Cobalt Silicate Research Articles

Hollow Co2SiO4 microcube with amorphous structure as anode material for construction of high performance lithium ion battery

To solve the problem of large volume expansion of cobalt silicate electrode during cyclic process and low electric conductivity, Co2SiO4 with amorphous, porous and hollow structure is firstly designed to act as high performance lithium ion battery (LIB) anode. Compared with crystalline materials, the amorphous Co2SiO4 microcube could facilitate Li+ diffusion to enhance their performance of LIBs because of isotropic characteristics. Here, the amorphous Co2SiO4 hollow microcube (named as a-Co2SiO4 HC) was prepared by mild hydrothermal method with use of MnCO3 microcube as hard-template. Benefitting from the advantages of such structure, Li+ diffusion rate was greatly accelerated and the volume expansion can be alleviated. The as-prepared amorphous Co2SiO4 hollow microcube as anode material of LIBs exhibited significantly improved electrochemical performance of 610 mAh g−1 even after 380 cycles at 500 mAh g−1 than their crystalline counterpart (only 280 mAh g−1 retained after 380 cycles). This work is a good try to employ amorphous metal silicate in LIBs and simultaneously motivate the exploration of other amorphous materials for high performance LIBs, SIBs, catalysts, etc.

Hierarchical mesoporous cobalt silicate architectures as high-performance sulfate-radical-based advanced oxidization catalysts

Self-sacrificial biomass-derived silica is a rising and promising approach to fabricate large metal silicates, which are practical water treatment agents ascribed for easy sedimentation and separation. However, the original biomass architecture is difficult to be maintained and utilized. Furthermore, sufficient ion diffusion pathways need to be created to satisfy massive mass transport in large bulk materials. Herein, a series of metal silicates, including cobalt silicate (CoSiOx), copper silicate, nickel silicate, iron silicate, and magnesium silicate, are synthesized from Indocalamus tessellatus leaf as the biomass-derived silica source and investigated as catalysts in sulfate-radical-based advanced oxidization processes (SR-AOPs) for the first time. Among them, CoSiOx presents an analogical sandwich structure as a leaf-derived template of micron-level size. More importantly, the interior hollow nanotubes assembled by small nanosheets provide numerous pathways for ion diffusion and remarkably promote the mass transport in such large bulk materials. Owing to the combination of the unique structure with the high reactivity of Co (II) toward peroxymonosulfate, CoSiOx exhibits excellent catalytic performance with 0.242 and 0.153 min−1 rate constants for the removal of methylene blue and phenol, respectively, which outperforms/is comparable to that of the reported nanomaterials toward organic contaminants in SR-AOPs.

In-depth characterisation of metal-support compounds in spent Co/SiO2 Fischer-Tropsch model catalysts

Only little is known about the formation and morphology of metal-support compounds (MSCs) in heterogeneous catalysis. This fact can be mostly ascribed to the challenges in directly identifying these phases. In the present study, a series of Co/SiO2 model catalysts with different crystallite sizes was thoroughly characterised with focus on the identification of cobalt silicate, which is the expected metal-support compound for this particular catalyst system. The catalysts were exposed to simulated high conversion Fischer-Tropsch environment, i.e. water-rich conditions in the presence of hydrogen. The transformation of significant amounts of metallic cobalt to a hard-to-reduce phase has been observed. This particular MSC, Co2SiO4, was herein identified as needle- or platelet-type cobalt silicate structures by means of X-ray spectroscopy (XAS) and high-resolution scanning transmission electron microscopy (HRSTEM) in combination with elemental mapping. The metal-support compounds formed on top of fully SiO2-encapsulated nanoparticles, which are hypothesised to represent a prerequisite for the formation of cobalt silicate needles. Both, the encapsulation of cobalt nanoparticles by SiO2 via creeping, as well as the formation of these structures, were seemingly induced by high concentrations of water.

