Degree Of Aromaticity Research Articles

Optical properties and molecular composition of wintertime atmospheric water-soluble organic carbon in different coastal cities of eastern China

To evaluate the optical properties and molecular composition of water-soluble organic carbon (WSOC) in the atmosphere of coastal cities, particle samples were collected in Tianjin, Qingdao and Shanghai, three coastal cities in eastern China. Subsequent analysis by ultraviolet visible and fluorescence spectrometer and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry were performed. The results showed that the concentration levels and light absorption ability of WSOC decreased from the north to south cities, ranking as Tianjin > Qingdao > Shanghai. Three major fluorescent components including less‑oxygenated humic-like substances (52–60 %), highly‑oxygenated humic-like substances (15–31 %) and protein-like substances (17–31 %) were identified in WSOC based on the fluorescence spectroscopy and parallel factor analysis, which might be closely related to anthropogenic emissions and continental sources as well as secondary formation processes. Five subgroups of molecular components were further identified in WSOC, including the predominant CHON compounds (35–43 %), sulfur-containing compounds (i.e., CHONS and CHOS compounds, 24–43 %), CHO compounds (20–26 %) and halogen-containing compounds (1–7 %). Compared to marine air masses influenced samples, WSOC affected by continental air masses exhibited higher light absorption coefficients and generally had a higher degree of aromaticity and unsaturation, as well as contained more molecular formulas of WSOC, especially enriched with sulfur-containing compounds. In contrast, relatively more abundant halogen-containing compounds were identified in the marine air masses influenced samples. Overall, this study provided new insights into the light-absorbing and chemical properties of WSOC in coastal cities, especially under the influences of continental and marine air masses.

Thermal pretreatment of poplar sawdust at 100 °C in water or with microwave heating impacts the pyrolysis behaviors

Drying at 100 °C is a common practice for processing many biomasses for their further thermochemical conversion via the routes such as pyrolysis. The drying temperature of 100 °C is low, but might not be too low to cause any impact on pyrolytic behaviors of a biomass feedstock. In this study, varied scenarios of thermal pretreatment of poplar sawdust (oven-drying, boiling in water and microwave heating) at 100 °C were screened for probing their potential influence on the pyrolytic behaviors at 500 and 750 °C. Comparing with oven-drying, boiling in water (cooking) and microwave heating at 100 °C could remove some oxygen-containing species, increasing carbon content of the pretreated sawdust and promoting carbonization in pyrolysis. This enhanced formation of biochar, heavy π-conjugated organics in bio-oil, but suppressed generation of gas. The cooking or microwave heating pretreatment also promoted aromatization to form the biochar of higher thermal stability, higher crystallinity, and higher aromatic degree, due to the enhanced deoxygenation reactions in the pyrolysis. The in-situ IR characterization suggested that microwave pretreatment promoted generation of unsaturated ketones and also the species with olefinic C = C, favoring their further aromatization. The cooking pretreatment impacted transformation routes of the oxygen-containing organics, thus modifying pyrolysis behaviors of the pretreated sawdust.

Amide- and bis-amide-linked highly potent and broadly active antifungal agents for the treatment of invasive fungal infections- towards the discovery of pre-clinical development candidate FC12406

Most fungal infections are common, localized to skin or mucosal surfaces and can be treated effectively with topical antifungal agents. However, while invasive fungal infections (IFIs) are uncommon, they are very difficult to control medically, and are associated with high mortality rates. We have previously described highly potent bis-guanidine-containing heteroaryl-linked antifungal agents, and were interested in expanding the range of agents to novel series so as to reduce the degree of aromaticity (with a view to making the compounds more drug-like), and provide broadly active high potency derivatives. We have investigated the replacement of the central aryl ring from our original series by both amide and a bis-amide moieties, and have found particular structure-activity relationships (SAR) for both series’, resulting in highly active antifungal agents against both mold and yeast pathogens. In particular, we describe the in vitro antifungal activity, absorption, distribution, metabolism and elimination (ADME) properties, and off-target properties of FC12406 (34), which was selected as a pre-clinical development candidate.

