Mesophase Development Research Articles

Saturate Acts as Both a "Lubricant" and an "Activator" during the Conversion Process of Mesophase in Fluid Catalytic Cracking Slurry Oil.

Saturate (Sa), the lightest component in fluid catalytic cracking (FCC) slurry oil, exhibits a poorly understood influence on the formation and development of mesophase, thereby constraining the production of premium-quality mesophase pitch. To address this issue, Sa is isolated from FCC slurry oil, and its concentration is modulated to investigate its impact on the formation and development of mesophase. The results indicate that Sa contains a high concentration of long alkane side chains and naphthenic structures, which render it an effective "lubricant" and "activator" within the reaction system. The addition of a small amount of Sa (≤5 wt %) maintains a low viscosity state of the reaction system, further facilitating the migration of aromatic molecules and promoting mesophase formation. It is crucial to note that excessive amounts of Sa (>10 wt %) significantly reduce the aromaticity and reactivity of the reaction system, further delaying the formation of mesophase. The reaction system exhibits moderate aromaticity and reactivity with low viscosity at 10 wt % Sa, leading to the formation of mesophase pitch with a moderate softening point (270 °C) and a wide-area optical texture (anisotropy length >60 μm, width >10 μm) within a short time of 6 h. This work establishes a robust theoretical foundation for producing premium-quality mesophase pitch through the regulation of raw material components.

Magnetic Supramolecular Spherical Arrays: Direct Formation of Micellar Cubic Mesophase by Lanthanide Metallomesogens with 7-Coordination Geometry.

Here, an unprecedented phenomenon in which 7-coordinate lanthanide metallomesogens, which align via hydrogen bonds mediated by coordinated H2O molecules, form micellar cubic mesophases at room temperature, creating body-centered cubic (BCC)-type supramolecular spherical arrays, is reported. The results of experiments and molecular dynamics simulations reveal that spherical assemblies of three complexes surrounded by an amorphous alkyl domain spontaneously align in an energetically stable orientation to form the BCC structure. This phenomenon differs greatly from the conventional self-assembling behavior of 6-coordinated metallomesogens, which form columnar assemblies due to strong intermolecular interactions. Since the magnetic and luminescent properties of different lanthanides vary, adding arbitrary functions to spherical arrays is possible by selecting suitable lanthanides to be used. The method developed in this study using 7-coordinate lanthanide metallomesogens as building blocks is expected to lead to the rational development of micellar cubic mesophases.

Terminal methylene biphenyl derived coumarin Schiff base-esters: Synthesis, mesomorphic behaviour and DFT investigations

In the present investigation new unsymmetrical coumarin-methylene biphenyl MBPCE-(2–16) mesogens were designed and synthesized. Methylene biphenyl end group at one end of molecules have been linked to the 7-alkyloxy substituted coumarin core through imine and ester mesogenic connecting units. The structures of new hybrids have been elucidated employing different analytical techniques including FT-IR, 1H NMR, 13C NMR, Mass & CHN elemental analysis. New molecules have been investigated for their mesomorphic behaviour using DSC (Measurement of transition temperature and enthalpy associated) and POM (Texture study) techniques and the existence of mesophase was established by VT-XRD analysis. Compounds with n = 2 (-OC2H5) to n = 7 (-OC7H15) chain length exhibited enantiotropic nematic mesophase with good thermal stability. As the chain length increases, compounds from n = 8 (-OC8H17) and n = 10 (-OC10H21) displayed enantiotropic nematic as well as smectic-A mesophase whereas compound with n = 12 (-OC12H25) showed only interdigitated SmA phase. Next two members of the series failed to show any mesomorphism. The commencement of SmA phase and disappearance of nematic could be attributed to more layer arrangement with increased van der waals interactions. The density functional theory (DFT) calculations were employed to complement the experimental results concerning the mesomorphic behaviour. Development of smectic phase could be due to the augmentation in the area of the intermolecular interaction which increases the degree of molecular packing. Conversely, it was discovered that higher polarizability leads to lower nematic thermal stability because it strengthens parallel intermolecular interactions, which promotes a higher degree of molecular order while reducing the development of lower-order nematic mesophase.

