Unsaturated Aliphatic Compounds Research Articles

The loss of dissolved organic matter from biological soil crust at various successional stages under rainfall of different intensities: Insights into the changes of molecular components at different rainfall stages

Biological soil crusts (BSCs) are typical covers in arid and semiarid regions. The dissolved organic matter (DOM) of BSCs can be transported to various aquatic ecosystems by rainfall-runoff processes. However, the spatiotemporal variation in quality and quantity of DOM in runoff remains unclear. Herein, four kinds of runoff plots covered by four successional stages of BSCs were set up on slopes, including bare runoff plot (BR), cyanobacteria crust covered runoff plot (CR), mixed crust covered runoff plot (MIR), and moss crust covered runoff plot (MOR). The quantity and quality of DOM in runoff during rainfall was investigated based on the stimulated rainfall experiments combined with optical spectroscopy and ultra-high resolution mass spectrometry analyses. The results showed that the DOM concentrations (i.e., 0.30 to 45.25 mg L−1) in runoff followed the pattern of MOR>MIR>CR>BR, and they were exponentially decreased with rainfall duration. The DOM loss rate of BR (8.26 to 11.64 %) was significantly greater than those of CR, MIR, and MOR (0.84 to 3.22 %). Highly unsaturated compounds (HUCs), unsaturated aliphatic compounds (UACs), saturated compounds (SCs), and peptide-like compounds (PLCs) were the dominated compounds of the water extractable DOM from the original soils. Thereinto, PLCs and UACs were more easily leached into runoff during rainfall. The relatively intensity of HUCs in runoff generally decreased with rainfall duration, while the relatively intensities of UACs, PLCs, and SCs slightly increased with rainfall duration. These findings suggested that the DOM loss rate was effectively decreased with the successional of BSCs during rainfall; meanwhile, some labile compounds (e.g., PLCs and UACs) were transported into various aquatic ecosystems by rainfall-runoff processes.

Reduced sulfur compounds and carboxylic acid groups in dissolved PFRs of iron-biochar enhance Cr(VI) reduction in anaerobic conditions

In addition to the adsorption and immobilization capacities of iron-modified biochars, these materials produce persistent free radicals (PFRs) that can carry out metal [i.e., Cr(VI)] redox transformations, but the primary forms and active species of PFRs involved are not well understood. Here, we investigated the key species of PFRs of α-Fe2O3-modified biochar (MBC) and their influence on Cr(VI) reduction under anaerobic conditions simulating paddy soil environments. MBC produced bulk phenoxyl PFRs that promoted Cr(VI) reduction due to the catalytic effect of the transition metal Fe. In addition, MBC was more efficient in reducing Cr(VI) under anaerobic conditions than under aerobic conditions due to the more active and accessible dissolved PFRs present in the dissolved organic matter (DOM). The electron transfer capacity of DOM was demonstrated by excitation-emission matrix (EEM) spectrophotometry combined with parallel factor analysis, which showed that the protein-like and humic-like components of DOM were involved in Cr(VI) reduction. Furthermore, Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) analysis indicated that reduced-S compounds (O/S < 4) and carboxylic acid (–COO) groups in the unsaturated aliphatic and lignin-like compounds are potentially the main active species accelerating Cr(VI) reduction under anaerobic conditions. Our results provide new insights into the role of dissolved PFRs from iron-modified biochar in promoting Cr(VI) reduction under anaerobic conditions such as flooded soils.Graphical

Molecular characteristics of organic matter derived from sulfonated biochar.

Sulfonated biochar (SBC), as a functional carbon-based material, has attracted widespread attention due to its excellent adsorption properties. The composition of biochar-derived organic matter (B-DOM) is a key factor influencing the migration and transformation of soil elements and pollutants. However, molecular characteristics of sulfonated biochar-derived organic matter (SBC-DOM) are still unclear. In this study, the molecular composition of derived organic matter (DOM) from SBC prepared via one-step carbonization-sulfonation techniques was investigated by Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and then compared with those of DOMs from rice husk (RH), pyrochar (PYC), and hydrochar (HYC). The results show that the CHOS- and CHONS-containing formulae are predominant in SBC-DOM, accounting for 85% of the total molecular formula number, while DOMs from RH, PYC, and HYC are dominated by CHO-containing formulae. Compared to PYC-DOM and HYC-DOM, SBC-DOM has more unsaturated aliphatic compounds, which make it more labile and easily biodegraded. Additionally, SBC-DOM has higher O/C, (N + O)/C ratios and sulfur-containing compounds. These findings provide a theoretical basis for further research on the application of sulfonated biochar in soil improvement and remediation.