Fast and Fully Scalable Synthesis of Graphene Oxide from Cellulose by Catalytic Acid Spray Method (CAS)

Graphene oxide (GO) characterized by high electrical conductivity and thermal stability can be considered as a single monomolecular graphite layer, containing numerous functional oxygen groups such as epoxide, carbonyl, carboxyl and hydroxyl groups. Therefore, in this work, we have come to produce high quantities of GO sheets by innovative, simple and hydrazine-free methods based on rice straw, using catalytic acid spray method (CAS) in the presence of cobalt silicate nanoparticle as a catalyst. The structure of graphene oxide was characterized by FTIR, Raman, HR-TEM and DLS. FTIR shows that GO comprises some efficient hydroxyl (OH), epoxy (cyclic ether), carboxyl and carbonyl groups. XRD shows that the interlayer spacing of GO prepared by our techniques is higher to some extent than the interlayer spacing of other GO produced by another processes. We can say that, GO sheets can be produced for various applications, in large quantities, high efficiency and low cost, by adjusting the parameters such as acid strength or catalytic doses used in the CAS method. Thereby, we can overcome the weak inter-bond between the GO sheets without cracking them.

Cobalt silicate hydroxide nanosheets in hierarchical hollow architecture with maximized cobalt active site for catalytic oxidation

A facile dissolution-regrowth strategy was developed in synthesis of hierarchical hollow nanospheres of cobalt silicate hydroxide (CSH-80) for maximizing cobalt active sites on unit mass basis, which is different from the conventional supported cobalt catalysts. Due to the unique design and elaborative nanoarchitecture, the cobalt active center can be homogeneously dispersed into the structured catalyst, achieving the maximum exposure of the cobalt center for reaction. In activation of peroxymonosulfate (PMS) for degradation of organic contaminants, CSH-80 exhibited outstanding catalytic performance, excellent physicochemical stability and long-term durability, giving 1.9–3.1 folds higher efficiency than that of the conventional supported cobalt catalysts. The turnover frequency of CSH-80 in organic oxidation was 2.0–3.2 folds higher than that of the conventional supported cobalt catalysts. The effects of reaction parameters on contaminant degradation were systematically investigated. The catalytic oxidation mechanism was further elucidated by the quenching tests, electron paramagnetic resonance and photoluminescence studies. The design concept in this study will provide new opportunities for future development of high-performance cobalt-based heterogeneous catalysts in environmental remediation.

Novel ceramic paper structures for diesel exhaust purification.

The catalytic combustion of diesel soot is addressed with flexible and structured "paper catalysts". Two different series of catalysts were prepared either by drip impregnation or by a spray method to deposit a mixture of Co, Ba, and K or a mixture of Co and Ce onto SiO2-Al2O3 ceramic paper matrixes. In every case, CeO2 nanoparticles were added to bind the ceramic fibers. SEM images showed that the impregnation method generated catalytic particles concentrated as large chunks (> 10μm), mainly at ceramic fiber crossings, whereas the spray method produced smaller catalytic particles (< 1μm) well distributed throughout the ceramic paper. Besides, Co-Ba-K particles appeared better dispersed on the surface of ceramic fibers than Co-Ce due to the presence of K. Additionally, FTIR spectra showed the formation of O22- and O2- species associated with CeO2 (binder) on the samples containing potassium which gave the Co-Ba-K-ceramic paper good catalytic properties, thus making the Co-Ba-K drop impregnated the best catalyst both considering activity and stability. Successive temperature programmed oxidation (TPO) runs up to 700°C caused the formation of cobalt silicates in the catalytic ceramic paper prepared by the spray method, as indicated by TPR. The formation of these species was probably favored by the smaller size of cobalt particulates and their higher dispersion in the catalysts prepared by the spray method. This provoked the partial loss of the redox properties of Co3O4. TPR experiments also indicated the formation of BaCoO3 in Ba-containing ceramic paper, which could help in maintaining the catalyst activity after several TPO runs through the capacity of this mixed perovskite-type oxide to trap and release NOx.

