on-line
100-5000 peaks, 12 MeV
minutes, hours
>ppm
all except He
max. 1-2 days
10 mg
drying, ampule
at the n0 source
separated in time and space
10-100 peaks, 3 MeV
weeks and more
ppm-ppb
>Na
for months
Multi-element method
No matrix effect
reproducibility
reliable error estimate
nondestructive
Detection after irradiation
PGAA station
NIPS station
Sample
NAA/NIPS
28 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
NAA/NIPS: detection
29 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Short sample-detector distance
Increase of efficiency (50-180x)
Detection limit can be better
for certain elements, and
element combinations
For large samples requires
correction for g-self-absorption
Imaging: Why to use neutrons for safeguards?
150 keV X-rays
1.25 MeV gamma-rays
slow neutrons
NO USEFUL INFO
NOT SHARP ENOUGH, BAD CONTRAST
ALL OBJECTS CAN BE RECOGNISED
IRON PIPE
30 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Well-collimated (parallel) neutron beam
Measuring neutron transmission image
Neutron radiography (1 picture)
Neutron tomography (rotation,
many pictures 3D)
Neutron radiography/tomography (NR/NT)
31 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
NR/NT with Prompt Gamma Activation Imaging
32 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
PGAI-NR/NT
courtesy of Z. Kis and L. Szentmiklósi
n0 direction
A: sample chamber
B: sample stage
C: imaging system
D: gamma detection
Uranium oxide
(U3O8)
Iron
skrew
Aluminum
cylinder
Cu
spheres
…in a Lead
container
Components of the benchmark sample:
PGAI-NR of items in a sealed Pb container
33 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Image correction and object localization
34 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Prompt-gamma spectra of items
35 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Question
36 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Free your mind Neo!
What would be your envisaged PGAA application?
PGAA applications
37 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
PGAA
PGAA applications: industry
Radioisotopic sources + scintillator
• on-line feed analyzers at conveyor belts (Continuous Neutron Analyzer):
cement, coal, mineral analysis
• bore hole logging: oil and mineral extraction industry
Continuous Neutron Analyzer
38 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
PGAA in space
Gamma Ray Spectrometer (GRS) aboard the 2001 Mars Odyssey
To learn about the composition of the Martian surface
39 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
PGAA in space
Gamma Ray Spectrometer Thermal Emission Imaging System
http://mars.jpl.nasa.gov/odyssey/multimedia/images/
J.L. Bandfield, Nature, 447, 2007, 64
40 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
PGAA example: ANCIENT CHARM
41 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
http://ancient-charm.neutron-eu.net/ach
non-destructive analysis of cultural heritage samples
PGAA-NR: ANCIENT CHARM
42 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Disc fibula (Hungarian National Museum), 6th century.
NT
PGAI
PGAA-NR: ANCIENT CHARM
43 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Fe S Au
Cu Al H
Ralf Schulze, Ph.D. thesis, Univ. Köln, 2010
Au
Cu
Au, not Ag
In-situ PGAA
• Adapt PGAA to catalytic research: to provide
fundamental insights of reaction mechanism
• Challenges: • Special geometry, sample environment, shielding
• Decrease background signal
• Reproducibility
• Time dependence?
• Limited beamtime to follow many reaction conditions
• Detection of catalytic performance
• Nuclear data
• Everything should fit
44 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
In-situ PGAA
• Remember: PGAA measures elements, never
compounds
• Signal = Gas phase + Surface + Bulk
• Gas phase: constant or negligible
• Bulk: sometimes the main signal, but sometimes no
bulk contribution
• If no bulk: signal → surface coverage
• Often we measure element ratios
• Sometimes information: only small signal changes
• Online reactivity measurement is required.
45 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Example 1: Hydrogenation
Zs. Révay et al., Anal. Chem. 2008, 80, 6066.
46 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Example 1: Hydrogenation
47 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
1. Experiment in N2 (typically @120°C): to measure
hydrogen content not related to the sample
2. Experiment in H2 (typically near RT)
3. Experiments in hydrogenation (e.g. CxH2x-2+H2;
CxH2x-2+CxH2x+H2)
4. If needed check [H] in N2
+ Correction for gas phase H background
In situ PGAA methodology
1-pentyne conversion and corresponding bulk H/Pd values
Sample: 7 mg Pd black
(200 nm mean p.s.; in SiC)
Temperature: RT
H2: 4 cm3min-1
1-pentyne: 1.6 cm3min-1 in N2
• Always selective hydrogenation
to 1-pentene
• wide variation in H/Pd
No correlation!
D. Teschner et al., Science 2008, 320, 86.
48 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Example 1: Hydrogenation
Alkene Alkane:
Alkyne Alkane:
H
C
D. Teschner et al., Science 2008, 320, 86.
D. Teschner et al., Angewandte Chemie 2008, 120, 9414.
Hydrogen content always
high: 0.8-1 H/Pd
49 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Example 1: Hydrogenation
Model: alkyne hydrogenation on Pd
(h.p. XPS)
50 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Example 1: Hydrogenation
Example 1: Hydrogenation
DFT
P. Sautet
D. Teschner et al., J. Phys. Chem. C 2010, 114, 2293.
51 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
J. Osswald et al., J. Catal., 2008, 258, 210.
K. Kovnir et al., Surf. Sci., 2009, 603, 1784.
PdGa
Isolated Pd site
• Covalent bonding
• Modified electronic structure
No H dissolution (PGAA)
Excellent selectivity in acetylene
semi-hydrogenation
52 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Example 1: Hydrogenation
Example 2: Cl2 production, Deacon
Cl2
NaCl electrolysis
HCl electrolysis
Cl2
H2 +
2 NaCl + 2H2O 2 NaOH + + H2
2 HCl
E
Cat.
