Showing papers in "Catalysts in 2019"
TL;DR: In this article, a comprehensive review discusses the pseudo kinetics and mechanisms of the photodegradation reactions, as well as the operational factors that govern the adsorption of dye molecules, including the initial dye concentration, pH of the solution, temperature of the reaction medium, and light intensity.
Abstract: Due to its low cost, environmentally friendly process, and lack of secondary contamination, the photodegradation of dyes is regarded as a promising technology for industrial wastewater treatment. This technology demonstrates the light-enhanced generation of charge carriers and reactive radicals that non-selectively degrade various organic dyes into water, CO2, and other organic compounds via direct photodegradation or a sensitization-mediated degradation process. The overall efficiency of the photocatalysis system is closely dependent upon operational parameters that govern the adsorption and photodegradation of dye molecules, including the initial dye concentration, pH of the solution, temperature of the reaction medium, and light intensity. Additionally, the charge-carrier properties of the photocatalyst strongly affect the generation of reactive species in the heterogeneous photodegradation and thereby dictate the photodegradation efficiency. Herein, this comprehensive review discusses the pseudo kinetics and mechanisms of the photodegradation reactions. The operational factors affecting the photodegradation of either cationic or anionic dye molecules, as well as the charge-carrier properties of the photocatalyst, are also fully explored. By further analyzing past works to clarify key active species for photodegradation reactions and optimal conditions, this review provides helpful guidelines that can be applied to foster the development of efficient photodegradation systems.
464 citations
TL;DR: In this article, a broad range of research efforts have been devoted to enhancing the optical and electrical properties of TiO2, resulting in improved photocatalytic activity, including the introduction of intrinsic defects and foreign species into the TiO 2 lattice, morphology and crystal facet control, and the development of unique mesocrystal structures.
Abstract: Titanium dioxide (TiO2) nanomaterials have garnered extensive scientific interest since 1972 and have been widely used in many areas, such as sustainable energy generation and the removal of environmental pollutants. Although TiO2 possesses the desired performance in utilizing ultraviolet light, its overall solar activity is still very limited because of a wide bandgap (3.0–3.2 eV) that cannot make use of visible light or light of longer wavelength. This phenomenon is a deficiency for TiO2 with respect to its potential application in visible light photocatalysis and photoelectrochemical devices, as well as photovoltaics and sensors. The high overpotential, sluggish migration, and rapid recombination of photogenerated electron/hole pairs are crucial factors that restrict further application of TiO2. Recently, a broad range of research efforts has been devoted to enhancing the optical and electrical properties of TiO2, resulting in improved photocatalytic activity. This review mainly outlines state-of-the-art modification strategies in optimizing the photocatalytic performance of TiO2, including the introduction of intrinsic defects and foreign species into the TiO2 lattice, morphology and crystal facet control, and the development of unique mesocrystal structures. The band structures, electronic properties, and chemical features of the modified TiO2 nanomaterials are clarified in detail along with details regarding their photocatalytic performance and various applications.
249 citations
TL;DR: In this paper, hierarchical Au/TiO2 nanostructures were studied as possible photoanodes for water splitting and bisphenol A (BPA) oxidation.
Abstract: In this work, hierarchical Au/TiO2 nanostructures were studied as possible photoanodes for water splitting and bisphenol A (BPA) oxidation. TiO2 samples were synthetized by Pulsed Laser Deposition (PLD), while Au nanoparticles (NPs) were differently dispersed (i.e., NPs at the bottom or at the top of the TiO2, as well as integrated TiO2/Au-NPs assemblies). Voltammetric scans and electrochemical impedance spectroscopy analysis were used to correlate the morphology of samples with their electrochemical properties; the working mechanism was investigated in the dark and in the presence of a light radiation, under neutral pH conditions towards the possible oxidation of both bisphenol A (BPA) and water molecules. Different behavior of the samples was observed, which may be attributed mainly to the distributions of Au NPs and to their dimension as well. In particular, the presence of NPs at the bottom seems to be the crucial point for the working mechanism of the structure, thanks to scattering effects that likely allow to better exploit the radiation.
207 citations
TL;DR: In this article, the authors evaluated the performance of three promising photocatalysts (titania (TiO2-P25), graphitic carbon nitride (g-C3N4), and cadmium sulfide (CdS)) using various sacrificial agents.