Influence of two asphaltenes on the formation and development of mesophase in fluid catalytic cracking (FCC) slurry oil

Asphaltene constitutes the heaviest component in fluid catalytic cracking (FCC) slurry oil. Mesophase pitch are prepared from FCC slurry oil by adding two asphaltenes (CL-As/JB-As) with distinct structure, and the influence of asphaltenes on the formation of mesophase is investigated. The findings suggest that an addition of CL-As within the range of 0–20 wt% is advantageous for the development and formation of mesophase. The addition of JB-As less than 1 wt% facilitates the formation and development of mesophase, while the opposite is observed with JB-As greater than 1 wt%. This is due to the light fraction of JB-As (JB-As-L), which is similar to CL-As and possesses appropriate concentrations of reactive sites that promote the formation of mesophase. However, the prevalence of alkane-branched chains is most densely concentrated in the heavy fraction of JB-As (JB-As-H), which leads to an excessive concentration of reactive sites. The predominance of JB-As-H causes an increase of the system's viscosity in the early stage so that the collision of polycyclic aromatic hydrocarbon macromolecules is reduced and the formation of the mesophase is postponed eventually. This provides a profound understanding of the preparation of high-quality mesophase pitch by regulating the properties of raw materials.

Influence of resin on the formation and development of mesophase in fluid catalytic cracking (FCC) slurry oil

Resin is one of the key components of fluid catalytic cracking slurry oil which is the raw material to form high-quality mesophase pitch. The effect of resin variations on the formation of mesophase was investigated in this paper. The results showed when the resin addition was from 0 to 20 wt%, the formation rate of mesophase remained basically invariable, but it was beneficial to the development of mesophase pitch with higher order degree. However, excessive additions of resin (>20 wt%) sharply accelerated the formation of mesophase due to the high concentration of reactive sites in the system, which shortened the time to form pitch with mesophase content close to 100%, adversely it led to the generation of mesophase pitch with lower order degree. In addition, the approximate molecular structure model of resin was constructed by various characterization methods. The aromatic ring skeleton of resin was dominated by 3–4 ring aromatic hydrocarbons. Resin also possessed structural features such as higher aromaticity, higher N and S content, larger molecular size, longer branched chains, more cyclic alkane structures and methylene bridges, and higher concentration of reactive sites than FCC-exR. Furthermore, an explanation of the effect of resin on the formation and development of mesophase with respect to the molecular structure characteristics was presumed. This work has important implications for regulating the raw material properties of FCC slurry oil and the preparation of high-quality mesophase pitch.

Texture development of mesophase in reservoir pyrobitumen and the temperature-pressure converting of the gas reservoir in the Chuanzhong Uplift, Southwestern China

The Neoproterozoic-Lower Paleozoic dolostone gas reservoirs in the Chuanzhong Uplift in Southwestern China contain the mesophase pyrobitumen (pyrobitumen with mesophase). The mesophase in the pyrobitumen is mostly composed of a mixture of condensed macromolecule polycyclic aromatic hydrocarbons (PAH), and has been mostly converted to various grain, flow, and domain textures. The volcanic activity nearby the Chuanzhong Uplift may have generated very hot (over 300 °C) hydrothermal fluid, with migration of the fluid into the dolostone reservoir transforming the hydrocarbons in the reservoir into an anisotropic carbon by-product, which formed under high temperature and pressure conditions; over 300 °C and 200 MPa according to fluid inclusion analysis. The high temperature-pressure in reservoir was caused by sudden devolatilization of the hydrocarbons due to hydrothermal heating, which formed the unusual texture of the mesophase. The elliptical mesophase grains (EG), the honeycomb structure of pyrobitumen, and the occurrence of polarized classes of mesophase in single pyrobitumen deposits are all unusual textures. This study investigates the texture development of this pressure-affected pyrobitumen. Observation and study of the mesophase suggest that the class of mesophase in pyrobitumen is determined by temperature, while pressure (assessed from associated fluid inclusions) significantly affected the texture. Analysis of the texture of the pyrobitumen in conjunction with previous thermometry results from methane inclusions suggests that the high class mesophase of the pyrobitumen could be applied as a temperature indicator for geological conditions. Furthermore, the unusual textures of the pyrobitumen including elliptical mesophase grains (EG), the honeycomb structure of pyrobitumen, and the occurrence of polarized classes of mesophase in single pyrobitumen could reflect the abnormal high formation pressure.

