Environmental Catalysis Research Articles

Reactive Grinding synthesis of La(Sr,Ce)CoO3 and their properties in toluene catalytic total oxidation

AbstractPerovskites‐type metal oxides are an attractive alternative to noble metal‐based materials for environmental catalysis. Nevertheless, they suffer from major issues such as unattractive textural properties and lower intrinsic activities than those of noble metal counterparts. Reactive grinding (RG) has been already proved to be a powerful method to produce materials with improved textural properties. La1‐xA’xCoO3 (A’: Sr, Ce) perovskite‐type materials were synthesized by RG synthesis as a 3‐steps top down method: (i) conventional solid‐state reaction – SSR (leading to microcrystalline material); (ii) high energy ball milling – HEBM and (iii) low energy ball milling – LEBM. The physicochemical properties of perovskite materials were investigated by XRD, N2‐physisorption, H2‐TPR, O2‐TPD and XPS, while their catalytic performances were evaluated for the toluene total oxidation reaction. In this study we showed that the HEBM step leads in a drastic reduction in crystal size to nanometric scale along with aggregation into dense particles. The LEBM step allows the deagglomeration of particles and specific surface areas were significantly increased. Their performances in the toluene total oxidation increased along grinding steps and a maximum of catalytic performance was observed for La0.9Sr0.1CoO3. This material also exhibited a high catalytic stability as a function of the reaction time, under dry and wet air reaction conditions.

Valmet Oyj, Finland

Hydrogen is becoming important clean energy while zerovalent iron (ZVI) and ferroferric oxide are of great interest to many applications including environmental remediation and chemical catalysis. Here, we report production of hydrogen, zerovalent iron and ferroferric oxide octahedron by etching Al–Fe alloys using NaOH solutions. The rate of hydrogen generation increased with increasing NaOH concentration and the alloy's particle size and decreasing the alloy's Fe concentration. Alkaline etching Al–Fe alloy particles of 425–850 μm produced 19–53 μm ZVI particles, which had paralleled ravines of 0.2–0.3 μm wide on the surface and possessed specific surface areas of 30–70 m2/g. The microscale ZVI was highly active for the removal of a model pollutant acid orange 7 from water. After 3–6 h ageing in the alkaline etching solution, the microscale ZVI particles were transformed to octahedral ferroferric oxide with saturation magnetization of 68.2 emu/g and residual magnetization of 13.2 emu/g and a coercive force of 330 Oe. This study provides a new approach for a facile synthesis of highly active ZVI and octahedral ferroferric oxide along with on-board generation of hydrogen from Al–Fe alloys.

Review of supported metal nanoparticles: synthesis methodologies, advantages and application as catalysts

Supported metal nanoparticles, M-NPs, are of great scientific and economic interest as they encompass application in chemical manufacturing, oil refining and environmental catalysis. Oxidation and hydrogenation reactions are among the major reactions catalyzed by supported M-NPs. Although supported M-NPs are preferable due to their easy recovery and reuse, there are still some practical issues regarding their catalytic activity and deactivation. This review highlights the general features of supported M-NPs as catalysts with particular attention to copper, gold, platinum, palladium, ruthenium, silver, cobalt and nickel and their catalytic evaluation in various reactions. The catalytic performance of noble M-NPs has been explored extensively in various selective oxidation and hydrogenation reactions. In general, noble metals are expensive and sensitive to poisons. Despite their significant merits and potential (easily available, comparatively inexpensive and less sensitive to poisons), catalysis by base M-NPs is relatively less explored. Therefore, activity of base M-NPs can be improved, and still, there is potential for such catalysts.

Dual response mimetic enzyme of novel Co4S3/Co3O4 composite nanotube for antibacterial application

Novel Co4S3/Co3O4 composite nanotubes were first time successfully synthesized through the control of Na2S treatment of Co(CO3)0.35Cl0.20(OH)1.10 precursor and testified to having both oxidase-like and peroxidase-like catalytic activities. Through nanoscale Kirkendall effect, acicular precursor was vulcanized to form Co4S3/Co3O4 nanotubes (NTs). Co4S3/Co3O4 NTs exhibit great properties such as smaller Km and higher Vmax than natural horseradish peroxidase, favorable selectivity and ideal stability. Co4S3/Co3O4 NTs with promising biocompatibility can realize spectral sterilization towards Escherichia coli and Staphylococcus sciuri in the presence of low level H2O2. It turned to be that superoxide anion radical catalyzed by Co4S3/Co3O4 NTs not only oxidizes 3, 3′, 5, 5′-tetramethylbenzidine in the catalytic process but also eliminates gram-bacteria during sterilization. The successful synthesis of biofunctional Co4S3/Co3O4 NTs can serve as significant applications of new energy and environmental catalysis.