Regulating the properties of activated carbon for supercapacitors: impact of particle size and degree of aromatization of hydrochar

Regulating the properties of activated carbon for supercapacitors: impact of particle size and degree of aromatization of hydrochar

Seasonal variations of dissolved organic matter chemistry in a semi-enclosed and eutrophic coastal bay in southeastern China: Implications for carbon cycling

As the widely distributed transition zones connecting the terrestrial and marine ecosystems, coastal bays have long water retention times to reconstruct the DOM pool affecting global carbon cycling. However, we still have a limited understanding of mechanisms shaping the carbon cycling of coastal bays at regional scales. To address this issue, we combined stable carbon isotopes, ultraviolet–visible absorption, fluorescence spectroscopy, and ultrahigh-resolution mass spectrometry to investigate the spatiotemporal chemistry of dissolved organic matter (DOM) in Xiangshan Bay, a semi-enclosed, eutrophic bay in southeastern China. The DOM in Xiangshan Bay was characterized by a higher degree of humification and aromaticity during winter, whereas the inverse signature during summer. Results showed that the significant seasonal variation of DOM chemistry was mainly modulated by intense primary productivity stimulated by nutrients during summer, and other factors including sediment pore water DOM release and photochemical reactions. Additionally, based on the microbial carbon pump (MCP) hypothesis, marine microorganisms may synthesize biologically recalcitrant DOM with millennia turnover time. The efficient MCP associated with reduced nutrients probably acted as a critical factor in Xiangshan Bay, leading to the formation of additional refractory molecular formulae (carboxyl-rich alicyclic molecules) and a more recalcitrant signature of DOM during winter. Incorporated with seven other coastal bays across China, it is revealed that anthropogenic inputs substantially contributed to Chinese coastal bays. Further studies need to better constrain the biogeochemical implications of these anthropogenic inputs. More importantly, decreasing the anthropogenic input of nutrients to coastal bays may enhance their functions in long-term carbon sequestration.

Effects of Functional Groups in Coal with Different Vitrinite/Inertinite Ratios on Pyrolysis Products.

Maceral composition is one of the key factors affecting the liquefaction and gasification of coal, which has attracted extensive attention of researchers working on coal chemical industry. To elucidate the impact of vitrinite and inertinite in coal on pyrolysis products, vitrinite and inertinite were extracted from a single coal sample and mixed to create six samples with varying vitrinite/inertinite ratios. The samples were subjected to thermogravimetry coupled online with mass spectrometry (TG-MS) experiments, and the Fourier transform infrared spectrometry (FITR) experiment was used to determine the macromolecular structures before and after the TG-MS experiments. The results show that the maximum mass loss rate is proportional to the vitrinite content and inversely proportional to the inertinite content, and increased vitrinite content accelerates the pyrolysis process and shifts the pyrolysis peak to low temperatures. Based on FTIR experiments, the sample's CH2/CH3 content, representing the length of aliphatic side chains, decreases significantly after pyrolysis, and the greater the loss of CH2/CH3, the greater the intensity of organic molecule production, indicating that aliphatic side chains are likely to yield organic molecule products. The aromatic degree (I) of samples rises sharply and steadily with increasing inertinite content. After high-temperature pyrolysis, the polycondensation degree of aromatic rings (DOC) and relative abundance of aromatic and aliphatic hydrogen (Har/Hal) within the sample increased significantly, indicating the thermal degradation rate of aromatic hydrogen content is much lower than that of aliphatic hydrogen. When the pyrolysis temperature is lower than 400 °C, the higher the inertinite content, the easier it is to produce CO2, whereas an increase in vitrinite leads to an increase in CO production. At this stage, the "-C-O-" functional group is pyrolyzed to produce CO and CO2. When the temperature exceeds 400 °C, the CO2 output intensity of vitrinite-rich samples is much higher than that of inertinite-rich samples, while the CO output intensity of vitrinite-rich samples is lower, and the higher the vitrinite content, the higher the peak temperature of CO gas production of samples, indicating that when the temperature exceeds 400 °C, the increase of vitrinite inhibits CO production and promotes CO2 production. At this stage, the reduction of each sample's "-C-O-" functional group after pyrolysis is positively correlated with the maximum CO gas production intensity, and the reduction of each sample's "-C=O" functional group after pyrolysis is positively correlated with the maximum CO2 gas production intensity. As a result, the "-C-O-" functional group is more likely to produce CO, whereas the "-C=O" functional group is more likely to be pyrolyzed to CO2. Hydrogen is primarily produced during the polycondensation and aromatization processes, and its production is proportional to the dynamic DOC values after pyrolysis. The higher the I value after pyrolysis, the lower the maximum gas production peak intensity of CH4 and C2H6, which indicates that increasing the aromatic proportion is detrimental to CH4 and C2H6 production. This work is expected to provide theoretical support of the liquefaction and gasification of coal with different vitrinite/inertinite ratios.

