Performance of Al-MCM-41 nanospheres as catalysts for dimethyl ether production

The need to develop specific-morphology nanomaterials to produce dimethyl ether (DME), a promissory alternative fuel, by the catalytic methanol dehydration has triggered extensive research to synthesize novel materials. In this work mesoporous Al-MCM-41 nanospheres with variable size (35 90 nm) were synthesized by the sol-gel method. The size of the Al-MCM-41 nanospheres was controlled by adjustable NaOH/TEOS ratio (0.2 0.5). The Al-MCM-41 nanospheres were characterized by TPD, TEM, XRD, EDX, XPS and N-2-physisorption. According to the characterization results the Al ions were successfully incorporated in the MCM-41 framework and the Al-MCM-41 nanospheres showed hexagonal and mesoporous structure. Additionally, it was observed that the higher the NaOH/TEOS ratio the smaller size of the nanosphere and, smaller Al-MCM-41 nanospheres presented more amount of medium acidic sites on its surface. The catalytic activity results showed that all samples tested reached 100% of selectivity towards DME. The smallest Al-MCM-41 nanospheres achieved 78% of DME yield at 300 degrees C and good catalytic activity performance below to 300 degrees C. The stability of the fresh and regenerated AlMCM-41 nanospheres was evaluated for 48 h time-on-stream. High values of DME yield (> 60%) were maintained during 48 h time-on-stream showing the possibility for recycling the material.

Automated summary

In this study, mesoporous Al-MCM-41 nanospheres with variable sizes were successfully synthesized and characterized, showing hexagonal and mesoporous structure with the successful incorporation of Al ions. The smaller nanospheres exhibited more medium acidic sites on the surface. All samples displayed good selectivity towards DME, with the smallest nanospheres achieving 78% DME yield at 300 degrees C. The stability test revealed high DME yield (>60%) maintained during a 48-hour time-on-stream, indicating the potential for material recycling.