دانلود رایگان مقاله لاتین سنتز سبز فوتوکاتالیستی ویتامین b3 از سایت الزویر
عنوان فارسی مقاله:
سنتز سبز فوتوکاتالیستی ویتامین B3 توسط فوتوکاتالیست پلاتین بار TiO2
عنوان انگلیسی مقاله:
Green photocatalytic synthesis of vitamin B3 by Pt loaded TiO2 photocatalysts
سال انتشار : 2017
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مقدمه انگلیسی مقاله:
1. Introduction
Heterogeneous photocatalysis by TiO2 fulfils the principles of Green Chemistry as the experiments are generally carried out in water at ambient temperature and under sunlight by using oxygen from air as the oxidant [1]. A semiconductor such as TiO2 is very suitable for green photocatalysis as it is very effective, cheap and stable to photocorrosion [2]. Using oxygen from air without doing any purification is very simple, economic and hazardless. Water is also very cheap, sustainable and un-flammable solvent [3]. By considering that fossil fuels will end near future, using sunlight as energy source becomes a very important challenge for mankind. In addition, working at room temperature and pressure decreases energy requirement and costs for reactor security. Heterogeneous photocatalysis has been mainly employed to oxidise organic and inorganic pollutants in liquid or gaseous phases[2]. The oxidation reaction in water, due mainly to primary oxidant species as hydroxyl radicals, has been considered unselective and therefore synthesis reactions generally have been carried out in organic solvents [4]. Photocatalytic selective oxidation of benzyl alcohol derivatives [5], 5-(hydroxymethyl)-2-furaldehyde [6], amines [7], piperonyl alcohol [8], trans-ferulic acid [9], isoeugenol [10], and glycerol[11] or selective cyclization of aromatic acids [12] are examples of synthetic reactions performed in water. It is well known that Pt loading of TiO2 photocatalysts increases the activity both under UV and visible irradiation [7,12]; in fact Pt loading decreases the electron-hole recombination rate and therefore the reaction rate increases. By using metal loaded TiO2, photocatalytic reactions under visible or sunlight irradiation have been generally performed for degrading harmful compounds [13], some investigationshaving beenalso carried outtoperformorganic syntheses in organic solvents [14]. For instance photocatalytic oxidation of aniline to nitrosobenzene has been selectively (90%) performed by using Pt-loaded TiO2 in toluene and under visible irradiation [14c]. Vitamin B3 (pyridine-3-carboxylic acid), whose world production is around 35,000 tons per year [15], is generally used in theprevention and treatment of pellagra disease. Industrially vitamin B3 and other pyridine carboxylic acids are produced at high pressure by oxidation of picolinic isomers using nitric acid, permanganate or chromic acid and vanadia-titania-zirconia oxide supported catalysts [15]. Justthree research papers were published on the photocatalytic selective oxidation of 3-pyridine-methanol [16,17] and its derivatives [15] to their corresponding aldehydes and acids. These reactions were performed in water, under acidic conditions (pH 1–4) [15–17] and using commercial TiO2 [15,17] and TiO2-graphen-like [16] composite photocatalysts. In addition, the reactions were performed under de-aerated conditions using cupric ions as electron acceptor in order to minimize the electron-hole recombination. pH and temperature influence on 3-pyridine-methanol oxidation was also investigated [15]. It was found that temperature effect was negligible for products yields while, by increasing pH from 1 to 4, both aldehyde and vitamin B3 yields and Cu2+ ions conversion decreased. In these works, high total selectivity values were obtained, being selectivities to aldehyde higher than those to acid. Selective production of pyridinecarboxaldehydes from methylpyridine isomers was also performed under de-aerated conditions in acetonitrile or acetonitrile-water solvents [18]. The obtained results show thatthe reactivity is strongly dependent on the photocatalyst properties. In our recent work selective photocatalytic oxidation of 4- methoxybenzyl alcohol and 4-nitrobenzyl alcohol was performed in water under simulated solar light by using Pt, Au, Pd and Ag loaded Degussa P25 TiO2 catalysts [19]. The best activity and selectivity results were obtained with Pt-loaded (0.5%) TiO2 and the highest aldehyde selectivities were reached at low pH’s. Signifi- cant amount of 4-nitrobenzoic acid (ca. 50%) was obtained only from 4-nitrobenzyl alcohol at high pH values. In this work, differently from the previously cited works [15–17,19], Pt-loaded home prepared (HP) TiO2 photocatalysts were used for selective oxidation of 2, 3 and 4-pyridinemethanol to its corresponding aldehyde and acid in water. Oxygen from atmospheric air was used as oxidant; the influence of different light sources (UV, UV–vis and visible) on substrate degradation rates and products selectivities was also investigated for different pH’s (2–12). The optimal amountto be loaded on TiO2 was already investigated [19] and this amount (0.5%) has been used for the TiO2 samples of this work.
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کلمات کلیدی:
Chemical Science - RSC Publishing - Royal Society of Chemistry pubs.rsc.org › Journals Versatile routes for synthesis of diarylamines through acceptorless dehydrogenative ... nonadiabatic molecular dynamics simulations (NAMD) of photocatalytic water oxidation by small ... SABRE hyperpolarisation of vitamin B3 as a function of pH. Alexandra M Olaru, Michael J Burns, Gary GR Green and Simon B Duckett. Energy and Molecules from Photochemical/Photocatalytic ... - MDPI www.mdpi.com/1420-3049/20/1/1527/htm by D Ravelli - 2015 - Cited by 7 - Related articles Jan 16, 2015 - The green role of photochemistry/photocatalysis is rather that of forming ... Toxins - Organic and Analytical Chemistry, Vitamins, Organic Iodine .... Introduction: Photochemistry for Synthesis and Energy .... the data reported) at the G3(MP2)B3 level (see Supplementary Materials for the computational details). Selective Photocatalytic Oxidation of Aniline to Nitrosobenzene by Pt ... acs.jce.ac.il/doi/abs/10.1021/cs500447n Selective photocatalytic oxidation of aromatic alcohols in solar-irradiated ... Green photocatalytic synthesis of vitamin B3 by Pt loaded TiO2 photocatalysts. Heterogeneous Photocatalysis and Photoelectrocatalysis: From ... acs.jce.ac.il/doi/abs/10.1021/acs.jpclett.5b00294 Apr 30, 2015 - Dimethyl carbonate has been proposed as an alternative green organic ... Green photocatalytic synthesis of vitamin B3 by Pt loaded TiO2 ... Top 10 Foods Highest in Vitamin B3 (Niacin) - HealthAliciousNess . com https://www.healthaliciousness.com/articles/foods-high-in-niacin-vitamin-B3.php Vitamin B3, or Niacin, is an essential vitamin required for processing fat in the ... turkey, pork, liver, peanuts, beef, mushrooms, green peas, sunflower seeds, and ... CHEM6103 | Sustainable Chemistry | University of Southampton www.southampton.ac.uk/courses/modules/chem6103.page More specifically, it will provide an overview of the fundamental principles of Green Chemistry and its applicability in Sustainable Chemical Processes Lecture ...