Molecular insight of dissolved organic matter and chlorinated disinfection by-products in reclaimed water during chlorination with permanganate preoxidation

Permanganate is a common preoxidant applied in water treatment to remove organic pollutants and to reduce the formation of disinfection by-products. However, the effect of permanganate preoxidation on the transformation of dissolved effluent organic matter (dEfOM) and on the formation of unknown chlorinated disinfection by-products (Cl-DBPs) during chlorination remains unknown at molecular level. In this work, the molecular changes of dEfOM during permanganate preoxidation and subsequent chlorination were characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Permanganate preoxidation was found to decrease the DBE (double bond equivalent) and AImod (modified aromaticity index) of the dEfOM. The identity and fate of over 400 unknown Cl-DBPs during KMnO4-chlorine treatment were investigated. Most Cl-DBPs and the precursors were found to be highly unsaturated aliphatic and phenolic compounds. The Cl-DBPs precursors with lower H/C and lower O/C were preferentially removed by permanganate preoxidation. Additionally, permanganate preoxidation decreased the number of unknown Cl-DBPs by 30% and intensity of unknown Cl-DBPs by 25%. One-chlorine-containing DBPs were the major Cl-DBPs and had more CH2 groups and higher DBEw than Cl-DBPs containing two and three chlorine atoms. 60% of the Cl-DBPs formation was attributed to substitution reactions (i.e., +Cl–H, +2Cl–2H, +3Cl–3H, +ClO–H, +Cl2O3–2H). This work provides detailed molecular level information on the efficacy of permanganate preoxidation on the control of overall Cl-DBPs formation during chlorination.

Comparative molecular transformations of dissolved organic matter induced by chlorination and ammonia/chlorine oxidation process

The ammonia/chlorine oxidation process can greatly degrade PPCPs in water. However, its effect on molecular transformations of natural organic matter (NOM) and effluent organic matter (EfOM) are still poorly understood. In this study, molecular transformations of NOM and EfOM occurring during ammonia/chlorine were explored and compared with those occurred during chlorination, using spectroscopy and mass spectrometry. Phenolic and highly unsaturated aliphatic compounds together with aliphatic compounds were found to be predominant in both NOM and EfOM samples, all of which were significantly degraded after two processes. The ammonia/chlorine process led to greater decreases in the molecular weights of such components but lower reductions in aromaticity. Compared with chlorination, ammonia/chlorine was found to be more likely to degrade compounds while remaining fluorophores or chromophores. The CH(N)O(S) precursors were found to be similar for both processes but their products were quite different. The CH(N)O(S) precursors that only found in ammonia/chlorine had higher molecular weights and greater degrees of oxidation but lower degrees of saturation. In contrast, the unique CH(N)O(S) products that only found in ammonia/chlorine exhibited lower molecular weights and lower degrees of oxidation degrees together with higher degrees of saturation. Lower total abundance of chlorinated byproducts was found by ammonia/chlorine compared with chlorination, although the former process provided a richer diversity. In all water samples, chlorinated byproducts were mainly generated by substitution reactions during ammonia/chlorine and chlorination. Overall, the findings of this study could provide new insights into the transformations of NOM and EfOM induced by ammonia/chlorine and chlorination.

Hypoxia diversifies molecular composition of dissolved organic matter and enhances preservation of terrestrial organic carbon in the Yangtze River Estuary

