共查询到20条相似文献,搜索用时 31 毫秒
1.
《Journal of aerosol science》1999,30(8):1095-1113
A physical box model simulating the aerosol particle evolution along air mass trajectories is developed to provide a tool for interpreting the local observations of stratospheric aerosols (i.e., polar stratospheric clouds). The model calculates the composition and the size distributions of H2SO4/H2O and HNO3/H2SO4/H2O liquid droplets. The parameterization of the physical processes affecting the dynamics of HNO3 and H2SO4 solid hydrates and ice particle size distributions is also included, but not used. This work is restricted to some speculations about the liquid to solid transition, according to existing theories. The evolution of liquid particles is simulated taking into account nucleation, diffusive condensation/evaporation and coagulation. This paper reports the physical and numerical details of the model, which are discussed within the framework of the current understanding of the stratospheric aerosol physics. Performance and limitations of the model are discussed on the basis of the evolution of particle size, and composition along synthetic air mass thermal histories. Size distributions and size-dependent acid weight fractions of the liquid stratospheric aerosols consisting of HNO3/H2SO4/H2O are calculated in the cases of air mass thermal histories with different cooling rates and with rapid temperature fluctuations. 相似文献
2.
《Fuel》2007,86(7-8):983-992
In this study in which the Taguchi method was used, the optimization of sulphur removal by H2O2/H2SO4 solutions was carried out over lignite with higher content of sulphur from Artvin/Yusufeli, Turkey. In experiments, the ranges of experimental parameters were between 0.25 and 6.0 mol L−1 for H2O2 concentration, 0.25–4 mol L−1 for H2SO4 concentration, 10–60 °C for reaction temperature, 0.01–0.08 g mL−1 for solid-to-liquid ratio, 15–120 min for reaction time, 200–300 rpm for stirring speed and 710–120 μm for particle size. The optimum conditions for these parameters have found to be 60 °C of temperature, 0.06 g mL−1 of solid-to-liquid ratio, 60 min of reaction time, 250 rpm of stirring speed and −250 + 180 μm of particle size.A statistical experimental arrangement, L25(56) was prepared to determine optimum sulphur removal and ash removal ratios. The obtained yields were 97.85% in removal of total sulphur, 56.54% in removal of pyritic sulphur, 21.33% in removal of organic sulphur and 61.52% in removal of ash. According to variance analysis, it was seen that all parameters were effective in removal of pyritic and total sulphur, reaction temperature, solid-to-liquid ratio, reaction time, stirring speed, H2O2 and H2SO4 concentrations in removal of organic sulphur, and other parameters except acid concentration in removal of ash. 相似文献
3.
《Fuel》2005,84(14-15):1968-1974
Removal of Hg0 vapor from the simulated coal combustion flue gases with a commercial activated carbon was investigated using H2S. This method is based on the reaction of H2S and Hg over the adsorbents. The Hg0 removal experiments were carried out in a conventional flow type packed bed reactor system in the temperature range of 80–150 °C using simulated flue gases having the composition of Hg0 (4.9 ppb), H2S (0–20 ppm), SO2 (0–487 ppm), CO2 (10%), H2O (0–15%), O2 (0–5%), N2 (balance gas). The following results were obtained: in the presence of both H2S and SO2, Hg removal was favored at lower temperatures (80–100 °C). At 150 °C, presence of O2 was indispensable for Hg0 removal from H2S–SO2 flue gas system. It is suggested that the partial oxidation of H2S with O2 to elemental sulfur (H2S+1/2O2=Sad+H2O) and the Clause reaction (SO2+2H2S=3Sad+2H2O) may contribute to the Hg0 removal over activated carbon by the following reaction: Sad+Hg=HgS. The formation of elemental sulfur on the activated carbon was confirmed by a visual observation. 相似文献
4.
