Non-conventional feeds such as vacuum residue (VR) and heavy oils have shown an alternate source for the production of high value transportation fuels, as it is abundantly available. These feeds are ...of low quality due to presence of impurities like CCR, asphaltenes, sulfur, nitrogen and heavy metals. Several process technologies have been developed to upgrade these feeds through fixed-bed, moving-bed, ebullated-bed, slurry-phase reactor or a combination. Hydrocracking in slurry-phase type reactor is a prominent technology to convert low value feeds into high value transportation fuels and petrochemical products. Varieties of homogeneous and heterogeneous catalysts comparison are reviewed for hydrocracking of VR and heavy oils. Recent studies on hydrocracking reaction mechanisms are represented in this report. Choice of process technology is implemented by considering the feed properties, product demand and economic benefit as well as environmental concerns. This review addresses the most recent hydrocracking technologies, catalyst development and important issues related to conversion of non-conventional feeds.
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•From waste PET plastic, graphite was prepared through a facile method.•The PET-derived graphite exhibited a high degree of graphitization.•Graphene sheets were successfully obtained ...by exfoliating the PET-derived graphite.
The development of new technologies for converting waste plastics into value-added products is attracting widespread attention because of the global plastic waste crisis. In this study, we present a novel route for the upcycling of waste plastics, wherein synthetic graphite is prepared from a waste polyethylene-terephthalate (PET) bottle through a facile and scalable method. PET was successfully converted to graphite via a synthetic method of pyrolysis at 900 °C followed by boron-assisted catalytic graphitization at 2400 °C. This technique overcame the intrinsic non-graphitizable property of PET and yielded graphite showing high crystallinity with the maximum crystallite size of 20.9 nm in Lc and the d(002) spacing of 3.373 Å. In particular, it showed a much higher degree of graphitization (80.6%) than that (68.9%) derived from a well-known AR mesophase pitch (Mitsubishi). In addition, via a microwave-assisted liquid-phase exfoliation, the PET-derived graphite was successfully exfoliated as graphene sheets with the average lateral size of 410 nm. We expect that our work can guide the innovative upcycling of waste plastics to invaluable synthetic graphite, which has many potential applications such as anode materials in secondary batteries and fillers for carbon composites, and may serve as an alternative source for graphene production.
The correlation of the anisotropic texture and (002) the molecular stacking property of spinnable mesophase pitch (SMP) was closely examined. SMP was found to be a specific solution consisting of ...mesogenic and solvent components, and the mesogenic component was composed of a cluster unit of (002) stacked molecular sheets. The anisotropic texture of SMP was strongly correlated with the height of (002) molecular stacking. When the concentration ratio of the mesogenic component to the solvent component was higher than the threshold concentration, the SMP always had 100 vol% anisotropic texture and a similar or larger number of stacked (002) sheets compared with its mesogenic component in both the solid and molten states. The solvent component, in both lamellar and hexagonal phases, assisted orientation of mesogenic molecules and rearrangement of mesogenic cluster units, thereby inducing a higher degree of graphitization than that of the solvent-free mesophase pitch. A schematic phase model of SMP was proposed based on a lyotropic liquid crystalline system and a hierarchical domain model.
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Spinnable mesophase pitch precursor containing more than 98% mesophase content was successfully prepared from FCC-DO (fluid catalytic cracking-decant oil) without hydrogenation or catalytic reaction. ...The preparation method involved thermal condensation, vacuum treatment, and annealing treatment. Petroleum mesophase pitch-based carbon fibers are produced by melt spinning of pitch precursors, followed by stabilization and carbonization. The resulting carbon fiber exhibited good mechanical performances up to tensile strength of 2.1 GPa and tensile modulus of 212 GPa, with strain-to-failure higher than 1.0%. These properties ensuring that the automotive grade carbon fibers can be successfully prepared from FCC-DO derived petroleum mesophase pitches through the cost-competitive processes.