In-situ infrared and kinetic characteristics analysis on pyrolysis of tar-rich coal and macerals

Tar-rich coal is a high-quality coal-based oil and gas resource, pyrolysis of tar-rich coal is crucial to alleviate the world energy crisis and pressure on oil and gas resources. This paper analyzed pyrolysis characteristics of tar-rich coal and macerals and evolution mechanism of main functional groups by thermogravimetric analyzer and Fourier in-situ infrared spectrometer. The thermogravimetry results showed that when the heating rate was 10 ∼ 40 °C·min−1, inertinite's volatile yield was 25.21 %∼27.27 %, significantly lower than that of tar-rich coal and vitrinite, the average activation energy required for tar-rich coal pyrolysis was 185.63 kJ·mol−1, lower than 360.56 kJ·mol−1 of vitrinite, indicating that inertinite had more macromolecular structure and was not easy to be pyrolyzed and volatilized, volatile was more likely to be generated and liberated in tar-rich coal. The results of in-situ infrared analysis showed that coal mainly contained out-of-plane aromatic CH, C-O-C, aliphatic-CH3, –CH2, –CH, C = O, –OH and other major functional group structures. Vitrinite contained more aliphatic-CH2, –CH3, –CH and other aliphatic hydrocarbon structures. Tar-rich coal and vitrinite contained more hydrogen-rich structures such as aliphatic CH and active groups such as free-OH, inertinite contained more ether bonds, C = O and hydrogen bonds, almost no aliphatic hydrocarbons and oxygen-containing active groups, and had stronger structural stability. The results of structural parameter analysis showed that under the same conditions, for vitrinite, the aliphatic chain length and hydrocarbon potential were 1.14 and 2.37, greater than those of tar-rich coal and inertinite. The aromatic degree and aromatic condensation degree were 0.39 and 0.48, lower than those of tar-rich coal and inertinite. The pyrolysis characteristic indexes of tar-rich coal and vitrinite were 90.04 (10-8 %·min−1·°C−3) and 93.64 (10-8%·min−1·°C−3), significantly higher than 30.90 (10-8 %·min−1·°C−3) of inertinite. The above results showed that vitrinite had more aliphatic long chains and alkyl side chain, tar-rich coal and vitrinite had better pyrolysis reaction performance and strong volatilization ability, inertinite had less hydrogen-rich structure, poor pyrolysis reaction performance and stronger stability. Based on the discussion of the relationship between functional groups distribution and reaction performance of tar-rich coal and macerals, variation range of structural parameters with functional groups distribution was obtained.