Liquid phase oxidation of cyclohexane over mesoporous cobalt silicates molecular sieves synthesized in strong acidic media by assembly of preformed CoS-1 precursors with triblock copolymer

Cobalt–incorporated mesoporous silica materials [MCoS(n), n = Si/Co = 20; 60] have been successfully prepared in strong acidic media by assembly of preformed CoS-1 precursors with triblock copolymer of the Pluronic type (P123) by a two steps procedure. They were characterized by various techniques including XRD, BET, FT-IR spectroscopy and diffuse reflectance UV–Vis (DRUV–Vis). The results show that the calcined MCoS materials contain Co(II) ions in tetrahedral environments under low and high Co content and the mesoporous walls contain the MFI structure building units. Liquid phase oxidation of cyclohexane using TBHP as oxidant was investigated on MCoS(n). The major products detected are cyclohexanone and cyclohexanol in all cases. The MCoS(n) catalysts are more active when water free TBHP was used and the conversion of cyclohexane increases when cyclohexane to TBHP molar ratio increases from 1:1 to 1:2, while the cyclohexanol selectivity decreases, which is ascribed to a further oxidation of cyclohexanol to cyclohexanone. The catalytic activity of MCoS(n) materials is enhanced as the cobalt content increases. It is worth noting that MCoS(20)is more active than Co-SBA15(20). The most active catalyst MCoS(20) acts as truly heterogeneous catalyst and was very stable after four runs.

The obtaining and properties of asymmetric ion transport membrane for separating of oxygen from air

The bilayer oxygen-permeable membrane, consisting of a thin-film dense composite based on Co3O4 - 36 wt. % Bi2O3, and of a porous ceramic substrate of Co2SiO4, was synthesized and characterized. The way for obtaining of porous ceramic based on cobalt silicate was found, while the microstructure and the mechanical properties of porous ceramic were studied. Layered casting with post-pressing was used to cover the surface of porous support of Co2SiO4 by the Co3O4 - 36 wt. % Bi2O3 - based film. Transport properties of the asymmetric membrane have been studied, the kinetic features of oxygen transport have been established, and the characteristic thickness of the membrane has been estimated. The methods to prevent the high-temperature creep of ion transport membranes based on solid/molten oxides, which are the promising ones for obtaining of pure oxygen from air, are proposed and discussed.

P-doping Li2CoSiO4/C cathode material: A joint experimental and theoretical study

Lithium cobalt silicate Li2CoSiO4 is a promising but very challenging high energy cathode material for lithium-ion battery. This work presents a systematic study of synthesis-structure-performance of Li2CoSiO4, in which carbon coating and P doping are incorporated in nano-particles synthesized by hydrothermal reactions and the collaboration among different mechanisms of modification results in controlled synthesis of polymorphs and advanced electrochemical performance. The carbon coated Li2CoSiO4 sample exhibits improved electrochemical performance with a reversible capacity of 112 mAh g−1 at room temperature. Furthermore, 10% P substituted Si in Li2CoSiO4/C demonstrates a single form in polymorphs with much higher discharge capacity of 144 mAh g−1. The analysis of cyclic voltammograms and ex situ XRD indicates Li2CoSiO4 bears electrochemical characters of stable structure and high discharge voltage plateau during cycling. First-principles calculations on P-doping Li2CoSiO4 models find the P-doping site to be a repulsively positive center that suppresses the asymmetrical stress of Li+ and Peierls distortion in the delithiated structures, therefore promoting the deintercalation in the electrochemical performance.