Plant-Extract-Mediated SnO2 Nanoparticles: Synthesis and Applications

Tin(IV) oxide nanoparticles (SnO2 NPs) have attracted great attention in various fields such as environmental remediation, sensing, catalysis, and lithium ion batteries. This led to an intense deve...

Structured Fe3O4-doped ordered mesoporous carbon catalyst supported on sintered metal fibers for intensifying phenol degradation

Microfibrous-structured catalysts are materials that address the mass/heat transfer limitation and achieve catalytic process intensification, showing great promise for enabling practical environmental catalysis such as continuous wastewater treatment process. In this work, Fe3O4-doped ordered mesoporous carbon (OMC) catalyst supported on porous sintered metal fibers (Fe-OMC/SMFs) was prepared using a new yet simple “one-pot” method and used as a Fenton-like heterogeneous catalyst. The obtained catalysts were carefully characterized by TGA-DTG, BET, XRD, SEM-EDS, XPS and H2-TPR techniques. Structured reactor was designed and developed using developed microfibrous-structured catalysts, demonstrating an excellent catalytic performance for continuous heterogeneous Fenton oxidation of phenol. Specifically, both phenol and H2O2 conversions increased slightly as carbonization temperatures increasing from 400 to 1000°C. Compared to Fe-OMC pellet catalyst, the developed structured catalyst showed an improved catalytic activity (i.e. ∼100 % phenol/H2O2 conversions), and remarkable long-term stability (i.e. ∼100 % phenol conversion over a 7-h longevity test). Additionally, the developed Fe-OMC/SMFs catalyst showed Fe leaching amounts of ∼10mgL−1 during reaction, being significantly lower than that of Fe-OMC pellet catalyst (i.e. ∼500mgL−1). Experimental results revealed that well-dispersed Fe3O4 nanoparticles in OMC and three-dimensional microfibrous networks and large void volume of SMFs support are significantly benefit to enhance mass transfer and contacting efficiency between active sites and reactants, and thus achieve the process intensification of catalytic degradation of phenol.

Lattice oxygen activation in transition metal doped ceria

Density functional theory calculations were carried out to investigate the influence of doping transition metal (TM) ions into the ceria surface on the activation of surface lattice oxygen atoms. For this purpose, the structure and stability of the most stable (111) surface termination of CeO2 modified by TM ions was determined. Except for Zr and Pt dopants that preserve octahedral oxygen coordination, the TM dopants prefer a square-planar coordination when substituting the surface Ce ions. The surface construction from octahedral to square-planar is facile for all TM dopants, except for Pt (1.14 eV) and Zr (square-planar coordination unstable). Typically, the ionic radius of tetravalent TM cations is much smaller than that of Ce4+, resulting a significant tensile-strained lattice and explaining the lowered oxygen vacancy formation energy. Except for Zr, the square-planar structure is the preferred one when one oxygen vacancy is created. Thermodynamic analysis shows that TM-doped CeO2 surfaces contain oxygen defects under typical conditions of environmental catalysis. A case of practical importance is the facile lattice oxygen activation in Zr-doped CeO2(111), which benefits CO oxidation. The findings emphasize the origin of lattice oxygen activation and the preferred location of TM dopants in TM-ceria solid solution catalysts.

Diospyros lotus-mediated Synthesis of Iron Oxide Nanoparticles and Their Application as a Catalyst in Fenton Reaction

Background: : Iron Oxide nanoparticles have enormous applications in environmental remediation and catalysis. The synthesis of such nanoparticles through a green approach provides a significant advantage due to the non-toxic nature of the ingredients involved. Method: : In the present work, Diospyros lotus fruit extract was used for the synthesis of iron oxide nanoparticles (NPs). The plant biomolecules were extracted employing two different solvents, i.e. water and methanol. The effect of both the extracts on the reduction of metal salt as well as on the shape and size of the produced NPs was investigated. Results:: UV-Visible spectroscopy confirmed the synthesis of iron oxide NPs, Fourier Transform Infrared (FTIR) spectrum depicted the presence of biomolecules on the surface of NPs as capping agents, X-ray Diffraction (XRD) diffractogram confirmed the crystalline structure of mixed iron oxide NPs and Scanning Electron Microscopy (SEM) images showed the spherical shape of NPs. The synthesized NPs were exploited to catalyze the degradation of methylene blue dye in the Fenton type catalytic reaction. The degradation reaction was monitored using UV-Visible spectroscopy, which indicated that the percent degradation increased from 15% (without iron oxide NPs) to 91% in the presence of organic extract prepared iron oxide NPs and to 81% in the presence of aqueous extract prepared iron oxide NPs. The effect of the concentration of methylene blue and iron oxide NPs on the degradation process was also investigated. Conclusion: : The results indicated the potential of synthesized nanoparticles to promote catalytic reactions involved in environmental remediation.

