Dual-Bed Plasma/Catalytic Synergy for Methane Transformation into Aromatics

Abstract

Direct conversion of methane to aromatics (benzene, toluene, and xylene, briefly BTX) remains a formidable challenge. Here, we demonstrate that CH4 can be efficiently transformed into BTX through the coupling of a dielectric barrier discharge (DBD) plasma reactor with a thermocatalytic aromatization reactor (at temperatures ≤ 550 °C). With the assistance of DBD plasma, methane can be activated by the energetic electrons to form various radicals, which are recombined to produce a mixture of C2–C6 light alkanes and alkenes. With a plasma power deposition of 12 W, the conversion of CH4 is up to 50% dependent upon the partial pressure. The energy efficiency is between 0.3 to 1.5 mol/(kW h) dependent upon the power deposition. The C2–C6 light hydrocarbons from the plasma reactor can be transformed into BTX over various catalysts at temperatures ≤ 550 °C. With the Ga/HZSM-5 catalyst, the selectivity of total BTX is up to 70% dependent upon the reaction conditions (temperature, partial pressure, and catalyst loading). With such a dual-bed plasma/catalytic tandem system, CH4 conversion and BTX yield only slightly deactivated with time-on-stream up to 1000 min and can be 100% regenerated through coke burnoff. We suggest that the dual-bed plasma/catalytic reaction system could be interesting for small-scale onsite flare gas or biogas conversion.