Peng Ping-an

Synthesis, characterization and photocatalytic property of nano-sized Zn2SnO4

Nano-sized Zn2SnO4 materials have been synthesized using the coprecipitation method. The synthetic conditions and the calcination behaviors of nano-sized Zn2SnO4 materials have been studied. The nano-sized Zn2SnO4 materials have been characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry and differential thermal analysis (TG-DTA) and specific surface area. As a result, the kinetic grain growth equation for nano-sized Zn2SnO4 can be expressed as D4.78 = 9.12 × 1023t exp(−40.6 × 103/T), with an activation energy for grain growth of Q = 337.9 KJ/mol. The nano-sized Zn2SnO4 materials have been used as photocatalysts to decompose benzene in water solution. The results show that Zn2SnO4 can photocatalytically decompose benzene, and the photocatalytic capacity for Zn2SnO4 relates to the grain size, which is discussed in terms of the surface effect and the quantum size effect.

Characterization of organic matter in total suspended particles by thermodesorption and pyrolysis-gas chromatography-mass spectrometry

The organic matter in tropospheric aerosol plays an important role in atmospheric physical and chemical processes. The bulk of organic matter, representing a significant proportion of the total suspended particulate (TSP) mass, is bound to polymeric material whose structure and properties are largely unknown. Here we used thermodesorption gas chromatography/mass spectrometry (Td-GC/MS) to study organic compounds of low molecular mass and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) to characterize the chemical structure of macromolecules in TSP samples collected in different seasons from different sites in Guangzhou. n-Alkanes, fatty acids and nitriles were the predominant compounds in the thermodesorption products, whereas aromatics, fatty acids, nitriles and n-alkanes/alkenes were the major compounds in the pyrolysates. The results indicated that aromatics were main units in macromolecules. The fatty acids and nitriles formed from carboxylic ammonium salts were detected in both thermodesorption products and pyrolysates at a certain concentration, indicating the importance of these compounds in TSP formation. The TSP source mainly determined the occurrence of compounds in samples from urban, suburban and forest sites, whereas the TSP source and formation process maybe controlled the seasonal variation in compounds detected. High levels of nitriles in summer samples from suburban and forest sites coincide with the release of ammonium from the land and of fatty acids from vegetation at these sites.

Establishment and Application of the Co-analysis Method of PBDD/Fs and PCDD/Fs with Isotope Dilution High Resolution Gas Chromatography-High Resolution Mass Spectrometry in Ambient Air Samples

Abstract It has been known that the polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) share similar or even higher toxicity and bio-accumulativity with polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs). In this study, the co-analysis method of PBDD/Fs and PCDD/Fs with isotope dilution HRGC-HRMS was built based on the U.S. EPA Method 1613 and TO-9A. The samples were extracted and cleaned through acid silica gel bed, multi-layer silica gel column, and Florisil column, respectively. Eight 2,3,7,8-PBDD/Fs congeners and 17 congeners of 2,3,7,8-PCDD/Fs were quantified. The HRGC-HRMS conditions for PBDD/Fs were: EI+ and SIM model with resolution ≥ 10000, electron emission energy of 50 eV, and filament current of 0.75 mA; DB-5 MS fused silica capillary column (30 m × 0.25 mm i.d., 0.1 μm) was used and the temperatures for injection, ion source, and transfer line were 250 °C, 250 °C, and 305 °C, respectively. The carrier gas was helium (1.0 ml min−1). The results showed that the relative standard deviations (RSDs) of parallel blank samples were ≤ 10.3% and the recoveries of PBDD/Fs and PCDD/Fs were in the range of 73%–112%. The average quantified values of the standard reference sample were in accordance with the certified values and the RSDs were ≤ 12.0%. The method detection limits were 0.25–1.5 pg μl−1 for PBDD/Fs and 1.5–5 pg μl−1 for PCDD/Fs. The concentrations of PBDD/Fs and PCDD/Fs were 1.01–2.43 pg per m3 and 6.19–10.8 pg per m3 for particulate samples, and 0.036–0.801 pg per m3 and 1.37–12.1 pg per m3 for gaseous samples of certain area, respectively. Compared with other areas in the world, the atmospheric dioxins pollution of the sampling area was at high level.

