Aromatic Structures Research Articles

From Pulp to Aromatic Products-Reaction Pathways of Lignin Depolymerization.

This study investigated the depolymerization of lignin into aromatic monomer compounds under hydrothermal conditions. A reaction scheme highlighting secondary alkylation reactions as well as the molecular weight shift was developed based on the experimental data. Lignin is produced in large quantities in paper production and dissolved in what is known as black liquor (BL). To avoid lignin recovery as an additional process step, BL is used directly as feedstock in the hydrothermal liquefaction (HTL) in this work. We performed various batch experiments in micro autoclaves with BL and model substances at different reaction temperatures (TR = 250-400 °C) and a holdingtime of tR = 20 min, as well as continuous experiments (TR = 325-375 °C, tR = 20 min). We were able to show that different derivatives of catechols are the main products among the monomers in our process. With the help of the model substance experiments, we were able to work out three main reactions: demethoxylation, demethylation, and alkylation. This behavior could be observed in the case of BL from hardwood as well as from softwood. 31P nuclear magnetic resonance (NMR) spectroscopy analysis has shown that these reactions take place on aromatic monomers as well as on larger aromatic oligomer structures. At higher temperatures, a large fraction of the carbon ends up in the solid product, while the yields of the monomers decrease sharply. 13C NMR spectroscopy of the solid material shows that the monomers are probably incorporated into the solid phase by repolymerization. We were also able to see this effect using size exclusion chromatography analysis based on the relative molecular weight. From all of the analytical results of the products, a reaction scheme was developed that describes the reaction pathways of the lignin during HTL. Based on this, a reaction kinetic model can be developed in the next step.

Optimization of alkaline hydrothermal treatment for humic acids production from corn straw digestate using the response surface methodology

Anaerobic digestion (AD) technology was widely used for treating waste biomass, during which a large amount of lignin-rich digestate would be produced, needing further treatment. In this study, corn straw digestate (CSD) was used as raw material for hydrothermal humic acids (HHA) producing through alkaline hydrothermal treatment (AHT). According to the response surface analysis, the optimal reaction conditions were determined to be 156°C, 2 hours, and 5% KOH (% of the dry digestate), resulting in a HHA yield of 40.3 wt%. Structural characterization analysis showed the produced HHA had abundant oxygen-containing functional groups (e.g., C-O and CO) in HHA and aromatic structures, which also showed good thermal stability. By AHT with hemicellulose and lignin, the HHA yields reached 79.2%. Hemicellulose and lignin proved to be important components for HHA formation. In addition, the protein content in the EPS extraction solution of HC was significantly reduced compared to CSD, indicating that the dewaterability of the digestate were improved after AHT. This technique provides a feasible approach for the further utilization of residual lignocellulosic materials after anaerobic digestion.

Precursor screening of fruit shell derived hard carbons for low-potential sodium storage: A low lignin content supports the formation of closed pores

Biomass hard carbons are being explored for anode materials of sodium-ion batteries due to the wide availability. However, the precursor screening for optimal microstructure and sodium storage performance is tedious and time-consuming. Here, we selected three kinds of fruit shells to prepare hard carbons for sodium-ion batteries and investigated their structure characteristics and sodium storage performance. It is demonstrated that a low lignin content in fruit shells is favor to the formation of closed pores in the derived hard carbons, thus generating a high low-potential plateau capacity. Among the main component of biomass, lignin with rich aromatic ring structure possesses higher thermal stability than cellulose and hemicellulose. During the pyrolysis and carbonization, lignin may decompose to large-size crystalline domains, which hinders the random stacking of carbon layers. Therefore, as the lower lignin content than pine nut shell and macadamia nut shell (28.4% vs. 39.2% and 37.4%), the walnut shell derived hard carbon shows a largest interlayer distance of 0.397 nm and a highest closed pore area of 391 m2 g−1, contributing to the supreme specific capacity of 362.6 mAh g−1, with a plateau capacity of 195.8 mAh g−1 as well as a remarkable cycle stability. The assembled WNSC//NVP full-cell remains a discharge capacity of 53.1 mAh g−1 after 100 cycles at 0.1 A g−1. This work gives a deep insight of the relationship between biomass composition and microstructure of the derived hard carbons to explore its high sodium storage ability in low-potential region.

