Preparation and characterization of mesoporous carbons using a Turkish natural zeolitic template/furfuryl alcohol system

The template carbonization method was utilized for the production of mesoporous carbons using a Turkish natural zeolite as a template. The major carbon precursor used was furfuryl alcohol. Furfuryl alcohol was polymerized and carbonized between 700 °C and 1000 °C in the channels of the natural zeolite. The structure of the zeolite template and carbons were investigated by surface analysis techniques, scanning electron microscopy, 13C NMR and FTIR spectrometry, and powder X-ray diffraction. At the micrometer level, the carbon material templated with the natural zeolite had the same morphology as the zeolite. The porous carbon samples contained 9199% C and minor amounts of oxygen. While the surface area of the carbon produced without templation was only 18 m2/g, the surface area of the carbons produced within the template was found to be in the range of 400800 m2/g. Average pore diameter of the porous carbons was measured as ca. 510 nm, demonstrating presence of mesoporous framework in the carbons. The 13C NMR and FTIR spectra revealed that the carbons produced in the carbonization range of 7001000 °C contained some hydrogen and oxygen containing functional groups. The XRD results put forward indications to the presence of turbostratic structures and preservation of the structural regularity of the zeolite over extended distances in the carbons

Biogasification of soma lignite by microorganisms

The main scopes of this study are to analyze the bacterial activity on the coal samples which come from Soma basin in Turkey and investigation of the bacterial gas production of these samples. For that purpose, characterization of the coal samples was performed by using FTIR, STA, BET, SAM and ICP

Structural aspects of AlPO4-5 zeotypes synthesized by microwave-hydrothermal process. 1. Effect of heating time and microwave power

AlPO4-5 with AFI structure containing 12-membered rings was prepared using the aluminum isopropoxide precursor as a source of alumina and TEA as the structure directing agent via microwave technique. The influence of microwave power and heating time on the dimensions of AlPO4-5 crystals formed in the system Al2O3:P2O5:(C2H5)3N (or (C3H7)3N):H2O:HF has been studied systematically. It was found that the morphology of the AlPO4-5 depended on the microwave power and heating time. Several mechanisms of fast crystallization existed in the microwave radiation, due to increased dissolution of the gel by lonely water molecules in almost temperature gradient-free and convection-free in situ heating

Use of Pd/activated carbon fiber catalyst to dehydrogenate cyclohexane

In this work, activated carbon fibers (ACFs) were prepared from polyacrylonitrile fibers, Pd catalyst was loaded onto the ACFs. The BET surface areas noted before activation were in the range of 120-140 m2/g. Activation of the fibers with carbon dioxide increased the surface areas of the fibers to about 150-190 m2/g. Diameters of metallic Pd particles loaded along the fibers ranged from 50 nm to 100 nm. The shape of the Pd particles was generally spherical albeit some non-spherical Pd particles were also noted. The catalytic activity of the Pd/ACF system in dehydrogenating cyclohexane at 350oC under liquid-phase conditions was investigated. Utilizing the Pd/ACF system in the micro-autoclave of a differential scanning calorimetric system was described for the liquid-phase catalytic dehydrogenation of cyclohexane. The DSC thermogram of the non-catalytic system yielded fewer endothermic events compared to the catalytic dehydrogenation of cyclohexane in the presence of Pd/ACF. The dehydrogenation of cyclohexane at 350oC was a first-order reaction with a rate constant, k = 3.5 x 10-4 s-1. GC-MS analyses of the products of catalytic dehydrogenation revealed a wide distribution of saturated and unsaturated hydrocarbons that were not present in the corresponding non-catalytic experiment. The presence of high molecular weight products could be explained by the recombination of carbon radicals during reaction

Utilization of multiple graphene layers in fuel cells. 1. An improved technique for the exfoliation of graphene-based nanosheets from graphite

An improved, safer and mild method was proposed for the exfoliation of graphene like sheets from graphite to be used in fuel cells. The major aim in the proposed method is to reduce the number of layers in the graphite material and to produce large quantities of graphene bundles to be used as catalyst support in polymer electrolyte membrane fuel cells. Graphite oxide was prepared using potassium dichromate/sulfuric acid as oxidant and acetic anhydride as intercalating agent. The oxidation process seemed to create expanded and leafy structures of graphite oxide layers. Heat treatment of samples led to the thermal decomposition of acetic anhydride into carbondioxide and water vapor which further swelled the layered graphitic structure. Sonication of graphite oxide samples created more separated structures. Morphology of the sonicated graphite oxide samples exhibited expanded the layer structures and formed some tullelike translucent and crumpled graphite oxide sheets. The mild procedure applied was capable of reducing the average number of graphene sheets from 86 in the raw graphite to nine in graphene-based nanosheets. Raman spectroscopy analysis showed the significant reduction in size of the in-plane sp2 domains of graphene nanosheets obtained after the reduction of graphite oxide

Removal of Boron from aqueous solutions by adsorption using fly ash, zeolite and demineralized lignite