With the development of microelectronic devices having miniaturized and integrated electronic components, an efficient thermal management system with lightweight materials, which have outstanding ...thermal conductivity and processability, is becoming increasingly important. Recently, the use of polymer-based thermal management systems has attracted much interest due to the intrinsic excellent properties of the polymer, such as the high flexibility, low cost, electrical insulation, and excellent processability. However, most polymers possess low thermal conductivity, which limits the thermal management applications of them. To address the low thermal conduction of the polymer materials, many kinds of thermally conductive fillers have been studied, and the carbon-based polymer composite is regarded as one of the most promising materials for the thermal management of the electric and electronic devices. In addition, the next generation electronic devices require composite materials with various additional functions such as flexibility, low density, electrical insulation, and oriented heat conduction, as well as ultrahigh thermal conductivity. In this review, we introduce the latest papers on thermally conductive polymer composites based on carbon fillers with sophisticated structures to meet the above requirements. The topic of this review paper consists of the following four contents. First, we introduce the design of a continuous three-dimensional network structure of carbon fillers to reduce the thermal resistance between the filler-matrix interface and individual filler particles. Second, we discuss various methods of suppressing the electrical conductivity of carbon fillers in order to manufacture the polymer composites that meet both the electrical insulation and thermal conductivity. Third, we describe a strategy for the vertical alignment of carbon fillers to improve the through-plane thermal conductivity of the polymer composite. Finally, we briefly mention the durability of the thermal conductivity performance of the carbon-based composites. This review presents key technologies for a thermal management system of next-generation electronic devices.
Petroleum residues are produced as by-products of petroleum refining. Recently, various effective non-fuel uses of petroleum residues have been considered toward a carbon-neutral society. Pyrolysis ...fuel oil (PFO) is one of the petroleum residues. Advanced utilization of PFO for future non-combustion applications is required. In this study, Mesophase pitch-based carbon fibers (MPCF) were successfully produced from PFO. Spinnable mesophase pitch (SMP), a precursor of MPCF, was prepared using PFO as a raw material through the pressurized heat treatment at 420°C-430 °C. PFO is from the naphtha catalytic cracking process for ethylene production and is mainly composed of 2–4 condensed polycyclic aromatic hydrocarbons (PAHs). The high temperature pressurized heat treatment could result in the PFO-derived SMPs with yield of 23.0 wt% and excellent spinnability. On the other hand, without pressurized heat treatment, the yield was 8.5 wt%. This indicates that pressurized heat treatment significantly contributed to the yield improvement. In addition, the preference for the conversion of PFO molecules into highly condensed PAHs via cata-condensation during pressurized heat treatment at 420°C-430 °C was observed, which may be the main reason for the high yield and excellent spinnability of the resulting SMPs. As a result, the obtained PFO-derived SMPs though the such high-temperature pressurized heat treatment provided the typical radial-random transversal textures and general mechanical performances of MPCF: The tensile strength and Young's modulus of the PFO-derived MPCF graphitized at 2400 °C showed high values of 1.9–2.7 GPa and 554–635 GPa, respectively.
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Textiles represent an ideal platform for next-generation electronic devices owing to their flexibility, stretchability, wearability, and biocompatibility. Herein, we present highly conductive and ...flexible electrodes based on electrochemically exfoliated graphene (EEG) and cotton textile; these electrodes are fabricated via hot pressing to be used as sensing materials in piezoresistive-type pressure sensors. The sheet resistance and microstructure of the electrodes can be controlled by varying the surface density of the EEG on the textile substrate. The optimized EEG/textile electrodes exhibited a minimum sheet resistance ( R s ) of 1.3 Ω sq −1 as well as high flexibility and durability during a 1000-cycle bending test. The pressure sensors were fabricated by assembling two EEG/textile electrodes, with each electrode acting as a pressure-sensing material; the sensors exhibited a maximum pressure sensitivity of ∼0.16 kPa −1 , a wide range of linear sensitivity (up to 100 kPa), a fast response of ∼373 ms, and reproducible performance over 10 000 cycles of pressure loading and unloading. These sensors also functioned effectively as bending-motion, wrist-pulse, and step-motion sensors, as well as on/off-type pressure sensors. Hence, the developed EEG/textile electrodes have the potential to be used in textile electronics and next-generation wearable devices.