Strong interaction between Au nanoparticles and porous polyurethane sponge enables efficient environmental catalysis with high reusability

A novel and recoverable platform of polyurethane (PU) sponge-supported Au nanoparticle catalyst was obtained by a water-based in-situ preparation process. The structure, chemical, and morphology properties of this platform were characterized by XRD, TGA, SEM, FT-IR, and XPS. The Au/PU sponge platform exhibited excellent catalytic performances in catalytic reductions of p-nitrophenol and o-nitroaniline at room temperature, and both catalytic reactions could be completed within 4.5 and 1.5 min, respectively. Furthermore, the strong interaction between Au nanoparticles and the PU sponge enabled the catalyst system to maintain a high catalytic efficiency after 5 recycling times, since the PU sponge reduced the trend of leaching and aggregation of Au nanoparticles. The unique nature of Au nanoparticles and the porous PU sponge along with their strong interaction resulted in a highly efficient, recoverable, and cost-effective multifunctional catalyst. The AuNP/Sponge nanocatalyst platform has great potential for wide environmental and other catalytic applications.

New opportunities and challenges in energy and environmental catalysis (EEST2018)

New opportunities and challenges in energy and environmental catalysis (EEST2018)

Engineering and Economic Evaluation of Production of SnO2 Nanoparticles by Microwave-Assisted Green Synthesis

The synthesis of nanoparticles from noble metals such as tin (IV) oxide (SnO2) is a research in progress with a very wide application in various fields, such as environmental improvement, gas sensors, catalysis, and lithium-ion batteries. The purpose of this study was to evaluate the economic feasibility of producing tin (IV) oxide (SnO2) nanoparticles using the microwave-assisted green synthesis method on an industrial scale for 10 years by evaluating from an engineering and economic perspective. Various economic parameters are used to analyze economic viability, including Gross Profit Margin (GPM), Payback period (PBP), Cumulative Net Present Value (CNPV), as well as economic variations in sales, taxes, raw materials, labor wages, and utilities to ascertain project viability. Technical analysis to produce 8.54 kg of SnO2 nanoparticles per day shows a total production cost of 1,982,243,613.12 IDR and a total investment cost of 1,732,590,765.12 IDR. The resulting gross profit margin is 39,231,578,268 IDR/year, the profit is relatively economical, so this project can be run for 10 years under ideal conditions. This research is expected to be a reference for technical and economic analysis of industrial scale production of SnO2 nanoparticles.

Phosphorus-doped carbon fibers as an efficient metal-free bifunctional catalyst for removing sulfamethoxazole and chromium (VI).

Developing an efficient and metal-free bifunctional catalyst for the simultaneous degradation of antibiotic and reduction of Cr (VI) has been regarded as increasingly attractive yet challenging objectives in the environmental catalysis field. Herein, phosphorus-doped carbon fibers (P-CFs) was innovatively prepared by doping and calcination methods, characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Sulfamethoxazole (SMX) as the target contaminant was selected to evaluate the catalytic activity of P-CFs in PMS activation, over 90% SMX removal and 82.75% mineralization were high-efficiently achieved in the P-CFs/peroxymonosulfate (PMS) system. Particularly, P-CFs/PMS system exhibited a superior catalytic oxidation performance over a wide pH range (3.5-9.5) and even in the complicated water matrix. Surprisingly, the presence of humic acid (HA) in the P-CFs/PMS system could achieve about 2 times enhancement on SMX removal, different from most reports about the inhibition of HA in PMS activation. More importantly, Brunauer-Emmett-Teller (BET) method and XPS analysis revealed that the highly toxic Cr (VI) could be reduced to Cr (III) by P-CFs. Furthermore, electron spin resonance (ESR) combined with various trapping agents demonstrated that SO4•-, •OH and 1O2. were generated and participated in the SMX degradation, while the free electron in P-CFs played a main role in Cr (VI) reduction. This finding not only provided a high-efficiency strategy in the treatment of wastewaters containing organic contaminants and heavy metals Cr (VI), but might open new insights into an innovative metal-free catalyst in environment remediation.

