Open AccessFeature PaperReview
Visible-Light-Active TiO2-Based Hybrid Nanocatalysts for Environmental Applications
Catalysts 2017, 7(4), 100; doi:10.3390/catal7040100 (registering DOI) -
Abstract
Photocatalytic nanomaterials such as TiO2 are receiving a great deal of attention owing to their potential applications in environmental remediation. Nonetheless, the low efficiency of this class of materials in the visible range has, so far, hampered their large-scale application. The increasing
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Photocatalytic nanomaterials such as TiO2 are receiving a great deal of attention owing to their potential applications in environmental remediation. Nonetheless, the low efficiency of this class of materials in the visible range has, so far, hampered their large-scale application. The increasing demand for highly efficient, visible-light-active photocatalysts can be addressed by hybrid nanostructured materials in which two or more units, each characterised by peculiar physical properties, surface chemistry and morphology, are combined together into a single nano-object with unprecedented chemical–physical properties. The present review intends to focus on hybrid nanomaterials, based on TiO2 nanoparticles able to perform visible-light-driven photocatalytic processes for environmental applications. We give a brief overview of the synthetic approaches recently proposed in the literature to synthesise hybrid nanocrystals and discuss the potential applications of such nanostructures in water remediation, abatement of atmospheric pollutants (including NOx and volatile organic compounds (VOCs)) and their use in self-cleaning surfaces. Full article
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Open AccessArticle
Fivefold Enhanced Photoelectrochemical Properties of ZnO Nanowire Arrays Modified with C3N4 Quantum Dots
Catalysts 2017, 7(4), 99; doi:10.3390/catal7040099 -
Abstract
A facile and effective growing strategy of graphite-like carbon nitride quantum dots (CNQDs) modified on ZnO nanowire array composite electrodes has been successfully designed and prepared for the first time. The remarkable quantum enhanced properties were carefully studied by means of scanning electron
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A facile and effective growing strategy of graphite-like carbon nitride quantum dots (CNQDs) modified on ZnO nanowire array composite electrodes has been successfully designed and prepared for the first time. The remarkable quantum enhanced properties were carefully studied by means of scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscope (XPS), UV-vis diffuse reflectance, PEC performance, and photocatalytic hydrogen production, and the results were in good agreement. Fivefold enhanced photoelectrochemical performances of this novel hierarchical hetero-array prepared in this paper compared with pure ZnO nanowire arrays were obtained under UV-light. The effect was attributed to the remarkable charge separation between CNQDs and ZnO nanowire arrays. Additional investigations revealed that the particular structure of CNQDs/ZnO composites contributed to the separation of a photon-generation carrier and an enhanced photoelectric current. Moreover, the absorption edge of CNQD-modified ZnO nanowire arrays was slightly broadened, and the diameter was reduced as well. The photoelectrochemistry hydrogen evolution splitting water using simulated solar irradiation exhibited the foreground of a possible application of a mechanism of photoelectrochemistry hydrogen evolution over CNQDs/ZnO composite electrodes. Full article
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Open AccessArticle
Three-Dimensional TiO2 Structures Incorporated with Tungsten Oxide for Treatment of Toxic Aromatic Volatile Compounds
Catalysts 2017, 7(4), 97; doi:10.3390/catal7040097 -
Abstract
This study assessed 3D WO3–TiO2 nanoflowers (WTNF) synthesized by a combined hydrothermal–ultrasonication–impregnation method for their applicability to the treatment of aromatic volatile compounds under visible-light illumination. The scanning electron microscopy exhibited the formation of 3D structures in the prepared WTNF
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This study assessed 3D WO3–TiO2 nanoflowers (WTNF) synthesized by a combined hydrothermal–ultrasonication–impregnation method for their applicability to the treatment of aromatic volatile compounds under visible-light illumination. The scanning electron microscopy exhibited the formation of 3D structures in the prepared WTNF samples. The X-ray diffraction patterns and energy dispersive X-ray results indicated a successful incorporation of WO3 into TNF structures. The UV-visible spectroscopy showed that the prepared WTNF samples can be functioned under visible light irradiation. The output-to-input concentration ratios of toluene and o-xylene with WTNF samples were lower than those of TiO2 nanoflowers. These findings were illustrated on the basis of charge separation ability, adsorption capability, and light absorption of the sample photocatalysts. The input-to-output concentration ratios of the target chemicals were lowest for 10 M NaOH and highest for 5 M NaOH. The photocatalytic degradation efficiencies of WTNF sample photocatalysts increased with increasing WO3 content from 0.1% to 1.0%, and dropped gradually with increasing WO3 content further to 4.0%. Light-emitting-diodes (LEDs) are a more highly energy-efficient light source compared to a conventional lamp for the photocatalytic degradation of toluene and o-xylene, although the photocatalytic activity is higher for the conventional lamp. Full article
