In Situ Construction of Manganese Oxide Photothermocatalysts for the Deep Removal of Toluene by Highly Utilizing Sunlight Energy.

The alternative use of electric energy by renewable energy to supply power for catalytic oxidation of pollutants is a sustainable technology, requiring a competent catalyst to realize efficient utilization of light and drive the catalytic reaction. Herein, in situ-synthesized manganese oxide heterostructure composites are developed through solvothermal reduction and subsequent calcination of amorphous manganese oxide (AMO). 95% of toluene conversion and 80% of CO2 mineralization were achieved over amorphous manganese oxide calcined at 250 °C (AMO-250) under light irradiation, and catalyst stability was maintained for at least 40 h. Highly utilization of light energy, uniformly dispersed nanoparticles, large specific surface area, improved metal reducibility, and oxygen desorption and migration ability at low temperature contribute to the good catalytic oxidation activity of AMO-250. Light activated more lattice oxygen to participate in the reaction via the Mars-van Krevelen (MvK) mechanism, and traditional e--h+ photocatalytic behavior exists over the AMO-250 heterostructure composite as an auxiliary degradation path. The reaction pathways of photothermocatalysis and thermocatalysis are close, except for the emergence of different copolymers, where light enhances the deep conversion of intermediates. A proof-of-concept study under natural sunlight has confirmed the feasibility of practical application in the photothermocatalytic degradation of pollutants.

3-Aryl-5-aminobiphenyl Substituted [1,2,4]triazolo[4,3-c]quinazolines: Synthesis and Photophysical Properties.

Amino-[1,1']-biphenyl-containing 3-aryl-[1,2,4]triazolo[4,3-c]quinazoline derivatives with fluorescent properties have been designed and synthesized. The type of annelation of the triazole ring to the pyrimidine one has been unambiguously confirmed by means of an X-ray diffraction (XRD) method; the molecules are non-planar, and the aryl substituents form the pincer-like conformation. The UV/Vis and photoluminescent properties of target compounds were investigated in two solvents of different polarities and in a solid state. The samples emit a broad range of wavelengths and display fluorescent quantum yields of up to 94% in toluene solutions. 5-(4'-Diphenylamino-[1,1']-biphenyl-4-yl)-3-(4-(trifluoromethyl)phenyl)-[1,2,4]triazolo[4,3-c]quinazoline exhibits the strongest emission in toluene and a solid state. Additionally, the solvatochromic properties were studied for the substituted [1,2,4]triazolo[4,3-c]quinazolines. Moreover, the changes in absorption and emission spectra have been demonstrated upon the addition of water to MeCN solutions, which confirms aggregate formation, and some samples were found to exhibit aggregation-induced emission enhancement. Further, the ability of triazoloquinazolines to detect trifluoroacetic acid has been analyzed; the presence of TFA induces changes in both absorption and emission spectra, and acidochromic behavvior was observed for some triazoloquinazoline compounds. Finally, electronic-structure calculations with the use of quantum-chemistry methods were performed for synthesized compounds.

Ginkgo, fennel, and flaxseed can affect hormone release by porcine ovarian cells and modulate the effect of toluene.

Experimental studies have documented the toxic effects of toluene on the mammalian female reproductive processes. The aim of this in vitro study was to examine the potential of functional food plant extracts, namely, of ginkgo, fennel, and flaxseed, in modifying the toluene-induced effects on ovarian hormone release. Porcine granulosa cells were incubated with ginkgo, fennel, or flaxseed extracts (0, 1, 10, or 100 µg/mL) and/or toluene (10 µg/mL). Enzyme immunoassays were used in order to measure the release of progesterone (P), oxytocin (OT), and prostaglandin F (PGF) in the culture media. Toluene suppressed the release of P and enhanced the release of OT and PGF. All tested plant extracts reduced P and increased OT release, while the PGF output was found inhibited by ginkgo and stimulated by fennel and flaxseed. When the cells were incubated with toluene and each one of the plant extracts, toluene was able to prevent their action on P release, as well as those of fennel and flaxseed on OT and PGF release. Moreover, ginkgo enhanced but fennel or flaxseed prevented the toluene-induced effects on OT and PGF release. These observations (i) document novel aspects of the toluene-induced toxicity; (ii) demonstrate the direct influence of ginkgo, fennel, and flaxseed extracts on the ovarian secretory activity; (iii) inform our understanding of the interrelationship between toluene and the tested plant extracts with regard to their effects on ovarian hormone release; (iiii) demonstrate the ability of fennel and flaxseed to prevent adverse effect of toluene on ovarian hormones.