Effects of olefinic compounds on the thermal transformation for FCC slurry oil: Evolution pattern and mechanism

FCC decant oil was always used as the raw material for the preparation of high-value-added carbonaceous materials. There is little disagreement that the free radical mechanism induces thermal polymerization reactions between reactant molecules and intermediate species, which leads to the formation of carbonaceous mesophase in the early stage of carbonization. Olefinic hydrocarbons were recently found to be widely distributed in FCC decant oil in our previous research, and these chemically active compounds usually possess weak π-bonds in molecules and thus potentially form free radicals easily, which may impact the carbonization performance dramatically. This research investigated the effects of olefinic compounds on the preparation of needle coke from FCC decant oil, as well as the corresponding mechanism in depth combined with the evolution pattern of the intermediate species during liquid carbonization. ESR analyses were adopted to evaluate the variation of the concentration of stable free radicals. Stable free radical concentration varied greatly in diverse polymerizing systems along with the carbonization process. Olefin showed a significant effect on the stable free radical concentration during carbonization. The stable free radical concentration of the polymerizing system derived from FCC decant oil was 3.32 × 1020 spins/g when the reaction time was 4 h. But with 3 wt% addition of 2-vinylnaphthalene and squalene in FCC decant oil, the stable free radical concentration increased to 2.14 × 1021 spins/g and 1.33 × 1021 spins/g, respectively, with the same reaction time. Meanwhile, the olefins conjugated with aromatic rings shown more obvious effect on the generation of free radicals. Olefinic compounds can lead to a high generation rate of free radicals and significantly high stable free radical concentration in the polymerizing system which then promote the formation of disordered carbon materials. Besides, plenty of fine particles appeared between mesophase spheres with the addition of olefinic hydrocarbons, and then impeded the coalescence between mesophase spheres. Effect mechanism for olefin on the development of carbonaceous mesophase was proposed accordingly. In sum, the content of olefinic compounds in raw materials should be limited for reaching the requirements of the synthesis of carbon materials with superior structures, in which the content of olefinic compounds should be less than 1 wt% at least based on the research in this paper.

Carbonization characteristics of ethylene tar narrow fractions

In this study, the feasibility of using ethylene tar (ET) as raw material for needle coke production was investigated. The basic properties, structural compositions, and thermal stability of ethylene tar and its narrow fractions were studied by elemental analysis, Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR), the coke induction period, and simulation of thermal stability of coking feed. The properties of the products were analyzed by a polarized light microscope, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results showed that the content of asphaltenes was up to 22.04% in ET, and the thermal stability was poor due to the high content of olefin and other thermally sensitive components. Thus, the coke induction period of ET was only 34 min. After distillation, narrow fractions had no asphaltenes and a low quantity of heat-sensitive components, resulting in improved fraction thermal stability with coke induction period of more than 55 min. Due to its narrow molecular distribution and low content of heat-sensitive components of narrow fractions, the semi-cokes formed from narrow fractions possessed better anisotropic and microcrystalline structures than those formed from the ET. Compared with one-stage carbonization, the two-stage carbonization was more conducive to the coalescence, development, and orientation of mesophase, leading to the formation of a fibrous wide-area streamline structure. The needle coke prepared from the fraction of ET-C had a lower thermal expansion coefficient (CTE), as low as 2.49×10−6 °C−1, meeting the CTE requirement of needle coke.