Dissolved organic matter (DOM) is an essential component of the global carbon cycle, and estuaries link the rivers and the oceans, thus playing important roles in land-ocean DOM transformation and transport. However, the effects of hypoxia on DOM transport and fate in estuaries and coastal oceans remains poorly understood. To address this gap, we characterized the molecular composition of DOM in bottom water (BW) and sediment porewater (PW) at hypoxic and non-hypoxic sites in the Yangtze River Estuary (YRE) using ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry. Our results showed significant differences in DOM molecular composition between hypoxic and non-hypoxic areas for both BW and PW. Specifically, DOM in hypoxic sites was more recalcitrant than that in non-hypoxic areas for both BW and PW, with lower H/C, and higher O/C, double bond equivalent, and modified aromaticity index. The presence of higher polyphenols, and black carbon in hypoxic areas suggested that hypoxic conditions could facilitate the preservation of terrestrial organic matter. Furthermore, we identified a much higher number of hypoxia-unique formulas than ocean-non-hypoxia-unique formulas, indicating that hypoxia could diversify the DOM pool. Within hypoxia-unique formulas for PW, both biologically labile (unsaturated aliphatic compounds and peptides) and recalcitrant formulas (carboxyl-rich alicyclic molecules) were found, suggesting that hypoxia could facilitate the preservation of labile formulas and the production of recalcitrant formulas. In addition, we formulated that the sulfurization is more important in PW than BW in hypoxic areas based on the higher dissolved organic sulfur (DOS) abundance and larger number of hypoxia-only formulas in hypoxic PW, and also the precursor analysis results. Overall, our study provides insights into the effect of hypoxia on the molecular characteristics and preservation of DOM in estuaries and coastal oceans, highlighting the importance of considering hypoxia in understanding the biogeochemical processes of these ecosystems.

Coupled Processes Involving Organic Matter and Fe Oxyhydroxides Control Geogenic Phosphorus Enrichment in Groundwater Systems: New Evidence from FT-ICR-MS and XANES.

The enrichment of geogenic phosphorus (P) in groundwater systems threatens environmental and public health worldwide. Two significant factors affecting geogenic P enrichment include organic matter (OM) and Fe (oxyhydr)oxide (FeOOH). However, due to variable reactivities of OM and FeOOH, variable strategies of their coupled influence controlling P enrichment in groundwater systems remain elusive. This research reveals that when the depositional environment is enriched in more labile aliphatic OM, its fermentation is coupled with the reductive dissolution of both amorphous and crystalline FeOOHs. When the depositional environment is enriched in more recalcitrant aromatic OM, it largely relies on crystalline FeOOH acting concurrently as electron acceptors while serving as "conduits" to help itself stimulate degradation and methanogenesis. The main source of geogenic P enriched by these two different coupled processes is different: the former is P-containing OM, which mainly contained unsaturated aliphatic compounds and highly unsaturated-low O compounds, and the latter is P associated with crystalline FeOOH. In addition, geological setting affects the deposition rate of sediments, which can alter OM degradation/preservation, and subsequently affects geochemical conditions of geogenic P occurrence. These findings provide new evidence and perspectives for understanding the hydro(bio)geochemical processes controlling geogenic P enrichment in alluvial-lacustrine aquifer systems.

Effects of dissolved organic matter from sediment and soil samples on the growth and physiology of four bloom-forming algal species

Algal blooms negatively impact the water quality of reservoirs; however, the role of dissolved organic matter (DOM) in bloom formation in reservoirs has not been investigated. Therefore, we assessed the compositions of sediment- and soil-derived DOM and their effects on the growth, physiology, and photosynthetic activity of Microcystis aeruginosa, Anabaena sp., Chlamydomonas sp., and Peridiniopsis sp. (bloom-forming species). Sediment DOM promoted the growth of all algal species, whereas soil DOM significantly promoted the growth of Chlamydomonas sp. and Peridiniopsis sp.; this effect was due to enhanced stress tolerance and photosynthetic efficiency exhibited by these algae under DOM treatment. However, soil DOM slightly inhibited the growth of Anabaena sp. by increasing reactive oxygen species levels and inactivating some photosystem II reaction centers. The tyrosine-like substance, humic acid-like substances, and unsaturated aliphatic compounds were the main DOM components that affected algal growth. The findings of this study will provide a theoretical foundation for the development of bloom-prevention strategies for river-type reservoirs.

The nature of carbon deposits and their formation pathways during catalytic supercritical water gasification of glycerol