Carbon fibers from polypropylene: Structural evolution of precursor fiber during stabilization and carbonization

Utilizing polypropylene (PP) fibers as the precursor material, Polypropylene-based carbon fibers (CFPP) were obtained by carbonization after sulfonation cross-linking with sulfuric acid. First, the mechanism of structural evolution of sulfonated PP fiber (SFPP) during carbonization was investigated at temperatures between 500 °C-1300 °C. According to the results, the chemical structure, as well as the carbon structure transformation of SFPP, depending on the carbonization temperature, i.e., the removal of organic functional groups, the fusion to small aromatic structures, and the transformation to ordered carbon structures. The carbon content of the carbon fibers obtained at 1300 °C was as high as 93.4 %. Subsequently, various PP fibers with different diameters and crystalline structures were prepared by melt spinning and subsequent thermal-drawing treatment, and the relationship between their structures and the properties of CFPPs was investigated. The sulfonation reaction rate of PP fibers increased as the sulfonation reaction proceeded and was synergistically regulated by the crystalline structure and fiber diameter. The CFPP with a smaller diameter exhibited a more homogeneous skin-core structure, together with higher overall graphitization, smaller graphite layer spacing, and better graphite microcrystalline structure, and thus its conductivity and mechanical properties of the carbon fiber were significantly improved. The mechanical properties and volume resistivity of the prepared CFPP reached 338.6 MPa and 4.91×10−5 Ω·m, respectively.

Investigation on Combustion Characteristics and Molecular Structures of Heiyanquan Mining Area, Xinjiang, China.

In order to comprehend the molecular composition of coal and better understand the process of coal combustion, this study involved the development of a molecular structure model for Heiyanquan coal in Xinjiang, as well as the optimization and annealing dynamics simulation of the model. Thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), and high-resolution transmission electron microscopy (HRTEM) were utilized to investigate the spontaneous combustion characteristics of coal at different temperatures (room temperature, 50-500 °C with 50 °C interval). The findings revealed that the coal primarily consists of aromatic carbon, with the aromatic structure mainly comprising naphthalene, anthracene, and phenanthrene, and the aliphatic carbon mainly consisting of CH2 and CH, along with a small quantity of minerals. The empirical molecular formula of Heiyanquan coal was determined to be C175H125O21N3. After the optimization, the total energy of the model was significantly reduced, and the aromatic layers tended to align in a regular parallel manner, with van der Waals energy playing a crucial role in maintaining structural stability. As the temperature increased, the activation energy of the three stages also increased, with the combustion stage exhibiting the highest activation energy. The presence of hydroxyl groups and oxygen-containing functional groups was found to mainly participate in the reaction, while the content of aromatic hydrocarbons remained relatively stable, C=C exhibited a decreasing trend, and C-O displayed an increasing trend. Moreover, it was observed that 1 × 1 and 2 × 2 were the predominant aromatic stripes in the coal samples, accounting for more than 90% of the total stripes.

Mechanochemical regulation of microcrystalline in coal-derived disordered carbon for improved sodium storage: Metamorphic grade

Coals are common precursors of the disordered carbon anodes for sodium ion batteries. In order to hinder the long-range ordered development of coal precursors during thermal conversion, the acid reagents and calcination under air atmosphere have been adopted in the pre-oxidation procedure, not in accordance with the demand of green energy storage. Herein, the mechanochemical pretreatment was employed to break the aromatic structures and generate the edge defects and oxygen functional groups on the coal surface, which would suppress the long-range ordered tendency and promote the introduction of nitrogen heteroatoms during following calcination. With the increasing metamorphic grades, the molecular rigidity of coal precursors increases owing to more highly polycondensed aromatic structures and less interior buffer space. The aromatic structures in the highest-ranked anthracite are broken most heavily during the mechanochemical process. Thus the nitrogen-doped anthracite-based carbon materials have the most disordered carbon structures and deliver a high reversible capacity of 323 mA h g−1 under 0.03 A/g after 90 cycles. This work provides a facile and green solution to fabricate the highly disordered carbon anodes with low cost and high performance from the industrial raw materials.

