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See detailCatalytic reforming of gasification tars with bi- and trimetallic catalysts optimized with organosilane precursors
Claude, Vincent ULg; Lambert, Stéphanie ULg

Poster (2017, March 07)

Biomass gasification is interesting for the production of CO + H2 from wastes and catalysts are necessary for tars degradation. Catalysts were synthesized by the sol-gel process to develop γ-Al2O3 doped ... [more ▼]

Biomass gasification is interesting for the production of CO + H2 from wastes and catalysts are necessary for tars degradation. Catalysts were synthesized by the sol-gel process to develop γ-Al2O3 doped with 10%wt of nickel and 2 wt.% of a second dopant (Co, Cu, Fe, Mn, Mo). Before their adding in AlOOH sol, metallic dopants were complexed with (OCH3)3-Si-(CH2)3-NH-(CH2)2-NH2 (EDAS) to increase their dispersion by cogelation between EDAS and AlOOH clusters. These catalysts were tested at 650°C for toluene reforming. [less ▲]

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See detailEthylene polymerization and hydrodechlorination of 1,2-dichloroethane mediated by nickel(II) covalently anchored to silica xerogels
Mahy, Julien ULg; Claude, Vincent ULg; Sacco, Luigi et al

in Journal of Sol-Gel Science and Technology (2017), 81(1), 59-68

Ni/SiO2 cogelled xerogel catalysts have been prepared in ethanol containing nickel acetylacetonate, tetraethoxysilane (TEOS), an aqueous ammonia solution of 0.54 mol L-1 and either a commercial sylilated ... [more ▼]

Ni/SiO2 cogelled xerogel catalysts have been prepared in ethanol containing nickel acetylacetonate, tetraethoxysilane (TEOS), an aqueous ammonia solution of 0.54 mol L-1 and either a commercial sylilated ligand, 3-(2-aminoethyl)aminopropyltrimethoxysilane (EDAPMS), or a home-made new silylated pyrazolypyridine ligands, respectively 2-[4-[3-(trimethoxysilyl)propyl]-3,5-dimethyl-1H-pyrazol-1-yl]pyridine (MS-PzPy) and 2-[4-[3-(trimethoxysilyl)propyl]-3,5-dimethyl-1H-pyrazol-1-yl]-6-methylpyridine (MS-PzPyMe), able to form a chelate with a metal ion such as Ni2+. All samples form homogeneous and very highly dispersed Ni/SiO2 cogelled xerogel catalysts. The resulting catalysts are composed of nickel nanoparticles with a diameter of about 2.8 nm, located inside primary silica particles exhibiting a monodisperse microporous distribution. The silylated organic ligand has a strong influence on the textural properties of cogelled xerogel catalysts, both before and after calcination and reduction steps. Changing the nature of the silylated ligand permits tailoring textural properties such as pore volume, pore size and surface area. Homogenous nickel complexes synthesized from pyrazolylpyridine derivatives are inactive for ethylene polymerization. In opposite, heterogenous nickel-based catalysts onto silica xerogel synthesized from pyrazolylpyridine derivatives bearing a tethered trialkoxysilyl group allow increasing ethylene polymerization activity. Although nickel nanoparticles are located inside the silica crystallites, their complete accessibility, via the micropore network, has been shown. For 1,2-dichloroethane hydrodechlorination over Ni/SiO2 catalysts, the conversion of 1,2-dichloroethane is high at the temperature of 350°C and mainly ethane is produced. [less ▲]

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See detailTowards a large scale aqueous sol-gel synthesis of doped TiO2: Study of various metallic dopings for the photocatalytic degradation of p-nitrophenol
Mahy, Julien ULg; Lambert, Stéphanie ULg; Léonard, Géraldine ULg et al

in Journal of Photochemistry and Photobiology A : Chemistry (2016), 329

In this paper, an easy aqueous sol-gel synthesis developed previously by Mahy et al. [J. Sol-Gel Sci. Technol. (2016)] is adapted to produce highly active TiO2 catalysts doped with Fe3+, Ag+, Cu2+, Zn2 ... [more ▼]