Abstract: Photocatalytic water splitting is a sustainable technology for the production of clean fuel in terms of hydrogen (H2). In the present study, hydrogen (H2) production efficiency of three promising photocatalysts (titania (TiO2-P25), graphitic carbon nitride (g-C3N4), and cadmium sulfide (CdS)) was evaluated in detail using various sacrificial agents. The effect of most commonly used sacrificial agents in the recent years, such as methanol, ethanol, isopropanol, ethylene glycol, glycerol, lactic acid, glucose, sodium sulfide, sodium sulfite, sodium sulfide/sodium sulfite mixture, and triethanolamine, were evaluated on TiO2-P25, g-C3N4, and CdS. H2 production experiments were carried out under simulated solar light irradiation in an immersion type photo-reactor. All the experiments were performed without any noble metal co-catalyst. Moreover, photolysis experiments were executed to study the H2 generation in the absence of a catalyst. The results were discussed specifically in terms of chemical reactions, pH of the reaction medium, hydroxyl groups, alpha hydrogen, and carbon chain length of sacrificial agents. The results revealed that glucose and glycerol are the most suitable sacrificial agents for an oxide photocatalyst. Triethanolamine is the ideal sacrificial agent for carbon and sulfide photocatalyst. A remarkable amount of H2 was produced from the photolysis of sodium sulfide and sodium sulfide/sodium sulfite mixture without any photocatalyst. The findings of this study would be highly beneficial for the selection of sacrificial agents for a particular photocatalyst.
185 citations
TL;DR: In this paper, a review analyzes the preparation and characterization of metal organic frameworks (MOFs) and their application as photocatalysts for water purification, highlighting the problem of water scarcity and the different solutions for purification including photocatalysis with semiconductors such as MOFs.
Abstract: This review analyzes the preparation and characterization of metal organic frameworks (MOFs) and their application as photocatalysts for water purification. The study begins by highlighting the problem of water scarcity and the different solutions for purification, including photocatalysis with semiconductors, such as MOFs. It also describes the different methodologies that can be used for the synthesis of MOFs, paying attention to the purification and activation steps. The characterization of MOFs and the different approaches that can be followed to learn the photocatalytic processes are also detailed. Finally, the work reviews literature focused on the degradation of contaminants from water using MOF-based photocatalysts under light irradiation.
185 citations
TL;DR: In this paper, the authors reviewed the recent research progress on supported transition and mixed transition metal oxide catalysts for the LT-SCR reaction and discussed the influence of operating conditions and promoters on the performance.
Abstract: The importance of the low-temperature selective catalytic reduction (LT-SCR) of NOx by NH3 is increasing due to the recent severe pollution regulations being imposed around the world. Supported and mixed transition metal oxides have been widely investigated for LT-SCR technology. However, these catalytic materials have some drawbacks, especially in terms of catalyst poisoning by H2O or/and SO2. Hence, the development of catalysts for the LT-SCR process is still under active investigation throughout seeking better performance. Extensive research efforts have been made to develop new advanced materials for this technology. This article critically reviews the recent research progress on supported transition and mixed transition metal oxide catalysts for the LT-SCR reaction. The review covered the description of the influence of operating conditions and promoters on the LT-SCR performance. The reaction mechanism, reaction intermediates, and active sites are also discussed in detail using isotopic labelling and in situ FT-IR studies.
182 citations
TL;DR: In this paper, the recent progress in the development of novel photocatalysts for wastewater treatment via various methods in the sight of composite techniques are systematically discussed, and a brief summary of the current challenges and an outlook for the developing of composite photocatalyst in the area of wastewater treatment are provided.
Abstract: Serious water pollution and the exhausting of fossil resources have become worldwide urgent issues yet to be solved. Solar energy driving photocatalysis processes based on semiconductor catalysts is considered to be the most promising technique for the remediation of wastewater. However, the relatively low photocatalytic efficiency remains a critical limitation for the practical use of the photocatalysts. To solve this problem, numerous strategies have been developed for the preparation of advanced photocatalysts. Particularly, incorporating a semiconductor with various functional components from atoms to individual semiconductors or metals to form a composite catalyst have become a facile approach for the design of high-efficiency catalysts. Herein, the recent progress in the development of novel photocatalysts for wastewater treatment via various methods in the sight of composite techniques are systematically discussed. Moreover, a brief summary of the current challenges and an outlook for the development of composite photocatalysts in the area of wastewater treatment are provided.
172 citations
TL;DR: In this paper, a comparative analysis of various existing catalytic oxidation techniques: acetic acid/formic acid catalytic oxide, heteropolyacid (HPA) catalytic oxidization, ionic liquid catalytic dioxide, molecular sieve catalytic, polyoxometalates catalytic and titanium catalytic systems is presented, as well as discusses research gaps and proposes important recommendations for future challenges.