Chemical composition of soil humin in an organic soil profile

Humin is identified as the most recalcitrant fraction of soil organic matter, but its synthesis and depth variability in the soil profile are unknown. Here, we suggest that carboxyl-rich alicyclic structures (CRAM) and fused aromatic ring structures (FAR) can process significant components of the humin structure. We conducted molecular-level characterization of humin using advanced solid-state nuclear magnetic resonance spectroscopy (SSNMR) experiments and calculated the proportion of FAR and functionalities of CRAM (OCq, –C(CH)n, –CH3) structures. Dipolar dephased (dd) direct polarization magic angle spinning (DPMAS) NMR experiments provided insights into non-protonated carbon and mobile quaternary carbons. We calculated the proportions of non-protonated aromatic carbon and non-polar aliphatic C in the organic layers of the topsoil (Oa), mid-soil (Om), and mineral subsoil (Cg). It was evident that the total aliphatic carbon constitutes a significant proportion of humin, as is the non-protonated C attached to CH3. The 13C dd/DPMAS NMR spectrum of Cg humin clearly showed the formation and preservation of hydrophobic OCq, which is indicative of CRAM structures. CRAM structures could be attached to FAR, which makes the whole structure relatively more hydrophobic, a critical humin functionality in deeper soil. The findings from our research can be successfully utilized in terrestrial carbon sequestration studies to amplify the potential of humin as a recalcitrant carbon reservoir.

Mechanochemical evolution of coal microscopic groups: A new pathway for mechanical forces acting on coal spontaneous combustion

Coal spontaneous combustion (CSC) remains a significant threat to regional ecological environments. As coal mining operations extend deeper into the earth, the increasingly complex mechanical force conditions in deep-seated mines escalate the potential risk of CSC. Mechanical forces such as ground stress and mechanical cutting are traditionally believed to be linked to CSC through the following pathway: mechanical forces act → mechanical energy is input → mechanical crushing and pulverization occur → coal–oxygen contact area increases → CSC accelerates. Noteworthily, these forces do more than just physically break coal; they also trigger a mechanochemical effect (MCE) that alters coal's microscopic chemistry. However, an independent evaluation of its influence on CSC was lacking. This study characterized coal's microscopic chemical group responses to the MCE. It was found that the MCE led to the degradation of aliphatic side chains while enhancing the polycondensation of aromatic ring structures, indicating a synergistic effect. Additionally, an increase in oxygen-containing functional groups, such as alkyl/aryl ethers, suggested enhanced interactions of the coal microscopic groups with oxygen due to mechanical forces. Based on these findings, an MCE-modified coal macromolecular model was developed and molecular quantum mechanical calculations were conducted. The results indicated that the MCE boosted coal macromolecule reactivity, thus facilitating easier activation. These conclusions were validated through modern thermal analysis tests. Finally, this study proposed a new pathway of mechanical forces acting on CSC: mechanical forces act → mechanical energy is input → the MCE occurs → evolutions of the microscopic groups within coal are induced → Activity of coal molecules is enhanced → CSC accelerates.

Effect of pyrolysis temperature on the binding characteristics of DOM derived from livestock manure biochar with Cu(II).

Biochar-derived dissolved organic matter (BDOM) has the potential to influence the environmental application of biochar and the behavior of heavy metals. In this study, the binding properties of BDOM derived from livestock manure biochar at different pyrolysis temperatures with Cu(II) were investigated based on a multi-analytical approach. The results showed that the DOC concentration, aromatics, and humification degree of BDOM were higher in the process of low pyrolysis of biochar. The pyrolysis temperature changed the composition of BDOM functional groups, which affected the binding mechanism of BDOM-Cu(II). Briefly, humic-like and protein-like substances dominated BDOM-Cu(II) binding at low and high pyrolysis temperatures, respectively. The higher binding capacity for Cu(II) was exhibited by BDOM derived from the lower pyrolysis temperature, due to the carboxyl as the main binding site in humic acid had high content and binding ability at low-temperature. The amide in proteins only participated in the BDOM-Cu(II) binding at high pyrolysis temperature, and polysaccharides also played an important role in the binding process. Moreover, the biochar underwent the secondary reaction at certain high temperatures, which led to condensation reaction of the aromatic structure and the conversion of large molecules into small molecules, affecting the BDOM-Cu(II) binding sites.