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Open AccessArticle
Total Oxidation of Propane Using CeO2 and CuO-CeO2 Catalysts Prepared Using Templates of Different Nature
Catalysts 2017, 7(4), 96; doi:10.3390/catal7040096 -
Abstract
Several CeO2 and CuO-CeO2 catalysts were prepared using different methods, i.e., a homogeneous precipitation with urea, a nanocasting route using CMK-3 carbon as a hard template and a sol–gel process using Poly(methyl methacrylate) (PMMA) polymer as a soft template, and tested
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Several CeO2 and CuO-CeO2 catalysts were prepared using different methods, i.e., a homogeneous precipitation with urea, a nanocasting route using CMK-3 carbon as a hard template and a sol–gel process using Poly(methyl methacrylate) (PMMA) polymer as a soft template, and tested in the total oxidation of propane. The catalysts were characterized by a number of physicochemical techniques (XRD, N2 adsorption, TPR, XPS, Raman spectroscopy) showing distinct characteristics. For each series, Cu-Ce-O catalysts with low Cu-loadings (5 wt % CuO) showed the highest activity, higher than those samples either without copper or with high Cu-loading (13 wt % CuO). The incorporation of copper leads to an increase of the concentration of bulk defects but if the Cu-loading is too high the surface area drastically falls. The highest activity in the total oxidation of propane was achieved by Cu-containing ceria catalysts synthesized using a polymer as a template, as this method yields high surface area materials. The surface area and the number of bulk/sub-surface defects of the ceria seem to be the main properties determining the catalytic activity. Full article
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Open AccessReview
Eco-Friendly Physical Activation Methods for Suzuki–Miyaura Reactions
Catalysts 2017, 7(4), 98; doi:10.3390/catal7040098 -
Abstract
Eco-compatible activation methods in Suzuki–Miyaura cross-coupling reactions offer challenging opportunities for the design of clean and efficient synthetic processes. The main enabling technologies described in the literature are microwaves, ultrasound, grinding (mechanochemistry) and light. These methods can be performed in water or other
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Eco-compatible activation methods in Suzuki–Miyaura cross-coupling reactions offer challenging opportunities for the design of clean and efficient synthetic processes. The main enabling technologies described in the literature are microwaves, ultrasound, grinding (mechanochemistry) and light. These methods can be performed in water or other green solvents with phase-transfer catalysis or even in solventless conditions. In this review, the authors will summarize the progress in this field mainly from 2010 up to the present day. Full article
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Open AccessArticle
Graphene Oxide-Supported Oxime Palladacycles as Efficient Catalysts for the Suzuki–Miyaura Cross-Coupling Reaction of Aryl Bromides at Room Temperature under Aqueous Conditions
Catalysts 2017, 7(3), 94; doi:10.3390/catal7030094 -
Abstract
Palladacycles are highly efficient precatalysts in cross-coupling reactions whose immobilization on carbonaceous materials has been hardly studied. Herein, we report a detailed study on the synthesis and characterization of new oxime palladacycle-graphene oxide non-covalent materials along with their catalytic activity in the Suzuki–Miyaura
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Palladacycles are highly efficient precatalysts in cross-coupling reactions whose immobilization on carbonaceous materials has been hardly studied. Herein, we report a detailed study on the synthesis and characterization of new oxime palladacycle-graphene oxide non-covalent materials along with their catalytic activity in the Suzuki–Miyaura reaction. Catalyst 1-GO, which has been fully characterized by ICP, XPS, TGA, and UV-Vis analyses has been demonstrated to be an efficient catalyst for the Suzuki–Miyaura coupling between aryl bromides and arylboronic acids using very low catalyst loadings (0.002 mol % of Pd) at room temperature under aqueous conditions. Full article
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Open AccessArticle
Highly Selective Solid Acid Catalyst H1−xTi2(PO4)3−x(SO4)x for Non-Oxidative Dehydrogenation of Methanol and Ethanol
Catalysts 2017, 7(3), 95; doi:10.3390/catal7030095 -
Abstract
The conversion of alcohols towards aldehydes in the presence of catalysts by non-oxidative dehydrogenation requires special importance from the perspective of green chemistry. Sodium (Na) super ionic conductor (NASICON)-type hydrogen titanium phosphate sulfate (HTPS; H1−xTi2(PO4)3−