In this paper, an easy aqueous sol-gel synthesis developed previously by Mahy et al. [J. Sol-Gel Sci. Technol. (2016)] is adapted to produce highly active TiO2 catalysts doped with Fe3+, Ag+, Cu2+, Zn2+, Cr3+, Al3+, Mn2+, and Co2+ ions and Pt metallic nanoparticles. Samples are characterized by inductively coupled plasma–atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), Mössbauer spectroscopy, transmission electron microscopy (TEM), nitrogen adsorption–desorption measurements and diffuse reflectance spectroscopy measurements. Results show that the samples are composed of anatase-brookite TiO2 nanoparticles with a spherical shape and mean diameter of around 5-8 nm and a surface area of between about 150 - 250 m2 g-1. In each doped sample, the dopant is present in the form added during the synthesis, given that the sample has not undergone any particular treatment. Photoactivity tests show improvement in catalyst activity for Fe3+, Ag+, Cu2+, Zn2+, and Al3+ ion and Pt metallic nanoparticle dopants, while a decrease of activity is obtained for Cr3+, Mn2+ and Co2+ ion dopants. For some dopants, the activity of TiO2 doped with metallic ions and synthesized from the aqueous sol-gel process is equal or superior to the activity of the commercial photocatalyst Degussa P25. Some mechanisms are proposed to explain these modifications of activity with doping. Furthermore, cost comparison at laboratory scale showed that Zn and Cu nitrate salt dopings are clearly less expensive for a halogen light (UV/visible) or low energy light enhanced catalyst and may be considered for industrial applications. Using this method, a large scale Zn-doped TiO2 photocatalyst is synthesized with properties homologous to the lab-scale product. Results show that the aqueous sol-gel synthesis developed previously can be easily adapted for doping in order to produce an up-scalable synthesis. [less ▲]

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See detailIntegrated Project with Focus on Energy Transition and Circular Economy for Developing Engineering Students' Soft Skills
Léonard, Grégoire ULg; Pfennig, Andreas ULg; Toye, Dominique ULg et al

Poster (2016, September 05)

The present work reports the experience of an integrated project developed at the University of Liege for master students in chemical engineering. The goals are to promote the acquisition of soft skills ... [more ▼]

The present work reports the experience of an integrated project developed at the University of Liege for master students in chemical engineering. The goals are to promote the acquisition of soft skills and to consolidate technical knowledge by integrating and linking chemical engineering disciplines usually taught separately. A case study was selected to address some of the challenges related to energy transition: students had to design the energy system of a remote island and make it as energy independent and CO2-neutral as possible by 2030. The course of action during the academic year, the assessment of soft skills, and the tools offered to ease the mentoring and encourage the acquisition of soft skills are described. Not all implemented techniques performed equally well, and this project finally appeared to be a challenge for the teaching team as well. 1 Introduction and background Over the last few years, University authorities, industrial partners as well as national and international experts that evaluated the education quality of our Department (AEQES, CTI) strongly suggested that opportunities should be offered to students to increase their soft skills as part of their curriculum. Moreover, many developments in chemical engineering are related to energy transition and circular economy, which are both transdisciplinary to conventional lectures. In this paper, we present methods and mentoring tools developed to teach students technical and soft skills for multi-disciplinary topics. 2 Description of the integrated project Objectives and constraints were defined at the onset of the project for both technical and soft skills. The technical objective was to propose an energy system that would make Reunion Island as energy independent and CO2-neutral as possible by 2030. This idea originated in the challenge set by the Eurecha 2015 student contest[1], for which students had to design facilities for a sheikhdom: electricity, water recycling, production of fertilizers… In our case, Reunion Island (~850 000 inhabitants) was considered as a case study as it is remote, has large biomass resources and high potential for renewable energies. Besides the objectives mentioned above and in order to force students to look at chemical engineering processes, the treatment of wastewater was imposed as well as the use of a synthetic liquid fuel as energy carrier. The targeted soft skills included working in large groups of minimum 4 students, efficient communication of results in English - both written and oral -, ability to integrate knowledge from various disciplines, development of critical mind and demonstration of independent and creative thinking. 3 Course of actions A team of 8 professors and senior scientists mentored the project and contributed to its assessment. The 10-ECTS project was divided in two parts. In the fall semester, students made global energy balances to design the energy system that would fulfill the objectives. As a result, a Sankey diagram of the energy flows on Reunion Island by 2030 was produced to allow for an overview of the available Island’s resources and needs, as well as of processes that can make the link between resources and needs. In the spring semester, two processes identified in the first part, namely the synthesis of bio-ethanol and bio-methanol, were modelled in more details using commercial software. Different tools were used to encourage student initiatives and work: • The use of a shared on-line portfolio for students to gather their documents improved their internal communication, but this remained a marginal channel for communication with teachers • In the fall semester, students orally presented progress reports every two weeks. After a feedback to students, the teaching team met to discuss the achievements and set the objectives for the next two weeks. This was very positive for the communication inside the teaching team. However, presentations every fortnight implied a work overload for students that had to constantly focus on preparing the presentations. • From the beginning, students were strongly encouraged to reach out to field experts whose contacts were provided. However, they preferred to rely mostly on Internet as their main source of information and reached out only rarely for help and usually very late. • In the fall semester, students had to designate new team leaders in turn every fortnight. This was abandoned as it prevented the establishment of clear structures in the group, reducing its efficiency. • In the spring semester, work tables allowed students to work directly with the teacher specialized in their task. This was appreciated by students and teachers, and it needs to be further encouraged. • Help in the group organization and interactions was provided by the PSGO (psychology of groups and organizations). This also included videoscopy, i.e. filming the students during their presentations and analyzing the records with them. This help was appreciated by students. The assessment was based on technical results for 60%, and soft skills for 40%. The evaluation of technical skills was done partly by all teachers equally and partly by teachers whose expertise was the closest to the technical sub-tasks. For soft skills, efficient communication, creativity in the work and results and links with conventional lectures were assessed. Critical thinking was evaluated through the relevance of qualitative and quantitative results and discussions. Group work was assessed by the teachers as well as by students through mutual evaluation. 4 Conclusions and perspectives The integrated project gave students a first opportunity to improve their soft skills along with their technical knowledge. It also improved their communication skills and their fluency in English. The teaching team proposed different mentoring techniques to encourage efficient work, with varying results. Finally, as the assessment ignored soft skills improvements, it may be modified by evaluating soft skills all year long so both the final result and the observed improvements contribute to the grade. Reference Eurecha, The European Committee for the Use of Computers in Chemical Engineering Education, 2015. Announcement for student contest problem competition 2015. http://bari.upc.es/eurecha/. [less ▲]