Microorganisms and their metabolites affect the content of polycyclic aromatic hydrocarbons and their derivatives in pyrolyzed material

Toxic polycyclic aromatic hydrocarbons (PAHs) and more toxic N- and O-containing derivatives can be determined in biochar. However, their fate in the environment and bioavailability depends on many parameters and was not studied yet. In the presented studies a set of biochars obtained from various feedstock at the same pyrolysis temperature (600 °C) subjected to environmental pressure e.g. soil microorganisms and enzymes was described. Presented study aimed to determine the effect of biological agents on the physicochemical characteristic and the content of PAHs and their derivatives in biochars after long-term treatment (6 months). The results indicated that enzymatic aging usually lowered (up to 94 %) the content of PAHs and their derivatives in biochar. Simultaneously, biological aging reduced the bioavailability of tested compounds. Considering the total fraction of PAHs and their derivatives, biochars treated with nutrients and microbial inoculum were characterized by the lowest content of analytes (even in comparison to biochars treated with nutrients alone). To complement the obtained results, the content of C, H, N, O, and ash as well as specific surface area, aromaticity, polarity, and hydrophilicity in biochar before and after modifications were determined. In general, enzymatic aging increased, and biological aging decreased the content of C% and H% in biochar. Both aging processes lowered the H/C ratio which indicated the decrease of the aromatization degree for artificially altered biochar.

Effects of functional group loss on biochar activated persulfate in-situ remediation of phenol pollution in groundwater and its countermeasures

Biochar is considered a good activator for use in advanced oxidation technology. However, dissolved solids (DS) released from biochar cause unstable activation efficiency. Biochar prepared from saccharification residue of barley straw (BC-SR) had less DS than that prepared directly from barley straw (BC–O). Moreover, BC-SR had a higher C content, degree of aromatization, and electrical conductivity than BC-O. Although the effects of BC-O and BC-SR on activation of Persulfate (PS) to remove phenol were similar, the activation effect of DS from BC-O was 73% higher than that of DS from BC-SR. Moreover, the activation effect of DS was shown to originate from its functional groups. Importantly, BC-SR had higher activation stability than BC-O owing to the stable graphitized carbon structure of BC-SR. Identification of reactive oxygen species showed that SO4•-, •OH, and 1O2 were all effective in degradation by BC-SR/PS and BC-O/PS systems, but their relative contributions differed. Furthermore, BC-SR as an activator showed high anti-interference ability in the complex groundwater matrix, indicating it has practical application value. Overall, this study provides novel insight that can facilitate the design and optimization of a green, economical, stable, and efficient biochar-activated PS for groundwater organic pollution remediation.

Microbiological mechanism for “production while remediating” in Cd-contaminated paddy fields: A field experiment

Security utilization measures (SUMs) for “production while remediating” in moderate and mild Cd-polluted paddy fields had been widely used. To investigate how SUMs drove rhizosphere soil microbial communities and reduced soil Cd bioavailability, a field experiment was conducted using soil biochemical analysis and 16S rRNA high-throughput sequencing. Results showed that SUMs improved rice yield by increasing the number of effective panicles and filled grains, while also inhibiting soil acidification and enhancing disease resistance by improving soil enzyme activities. SUMs also reduced the accumulation of harmful Cd in rice grains and transformed it into FeMn oxidized Cd, organic-bound Cd, and residual Cd in rhizosphere soil. This was partly due to the higher degree of soil DOM aromatization, which helped complex the Cd with DOM. Additionally, the study also found that microbial activity was the primary source of soil DOM, and that SUMs increased the diversity of soil microbes and recruited many beneficial microbes (Arthrobacter, Candidatus_Solibacter, Bryobacter, Bradyrhizobium, and Flavisolibacter) associated with organic matter decomposition, plant growth promotion, and pathogen inhibition. Besides, special taxa (Bradyyrhizobium and Thermodesulfovibrio) involved in sulfate/sulfur ion generation and nitrate/nitrite reduction pathway were observably enriched, which effectively reduced the soil Cd bioavailability through adsorption and co-precipitation. Therefore, SUMs not only changed the soil physicochemical properties (e.g., pH), but also drove rhizosphere microbes to participate in the chemical species transformation of soil Cd, thus reducing Cd accumulation in rice grains.