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The conversion of alcohols towards aldehydes in the presence of catalysts by non-oxidative dehydrogenation requires special importance from the perspective of green chemistry. Sodium (Na) super ionic conductor (NASICON)-type hydrogen titanium phosphate sulfate (HTPS; H1−xTi2(PO4)3−x(SO4)x, x = 0.5–1) catalysts were synthesized by the sol-gel method, characterized by N2 gas sorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), NH3 temperature-programmed desorption (NH3-TPD), ultraviolet–visible (UV-VIS) spectroscopy, and their catalytic properties were studied for the non-oxidative dehydrogenation of methanol and ethanol. The ethanol is more reactive than methanol, with the conversion for ethanol exceeding 95% as compared to methanol, where the conversion has a maximum value at 55%. The selectivity to formaldehyde is almost 100% in methanol conversion, while the selectivity to acetaldehyde decreases from 56% to 43% in ethanol conversion, when the reaction temperature is increased from 250 to 400 °C. Full article
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Open AccessArticle
Stabilization of a Lipolytic Enzyme for Commercial Application
Catalysts 2017, 7(3), 91; doi:10.3390/catal7030091 -
Abstract
Thermomyceslanouginosalipase has been used to develop improved methods for carrier-free immobilization, the Cross-Linked Enzyme Aggregates (CLEAs), for its application in detergent products. An activator step has been introduced to the CLEAs preparation process with the addition of Tween 80 as activator
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Thermomyceslanouginosalipase has been used to develop improved methods for carrier-free immobilization, the Cross-Linked Enzyme Aggregates (CLEAs), for its application in detergent products. An activator step has been introduced to the CLEAs preparation process with the addition of Tween 80 as activator molecule, in order to obtain a higher number of the individual lipase molecules in the ”open lid” conformation prior to the cross-linking step. A terminator step has been introduced to quench the cross-linking reaction at an optimal time by treatment with an amine buffer in order to obtain smaller and more homogenous cross-linked particles. This improved immobilization method has been compared to a commercially available enzyme and has been shown to be made up of smaller and more homogenous particles with an average diameter of 1.85 ± 0.28 µm which are 129.7% more active than the free enzyme. The CLEAs produced show improved features for commercial applications such as an improved wash performance comparable with the free enzyme, improved stability to proteolysis and a higher activity after long-term storage. Full article
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Open AccessArticle
Catalytic Transfer Hydrogenation of Biobased HMF to 2,5-Bis-(Hydroxymethyl)Furan over Ru/Co3O4
Catalysts 2017, 7(3), 92; doi:10.3390/catal7030092 -
Abstract
2,5-Bis-(hydroxymethyl)furan (BHMF) is an important biomass-based platform chemical that can be derived from the hydrogenation of biomass-based 5-hydroxymethylfurfural (HMF). In this paper, the formation of BHMF from HMF via the catalytic transfer hydrogenation (CTH) process, using isopropanol as the hydrogen source and Ru/Co
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2,5-Bis-(hydroxymethyl)furan (BHMF) is an important biomass-based platform chemical that can be derived from the hydrogenation of biomass-based 5-hydroxymethylfurfural (HMF). In this paper, the formation of BHMF from HMF via the catalytic transfer hydrogenation (CTH) process, using isopropanol as the hydrogen source and Ru/Co3O4 as the catalyst, was studied. The results revealed that the Ru/Co3O4 catalyst displayed a high catalytic efficiency, and that a BHMF yield of up to 82% was obtained at 190 °C in 6 h. Moreover, it was found that the recovered Ru/Co3O4 exhibited a similar catalytic activity to the pristine Ru/Co3O4 catalyst. These results supported the conclusion that the present CTH process is an attractive green route for the synthesis of BHMF from biomass-based HMF. Full article
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Open AccessReview
Photocatalytic Water Oxidation on ZnO: A Review
Catalysts 2017, 7(3), 93; doi:10.3390/catal7030093 -
Abstract
The investigation of the water oxidation mechanism on photocatalytic semiconductor surfaces has gained much attention for its potential to unlock the technological limitations of producing H2 from carbon-free sources, i.e., H2O. This review seeks to highlight the available scientific and
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The investigation of the water oxidation mechanism on photocatalytic semiconductor surfaces has gained much attention for its potential to unlock the technological limitations of producing H2 from carbon-free sources, i.e., H2O. This review seeks to highlight the available scientific and fundamental understanding towards the water oxidation mechanism on ZnO surfaces, as well as present a summary on the modification strategies carried out to increase the photocatalytic response of ZnO. Full article