Abstract: The production of green fuel oil is of the utmost importance for maintaining a healthy life and environment in the current world. Effective and complete removal of sulfur refractory compounds (such as 4,6-dimethyldibenzothiophene and other alkyl-substituted thiophene derivatives) from fuel oil is essential to meet the new requirements of sulfur standards. Several techniques have been proposed for desulfurization of fuel oil, such as hydrodesulfurization (HDS), selective adsorption, extractive distillation, biodesulfurization, and oxidative desulfurization (ODS). The removal of sulfur by the HDS process requires higher investment costs, high reaction temperature (up to 400 °C), and high pressure (up to 100 atm) reactors. On the other hand, studies have shown that the ODS process is remarkably successful in the removal of sulfur under mild reaction conditions. This review article presents a comparative analysis of various existing catalytic oxidation techniques: acetic acid/formic acid catalytic oxidation, heteropolyacid (HPA) catalytic oxidation, ionic liquid catalytic oxidation, molecular sieve catalytic oxidation, polyoxometalates catalytic oxidation, titanium catalytic oxidation, and ultrasound-assisted oxidation systems, as well as discusses research gaps, and proposes important recommendations for future challenges.
138 citations
TL;DR: In this article, the authors provide a timely overview of the very important advances that have recently taken place in the acylative Suzuki cross-coupling of an organoboron reagent with an acyl electrophile (acyl halide, anhydride, ester, amide).
Abstract: Acyl Suzuki cross-coupling involves the coupling of an organoboron reagent with an acyl electrophile (acyl halide, anhydride, ester, amide). This review provides a timely overview of the very important advances that have recently taken place in the acylative Suzuki cross-coupling. Particular emphasis is directed toward the type of acyl electrophiles, catalyst systems and new cross-coupling partners. This review will be of value to synthetic chemists involved in this rapidly developing field of Suzuki cross-coupling as well as those interested in using acylative Suzuki cross-coupling for the synthesis of ketones as a catalytic alternative to stoichiometric nucleophilic additions or Friedel-Crafts reactions.
126 citations
TL;DR: In this article, a review of recent advances in the catalytic hydrogenation of furfural towards (tetrahydro)furfuryl alcohol and 2-methyl(tetrahedron)furan in terms of different non-noble metal and noble metal catalytic systems is presented.
Abstract: Furfural has been considered as one of the most promising platform molecules directly derived from biomass. The hydrogenation of furfural is one of the most versatile reactions to upgrade furanic components to biofuels. For instance, it can lead to plenty of downstream products, such as (tetrahydro)furfuryl alcohol, 2-methyl(tetrahydro)furan, lactones, levulinates, cyclopentanone(l), or diols, etc. The aim of this review is to discuss recent advances in the catalytic hydrogenation of furfural towards (tetrahydro)furfuryl alcohol and 2-methyl(tetrahydro)furan in terms of different non-noble metal and noble metal catalytic systems. Reaction mechanisms that are related to the different catalytic materials and reaction conditions are properly discussed. Selective hydrogenation of furfural could be modified not only by varying the types of catalyst (nature of metal, support, and preparation method) and reaction conditions, but also by altering the reaction regime, namely from batch to continuous flow. In any case, furfural catalytic hydrogenation is an open research line, which represents an attractive option for biomass valorization towards valuable chemicals and fuels.
124 citations
TL;DR: In this paper, the progress of mainly the last five years in direct hydrogenation of CO2 to value-added chemicals (e.g., CO, CH4, CH3OH, DME, olefins, and higher hydrocarbons) by heterogeneous catalysis and plasma catalysis is summarized, and research priorities for CO2 hydrogenation are proposed.
Abstract: Due to the increasing emission of carbon dioxide (CO2), greenhouse effects are becoming more and more severe, causing global climate change. The conversion and utilization of CO2 is one of the possible solutions to reduce CO2 concentrations. This can be accomplished, among other methods, by direct hydrogenation of CO2, producing value-added products. In this review, the progress of mainly the last five years in direct hydrogenation of CO2 to value-added chemicals (e.g., CO, CH4, CH3OH, DME, olefins, and higher hydrocarbons) by heterogeneous catalysis and plasma catalysis is summarized, and research priorities for CO2 hydrogenation are proposed.