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See detailCogelled xerogel catalysts for applications in gazeous phase
Lambert, Stéphanie ULg

Conference (2016, June 15)

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See detailAg/SiO2 and Cu/SiO2 cogelled xerogel catalysts for benzene combustion and 2-butanol deshydrogenation
Mahy, Julien ULg; Claude, Vincent ULg; Tasseroul, Ludivine ULg et al

Poster (2016, June 08)

Tars are recognized as major impurities when biomass is gazified into Syngas (mixture CO + H2) or when the methane reforming was produced from sustainaible reagents [1]. Therefore, fundamental knowledge ... [more ▼]

Tars are recognized as major impurities when biomass is gazified into Syngas (mixture CO + H2) or when the methane reforming was produced from sustainaible reagents [1]. Therefore, fundamental knowledge of catalytic oxidation and deshydrogenation mechanisms can be valuable to develop effective methods to control syngas or methane pollution. A very important concern about cogelled catalysts is the accessibility of the active centers. Because the silver and copper is located inside silica particles, there is a risk that it may not be accessible. In the case of benzene oxidation, it was observed that the specific activity (mol s-1 g-1Ag) of Ag/SiO2 and Cu/SiO2 catalysts increases when the silver or copper loading decreases (Fig. 1). In fact, visual observations by TEM showed that in samples Ag0.25, Ag0.45, Ag1.05 and Cu1.00, there are not silver or copper particles located on silica particles external surface and then the metal dispersion values are greater in these samples. So, it is the proof that Ag and Cu particles located inside the silica particles are accessible for benzene in this catalytic system. In the case of 2-butanol dehydrogenation, the specific activity of Cu/SiO2 catalysts increases when the copper loading increases or when the metal dispersion values decreases (Fig. 2). However, in Cu1.00 sample, copper particles inside silica particles only are observed by TEM. It seems that these metallic particles are accessible for 2-butanol in this catalytic system. [less ▲]

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See detailCatalytic reforming of biomass gasification tars with bi- or tri-doped catalysts optimized with organosilane precursors
Claude, Vincent ULg; Courson, Claire; Heinrichs, Benoît ULg et al

Conference (2016, June 08)

The thermochemical method called “biomass gasification” is generating emphatic interest for the production of bio-Syngas (CO + H2) since this process presents the advantage of being renewable without ... [more ▼]

