Photo Catalytic Oxidation of Benzyl Alcohol to Benzyl Aldehyde using Synthesized Zinc Oxide and Zinc Doped Titanium Oxide
Received: 01-Jul-2024 / Manuscript No. ico-24-139275 / Editor assigned: 04-Jul-2024 / PreQC No. ico-24-139275(PQ) / Reviewed: 17-Jul-2024 / QC No. ico-24-139275(QC) / Revised: 25-Jul-2024 / Manuscript No. ico-24-139275(R) / Accepted Date: 30-Jul-2024 / Published Date: 30-Jul-2024
Abstract
Photo catalytic oxidation of alcohols to carbonyl compounds amongst various organic transformations is important due to its significant role in the synthesis of a variety of fine chemicals, confectionaries, fragrances, and pharmaceuticals. This Study explores the Comparative Photo catalytic activity of synthesized Zinc oxide and Zinc doped Titanium oxide, for the photo catalytic oxidation of aromatic alcohol to aldehyde. Un-doped and doped zinc oxide (Zn-doped TiO2 photo catalyst) were prepared using hydrothermal method. The photo catalytic performance of the synthesized photo catalyst was evaluated for the conversion of Benzyl alcohol to Benzyl aldehyde. Powdered X-Ray Diffractometer was used to characterize the synthesized product. Gas Chromatography - Flame ionization Detector was employed to access the photo catalytic conversion activity of Benzyl alcohol (BA) via UV-Visible irradiation. It was possible to achieve about 40% conversion of the alcohol and 80% of selectivity of the products. This research further enlightens comparative view of using hydrothermally synthesized Zinc oxide and Zn-TiO2 as photo catalyst in the organic synthesis of aromatic hydrocarbons such as benzyl alcohol, where Zinc doped titanium oxide yields more Selectivity of the product compared to the un-doped photo catalyst.
keywords
Photo catalysis; Hydrothermal; Benzyl alcohol; Benzyl aldehyde; UV-visible irradiation
Introduction
The conversion of alcohols into carbonyl compounds through selective oxidation is a crucial process in organic chemistry. However, this transformation has traditionally been carried out using hazardous and toxic stoichiometric oxidants under harsh conditions such as high temperatures and pressures as reported by relevant literatures. Recently, ultra-violet/visible light-driven organic photochemical synthesis has been a versatile research interest area as researchers covering the academia and Industry due to the unique features of green and sustainable chemistry. The Visible region is useful to perform many green organic photochemical reactions under catalytic conditions due to its sustainable and abundant nature [1]. Various research areas have been prompted by the characteristic property of photo catalyst in achieving the aim of green chemistry in the modern world today [2]. This photo catalyst which are formulated and synthesized using different mediums are evident to many plausible reactions and synthesis ranging from Water Treatment, Degradation of Organic waste, green photo catalytic oxy- functionalization of organic compounds and selective organic transformations under environmentally friendly conditions [3]. ZnO nanoparticle has extensive applications in system and processes of biosensors, gaseous sensors, solar cells, ceramics, nano generators, photo detectors, catalyzers, ultraviolet (UV) adsorbents in cosmetic and veneer of antivirus, pigments, optical materials, photocatalyst, electrical and optical processes [4]. Aldehyde compounds are indispensable substances for drugs, fragrances and organic synthesis in the chemical industry, and they are generally produced through reduction of corresponding carboxylic acids or oxidation of corresponding alcohols [5]. The production of aldehydes is conducted in environmentally harmful organic solvents with the use of stoichiometric oxygen donors such as KMnO4 and CrO3 [6]. Since these reagents are toxic and expensive and produce a large amount of waste, the process should be replaced with a more environmentally friendly method. Photo catalysis is a promising technique for environmental remediation due to its ability to degrade organic pollutants under mild conditions. Several Reports has employed several matrices inclusive of ZnO, TiO2 as photo catalyst due to its high chemical stability, low toxicity, and low cost [7,8].
This research works deals with selective oxidation reaction, which is important from the viewpoint of green and sustainable chemistry in controlling the release of toxic waste. Photo catalytic oxidation as one of the advanced oxidation processes (AOPs) due to strong decomposition characteristic of hydroxyl radicals in removal of organic pollutant has attracted much attention [9]. In view of this, the electron gap generation by the catalyst helps in the oxidation of organic reaction, thereby causing conversion. Various catalysts can be used in photo catalytic process. The primary aim of this study is to examine the potential of synthesized zinc oxide and Zinc doped Titanium oxide as a photo catalyst for converting benzyl alcohol into benzyl aldehyde.
Methodology
Preparation of ZnO nanoparticle
1.3g Zinc Acetate was dissolved in 50 mL distilled water. Separately, 1g of NaOH was dissolved in 50 mL Ethanol. A magnetic Stirrer was used to yield homogeneity of the solution. Then, NaOH(aq) was added drop wise to the Zinc Acetate Solution and allowed to stir for 1hr. The final mixture was transferred to an autoclave and placed in an Oven at 95oC for 2hrs. The mixture was then filtered and rinsed with distilled water, then placed in an oven to dry at 60oC. The obtained powder was then annealed at 400oC to improve the crystal structure. The whole process was repeated as required using 0.65g of Zinc Acetate which was weighed into a 250mL beaker. The Powder was then characterized using XRD.
Preparation of ZnO doped TiO2 nanoparticle
Hydrothermally Synthesized Zinc Oxide was mixed with Commercial TiO2 powder at 0.1 – 1% of ZnO. A magnetic Stirrer was used to yield homogeneity of the solution. Then, NaOH(aq) was added drop wise to the Solution and allowed to stir for 1hr. The final mixture was transferred to an autoclave and placed in an Oven at 95oC for 2hrs.