TL;DR: In this paper, the use of zeolites for cyclic adsorption plasma catalysis in order to reduce the energy cost to decompose per VOC molecule and to regenerate zeolite via plasma is discussed.
Abstract: Non-thermal plasma technique can be easily integrated with catalysis and adsorption for environmental applications such as volatile organic compound (VOC) abatement to overcome the shortcomings of individual techniques. This review attempts to give an overview of the literature about the application of zeolite as adsorbent and catalyst in combination with non-thermal plasma for VOC abatement in flue gas. The superior surface properties of zeolites in combination with its excellent catalytic properties obtained by metal loading make it an ideal packing material for adsorption plasma catalytic removal of VOCs. This work highlights the use of zeolites for cyclic adsorption plasma catalysis in order to reduce the energy cost to decompose per VOC molecule and to regenerate zeolites via plasma.
TL;DR: Methods for optimizing CLEA preparations by, for example, adding proteic feeders to promote cross-linking, and strategies for making the pores accessible for macromolecular substrates are critically reviewed and compared.
Abstract: Biocatalysis has emerged in the last decade as a pre-eminent technology for enabling the envisaged transition to a more sustainable bio-based economy. For industrial viability it is essential that enzymes can be readily recovered and recycled by immobilization as solid, recyclable catalysts. One method to achieve this is via carrier-free immobilization as cross-linked enzyme aggregates (CLEAs). This methodology proved to be very effective with a broad selection of enzymes, in particular carbohydrate-converting enzymes. Methods for optimizing CLEA preparations by, for example, adding proteic feeders to promote cross-linking, and strategies for making the pores accessible for macromolecular substrates are critically reviewed and compared. Co-immobilization of two or more enzymes in combi-CLEAs enables the cost-effective use of multiple enzymes in biocatalytic cascade processes and the use of “smart” magnetic CLEAs to separate the immobilized enzyme from other solids has raised the CLEA technology to a new level of industrial and environmental relevance. Magnetic-CLEAs of polysaccharide-converting enzymes, for example, are eminently suitable for use in the conversion of first and second generation biomass.
TL;DR: In this article, the authors discuss persistent anthropogenic pollutants which have become a global concern owing to their widespread existence and unfamiliar threats to the environment and living organisms, such as microplastics.
Abstract: Microplastics are persistent anthropogenic pollutants which have become a global concern owing to their widespread existence and unfamiliar threats to the environment and living organisms. This stu ...
TL;DR: In this paper, the authors provide a summary of the accomplishments concerning catalytic ozonation to point to the major directions for choosing the catalysts in catalytic odonation in the future.
Abstract: Catalytic ozonation is believed to belong to advanced oxidation processes (AOPs). Over the past decades, heterogeneous catalytic ozonation has received remarkable attention as an effective process for the degradation of refractory organics in wastewater, which can overcome some disadvantages of ozonation alone. Metal oxides, metals, and metal oxides supported on oxides, minerals modified with metals, and carbon materials are widely used as catalysts in heterogeneous catalytic ozonation processes due to their excellent catalytic ability. An understanding of the application can provide theoretical support for selecting suitable catalysts aimed at different kinds of wastewater to obtain higher pollutant removal efficiency. Therefore, the main objective of this review article is to provide a summary of the accomplishments concerning catalytic ozonation to point to the major directions for choosing the catalysts in catalytic ozonation in the future.
TL;DR: In this paper, perovskite-type oxides lanthanum ferrite (LaFeO3) photocatalysts were successfully prepared by a facile and cost-effective sol-gel method using La(NO)3 and Fe( NO)3 as metal ion precursors and citric acid as a complexing agent at different calcination temperatures.
Abstract: Perovskite-type oxides lanthanum ferrite (LaFeO3) photocatalysts were successfully prepared by a facile and cost-effective sol-gel method using La(NO)3 and Fe(NO)3 as metal ion precursors and citric acid as a complexing agent at different calcination temperatures. The properties of the resulting LaFeO3 samples were characterized by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (IR), transmission electron microscopy (TEM), N2 adsorption/desorption and photoelectrochemical tests. The photoactivity of the LaFeO3 samples was tested by monitoring the photocatalytic degradation of Rhodamine B (RhB) and 4-chlorophenol (4-CP) under visible light irradiation, the highest photocatalytic activity was found for LaFeO3 calcined at 700 °C, which attributed to the relatively highest surface area (10.6 m2/g). In addition, it was found from trapping experiments that the reactive species for degradation were superoxide radical ions (O2−) and holes (h+). Photocurrent measurements and electrochemical impedance spectroscopy (EIS) proved the higher photo-induced charge carrier transfer and separation efficiency of the LaFeO3 sample calcined at 700 °C compared to that that calcined at 900 °C. Band positions of LaFeO3 were estimated using the Mott-Schottky plots, which showed that H2 evolution was not likely.