The thermochemical method called “biomass gasification” is generating emphatic interest for the production of bio-Syngas (CO + H2) since this process presents the advantage of being renewable without emitting CO2. However, in practical applications, there are still some technical problems due to high tars concentration in the outlet gas which can condensate and clog the pipes. Many studies have highlighted the fact that the tar elimination via catalytic reforming seem to be the more practical and economical solution. The required properties of the catalysts are determined by its location: inside the reactor (primary catalyst) or outside of the reactor (secondary catalyst). Primary catalysts are generally robust, non-toxic, cheap and they are almost uniquely destined to fluidized bed reactors. Secondary catalysts can be used at the exit of both fluidized and fixed bed reactors. They are characterized by a tailored mesoporous shape, a controlled active site dispersion and an adapted elemental composition [1]. In this work , we decided to focus on designing materials for secondary catalytic applications, i.e. working at relatively low temperature (~650°C) with no mechanical stress. The supports were made of γ-Al2O3 synthesized via an easy Sol-Gel method. During their synthesis, these supports were doped with 10%wt of nickel and various combinations of metallic dopants (Co, Cu, Fe, Mn, Mo) in the aim of enhancing their catalytic activities and lifetime. [less ▲]

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See detailDevelopment of an easy aqueous sol-gel synthesis for large-scale film deposition methods for the manufacture of coated steel with self-cleaning properties
Mahy, Julien ULg; Léonard, Géraldine ULg; Pirard, Sophie ULg et al

Conference (2016, May 20)

In this work, a global process has been developed to produce at a large scale pure TiO2 films deposited on steel in order to get an easy-to-clean surface. This large scale process implies an easy aqueous ... [more ▼]

In this work, a global process has been developed to produce at a large scale pure TiO2 films deposited on steel in order to get an easy-to-clean surface. This large scale process implies an easy aqueous sol-gel process for the synthesis of the TiO2 sol. This synthesis [1] has been simplified to make easier the extrapolation towards an industrial scale. Results of TEM, photocatalytic properties, film hydrophilicity, and texture obtained with the simplified aqueous sol-gel synthesis (IsoP-TiO2 synthesis) show similar properties than those obtained with the standard aqueous sol-gel synthesis of TiO2 developed previously (HAc-TiO2 synthesis [2]). Only XRD patterns were slightly different with the presence of anatase-brookite phases in IsoP-TiO2 synthesis while anatase phase only was observed in HAc-TiO2 synthesis. Both the aqueous sol-gel synthesis of pure TiO2 and the film deposition on steel by roll-coating have been successfully extrapolated to a larger scale. Indeed, the deposition was done on a pilot line, the steel substrate is 25 cm width, and the band length is 800 m. The coating was deposited at line speed ranging from 30 to 120 m.min-1.The photocatalytic activity and the hydrophilicity of the film were found to be unchanged compared to the films produced at a laboratory scale, thus validating the production of an efficient easy-to-clean material. Even if some problems have still to be solved, this study is a hopeful first step in the development of a large scale process for self-cleaning steel production. [1] S. Mahshid, M. Askari, M.S. Ghamsari, J. Mater. Process. Technol. 189 (2007) 296–300 [2] C.M. Malengreaux, S. Douven, D. Poelman, B. Heinrichs, J.R. Bartlett, J. Sol-Gel Sci. Technol. 71 (2014) 557–570 [less ▲]

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See detailNanoparticles and microorganisms applied in groundwater decontamination
Lambert, Stéphanie ULg; Lavigne, Benoît

Conference (2016, May 13)

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See detailTailoring γ-Al2O3 supports with specific silicon precursors
Claude, Vincent ULg; Vilaseca, Miriam; Heinrichs, Benoît ULg et al

Poster (2016, May 13)

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See detailOverview and Essentials of Biomass Gasification Technologies and their Catalytic Cleaning Methods
Claude, Vincent ULg; Courson, Claire; Köhler et al

in Energy & Fuels (2016), 30(11), 8791-8814

Obtaining a tar-free biosyngas from biomass gasification processes has been the subject of many studies in the past 2 decades, and it still remains the major technologic and economic challenge ... [more ▼]

