Methane dehydroaromatization (MDA) reaction is typically catalyzed by a bifunctional Mo/H-ZSM-5 catalyst to produce benzene from methane (6CH4 → C6H6 + 9H2; ΔGo=432.5 kJ/mol). This reaction is one of the most complex problems of catalysis because of thermodynamic limitations (carbonaceous depositions) which are inevitable in deactivation. MDA is catalyzed by two sites: (a) a metal (typically Mo), and (b) an acid (typically H-ZSM-5). In this presentation, we will describe what solid superacids are, their main characteristics, and introduce the use of Mo/WO3/ZrO2 (Mo/W/Z) solid superacid catalysts in MDA instead of the widely used H-ZSM-5 with experimental results with three different molybdenum loadings (1% (wt.) Mo, 3% (wt.) Mo, and 6% (wt.) Mo). For this purpose, a series of reactions (TOS = 1000 min) were completed in two stages. Mo carburization (MoO3→Mo2C) was the first step. The second step involves MDA with CH4 as the only reactant at temperature ranges from 600°C to 800°C at 50°C intervals, constant pressure (atmospheric) and 1500 mL/g?h (space velocity). The main organic products at each temperature were ethylene, ethane, propylene, and benzene. The fresh, carburized, and spent samples were characterized by XRD, XPS, BET, NH3-TPD, pyridine DRIFTS, EXAFS, and XANES. Partial results show the conversion drops drastically in all the samples after 400 min. 6% (wt.) Mo/W-Z at 600°C has the highest CH4 conversion (12.3% at TOS = 50 min), but it shows more thermostability and lower deactivation rate at 650°C. The conversion achieved by methane within the first 100 minutes (at the same space velocity) is 15.8%1,2 with H-ZSM-5 which shows a big potential of WO3/ZrO2 catalyst.
Audience Take Away:
- Recognize about the importance of Benzene in the chemical industry.
- Learn about the Methane aromatization reaction.
- Understand what solid super acids are.
- Comprehend the application of solid super acids in methane aromatization reaction (specifically the use of Mo/WO3-ZrO2 catalyst).