Open AccessArticle
Organocatalytic Enantioselective Epoxidation of Some Aryl-Substituted Vinylidenebisphosphonate Esters: On the Way to Chiral Anti-Osteoporosis Drugs
Catalysts 2017, 7(3), 90; doi:10.3390/catal7030090 -
Abstract
The synthesis of a new class of epoxide derivatives from prochiral vinylidene bisphosphonate (VBP) precursors is reported using hydrogen peroxide as the terminal oxidant. The reaction is carried out using a series of possible organic activators having a basic character, with the best
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The synthesis of a new class of epoxide derivatives from prochiral vinylidene bisphosphonate (VBP) precursors is reported using hydrogen peroxide as the terminal oxidant. The reaction is carried out using a series of possible organic activators having a basic character, with the best results being observed using quinine and sparteine. These activators not only provide from good to excellent epoxide yields with a large variety of VBPs, but also interesting enantioselectivities in the 67%–96% ee range, at least in the case of the Ph and m-MeO–Ph VBP derivatives, opening the way to a number of chiral anti-osteoporosis potentially active pharmaceutical ingredients. Full article
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Open AccessReview
Pd/C Catalysis under Microwave Dielectric Heating
Catalysts 2017, 7(3), 89; doi:10.3390/catal7030089 -
Abstract
Microwave-assisted organic synthesis (MAOS) provides a novel and efficient means of achieving heat organic reactions. Nevertheless, the potential arcing phenomena via microwave (MW) interaction with solid metal catalysts has limited its use by organic chemists. As arcing phenomena are now better understood, new
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Microwave-assisted organic synthesis (MAOS) provides a novel and efficient means of achieving heat organic reactions. Nevertheless, the potential arcing phenomena via microwave (MW) interaction with solid metal catalysts has limited its use by organic chemists. As arcing phenomena are now better understood, new applications of Pd/C-catalyzed reactions under MW dielectric heating are now possible. In this review, the state of the art, benefits, and challenges of coupling MW heating with heterogeneous Pd/C catalysis are discussed to inform organic chemists about their use with one of the most popular heterogeneous catalysts. Full article
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Open AccessArticle
The Role of Ruthenium in CO2 Capture and Catalytic Conversion to Fuel by Dual Function Materials (DFM)
Catalysts 2017, 7(3), 88; doi:10.3390/catal7030088 -
Abstract
Development of sustainable energy technologies and reduction of carbon dioxide in the atmosphere are the two effective strategies in dealing with current environmental issues. Herein we report a Dual Function Material (DFM) consisting of supported sodium carbonate in intimate contact with dispersed Ru
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Development of sustainable energy technologies and reduction of carbon dioxide in the atmosphere are the two effective strategies in dealing with current environmental issues. Herein we report a Dual Function Material (DFM) consisting of supported sodium carbonate in intimate contact with dispersed Ru as a promising catalytic solution for combining both approaches. The Ru-Na2CO3 DFM deposited on Al2O3 captures CO2 from a flue gas and catalytically converts it to synthetic natural gas (i.e., methane) using H2 generated from renewable sources. The Ru in the DFM, in combination with H2, catalytically hydrogenates both adsorbed CO2 and the bulk Na2CO3, forming methane. The depleted sites adsorb CO2 through a carbonate reformation process and in addition adsorb CO2 on its surface. This material functions well in O2- and H2O-containing flue gas where the favorable Ru redox property allows RuOx, formed during flue gas exposure, to be reduced during the hydrogenation cycle. As a combined CO2 capture and utilization scheme, this technology overcomes many of the limitations of the conventional liquid amine-based CO2 sorbent technology. Full article
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Open AccessLetter
Olefin Metathesis with Ru-Based Catalysts Exchanging the Typical N-Heterocyclic Carbenes by a Phosphine–Phosphonium Ylide
Catalysts 2017, 7(3), 85; doi:10.3390/catal7030085 -
Abstract
Density functional theory (DFT) calculations have been used to describe the first turnover of an olefin metathesis reaction calling for a new in silico family of homogenous Ru-based catalysts bearing a phosphine–phosphonium ylide ligand, with ethylene as a substrate. Equal to conventional Ru-based
