1. 2015-5-231 Effect of water in direct methane dehydroaromatization over 3%Mo/HZSM-5 under supersonic jet expansion condition B.S. Liu a, L. Li a, C.T. Au c, A.S.-C. Cheung a* a The University of Hong Kong, Pokfulam Road, Hong Kong, China c Hong Kong Baptist University, Kowloon Tong, Hong Kong, China

2. 2015-5-232 Acknowledgements: The work was supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. HKU 7015/07P). Prof. Bingsi Liu, Tianjin University, China Drs. Joanne W.H. Leung and Lynn L. Li, HKU Prof. C.T. Au, Hong Kong Baptist University

3. 2015-5-233 I. Introduction Energy Petroleum Coal Syngas Chemicals Aromatics Hydrogen Fuel cell NH 3

4. 2015-5-234 CH 4 Mo/HZSM-5 700 o C C 6 H 6 C 7 H 8 C 10 H 8 + H2H2 The catalyst Mo/HZSM-5 needs to be activated during the induction period: H 2 O (< 2%) +

5. 2015-5-235 2. Problems ? (1) Activation of catalyst in induction period. (2) Carbon deposition over catalyst Non-traditional procedure CH 4 only ? Membrane reactor Supersonic jet expansion CH 4 + H 2 O ?

6. 2015-5-236 II. Experiment CH 4 dehydro-aromatization apparatus is coupled to a Time-of-flight (TOF) mass spectrometer. CH 4 dehydroaromatization apparatus – catalytic reaction TOF – detect and monitor reagents (CH 4, H 2 O) and reacted species (eg. C 10 H 8 ) etc.. Ionization of species by a pulsed laser (266 nm; 13 mJ) CH 4 dehydro-aromatization apparatus is coupled to a Time-of-flight (TOF) mass spectrometer. CH 4 dehydroaromatization apparatus – catalytic reaction TOF – detect and monitor reagents (CH 4, H 2 O) and reacted species (eg. C 10 H 8 ) etc.. Ionization of species by a pulsed laser (266 nm; 13 mJ)

7. 2015-5-237 Fig.1 Apparatus for CH 4 dehydroaromatization II. Experiment

8. 2015-5-238 III. Results and discussion Fig.2 Product distribution at different time on stream 1. Investigation on catalyst activation – CH 4

9. 2015-5-239 2. Effect of water during CH 4 dehydroaromatization (after the induction period) Fig.4 Effect of water on Mo/ZSM-5 catalyst; (A) 1.4%H 2 O; (B) 2.0%H 2 O; (C) Relative stability of catalyst.

10. 2015-5-2310 3. Investigation on catalyst activation – CH 4 + H 2 O Figure 5 Direct addition of water in induction period of CH 4 dehydroaromatic reaction NO C 10 H 8 formation

11. 2015-5-2311 4. Properties of coke under condition of H 2 O/CH 4 co-feed Fig.6 TPO profiles of used catalyst Fig.7 Amorphous carbon deposition over Mo 2 C particle. (TEM).

12. 2015-5-2312 Fig.8 Carbon 1s XPS spectra used 3%Mo/HZSM-5 at different condition.

13. 2015-5-2313 Fig.11 Mo 3d XPS spectra of 3%Mo/HZSM-5 samples 6. Properties of Mo 2 C at different H 2 O/CH 4 co-feed by XPS

14. 2015-5-2314 VI. Conclusion: 1.Direct dehydroaromatization of methane over 3%Mo/HZSM-5 forms naphthalene under the supersonic jet expansion condition. In this work, the gas mixture exited from reaction zone was analyzed directly using TOF-MS. 2. An appropriate amount of steam co-addition to methane feed over Mo/HZSM-5 can improve the stability of catalyst. Carbon deposition was reduced with increasing steam concentration.

15. 2015-5-2315 3. The results of TPO, XPS and HRTEM image demonstrate that the carbon deposition is basically amorphous in structure during the H 2 O/CH 4 reaction but the formation of graphite carbon when CH 4 was used only. 4. Addition of excess water (> 2%) led to the deactivation of Mo 2 C/HZSM-5 catalyst and the destruction of Mo 2 C.

16. 2015-5-2316