Obtaining a tar-free biosyngas from biomass gasification processes has been the subject of many studies in the past 2 decades, and it still remains the major technologic and economic challenge. Unfortunately, the countless publications about gasification technologies and different techniques permitting reduction of the tar present at the outlet of gasifier reactors usually confuse inexperienced persons who attempt to further research this subject. More than presenting the basis of biomass gasification technologies and positioning them among other bioenergies, this work mainly aims at reviewing and comparing the different methods developed in order to produce a tar-free biosyngas. In this way, biosyngas quality improvement can be obtained through different operating processes such as reactor designs, gasifying ratios, feedstock, temperature, and space ratio. Since catalytic destruction has proved to be one of the most convenient and efficient ways to eliminate undesirable tars, an important part of this work also highlights the catalytic and deactivating phenomena involved. Furthermore, this work takes inventory of numerous studies conducted to understand the influence of different properties, especially supports and active site compositions, on the tar reforming activities and lifetime of catalyst materials. Thus, this review aims at summarizing basic and more recent improvements applied to biomass gasification processes and catalytic syngas purification. [less ▲]

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See detailAdsorption of terpenes compounds onto palygorskite
GHRAB, Sana; LOUSAIEF, Mabrouk; Cretin, Marc et al

Conference (2016)

The present work aimed to study the processes of the synthesis insecticidal formulation. The active compounds of essential oil of eucalyptus globulus were fixed in the palygorskite by adsorption process ... [more ▼]

The present work aimed to study the processes of the synthesis insecticidal formulation. The active compounds of essential oil of eucalyptus globulus were fixed in the palygorskite by adsorption process. Two samples types of palygorskites were used; raw and modified palygorskite. The palygorskite clays were characterized by several physicochemical techniques including X-Ray Diffraction (XRD) and Fourier Transformed Infra Red (FTIR) analyses. Results show that the raw clay has a fibrous structure with calcite impurities. These structures and physicochemical properties of palygorskite raw and organo-clays give it the potential of material adsorbent. Results show that the adsorption capacity strongly depends on affinity between terpenic compounds and organic cations rather than on interlayer distance of organo-palygorskite clays. The highest adsorption capacity of terpenic compounds is obtained with palygorskite modified by DDDMA. These results revealed the potential utility of the S1-DDDMA as adsorbents for the uptake of terpenic compounds in environmental applications. [less ▲]

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See detailPhotocatalytic decolorization of Gentian Violet with Na-doped (SnO2 and ZnO)
Benhebal, Hadj; Chaib, Messaoud; Crine, Michel ULg et al

in Chiang Mai Journal of Sciences (2016), 42

Photocatalysis is a technique used for the purification and decolorization of water. In this work, the photocatalytic decolorization of aqueous solutions of Gentian Violet has been investigated. The ... [more ▼]

Photocatalysis is a technique used for the purification and decolorization of water. In this work, the photocatalytic decolorization of aqueous solutions of Gentian Violet has been investigated. The photocatalysts used for the study are tin dioxide (SnO2) and zinc oxide (ZnO) doped with sodium and prepared by sol-gel process. Photocatalysts were synthesised by sol-gel process and characterized by several techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Brunauer, Emmett and Teller (BET) method and UV-vis Spectroscopy. The results of photocatalytic activity of gentian violet degradation under ultraviolet irradiation, indicated that the synthesised photocatalyst exhibit good photocatalytic performance. [less ▲]

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See detailInfluences of the aqueous synthesis way and organosilane nature on the physico-chemical properties of porous alumina
Claude, Vincent ULg; Vilaseca, Miriam; Tatton, Andrew ULg et al

in European Journal of Inorganic Chemistry (2016), 2016(11), 1678-1689

The aqueous sol-gel synthesis of γ-Al2O3 modified with different silicon precursors {trimethoxysilane, triethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylene diamine} has been investigated. Two ... [more ▼]

The aqueous sol-gel synthesis of γ-Al2O3 modified with different silicon precursors {trimethoxysilane, triethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylene diamine} has been investigated. Two parameters have been studied: the silicon addition step and the type of silicon alkoxide. A first observation was that adding a silicon alkoxide either before or just after the precipitation step influences both the crystallinity and structure, whereas adding the alkoxide after a long agitation time only slightly modifies the support properties. It was also highlighted that due to their higher reactivity, silicon precursors with methoxy groups interact more strongly with the bulk alumina than the silicon precursors with ethoxy groups. This difference of Si location in the alumina structure permitted not only their resistance toward phase transition to be increased at high temperature, but also to stabilize them more efficiently against sintering under normal and steam conditions. Among the different silicon alkoxides tested, samples prepared with N-[3-(trimethoxysilyl)propyl]ethylene diamine showed very unusual properties. The alumina supports modified with this precursor showed grain-shaped nanocrystallites, whereas all other samples were platelet-like. As a result, this sample presented a very narrow pore diameter distribution of around 5 nm and a remarkably high specific surface area (530 m2/g). [less ▲]

