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111.
112.
自从ICI低压、低温甲醇合成过程取代高压过程以来,人们对该过程所使用的Cu/ZnO/Al_2O_3或Cu/ZnO/Cr_2O_3催化剂有极大的兴趣。Herman、Klier等人已证明这种低压、低温下的活性应归属于Cu-ZnO间的相互作用,在相同的条件下,单纯的铜或氧化锌的活性几乎可以忽略不计,而氧化铝或氧化铬主要起结构助剂的作用。由此可见,控制适宜的Cu-ZnO间的相互作用是提高甲醇合成活性的关键,因此,如何才能产生这种适宜的相互作用就成了人们极为重视的研究课题。到目前为止,人们普遍采用沉淀法制备铜基甲醇合成催化剂,试图通过改变各种制备条件来开发更好的 相似文献
113.
《中国化学会会志》2018,65(5):578-590
A laboratory study was carried out to investigate the chemical composition of aged aromatic secondary organic aerosol (SOA) formed from the photoxidation of p‐xylene in the presence of ammonia (NH3). The experiments were conducted by irradiating p‐xylene/CH3ONO/NH3 air mixtures without and with NO in a home‐made smog chamber. The particulate products of aged p‐ xylene SOA in the presence of NH3 were measured by UV–vis spectrophotometry, attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, and aerosol laser time‐of‐flight mass spectrometry (ALTOFMS) coupled with the fuzzy C‐means (FCM) clustering algorithm. The experimental results show that NH3 does not alter the gas–particle partitioning in the photoxidation of p‐xylene without NO and that 2,5‐dimethylphenol is the predominant NH3‐aged p‐xylene SOA without NO. However, NH3 has a significant promotional effect on the formation of organonitrogen compounds in the OH‐initiated oxidation of p‐xylene with NO. Organic ammonium salts such as ammonium glyoxylate and p‐methyl ammonium benzoate, which are formed from NH3 reactions with gaseous organic acids, were detected as the major particulate organonitrogen products of NH3‐aged p‐xylene SOA with NO. 1H‐Imidazole, 4‐methyl‐1H‐imidazole, and other imidazole products of the heterogeneous reactions between NH3 and dialdehydes of p‐xylene SOA were newly measured. The possible reaction mechanisms leading to these organonitrogen products are also discussed and proposed. The formation of imidazole products suggests that some ambient particles containing organonitrogen compounds may be the result of this mechanism. The results of this study may provide valuable information for discussing anthropogenic SOA aging mechanisms. 相似文献
114.
The aerosol-gel process is a thin film deposition process based on the sol-gel polymerisation of a liquid film deposited from
an ultrasonically sprayed aerosol. This process offers an attractive alternative for the deposition of sol-gel thin films.
The effects of the aerosol deposition route on the film characteristics have been investigated with regard to sol-gel chemistry.
TEOS solutions have been studied by viscosimetry and FTIR spectroscopy using an ATR device. Silica xerogel coatings have been
studied by transmission FTIR and optical microscopy. Film morphology and uniformity depend closely on the aerosol deposition
conditions. The film growth is controlled by a droplet coalescence surface phenomenon. 相似文献
115.
Giacomo Lorenzini 《Applied biochemistry and biotechnology》1994,48(1):1-4
A new miniaturized kit based on very young supersensitive tobacco Bel-W3 plantlets, which can be easily used to detect phytotoxic
levels of ozone in ambient air in large scale surveys, is described. It has been developed in laboratory as well as field
studies. The optimal sampling time is 5–7 d. The advantages of the kit are its user-friendliness, low cost, and reliability.
The kit may be integrated by a passive sampling tube set and may be also proposed for educational programs. 相似文献
116.