《Fuel》2006,85(12-13):1803-1810
A non-equilibrium method using fixed bed microreactor was used to measure SO2 adsorption characteristics of chars and activated carbons derived from Saskatchewan lignite. SO2 breakthrough times and profiles were measured using lignite at a variety of temperatures, particle sizes and SO2 concentrations of 75–175 °C; 2–5.6 mm and 1000–5000 ppm, respectively. Adsorption was found to be a strong function of residence time and feed SO2 concentration, a moderate function of particle size and a weak function of temperature. There was a marginal difference in the adsorption capacity between lignite (15 mg SO2/g lignite) and the char obtained from the same starting amount of lignite (26 mg SO2/g char, or 17 mg SO2/g original lignite). Activation of lignite with steam resulted in an activated carbon, which had highest adsorption capacity of 93 mg SO2/g activated carbon. 相似文献
5.
《Journal of aerosol science》1999,30(3):355-367
A sectional model (AEROFOR) for the formation of sulphuric acid–water particles has been developed. The model includes gas-phase chemistry and aerosol dynamics. An increased UV-B irradiation penetrating into the troposphere due to stratospheric ozone depletion causes via the SO2 oxidation route an enhanced nucleation potential for new H2SO4–H2O particles as well as the growth of particles to CCN size. Using AEROFOR we show that after a nucleation event the nucleated particle concentration is linearly dependent on increased UV-B irradiation with a positive slope. On the other hand, due to increased CO2 concentration photosynthetic rates of plants will increase, and it is likely that enhanced photosynthesis in forests will increase emissions of biogenic volatile organic compounds (BVOC) such as isoprene and monoterpenes. We show that the nucleated particle concentration decreases with increasing BVOC emission, but this dependence is not linear. We investigate the strength of these opposite effects and fit a straight line for such UV-B and BVOC conditions which yield a certain particle number density. The coupling between O3, OH and particle concentrations as a function of UV-B and BVOC emission is also demonstrated. 相似文献
6.
Two new tetrazamacrocycle based compounds, namely, [Cu6L3(SO4)2]·SO4·8H2O (1) and [Cu2L(SO4)(H2O)].2H2O (2), have been prepared at different temperatures (H2L = 10,21-dimethyl-3,6,14,17-tetraazatricyclo[17.3.18,12]tetracosa-1(23),8,10,12(24),19,21-hexaene-23,24-diolate). In 1, each SO42 − anion bridges three [Cu2L]2 + cations to yield a hexagonal network, whereas in 2 each SO42 − anion only links one [Cu2L]2 + cation to afford a discrete binuclear structure. Remarkably, the 2D network structure of 1 was transformed into the 0D structure of 2 in a single-crystal to single-crystal (SC–SC) fashion at room temperature. 相似文献
7.
Yunqin Lin Jianjin Liang Shubin Wu Baohan Wang 《Journal of Industrial and Engineering Chemistry》2013,19(1):316-321
The study focused on the mesophilic anaerobic hydrogen production from PPS (pulp and paper sludge) and FW (food waste) pretreated by NaOH or H2SO4, and the subsequent thermophilic anaerobic methane production with the effluent in a two-stage process. The maximum hydrogen yield (78.35 mL g?1 VSfed) which was 50.21% higher than that of CK, was achieved when 10 g NaOH/100 g TSsubstrate was used. However, the maximum methane yield (383.8 mL g?1 VSfed) was obtained in CK as well as 64% SCOD removal efficiency was achieved. In short, NaOH/H2SO4 pretreatment was suitable to enhance the hydrogen production. 相似文献
8.
Yuttapong Tanawannapong Amaraporn Kaewchada Attasak Jaree 《Journal of Industrial and Engineering Chemistry》2013,19(1):37-41
Waste cooking oil (WCO) was used to produce biodiesel in a microtube reactor. First, the acid value of the WCO was reduced from 3.96 mg KOH/g to less than 1 mg KOH/g via acid catalyzed esterification. The effects of the methanol-to-WCO molar ratio (4.5:1–18:1), the H2SO4 concentration (0.5–2 wt.%), reaction temperature (55–70 °C), and reaction time (5–20 s) were studied. The optimal conditions were 9:1 methanol-to-WCO molar ratio, 1 wt.% H2SO4, 65 °C and 5 s of reaction time. Triglycerides in the product from the first step were transesterified with methanol and alkaline catalyst. Methyl ester content of the biodiesel was 91.76%. 相似文献
9.