Solvent-dependent formation kinetics of L,L-diphenylalanine micro/nanotubes.

Investigating the molecular mechanism underlying the aggregation process of amyloid fibers is of great importance both for its implications in several degenerative diseases and for the design of new materials based on self-assembly. In particular, micro/nanotubes of L,L-diphenylalanine have been investigated as a model of amyloid plaques in Alzheimer's disease and also for their broad range of physical properties, e.g., good thermo- and mechanical stability, semiconductivity, piezoelectricity and optical properties. It has been reported that the assembly/disassembly dynamics of L,L-diphenylalanine crystals is influenced by the solvent composition being triggered by evaporation of solvents. In fact the solvatomorphism of this peptide-based nanomaterial is complex and rich attracting great attention. Here we investigated the growing kinetics of the micro/nanotubes of L,L-diphenylalanine in samples prepared with toluene, ethanol, and acetic acid solvents by time-resolved Raman spectroscopy. Our results indicated that the self-assembly in this case competes with the water evaporation process contrary to what is reported by samples prepared with widely used solvent 1,1,1,3,3,3-hexafluoro-2-propanol. We note that exclusively tubular structures (being hollow for the toluene solvent case) were observed. Interestingly our results support the fact that for acetic acid, ethanol, and toluene the micro/nanotube formation process is autocatalytic instead of being nucleation-dominating as reported for samples prepared using solvent 1,1,1,3,3,3-hexafluoro-2-propanol.

Pentafluoropropionic Anhydride Derivatization and GC-MS Analysis of Histamine, Agmatine, Putrescine, and Spermidine: Effects of Solvents and Starting Column Temperature.

Gas chromatography-mass spectrometry (GC-MS) is useful for the quantitative determination of the polyamines spermidine (SPD) and putrescine (PUT) and of the biogenic amine agmatine (AGM) in biological samples after derivatization. This GC-MS method involves a two-step extraction with n-butanol and hydrochloric acid, derivatization with pentafluoropropionic anhydride (PFPA) in ethyl acetate, and extraction of the pentafluoropropionic (PFP) derivatives by toluene of SPD, PUT, and AGM. We wanted to extend this GC-MS method for the biogenic amine histamine (HA), but we faced serious problems that did not allow reliable quantitative analysis of HA. In the present work, we addressed this issue and investigated the derivatization of HA and the effects of toluene and ethyl acetate, two commonly used water-insoluble organic solvents in GC-MS, and oven temperature program. Derivatization of unlabelled HA (d0-HA) and deuterium-labelled HA (d4-HA) with PFPA in ethyl acetate (PFPA-EA, 1:4, v/v; 30 min, 65 °C) resulted in the formation of d0-HA-(PFP)2 and d4-HA-(PFP)2 derivatives. d4-HA and 13C4-SPD were used as internal standards for the amines after standardization. Considerable quantitative effects of toluene and ethyl acetate were observed. The starting GC column temperature was also found to influence considerably the GC-MS analysis of HA. Our study shows the simultaneous quantitative analysis of HA as HA-(PFP)2, AGM as AGM-(PFP)3, PUT as PUT-(PFP)2, and SPD as SPD-(PFP)3 derivatives requires the use of ethyl acetate for their extraction and injection into the GC-MS apparatus and a starting GC column temperature of 40 °C instead of 70 °C. The PFP derivatives of HA, AGM, PUT, and SPD were found to be stable in ethyl acetate for several hours at room temperature. Analytically satisfactory linearity, precision, and accuracy were observed for HA, AGM, PUT, and SPD in biologically relevant ranges (0 to 700 pmol). The limits of detection of AGM, PUT, and SPD were about two times lower in ethyl acetate compared to toluene (range, 1-22 fmol). The limits of detection were 1670 fmol for d0-HA and 557 fmol for d4-HA. Despite the improvements achieved in the study for HA, its analysis by GC-MS as a PFP derivative is challenging and less efficient than that of PUT, AGM, and SPD.

