Enhancing selectivity in photocatalytic formation of p-anisaldehyde in aqueous suspension under solar light irradiation via TiO2 N-doping

The photocatalytic partial oxidation of 4-methoxybenzyl alcohol to the corresponding aldehyde (p-anisaldehyde) was performed under simulated solar irradiation by using home prepared N-doped TiO2 catalysts. The photocatalysts were prepared by a sol–gel method, using TiCl4 as TiO2 precursor and NH4Cl, urea or NH4OH as N-doping sources. A commercial TiO2 (Degussa P25) was also used for comparison aims. The prepared catalysts were characterized by BET specific surface area, XRD, ESEM and UV-vis spectroscopy. The reactivity results show that (i) the doped catalysts are predominantly amorphous, and they show selectivity values far higher than those of the corresponding undoped ones and of well crystallized catalysts – even if the last ones show a higher activity – and (ii) exploitation of solar light significantly increases the reaction selectivity. In addition, different light sources were also used in order to investigate the effect of radiation wavelength ranges on the reactivity and selectivity to aldehyde

Overview on oxidation mechanisms of organic compounds by TiO2 in heterogeneous photocatalysis

This review provides the reader with a general overview on heterogeneous photocatalytic oxidation mechanisms in the presence of TiO2, with a special address to conversion of aliphatic and aromatic organic species. The aim was to clarify the steps of the photo-oxidation of the various classes of compounds and to relate them with the properties of the catalysts and the experimental conditions used. Reactions carried out to perform complete degradation and photocatalytic partial oxidations have been deeply discussed. Recent isotopic studies highlighted new reaction pathways concerning partial oxidation of alcohols to aldehyde and oxidation of benzene while EPR investigations confirmed that not only the photogenerated hole but also the OH radicals are involved in the oxidation of the substrates

Photocatalytic selective oxidation of 5-(hydroxymethyl)-2-furaldehyde to 2,5-furandicarbaldehyde in water by using anatase, rutile and brookite TiO2 nanoparticles

5-(Hydroxymethyl)-2-furaldehyde (HMF) was selectively oxidized to 2,5-furandicarbaldehyde (FDC) in aqueous medium by using home-prepared (HP) anatase, rutile, and brookite TiO2 nanoparticles. HP samples were prepared via a sol−gel method by using TiCl4 as the TiO2 precursor. Commercial TiO2 catalysts were also used for comparison. All samples were characterized by BET specific surface area, XRD, TGA, and SEM, and the reactivity results showed that HP catalysts are predominantly amorphous and give rise to selectivities toward FDC more than twice that of commercial and well-crystallized catalysts

Extruded Expanded Polystyrene Sheets Coated by TiO2 as New Photocatalitic Materials for Foodstuffs Packaging

Nanostructured, photoactive anatase TiO2 sol prepared under very mild conditions using titanium tetraisopropoxide as the precursor is used to functionalise extruded expanded polystyrene (XPS) sheets by spray-coating resulting in stable and active materials functionalised by TiO2 nanoparticles. Photocatalytic tests of these sheets performed in a batch reactor in gas–solid system under UV irradiation show their successful activity in degrading probe molecules (2-propanol, trimethylamine and ethene). Raman spectra ensure the deposition of TiO2 as crystalline anatase phase on the polymer surface. The presence of TiO2 with respect to polymer surface can be observed in SEM images coupled to EDAX mapping allowing to monitor the surface morphology and the distribution of TiO2 particles. Finally thermoforming of these sheets in industrial standard equipment leads to useful containers for foodstuffs

Selective photooxidation of ortho-substituted benzyl alcohols and the catalytic role of ortho-methoxybenzaldehyde

It has been recently reported by Palmisano et al. (2015) [1] that the oxidation of 2-methoxybenzyl alcohol (2-MBA) to 2-methoxybenzaldehyde (2-MBAD) proceeds in water under near-UV light with an unexpected catalytic effect of 2-MBAD. In order to investigate the catalytic role of aldehyde in photolytic oxidation of ortho-substituted benzyl alcohols (OSBAs), reactivity runs were carried out with 2-methylbenzyl alcohol (2-MeBA), 2-nitrobenzyl alcohol (2-NBA), 2-hydroxybenzyl alcohol (2-HBA) and 2-chlorobenzyl alcohol (2-ClBA) in the absence and in the presence of their corresponding aldehyde. None of those alcohols showed a measurable oxidation rate even in the presence of their aldehydes but 2-NBA was oxidised very fast, although no corresponding carbonyl product was obtained. The possible catalytic role of 2-MBAD was investigated for the photolytic oxidation of 4-methoxybenzyl alcohol (4-MBA), 4-nitrobenzyl alcohol (4-NBA), 2-ClBA, 2-HBA, 2-MeBA and ferulic acid (FA). The results showed that 2-MBAD acts as a catalyst only for 4-MBA, 2-HBA and FA. The photocatalytic oxidation of OSBAs in the presence of powdered TiO2 has been also carried out in order to investigate the mutual influences, if any, between homogeneous and heterogeneous processes. The reactivity runs were carried out with TiO2 photocatalyst in water and under near-UV irradiation; a home-prepared (HP) TiO2 sample was used along with Degussa P25. HP catalyst showed the best performance: the 2-MBA half-life time was 5 times smaller and the selectivity to aldehyde 13 times higher than in the presence of Degussa P25