Role of the surface characteristics of hyper-crosslinked polymers on the transformation of adsorbed trichlorophenol: Implications for understanding the surface reactivity of biochar derived from waste biomass

The surface reactivity of biochar derived from waste biomass has not been well understood due to its complex composition and heterogeneity. Therefore, this study synthesized a series of biochar-like hyper-crosslinked polymers (HCPs) with different amounts of phenolic hydroxyl groups on the surface as an indicative tool to investigate the roles of key surface properties of biochar on transforming pollutants being adsorbed. Characterization of HCPs suggested that electron donating capacity (EDC) of different HCPs was positively correlated with increasing amounts of phenol hydroxyl groups, whereas specific surface area, degree of aromatization and graphitization were negatively correlated. It was found that greater amounts of hydroxyl radicals were produced with increasing amounts of hydroxyl groups on the synthesized HCPs. Batch degradation experiments with trichlorophenols (TCPs) suggested that all HCPs could decompose TCP molecules upon contact. The degree of TCP degradation (~45 %) was highest for HCP made from benzene monomer with the lowest amounts of hydroxyl groups, which was likely driven by its greater specific surface area and reactive sites for TCP degradation. Conversely, the degree of TCP degradation (~25 %) by HCPs with the highest hydroxyl group abundance was the lowest, probably because the lower surface area of HCPs had limited TCP adsorption, which led to lower interaction between HCP surface and TCP molecules. The results concluded from the contact of HCPs and TCP suggested both EDC and adsorption capacity of biochar played critical roles in transforming organic pollutants.

Using floating photocatalyst mpg-C3N4/expanded perlite to treat natural organic matter under visible light

In-situ application of powdered photocatalysts in water systems is particularly challenging owing to intrinsic hurdles, such as submersion in water without stirring, limited light penetration, limited material recovery, and metal-leaking from the metallic materials used. In this study, a floating mpg-C3N4/extended perlite (EP) photocatalyst was synthesized and applied for the first time in the treatment of natural organic matter (NOM) under visible light, overcoming the majority of limitations of conventional powdered photocatalysts. With the addition of 0.8 mM H2O2, the mpg-C3N4/EP photocatalytic system generated active species ·OH and ·O2−, and removed 41.8 ± 1.3% of the starting NOM at 2 g L−1 after 5 h of operation. Fluorescence measurements revealed a pronounced adsorption affinity of the photocatalyst and more effective destruction of NOM towards its constituents with higher degrees of aromaticity and functionalization. This was accompanied by the production of low-molecular-weight phenolic structures as a result of the incomplete mineralization of humic-like substances. Significant correlations between two fluorescent components (i.e., C1 and C2) and dissolved organic carbon were found, suggesting that the identified components could be utilized as reliable optical surrogates for monitoring the decomposition of the heterogeneous NOM by photocatalysis using floating mpg-C3N4/EP. Some of the advantages of the floating mpg-C3N4/EP complex over conventional powdered mpg-C3N4 for NOM treatment were: easy recovery, high performance without interference from common anions, and low dependency on stirring. Finally, the simple procedure to synthesize mpg-C3N4/EP facilitates its prospective industrial applications on a large scale.

Catalytic Hydrotreatment of Algal HTL Bio‐Oil over Phosphide, Nitride, and Sulfide Catalysts

AbstractGlobal energy demand and environmental concerns about limiting CO2 emissions have been growing recently. This is why fuel production from renewable resources has become a priority. In this context, microalgae represent an attractive alternative carbon source. In this work, different supported catalysts, including metal phosphide, nitride, and sulfide, were tested for the hydroconversion of bio‐oil issued from the hydrothermal liquefaction of microalgae. Supported Ni phosphide catalysts promoted the decarboxylation and decarbonylation route, while NiMo nitride promoted the hydrodeoxygenation pathway. NiW sulfide catalysts were the most performant, producing a hydrotreated oil with the best higher heating value (HHV), lower aromaticity degree, and lower average molar mass. Among sulfide catalysts, NiWS/SiO2−Al2O3 was the least active, probably due to the inhibition of acid sites by the nitrogen compounds. However, NiWS/Al2O3 performed better, showing high hydrogenation performances, which contributed to the conversion of refractory compounds.

