1. Hierarchically porous Pd/C
catalysts in nitrobenzene
flow hydrogenations
Brennen Lummus
1

2. Importance of Hydrogenation
• Hydrogenation of vegetable oils to make margarine
and shortenings [2]
• Hydrocracking in the petrochemical industry[1]
• Production of specialty chemicals such as aniline
and cyclohexane [4,6]
• Commercially performed using heterogeneous
catalysts – supported Ni, Pd, or Pt [5]
2

3. Hierarchically Porous Catalysts
• Hierarchy of pore sizes in the structure
1. Less potential for coking of catalyst
2. Increased accessible surface area and
metal dispersion [3]
3. Decreased metal particle size
• Theoretically: Longer lifetime, greater
product conversion
3
Advantages

4. Monolith Structures
ThruPore Commercial
4
Video

5. Reactor Design
5

6. Reactor Assembly
Packed-bed Down-flow Constructed with glass and polyethylene tubing
6

7. Flow andTemperature Controls
• Gas Flow: rotameter, range of 0-65 cm3/min
• Liquid Flow: syringe pump with 60 mL plastic syringe
• Temperature: temperature control unit with K-type
thermocouple and heating tape
7

8. Catalyst Loading
• Pre-heat, catalyst bed, and post-bed zones
• ½ inch ID glass tube
• Catalyst and 1 mm glass beads
8

9. Model Reaction-Hydrogenation of Nitrobenzene
• 3:1 Hydrogen to Nitrobenzene
stoichiometric ratio
• Problem: Hydrogen is a gas, reactor
volume is small
• Low Flow – prevent pressure build-up
Parameters studied
• Amount of catalyst
• Temperature
• ResidenceTime
• Metal Loading
• Type (manufacturer)
9

10. Qualitative Observations
• Catalyst eventually deactivates
• Product concentrations change
• Accompanied by color changes
10

11. Terms to Know
• Activity: How fast the reaction proceeds in the presence of the catalyst
• Conversion: Moles reactant converted
Moles of reactant fed
• Selectivity: Moles product X formed
Moles reactant converted
• Reactivity: General term for the overall “strength” of the catalyst
• ResidenceTime: How long the substrate spends in the reactor bed
11

12. Major Possible Products
12

13. Results - Catalyst Mass
• Conditions: 230 °C, .07 mL/min NB, 60 cm3/min H2,
1% Pd/CThruPore catalyst
• Very similar results
13

14. Results-Temperature
• Conditions: .07 mL/min NB, 60 cm3/min H2, 1% Pd/CThruPore catalyst
• HigherTemp: greater initial by-product concentration, deactivation
occurs sooner
14

15. Results - ResidenceTime
• Conditions: 230 °C, .07 mL/min NB,
60 cm3/min H2, 1% Pd/CThruPore
catalyst
• Conditions: 230 °C, .03 mL/min NB, 30
cm3/min H2, 1% Pd/CThruPore catalyst
• Delayed Deactivation
15

16. Results- Metal Loading
• Conditions: 230 °C, .07 mL/min NB, 60
cm3/min H2, 2.0 gramsThruPore Catalyst
• Deactivation seen sooner in 0.5% and 2%
metal loading catalysts
16

17. Results- Commercial Comparison
• Conditions: 230 °C, .07 mL/min NB, 60 cm3/min H2, 2.0 grams 1% Pd/C catalyst
• Neither deactivates, commercial – higher aniline selectivity
17

18. Conclusions
• Commercial catalyst is more selective for the
hydrogenation of nitrobenzene to aniline
• ThruPore catalyst is more reactive
• Catalyzes a deamination reaction alongside
hydrogenation
• Yields by-products, N-cyclohexylaniline and
Diphenylamine, in significant proportions
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19. Future Prospects
• Study more substrates – styrene, benzene,
dichlorobenzene, maleic acid
• Determine mechanism of the deamination
reaction
• Continuous improvement of reactor –
glass syringe, MFC, flow meter with
broader range
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20. References
1) "The Hydrocracking Process." Refining NZ. Refining NZ, n.d.Web. 28 July 2016.
2) "Hydrogenation of Unsaturated Fats andTrans Fat." Chemwiki. N.p., 01 Oct. 2013.Web. 28 July 2016.
3) Kotbagi,T.V., et al. (2015). "Novel one-pot synthesis of hierarchically porous Pd/C monoliths by a co-
gelation method." MRSCommunications 5(01): 51-56.
4) Li, C. H., et al. (2005). "Nitrobenzene hydrogenation with carbon nanotube-supported platinum catalyst
under mild conditions." Journal of Molecular Catalysis A:Chemical 226(1): 101-105.
5) Sangeetha, P., et al. (2009). "Hydrogenation of nitrobenzene over palladium-supported catalysts—Effect
of support."Applied Catalysis A: General 353(2): 160-165.
6) Solymosi, F. (1968). "Importance of the Electric Properties of Supports in theCarrier Effect." Catalysis
Reviews 1(1): 233-255.
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21. Acknowledgements
• ThruPore and NSF for the funding to carry out this project
• Dr.Vincent and the University of Alabama REU program for this opportunity
• Dr. Martin Bakker and Dr.Trupti Kotbagi for advice and guidance
• Dr. Qiaoli Liang for training and assistance on the GCMS software
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22. Heterogeneous Catalysts
• Phase of catalysts differs from
the phase of the reactants
Homogeneous
Heterogeneous

23. Conversion and Selectivity Clarification
Example:
• Run 100 g of NB through reactor
• Product consists of 50 g NB, 40 g aniline,
and 10 g diphenylamine
• Conversion is 50%
• Selectivity is 80% aniline, 20%
diphenylamine
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24. Chromatogram and Spectrum
TP DC 2.118 LF RUN 1, HR 17, '4'
Time
1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00
%
0
100
BAKKER-072016-4 Sm (Mn, 2x1) Magnet EI+
TIC
1.34e6
Area, Height
Area%
70.61
17.65
11.74
Area
142139.19
35522.36
23636.50
Height
1252044
452655
299336
Time
4.31
10.22
10.70
4.31
142139
1252044
10.22
35522
452655 10.70
23636
299336
TP DC 2.118 LF RUN 1, HR 17, '4'
m/z
62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100
%
0
100
BAKKER-072016-4 187 (4.285) Cn (Cen,2, 80.00, Ht); Cm (186:187) Magnet EI+
6.55e493.166.0
65.0
64.063.0
92.1
67.1
78.077.076.0
75.0
91.1
90.0
94.1
95.1
(mainlib) Aniline
60 64 68 72 76 80 84 88 92 96 100 104 108
0
50
100
63
65
66
67
74 76 78 86 88 91
92
93
94
95
NH2
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25. WhyVapor Phase?
• Greater kinetics
• Solubility of hydrogen is low in
nonpolar liquids
• Less transverse force on catalyst
particles by gas compared to liquid
24