The mixture was then filtered and rinsed with distilled water, then placed in an oven to dry at 60oC. The obtained powder was then annealed at 400oC.
Alcohol conversion
Photo catalytic conversion using synthesized Zn-TiO2
1g of the Synthesized catalyst (ZnO/TiO2) was placed in a 50mL Conical Flask containing 100mL of Distilled water as solvent and 20micro Liter of Benzyl alcohol and placed in the UV Chamber, for 5 mins, 10 mins, 15 mins, 20 mins, 25 mins and 30 mins. At each run, the process was repeated using 0.5g, 1g, 1.5g and 2g of the photo catalyst. The Result of each process per time was transferred in a clean amber reagent bottle for GC-FID analysis of the resulting product.
Photo catalytic conversion using synthesized ZnO
0.051g of the Synthesized catalyst (ZnO) was placed in a 50mL Conical Flask containing 100mL of Distilled water as solvent and 20micro Liter of Benzyl alcohol and placed in the UV Chamber, for 5min, 10mins, 15mins, 20mins, 25mins and 30mins. At each run, the process was repeated using 0.5g, 1g, 1.5g and 2g of the photo catalyst. The Result of each process per time was transferred in a clean amber reagent bottle for GC-FID analysis of the resulting product.
Photo catalytic activity of the synthesized particles in oxidation of benzyl alcohol to benzyl aldehyde
The Photo catalytic activity of the Synthesized ZnO and Zn-doped Titanium Oxide were studied by the use of Gas Chromatography-Flame Ionization Detector, using a plot of Concentration (mMol/L) vs Time (min). The purpose of the experiment, which is to investigate the photo catalytic oxidation of benzyl alcohol to benzyl aldehyde using ZnO and Zn-TiO2 nanoparticles as catalysts.
The photo catalytic conversion of BA (Benzyl alcohol) using ZnO and Zn-TiO2 respectively with respect to Catalyst Loading at 0.5g, 1.0g, 1.5g and 2g. Catalyst loading at 0.5g of ZnO for BA conversion was observed at high concentration and BA was converted on a steady state with initial time 0 – 4 mins, after which a considerable decline was observed in the plot with increase time, whereas at 2.0 ZnO catalyst loading, the conversion of BA occurred rapidly and further conversion was completed with increased time. This implies that Catalyst loading of ZnO at 2.0g shows high or preferential BA photo catalytic conversion.
Catalyst loading of Zn-TiO2 at 0.5g for BA conversion was not efficient as the conversion experienced less conversion rate as seen in the plot. Whereas Catalyst loading of Zn-TiO2 at 2.0g for BA conversion was sharp and occurred in a steady state with increase in time. Thus for Zn-TiO2 catalyst loading at 0.5g the conversion is low whereas for catalyst loading at 2.0g, the BA Conversion rate is efficient.
Photo catalytic activity of the synthesized particles in oxidation of benzyl alcohol to benzyl aldehyde
The Photo catalytic activity of the Synthesized ZnO and Zn-doped Titanium Oxide were studied by the use of Gas Chromatography-Flame Ionization Detector, using a plot of Concentration (mMol/L) vs Time (min).
The purpose of the experiment, which is to investigate the photo catalytic oxidation of benzyl alcohol to benzyl aldehyde using ZnO and Zn-TiO2 nanoparticles as catalysts.
The photo catalytic conversion of BA (Benzyl alcohol) using ZnO and Zn-TiO2 respectively with respect to Catalyst Loading at 0.5g, 1.0g, 1.5g and 2g. Catalyst loading at 0.5g of ZnO for BA conversion was observed at high concentration and BA was converted on a steady state with initial time 0 – 4 mins, after which a considerable decline was observed in the plot with increase time, whereas at 2.0 ZnO catalyst loading, the conversion of BA occurred rapidly and further conversion was completed with increased time. This implies that Catalyst loading of ZnO at 2.0g shows high or preferential BA photo catalytic conversion. Catalyst loading of Zn-TiO2 at 0.5g for BA conversion was not efficient as the conversion experienced less conversion rate as seen. Whereas Catalyst loading of Zn-TiO2 at 2.0g for BA conversion was sharp and occurred in a steady state with increase in time. Thus for Zn-TiO2 catalyst loading at 0.5g the conversion is low where as for catalyst loading at 2.0g, the BA Conversion rate is efficient.
Conclusion
Although TiO2 has been thoroughly investigated as an effective photo catalyst, ZnO has been considered a suitable alternative since it is less expensive and possesses a similar band gap (∼3.3 eV). Zinc doped Titanium oxide has been reported to produce better oxidation in terms of percentage conversion and selectivity of BA due to the higher efficiency of photo excitation under Uv-visible light. Furthermore, ZnO and Zn-TiO2 synthesized using Hydrothermal Method provides a suitable and cost effective method of synthesis, and the resultant material synthesized was crystalline with Wurzite structure as confirmed by XRD analysis. To further improve the photo activity, there is a need to increase the photo catalyst surface area, for optimal mass transfer and efficient dye degradation, without additional equipment cost in catalyst separation from water.
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Citation: Abutu IO (2024) Photo Catalytic Oxidation of Benzyl Alcohol to Benzyl Aldehyde using Synthesized Zinc Oxide and Zinc Doped Titanium Oxide. Ind Chem, 10: 289.
Copyright: © 2024 Abutu IO. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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