Li-Cai Zhu Yi Zhao Shu-Juan Yu Mou-Ming Zhao 《Inorganic chemistry communications》2010,13(11):1299-1303
Two transition-lanthanide metal-organic coordination polymers, {[CoLn2(Himdc)2(SO4)2(H2O)4]·H2O}n [Ln = Yb (1), Ho (2)] (H3imdc = imidazole-4, 5-dicarboxylic acid), have been synthesized by the hydrothermal reactions of lanthanide oxides, CoSO4·7H2O, H3imdc and H2O. Single-crystal X-ray diffraction analysis reveals that the isostructural complexes 1 and 2 possess unusual 2D wave-like heterometallic layers with 1D (Ln2O2CoO2)n and [Ln2(SO4)2]n inorganic chains constructed by the assembly of 1D left-/right-handed helical L–Ln2Co–L (L = Himdc) chains and SO42? anions, while a 3D framework is formed via hydrogen-bonding interactions interlayer. 相似文献
10.
Deok Hyun Moon Ju-Ry Lee Mahmoud Wazne Jeong-Hun Park 《Journal of Industrial and Engineering Chemistry》2012,18(2):822-825
Bench-scale soil washing experiments were conducted to remove Zn from contaminated soils. Various washing solutions including hydrochloric acid (HCl), nitric acid (HNO3), sodium hydroxide (NaOH), oxalic acid (HOOCCOOH·2H2O), sulfuric acid (H2SO4), phosphoric acid (H3PO4), and tartaric acid (C4H6O6) were used. The concentration of the washing solutions used in this study ranged from 0.1 M to 2 M with a liquid to solid ratio of 10. The soil washing results showed the following order of washing solution decreasing effectiveness for the removal of Zn: HCl > HNO3 > H2SO4 > H3PO4 > C4H6O6 > HOOCCOOH·2H2O > NaOH. 相似文献
11.
《Journal of aerosol science》1999,30(4):533-548
Experimental measurements on the deposition of cigarette smoke particles (CSP) in the human airways have produced results that are inconsistent with typical deposition data based on particle size. Previous work relating to hygroscopic growth indicates that hygroscopicity alone can not account for this discrepancy. The present study investigates coagulation of CSP modeled as a polydisperse-charged aerosol as a possible explanation. The results of the model more accurately predict the experimental coagulation data for mainstream CSP than models that treat CSP as a monodisperse or polydisperse-uncharged aerosol. An aerosol with an initial charge distribution based on Boltzmann equilibrium yields slightly larger coagulation rates than the mainstream CSP polydisperse-charged model. The numerical results indicate that the size and charge distribution of sidestream CSP, with a concentration of 106 particles cm-3, remain stable. In 2 s, the size distribution of mainstream CSP, with a concentration of 109 particles cm-3, shifts to a larger size while becoming flatter and wider. The diameter of average mass increases from 0.29 to 0.5 μm. Numerical results confirm experimental reports for mainstream CSP, which indicate that the total number of charged particles increases with time and, in the early stages of coagulation, the amount of charge per particle cannot be estimated based on the particle size. This study shows that polydisperse-charged CSP, allowed to coagulate for 2 s in the mouth, will not produce size distributions that yield the observed deposition of CSP. However, additional coagulation will take place as the CSP travels through the respiratory tract, which will be investigated in future work. 相似文献
12.
The catalysts SO42 − Mn–Co–Ce/TiO2/SiO2 were investigated for the low-temperature SCR of NO with NH3 in the presence of SO2. An excellent SO2 durability at low temperature was obtained with the catalyst used TiO2/SiO2 as support and modified with SO42 −. The catalyst sulfated with 0.1 mol/L H2SO4 solution and then calcined at 300 °C exhibited the best NOx conversion efficiency of 99.5% at 250 °C in the presence of 50 ppm SO2. The conversion efficiency did not decrease after repeatedly used for 8 times. 相似文献
13.