Integrated Sustainable Management of Petrochemical Industrial Air Pollution.

The emission inventory, emission factor, and spatial concentration distribution of volatile organic compounds (VOCs) from a petrochemical industry (aromatics plant) were intensively evaluated in this study to elucidate the potential sources of BTX emission and their contribution to ambient concentrations. Five emission groups were quantified through direct measurement and emission models. These data were then used as input for the AERMOD dispersion model for the source apportionment analysis. The source to ambient contribution analysis revealed that a wastewater treatment facility and organic liquid storage tank were major contributors accounting for about 20.6-88.4% and 10.3-75.4% to BTX environmental concentrations, respectively. The highest annual ambient concentrations of benzene (B), toluene (T), and xylenes (X) were predicted as 9.0, 2.8, and 57.9 µg/m3 at the fence line of the plant boundary, respectively. These findings assist policymakers in prioritizing the appropriate control measures to the right source by considering not just the amount released but also their contribution to ambient concentrations. This study suggested that the wastewater treatment unit should be changed to the closed system which will benefit reduction in its emission (45.05%) as well as effectively minimizing ambient VOC concentration by 49.96% compared to its normal operation.

Ionization and lipophilicity in nonpolar media mimicking the cell membrane interior.

Ionization and lipophilicity may vary with the environment. Therefore, in this study we provide some insight in the performances of different experimental techniques (potentiometry, UV-vis, shake-flask and chromatography) to determine ionization and lipophilicity in more nonpolar systems than those commonly used in drug discovery. To this purpose a pool of 11 compounds of pharmaceutical interest was firstly submitted to a few experimental techniques to measure pKa in water, water/acetonitrile mixtures and pure acetonitrile. Then we measured logP/logD with shake-flask and potentiometry in octanol/water and toluene/water and also determined a chromatographic lipophilicity index (log k'80 PLRP-S) in a nonpolar system. Results show that ionization decreases for both acids and bases in a coherent, significant but not dramatical extent when water is present in the system, but the picture is completely different in pure acetonitrile. Lipophilicity may vary or not with the environment according to the chemical structure of the investigated compounds as also revealed by electrostatic potential maps. Since the internal core of cell membranes is largely nonpolar, our results support the need of extending the pool of physicochemical descriptors to be determined in the various stages of drug discovery programs and indicate some experimental strategies for their determination.

Evaluation of Bacillus subtilis as a Tool for Biodegrading Diesel Oil and Gasoline in Experimentally Contaminated Water and Soil.

Benzene, toluene, ethylbenzene and xylene (BTEX) are toxic petroleum hydrocarbons pollutants that can affect the central nervous system and even cause cancer. For that reason, studies regarding BTEX degradation are extremely important. Our study aimed evaluate the microorganism Bacillus subtilis as a tool for degrading petroleum hydrocarbons pollutants. Assays were run utilizing water or soil distinctly contaminated with gasoline and diesel oil, with and without B. subtilis. The ability of B. subtilis to degrade hydrophobic compounds was analyzed by Fourier-Transform Infrared Spectroscopy (FTIR) and gas chromatography. The FTIR results indicated, for water assays, that B. subtilis utilized the gasoline and diesel oil to produce the biosurfactant, and, as a consequence, performed a biodegradation process. In the same way, for soil assay, B. subtilis biodegraded the diesel oil. The gas chromatography results indicated, for gasoline in soil assay, the B. subtilis removed BTEX. So, B. subtilis was capable of degrading BTEX, producing biosurfactant and it can also be used for other industrial applications. Bioremediation can be an efficient, economical, and versatile alternative for BTEX contamination.

Engineering the Substrate Specificity of Toluene Degrading Enzyme XylM Using Biosensor XylS and Machine Learning.

