Synthesis of Beta Nanocrystal Aggregates from Al-SBA-15 via Seed-assisted Steaming Conversion
Beta nanocrystal aggregates(BNA)possessing two types of hierarchical mesopores have been synthesized by the one-step conversion of the ordered mesoporous material Al-SBA-15 following a seed-assisted steaming conver-sion(SASC)strategy.The relationship between the assembly of the Beta zeolite and the evolution of hierarchical mesostructure was systematically investigated.Using a controllable thermal treatment,the P123 micelle was selectively decomposed to form the carbonaceous particles that highly dispersed inside the mesopores,and then a new three-dimensional nanosized space network was constructed in the whole Al-SBA-15 bulky particles.With the help of the pre-impregnated Beta seed solution and tetraethylammonium cation(TEA+)template,the amorphous Al-SBA-15 walls were slowly converted to the Beta nanocrystals in these spaces under the low-solvent-content conditions.By adjusting the synthesis parameters,the resulting nanocrystals arranged along the Al-SBA-15 wall direction and formed a newly ordered mesostrcuture.In addition,the BNA has another kind of large cavity that connected through the mesopores after the removal of carbonaceous particles.On the other hand,the high-quality framework assembly derived from the slow mass transfer directly caused the strong acidity of the final BNA.The strong acidity combined with the excellent hierarchical textural characteristic endow BNA with great application potential in acid catalytic reactions involving large molecules.
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