Highly-selective metalation of porphyrin enabled by distinct aromatic ring-fused structures

Metalation is an effective strategy for tuning the optical, magnetic, and other physical properties of porphyrins, which play an important role in material synthesis and biological activities. Multiple aromatic ring-fused structures (ARFSs) can be formed by cyclodehydrogenation from a single porphyrin compound. Understanding the various bonding forms and bond strengths of aromatic allotropes with metals remains as an intriguing area. The role of ARFSs in porphyrin metalation is yet unknown. Herein, we demonstrate highly selective metalation of porphyrin enabled by the distinctive ARFSs derived from a single precursor on Ag(111). ARFS-A is self-metalated with a high yield (∼100%) on Ag(111), setting one Ag atom in its molecular central cavity. ARFS-B is barely metalated until full molecular desorption from the substrate. The selectivity is attributed to the differences in metalation energy barriers originated from the different dehydrocyclization structures and adsorption configurations of porphyrin allotropes on the surface. By exposing the relationship between the ring-fused structures and porphyrin metalation, this work offers insights into how to design aromatic ring-fused porphyrins structurally and shows how to control the occurrence and selectivity of porphyrin metalation.

Characteristics of Dissolved Organic Matter in Uranium Hosting Aquifers and Potential Molecular Transformation During Neutral In Situ Leaching

AbstractDissolved organic matter (DOM) is widespread in uranium (U) hosting aquifer, a key substance affecting CO2 + O2 in situ leaching (ISL) of U by consuming injected O2. However, molecular composition and molecular transformation of DOM are poorly understood in this aquifer during the U mining. To address this issue, Fourier transform ion cyclotron resonance mass spectrometry was applied to investigate DOM molecules in groundwater samples and rock samples collected from a U mining aquifer. The high proportion of labile tyrosine‐like component and BIX value in monitoring wells (BM) indicated the biological origin of DOM. CHOS and aliphatic were the major components of water‐soluble organic matter (WSOM) in U‐bearing rocks, but CHO and highly unsaturated structures with high oxygen (HUSHO) were the main components of DOM in BM. The ISL led to the release of WSOM and the oxidation of DOM, which accounted for 24.5%–57.4% and 39.1%–65.7% of expected DOM, respectively. Potential molecular transformations (PMTs) results showed that the intragroup transformations dominated, and remarkable transformations from CHON and CHONS to CHO occurred during ISL. The positive net PMTs of condensed aromatic structure (CAS), aromatic structures (AS), and aliphatic suggested that they were transformed from HUSLO and HUSHO. A gradual decrease in (DBE−O)/Cwa and a gradual increase in NOSCwa indicated that the saturated degree and oxidation state of DOM increased during mining. This work successfully identified molecular characteristics of DOM in U hosting aquifer, and proposed a paradigm of DOM transformation pathways during ISL.

Co-pyrolysis of low-rank coal and rice stalk: A comprehensive study on product distributions, product properties, and synergistic effects

Co-pyrolysis of low-rank coal and rice stalk is an important way to achieve hierarchical and efficient utilization of energy. This work explored how blend ratios (0–100 wt%) and temperatures (773–1073 K) affect pyrolysis product distribution and characteristics. The results showed that a higher rice straw ratio (80 wt%) significantly reduced the yield of char (22.38–26.9 wt%) compared with 20 wt% of rice straw at different temperatures. The yield and physicochemical properties of target products were closely related to process parameters, which can provide a promising opportunity to acquire desired products by reaction conditions optimization. Co-pyrolysis was able to inhibit the production of large aromatic ring structures in char. High temperature promoted the generation of cross-linked structures, which was influenced by the blend ratio. The synergistic effects of BET surface area and pore volume were most pronounced when the J content was 40 wt% at 873 K, and their increments were 59.6 m2/g and 0.027 cm3/g, respectively. For the char derived from lower rice straw proportions (0, 20, and 40 wt%), the main combustion range and the maximum combustion rate temperature showed a progressive shift towards higher values with temperature increasing. The research is valuable of guiding high-value utilization of agricultural residues and energy transitions.

2D Conjugated Metal-Organic Frameworks: Defined Synthesis and Tailor-Made Functions.