Kinetics of various hydrocarbon groups formation in distillates obtained during the production of needle coke via the delayed coking of decantoil

Carbon-graphite materials based on needle coke are fundamentally important for the development of related industries worldwide. This paper presents the study results of two types of decantoil coking distillates from the FCC plant, obtained in a laboratory simulation to produce petroleum needle coke. During coking, distillates were sampled by cut fractions at formation temperatures of 410–440, 440–470, 470–500, 500–505 °C. The hydrocarbon composition of the original decantoils and obtained cut fractions of the coking distillates were analysed by GC–MS. The selection of short-boiling-range products and analysis of their hydrocarbon composition allowed to estimate indirectly the stages of mesophase development and to determine the narrow temperature interval at which its most active development occurs. For the two types of decantoils this temperature interval is different (for D2 − 440–470 °C, for D1 − 470–500 °C). This phenomenon allows us to effectively determine the regime parameters of the delayed coking process for needle coke production. The formation kinetics (effective activation energy and pre-exponential factor) of different groups hydrocarbons, including paraffin-naphthenic, unsaturated, aromatic (mono-, bi- and polycyclic) for the first time was determined using the model-free Friedman isoconversion method. The obtained coefficients of determination are close to 0.9–1.

Influence of Resin Variations on the Formation and Development of Mesophase in Fluid Catalytic Cracking (Fcc) Slurry Oil

Influence of Resin Variations on the Formation and Development of Mesophase in Fluid Catalytic Cracking (Fcc) Slurry Oil

Molecular Engineering for the Development of a Discotic Nematic Mesophase and Solid-State Emitter in Deep-Blue OLEDs.

A unique strategy for the attainment of a discotic nematic (ND) mesophase is reported consisting of a central benzene core to which are attached two 4-alkylphenyl and two 4-pentylbiphenyl moieties diagonally via alkynyl linkers. The rotational nature and incompatibility of unequal phenylethynyl units led to the disruption of π-π interactions within cores that aids to the realization of ND phase and favors high solid-state emission. When used in OLEDs, compounds act as an efficient solid-state pure deep-blue emitter with Commission Internationale de L'Eclairage (CIEx,y) coordinates of (0.16, 0.07).

Preparation of mesophase carbon microbeads from fluidized catalytic cracking residue oil: The effect of active structures on their coalescence

Mesophase carbon microbeads (MCMBs) were synthesized by thermal polycondensation with fluidized catalytic cracking residue oil (FRO) as the feedstock. The evolution features of functional groups of the residual oils and the residual solid products from thermal polymerization were analyzed, and the effect of olefinic compounds on the coalescence between mesophase spheres was investigated in depth. The results showed that the olefin contents of residual oil, heptane-soluble, and heptane-insoluble/toluene-soluble decreased simultaneously as the reaction proceeded while that of toluene-insoluble increased, indicating that the olefins in the solvent phase could not only provide molecule sources for the development of carbonaceous mesophase but also directly assemble into the insoluble mesogens. More importantly, the involvement of olefins caused a sharp increase of the system viscosity, making it difficult for the mesophase spheres to completely coalesce into regular large ones after cohering, leading to the apparent deformation. In contrast, catalytic hydrotreatment can saturate olefinic species and enhance the hydrogen transfer ability of FRO to further avoid the induction effect of olefins, slow down the mesophase development, reduce the system viscosity, and consequently avoid the deformation of mesophase spheres.

Rapid Fabrication by Lyotropic Self-Assembly of Thin Nanofiltration Membranes with Uniform 1 Nanometer Pores.