Coating building envelopes with a passive daytime radiative cooling (PDRC) material has attracted enormous attention as an alternative cooling technique with minimal energy consumption and carbon ...footprint. Despite the exceptional performance and scalability of porous polymer coating (PPC), achieving consistent performance over a wide range of drying environments remains a major challenge for its commercialization as a radiative cooling paint. Herein, we demonstrate the humidity vulnerability of PPC during the drying process and propose a simple strategy to greatly mitigate the issue. Specifically, we find that the solar reflectance of the PPC rapidly decreases with increasing humidity from 30% RH, and the PPC completely losses its PDRC ability at 45% RH and even become a solar-heating material at higher humidity. However, by adding a small amount of polymer reinforcement to the PPC, it maintains its PDRC performance up to 60% RH, resulting in a 950% increase in estimated areal coverage compared to PPC in the United States. This study sheds light on a crucial consistency issue that has thus far been rarely addressed, and offers engineering guidance to handle this fundamental threat to the development of dependable PDRC paint for industrial applications.
The pitch impregnation process enhances the properties of synthetic graphite by optimizing their physicalstructure of channels and pores generated during heat treatment. Synthesizing a ...well-balancedmolecular structure of impregnation pitch (IP) is essential for facilitating impregnation and obtaining ahigh carbonization yield. However, achieving this delicate balance is exceptionally challenging due tothe inherent trade-off relationship between these factors. To resolve this issue, we propose a stepwisepitch synthesis recipe and the molecular weight distribution (MWD) tailoring, specifically applied tothe petroleum IP from pyrolysis fuel oil (PFO). The stepwise recipe is composed of a pressurized pretreatmentstep applied to increase production yield and coking value, followed by a thermal polymerizationstep. The tailoring process is systematically designed to obtain the best performing petroleum IP by effectivelyremoving impregnation inhibitor. Our study highlights the potential benefits of using petroleumbasedpitch for impregnation processes in manufacturing of artificial graphite. The impregnation performancewas enhanced by 6.7% and carbonation yield was notably improved by 16.2% relative to the coaltarderived commercial IP. Our results show that tailoring the molecular weight distribution (MWD) ofthe impregnating pitch enhances impregnation performance by 1.88% compared to the raw IP. KCI Citation Count: 0
The development of miniaturized and highly integrated microelectronic products has motivated the current importance of synthesizing heat-dissipation materials with high thermal conductivity and ...excellent electrical insulation. Although graphene is attractive for improving the thermal conductivity of polymers owing to its high aspect ratio and outstanding thermal conductivity, it significantly deteriorates electrical insulation capability, limiting its practical application in polymer composites for thermal management of electronics and systems. In this work, we used planetary ball milling to synthesize a hybrid powder Al@EEG consisting of electrochemically exfoliated graphene (EEG) and surface-passivated aluminum particles. This ball milling prevents contact between graphene sheets by uniformly dispersing EEG in Al matrices without the conventional surface modification or chemical treatment process of graphene, thereby imparting thermal conductivity and electrical insulation to the hybrid powder. The resulting epoxy composite, containing 35- wt% Al@EEG hybrid, retains an electrical resistance of 1014 Ω·cm or higher and a thermal conductivity of 1.43 W m−1 K−1, which is 499% higher than that of neat epoxy. The as-designed material points the way to polymer-based, thermally conductive, electrically insulating composites for various electronic components such as printed circuit boards and light-emitting diode driver cases.
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