TL;DR: In this article, an optimization of a bench-scale UV-C photocatalytic process using a TiO2 catalyst suspension for degradation of two textile dyes, Acid Blue 113 (AB 113) and Acid Red 88 (AR 88), was investigated.
Abstract: Textile industries produce copious amounts of colored wastewater some of which are toxic to humans and aquatic biota. This study investigates optimization of a bench-scale UV-C photocatalytic process using a TiO2 catalyst suspension for degradation of two textile dyes, Acid Blue 113 (AB 113) and Acid Red 88 (AR 88). From preliminary experiments, appropriate ranges for experimental factors including reaction time, solution pH, initial dye concentration and catalyst dose, were determined for each dye. Response surface methodology (RSM) using a cubic IV optimal design was then used to design the experiments and optimize the process. Analysis of variance (ANOVA) was employed to determine significance of experimental factors and their interactions. Results revealed that among the studied factors, solution pH and initial dye concentration had the strongest effects on degradation rates of AB 113 and AR 88, respectively. Least-squares cubic regression models were generated by step-wise elimination of non-significant (p-value > 0.05) terms from the proposed model. Under optimum treatment conditions, removal efficiencies reached 98.7% for AB 113 and 99.6% for AR 88. Kinetic studies showed that a first-order kinetic model could best describe degradation data for both dyes, with degradation rate constants of k1, AB 113 = 0.048 min−1 and k1, AR 88 = 0.059 min−1.
TL;DR: In this paper, polyethyleneimine/polycaprolactone/Pd nanoparticles (PEI/PCL@PdNPs) composite catalysts were successfully designed and prepared by electrospinning and reduction methods using PEI/pCL elexctrospun fiber as carrier.
Abstract: Nano-sized palladium nanoparticles showed high catalytic activity with severe limitations in catalytic field due to the tendency to aggregate. A solid substrate with large specific surface area is an ideal carrier for palladium nanoparticles. In present work, polyethyleneimine/polycaprolactone/Pd nanoparticles (PEI/PCL@PdNPs) composite catalysts were successfully designed and prepared by electrospinning and reduction methods using PEI/PCL elexctrospun fiber as carrier. The added PEI component effectively regulated the microscopic morphology of the PEI/PCL fibers, following a large number of pit structures which increased the specific surface area of the electrospun fibers and provided active sites for loading of the palladium particles. The obtained PEI/PCL@PdNPs catalysts for reductions of 4-nitrophenol (4-NP) and 2-nitroaniline (2-NA) exhibited extremely efficient, stable, and reusable catalytic performance. It was worth mentioning that the reaction rate constant of catalytic reduction of 4-NP was as high as 0.16597 s−1. Therefore, we have developed a highly efficient catalyst with potential applications in the field of catalysis and water treatment.
TL;DR: In this paper, a review summarizes the evolution of PM mass emissions from gasoline vehicles placed in the market from early 1990s until 2019 in different parts of the world, and the analysis then extends to total and nonvolatile particle number emissions.
Abstract: The particulate matter (PM) emissions of gasoline vehicles were much lower than those of diesel vehicles until the introduction of diesel particulate filters (DPFs) in the early 2000s. At the same time, gasoline direct injection (GDI) engines started to become popular in the market due to their improved efficiency over port fuel injection (PFI) ones. However, the PM mass and number emissions of GDI vehicles were higher than their PFI counterparts and diesel ones equipped with DPFs. Stringent PM mass levels and the introduction of particle number limits for GDI vehicles in the European Union (EU) resulted in significant PM reductions. The EU requirement to fulfill the proposed limits on the road resulted to the introduction of gasoline particulate filters (GPFs) in EU GDI models. This review summarizes the evolution of PM mass emissions from gasoline vehicles placed in the market from early 1990s until 2019 in different parts of the world. The analysis then extends to total and nonvolatile particle number emissions. Care is given to reveal the impact of ambient temperature on emission levels. The discussion tries to provide scientific input to the following policy-relevant questions. Whether particle number limits should be extended to gasoline PFI vehicles, whether the lower limit of 23 nm for particle number measurements should be decreased to 10 nm, and whether low ambient temperature tests for PM should be included.
