Evolution of carbon structures in the pyrolysis of petroleum pitches

The present study focuses on the carbon structure analysis of hydrographene like materials produced during the pyrolysis of petroleum pitches under various experiment conditions and non-isothermal kinetics of pyrolysis of petroleum pitches. Non-isothermal kinetic studies of pyrolysis of the pitches based on the TGA measurements at different heating rates resulted that the average activation energy of the pyrolysis of pitch B (213.2 kJ/mol) was higher than that of the average activation energy of pitch A (185.7 kJ/mol) whereas the reaction orders of pitches A and B were 1.3 and 0.91, respectively. Experiments were carried out under an argon atmosphere at the temperature range of 500-1000±C for 30, 60 and 120 minutes in a tube furnace. FTIR, [1]H-NMR, and [13]C-NMR results showed that the aromatic structure of the hydrographenes were increasing with respect to increasing temperature as well as increasing time. Raman spectra results demonstrated the increase in orderness with increasing ID/IG ratio from 0.65 to 0.92 when the temperature of pitch A pyrolysis was increased from 500°C[degrees Celsius] to 900°C[degrees Celsius]. XRD patterns of the hydrographenes showed the crystallinity increased with increasing time and temperature. The calculated average numbers of graphene layers were 5 to 10 with respect to XRD patterns. The SEM images visualized the amorphous structure of hydrographenes that was highly rich in turbostratic structures. All the results of characterizations were consistent indicating the formation of highly amorphous hydrocarbon materials that contain turbostratic structures and higher heat treatments formations of aromatic structure with an increasing crystallinity and orderness. Highly amorphous hydrocarbon materials containing turbostratic structures were produced by two different types of pitches. Temperature seemed to be the dominating parameter of the pyrolysis reactions. As the pyrolysis temperature was increased aromatic structure formation was favored with an increasing crystallinity and orderness in the hydrographene materials

Preparation and characterization of modified polyether ether ketone (PEEK-WC) membranes for polymer assisted ultrafiltration of Cu2+ IONS from water

Membrane technology is one of the most important topics in today’s research for achieving metal removal and/or recovery from water. In this study, modified polyether ether ketone (PEEK-WC) membranes ranging from microfiltration to nanofiltration membranes depending on the coagulation bath, evaporation time and temperature were produced by phase inversion method. Produced asymmetric porous ultrafiltration membranes were preferred for PAUF processes. In the meantime, bonding conditions (pH and polymer/metal concentration) of various heavy metals (Cu2+, Ni2+, Co2+) with PEI were optimized. Optimum pH of 6 and 1:1 Cu2+:B-PEI (weight ratio) conditions were used to prepare feed solution for PAUF tests. In conclusion, a denser structure of PEEK-WC membranes, DW-120, corresponded to a higher rejection of Cu2+ (98%), although there was a sharp reduction in permeance. All membranes showed a constant permeance profile with respect to time. This strongly indicated that there was no effect of concentration polarization on the membranes. Also, both long-term and short-term stability (in means of flux and selectivity) of these membranes validated the reduction of fouling effect due to the chemical stabilility of PEEK-WC. In spite of the decrease in permeances, reusability and almost complete recovery (94.5%) of the used membranes make these membranes an attractive alternative for industrial applications. Specifically, almost full recovery of performance of PEEK-WC membranes, just by washing with water, makes them significant among commercially used membranes

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

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

Conversion of low-rank Kilyos coal to nitrogeneous fertilizers

The aim of this work is to convert the low-rank Kilyos coal to a material that could be used as a nitrogenous fertilizer. Incorporation of nitrogen into this Kilyos coal was accomplished by oxidative ammoniation, which was a two-step process involving oxidation with nitric acid followed by a treatment by ammonia. The nitrogen content of the raw coal increased from 0.8% to 8.3-9.3% after ammoniation process. Trace element concentrations in the nitro-coal, HA and OAC samples were within the acceptable ranges to be used as nitrogenous fertilizer. Therefore the oxy-ammoniated products could be considered as high-value fertilizers

Enhanced exfoliation technique for the separation of graphene nanosheets

Graphene sheets are carbon-based materials which combine exceptional electron conductivity, mechanical strength and optical transparency. Graphene nanosheets were fabricated by an enhanced, safer and mild technique in a shortened processing time. Samples were characterized by SEM, XRD, TGA, AFM and Raman Spectroscopy

Production of carbon nanotubes over Fe-FSM-16 catalytic material: effect of acetylene flow rate and CVD temperature

In this article, a high-yield synthesis of high-quality CNTs using Fe catalysts trapped within channels of Folded Sheet Mesoporous Materials, FSM-16 by Chemical Vapor Deposition CVD using acetylene as a hydrocarbon source is reported. The effect of reaction temperature and acetylene flow rate on the formation of CNTs was investigated. It was found that the yield, diameter and quality of CNTs synthesized strongly depend on reaction temperature during CVD. The resulting materials were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and thermogravimetric analysis (TGA). Our research found that carbon deposition, diameter and quality of the CNTs strongly depend on CVD temperature. However acetylene flow rate did not have any significant effect on diameter distribution. Raman measurement indicated that the synthesized products were MWCNTs. High-resolution transmission electron micrographs of samples reveal the multilayer sidewalls of individual MWCNTs with a diameter of 40 nm, in which hollow and tubal structures were observed

Production of carbon nanotubes over Fe-FSM-16 catalytic material: effect of acetylene flow rate and CVD temperature

In this article, a high-yield synthesis of high-quality CNTs using Fe catalysts trapped within channels of Folded Sheet Mesoporous Materials, FSM-16 by Chemical Vapor Deposition CVD using acetylene as a hydrocarbon source is reported. The effect of reaction temperature and acetylene flow rate on the formation of CNTs was investigated. It was found that the yield, diameter and quality of CNTs synthesized strongly depend on reaction temperature during CVD. The resulting materials were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and thermogravimetric analysis (TGA). Our research found that carbon deposition, diameter and quality of the CNTs strongly depend on CVD temperature. However acetylene flow rate did not have any significant effect on diameter distribution. Raman measurement indicated that the synthesized products were MWCNTs. High-resolution transmission electron micrographs of samples reveal the multilayer sidewalls of individual MWCNTs with a diameter of 40 nm, in which hollow and tubal structures were observed

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