Promoted catalytic performance of sugarcane bagasse ash supported by γ-alumina as efficient, stable, and ecofriendly catalyst for dehydration of methanol to dimethyl ether

The aim of this study was to use different proportions (1% to 20% by weight) of γ-alumina to modify sugarcane bagasse ash (SCBA) for the production of dimethyl ether (DME) through the dehydration of methyl alcohol. A simple precipitation method was utilized to fabricate (1–20 wt.%) Al₂O₃/SCBA catalysts. X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, and N₂ sorption were used to explore the structural, spectroscopic, morphological, and textural features. The XRD pattern of Al₂O₃/SCBA catalysts showed a new peak that corresponded to the formation of γ-Al₂O₃. In addition, the average crystallite sizes of pure SCBA and 10% and 20%Al₂O₃/SCBA catalysts were calculated and found to be 20.1, 21.6, and 22.6 nm, respectively. To evaluate the acidity of these catalysts, the dehydration of isopropyl alcohol and the chemisorption of basic probe molecules were employed. The acidity test results displayed that these catalysts have weak to moderate acidic sites. The 10% Al₂O₃/SCBA catalyst calcined at 400°C showed high efficiency for the conversion of methyl alcohol to DME, attaining 89% conversion with 100% selectivity. This observation can be attributed to the even distribution of active sites and the acid–base equilibrium on the surface. Moreover, its catalytic activity and selectivity remain unchanged over a continuous 2-week operation without coke formation, demonstrating its extremely high stability. A strong correlation was observed between the catalytic activity and both the surface area and acidity of the catalysts.