Supercritical water gasification (SCWG) is a promising technology to convert wet biomass to renewable natural gas. The present study sheds light on the chemical composition and the formation mechanism of coke deposits on a Ru/CNF catalyst during continuous SCWG of glycerol in a fixed-bed reactor. SCWG experiments were performed using pristine carbon nanofibers (CNF) and 5 wt% Ru/CNF catalysts, which suffered from partial deactivation. Transmission electron microscopy (TEM) indicated a 34–42 % dispersion loss independently of the conditions, only partially explaining the activity loss observed during the test at very high space velocity. When operated under thermodynamic conditions, no deposits could be observed. A nanometric layer of deposits on the catalysts was present under intermediate conditions, while in the kinetic regime (conversion of glycerol down to 4 %), significant carbon deposition was observed. The chemical compositions of aqueous phases and organic deposits extracted from the catalysts and support showed that the presence of Ru enhanced the formation of unsaturated compounds from glycerol. In particular, molecules containing aromatic rings were detected. The space velocity significantly affected the composition of the coke deposits. The number of carbons in the molecules increased from 5–25 to 10–45 when moving away from the thermodynamic regime (full conversion), and the O/C ratio significantly decreased from 0.3–0.6 to 0.05–0.3, maintaining a very broad H/C ratio. The extracted organic deposits contained various aromatic compounds but were mostly represented by unsaturated aliphatic compounds. All these results were used to elucidate a reaction pathway for the formation of organic deposits from glycerol.

Reduction of byproduct formation and cytotoxicity to mammalian cells during post-chlorination by the combined pretreatment of ferrate(VI) and biochar

Ferrate [Fe(VI)] can efficiently degrade various pollutants in wastewater. Biochar application can reduce resource use and waste emission. This study investigated the performance of Fe(VI)/biochar pretreatment to reduce disinfection byproducts (DBPs) and cytotoxicity to mammalian cells of wastewater during post-chlorination. Fe(VI)/biochar was more effective at inhibiting the cytotoxicity formation than Fe(VI) alone, reducing the cytotoxicity from 12.7 to 7.6 mg-phenol/L. The concentrations of total organic chlorine and total organic bromine decreased from 277 to 130 μg/L and from 51 to 39 μg/L, compared to the samples without pretreatment. Orbitrap ultra-high resolution mass spectrometry revealed that the number of molecules of DBPs decreased substantially from 517 to 229 by Fe(VI)/biochar, with the greatest reduction for phenols and highly unsaturated aliphatic compounds. In combination with the substantial reduction of 1Cl-DBPs and 2Cl-DBPs, 1Br-DBPs and 2Br-DBPs were also reduced. Fluorescence excitation-emission matrix coupled with parallel factor analysis suggested that fulvic acid-like substances and aromatic amino acid was obviously reduce likely due to the enhanced oxidation of Fe(IV)/Fe(V) produced by Fe(VI)/biochar and adsorption of biochar. Furthermore, the DBPs generated by electrophilic addition and electrophilic substitution of precursors were reduced. This study shows that Fe(VI)/biochar pretreatment can effectively reduce cytotoxicity formation during post-chlorination by transforming DBPs and their precursors.

Adsorbing Volatile Organic Compounds within Bitumen Improves Colloidal Stability and Air Quality

The mass loss of bitumen due to volatilization is one of the deterioration mechanisms through which the chemical composition of bitumen deviates from its original condition, leading to change in the physical and rheological properties of bitumen. The emissions from bitumen not only accelerate its aging but also negatively impact air quality and consequently human health. Here, we characterized the molecular compositions of the volatiles emitted from bitumen in an isothermal aging process (150 °C for 24 h). We also investigated the impact of losing these compounds on the association behavior of asphaltene stacks. Based on the GC-MS results, the main mass loss of SARA (saturates, aromatics, resins, asphaltenes) fractions is attributed to the emission of lightweight nonpolar aromatic and aliphatic compounds. The most dominant volatiles are single-ring aromatics carrying short side chains, followed by saturated and unsaturated aliphatic compounds including short-chain n-alkanes, iso-alkanes, cyclic alkenes, alkenes, and dienes. Using molecular modeling in the framework of density functional theory (DFT), we showed how the reduction in aromatics and saturates can impact the colloidal stability of asphaltenes in the matrix of bitumen. Based on the DFT results, the surface adsorption of aromatics and saturates on asphaltene planes provides the steric repulsion required to maintain the asphaltene planes at a distance sufficient to inhibit their agglomeration. In addition, aromatic molecules with the least hindrance repulsion can disturb the π–π interfacial interactions between asphaltene planes, facilitating their deagglomeration. Therefore, a direct consequence of the mass loss of bitumen due to volatilization is disturbing the asphaltene distribution within the bitumen and stimulating the aggregation of asphaltenes. We also studied the merits of incorporating biochar into the bitumen surface to reduce bitumen’s mass loss. Modification of bitumen separately with each of six biochars derived from biomass feedstocks (walnut shell, peanut shell, Douglas fir, pine bark, birch, and algae) showed the efficacy of each biochar to reduce the volatiles emitted from bitumen, thereby reducing the changes in the composition of maltene with consequent colloidal stability losses. The study outcomes highlight the importance of reducing emissions from bitumen to delay its aging and minimize negative impacts on air quality and human health.