Self-sacrificing template strategy to facilely prepare well-defined SnO2@C quasi-hollow nanocubes for lithium-ion battery anode

With many attracted physicochemical properties, hollow nanostructures have gained extensive attention in field of anode materials for lithium-ion batteries. The template-assisted method is a common and simple method to prepare hollow nanomaterials. However, the geometry of 0D resultant hollow nanomaterials from template-assisted methods is mostly spherical due to the difficulties ranging from forming uniform coating around high curvature surfaces to the deficiency of nonspherical templates available. Herein, we successfully demonstrate a self-sacrificing template strategy for facile preparation of a well-defined nonspherical SnO2@C quasi-hollow nanocubes composite (SnO2@C q-HNCs) for the first time. More importantly, thus cubic geometry offers the SnO2@C q-HNCs several architectural advantages in lithium storage: (i) the external carbon coating and internal hollow space can availably mitigate a large volume expansion, and thus guarantee the improved structural stability; (ii) the thin SnO2 shell can dramatically lower the diffusion distances of electrons and ions, therefore accelerates ions and electrons transport; (iii) the carbon can enhance the conductivity of whole composite, and accordingly enhances the rate property; and (iv) the well-defined cubic geometry with the accessible exposed active planes can offer more lithium storage sites and enlarge the contact area between SnO2@C q-HNCs and electrolytes, hence promote the diffusion efficiency. Consequently, the SnO2@C q-HNCs electrodes reveal superior electrochemical performance, delivering 732 mAh g−1 after 350 cycles at 200 mA g−1 as well as 545 mAh g−1 at even 3000 mA g−1. Broadly, this strategy may be extended to preparation of other nonspherical metal oxides/carbon nanocomposites for applications in various fields such as energy storage and conversion, environmental analysis, catalysis, drug delivery, and sensor.

Nanostructured MoO3 for Efficient Energy and Environmental Catalysis.

This paper mainly focuses on the application of nanostructured MoO3 materials in both energy and environmental catalysis fields. MoO3 has wide tunability in bandgap, a unique semiconducting structure, and multiple valence states. Due to the natural advantage, it can be used as a high-activity metal oxide catalyst, can serve as an excellent support material, and provide opportunities to replace noble metal catalysts, thus having broad application prospects in catalysis. Herein, we comprehensively summarize the crystal structure and properties of nanostructured MoO3 and highlight the recent significant research advancements in energy and environmental catalysis. Several current challenges and perspective research directions based on nanostructured MoO3 are also discussed.

Functionalized MoS2/polyurethane sponge: An efficient scavenger for oil in water

Advanced materials with special wettability hold promise in environmental remediation, catalysis or superfluid, and have attracted a great deal of interest in the last years. Herein, a composite material consisting of a molybdenum sulfide/polyurethane sponge (MoS2/PU) was fabricated through MoS2 nanosheets loading onto PU using high-intensity sonication and subsequent chemical functionalization by in-situ generated diazonium salts. The MoS2 enhanced the hydrophobicity and roughness of the PU sponge and its surface could be effectively modified with aryl and carbon-fluorine groups through diazonium chemistry. The resulting F-MoS2/PU interface exhibited exceptional superhydrophobic/superoleophilic wettability, and allowed to separate oil/water mixtures and eliminate selectively oil from underwater or emulsions. Besides, due to the cavitation effect of high-intensity ultrasound, the exfoliated MoS2 sheets were strongly anchored onto the PU sponge. Loading MoS2 and/or diazonium molecules did not induce any adverse effect on the adsorption capacity of the sponge with values ranging from 25 to 90 gg−1 for different organic solvents (hexane, diethyl ether, ethanol, toluene, rapeseed oil, acetonitrile, dichloromethane and chloroform). Additionally, the hydrophobic groups covalently bonded to the surface conferred excellent stability to the MoS2/PU material during repeated cycles of oil/water separation, or upon exposure to harsh environments (−20 or +120 °C, acid solution of pH = 1 and base solution of pH = 14, NaCl solution of 3.0%, natural seawater, ethanol and chloroform).