TL;DR: In this article, a review aims to promote the further study of gas-phase systems for CO2 reduction, by generally examining some previous approaches from liquid phase to gas phase systems.
Abstract: Electrochemical CO2 conversion offers a promising route for value-added products such as formate, carbon monoxide, and hydrocarbons. As a result of the highly required overpotential for CO2 reduction, researchers have extensively studied the development of catalyst materials in a typical H-type cell, utilizing a dissolved CO2 reactant in the liquid phase. However, the low CO2 solubility in an aqueous solution has critically limited productivity, thereby hindering its practical application. In efforts to realize commercially available CO2 conversion, gas-phase reactor systems have recently attracted considerable attention. Although the achieved performance to date reflects a high feasibility, further development is still required in order for a well-established technology. Accordingly, this review aims to promote the further study of gas-phase systems for CO2 reduction, by generally examining some previous approaches from liquid-phase to gas-phase systems. Finally, we outline major challenges, with significant lessons for practical CO2 conversion systems.
TL;DR: In this paper, a co-precipitation method was used to synthesize BiOCl nanoplates (diameter 140-220 nm, thickness 60-70 nm).
Abstract: In this work, we have synthesized BiOCl nanoplates (diameter 140–220 nm, thickness 60–70 nm) via a co-precipitation method, and then created Bi nanoparticles (diameter 35–50 nm) on the surface of BiOCl nanoplates via a NaBH4 reduction method. By varying the NaBH4 concentration and reaction time, the evolution of Bi nanoparticles was systematically investigated. It is demonstrated that with increasing the NaBH4 concentration (at a fixing reaction time of 30 min), BiOCl crystals are gradually reduced into Bi nanoparticles, and pure Bi nanoparticles are formed at 120 mM NaBH4 solution treatment. At low-concentration NaBH4 solutions (e.g., 10 and 30 mM), with increasing the reaction time, BiOCl crystals are partially reduced into Bi nanoparticles, and then the Bi nanoparticles return to form BiOCl crystals. At high-concentration NaBH4 solutions (e.g., 120 mM), BiOCl crystals are reduced to Bi nanoparticles completely with a short reaction time, and further prolong the treatment time leads to the transformation of the Bi nanoparticles into a two-phase mixture of BiOCl and Bi2O3 nanowires. The photodegradation performances of the samples were investigated by choosing rhodamine B (RhB) as the model pollutant and using simulated sunlight as the light source. It is demonstrated that an enhanced photodegradation performance can be achieved for the created Bi@BiOCl hybrid composites with appropriate NaBH4 treatment. The underlying photocatalytic mechanism was systematically investigated and discussed.
TL;DR: In this article, the authors analyze the intellectual property activities of the last five years (2014-2019) with a specific focus on biocatalysis applied to asymmetric synthesis.
Abstract: The broad interdisciplinary nature of biocatalysis fosters innovation, as different technical fields are interconnected and synergized. A way to depict that innovation is by conducting a survey on patent activities. This paper analyses the intellectual property activities of the last five years (2014–2019) with a specific focus on biocatalysis applied to asymmetric synthesis. Furthermore, to reflect the inventive and innovative steps, only patents that were granted during that period are considered. Patent searches using several keywords (e.g., enzyme names) have been conducted by using several patent engine servers (e.g., Espacenet, SciFinder, Google Patents), with focus on granted patents during the period 2014–2019. Around 200 granted patents have been identified, covering all enzyme types. The inventive pattern focuses on the protection of novel protein sequences, as well as on new substrates. In some other cases, combined processes, multi-step enzymatic reactions, as well as process conditions are the innovative basis. Both industries and academic groups are active in patenting. As a conclusion of this survey, we can assert that biocatalysis is increasingly recognized as a useful tool for asymmetric synthesis and being considered as an innovative option to build IP and protect synthetic routes.
TL;DR: In this paper, the historic progress of molybdenum-based catalysts in alkenes epoxidation is covered and an outlook on future challenge is discussed, and the challenges and perspectives to further enhance the catalytic performances in ALKENES are presented.
Abstract: Epoxides are important industrial intermediates applied in a variety of industrial processes. During the production of epoxides, catalysts have played an irreplaceable and unique role. In this review, the historic progress of molybdenum-based catalysts in alkene epoxidation are covered and an outlook on future challenge discussed. Efficient catalysts are demonstrated including soluble molybdenum complexes, polyoxometalates catalysts, molybdenum-containing metal organic frameworks, silica supported molybdenum-based catalysts, polymer supported molybdenum-based catalysts, magnetic molybdenum-based catalysts, hierarchical molybdenum-based catalysts, graphene-based molybdenum containing catalysts, photocatalyzed epoxidation catalysts, and some other systems. The effects of different solvents and oxidants are discussed and the mechanisms of epoxidation are summarized. The challenges and perspectives to further enhance the catalytic performances in alkenes epoxidation are presented.