Effects of dissolved organic matter derived from two herbs on the growth, physiology, and physico-chemical characteristics of four bloom-forming algae species

While algal blooms occur frequently in lakes and reservoirs worldwide, the effects of dissolved organic matter (DOM) from lakeside and riparian zones on bloom formation are not well understood. In this study, we characterized the molecular composition of DOM from Cynodon dactylon (L.) Pers. (CD-DOM) and Xanthium sibiricum Patrin ex Widder (XS-DOM) and assessed their effects on the growth, physiology, volatile organic compounds (VOCs), and stable carbon isotope in four bloom-forming algae species (Microcystis aeruginosa, Anabaena sp., Chlamydomonas sp., and Peridiniopsis sp.). Stable carbon isotope analysis showed that the four species were affected by DOM. Both DOM types increased the cell biomass, polysaccharide and protein contents, chlorophyll fluorescence parameter values, and VOCs release of Anabaena sp., Chlamydomonas sp. and Microcystis aeruginosa, suggesting that DOM stimulated algal growth by increasing nutrient sources, photosynthetic efficiency, and stress tolerance. And in general, these three strains exhibited better growth at higher DOM concentrations. However, DOM treatment inhibited the growth of Peridiniopsis sp., as indicated by the increases in reactive oxygen species, damage in photosystem II reaction centers, and blockage in electron transport. Fluorescence analysis showed that tryptophan-like compounds were the main DOM components that affected algal growth. Molecular-level analysis suggested that unsaturated aliphatic compounds may be the most important DOM components. The findings indicate that CD-DOM and XS-DOM promote the blue-green algal blooms formation and thus should be considered in the management of natural water quality.

Molecular evidence for the production of labile, sulfur-bearing dissolved organic matter in the seep sediments of the South China Sea

Cold seeps with methane-rich fluids leaking out of the seafloor usually support massive biomass of chemosynthetic organisms and associated fauna. A substantial amount of methane is converted to dissolved inorganic carbon by microbial metabolism, and this process also releases dissolved organic matter (DOM) into pore water. Here, pore water samples from “Haima cold seeps” sediments and the non-seep reference sediments in the northern South China Sea were analyzed for optical properties and molecular compositions of pore water DOM. Our results showed that the relative abundance of protein-like DOM, H/Cwa and molecular lability boundary percentage (MLBL%) in the seep sediments were significantly higher than those in the reference sediments, indicating that more labile DOM related to unsaturated aliphatic compounds is produced in the seep sediments. Spearman's correlation of the fluoresce and molecular data suggested that the humic-like components (C1 and C2) mainly constituted the refractory compounds (CRAM, highly unsaturated and aromatics compounds). In contrast, the protein-like component (C3) had high H/C ratios featuring high degree of DOM lability. The amount of S-containing formulas (CHOS and CHONS) was greatly elevated in the seep sediments, likely caused by abiotic and biotic sulfurization of DOM in the sulfidic environment. Although the abiotic sulfurization was proposed to have a stabilizing effect on organic matter, our results implied that the biotic sulfurization in the cold seep sediments would increase DOM lability. Overall, the labile DOM accumulated in the seep sediments is closely linked to methane oxidation, which not only support heterotrophic communities and but also likely have an impact on carbon and sulfur cycling in the sediments and the ocean.

Volatile Organic Compound Profiles of Cystoseira corniculata (Turner) Zanardini 1841 and Ericaria amentacea (C.Agardh) Molinari and Guiry 2020 (ex. Cystoseira amentacea (C.Agardh) Bory de Saint-Vincent, 1832).