It is found that many kinds of organic gases, which belong to aromatics, terpenes, and cycloalkanes, produce aerosols when irradiated by a deuterium lamp with spectrum ranging from 180 to 400 nm in wavelength, and by a krypton-fluoride excimer laser operated at 249 nm. Two initial processes are important, direct excitation of organic molecule by the ultraviolet light, and reaction of organic molecule with ozone produced photochemically by the ultraviolet light. It depends on compounds which process is dominant. For some compounds, both are possible. 相似文献
117.
气溶胶作为大气颗粒物的重要成分对大气环境以及人体健康均有重要影响.其中气溶胶的吸湿性作为影响其在大气中存活时间以及物理化学性质的重要因素受到广泛关注.目前对于气溶胶颗粒的吸湿性研究较为简单,对于气溶胶颗粒物微观结构对吸湿性的影响较少.本文根据Langmuir吸附模型、Fick扩散定律建立了单颗粒的气-粒作用模型,分析了气溶胶颗粒物的均匀分布结构(H2O/C2H2O4)以及非均匀分布结构(H2O/C2H2O4/H2SO4)对其吸湿性的不同影响。研究结果发现,气溶胶颗粒物的非均匀分布结构会影响其吸湿过程的快慢;对于理想流体构成的气溶胶分子,由于分子之间不存在分子间相互作用,因此气-粒间的水分子交换更快,颗粒物外侧浓度首先升高,接着在浓度差的作用下,内侧颗粒逐渐向外扩散,直至达到平衡;相较与大尺寸的颗粒,在相同体积比的条件下,小颗粒由于气溶胶颗粒物的接触角大,因此表面张力大,水分更难流失;此外,由于大尺寸的气溶胶颗粒物表面积体积比较小,因此颗粒失水速度低,需要更多的时间达到相平衡。 相似文献
118.
A method was developed for the determination of As, Cd, Pb and Tl by electrothermal vaporization inductively coupled plasma
mass spectrometry (ETV-ICP-MS) with slurry sample introduction using certified reference coal samples. The 75As, 111Cd, 208Pb and 205Tl isotopes were monitored, considering the lower probabilities of these isotopes in suffering interferences. The carrier
and modifier effect of Ru added in solution was evaluated, demonstrating that sensitivity for all elements is considerably
improved by the addition of 15 μg of Ru to each individual measurement. This confirms its ability to act as a physical carrier
particularly for the analytes in aqueous solution. Pyrolysis and vaporization temperatures of 500 and 2500 °C, respectively,
were selected after optimization for aqueous solutions and for coal slurries. Similarly, the carrier gas flow rate was optimized
as 1.1 L min−1. After optimization of the operational parameters, the determination of the four elements in six certified reference coal
samples was carried out by external calibration against aqueous standards in 5% v/v HNO3, resulting in good agreement between the certified or given values and the determined ones. For Tl, due to the absence of
certified values, a comparison was established considering previously published data using solid sampling high-resolution
continuum source graphite furnace atomic absorption spectrometry. Detection limits (μg g−1) of 0.1, 0.004, 0.045 and 0.001 were achieved for As, Cd, Pb and Tl, respectively, and the precision was typically better
than 10%. 相似文献
119.
Airborne metallic particulates from industry and urban sources are highly conducting aerosols. The characterization of these pollutant particles is important for environment monitoring and protection. Because these metallic particulates are highly reflective, their effect on local weather or regional radiation budget may also need to be studied. In this work, light scattering characteristics of these metallic aerosols are studied using exact solutions on perfectly conducting spherical and cylindrical particles. It is found that for perfectly conducting spheres and cylinders, when scattering angle is larger than 90° the linear polarization degree of the scattered light is very close to zero. This light scattering characteristics of perfectly conducting particles is significantly different from that of other aerosols. When these perfectly conducting particles are immersed in an absorbing medium, this light scattering characteristics does not show significant change. Therefore, measuring the linear polarization of scattered lights at backward scattering angles can detect and distinguish metallic particulates from other aerosols. This result provides a great potential of metallic aerosol detection and monitoring for environmental protection. 相似文献
120.