248
selectivity as observed in fixed-bed unit. On increasing temperature, higher amount
of H 2 was released (16%) showing an improvement in conversion and benzene
selectivity.
1.6 Summary
Non-oxidative methane conversion into higher hydrocarbons is of huge potential
curiosity as emerging high-value aromatic compounds with pure hydrogen as side
product direct from natural gas in one-step reaction. However, thermodynamic and
kinetic based limitations in methane dehydroaromatization restrict its commercialization. Besides aromatic compounds (benzene, toluene and xylene) and hydrogen
in MDA reaction, carbonaceous species is another major product which is thermodynamically favoured at MDA conditions and thus imparts fast catalytic deactivation which is a major challenge in the MDA process. To overcome these limitations,
different experimental approaches such as the addition of oxygenates (CO 2 , CO,
H 2 O and CH 3 OH) and light hydrocarbons (C 2 –C 4 ) to methane feed, in situ H 2
removal using modified reactor configuration, incorporation of catalyst regeneration protocol, etc. have been implemented by chemical community to control the
thermodynamic and kinetic inertness of MDA reaction. High chemical inertness of
methane molecule imparts certain limitations for its activation and coupling to
higher hydrocarbons and thus requires high energy for the MDA process. Combined
theoretical and experimental studies can control these kinds of limitations. Mo/
ZSM-5 is the best catalyst studied for the MDA reaction and results in higher methane conversion with remarkable benzene yield. Major constituents of MDA catalyst
are active molybdenum carbide/oxycarbide (Mo x C y ) species and Brønsted acid sites
of zeolite which controls the anchoring of active Mo x C y species inside the zeolite
channels. Theoretically, different molybdenum carbide/oxycarbide structure has
been optimized and identified for MDA reaction analysis which directs that stable
Mo x C y nanocluster anchored at suitable site (Al site) inside the channel of zeolite
framework significantly controls the overall activity of MDA catalyst. Thus, understanding the mechanistic insights of MDA reaction and modifications in reactor
configuration can significantly upgrade the MDA process at industrial level.
References
1. Ashcroft AT, Cheetham AK, Green MLH, Vernon PDF (1991) Partial oxidation of methane to
synthesis gas using carbon dioxide. Nature 352:225–226. nature.com/articles/352225a0
2. Wang S, Lu (Max) GQ, Millar GJ (1996) Carbon dioxide reforming of methane to produce
synthesis gas over metal-supported catalysts: state of the art. Energy Fuels 10:896–904. https://
doi.org/10.1021/ef950227t
S. Mishra et al.
selectivity as observed in fixed-bed unit. On increasing temperature, higher amount
of H 2 was released (16%) showing an improvement in conversion and benzene
selectivity.
1.6 Summary
Non-oxidative methane conversion into higher hydrocarbons is of huge potential
curiosity as emerging high-value aromatic compounds with pure hydrogen as side
product direct from natural gas in one-step reaction. However, thermodynamic and
kinetic based limitations in methane dehydroaromatization restrict its commercialization. Besides aromatic compounds (benzene, toluene and xylene) and hydrogen
in MDA reaction, carbonaceous species is another major product which is thermodynamically favoured at MDA conditions and thus imparts fast catalytic deactivation which is a major challenge in the MDA process. To overcome these limitations,
different experimental approaches such as the addition of oxygenates (CO 2 , CO,
H 2 O and CH 3 OH) and light hydrocarbons (C 2 –C 4 ) to methane feed, in situ H 2
removal using modified reactor configuration, incorporation of catalyst regeneration protocol, etc. have been implemented by chemical community to control the
thermodynamic and kinetic inertness of MDA reaction. High chemical inertness of
methane molecule imparts certain limitations for its activation and coupling to
higher hydrocarbons and thus requires high energy for the MDA process. Combined
theoretical and experimental studies can control these kinds of limitations. Mo/
ZSM-5 is the best catalyst studied for the MDA reaction and results in higher methane conversion with remarkable benzene yield. Major constituents of MDA catalyst
are active molybdenum carbide/oxycarbide (Mo x C y ) species and Brønsted acid sites
of zeolite which controls the anchoring of active Mo x C y species inside the zeolite
channels. Theoretically, different molybdenum carbide/oxycarbide structure has
been optimized and identified for MDA reaction analysis which directs that stable
Mo x C y nanocluster anchored at suitable site (Al site) inside the channel of zeolite
framework significantly controls the overall activity of MDA catalyst. Thus, understanding the mechanistic insights of MDA reaction and modifications in reactor
configuration can significantly upgrade the MDA process at industrial level.
References
1. Ashcroft AT, Cheetham AK, Green MLH, Vernon PDF (1991) Partial oxidation of methane to
synthesis gas using carbon dioxide. Nature 352:225–226. nature.com/articles/352225a0
2. Wang S, Lu (Max) GQ, Millar GJ (1996) Carbon dioxide reforming of methane to produce
synthesis gas over metal-supported catalysts: state of the art. Energy Fuels 10:896–904. https://
doi.org/10.1021/ef950227t
S. Mishra et al.