Gas to liquids: natural gas conversion to aromatic fuels and chemicals in a hydrogen-permeable ceramic hollow fiber membrane reactor

Abstract

The performance of a dense ceramic hydrogen-permeable membrane reactor for the nonoxidative methane dehydroaromatization (MDA), according to the equilibrium reaction 6CH₄ ⇆ C₆H₆+ 9H₂ with a 6 wt % Mo/HZSM-5 bifunctional catalyst was investigated. A U-shaped ceramic hollow fiber membrane of the composition La₅.₅Wₒ.₆Mo₀.₄O₁₁.₂₅−δ (LWM₀.₄) has been used for the in situ removal of H₂ to overcome thermodynamic constraints. The yield of aromatics (benzene, toluene, naphthalene) in the MDA could be increased in the beginning of the aromatization reaction by ∼50%–70%, in comparison with the fixed-bed reactor, because 40%–60% of the H₂ abstracted have been extracted at 700 °C with a weight hourly space velocity (WHSV) of 840 cm³ gcat¯¹ h¯¹. These advantages of the membrane reactor operation decrease with time on stream, since the removal of H₂ boosts not only CH₄ conversion and yield of aromatics, but also catalyst deactivation by deposition of carbonaceous deposits. However, the catalyst system could be regenerated by burning the coke away with air.