In the present study for the purpose of removal of boron from water by adsorption using adsorbents like fly ash, natural zeolite and demineralized lignite was investigated. Boron in water was removed with fly ash, zeolite and demineralized lignite with different capacities. 94% boron was removed using fly ash. Batch experiments were conducted to test removal capacity, to obtain adsorption isotherms, thermodynamic and kinetic parameters. Boron removal by all adsorbents was affected by pH of solution; maximum adsorption was achieved at pH 10. Adsorption of boron on fly ash was investigated by Langmuir, Freundlich, Dubinin-Radushkevich models. Standard entropy and enthalpy changes of adsorption of boron on fly ash were, =S0 = -0.69 kJ/mol K and =H0 = -215.34 kJ/mol, respectively. The negative value of S0 indicated decreased randomness at the solid/solution interface during the adsorption boron on the fly ash sample. Negative values of H0 showed the exothermic nature of the process. The negative values of G0 implied that the adsorption of boron on fly ash samples was spontaneous. Adsorption of boron on fly ash occurred with a pseudo-second order kinetic model, intraparticle diffusion of boron species had also some effect in adsorption kinetics

Carbon nanotube production over MCM-41 type catalytic materials via CVD method

We investigate the effects of mesoporous catalyst synthesis methods over carbon nanotube (CNT) production. Metal incorporated mesoporous catalysts were synthesized by two different microwave assisted synthesis methods. In the first method, MCM-41 mesoporous materials were synthesized with microwave radiation and then metal was impregnated into these as-synthesized MCM-41 samples. In the second method metal was added into the raw materials directly and then the mixture was treated in the microwave oven. The catalyst were tested in CVD for CNT production

Structural characterization of semicokes produced from the pyrolysis of petroleum pitches

Semicokes obtained from the pyrolysis of petroleum pitches are important materials that are used in the manufacture of many carbonaceous products. Therefore, new structural information of the semi-cokes will extend their utilization. The structural analysis of anisotropic semicokes of the pyrolysis of petroleum pitches obtained under various experimental conditions of temperature and time was investigated. The overall objective is to provide further detailed information of factors which influence formation of anisotropy or turbostratic structures in resultant semicokes. Experiments were carried out under an argon atmosphere at the temperature range of 500-1000 degrees C for 30, 60 and 120 min in a tube furnace. FTIR, H-1-NMR, and C-13 NMR results showed that the aromatic structure of the semicokes was increasing with respect to increasing temperature as well as increasing time. Aromaticity of the semicokes was calculated as 0.54 and 0.64, for Pitch A at 500 degrees C after 120 min, and Pitch B at 600 degrees C after 120 min, respectively. The intensity ratio between Raman "D" and "G" peaks, I-D/I-G (commonly used to characterize disorder in graphene structures) was observed to increase approximately linearly from 0.65 to 0.92 when the pyrolysis temperature of Pitch A was increased from 500 degrees C to 900 degrees C. XRD patterns of the semicokes showed the formation of some crystalline material with time and temperature. The average number of layers, calculated by the Debye-Scherer technique using the XRD patterns of the semicokes, was between 5 and 10. SEM images of the semicokes indicated the presence of turbostratic structures. All the results of characterizations were consistent and indicated the formation of highly amorphous hydrocarbon materials that contain turbostratic structures. Treatments at higher temperatures increased formations of aromatic structure with increased crystallinity. Temperature seemed to be the dominating parameter of the pyrolysis reactions. As the pyrolysis temperature was increased, aromatic structure formation was favored with increased crystallinity in the semicokes. We expect that findings of the present work will open new uses for the anisotropic semicokes obtained from petroleum pitches. The pitches can be widely applied to the templating synthesis of carbon nanostructures and other carbon nanomaterials

Copper and nickel supported FSM-16 molecular sieves for carbon nanotube production

FSM-16, Cu-FSM-16 and Ni-FSM-16 type folded sheet mesoporous materials has been synthesized by using kanemite and hexadecyltrimethylammonium bromide as a template. 1, 5, 10 wt % Cu and Ni were loaded by simple impregnation method. The X-ray diffraction and N2 sorption characteristics show that the resultant materials has uniform pore structure with hexagonal well ordered arrangement. BET surface area, pore volume nd pore diameters were decreased as the metal loading increased. Carbon nanotubes (CNTs) have been synthesized within the metal trapped channels of the FSM-16 via chemical vapor deposition using acetylene as the hydrocarbon source. The resultant nanotubes were compared under similar reaction conditions and they were characterized by scanning electron microscopy (SEM), Raman Spectroscopy, AFM and TGA

Graphene nanosheet and carbon nanotube based nanocomposites as an electrode support for fuel cells

An electrode support material in fuel cells has great influence on catalyst dispersion, charge transport, and stabilization of the catalyst particles. Graphene and carbon nanotubes have been considered as a fuel cell electrode material due to their high specific surface area, exceptional electronic and mechanical properties. The mesopores in graphene nanosheets and carbon nanotube electrodes are interconnected, providing a continuous charge distribution that uses nearly all of the available surface area. In present work, for the production of advanced type of electrode materials, the distinguished properties of graphene nanosheets and multi walled carbon nanotubes were combined with the structural properties of conducting polymers (polypyrrole) by the incorporation of graphene and carbon nanotubes into a polymer matrix. Graphene nanosheets were exfoliated from graphite by a mild chemical treatment including graphite oxidation using sulphuric acid and potassium dichromate, ultrasonic treatment, and chemical reduction by hydroquinone. Pyrrole was coated on graphene nanosheets and carbon nanotubes by in situ polymerization by different feeding ratios. Graphene nanosheet and carbon nanotube based nanocomposites were compared according to their structural properties, thermal stabilities and electrical conductivities. Samples were analyzed in detail by SEM, XRD, TGA, AFM, TEM, FTIR and Raman Spectroscopy