Effect of cobalt loading on structure and catalytic behavior of CoOx/SiO2 in CO2-assisted dehydrogenation of ethane

Structural and catalytic properties of flame-made CoOx/silica catalysts for the CO2-assisted dehydrogenation of ethane were observed to vary strongly depending on the Co-loading (0.1–4.5 wt%). X-ray diffraction showed that both fresh and spent catalysts were amorphous. UV–vis, XPS and XAS indicated that at Co-loadings lower than about 1 wt% highly dispersed tetrahedral Co2+ strongly bound to the silica matrix in a cobalt silicate like mixed oxide phase, was the prevalent cobalt species. At higher Co-loadings the presence of CoOx clusters became significant. All cobalt species showed strong resistance towards reduction, as shown by TPR. Comparative XAS analyses of catalysts exposed to ambient atmosphere and thermally pretreated catalysts (400 °C, vacuum for 2 h) showed that the presence of water facilitates the transformation of tetrahedrally to octahedrally coordinated Co2+. Best catalytic performance was achieved with a catalyst containing 0.75 wt% Co, affording 46% ethane conversion at 85% selectivity to ethene under the standard reaction conditions applied (700 °C, CO2/C2H6 ratio of 2.5 and gas hourly space velocity of 6000 L kg−1 h−1). Some coke deposition in the form of disordered and graphitic carbon was observed with all Co-loaded catalysts. The catalyst with optimal Co-loading (0.75 wt%) showed nearly stable performance during 10 h time-on-stream.

Synthesis and superior lithium storage performances of hybrid hollow urchin-like silicate constructed by nanotubes wrapped in reduced graphene oxides

Hybrid hollow urchin-like cobalt and copper silicate constructed by nanotubes encapsulated in graphene nanosheets composites were successfully prepared using graphene oxide as carrier and silica spheres as template, which were done through a well-known Stȍber process and a hydrothermal method. In fact, the synthesis of hybrid urchin-like silicate constructed by nanotubes through onestep hydrothermal reaction has rarely been reported.The electrochemical performances of the composites as lithium-ion battery anode materials were studiedfor the first time. As novel anode materials of Li-ion batteries, the special hollow urchin-like structure not only could facilitate the Li+ diffusion and electron transport but alsocouldaccommodate the volume variation during the conversion reactions. In addition, the introduction of graphene can make the electrical conductivity better. Graphene wrapped hollow urchin-like silicate compositespossesses superior electrochemical cycling properties. The first discharge capacity is1955.2mAh/g with a current density of 300mA/g. The unique well-designed configuration presents a beneficial method to synthesize efficient and high performance electrode materials for advanced power applications.

Exploring pretreatment effects in Co/SiO2 Fischer-Tropsch catalysts: Different oxidizing gases applied to oxidation-reduction process

The influence of reduction-oxidation-reduction (ROR) pretreatment on 20% Co/SiO2 has been investigated using different oxidizing gases including water vapor and oxygen in the oxidation step. In this study, the evolution concerning the SiO2 structure and the cobalt phase and morphology is clearly elucidated at each step of reduction, oxidation and subsequent re-reduction. It is demonstrated that ROR treatment using both oxygen and water vapor decreases the average cobalt particle size. However, the catalytic performance affected in FTS is considerably different. ROR treatment in oxygen results in an increase in catalytic activity. In contrast, the water vapor applied in oxidation step obviously deactivates cobalt catalyst and enhances selectivity of methane. The resulting deactivation is ascribed to the promoted formation of irreducible cobalt silicate through the reaction between water vapor caused surface SiOH groups and oxidized cobalt (CoO) in spite of unchanged surface area and pore structure on SiO2. The characterization data reveals that the re-dispersion of cobalt particles occurs at oxidation step rather than the re-reduction step. In addition, the results indicate that the ROR treatment reducing the cobalt particle size depends on its initial size as no re-dispersion can be observed in the case of particles smaller than about 11nm. Furthermore, the water vapor shows more effective re-dispersion in cobalt particles compared with the use of oxygen. This study provides fundamental insights into the control of catalytic activity, product selectivity, and catalyst stability over supported cobalt catalysts by understanding the evolution of catalyst structure through ROR treatment in different chemical environment.

Size dependent stability of cobalt nanoparticles on silica under high conversion Fischer-Tropsch environment.