Novel porous ceramic sheet supported metal reactors for continuous-flow catalysis

A novel porous ceramic sheet supported nickel particles reactor was obtained by an in-situ preparation method. This reactor was then used to investigate continuous-flow catalysis of nitroaromatic compounds and methyl orange. The details of the structure and morphology were characterized by XRD, SEM, XPS, Raman, element mapping, mercury intrusion method and Archimedes principle. The porous ceramic sheet supported Ni particles reactor exhibited excellent catalytic performance in the catalytic reduction of p-nitrophenol and methyl orange by sodium borohydride at room temperature. Both the conversion of p-nitrophenol (5 mM) and methyl orange (0.3 mM) reached nearly 100% at the injection speed of 2.67 mL·min−1. In addition, it maintained conversions of 100% after 10 recycling time since the porous ceramic sheet could reduce the aggregation for Ni particles. Furthermore, the chemisorbed oxygen, and the strong interaction between Ni and porous ceramic sheet resulted in a highly efficient, recoverable, and cost-effective multifunctional reactor. All of these advantages present new opportunities to be implemented in the field of waste water treatment and environmental toxicology. Ultimately, the porous ceramic sheet could also support other metal nanomaterial, and used in other fields of environmental catalysis.

Glycerol molecules in nano channels of NaY and USY zeolites

Rich nano channels of zeolites give themselves excellent adsorption capacity, which have been widely used in environmental protection and catalysis. The adsorption process and existential form of the molecules in the nano channels are affected by the spatial confinement and regularity of the nanoporous channels. In this work, the adsorption of glycerol molecules in NaY and USY zeolites nano channels were studied. The results showed that adsorption quantity of glycerol molecules in nano channels and formation of glycerol molecular clusters were significantly affected by the static adsorption time. Due to the spatial confinement of the nanoporous channel, the H⋯O bond length and the HO⋯O angle were reduced. TEM scanning results indicated that the size of glycerol molecular cluster in nano channel was smaller than that of the bulk ones outside nano channel. 1H NMR results suggested that the spin motion of the hydroxyl hydrogen bond was enhanced. Computer simulation results showed that intermolecular hydrogen bonds were formed between the glycerol molecular cluster and oxygen atoms on the channel wall. This work may show new light on the study of molecular immobilization in spatial confinement.

Hierarchical Porous Wood Cellulose Scaffold with Atomically Dispersed Pt Catalysts for Low-Temperature Ethylene Decomposition.

Despite the excellent catalytic properties of individual nanoparticles and atomic clusters, the current capabilities to assemble them into a complex system are insufficient for many practical applications. An objective of this work is to develop a fabrication technology that allows for the simultaneous control of the nanoparticle surface chemistry, elemental distribution, microscale geometry, and large-scale assembly. Using a cellulose structure derived from wood, we fabricate hierarchical porous cellulose scaffolds combining with cerium-doped TiO2. This hybrid material serves as the support for atomically dispersed Pt catalysts and is used to successfully decompose ethylene at 0 °C. The fabrication concept developed in this work would allow mitigating the conflict between the required large active surfaces and the difficulties in handling nanopowders in environmental catalysis, including food preservation and indoor air purification. We thus discover a promising route to manufacture multifunctional materials with complex structures by combining a controllable chemical synthesis with the nature-designed wood scaffold.

Spatial confinement of cobalt crystals in carbon nanofibers with oxygen vacancies as a high-efficiency catalyst for organics degradation.

Catalytic activation of peroxymonosulfate (PMS) to generate radicals has received considerable and increasing attention in the environmental catalysis for treatment of recalcitrant pollutants. In the current study, a series of highly porous, cobalt-loaded activated carbon nanofibers (Co/CNFs) were prepared by one-pot electrospinning followed by thermal treatment. Observations showed that the limited addition of Co (≤8%) had no obvious effect on the morphology of the resulted CNFs, but it did affect the surface area and porosity of the CNFs as well as the carbon graphitic process during the carbonization. The applicability of this confined nanoreactor used in sulfate-radical based advanced oxidation processes (SR-AOPs) was systematically investigated. The effect of pH on the radical generation and organics removal was examined. The oxygen species on the CNFs played an important role in the activation of PMS. The carbon layer encapsulated on the Co crystal surface inhibited the Co leaching during the reaction and increased the catalytic efficiency due to the enhanced interfacial charge transfer. Meanwhile, the carbon layer could synchronously function as the adsorptive active sites during the degradation of organics. Results showed that the Co/CNFs possessed the highest catalytic efficiency under neutral pH, corresponding to the sulfate radical generation. The Co leaching and XPS results showed that the Co served as the main active site in PMS activation.

Synergetic Photocatalytic Pure Water Splitting and Self-Supplied Oxygen Activation by 2-D WO3/TiO2 Heterostructures

Oxygen generation from the endogenous reaction and accompanying activation is of vital importance in ubiquitous environmental and biological catalysis. In this paper, we demonstrated the constructi...