Enzyme engineering using machine learning has been developed in recent years. However, to obtain a large amount of data on enzyme activities for training data, it is necessary to develop a high-throughput and accurate method for evaluating enzyme activities. Here, we examined whether a biosensor-based enzyme engineering method can be applied to machine learning. As a model experiment, we aimed to modify the substrate specificity of XylM, a rate-determining enzyme in a multistep oxidation reaction catalyzed by XylMABC in Pseudomonas putida. XylMABC naturally converts toluene and xylene to benzoic acid and toluic acid, respectively. We aimed to engineer XylM to improve its conversion efficiency to a non-native substrate, 2,6-xylenol. Wild-type XylMABC slightly converted 2,6-xylenol to 3-methylsalicylic acid, which is the ligand of the transcriptional regulator XylS in P. putida. By locating a fluorescent protein gene under the control of the Pm promoter to which XylS binds, a XylS-producing Escherichia coli strain showed higher fluorescence intensity in a 3-methylsalicylic acid concentration-dependent manner. We evaluated the 3-methylsalicylic acid productivity of XylM variants using the fluorescence intensity of the sensor strain as an indicator. The obtained data provided the training data for machine learning for the directed evolution of XylM. Two cycles of machine learning-assisted directed evolution resulted in the acquisition of XylM-D140E-V144K-F243L-N244S with 15 times higher productivity than wild-type XylM. These results demonstrate that an indirect enzyme activity evaluation method using biosensors is sufficiently quantitative and high-throughput to be used as training data for machine learning. The findings expand the versatility of machine learning in enzyme engineering.

Effective Toluene Ozonation over δ-MnO2: Oxygen Vacancy-Induced Reactive Oxygen Species.

To improve the reactivity and lifetime of catalysts in the catalytic ozonation of toluene, a simple strategy was provided to regulate the morphology and microstructure of δ-MnO2 via the hydrothermal reaction temperature. The effects of the reaction temperature and the ozone to toluene concentration ratio on the catalyst performance were investigated. The optimized MnO2-260 catalyst prepared at the limiting hydrothermal temperature (260 °C) showed high catalytic activity (XTol = 95%) and excellent stability (1200 min) at the approximately ambient temperature of 40 °C, which was superior to the results in previous studies. The structure and morphology of δ-MnO2 were characterized by extended X-ray absorption fine structure, X-ray diffraction, scanning electron microscopy, positron annihilation lifetime spectroscopy, electron spin resonance, and other techniques. Experimental results and density functional theory calculations were in agreement that surface oxygen vacancy clusters, especially surface oxygen dimer vacancies, are critical in ozone activation. Oxygen vacancies can facilitate the adsorption and activation of O3 to generate reactive oxygen species (ROS, including 1O2, O2-, and •OH), leading to superior ozonation activity to degrade toluene and intermediates. Meanwhile, free radical detection and scavenger tests indicated that •OH is the primary ROS during toluene ozonation rather than 1O2 or O2-.

An immobilization of aminopropyl trimethoxysilane-phenanthrene carbaldehyde on graphene oxide for toluene extraction and separation in water samples.

A new functionalized Nano graphene with aminopropyl trimethoxysilane-phenanthrene-4-carbaldehyde (NGO@APTMS-PNTCA) as a novel adsorbent was used to extract toluene from water samples by the ultrasound-assisted dispersive solid-phase microextraction procedure (USA-D-SPME). So, 50 mg of NGO@APTMS-PNTCA adsorbent was added to water samples and sonicated for 20 min. After toluene extraction, the NGO@APTMS-PNTCA adsorbent separated from the liquid phase with a Whatman membrane filter (200 nm). Then, the toluene was back-extracted from the adsorbent by 2.0 mL of the acetone/ethanol (1:1, eluent) at 25 °C. Due to the physical properties and structure of toluene, fluorobenzene was used as an internal standard. Finally, the toluene values were measured by a gas chromatography-flame ionization detector (GC-FID). In optimized conditions, the limit of detection (LOD), the working range (WR), and the enrichment factor (EF) were obtained at 2.5 µg L-1, 0.01-1.2 mg L-1, and 9.63, respectively (MRSD% = 3.38). Also, the limit of quantification (LOQ) 10 µg L-1 and extraction recovery of more than 95% was efficiently achieved for toluene. Standard additions of toluene to blank solutions had high recoveries between 95.2% and 104.5% with a relative standard deviation (RSD%) of 0.27-5.2. The absorption capacities of NGO and NGO@APTMS-PNTCA adsorbents for toluene extraction were obtained at 32.8 mg g-1 and 154.9 mg g-1, respectively. The USA-D-SPME method was validated by spiking the standard concentrations of toluene. The proposed method demonstrated relevant and suitable statistical results with high accuracy and precision for toluene extraction by a novel adsorbent synthesis.