Decoupling effects of C3H3/C4H5/i-C4H5/CN radicals on the formation and growth of aromatics: A ReaxFF molecular dynamics study

This paper demonstrates the effects of C3H3/C4H5/i-C4H5/CN radicals on the formation and growth of aromatic hydrocarbons, particular types of polycyclic aromatic hydrocarbons (PAHs) such as heavier-PAHs, cyclopentafused PAHs (CP-PAHs), through reactive force field molecular dynamics simulations under 2250K and 2500K. Adding non-acetylene radicals enhanced the early-stage mass growth of aromatics to varying degrees. However, the later-stage mass growth and aromaticity degree were weakened by adding radicals except for the C3H3 radical. The reactivity of acetylene and additional radicals showed that the additional C3H3 radicals accelerated the consumption of radical pools, and the interaction reaction between C3H3 was responsible for the consumption of radical pools for the C3H3 additive case. The consumption of i-C4H5 was significantly faster than that of C4H5, whereas the consumption of acetylene in the two simulation cases was essentially the same. Thus, the i-C4H5 simulation case formed more intermediate species C6H7 than C4H5 radical. As for the formation of less-studied PAHs, i-C4H5 radicals generated more heavier PAHs and CP-PAHs than straight butyl C4H5 isomers. Finally, the effect of nitrogen-containing radical CN, which normally resides in ammonia fuel, was analyzed. Several factors explained the stronger enhancement in aromatic mass growth, but the relatively lowest aromatization degree resulted from the additional CN radicals. The reactions between CN and acetylene formed carbon–nitrogen species that participated less in the formation and growth of aromatics. The potential reactions between CN radical and aromatics led to ring-opening reactions and the formation of nitrogen-membered rings, which accelerated the mass growth of carbon clusters but inhibited the development of aromaticity degree. The least amount of CP-PAHs was found in CN cases compared with hydrocarbon radical cases.

Synthesis and Chemistry of 1,2,4,3-Triazaphosphole Derivatives

Abstract: This review describes the progress made during the last fifty years in the synthesis and chemistry of 1,2,4,3 triazaphospholes. This class of compounds has attracted tremendous homogeneous catalysis and interest in molecular materials science. These fascinating phosphorus heterocycles have conjugated π systems with high degrees of aromaticity. 1,2,4,3- Triazaphospholes can be designed through [3+2] cyclocondensation between functionalized hydrazines with phosphonoimidates that allow the incorporation of additional donor substituents into specific positions of the phosphorus heterocycle. In addition, [4+1] cyclocondensation between functionalized amidrazones and active phosphorus reagents is the most synthetically accessible method. The used strategies facilitated synthetic access to a completely new set of triazaphospholes leading to a much broader scope for potential applications. 1,2,4,3-triazaphospholes displayed reactivity towards a variety of reagents. The phosphorus is particularly prone to undergo oxidative 1,1-addition. Protic reagents such as alcohols, phenols, and amines can be added across the P=N bond of 2H-1,2,4,3-triazaphospholes to yield the dihydro-1,2,4,3-triazaphosphole derivatives. 1H- and 2H-1,2,4,3- triazaphospholes reacted with alcohols, ammonia and amines in the presence of sulfur or selenium to form dihydro- 1,2,4,3-triazaphosphole 3-chalcogenides. The appropriate difunctional reagents such as glycols, 2-azido alcohols and phenol with a heterodiene function in the ortho position reacted with 2H-1,2,4,3-triazaphospholes to yield products formed via 1,2-addition on P=N bond. Similar behavior is shown by 2-hydroxyacetophenone and 2- hydroxy-benzophenone. 2H-1,2,4,3-Triazaphospholes reacted with acetylenes to form [3+2] cycloadducts; the latter change to 1,2,3-diazaphospholes. [4+1] Cycloadditions occurred with α-diimines, azodicarboxylic esters, and 1,2-diketones; in the latter two cases, the resulting products dimerize.