The volatile organic compounds (VOCs) of fresh (FrCC) and air-dried (DrCC) Cystoseria corniculata and fresh (FrEA) and air-dried (DrEA) Ericaria amentacea from the Adriatic Sea were investigated by headspace solid-phase microextraction (HS-SPME) and hydrodistillation (HD) and analysed by gas chromatography and mass spectrometry (GC-MS). In HS-FrCC and HS-DrCC, aliphatic compounds were dominant, with decan-5-ol as the most abundant in HS-FrCC, but in HS-DrCC pentadecane dominated. Monoterpenes (β-cyclocitral, β-citral, and β-cyclohomocitral) and sesquiterpenes (cubenol) were abundant in HS-FrCC. Notable differences between fresh and air-dried samples were found for benzene derivatives. Fatty acids and their derivatives were the most abundant in HD-FrCC and HD-DrCC. In HS-FrEA and HS-DrEA, saturated aliphatic compounds as well as unsaturated aliphatic compounds (particularly hexan-1-ol and (Z)-hex-3-en-1-ol) predominantly showed decrements after drying. Pentadecane, heptadecane, pentadecanal, and hexan-1-ol were predominant in HD-FrEA, and their percentage decreased in HD-DrEA. The percentage of monoterpenes decreased after drying, but the percentages of diterpenes and especially sesquiterpenes increased. δ-Selinene was the major terpene and the most abundant in HD-DrEA. A significant increment after drying could be noticed for fatty acids and their derivatives. The great diversity of identified VOCs among these two macroalgae supports their different botanical classifications.

Detailed Chemical Prospecting of Volatile Organic Compounds Variations from Adriatic Macroalga Halopteris scoparia.

The present study aimed to isolate volatile organic compounds (VOCs) from fresh (FrHSc) and air-dried (DrHSc) Halopteris scoparia (from the Adriatic Sea) by headspace solid-phase microextraction (HS-SPME) and hydrodistillation (HD) and to analyse them by gas chromatography and mass spectrometry (GC–MS). The impact of the season of growth (May–September) and air-drying on VOC composition was studied for the first time, and the obtained data were elaborated by principal component analysis (PCA). The most abundant headspace compounds were benzaldehyde, pentadecane (a chemical marker of brown macroalgae), and pentadec-1-ene. Benzaldehyde abundance decreased after air-drying while an increment of benzyl alcohol after drying was noticed. The percentage of pentadecane and heptadecane increased after drying, while pentadec-1-ene abundance decreased. Octan-1-ol decreased from May to September. In HD-FrHSc, terpenes were the most abundant in June, July, and August, while, in May and September, unsaturated aliphatic compounds were dominant. In HD-DrHSc terpenes, unsaturated and saturated aliphatic compounds dominated. (E)-Phytol was the most abundant compound in HD-FrHSc through all months except September. Its abundance increased from May to August. Two more diterpene alcohols (isopachydictyol A and cembra-4,7,11,15-tetraen-3-ol) and sesquiterpene alcohol gleenol were also detected in high abundance. Among aliphatic compounds, the dominant was pentadec-1-ene with its peak in September, while pentadecane was present with lower abundance. PCA (based on the dominant compound analyses) showed distinct separation of the fresh and dried samples. No correlation was found between compound abundance and temperature change. The results indicate great seasonal variability of isolated VOCs, as well among fresh and dried samples, which is important for further chemical biodiversity studies.

Influence of unsaturated aliphatic and aromatic volatile organic compounds on the oxidation of aqueous sulfur dioxide by oxygen in aqueous medium

The trace atmospheric volatile organic compounds(VOCs) are reported to influence the oxidation of dissolved sulfur dioxide, S(IV), by oxygen, which is an important reaction in atmospheric acid formation. In this work, the influence of 15 VOCs on uncatalyzed oxidation of S(IV) by oxygen has been investigated by following the disappearance of [O2]. The inhibition of oxidation reaction by toluene, aniline, benzene, cinnamic acid, hydroquinone, acrylamide, acrylonitrile and allyl alcohol was defined by the rate law(A):kVOC = k0/(1+B [Inh]) (A)where, kVOC, and k0 are the first order rate constants in the presence and the absence of VOCs respectively. B is the inhibition parameter and [Inh] is the concentration of inhibitor.On the other hand, fumaric, maleic and crotonic acids, which have conjugated CC bonds, catalyze the reaction defined by the rate law(B):kVOC = k0 + kcat [VOC] (B)where kcat is catalytic constant and [VOC] is the concentration of catalytic VOC.Interestingly, presence of 1-hexene, cyclohexene, methacrylic acid, methyl acrylate was without any significant effect on the rate of reaction.