Highly monodisperse cobalt crystallites, supported on Stöber silica spheres, as model catalysts for the Fischer-Tropsch synthesis were exposed to simulated high conversion environments in the presence and absence of CO utilising an in house developed in situ magnetometer. The catalyst comprising the smallest crystallites in the metallic state (average diameter of 3.2 nm) experienced pronounced oxidation whilst the ratio of H2O to H2 was increased stepwise to simulate CO conversions from 26% up to complete conversion. Direct exposure of this freshly reduced catalyst to a high conversion Fischer-Tropsch environment resulted in almost spontaneous oxidation of 40% of the metallic cobalt. In contrast, a model catalyst with cobalt crystallites of 5.3 nm only oxidised to a small extent even when exposed to a simulated conversion of over 99%. The largest cobalt crystallites were rather stable and only experienced measurable oxidation when subjected to H2O in the absence of H2. This size dependency of the stability is in qualitative accordance with reported thermodynamic calculations. However, the cobalt crystallites showed an unexpected low susceptibility to oxidation, i.e. only relatively high ratios of H2O to H2 partial pressure caused oxidation. Similar experiments in the presence of CO revealed the significance of the actual Fischer-Tropsch synthesis on the metallic surface as the dissociation of CO, an elementary step in the Fischer-Tropsch mechanism, was shown to be a prerequisite for oxidation. Direct oxidation of cobalt to CoO by H2O seems to be kinetically hindered. Thus, H2O may only be capable of indirect oxidation, i.e. high concentrations prevent the removal of adsorbed oxygen species on the cobalt surface leading to oxidation. However, a spontaneous direct oxidation of cobalt at the interface between the support and the crystallites by H2O forming presumably cobalt silicate type species was observed in the presence and absence of CO. The formation of these metal-support compounds is in accordance with conducted thermodynamic predictions. None of the extreme Fischer-Tropsch conditions initiated hydrothermal sintering. Seemingly, the formation of metal-support compounds stabilised the metallic crystallites and/or higher partial pressures of CO are required to increase the concentration of mobile, cobalt oxide-type species on the metallic surface.

The genesis of supported cobalt catalysts

The general objectives of this research were to investigate the effect of the support and the gas atmosphere on the decomposition and reduction of cobalt nitrate hexahydrate supported on silica and alumina to gain a greater understanding of the calcination and reduction procedures used in catalyst manufacturing processes. The decomposition was followed by TGA-DSC-MS. The observed breakdown on the unsupported complex is similar but not identical to previous reports with NO detected as an evolved gas. In an oxygen/argon atmosphere the decomposition is generally simplified for the supported samples with a fewer number of weight loss events. When supported on alumina, cobalt nitrate is stabilised with decomposition events shifting to higher temperatures, whereas when supported on silica, cobalt nitrate is destabilised with only one significant decomposition event, which occurs at a lower temperature than that of the unsupported complex. In a hydrogen/nitrogen atmosphere partial decomposition of cobalt nitrate occurs before reduction is initiated with both supported samples. When supported on alumina, cobalt nitrate reduction is catalysed with the two events that occur below 350 °C happening at lower temperatures, while reduction above 350 °C is moved to higher temperatures. The silica-supported complex in contrast exhibits reduction events that are all reduced in temperature relative to the unsupported salt. However, there is evidence of the formation of cobalt silicate with a high temperature reduction. The study has shown that the calcination and direct reduction of supported cobalt nitrate is significantly affected by the support and that different conditions are required to achieve the same state.

