Low Temperature Direct Conversion of Methane using a Solid Superacid

The direct conversion of methane to higher hydrocarbons and hydrogen can be catalyzed using “superacids”: n CH 4 →C n H m + x H 2 . The first report of catalytic oligomerization of methane using superacids was that of Olah et al., who demonstrated the superacidity of FSO 3 H−SbF 5 , which is a liquid. More recently, Vasireddy et al. showed that gas‐phase HBr/AlBr 3 was an active superacid. The only reported solid superacid for methane oligomerization is sulfated zirconia (SZ). Here, we report a new class of Br‐based solid superacids, AlBr x /H‐ZSM‐5 (“ABZ‐5”, x=1 or 2). ABZ‐5 is based on gas‐phase HBr/AlBr 3 , with the objective of synthesizing a heterogeneous analogue of the gas‐phase superacid HBr/AlBr 3 . The results show that ABZ‐5 is significantly more active than SZ. Perhaps more significantly, results here show methane conversions of ∼1 % at 300 °C using ABZ‐5. By comparison with SZ, 350 °C is the lowest temperature reported in the literature at which measurable conversions are shown, and the corresponding methane conversions were <0.15. Here, we demonstrate direct conversion of methane using a solid superacid catalyst, AlBr x /H‐ZSM‐5. This solid catalyst is synthesized using a vapor‐phase process in which AlBr 3 vapor is grafted on to solid H‐SZM‐5. This catalyst is characterized using NH 3 ‐TPD, XRD, and DRIFTS. Hydrocarbon products observed in the temperature range of 200–400 °C include both C 2 –C 6 hydrocarbons and aromatics.