(Digital Presentation) Electrochemical Polymerization of Thiophene in Cholesteric Liquid Crystal with Vitamins

Vitamins are natural compounds which is important for biological reactions. Vitamin C (ascorbic acid) is a water-soluble substance, while Vitamin E (tocopherol) is a soluble material in organic solvents. Further, antioxidant action can affect for metabolism in biological system. Vitamin E has three asymmetric centers in the molecular structure. In the liquid crystal technology, nematic liquid crystal is simple and high fluidity similar to isotopic liquid. Addition of small amount of chiral compounds to nematic liquid crystal can induce cholesteric liquid crystal. This is another chiral and helical version of nematic liquid crystal. In this study, we employed vitamin E as a chiral inducer to nematic liquid crystal for formation of helical liquid crystal system. Electrochemical polymerization is a convenient method for preparation of electroactive polymer deposited on an electrode in the form of thin film. Electrochemical polymerization in LC provides some interesting phenomena. First, electrochemical polymerization in liquid crystal allows the resultant to imprint morphology of molecular aggregation structure from molecular level to macroscopic level of liquid crystal. Second, electrochemical polymerization produces electroactive polymer with dynamically color change upon electrochemical redox process, which character can be applied for electrochemical driven display. Third, electrochemical charge and discharge provides voltaic storage function for the resultant polymer. Thus, electrochemical technique and polymer chemistry, such a brilliant combination produces electro-optic character. Recently, electrochemical polymerization in helical liquid crystal system has been performed. The electrochemical polymerization employs cholesteric liquid crystal as an electrolyte for polymerization. Cholesteric liquid crystal can be prepared by mix of nematic liquid crystal and chiral compounds. We employ synthetic compound as a chiral inducer. Here, we use vitamin E as chiral inducer to nematic liquid crystal preparation of cholesteric liquid crystal electrolyte solution for electrochemical polymerization. Observation of optical texture of the cholesteric liquid crystal electrolyte containing tetrabutylammonium perchlorate (TBAP) as a supporting salt showed fingerprint texture, which is characteristic of cholesteric liquid crystal.Next, electrochemical polymerization in cholesteric liquid crystal induced by vitamin E was carried out. We employed constant voltage electrochemical polymerization to ITO (indium–tin-oxide) coated glass slides were sandwiched via insulator tetrafluoroethylene as a spacer, and the choleretic liquid crystal electrolyte contained monomer (2,2′-bithiophene) was charged with pipette before application of voltage for electrochemical polymerization. The entire polymerization cell was heated to change the liquid crystal to isotropic phase. Then, gradually cooled to room temperature, and the isotopic phase was changed to cholesteric liquid crystal phase with iridescence. After confirming the electrolyte showed liquid crystal phase, constant voltage of 6 V across the sandwiched cell for 60 min was applied. Then, the polymerization cell was de-assembled and washed wish a large volume of organic solvent to remove the liquid crystal electrolyte solution, oligomer, and residual monomer. The polymer film thus prepared was deposited on cathode. This is quite interesting phenomena because electrochemical polymerization is generally occurred at the anode with oxidation. However, this result indicates that electrochemical polymerization in liquid crystal at cathode is possible. Cathodic electrochemical polymerization has been reported for dibromo aromatic compound or unsaturated aliphatic compounds. However, cathodic electrochemical polymerization of aromatic compounds with no halogen group has been few reported.The polymer shows electronic optical transition in visible range due to development of p-conjugated system and absorption at long wave lengths due to doping band accompany by generation on polaron (radical cation). The electrochemical character of the resultant polymer was examined using cyclic voltammetry (CV). The CV measurements were achieved in a monomer-free 0.1-M TBAP−acetonitrile solution at the scan rates of 10 mVs−1. The potential was calculated using a reference of silver/silver ion (Ag/Ag+) electrode. The oxidation and reduction signals are observed during the oxidation and reduction processes. The result showed the resultant polymer has good redox property. The resultant polymer shows no CD signal from short to long wavelengths, indicating no optical activity. However, the polymer shows the similar optical texture to that of liquid crystal electrolyte under the polarizing optical microscopy observations, implying the fingerprint texture of the polymer as macroscopic transcription of the liquid crystal structure may not contribute optical active property. Transcription from liquid crystal environment may not always occurs from molecular level to macroscopic level in the polymerization in liquid crystal. The polymer prepared in this study has no hierarchal structure from molecular level to the higher level, indicating macroscopic morphological imprinting in the polymerization is not essential condition for imprinting from the molecular level.