Structure-property-performance relationship of transition metal doped WO3 mixed oxides for catalytic degradation of organic pollutants.

Transition metal doped WO3 mixed oxides (named as W-M-O, M = Nb, Fe, Cr, Cu, Ti or Sn, respectively) with high structure stability were synthesized by modified sol-gel method using citric acid as organic crosslinking agent, and were evaluated for catalytic elimination of low-concentration toluene, monochlorobenzene and 1,2-dichloroethance with high toxicity and relatively stable molecule structure, as the typical examples for the pollutants of various volatile organic compounds (VOCs). Results of the structure-property-performance relationship research showed that mesoporous structure and nanocrystalline/amorphous state were formed, and binary metal components were dispersed into each other, which contributed to promoting the metal/metal electron interaction and adjusting the physicochemical properties of mixed metal oxides. The sequence of apparent catalytic activity for toluene degradation was: W-Nb-O＞W-Fe-O＞W-Cr-O, W-Cu-O＞W-Ti-O＞W-Sn-O＞WO3, and the sequence for monochlorobenzene degradation was: W-Nb-O＞W-Fe-O＞W-Cr-O, W-Ti-O＞W-Cu-O＞W-Sn-O＞WO3. There existed cooperative catalytic effect: mesopore and surface acid sites of catalysts facilitated adsorption, activation and breakage of the C-X bond, and then redox sites of catalysts promoted deep oxidation of a series of reaction intermediates to transform into CO2 and H2O. Especially, the optimized W-Nb-O catalyst deserved more attention, since it represented remarkable catalytic activity, selectivity and durability for three typical VOCs degradation along with good resistance to water vapor and corrosion of HCl.

Preparation of environment-friendly SiO2 aerogel based on waste boron mud and its adsorption behavior for toluene.

To mitigate the environmental hazards of boron mud waste accumulation, we prepared environmental-friendly SiO2 aerogels by extracting them through alkaline leaching treatment and optimized the experimental conditions. The optimum process parameters for alkaline leaching solution NaOH concentration, leaching temperature, solid-to-liquid ratio, and leaching time were 2 mol/L, 95 °C, 1:4, and 3 h, respectively. In this work, cheap and non-toxic hydroxy silicone oil (PDMS-OH) and hydrogen-containing silicone oil (PMHS) were used as surface modifiers instead of toxic and expensive trimethylchlorosilane (TMCS) in the SiO2 aerogel modification process. The best performance under the optimum conditions was achieved with 60% PDMS-OH-modified SiO2 aerogel. Organic liquid spills, represented by toluene, pose a great danger to the environment and water bodies. We treated free toluene on the water surface with the aerogel mentioned above and its adsorption capacity was up to 2,655 mg/g. After the adsorption of toluene, the aerogels coalesced into agglomerates for subsequent collection and handling. Furthermore, after five repeated applications, the adsorption capacity remained at 91.43% of the initial application. Overall, this research provided an inexpensive and simple solution for the treatment of organic liquids in wastewater.

Volatile organic compounds at a roadside site in Hong Kong: Characteristics, chemical reactivity, and health risk assessment.

Volatile organic compounds (VOCs) and oxygenated VOCs (OVOCs) play important roles in atmospheric chemistry and are recognized as the major pollutants in roadside microenvironments of metropolitan Hong Kong, China. In this study, the ambient VOCs and OVOCs were intensively monitored at a roadside site in Hong Kong for one month during morning and evening rush hours. The emission characterizations, as well as ozone formation potentials (OFP) and hydroxyl radical (OH) loss rates (LOH) were determined. Results from the campaign showed that the average concentrations of detected VOCs/OVOCs ranged from 0.21 to 9.67 ppb, and higher toluene to benzene (T/B) ratio was observed during evening sections due to the variation of fuel types in vehicle fleets and mix of additional emission sources in this site. On average, OVOCs had much higher concentrations than the targeted VOC species. Acetone, formaldehyde, and acetaldehyde were the three most abundant species, while formaldehyde showed the highest contributions to both OFP (32.20 %) and LOH (16.80 %). Furthermore, potential health hazards with inhalation exposure to formaldehyde, acetaldehyde, propionaldehyde, methyl ethyl ketone (MEK), 1,3-butadiene, toluene, benzene, and acrylonitrile were found. These results reveal that it is imperative to implement efficient control measures to reduce vehicle emissions for both primary and secondary pollutants and to protect both roadside workers and pedestrians.