TL;DR: In this paper, a comprehensive review of polymer-based photocatalytic materials is presented, focusing on polymer nanocomposites used as catalysts in fine organic reactions or in organic pollutants degradation.
Abstract: In the present comprehensive review we have specifically focused on polymer nanocomposites used as photocatalytic materials in fine organic reactions or in organic pollutants degradation. The selection of the polymer substrates for the immobilization of the active catalyst particles is motivated by several advantages displayed by them, such as: Environmental stability, chemical inertness and resistance to ultraviolet radiations, mechanical stability, low prices and ease availability. Additionally, the use of polymer nanocomposites as photocatalysts offers the possibility of a facile separation and reuse of the materials, eliminating thus the post-treatment separation processes and implicitly reducing the costs of the procedure. This review covers the polymer-based photocatalytic materials containing the most popular inorganic nanoparticles with good catalytic performance under UV or visible light, namely TiO2, ZnO, CeO2, or plasmonic (Ag, Au, Pt, Pd) NPs. The study is mainly targeted on the preparation, photocatalytic activity, strategies directed toward the increase of photocatalytic efficiency under visible light and reuse of the hybrid polymer catalysts.
TL;DR: The literature from the past few years dealing with hydrodesulfurization catalysts to deeply remove the sulfur-containing compounds in fuels is reviewed in this paper, where the typical transition metal sulfides (TMS) Ni/Co-promoted Mo, W-based bi-and tri-metallic catalysts for selective removal of sulfur from typical refractory compounds.
Abstract: The literature from the past few years dealing with hydrodesulfurization catalysts to deeply remove the sulfur-containing compounds in fuels is reviewed in this communication. We focus on the typical transition metal sulfides (TMS) Ni/Co-promoted Mo, W-based bi- and tri-metallic catalysts for selective removal of sulfur from typical refractory compounds. This review is separated into three very specific topics of the catalysts to produce ultra-low sulfur diesel. The first issue is the supported catalysts; the second, the self-supported or unsupported catalysts and finally, a brief discussion about the theoretical studies. We also inspect some details about the effect of support, the use of organic and inorganic additives and aspects related to the preparation of unsupported catalysts. We discuss some hot topics and details of the unsupported catalyst preparation that could influence the sulfur removal capacity of specific systems. Parameters such as surface acidity, dispersion, morphological changes of the active phases, and the promotion effect are the common factors discussed in the vast majority of present-day research. We conclude from this review that hydrodesulfurization performance of TMS catalysts supported or unsupported may be improved by using new methodologies, both experimental and theoretical, to fulfill the societal needs of ultra-low sulfur fuels, which more stringent future regulations will require.
TL;DR: In this article, the authors compared the product selectivity of several FTS catalysts and found that only iron catalysts consistently produced the most isomerized products of the catalysts that were tested.
Abstract: The bulk of the products that were synthesized from Fischer–Tropsch synthesis (FTS) is a wide range (C1–C70+) of hydrocarbons, primarily straight-chained paraffins. Additional hydrocarbon products, which can also be a majority, are linear olefins, specifically: 1-olefin, trans-2-olefin, and cis-2-olefin. Minor hydrocarbon products can include isomerized hydrocarbons, predominantly methyl-branched paraffin, cyclic hydrocarbons mainly derived from high-temperature FTS and internal olefins. Combined, these products provide 80–95% of the total products (excluding CO2) generated from syngas. A vast number of different oxygenated species, such as aldehydes, ketones, acids, and alcohols, are also embedded in this product range. These materials can be used to probe the FTS mechanism or to produce alternative chemicals. The purpose of this article is to compare the product selectivity over several FTS catalysts. Discussions center on typical product selectivity of commonly used catalysts, as well as some uncommon formulations that display selectivity anomalies. Reaction tests were conducted while using an isothermal continuously stirred tank reactor. Carbon mole percentages of CO that are converted to specific materials for Co, Fe, and Ru catalysts vary, but they depend on support type (especially with cobalt and ruthenium) and promoters (especially with iron). All three active metals produced linear alcohols as the major oxygenated product. In addition, only iron produced significant selectivities to acids, aldehydes, and ketones. Iron catalysts consistently produced the most isomerized products of the catalysts that were tested. Not only does product selectivity provide a fingerprint of the catalyst formulation, but it also points to a viable proposed mechanistic route.