Synthesis and characterization of titanium dioxide and titanium dioxide-based materials

The aim of the chapter is to describe some different preparation methods and characterization techniques for bare, supported, and coupled TiO2 samples used in different fields. Particular attention has been paid both to the fundamental aspects of the different TiO2 preparation and characterization methods and the practical applications that the results obtained can have. Various examples have been reported from the literature to demonstrate the usefulness that students and scientists working with TiO2-based materials in different research areas can derive from various characterizations

From the perspective of preservice teachers, the accomplishment levels of primary school teachers’ effective teacher attitudes in science lessons

The aim of this study is to determine to what extent the Primary School Teachers can accomplish the effective teacher attitudes in science lessons. In this context, the observations of 83 primary school preservice teachers, who studied teaching practice course, have been used. In order to determine the accomplishment levels of primary school teachers’ effective teacher attitudes in science lessons, the preservice teachers have been asked to observe the primary school teachers in the schools they attend for the practice lessons and the accomplishment levels of science education teacher’seffective teacher attitudes has been determined via an observation form including 25 questions in total. Descriptive- survey research has been used in the study and the data have been analyzed through frequency and percentage. When the findings of the study have been evaluated in terms of the preservice teachers' observations, it has been concluded that the teachers prepare the setting for the active participation of all the students in the lesson and they are tolerant for the mistakes the students make during the learning process. However, it has also been concluded that the teachers do not state the objectives of the lesson clearly and definitely, they do not take the interest levels of the students into consideration and they do not spare enough time for the students to think about the answers after they ask the questions. © The Turkish Online Journal of Educational Technology

Heterogeneous photocatalysis from fundamentals to possible applications

This special issue of Catalysis Today Journal, is dedicated to the career of Prof. Vincenzo Augugliaro, University of Palermo, Italy, in the occasion of his retirement in 2015. Prof. Vincenzo Augugliaro was Full Professor of Transport Phenomena at the University of Palermo (Italy) since 1994. He contributed to the fol- lowing research fields: chemical absorption kinetics, biochemical reactor modelling, diffusional kinetics in metallizing alloys and heterogeneous photocatalysis; in this last field he investigated on chemical kinetics of heterogeneous photocatalytic systems, modelling of heterogeneous photoreactors, radiation field in absorbing-reacting media and application of heterogeneous pho- tocatalysis to syntheses processes. He published more than 150 papers in prestigious journals and many chapters in books and is co-author of 4 patents. Prof. Augugliaro was appreciated not only for his important achievements in the field of heterogeneous photocatalysis, but also for his great effort as mentor of many master and PhD chemical engineering students. This special issue contains twenty-four original papers by researchers involved in various aspects of heterogeneous photocatalysis

A quantitative method of photoadsorption determination for irradiated catalyst in liquid-solid system

A method for determining the amount of substrate adsorbed onto the catalyst surface in liquid-solid photocatalytic system under reaction conditions (photoadsorption) is proposed. The method has been applied to the photocatalytic oxidation of benzyl alcohol carried out in aqueous suspensions of a home prepared TiO2 catalyst. The influence of alcohol concentration, catalyst amount and irradiation power on photoadsorption was investigated. The photoadsorption per unit mass of catalyst increased by increasing concentration of benzyl alcohol and irradiation power but it decreased, increasing the catalyst amount. By taking into account the photoadsorption phenomena, the kinetic modeling of the photooxidation process has been carried out and the parameters of the model have been determined. The results indicate that all these parameters are favorably affected by an increase of the photon flow absorbed per unit mass of catalyst

Nanostructured Rutile TiO2 for Selective Photocatalytic Oxidation of Aromatic Alcohols to Aldehydes in Water

Selective photocatalytic oxidation of aromatic alcohols to aldehydes was performed in water in the presence of TiO2 rutile photocatalysts that exhibited a low degree of crystallinity. The nanostructured rutile samples, prepared ex TiCl4 at very low temperature, ensured a selectivity toward the aldehyde 3 to 4-fold higher than the commercial rutile tested (Sigma-Aldrich)