Nanostructured materials with precisely defined and water-bicontinuous 1-nm-scale pores are highly sought after as advanced materials for next-generation nanofiltration membranes. While several self-assembled systems appear to satisfy this need, straightforward fabrication of such materials as submicron films with high-fidelity retention of their ordered nanostructure represents a nontrivial challenge. We report the development of a lyotropic liquid crystal mesophase that addresses the aforementioned issue. Films as thin as ∼200 nm are prepared on conventional support membranes using solution-based methods. Within these films, the system is composed of a hexagonally ordered array of ∼3 nm diameter cylinders of cross-linked polymer, embedded in an aqueous medium. The cylinders are uniformly oriented in the plane of the film, providing a transport-limiting dimension of ∼1 nm, associated with the space between the outer surfaces of nearest-neighbor cylinders. These membranes exhibit molecular weight cutoffs of ∼300 Da for organic solutes and are effective in rejecting dissolved salts, and in particular, divalent species, while exhibiting water permeabilities that rival or exceed current state-of-the-art commercial nanofiltration membranes. These materials have the ability to address a broad range of nanofiltration applications, while structure-property considerations suggest several avenues for potential performance improvements.

Sequential pretreatments of an FCC slurry oil sample for preparation of feedstocks for high-value solid carbon materials

FCC slurry oil (SO) is an important and yield-rich by-product of the FCC process, which can be regarded as the raw material of high-value-added carbonaceous products due to its abundant concentration of aromatic components, but essential pretreatments and purifications for SO are required before carbonization to eliminate the adverse factors. Appropriate sequential pretreatments aimed at achieving the high-value utilization of SO have been developed, and two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H NMR, 13C NMR) were implemented for the systematical properties analyses of SO and its derivatives after sequential pretreatments. Polarized-light microscope, scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to evaluate the microstructures and microcrystal parameters of intermediate species and final products during carbonization. Through the varying degrees of sequential pretreatments, the comprehensive properties of feedstocks were improved gradually which further led to the diverse development of carbonaceous mesophase at the early stage of carbonization. Furthermore, ordinary or superior needle coke can be synthesized from the obtained oil samples during sequential pretreatments. The synthesized needle coke had suitable performance for the application in anode material of lithium-ion batteries.

Modified effect on properties of mesophase pitch prepared from various two-stage thermotreatments of FCC decant oil

The comparative study of different two-stage heat treatments was conducted to illustrate the modified effects on improving yield and spinnability of mesophase pitch. In such two-stage thermotreatments, a pressured condensation is employed to involve low-molecular-weight species into the formation of mesogens, thereby increasing pitch yields. Subsequently, vacuum polymerization could contribute to rapid development of mesophase and then reduce the residence time. The results indicate that the short duration could decrease occurrence of the intramolecular aromatization and intermolecular polymerization reactions that are readily induced by elimination of α-methyl and dehyroaromatization of naphthenic rings during the later stage of heat treatment. Consequently, the formed semi-rigid molecules in QS sub-fraction (i.e., fusible component) are seldom transformed into rigid ones mainly constituting QI sub-fraction (i.e., infusible component). Ultimately, sufficient QS sub-fraction, with a higher average Mw and a large amount of short alkyl and naphthenic substituents, is more likely to completely dissolve QI sub-fraction. Thus, the resultant mesophase exhibits an excellent fusible deformability. Besides, the structural feature of semi-rigid oligomer could somewhat loosen molecular association of layered stacking and contribute to the slippage between stacked mesogens due to its steric effects, thereby decreasing the softening points of mesophase pitch. Above modified effects are easily implementable during a suitable process of two-stage thermotreatment, such as the processes of preparing MP-4-0.01-1.0, MP-4-0.005-1.0 and MP-3-0.01-2.0 in this study. It is worthwhile to mention that the vacuum treatment is required to be conducted prior to large-scale coalescence of mesophase spheres in order to obtain spinnable mesophase pitch.