TL;DR: In this paper, Ni-NiO/SiO2 nanoparticles were successfully anchored on an SiO2 support via a one-pot synthesis and used as heterogeneous catalysts for CO methanation.
Abstract: Highly-dispersed Ni-NiO nanoparticles was successfully anchored on an SiO2 support via a one-pot synthesis and used as heterogeneous catalysts for CO methanation. The as-obtained Ni-NiO/SiO2 catalyst possessed a high Ni content of 87.8 wt.% and exhibited a large specific surface area of 71 m2g−1 with a main pore diameter of 16.7 nm. Compared with an H2-reduced Ni-NiO/SiO2 (i.e., Ni/SiO2) catalyst, the Ni-NiO/SiO2 displayed a superior CO methanation performance. At the temperature of 350 °C, the Ni-NiO/SiO2 showed a CO conversion of 97.1% and CH4 selectivity of 81.9%, which are much better values than those of Ni/SiO2. After a 50-h stability test, the Ni-NiO/SiO2 catalyst still had an overwhelming stability retention of 97.2%, which was superior to the 72.8% value of the Ni/SiO2 catalyst.
TL;DR: In this article, the substitutional doping of tungsten oxide (WO3) with metal ions demonstrates a promising approach to enhance its photoelectrochemical (PEC) water splitting efficiency.
Abstract: The substitutional doping of tungsten oxide (WO3) with metal ions demonstrates a promising approach to enhance its photoelectrochemical (PEC) water splitting efficiency. In this article, the substitutional doping of Sn ions into WO3 lattice and its effect on optical, electrical, band edge, and PEC water splitting properties are explored. Sn-doped WO3 thin films were synthesized using a facile hydrothermal method. The characterization data reveal that the doping of Sn alters the morphology, induces multiple crystal phases, effects the crystal orientation, reduces the band gap, and increases the carrier density of WO3. With the uniform distribution of Sn ions in WO3 and the decreased charge transfer resistance at the electrode/electrolyte interface, the doped WO3 show notable enhancement in its PEC activity compared to the undoped WO3. The band edge study revealed that the introduction of Sn in WO3 lattice causes an increase in the energy distance between the valence band edge and Fermi level and, at the same time, induces a downward shift in both the valence and conduction band edges towards higher potentials with respect to reversible hydrogen electrode (RHE). Conclusively, this work shows significant and new insights about Sn-doped WO3 photoanodes and their influence on PEC water splitting efficiency.
TL;DR: In this article, a review of recent advances on CO2 cycloaddition to epoxide mediated by hybrid catalysts through organometallic or organo-catalytic species supported onto silica-, nanocarbon-, and metal-organic framework (MOF)-based heterogeneous materials, are highlighted and discussed.
Abstract: The conversion of carbon dioxide into valuable chemicals such as cyclic carbonates is an appealing topic for the scientific community due to the possibility of valorizing waste into an inexpensive, available, nontoxic, and renewable carbon feedstock In this regard, last-generation heterogeneous catalysts are of great interest owing to their high catalytic activity, robustness, and easy recovery and recycling In the present review, recent advances on CO2 cycloaddition to epoxide mediated by hybrid catalysts through organometallic or organo-catalytic species supported onto silica-, nanocarbon-, and metal–organic framework (MOF)-based heterogeneous materials, are highlighted and discussed
TL;DR: In this paper, the up-to-date findings of different chemicals/metal addition methods for improving hydrogen generation during dark fermentation (DF) processes have been quantitatively evaluated and thoroughly compared.
Abstract: Bio-hydrogen production (BHP) produced from renewable bio-resources is an attractive route for green energy production, due to its compelling advantages of relative high efficiency, cost-effectiveness, and lower ecological impact. This study reviewed different BHP pathways, and the most important enzymes involved in these pathways, to identify technological gaps and effective approaches for process intensification in industrial applications. Among the various approaches reviewed in this study, a particular focus was set on the latest methods of chemicals/metal addition for improving hydrogen generation during dark fermentation (DF) processes; the up-to-date findings of different chemicals/metal addition methods have been quantitatively evaluated and thoroughly compared in this paper. A new efficiency evaluation criterion is also proposed, allowing different BHP processes to be compared with greater simplicity and validity.