Applying the core-satellite species concept: Characteristics of rare and common riverine dissolved organic matter

IntroductionDissolved organic matter (DOM) composition varies over space and time, with a multitude of factors driving the presence or absence of each compound found in the complex DOM mixture. Compounds ubiquitously present across a wide range of river systems (hereafter termed core compounds) may differ in chemical composition and reactivity from compounds present in only a few settings (hereafter termed satellite compounds). Here, we investigated the spatial patterns in DOM molecular formulae presence (occupancy) in surface water and sediments across 97 river corridors at a continental scale using the “Worldwide Hydrobiogeochemical Observation Network for Dynamic River Systems—WHONDRS” research consortium.MethodsWe used a novel data-driven approach to identify core and satellite compounds and compared their molecular properties identified with Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS).ResultsWe found that core compounds clustered around intermediate hydrogen/carbon and oxygen/carbon ratios across both sediment and surface water samples, whereas the satellite compounds varied widely in their elemental composition. Within surface water samples, core compounds were dominated by lignin-like formulae, whereas protein-like formulae dominated the core pool in sediment samples. In contrast, satellite molecular formulae were more evenly distributed between compound classes in both sediment and water molecules. Core compounds found in both sediment and water exhibited lower molecular mass, lower oxidation state, and a higher degree of aromaticity, and were inferred to be more persistent than global satellite compounds. Higher putative biochemical transformations were found in core than satellite compounds, suggesting that the core pool was more processed.DiscussionThe observed differences in chemical properties of core and satellite compounds point to potential differences in their sources and contribution to DOM processing in river corridors. Overall, our work points to the potential of data-driven approaches separating rare and common compounds to reduce some of the complexity inherent in studying riverine DOM.

Hydrothermal carbonization coupled with gasification for collaborative disposal of kitchen waste and yard waste

Kitchen waste and yard waste are typical components of municipal solid waste. In this paper, two schemes for collaborative disposal of these two wastes by hydrothermal carbonization (HTC) coupled with gasification were proposed and compared: Scheme 1: co-gasification of poplar with hydrochar derived from food waste; Scheme 2: direct gasification of hydrochar derived from co-HTC process of food waste and poplar. HTC was the pretreatment to regulate the composition and structure of raw materials. After HTC, the H/C and O/C of food waste decreased to the minimum of 1.06 and 0.14, respectively, and the coalification degree was increased close to lignite. Most of K and Na would be removed but Ca was enriched during HTC process, in which hydrochar derived from food waste at 260 °C contained the highest Ca content of 3752.30 mg/kg. The C=C and C=O functional groups of hydrochar were richer than the raw materials indicating the aromatization degree was improved. In Scheme 1, the gasification feedstock had relatively higher alkali and alkaline earth metals and volatile, resulting in a rapid gasification and the H2/CO ratio was between 1.6 and 1.8. In Scheme 2, the co-HTC hydrochar had high content of fixed carbon which can reach the maximum of 48.62 wt.% when the temperature was 260 °C. Due to the richer surface functional group structure, especially C=O, the hydrochar was easy to crack into CO during the initial gasification stage, and H2/CO ratios of the syngas were all less than 1. HTC coupled with gasification could broad the waste usage to meet the different industrial process needs, which can achieve waste disposal and energy conversion efficiently.

Influence of torrefaction with microwave and furnace heating on pyrolysis of poplar sawdust

Microwave heating is different from furnace heating in terms of heat transfer direction and heating mechanism. The torrefaction with microwave or furnace heating might further impact evolution of the pyrolytic products in further pyrolysis. This was investigated herein via thermal pretreatment of sawdust at 150 to 250 °C and the subsequent pyrolysis at 600 °C. The results showed that the microwave pretreatment led to more pronounced pyrolysis at 200/250 °C, which enhanced aromatic degree of semi-char and created difficulty for its further cracking in pyrolysis at 600 °C but not affected gasification. This led to the formation of more biochar and much more gases but less bio-oil with less heavy components than that from furnace heating plus pyrolysis. Additionally, the microwave pretreatment could enhance deoxygenation but the enhanced aromatic degree of the semi-char created difficulty for creating micropores and development of the pore structures (176.2 m2g−1 with 67.3% micropores from microwave pretreatment versus 441.1 m2g−1 with 78.5% micropores from furnace pretreatment). The characterization of the pyrolysis of semi-char with in-situ IR technique confirmed that the microwave pretreatment substantially removed the aliphatic structures and made the biochar with more fragmented morphology.