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See detailEfficient P- and Ag-doped titania for the photocatalytic degradation of waste water organic pollutants
Bodson, Céline ULg; Heinrichs, Benoît ULg; Tasseroul, Ludivine ULg et al

in Journal of Alloys & Compounds (2016), 682

In this work, physico-chemical properties and photocatalytic activity of three types of dried or dried and calcined TiO2 materials, synthesized by the cogelation method, were studied: (i) a pure TiO2 ... [more ▼]

In this work, physico-chemical properties and photocatalytic activity of three types of dried or dried and calcined TiO2 materials, synthesized by the cogelation method, were studied: (i) a pure TiO2 xerogel ; (ii) TiO2 xerogels doped with Ag ; (iii) TiO2 xerogels co-doped with Ag and P. The presence of silver nanoparticles was observed by transmission electron microscopy (TEM) and the oxidation state of silver after calcination was examined by temperature-programmed reduction (TPR) measurements. The physico-chemical properties of xerogels were characterized by X-ray diffraction (XRD), diffuse reflectance UV-Vis spectroscopy (DR UV-Vis) and from nitrogen adsorption-desorption isotherms. The photocatalytic activity of the samples was quantified for the p-nitrophenol degradation under visible light. [less ▲]

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See detailFe3+/Iron Oxide/SiO2 Xerogel Catalysts for p-nitrophenol Degradation by Photo-Fenton Effects: Influence of Thermal Treatment on Catalysts Texture
Mahy, Julien ULg; Tasseroul, Ludivine ULg; Herlitscke, Marcus et al

in Materials Today: Proceedings (2016), 3(2), 464-469

Three iron xerogel catalysts were synthesized by hydrolysis and condensation of tetraethoxysilane (TEOS) and 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS) which is able to form a chelate with iron ... [more ▼]

Three iron xerogel catalysts were synthesized by hydrolysis and condensation of tetraethoxysilane (TEOS) and 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS) which is able to form a chelate with iron ions. Four thermal treatments were applied to catalysts: drying, drying-autoclaving, calcination and calcination-autoclaving. Textural characterizations show that the specific surface area is increased by calcination while materials microporosity completely collapse when using autoclaving. Based on Mössbauer spectroscopy and magnetometry measurements, only Fe3+ species were observed in xerogel catalysts. The photo-Fenton effect of these catalysts was evaluated on the degradation of p-nitrophenol in aqueous media. In the presence of H2O2, results show that this effect reachs 99% of degradation after 24 h. Mössbauer and catalytic tests are presented in another paper. [less ▲]

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See detailDoped sol–gel films vs. powders TiO2: On the positive effect induced by the presence of a substrate
Léonard, Géraldine ULg; Malengreaux, Charline; Melotte, Quentin et al

in Journal of Environmental Chemical Engineering (2016), 4

SiO2 and Ag–SiO2 doped TiO2 films and powders have been produced using a controlled sol–gel process. The dopant has been introduced using an alkoxysilane-functionalized ligand, with or without complexed ... [more ▼]

SiO2 and Ag–SiO2 doped TiO2 films and powders have been produced using a controlled sol–gel process. The dopant has been introduced using an alkoxysilane-functionalized ligand, with or without complexed silver ions. The influence of dopants on physico-chemical properties of the catalysts is studied by XRD, TEM–EDX, DRUV–vis analyses in the case of powders, while GIXRD, XPS, profilometry, UV–vis absorption analyses have been used for thin films. The photocatalytic activity has been evaluated from the degradation of methylene blue under UV-A light in the presence of the different catalysts over a period of 24 h. The detailed comparison between powders and films highlights a surprising positive effect in the case of films due to the presence of the substrate. In the case of photocatalytic powders, the presence of SiO2 or Ag–SiO2 into the TiO2 matrix has a detrimental effect on the photocatalytic activity while the opposite tendency is observed in the case of films, with best activities obtained with Ag–SiO2 doping. Different factors, in particular crystallinity modification between powders and films, have been studied to explain these opposite behaviors. In the case of powders, crystallization is hindered by SiO2 and Ag particles incorporation into the TiO2 matrix, leading to a decrease of the photocatalytic activity. In the case of thin films, probably because of the presence of a substrate, crystallization is not influenced by the presence of SiO2 and Ag particles. Therefore, the latter ones can fully play their role of electron traps leading to an enhanced photocatalytic activity. [less ▲]

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