Conspectus2D conjugated metal-organic frameworks (2D -MOFs) have emerged as a class of graphene-like materials with fully π-conjugated aromatic structures. Their unique structural characteristics provide abundant physiochemical features, including regular nanochannels, high electrical conductivity, and customizable band gaps. Recent intensive research has significantly advanced this field, yet the exploration of 2D c-MOFs with enhanced features is limited by the availability of organic linkages and topologies. Designing novel ligands is essential for the construction of new 2D c-MOFs with high crystallinity, excellent conductivity, and tailor-made functions.In this Account, we summarize our recent contributions in fine-tuning the topology of 2D c-MOFs through precise ligand design, thereby giving them fantastic structures and tailor-made functions. First, we propose the concept of replacing planar ligands by nonplanar ligands on conductive MOF skeletons. The incorporation of nonplanar ligands improves the solubility of large π-conjugated organic molecules without interfering with the interlayer π-stacking. Our investigation discovered that conjugate polycyclic aromatics-based ligands can be synthesized through in situ Scholl reactions by means of oxidative cyclodehydrogenation of a nonplanar precursor ligand during the solvothermal synthesis process. Hence, fully conjugated 2D c-MOFs can be directly synthesized from nonplanar organic ligands, simplifying and diversifying the preparation of 2D c-MOFs. Accordingly, the design flexibility of the ligands expands the topological structures and pore types. By controlling the synthesis conditions, we can successfully induce either a rhombus or a kagome topology from a nonplanar D2 symmetric ligand. Moreover, by employing a ligand engineering strategy, we incrementally increase the number of coordination functional groups on a twisted hexabenzocoronene core, resulting in the formation of three distinct symmetric hydroxyl ligands. These ligands elicit diverse target topologies and pore sizes, resulting in variances in the coordination node density on the skeletons. This, in turn, leads to differences in electron transfer abilities, ultimately causing variations in the electrical conductivity and mobility. In addition, we employ a straightforward coupling method to incorporate redox components, such as salphen and pyrazine, into nonplanar ligands, facilitating the synthesis of 2D c-MOFs with highly active centers. This strategy confers upon the resulting frameworks substantial capacity for catalysis and energy storage, offering a good platform for elucidating the structure-property relationships at the molecular level. Moreover, the well-defined synthesis of 2D c-MOFs imparts them with specific properties, particularly in the fields of electrical, electrochemical, and spintronic applications. At the end, the primary challenges facing 2D c-MOFs in achieving tailor functions and their practical applications are proposed. This account is expected to evoke new inspirations and innovative research in the field of 2D c-MOFs, especially in emerging interdisciplinary research areas.

Surface alteration on biochar in long-term application: Insights into pyrolysis, freeze-thaw aging, and dissipation

Biochar, a carbonaceous material produced by pyrolysis, is subject to physical and chemical changes over time in its long-term application. Pollutants (e.g., TBBPA) through the environmental fate and transport can be immobilized on the biochar surface, causing an unexpected environmental impact. The objective of this study is to investigate the alteration of surface in freeze-thaw cycles to explore the long-term behaviors of biochar interactions with pollutants. The aging process of biochar is elucidated through characterization using X-ray photoelectron spectroscopy (XPS) and surface charge density analysis. These findings indicate that the aging process promotes the redistribution and re-equilibration of surface functional groups, resulting in the emergence of carboxyl groups and the disruption of aromatic structures. Using 2D-COS approaches, it was observed that the freeze-thaw aging of biochar resulted in a sequence of aromatic alkane (CH) > hydroxyl groups (-OH) > polysaccharide groups (CH) > ether and ester groups (CO-C) > carboxyl and lipid groups (C = O). The study also revealed a dissipative process with a specific sequence, depending on the level of pyrolysis of the biochar. This research contributes to an enhanced comprehension of the long-term use of biochar, particularly in the context of freeze-thaw aging processes and contaminant dissipation. This understanding can inform applications, regulations, and policies related to biochar in the context of long-term utilization.

