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(64b) Direct Conversion of Methane to Aromatics Using Metal Carbides

Authors: 
Thakur, R., Auburn University
Carrero, C., Auburn University
Due to the recent shifts in feedstock, the global petrochemical industry has experienced a significant disruption in the supply and demand of key chemical building. Supplies of ethylene have surged as US shale gas production has boomed, meanwhile the supplies of benzene and other light olefins have declined. Therefore, finding direct routes to convert methane into valuable, and preferentially, liquid products is highly desired. Up to now, various catalytic routes including dehydroaromatization,1-3and oxidative coupling to produce ethylene4 have been investigated but still cannot compete with the well stablished, although highly energy intensive, steam reforming of methane. This indirect route convert methane into syngas to then produce most of the chemicals we use nowadays, while the direct conversion of methane is potentially more environment friendly and economical but the challenge lies in stabilizing the catalyst against coking. Metal containing zeolites, especially Mo/H-ZSM-5, have shown promising results for MDA reaction. Commercial prospects for MDA process are hampered by the copious amount of coke deposition on Mo/H-ZSM-5 catalyst at the high reaction temperatures. We believe that using identifying the optimal conditions during the preparation, carburization and testing of the catalyst, along with characterizing the Mo species formed and/or transformed during each step prior and during the reaction might be an effective alternative towards attaining stability, selectivity and activity under higher temperature conditions. As many of the important questions related to nature of active sites, catalyst deactivation mode etc. are still unanswered thus limiting the commercialization of MDA process.

In this presentation, we will present our results related to different pre-carburization methodologies to tune the Mo/H-ZSM-5 catalyst properties with enhanced activity and stability. We control the nature and the amount of carbide species formed during the initial induction period and relate that with the catalysts activity. Stress in the presentation will be focused towards the present Mo/H-ZSM-5 catalyst and the newly emerging family of two dimensional (2D) layered carbides, with an aim to stabilize the existing catalyst and to further explore different catalytic active material for the MDA process.

References

  1. Gao, J.; Zheng, Y.; Jehng, J.-M.; Tang, Y.; Wachs, I. E.; Podkolzin, S. G., Identification of molybdenum oxide nanostructures on zeolites for natural gas conversion. Science 2015, 348 (6235), 686-690.
  2. Lezcano‐González, I.; Oord, R.; Rovezzi, M.; Glatzel, P.; Botchway, S. W.; Weckhuysen, B. M.; Beale, A. M., Molybdenum Speciation and its Impact on Catalytic Activity during Methane Dehydroaromatization in Zeolite ZSM‐5 as Revealed by Operando X‐Ray Methods. Angewandte Chemie International Edition 2016, 55 (17), 5215-5219.
  3. Kosinov, N.; Wijpkema, A. S.; Uslamin, E.; Rohling, R.; Coumans, F. J.; Mezari, B.; Parastaev, A.; Poryvaev, A. S.; Fedin, M. V.; Pidko, E. A., Confined Carbon Mediating Dehydroaromatization of Methane over Mo/ZSM‐5. Angewandte Chemie International Edition 2018, 57 (4), 1016-1020.
  4. Bhatia, S.; Thien, C. Y.; Mohamed, A. R., Oxidative coupling of methane (OCM) in a catalytic membrane reactor and comparison of its performance with other catalytic reactors. Chemical engineering journal 2009, 148 (2-3), 525-532.