Insights into the promotional roles of palladium in structure and performance of cobalt-based zeolite capsule catalyst for direct synthesis of C5–C11 iso-paraffins from syngas

Pd-promoted zeolite capsule catalyst (Co/Pd/SiO2-HZSM5) was developed by coating H-ZSM-5 zeolite shell over Pd-modified core catalyst (Co/Pd/SiO2), and employed for direct synthesis of C5–C11 iso-paraffins from syngas via Fischer-Tropsch synthesis (FTS). The roles of Pd promotion in structure and performance of the capsule catalyst for C5–C11 iso-paraffins synthesis were deeply studied. Structure characterizations (XRD, FTIR, TPR, and XPS) indicated that the main cobalt species in Pd-promoted capsule catalyst was cobalt silicate, while Co3O4 was the predominant cobalt species in un-promoted capsule catalyst (Co/SiO2-HZSM5). Evolution of cobalt species in the synthesis of Pd-promoted capsule catalyst revealed that Pd improved the formation of cobalt silicate in strong basic TPAOH solution during the hydrothermal synthesis of H-ZSM-5 zeolite shell. It was found that Pd not only promoted the reduction in cobalt oxides, but also improved the reduction in cobalt silicate, which could not be reduced under traditional reduction condition for cobalt-based FTS catalysts. Catalytic tests indicated that Pd-promoted capsule catalyst exhibited highly enhanced performance for C5–C11 iso-paraffins synthesis with molar ratio of iso-paraffins to n-paraffins up to 1.03. Long-chain hydrocarbons were completely eliminated in the capsule catalyst as a consequence of spatial confinement effect of the H-ZSM-5 zeolite shell. The hydrogenation of olefins to paraffins, which was enhanced by Pd promotion, together with the hydrocracking and isomerization of primary hydrocarbons, contributed to the high selectivity of C5–C11 iso-paraffins in Pd-promoted capsule catalyst.

Rice husks as a sustainable silica source for hierarchical flower-like metal silicate architectures assembled into ultrathin nanosheets for adsorption and catalysis

Metal silicates have attracted extensive interests due to their unique structure and promising properties in adsorption and catalysis. However, their applications were hampered by the complex and expensive synthesis. In this paper, three-dimensional (3D) hierarchical flower-like metal silicate, including magnesium silicate, zinc silicate, nickel silicate and cobalt silicate, were for the first time prepared by using rice husks as a sustainable silicon source. The flower-like morphology, interconnected ultrathin nanosheets structure and high specific surface area endowed them with versatile applications. Magnesium silicate was used as an adsorbent with the maximum adsorption capacities of 557.9, 381.3, and 482.8mg/g for Pb2+, tetracycline (TC), and UO22+, respectively. Ni nanoparticles/silica (Ni NPs/SiO2) exhibited high catalytic activity and good stability for 4-nitrophenol (4-NP) reduction within only ∼160s, which can be attributed to the ultra-small particle size (∼6.8nm), good dispersion and high loading capacity of Ni NPs. Considering the abundance and renewability of rice husks, metal silicate with complex architecture can be easily produced at a large scale and become a sustainable and reliable resource for multifunctional applications.

Silica is preferred over various single and mixed oxides as support for CO2-assisted cobalt-catalyzed oxidative dehydrogenation of ethane

Catalysts containing 4.5wt% cobalt supported on single oxides of SiO2, Al2O3, TiO2 and ZrO2 and on mixed ones of SiO2-Al2O3, SiO2-TiO2, SiO2-ZrO2 and TiO2-ZrO2 were produced in a single step by flame spray pyrolysis and tested in the CO2-assisted oxidative dehydrogenation of ethane in a continuous fixed-bed microreactor. Structural and chemical properties of the nonporous catalysts were characterized by nitrogen adsorption, XRD, HR-TEM, EDXS, NH3-TPD, H2-TPR, TGA, DRIFTS, XPS and Raman and UV–vis spectroscopy. Depending on the supporting oxides the reducibility of the cobalt species varied in a broad range, indicating vastly different interaction of the cobalt species with the oxidic support. For catalysts supported on Al2O3 and SiO2-Al2O3 no significant H2 consumption was observed up to 840°C, while ZrO2-supported CoOx was already reduced at T <500°C. The silica-supported catalysts showed a broad reduction peak at ∼780°C attributed to well dispersed CoOx embedded in the SiO2 matrix forming cobalt silicate, consistent with HR-TEM, XPS and UV–vis analyses. Among all catalysts, silica-supported cobalt showed the best catalytic performance under the test conditions used (700°C with CO2/C2H6=2.5). Admixing Al2O3, TiO2 and ZrO2 to SiO2 did not result in improved catalytic performance. Reducibility of the CoOx species as well as the strength and surface density of acidic sites were identified as crucial catalyst properties for optimal ethene yield. Control of the surface acidity seems particularly important to avoid undesired side reactions (cracking, coking) impairing activity and selectivity. Parametric sensitivity studies of the silica supported cobalt catalyst, including reaction temperature, CO2/C2H6 feed ratio and space velocity, revealed the important role of CO2. In the absence of CO2, only low C2H6 conversion was observed and change of the oxidant to O2 resulted in poorer catalytic performance.