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Density functional theory (DFT) calculations have been used to describe the first turnover of an olefin metathesis reaction calling for a new in silico family of homogenous Ru-based catalysts bearing a phosphine–phosphonium ylide ligand, with ethylene as a substrate. Equal to conventional Ru-based catalysts bearing an N-heterocyclic carbene (NHC) ligand, the activation of these congeners occurs through a dissociative mechanism, with a more exothermic first phosphine dissociation step. In spite of a stronger electron-donating ability of a phosphonium ylide C-ligand with respect to a diaminocarbene analogue, upper energy barriers were calculated to be on average ca. 5 kcal/mol higher than those of Ru–NHC standards. Overall, the study also highlights advantages of bidentate ligands over classical monodentate NHC and phosphine ligands, with a particular preference for the cis attack of the olefin. The new generation of catalysts is constituted by cationic complexes potentially soluble in water, to be compared with the typical neutral Ru–NHC ones. Full article
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Open AccessArticle
Dendrimer-Stabilized Ru Nanoparticles Immobilized in Organo-Silica Materials for Hydrogenation of Phenols
Catalysts 2017, 7(3), 86; doi:10.3390/catal7030086 -
Abstract
New hybrid catalysts based on Ru nanoparticles, encapsulated into poly(propylene imine dendrimers), immobilized into silica pores, were synthesized and examined for the hydrogenation of alkyl-substituted phenols. The corresponding alkyl-substituted cyclohexanols were presented as the major reaction products, while incomplete hydrogenation products appeared to
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New hybrid catalysts based on Ru nanoparticles, encapsulated into poly(propylene imine dendrimers), immobilized into silica pores, were synthesized and examined for the hydrogenation of alkyl-substituted phenols. The corresponding alkyl-substituted cyclohexanols were presented as the major reaction products, while incomplete hydrogenation products appeared to be minor. A competition between the sterical factors of dendrimer-containing carriers and the electronic factors of substrate substituents influenced the hydrogenation rate of the alkyl-substituted phenols. The carrier structure was found to have a significant influence on both the physical and chemical properties of the catalysts and their hydrogenation activity. The synthesized hybrid catalysts appeared to be stable after recycling and could be re-used several times without significant loss of activity. Full article
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Open AccessReview
Recent Advancements in Stereoselective Olefin Metathesis Using Ruthenium Catalysts
Catalysts 2017, 7(3), 87; doi:10.3390/catal7030087 -
Abstract
Olefin metathesis is a prevailing method for the construction of organic molecules. Recent advancements in olefin metathesis have focused on stereoselective transformations. Ruthenium olefin metathesis catalysts have had a particularly pronounced impact in the area of stereoselective olefin metathesis. The development of three
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Olefin metathesis is a prevailing method for the construction of organic molecules. Recent advancements in olefin metathesis have focused on stereoselective transformations. Ruthenium olefin metathesis catalysts have had a particularly pronounced impact in the area of stereoselective olefin metathesis. The development of three categories of Z-selective olefin metathesis catalysts has made Z-olefins easily accessible to both laboratory and industrial chemists. Further design enhancements to asymmetric olefin metathesis catalysts have streamlined the construction of complex molecules. The understanding gained in these areas has extended to the employment of ruthenium catalysts to stereoretentive olefin metathesis, the first example of a kinetically E-selective process. These advancements, as well as synthetic applications of the newly developed catalysts, are discussed. Full article
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Open AccessArticle
Solvent-Free Biginelli Reactions Catalyzed by Hierarchical Zeolite Utilizing a Ball Mill Technique: A Green Sustainable Process
Catalysts 2017, 7(3), 84; doi:10.3390/catal7030084 -
Abstract
A sustainable, green one-pot process for the synthesis of dihydropyrimidinones (DHPMs) derivatives by a three-component reaction of β-ketoester derivatives, aldehyde and urea or thiourea over the alkali-treated H-ZSM-5 zeolite under ball-milling was developed. Isolation of the product with ethyl acetate shadowed by vanishing
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A sustainable, green one-pot process for the synthesis of dihydropyrimidinones (DHPMs) derivatives by a three-component reaction of β-ketoester derivatives, aldehyde and urea or thiourea over the alkali-treated H-ZSM-5 zeolite under ball-milling was developed. Isolation of the product with ethyl acetate shadowed by vanishing of solvent was applied. The hierachical zeolite catalyst (MFI27_6) showed high yield (86%–96%) of DHPMs in a very short time (10–30 min). The recyclability of the catalyst for the subsequent reactions was examined in four subsequent runs. The catalyst was shown to be robust without a detectable reduction in catalytic activity, and high yields of products showed the efficient protocol of the Biginelli reactions. Full article