Molecular characterization of sulfur compounds in some specieal sulfur-rich Chinese crude oils by FT-ICR MS

Routine GC/MS analysis may apply to the volatilized Low-Molecular-Weight compounds in saturate and aromatic hydrocarbon fractions; thus, relative studies using this technique inevitably bring about some limitations on distribution of miscellaneous sulfur atom. In this article, Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) with high resolution is employed to investigate the distribution of organic sulfur compounds (OSCs) in the crude oil typically derived from the Eogene carbonate-evaporite sediments with further chemical compositional characterization in molecular level by miscellaneous atomic type, carbon number, and double bond equivalent (DBE). A variety of miscellaneous atomic types with S1, S2, S3, OS, OS2, O2S, O2S2, NS, and NOS etc. (S1 means those OSCs with one sulfur atom in a molecule) were identified in OSCs in these oil samples. High levels of alkyl thioether series compounds with one ring structure were presented mainly in the crude oil in the Jianghan Basin whereas high amounts of benzothiophene, dibenzothiophene etc. compounds with higher values in DBE and carbon number range occurred in the sulfur-rich heavy oil in the Jinxian Sag. Although carbonate-evaporite sediments deposited in the saline lacustrine facies in the Eogene basin both occurred in the Jinxian Sag and Jianghan Basin, obviously, they possess different chemical diagenetic pathway of sulfur under various microbial reactions, leading to diverse distributional characteristics on biomarkers, OSCs, and even different hydrocarbon generation mechanism of immature crude oil.

Identification and formation of sulfur-containing steroids in sulfur-rich heavy oils in the Jinxian Sag, Bohai Bay Basin, North China

High abundant sulfur-containing steroids were identified and detected in saturate hydrocarbon fractions of heavy oil with a high sulfur content in the Jinxian Sag, Bohai Bay Basin, North China. These sulfur-containing steroids were structurally merged into the D-ring of steroid nucleus with thiophene ring and/or combined into the C-22 in the side-chain. Based on the previous reports of sulfur-containing steroids with methylthio-teroids and intra-molecular form, four formation mechanisms of sulfur-containing steroids and diagenetic pathway of steroids under S-rich conditions were proposed in this paper according to the double bond positions in the sterene compounds. Hydrogenation and sulfurization both occurred in the diagenetic processes of olefinic bond in the side-chain of steroids: abiogenic chemical hydrogenation of H2S and HS− leads to the formation of regular steranes; a successful sulfurization process leads to the formation of the side-chain sulfur-containing steroids whereas unsuccessful cyclization and/or sulfurization result in the generation of short-chain steranes. This kind of mechanism of hydrogenation/sulfurization of side-chain olefinic bond provides a potential genesis clue for the occurrence of high abundance of short-chain steranes (higher than the common regular steroids, phytane and n-alkanes) in S-rich heavy oils and source rocks in the Jinxian Sag, Bohai Bay Basin, North China.

Progress in generation kinetics studies of coal-derived gases

Abstract Hydrocarbon-generation kinetics is of applicable significance in the study of coal-derived gas pool formation. Its research progress in recent years includes: in combination with geothermal history, it is used as a tool to evaluate source rocks dynamically and depict the change of source kitchen with geological time; according to the carbon isotope fractionation kinetics, a more precise model of identifying coal-derived gas is developed, which contains the kinetic relationship among gas compounds; the combination of compositional kinetics and carbon isotopic kinetics leads to the study method of accumulation processes of coal-derived gases, which is constrained precisely by multi kinetic indices; with the reservoir records, generation kinetics is used to study the whole gas life including generation, charge and alteration. The problems that need investigation are generation kinetics of coal-derived gas at low maturity, pressure effects on gas generation, minerals and water influences, and kinetics of residual soluble organic matter at high maturity.

The record of atmospheric CO2 derived from the stable carbon isotopic composition of buried plant in perennial frozen lacustrine sediments

Abstract The δ 13 C values of well-preserved submersed plant tissues of Potamogeton pectinatus in a 200-cm perennial frozen lacustrine sediment of Ngoring Lake, representing the age from 9.17 to 2.17 ka BP, range from −17.67‰ to −11.39‰, and have a decreasing trend from bottom to top with obvious shifts at 6.77 and 4.56 ka BP. According to the model of carbon isotopic fractionation in submersed plant, an approach that can be used to estimate the atmospheric CO 2 change is developed because the δ 13 C of submersed plant is the function of the dissolved CO 2 concentration. The calculated results show that the atmospheric CO 2 concentration had an increasing tendency from 9.16 to 2.17 ka BP, and can be divided into three periods similar to the carbon isotope composition. The obvious shifts of δ 13 C in submersed plant tissues represent twice leaps of atmospheric CO 2 at 6.77 and 4.56 ka BP with average increase of approximately 30 and 45 ppmv in concentration, respectively.