High oxygen content (10–15 at.%) nanotextured carbons were obtained by pyrolysis of seaweeds at 600–750 °C and applied as electrodes for supercapacitors in H2SO4, KOH and Na2SO4 aqueous media. Interestingly, the potential stability window measured in a three-electrode cell configuration depends both on the nature of the oxygenated surface functionality and on the electrolyte pH. A high value of 2.4 V was observed in Na2SO4 for the seaweeds pyrolysed at 600 °C, showing that the surface functionality strongly influences the over-potentials of di-hydrogen evolution and carbon oxidation. Symmetric capacitors built from the seaweed carbons exhibited an excellent cycle life for voltage values up to 1.6 V, showing the promise of Na2SO4 for developing high energy density and environment friendly systems. 相似文献
14.
L. Jaideva Singh N. Shantibala Devi S. Pramodini Devi W. Bembee Devi R.K. Hemakumar Singh B. Rajeswari R.M. Kadam 《Inorganic chemistry communications》2010,13(3):365-368
Four new Cu(II) Complexes viz. [Cu(II)(1-amidino-O-methylurea)2]SO4·2H2O (1), [Cu(II)(1-amidino-O-ethylurea)2](SO4)2·2H2O (2), [Cu(II)(1-amidino-O-n-propylurea)2] SO4·2H2O (3), [Cu(II)(1-amidino-O-n-butylurea)2]2(SO4)2·2H2O (4) have been synthesized and characterized. EPR spectrum of complex 4 at RT consisted of fine-structure transitions (ΔMs = ±1) with zero-field splitting (ZFS) of 0.0485 cm?1 and a half-field signal (ΔMs = ±2) at ca. 1600 G, revealed formation of binuclear complex (S = 1). Whereas EPR spectrum of complex 2 in DMSO showed a mixture of mononuclear and binuclear complex in the ratio 0.75:1.0 with ZFS of 0.0385 cm?1. From the temperature dependence of the EPR signal intensity, the isotropic exchange-interaction constant J was evaluated. 相似文献
15.
Hak-Joo Lee H. Li Hyeongtag Jeon Wook-Seong Lee 《Diamond and Related Materials》2010,19(11):1393-1400
Some novel aspects of nanocrystalline diamond (NCD) film nucleation and growth by DC-PACVD were investigated, which focused on the effect of methane injection timing at ramp stage (see discussion in the text) and cathode temperature as well. NCD films were deposited for 4 h on a 4 in. Si wafer which was ultrasonically seeded in a methanol slurry of diamond powder with a 5 nm average diameter. The H2/CH4/N2 gas mixture with a composition of 96.7%/3%/0.3% was used as precursor gas. The total gas flow rate and chamber pressure were 150 sccm and 150 Torr, respectively. Discharge voltage and current of 500 V and 45 A were used respectively at a substrate temperature of 800 °C. The nucleation density, microstructure, growth rate and crystallinity of the obtained NCD films were characterized by SEM, XRD, NEXAFS and Raman spectroscopy. The nucleation density was found to be sensitive to methane injection timing in the ramp stage. In addition, the cathode temperature greatly affected the nucleation density, grain size and growth rate. 相似文献
16.
《Inorganic chemistry communications》2007,10(2):159-162
The title layered double salt Mn3(OH)2(SO4)2(H2O)2 · K2SO4 (1) was obtained from a simple hydrothermal reaction of CdSO4 · 8/3H2O, MnCl2 · 4H2O, α-aminopyridine (apy) and KI. X-ray analysis reveals that the two-dimensional (2-D) sheet of 1 is built up of the dimers of edge-sharing Mn(1) octahedral, extended by the apices of Mn(2) octahedral together with μ3 and μ4 SO4 groups. With free K+ ion as guest species, the 2-D sheets are further self-assembled into a 3-D supramolecular network with 1-D channels through the Ow-H ⋯ O hydrogen-bonded interactions. The magnetic property of 1 was investigated, and a classical behavior is observed with an antiferromagnetic order below 12.5 K. 相似文献
17.