Effect of propylene in feedstock on the coking behavior of PtSnK/Al2O3 catalyst of propane dehydrogenation

The dehydrogenation of propane was carried out with feed gas containing different proportions of propylene, and the coking behavior of Pt-based catalyst under propene-rich condition was investigated. The results show that the presence of propylene in the raw material accelerates the rate of coke deposition, shortens the time of dynamic equilibrium of coke deposition on the support, and promotes the formation of coke on the surface area of the active phase and the subsequent graphitization. At the same time, the increase the amount of unsaturated aliphatic compounds, thus promoting the generation of aromatic carbon and graphitized carbon, while the catalyst structure is not destroyed. In the process of propane dehydrogenation, the coke “Peak I” appears on the surface of the active phase, and the “Peak II” moves to the high-temperature region, when the propylene content increase to 1.5%. With the alkene content increasing to 3.0%, Peak I and Peak II merge into a larger peak, the area of which increases significantly. When the coke content exceeds 10.26%, the graphitization degree of the catalyst becomes higher and higher. The increase of the propylene content accelerates the saturation process of the coke holding capacity of the carrier, meaning the increasing amount of coke deposit under the same reaction time.

Detailed chemical analysis of a fully formulated oil using dielectric barrier discharge ionisation-mass spectrometry.

RationaleFully formulated oils (FFOs) are integral to automotive lubrication; however, detailed compositional analysis is challenging due to high levels of chemical complexity. In particular, existing mass spectrometric approaches often target particular FFO components, leading to poor analytical coverage of the overall formulation, with increased overheads and analytical timescales.MethodsHerein we report the application of a commercially available SICRIT SC‐20 dielectric barrier discharge ionisation (DBDI) source and Thermo Fisher Scientific LTQ Orbitrap XL to the analysis of an FFO. Nitrogen was used as a discharge gas for the DBDI source, and was modified using a range of commonplace solvents to tailor the experimental conditions for the analysis of various components.ResultsThe reported method allowed analysis of a range of FFO components of interest, encompassing a wide range of chemistries, in under 1 min. By modifying the discharge gas used for ionisation, experiments could be optimised for the analysis of particular FFO components across positive and negative ion modes. In particular, use of water vapour as a discharge gas modifier with positive ion mode mass spectrometry permitted concomitant analysis of antioxidants and base oil hydrocarbons. Furthermore, case studies of selected linear alkanes and alkenes profile the differences in the range of ions formed across these saturated and unsaturated aliphatic compounds, giving insight into the fate of base oil hydrocarbons in FFO analyses.ConclusionsA rapid method for analysis of FFO compositions has been developed and provides coverage of a range of components of interest. The results indicate that the method presented may be of utility in analysis of other FFOs or similarly challenging complex mixtures.

Effects of chlorine dose on the composition and characteristics of chlorinated disinfection byproducts in reclaimed water

During chlorination of reclaimed water, the dose of chlorine used can influence the formation of chlorinated disinfection by-products (Cl-DBPs). We used non-targeted screening by Orbitrap mass spectrometry to identify Cl-DBPs in samples of chlorinated reclaimed water, and found that chlorination was likely to form slightly oxidized unsaturated aliphatic compounds and polycyclic aromatic compounds. Increasing the chlorine dose increased the proportion of polycyclic aromatic Cl-DBPs containing one chlorine atom (Cl1-DBPs) and highly oxidized unsaturated aliphatic Cl-DBPs containing two chlorine atoms (Cl2-DBPs). In addition, increasing the chlorine dose first decreased and then increased the proportion of Cl1-DBPs with aromatic index values >0.5 and increased the proportion of Cl2-DBPs with aromatic index values <0.5. Increasing the chlorine dose increased double bond equivalent minus oxygen values of Cl1-DBPs and decreased the double bond equivalent minus oxygen values of Cl2-DBPs, while the nominal oxidant state of carbon decreased for Cl1-DBPs and increased for Cl2-DBPs. In considering the possible precursors of Cl-DBPs and their reaction pathways, substitution reactions occurred more readily with aliphatic compounds and addition reactions occurred more readily with aromatic precursors. When the chlorine dose is increased, more Cl2-DBPs may be formed by substitution. Overall, the chlorine dose influences Cl-DBP formation and composition and should be taken into account during water treatment.