Isotherm and Kinetic Studies on Adsorption of Yellow Azo Dyes (Sunset Yellow, Tartrazine) using <i>Kigelia africana</i> (Lam.) Benth., Leaf Extract Mediated Iron Nanoparticles

Sunset yellow and tartrazine are commonly used azo dyes extensively employed in beverages and food products such as soda, fruit juices, confectionery, and cakes. These dyes hold the distinction of being the second and third most frequently utilized colour additives in a wide array of beverage products. The discharge of these synthetic food dyes into industrial wastewater can lead to significant environmental and health issues. Due to its aromatic structure, this dye is resistant to breaking down into harmless compounds, and its removal through effective adsorption presents an economical and efficient solution. The use of renewable bioresources for the eco-friendly production of metallic nanoparticles represents a recent and growing trend in nanotechnology research, offering enhanced environmental safety. In this current research, we achieved the green and cost-effective synthesis of monodispersed Iron Nanoparticles (FeNPs) with exceptional stability by utilizing an aqueous extract of Kigelia africana (Lam.) Benth is the primary bioresource for this synthesis. The FeNPs were noticed to be uniformly distributed spherical-shaped particles having smooth surfaces with a 26-34 nm size range and an average particle size of 28 ± 0.86 nm. The XRD results confirm that the FeNPs were rhombohedral phase structures with 71.43% of elemental iron. These synthesized nanoparticles were applied for the removal of sunset yellow and tartrazine dyes were investigated and more than 90% were removed. The adsorption isotherm study was best fitted with the Langmuir model, and the maximal adsorption capacity was found to be 76.29 and 47.22 mg/g for sunset yellow and tartrazine respectively. The adsorption reaction follows pseudo-first-order kinetics with a high correlation coefficient. Repeated cycles of regeneration, reuse and stability showed very high removal efficiency and stability. In conclusion, the biosynthesis of metal nanoparticles demonstrates substantial promise for applications in environmental protection.

Exploring chemical reactions to enhance thermal and dispersion stability of kraft and organosolv lignin

Lignin has been overlooked and used as a waste for long due to its complex and partially hydrophobic structure. Many efforts have been carried out to overcome these deficiencies and apply it as a high-value product, which are insufficient to reach the full potential of lignin in various advanced applications, since they require with procedures for the obtaining of more specific and fine-tuned chemical structures. This work focuses on the obtaining of differently structured hydrophilic lignins derived both from Kraft and organosolv isolation processes. The chemical structures of the different lignin types were studied, and the effect of the structural differences in the modification processes and their subsequent properties analyzed, valorizing their potential application for diverse purposes. The carboxymethylation and sulfomethylation reactions were carried out with the aim of enhancing the polarity of the lignin samples, while the methylation reaction aimed to obtain lignins with higher stability. The physicochemical analyses of the samples, carried out by FTIR, GPC, 31P NMR, 13C NMR, and HSQC NMR, verified the effectiveness of the chemical reactions and conditions selected, obtaining lignins with lower hydroxyl content, due to their substitution and insertion of carboxymetyl, sulfomethyl and methyl groups, therefore obtaining more condensed, aromatic and oxygenated aromatic carbon structures. While the methylation reaction was the most efficient in substituting the OH groups, due to its non-selectivity, OL showed higher modification yields than KL. In terms of the thermal and morphological properties, analyzed by DLS and TGA respectively, it was observed that the modified samples showed lower Z potential values, along with higher conductivity, being the sulfomethylated organosolv lignin the one showing the best results, which was also the one with the smallest particle size and polydispersity index. Finally, all the modified samples showed higher T50% values, suggesting a better stability towards degradation.

Monomer Dependence of Colorless and Transparent Polyimide Films: Thermomechanical Properties, Optical Transparency, and Solubility.

Six poly(amic acid)s (PAAs) were synthesized by reacting bis(3-aminophenyl) sulfone with various dianhydride monomers such as pyromellitic dianhydride, 4,4'-biphthalic anhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, 4,4'-oxidiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 4,4'-(hexafluoroisopropylidene) diphthalic anhydride. These PAAs were then converted to polyimide (PI) films by thermal imidization at various temperatures. To obtain colorless and transparent PI (CPI), the dianhydride monomer used in this study had an overall bent structure, a structure containing a strong electron-withdrawing -CF3 substituent or an alicyclic ring. In addition, some monomers contained ether or ketone functional groups in their bent structures. The thermomechanical properties, optical transparency, and solubility of CPI films with six different dianhydride monomer structures were investigated, and the correlation between the monomer structure and CPI film properties was clarified. Overall, CPI with an aromatic main chain structure or a linear structure had excellent thermal and mechanical properties. In contrast, CPI with a bent structure containing functional groups or substituents in the main chain exhibited excellent optical transparency and solubility.