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Open AccessFeature PaperReview
Review of Heterogeneous Catalysts for Catalytically Upgrading Vegetable Oils into Hydrocarbon Biofuels
Catalysts 2017, 7(3), 83; doi:10.3390/catal7030083 -
Abstract
To address the issues of greenhouse gas emissions associated with fossil fuels, vegetable oilseeds, especially non-food oilseeds, are used as an alternative fuel resource. Vegetable oil derived from these oilseeds can be upgraded into hydrocarbon biofuel. Catalytic cracking and hydroprocessing are two of
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To address the issues of greenhouse gas emissions associated with fossil fuels, vegetable oilseeds, especially non-food oilseeds, are used as an alternative fuel resource. Vegetable oil derived from these oilseeds can be upgraded into hydrocarbon biofuel. Catalytic cracking and hydroprocessing are two of the most promising pathways for converting vegetable oil to hydrocarbon biofuel. Heterogeneous catalysts play a critical role in those processes. The present review summarizes current progresses and remaining challenges of vegetable oil upgrading to biofuel. The catalyst properties, applications, deactivation, and regeneration are reviewed. A comparison of catalysts used in vegetable oil and bio-oil upgrading is also carried out. Some suggestions for heterogeneous catalysts applied in vegetable oil upgrading to improve the yield and quality of hydrocarbon biofuel are provided for further research in the future. Full article
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Open AccessArticle
Synthesis of Renewable Diesel Range Alkanes by Hydrodeoxygenation of Palmitic Acid over 5% Ni/CNTs under Mild Conditions
Catalysts 2017, 7(3), 81; doi:10.3390/catal7030081 -
Abstract
Recently, the catalytic upgrading of bio-oil to renewable diesel has been attracting more and more attention. In the current paper, carbon nanotube (CNT)-supported nickel catalysts, namely, 5% Ni/CNTs, were prepared for liquid hydrocarbon production through the deoxygenation of palmitic acid, the model compound
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Recently, the catalytic upgrading of bio-oil to renewable diesel has been attracting more and more attention. In the current paper, carbon nanotube (CNT)-supported nickel catalysts, namely, 5% Ni/CNTs, were prepared for liquid hydrocarbon production through the deoxygenation of palmitic acid, the model compound of bio-oil under a mild condition of 240 °C reaction temperature and 2 MPa H2 pressure. The experimental results revealed that the main reaction product was pentadecane (yield of 89.64%) at an optimum palmitic acid conversion of 97.25% via the hydrodecarbonylation (HDC) process. The deoxygenation mechanism for palmitic acid conversion was also investigated. This study provides technical parameters and a theoretical basis for further industrialization in the bio-oil upgrading process. Full article
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Open AccessArticle
Biotemplated Mesoporous TiO2/SiO2 Composite Derived from Aquatic Plant Leaves for Efficient Dye Degradation
Catalysts 2017, 7(3), 82; doi:10.3390/catal7030082 -
Abstract
The biotemplating technique is an environmental-protective high-efficiency new technology by which the resulting TiO2 may simultaneously attain the duplication of structure and self-doping elements from biotemplate materials, which is highly desirable for photocatalytic applications. In this paper, aquatic plant leaves—including reed, water hyacinth,
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The biotemplating technique is an environmental-protective high-efficiency new technology by which the resulting TiO2 may simultaneously attain the duplication of structure and self-doping elements from biotemplate materials, which is highly desirable for photocatalytic applications. In this paper, aquatic plant leaves—including reed, water hyacinth, and duckweed—were used as both templates and silicon precursors to successfully synthesize biomorphic TiO2/SiO2 composite with mesoporous structures. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption–desorption, and UV–visible diffuse reflectance spectra were applied to characterize the microstructures of the samples. The results show that all TiO2/SiO2 composites are mainly composed of an anatase phase with mesoporous structure and possess high specific surface area. Compared with commercial Degussa P25 TiO2, all TiO2/SiO2 samples display intensive light-harvesting efficiency, particularly in the visible light range. The activities were evaluated by using gentian violet as a target for photocatalytic degradation experiments under simulated solar irradiation. The TiO2/SiO2 samples templated by reed and water hyacinth leaves exhibit high activity, while the TiO2/SiO2 samples obtained from duckweed are inferior to P25 in the degradation of gentian violet. A synergistic effect of SiO2 incorporation and structural construction through biotemplating is proposed to be beneficial to photocatalytic activity. Full article
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