《Journal of aerosol science》1999,30(4):479-488
The Aerosizer (Amherst Process Instruments, Inc. Hadley MA) is a time-of-flight instrument frequently used to measure the size distribution of an aerosol. However, if the Aerosizer’s counting efficiency, defined as the number of particles counted divided by the total number entering the instrument, is not 100% or varies with particle size, the resulting size distribution will be inaccurate.Experiments were conducted to determine the effect of particle diameter, particle concentration, photomultiplier tube (PMT) voltage, and model type on the Aerosizer’s counting efficiency. To calculate counting efficiency, the number of particles between 0.3 and 10 μm recorded by the Aerosizer was divided by the number of particles of the same size collected on each stage of a cascade impactor.Particle diameter, aerosol concentration, Aerosizer model, PMT voltage, and the diameter interaction terms influenced counting efficiency. Counting efficiencies were less than 1% for particles smaller than 0.45 μm, and more than 100% for particles larger than 7 μm. Increasing the PMT voltage increased the counting efficiency for the smaller particles, but also created false, larger particles. Counting efficiency decreased as count rate increased for count rates greater than 20,000 particles per second. The Aerosizer LD counted particles more efficiently than the Aerosizer Mach 2 because of improved laser and optics systems. Four regression models that relate counting efficiency to the salient operating parameters were developed, one for each combination of Aerosizer model and photomultiplier tube voltage studied. 相似文献
18.
《Applied catalysis. B, Environmental》2002,35(3):227-234
Ex-framework FeMFI catalysts, prepared by isomorphous substitution of iron in the aluminosilicate or gallosilicate MFI-type framework and activation by calcination at 823 K and steaming (300 mbar H2O in N2) at 873 K, show high activity and stability in N2O decomposition in the presence of O2, CO2, H2O, and SO2. The N2O conversion of the ex-framework catalysts in simulated tail-gas mixtures was >80% at 800 K and 75,000 h−1. The specific activity per mole of Fe (turnover frequency, TOF) of the ex-framework catalysts in N2O–He is four to nine times higher than observed for catalysts prepared by conventional solid and liquid-ion exchange, and sublimation methods. The stability of ex-framework catalysts for the direct N2O decomposition, in the absence of any reductant, is remarkable, showing no significant deactivation (at N2O conversion levels ranging from 20 to 65%) after 600 h on stream. Sublimed and especially ion-exchanged FeZSM-5 catalysts show a strong irreversible deactivation in feed mixtures containing H2O and SO2. The effect of SO2 on the catalytic performance of FeMFI catalysts is discussed, as well as the applicability of the ex-framework FeMFI catalysts in fluid-bed combustion facilities. 相似文献
19.
《Ceramics International》2016,42(12):14107-14112
Stabilized Al2TiO5 (AT)-mullite (M) porous ceramics were fabricated by starch consolidation casting using corn starch as curing agent and their microstructure, mechanical properties, pore size distribution and corrosion resistance were examined. Results showed that AT-M porous ceramic with the flexural strength of 11.5 MPa, apparent porosity of about 54.7% and pore size distribution in the range of 1–15 µm could be obtained with 10 wt% corn starch addition. Corrosion resistance results showed mass losses in hot H2SO4 solution and NaOH solution for 10 h to decreased from 1.03% to 0.36% and 4.39–2% when the calcination temperature increased from 1400 °C to 1450 °C, which proved these AT-M porous ceramics to possess an excellent corrosion resistance in acidic condition when calcined at 1450 °C. 相似文献
20.
A new process that coupled the reaction and separation in the production of biodiesel from feedstocks with Free Fatty Acids (FFAs) was studied. A novel solid acid catalyst, sulfonated-multiwalled carbon nanotubes (s-MWCNTs), was used in the synthesis of biodiesel from methanol and oleic acid in a 250 mL autoclave. s-MWCNTs with different concentrations of –SO3H were produced from the treatment of MWCNTs with concentrated H2SO4 (96%) at 120–210 °C, and were characterized by SEM/EDS and FTIR analysis. Recycling of the methanol phase was used to separate the water produced from the reaction mixture, which increased the esterification conversion substantially and decreased the acidity of the product. A conversion of oleic acid of 95.46 wt.% was obtained with a catalyst/oleic acid mass ratio of 0.20%, methanol/oleic acid molar ratio of 5.8, temperature of 135 °C, and reaction time of 1.5 h. By removing water from the reaction mixture and adding the recycling of the methanol steam, the conversion of oleic acid was increased to 99.10 wt.% after 1 h. 相似文献