Characteristics of the mesophase and needle coke derived from the blended coal tar and biomass tar pitch

In this work, coal tar pitch was co-carbonized with biomass tar pitch to manufacture hybrid mesophase pitch as precursor for the preparation of needle coke. The properties of mesophase pitches were characterized using a polarized light optical microscope, apparent viscometer, FT-IR, and 1H NMR. After adding biomass tar pitch into coal tar pitch, the mesophase pitches had more flow domain-like texture due to its lower viscosity and softening points. Besides, the addition of biomass tar pitch altered the chemical structure and functional groups of the resulting mesophase pitch, accompanied by the growth of alkyl and naphthenic compounds. Accordingly, the needle coke prepared from the hybrid mesophase pitches showed more flow domain textures and were better aligned uniaxially than the counterpart derived from pure coal tar pitch. The coefficient of thermal expansion of needle coke was reduced from 0.93 × 10−6 °C-1 to 0.42 × 10−6 °C-1. The low viscosity of the mesophase pitches caused by the addition of biomass tar pitch favored the development of mesophase and highly uniaxial arrangement. The increase in the alkyl and naphthenic group compounds greatly improved the performance of the needle coke.

Impact of d-isomer content on the microstructure and mechanical properties of uniaxially pre-stretched poly(lactic acid)

Poly(lactic acid) with 2%, 4%, and 12% d-isomer content were selected to investigate the influence of stereoregularity on mechanical properties of uniaxially pre-stretched PLAs (ps-PLAs). The mobility of molecular chains was activated by pre-stretching because the network structures composed of cohesional entanglements were destroyed, leading to a brittle-ductile transition. The elongation at break increased to 145%, 175% and 190% at pre-stretching ratio of 0.5 for ps-PLA2, ps-PLA4 and ps-PLA12, respectively. The network structures of cohesional entanglements were easier destroyed in PLAs with more d-isomer due to the stereoregularity defects, leading to higher elongation at break. Then the elongation at break decreased with increasing pre-stretching ratio owing to the development of mesophase which might initiate crazing. The more d-isomer the less strain-induced mesophase resulting from the more active chain relaxation, and then the slower decrease of elongation at break. In addition, the modulus and strength of ps-PLAs were all increased with increasing pre-stretching ratio.

Effects of Inductive Condensation on Mesophase Development during Aromatic-Rich Oil Carbonization

A novel method was discussed for the preparation of petroleum-based mesophase pitch with a large domain structure and an ordered microcrystal structure. A condensation pitch with a certain amount o...

Preparation of mesophase pitch from refined coal tar pitch using naphthalene-based mesophase pitch as nucleating agent

By adding naphthalene-based mesophase pitch (NBMP) into refined coal tar pitch (RCTP), pyrolysis products were obtained by dry-blending and co-carbonization method. The properties of pyrolysis products were characterized by polarizing microscope, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD) and Raman spectroscopy. The result shows the NBMP can obviously change the mesophase development of RCTP because it can promote the formation of mesophase spheres during the pyrolysis process. The carbon yield and aromaticity of pyrolysis products were increased with the increase of NBMP content. The anisotropic texture was wide-area structure when the NBMP content was 5 wt%. However, when the content of the additive is increased to 10 wt%, pyrolysis products will appear coking. The main role of this additive is to accelerate the reaction rate as the “nucleating agent” of the thermal condensation reaction.

Mesocarbon Microbead Production from Fluid Catalytic Cracking Slurry Oil: Improving Performance through Supercritical Fluid Extraction

The utilization of fluid catalytic cracking (FCC) slurry oil is a wide concern in modern refineries because of its poor processability. The present study used FCC slurry oil (SLO) as feedstock to produce mesocarbon microbeads (MCMBs) according to its rich aromatic content. A supercritical fluid extraction technique was adopted to remove the undesirable components and thus improve the mesophase development performance. Three different alkanes were used as the supercritical fluids, and the chemical composition of the derived fractions (SFEO) was analyzed. Four stages of mesophase development were observed in the carbonization process. The results showed that heavier feedstock reacted faster and reached the coalescence stage earlier, forming a bulk mesophase. MCMBs with a smooth surface and good morphology were prepared from iso-butane-derived SFEO at a reaction time of 3 h. The quality of the bulk mesophase produced from SFEOs was significantly improved in comparison to DQ SLO.