Abstract
TiO2-based photocatalysts synthesized by the microwave-assisted sol-gel method was tested in the photocatalytic glucose conversion. Modifications of TiO2 with type-Y zeolite (ZeY) and metals (Ag, Cu, and Ag-Cu) were developed for increasing the dispersion of TiO2 nanoparticles and increasing the photocatalytic activity. Effects of the TiO2 dosage to zeolite ratio (i.e., TiO2/ZeY of 10, 20, 40, and 50 mol %) and the silica to alumina ratio in ZeY (i.e., SiO2:Al2O3 of 10, 100, and 500) were firstly studied. It was found that the specific surface area of TiO2/ZeY was 400–590 m2g−1, which was higher than that of pristine TiO2 (34.38 m2g−1). The good properties of 20%TiO2/ZeY photocatalyst, including smaller particles (13.27 nm) and high surface area, could achieve the highest photocatalytic glucose conversion (75%). Yields of gluconic acid, arabinose, xylitol, and formic acid obtained from 20%TiO2/ZeY were 9%, 26%, 4%, and 35%, respectively. For the effect of the silica to alumina ratio, the highest glucose conversion was obtained from SiO2:Al2O3 ratio of 100. Interestingly, it was found that the SiO2:Al2O3 ratio affected the selectivity of carboxylic products (gluconic acid and formic acid). At a low ratio of silica to alumina (SiO2:Al2O3 = 10), higher selectivity of the carboxylic products (gluconic acid = 29% and formic acid = 32%) was obtained (compared with other higher ratios). TiO2/ZeY was further loaded by metals using the microwave-assisted incipient wetness impregnation technique. The highest glucose conversion of 96.9 % was obtained from 1 wt. % Ag-TiO2 (40%)/ZeY. Furthermore, the bimetallic Ag-Cu-loaded TiO2/ZeY presented the highest xylitol yield of 12.93%.
Highlights
Nowadays, biomass is an important feedstock that can be used for chemical production
The effect of TiO2 dosages on Zeolite type Y (ZeY) (TiO2 /ZeY) on the physical and chemical properties of the samples was studied via a number of characterizations
It was found that the characteristic morphology of ZeY changed with increasing TiO2 content, because TiO2 was dispersed on the ZeY surface [16,17]
Summary
Biomass is an important feedstock that can be used for chemical production. The main advantage of biomass is zero CO2 emission [1]. The biomass has three main components, which are cellulose, hemicellulose, and lignin. Glucose is a sugar monomer in the structure of cellulose that is one of biomass derivatives. Many researches into glucose conversion are extensively studied in oxidation reactions to obtain high value products (e.g., gluconic acid, arabinose, xylitol, etc.). The synthesis of high value products from biomass can be performed via platform molecules, which can be used as building blocks for biorefinery. From a previous study of platform molecules, Catalysts 2020, 10, 423; doi:10.3390/catal10040423 www.mdpi.com/journal/catalysts
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