Study on the Occurrence Difference of Functional Groups in Coals with Different Metamorphic Degrees.

In order to quantitatively study the difference in occurrence content of functional groups in coals with different metamorphic degrees, the samples of long flame coal, coking coal, and anthracite of three different coal ranks were characterized by FTIR and the relative content of various functional groups in different coal ranks was obtained. The semi-quantitative structural parameters were calculated, and the evolution law of the chemical structure of the coal body was given. The results show that with the increase in the metamorphic degree, the substitution degree of hydrogen atoms on the benzene ring in the aromatic group increases with the increase in the vitrinite reflectance. With the increase in coal rank, the content of phenolic hydroxyl, carboxyl, carbonyl, and other active oxygen-containing groups gradually decreased, and the content of ether bonds gradually increased. Methyl content increased rapidly first and then increased slowly, methylene content increased slowly first and then decreased rapidly, and methylene content decreased first and then increased. With the increase in vitrinite reflectance, the OH-π hydrogen bond gradually increases, the content of hydroxyl self-association hydrogen bond first increases and then decreases, the oxygen-hydrogen bond of hydroxyl ether gradually increases, and the ring hydrogen bond first significantly decreases and then slowly increases. The content of the OH-N hydrogen bond is in direct proportion to the content of nitrogen in coal molecules. It can be seen from the semi-quantitative structural parameters that with the increase in coal rank, the aromatic carbon ratio fa, aromatic degree AR and condensation degree DOC increase gradually. With the increase in coal rank, A(CH2)/A(CH3) first decreases and then increases, hydrocarbon generation potential 'A' first increases and then decreases, maturity 'C' first decreases rapidly and then decreases slowly, and factor D gradually decreases. This paper is valuable for analyzing the occurrence form of functional groups in different coal ranks and clarifying the evolution process of structure in China.

Degradation of refractory organic matter in MBR effluent from treating landfill leachate by the UV-nZVI-H2O2 system.

In this study, nano zero-valent iron (nZVI) was used as the Fe2+ source in the Fenton reaction, and a UV-nZVI-H2O2 system was constructed to efficiently degrade and mineralize refractory organic matter in landfill leachate. The results showed that under the optimal conditions (initial pH = 3, UV = 14W, nZVI = 0.5g/L, and [H2O2] = 30mM), the removal efficiencies of total organic carbon, absorbance at 254nm, and color number were 61.38%, 83.89%, and 85.79%, respectively. Control experiments show that the UV-nZVI-H2O2 system has the highest removal rate and mineralization rate of refractory organic matter. The excellent performance of the UV-nZVI-H2O2 system is related to a higher H2O2 utilization rate. The H2O2 residue in the UV-nZVI-H2O2 system was the lowest, and the effective utilization rate of H2O2 was as high as 98.80%. Alcohol quenching experiments and hydroxyl radical quantitative experiments showed that the dominant reactive oxygen species in the UV-nZVI-H2O2 system was HO• and the yield of HO• was as high as 2007.80μM, which was much higher than that in other systems. The results of spectra analysis showed that the low molecular weight, high fluorescence frequency organic matter, and relatively stable aromatic organic matter were significantly degraded after treatment with the UV-nZVI-H2O2 system and the aromatic degree, humification degree, molecular weight, and molecular polymerization degree of refractory organic matter were also significantly decreased. The mechanism of the UV-nZVI-H2O2 reaction includes homogeneous and heterogeneous Fenton reactions and adsorption and precipitation of organic matter by iron-based colloids. This study can provide theoretical and technical support for the advanced treatment of refractory organic matter in landfill leachate.