Ultrastable and strongly acidic Al-SBA-15 with superior activity in LDPE catalytic cracking reaction

Ordered mesoporous molecular sieve materials, Al-SBA-15 was respectively synthesized from the strong acidic and the acid-free media by using a very small quantity of surfactants because of the economic and environmental considerations. The effects of various Al sources on the structural and acidic properties of the final materials were investigated with powder X-ray diffraction (XRD), nitrogen adsorption-desorption at 77 K, transmission electron microscopy (TEM), scanning electron microscopy (SEM), inductively coupled plasma (ICP) analyses, and chemical sorption (Py-IR). When following the acid-free strategy, a highly ordered mesostructure can be facilely constructed even with a very low surfactant concentration, extremely regardless of the kind of Al source that used. The resulting Al-SBA-15 exhibited a much higher aluminum content, a stronger acid strength and especially the predominant Bronsted acidic properties in comparison with those synthesized under the traditional strong acidic conditions, thanks to the high-quality cross-linking and self-assembly of silica and alumina species. In addition, the morphology of the product can also be modulated by simply altering the type of aluminum sources. The Al-SBA-15 synthesized with the aluminum nitrate as Al source exhibited very high catalytic activity in the Low Density Polyethylene (LDPE) cracking reaction, and the temperature corresponding to the maximum cracking rate was even comparable to the zeolitic catalyst.