Flame-made amorphous solid acids with tunable acidity for the aqueous conversion of glucose to levulinic acid

Solid acids of amorphous silica-alumina (a-SA) and amorphous silica-alumina-phosphate (a-SAPO) were prepared by flame spray pyrolysis (FSP). Careful tuning of the acidity of the solid acids was enabled by capitalizing on the advantage of FSP in preserving the metal stoichiometry ( i.e. , Si, Al, P)...

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Published in:Green chemistry : an international journal and green chemistry resource : GC 2020-02, Vol.22 (3), p.688-698
Main Authors: Beh, Gein Khai, Wang, Chang Ting, Kim, Kyungduk, Qu, Jiangtao, Cairney, Julie, Ng, Yun Hau, An, Alicia Kyoungjin, Ryoo, Ryong, Urakawa, Atsushi, Teoh, Wey Yang
Format: Article
Language:English
Subjects:
Acidity
Acids
Aluminum oxide
Catalysts
Conversion
Glucose
Green chemistry
Halides
Levulinic acid
Metal halides
Nanoparticles
Pyrolysis
Silica
Silicon dioxide
Spray pyrolysis
Stoichiometry
Zeolites
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Summary:Solid acids of amorphous silica-alumina (a-SA) and amorphous silica-alumina-phosphate (a-SAPO) were prepared by flame spray pyrolysis (FSP). Careful tuning of the acidity of the solid acids was enabled by capitalizing on the advantage of FSP in preserving the metal stoichiometry ( i.e. , Si, Al, P) in the product nanoparticles. Although the amount of acids on these non-porous solid acids is an order of magnitude lower than the well-recognized strong acidic ZSM-5 zeolite, both exhibit comparable acid strengths. The a-SA and a-SAPO were characterized by a mixture of Brnsted (B) and Lewis (L) acids, and the B/L ratios were composition-tunable. The highest B/L ratios were recorded for a-SA (Al/(Al + Si) = 0.4) and a-SAPO (Si/(P + Si) = 0.25), giving the highest yields of levulinic acid (40% carbon yield) from the conversion of glucose in the aqueous phase without requiring the addition of liquid acids or metal halides. Under the same conditions, the almost exclusive Brnsted acid ZSM-5 yielded only 17% levulinic acid. The FSP-made solid acid catalyst exhibited good reusability over at least 4 consecutive runs. Composition-tunable mixed Brnsted/Lewis acids on silica-alumina and silica-alumina-phosphate prepared by the rapid flame spray pyrolysis produce exceptionally high glucose-to-levulinic acid yield, twice that of commercial ZSM-5 and Zeolite X.
ISSN:1463-9262
1463-9270
DOI:10.1039/c9gc02567g