Synergistic Catalytic Oxidation of Typical Volatile Organic Compound Mixtures on Mn-Based Catalysts: Significant Promotion Effect and Reaction Mechanism.

The miscellaneous volatile organic compounds (VOCs) in industrial flue gas streams usually demonstrate significant mutual inhibition effects, and the behavior of a particular VOC in mixtures is not clear, which hinders the application of catalytic technology. This study examines the catalytic oxidation and mixing effects of representative VOCs in industrial exhausts, consisting of acetone (AC), ethyl acetate (EA), and toluene (Tol), on common Mn-based catalysts (e.g., MnO2, Mn2O3, LaMnO3, and Mn3O4) by means of intrinsic activity evaluation, coadsorption, VOC temperature-programmed oxidation, in situ diffuse reflectance infrared Fourier transform spectroscopy, and gas chromatography-mass spectrometry. The results showed no inhibiting effect on the conversion of these VOCs when combusted together; instead, a significant mutual promotion effect was found, especially on Tol destruction, with a sharp decrease in the Tol T50 from 214 to 158 °C on MnO2. It is proposed for the first time that the addition of AC/EA in Tol combustion leads to the generation of o/m-methyl phenol, which changes the rate-determining step of the ring-opening process, thus elevating the conversion of Tol together with AC and EA in the mixture at low temperatures.

Catalytic removal of toluene using MnO2-based catalysts: A review.

Volatile organic compounds (VOCs) have serious hazard to human health and ecological environment. Due to its low cost and high activity, the catalytic oxidation technology considered to be the most effective method to remove VOCs. Toluene is one of the typical VOCs, hence its catalytic elimination is crucial for the regulation of VOCs. Manganese dioxide (MnO2) has been extensively studied for its excellent redox performance and low-temperature operation conditions. In this review, we summarize the research progresses in the toluene catalytic oxidation of MnO2-based catalysts, which contain single MnO2, metal-doped MnO2 and supported MnO2 catalyst. In particular, we pay much attention on the relationship between the chemical properties and toluene oxidation performance over MnO2 catalyst, as well as the catalytic reaction mechanisms. Moreover, the effects of different crystal forms and morphologies on the catalytic toluene reaction were discussed. And the perspective on MnO2 catalysts for the catalytic oxidation of toluene has been proposed. We expect that the summary of these important findings can serve as an important reference for the catalytic treatment of VOCs.

Precise preparation of biomass-based porous carbon with pore structure-dependent VOCs adsorption/desorption performance by bacterial pretreatment and its forming process.

Pore distribution characteristic is one of the most crucial factors for porous adsorption materials, and the variety of volatile organic compounds (VOCs) approaches about how to simply and accurately tailor practical porous carbons for VOCs adsorption has gradually attracted attention. Here, precursors with different lignocellulose mass ratios have been used to produce porous carbon for model experiments to investigate the influence of the precursor lignocellulose contents on the pore structure and distribution characteristics of porous carbon, and the applicability of these mechanisms to real biomass materials has been further verified through bacteria-targeted bagasse decomposition: the microvolumes of ultra-micropores have decreased with decrease in cellulose contents, while mesopores have followed the reverse trend. The dynamic toluene adsorption/desorption performances of the obtained samples have been tested. The BACs-36 exhibits high toluene adsorption performance in low concentration with 635 mg/g while the BACs-48 shows excellent reusability in 10 times cycles. Based on this the balance between the adsorptive and regenerative capacities has been observed which indicates that carbon materials with abundant micropores and narrow mesopores have much better adsorption performance than porous carbon with a hierarchical pore structure, while the latter show better regeneration abilities than the former, which resulting in less desorption as a counter-acting force at the pore wall. Furthermore, the porous carbon has been shaped by one-step co-pyrolysis method using phenolic resin, which can not only maintain the hardness but also can avoid pore plugging phenomenon.

