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Clarifying solvent effect during photocatalytic glycerol conversion on TiO₂/GQD as selective photocatalyst.

ABSTRACT: Nowadays, dealing with the growing chemical and energy demands is important without compromising the environment. So, this work studies photocatalytic glycerol conversion (as biomass derivativ feedstock) into value-added products using an eco-friendly synthesized catalyst. Graphene quantum dots (GQDs) were prepared from available/cheap precursors like glucose via the hydrothermal method and used as a support for TiO₂. TiO₂/GQDs were characterized via different analytical techniques, revealing very small particle sizes of ~ 3-6 nm with a large surface area of ~ 253 m²/g and a band gap of ~ 2.6 eV. The prepared photocatalyst shows good efficiency during photocatalytic glycerol conversion to dihydroxyacetone (DHA). Different reaction conditions were tested: reaction time, catalyst amount, presence of oxidant (H₂O₂), and biphasic media (aqueous/organic phases). Comparing a monophasic (H₂O) photoreactor with a biphasic reactor containing 90% organic phase (ethyl acetate) and 10% aqueous phase (H₂O and/or H₂O₂) indicates that the presence of H₂O₂ increases glycerol conversion and liquid selectivity to reach 57% and 91%, respectively after 120 min. However, it still suffers a low DHA/GA ratio (2.7). On the other hand, using a biphasic reactor in the presence of an H₂O₂ oxidant increases the DHA/GA ratio to ~ 6.6, which was not reached in previous research. The formation of H₂O/H₂O₂ as micro-reactors dispersed in the ethyl acetate phase increased the average light intensity effect of the glycerol/photocatalyst system in the micro-reactors. Unlike previous work, this work presents a facile way to prepare eco-friendly/cheap (noble metal free) photocatalysts for glycerol conversion to ultrapure DHA using a biphasic photoreactor.

SUBMITTER: Hassan S

PROVIDER: S-EPMC10710419 | biostudies-literature | 2023 Dec

REPOSITORIES: biostudies-literature

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Clarifying solvent effect during photocatalytic glycerol conversion on TiO2/GQD as selective photocatalyst.

Hassan Sara S El-Hafiz Dalia R Abd DRA Abdullah E S ES Khalil Mostafa M H MMH

Scientific reports 20231209 1

Nowadays, dealing with the growing chemical and energy demands is important without compromising the environment. So, this work studies photocatalytic glycerol conversion (as biomass derivativ feedstock) into value-added products using an eco-friendly synthesized catalyst. Graphene quantum dots (GQDs) were prepared from available/cheap precursors like glucose via the hydrothermal method and used as a support for TiO2. TiO2/GQDs were characterized via different analytical te ...[more]

PMID: 38071356

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Project description:Nanotube/nanowire-structured TiO2 was formed on the Ti surface by an anodic oxidation method performed at different potential values (50 or 60 V) and for different times (3 or 5 h). The TiO2 photocatalysts were taken in powder form using the ultrasonic treatment from the Ti electrodes, calcined at different temperatures, and characterized by XRD and SEM techniques, and BET surface area analyses. Both the crystallinity and the size of the primary TiO2 particles increased by increasing the heat treatment temperature. While all the photocatalysts heat treated up to 500°C were only in the anatase phase, the particles heat-treated at 700°C consisted of both anatase and rutile phases. The BET specific surface area of the samples decreased drastically after heat treatment of 700°C because of partial sinterization. SEM analyses indicated that the prepared materials were structured in both nanotubes and nanowires. They were tested as photocatalysts for the selective oxidation of glycerol and 3-pyridinemethanol under UVA irradiation in water at room temperature and ambient pressure. Glyceraldehyde, 1,3-dihydroxyacetone, and formic acid were determined as products in glycerol oxidation, while the products of 3-pyridinemethanol oxidation were 3-pyridinemethanal and vitamin B3. Non-nanotube/nanowire-structured commercial (Degussa P25 and Merck TiO2) photocatalysts were used for the sake of comparison. Low selectivity values towards the products obtained by partial oxidation were determined for glycerol. On the contrary, higher selectivity values towards the products were obtained (total 3-pyridinemethanal and vitamin B3 selectivity up to ca. 90%) for the photocatalytic oxidation of 3-pyridinemethanol. TiO2 photocatalysts must be highly crystalline (calcined at 700°C) for effective oxidation of glycerol, while for the selective oxidation of 3-pyridinemethanol it was not necessary to obtain a high crystallinity, and the optimal heat treatment temperature was 250°C. Glycerol and its oxidation products could more easily desorb from highly crystalline and less hydroxylated surfaces, which would justifies their higher activity. The prepared photocatalysts showed lower activity than Degussa P25, but a greater selectivity towards the products found.

Project description:TiO2 nanofibers were fabricated by combination of sol-gel and electrospinning techniques. Ag-doped TiO2 nanofibers with different Ag contents were prepared by two different methods (in situ electrospinning or wetness impregnation of Ag on TiO2 nanofibers) and heat treated at 500 °C for 2 h under an air or N2 atmosphere. The obtained catalysts were characterized by field emission scanning electron microscopy, X-ray diffraction, photoluminescence, and N2 adsorption analyzed by the Brunauer-Emmett-Teller (BET) method. Photocatalytic glucose conversions with electrospun TiO2 and Ag-doped TiO2 nanofibers for production of high-value products were carried out. From different doping methods, the results indicated that 1 wt % Ag-TiO2 nanofibers prepared by an in situ method with calcination under N2 achieved the highest glucose conversion (85.49%). From several Ag loading contents (i.e., 0, 1, 2, and 4 wt %) in Ag-doped TiO2 nanofibers, the nanofibers exhibited different glucose conversions [in order of 2 wt % (99.65%) > 1 wt % (85.49%) > 4 wt % (77.72%) > 0 wt % (29.64%)]. Arabinose, xylitol, gluconic acid, and formic acid were found as the high-value chemicals with the photocatalytic reaction of TiO2 and Ag-doped TiO2 nanofibers under UVA irradiation. Product yields of each converted chemicals from different photocatalysts from different Ag loading contents showed relatively same trends with the glucose conversion. From all results, it can be concluded that the good characteristics of 2 wt % Ag-TiO2 nanofibers such as the smallest anatase crystallite size (8.25 nm) and the highest specific surface area (S BET = 53.69 m2/g) promoted the highest photocatalytic activity. Additionally, TiO2 and Ag-doped TiO2 nanofibers exhibited higher photocatalytic performance for glucose conversion than commercial TiO2 (P25) and synthesized TiO2 nanoparticles. Finally, Ag-doped TiO2 nanofibers showed recycling ability with high photocatalytic glucose conversion after four-time use.

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Clarifying solvent effect during photocatalytic glycerol conversion on TiO₂/GQD as selective photocatalyst.

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Clarifying solvent effect during photocatalytic glycerol conversion on TiO<sub>2</sub>/GQD as selective photocatalyst.

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