Cobalt silicate hierarchical hollow spheres for lithium-ion batteries

In this paper, the synthesis of cobalt silicate novel hierarchical hollow spheres via a facile hydrothermal method is presented. With a unique hollow structure, the Co2SiO4 provides a large surface area, which can shorten the lithium ions diffusion length and effectively accommodate the volumetic variation during the lithiation/de-lithiation process. Serving as an anode material in lithium-ion battery application, the Co2SiO4 electrode demonstrates a high reversible specific capacity (first-cycle charge capacity of 948.6 mAh g−1 at 100 mA g−1), a cycling durability (specific capacity of 791.4 mAh g−1 after 100 cycles at 100 mA g−1), and a good rate capability (specific capacity of 349.4 mAh g−1 at 10 A g−1). The results indicate that the cobalt silicate hierarchical hollow sphere holds the potential applications in energy storage electrodes.

Synthesis of Transparent Amorphous Carbon Thin Films from Cellulose Powder in Rice Straw

The transparent amorphous carbon thin films (ACTF) were prepared through a batch acid spraying technique in the presence of cobalt silicate as a catalyst at low temperature between 30 and 45 \(^{\circ }\hbox {C}\). Hence, the catalyst was prepared using silica gel as a basic matrix and supporting material to produce ACTF. The produced active carbon was characterized using XRD, FTIR, and Raman spectrum. The high-resolution transmission electron microscope (HR-TEM) and thermogravimetric analysis were used to analyze the surface morphology and thermal stability of cellulose and ACTF, whereas the surface area was calculated using the standard iodine method. The results of Raman spectroscopy and TEM show the realization of ACTF suspension with highest constitutional order and the lowest number of layers with confirming of the succeed preparation of thin ACTF layers in thickness and average size of 1 and 100 mm, respectively. In addition, under these conditions, the activated carbons’ iodine value is 721.64 mg/g, and the yield ratio is 85.71 %.

Nitrous oxide decomposition over Co/SBA-15 catalysts: the influence of metal loading, cobalt precursor, and solvent effect

The influence of cobalt loading (10–50 wt-%Co), cobalt precursor, and solvent on the physico-chemical and catalytic properties of mesoporous Co/SBA-15 catalysts for the N2O decomposition reaction has been investigated. Catalysts were characterised by N2 adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), and temperature-programmed reduction (TPR). For Co/SBA-15 catalysts prepared from Co(II) nitrate, the dispersion decreased and the extent of cobalt reduction increased with cobalt loading. A maximum N2O conversion was found for the sample with ca. 30 wt-% Co loading. At similar cobalt loading (ca. 30 wt-%), a low dispersion and a stronger cobalt–support interaction leading to the formation of low reducible cobalt silicates was observed for Co/SBA-15 samples prepared from acetate precursors as compared to that derived from cobalt(II) nitrate, as evidenced by TPR. The former catalysts showed a low N2O decomposition activity. Moreover, at every Co loadings, the catalysts prepared in water exhibited much higher activities than those prepared in ethanol solvent, which could be related to the low reducibility of cobalt species in the latter catalysts. Finally, at comparable Co loading Co/SBA-15 catalysts (nitrate precursor) were more active than a Co/SiO2 and Co/Al2O3 sample.