Expediting Toluene Combustion by Harmonizing the Ce-O Strength over Co-Doped CeZr Oxide Catalysts.

Low-temperature catalytic degradation of volatile organic compounds (VOCs) by enhancing the activity of non-precious metal catalysts has always been the focus of attention. The mineralization of aromatic VOCs requires the participation of a large number of oxygen atoms, so the activation of oxygen species is crucial in the degradation reaction. Herein, we originally adjust the Ce-O bond strength in CeZr oxide catalysts by cobalt doping to promote the activation of oxygen species, thus improving the toluene degradation performance while maintaining high stability. Subsequent characterizations and theoretical calculations demonstrate that the weakening of the Ce-O bond strength increases the oxygen vacancy content, promotes the activation of oxygen species, and enhances the redox ability of the catalysts. This strategy also promotes the activation of toluene and accelerates the depletion of intermediate species. This study will contribute a strategy to enhance the activation ability of oxygen species in non-noble metal oxide catalysts, thereby enhancing the degradation performance of VOCs.

Chain Walking in the AlCl3 Catalyzed Cationic Polymerization of α-Olefins.

Continuing efforts aimed at performing the 1-decene polymerization to low viscosity polyalphaolefins (PAO)s using a less hazardous AlCl3 catalyst than boron-based analogs, the basic mechanisms of this system were revealed in this research. In this aspect, neat AlCl3 and AlCl3 /toluene were carried out to perform 1-decene polymerizations. Microstructure analyses of the as-synthesized oils revealed low molecular weight (708 vs. 1529 g/mol), kinematic viscosity (KV100 =6.4 vs. 22.2 cSt), and long chain branching (82.1 vs. 84.7) of PAO from the system containing toluene solvent. Furthermore, NMR analysis confirmed various types of short chain branch (SCB) with the inclusion of toluene ring in the structure of final PAO chains. Then, to shed light on the basic mechanisms of cationic polymerization of 1-decene including: i) chain initiation, ii) chain transfer to the monomer, iii) isomerization of the carbocation via a chain walking mechanism (causes different SCB length), and iv) binding of toluene ring to the propagating PAO chain (to yield aromatic containing oligomers), molecular modeling at the DFT level was employed. The energies obtained confirmed the ease of carbocation isomerization and chain transfer mechanisms in toluene medium, which well confirms the highly branched structure experimentally obtained for related PAO.

Explication on distribution patterns of volatile organic compounds in petro-chemistry and oil refineries of China using a species-transport model and health risk assessment.

Volatile organic compounds (VOCs) from industrial emissions have attracted great attention due to their negative effects on human, but there is lack of deterministic air quality model for VOC emissions. In this study, airborne VOCs from a typical petrochemical and oil refinery region, Lanzhou, Gansu province of China, were on-site measured. The regional pollution patterns were investigated using a species transport model and the health risks were evaluated. The spatial distribution of VOCs showed that 87.5 % of the airborne VOCs were benzene, toluene, ethylbenzene, and xylene having higher concentration (146 µg/m3) in the north direction oil refinery industrial areas. The concentrations of toluene and benzene were as high as 41.5 and 33.3 µg/m3 in the 4 km2 area away from the petrochemical emission source, respectively, and the concentration of o-/m + p-xylene was up to 79.7 µg/m3. Based on the measured concentration data, the numerical results showed that the accumulation of high concentration of VOC species by mass transfer in the region is related to the atmospheric diffusion driven by downward-moving air over the valley areas. Non-carcinogenic risk assessments showed that airborne benzene exposure had acceptable hazard quotient of 0.185 for adults, which was 1.8 times of children's (0.102), whereas it was found that a high carcinogenic risk (>10-4) from benzene in several sampling sites and diffuse distance become significant for carcinogenic risk. This study verified the effectiveness of VOC atmospheric diffusion model through a large number of on-site monitoring data, providing data support for model-based risk assessment.