Investigation on the chemical structure evolution and action mechanism of coal during catalytic combustion

Catalytic combustion is one of the most promising technologies to realize efficient and clean coal combustion, but its catalytic mechanism is unknown until now. This study selected three types coal to explore the influence of catalysts on the chemical structure, surface morphology, and action mechanism during combustion. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were characterized the surface chemical structure of combustion products. The results showed that the aliphatic hydrogen decreased and then increased, the content of –CO and aromaticity(I) increased, and the aromatic condensation (DOC) and CC content decreased by catalysts. Both FTIR and XPS results demonstrated that the catalysts were easy to promote the dehydrogenation condensation reaction between coal molecules, disrupting the stability of coal aromatic structure, thereby generating many free radicals and improving coal combustion. BET and scanning electron microscopy (SEM) were used to observe the effect of catalysts on the pore structure and surface morphology of combustion products. The results showed that the pore structure of product with catalysts continuously formed from micropores to medium pores and even large pores, which accelerated the oxygen transport and chemical reaction on coal surface. Finally, the mechanism of catalytic coal combustion was summarized.

The effects of limonene and eugenol additives in n-heptane and low-octane gasoline on the emission characteristics and fuel consumption of single-cylinder gasoline engine

This study investigated the effects of two additive polarities: polar (eugenol) and nonpolar (limonene) additives blended into n-heptane and low-octane gasoline. These compounds were chosen due to their unique molecular structure characteristics which influences the exhaust emissions. The physicochemical properties, fuel consumption, and exhaust gas emissions of a single-cylinder gasoline engine were measured. Four fuel blends were created by blending eugenol and limonene on a volumetric basis, n-heptane-eugenol (NHE), n-heptane-limonene (NHL), low-octane gasoline-eugenol (GE), and low-octane gasoline-limonene (GL). Tests were conducted on a single-cylinder gasoline engine. The exhaust gas emissions were analyzed using gas chromatography, and the role of each additive substance in the formation of carbon monoxide (CO), unburned hydrocarbon (HC), residual oxygen (O2), and carbon dioxide (CO2) emissions was validated using Hyperchem simulation and gas chromatography mass spectrometry. Owing to differences in the molecular structure and energy content of the two additives, the fuel consumption of NHE-fueled vehicles increased by 19.69% compared to NHL, whereas GE decreased by 32.15% compared to GL. Owing to the presence of oxygen atoms and low binding energy, blending eugenol with n-heptane and low-octane gasoline significantly reduced CO by 1.87% higher than limonene. However, eugenol’s aromatic structure can only reduce 14.45% of HC emission, while limonene, with its dynamically moving electrons and nonpolar properties can reduce up to 18.24%. It was discovered that the two additives could improve the quality of exhaust gas emissions.

Comparative investigation of low temperature oxidized and pyrolyzed cokes from the inferior heavy oil: Structural feather, thermo-oxidation behavior, and kinetics

It was crucial to study the low temperature coking process for the heavy oil, which affected the fuel availability and subsequent in-situ combustion progress. From this perspective, low temperature coking experiments with different atmospheres were accomplished for the inferior heavy oil to obtain oxidized (cokeLTO) and pyrolytic (cokeLTP) cokes, which were further employed to trace structural feathers via joint analysis of elemental analysis, Fourier transform infrared spectrophotometry (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra, and to characterize thermo-oxidative characteristics and kinetics via different thermal analyses (TG-DTG/DSC) and model-free methods. The results showed that a relatively less aliphatic and more aromatic structures were contained in cokeLTO with a relatively higher proportion of C-O, C = O, O-C = O groups and C/H ratio, implying that oxygen atom was served as the promoter to replace hydrogen atom and accelerate macromolecular structure formation. While the decomposition and conversion of N- and S- functional groups were complicated and insensitive to the coking atmosphere. Furthermore, cokeLTO had a more dominant thermo-oxidation behavior than cokeLTP with better exothermic characteristic and lower activation energy distribution. From this study, it could provide a vital piece of updated insights on the role of low temperature oxidation process in coke deposition and feature.