E
Cat.
Deacon reaction
2 Cl2 4 HCl + O2 2 H2O + T
Cat.
• In both system RuO2/TiO2 is used as (electro)catalyst.
• RuO2/SnO2/Al2O3: Bayer Deacon patent
• New cheaper Deacon system under development: CeO2
53 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Example 2: Deacon over RuO2
ICIQ: N. Lopez
O2 + 2* ↔ O2**
O2** ↔ 2O*
HCl + O* + * ↔ OH* + Cl*
2Cl* ↔ Cl2 + 2*
2OH* ↔ H2O* +O*
H2O* ↔ H2O + *
54 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
D. Teschner et al., J. Catal., 2012, 285, 273.
Example 2: Deacon over RuO2
55 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Example 2: Deacon over RuO2
Neutron collimator
Detector
Sample in oven
Activity determined by titration Correlation between surface adsorbed species and activity
Gas in Gas out
56 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Example 2: Deacon over RuO2
HCl : O2
1:0.25
1:0.5
1:1
1:2
1:4
v(HCl) = 33.3 ml/min v(total) = 167 ml/min
Balance gas: N2
2. Different HCl: O2 ratios at different T’s
1. Pretreatment with HCl at reaction T
57 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
3. Additional reference experiments
Example 2: Deacon over RuO2
Experiments Titrated
surface sites Cl/Ru ratio
Cl2@RT
16.6 cm3 min-1 Cl2 +
150.1 cm3 min-1 N2
Cus 0.00898
HCl@543 K
33.3 cm3 min-1 HCl +
133.4 cm3 min-1 N2
Cus + Bridge 0.01797
O2@573 K
33.3 cm3 min-1 O2 +
133.4 cm3 min-1 N2
after HCl@543 K
Bridge 0.00876
58 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
D. Teschner et al., Nature Chem., 2012, 4, 739.
Example 2: Deacon over RuO2
• High Cl coverage inhibiting reaction, oxygen activation is rate limiting;
• The higher non-Cl „cus“ coverage, the higher the reaction rate:
1st order rate dependence;
• Effect of T to liberate sites from Cl;
• All supported and unsupported Ru-based samples behave the same way.
59 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
D. Teschner et al., Nature Chem., 2012, 4, 739.
Example 2: Deacon
The new catalytic system: CeO2
60 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Example 2: Deacon over CeO2
Both started after an O2-treatment at 450 °C
• T and p(O2) shows very similar dependence
Both, increasing T and p(O2) decreases surface [Cl] and enhances reactivity.
HCl:O2 ratio
surface subsurface/bulk chlorination
61 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
R. Farra et al., J. Catal., in press.
http://dx.doi.org/10.1016/j.jcat.2012.09.024
Example 2: Deacon over CeO2
Started after a O2-treatment at 450 °C,
from low to high HCl feed content
*O2 flow: 132.8 ml/min
62 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
R. Farra et al., J. Catal., in press.
http://dx.doi.org/10.1016/j.jcat.2012.09.024
Example 2: Deacon over CeO2
Started after a O2-treatment at 450 °C,
from low to high Cl2 feed content
• Essentially no effect of Cl2 on the Cl uptake and thus on [Cl].
• BUT, Cl2 inhibition.
*HCl:O2 = 1:9; T = 430 °C
Only minority sites contribute to the reactivity!
63 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
R. Farra et al., J. Catal., in press.
http://dx.doi.org/10.1016/j.jcat.2012.09.024
Example 2: Deacon over CeO2/ZrO2
• T and p(O2) shows very similar dependence
Both, increasing T and p(O2) decreases surface [Cl] and enhances reactivity.
• No obvious bulk/subsurface chlorination, as found with unsupported CeO2.
64 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
M. Moser et al., Appl. Cat. B., submitted
Future in situ applications
• Any heterogeneous catalytic reaction with stoichiometry change
• Hydrogen storage
• Study of Li ion transfer in batteries
• Diffusion and transport processes, proton transfer, temperature induced
segregation
• Time-resolved experiments
• Combination with neutron tomography
65 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Pros & Cons; Possibilities
Bulk characterization (even for H)
Easy adaptation to “in situ”
H/D exchange
Effective detection: H, B, S, Cl, Co
Can give in situ surface coverage information
Time resolution: (min-h) strongly depending on the element
sensitivity
Little sensitivity: C, O, Al, Si, Sn
Little available: only at cold neutron sources
66 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Further reading
67 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
• PGAA Stuff at Budapest:
L. Szentmiklósi, Zs. Révay, Z. Kis
• R. Farra
Thank you for your attention!
68 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner
Acknowledgement