喷气燃料中胶质化合物的质谱分析

喷气燃料中的不安定组分对燃料安定性影响很大,不安定组分主要集中在胶质化合物中,胶质化合物的存在会增加燃烧积炭,影响航空发动机的正常使用[1-2]。不安定组分含量极少,必须通过一定条件的分离和富集才能进行分析和评价。本文采用中性氧化铝吸附和极性溶剂脱附的方法分离制备     

Raman studies of hydrogen adsorbed on nanostructured porous materials

Raman spectroscopy was applied to study the adsorbed hydrogen phase in porous materials at room temperature and under cryogenic conditions. A comparison between the Raman spectra of H(2) molecules adsorbed on single walled carbon nanotubes and on a Cu-based metal-organic framework reveals that the interaction strength for the adsorption of molecular hydrogen is very similar in these materials. In both cases the small perturbation of the Raman spectrum of hydrogen indicates that adsorption takes place without any evident charge transfer between H(2) and the adsorbent. Additionally for single walled carbon nanotubes at least two types of adsorption sites could be identified by Raman spectroscopy.     

Genesis of the active-component precursor in the synthesis of Pt/Al2O3 catalysts: II. Synthesis of platinum hydroxo complexes on the alumina surface as precursors of the active component of Pt/Al2O3 catalysts

The thermal hydrolysis of chloroplatinate adsorbed on γ-Al₂O₃ is a possible approach to the synthesis of surface platinum hydroxo complexes as precursors to the active component of supported platinum catalysts. It is demonstrated by EXAFS and diffuse reflectance spectroscopy that the surface chloro complexes undergo deep hydrolysis under hydrothermal conditions at various processing times and temperatures. The average oxygen coordination number of platinum in these complexes is as large as 4.5. According to gradient elution data obtained using both the competitive replacement of adsorbed complex anions and variation of the charged state of the oxide surface, the resulting hydrolyzed precursor differs from the conventional chloride precursor in the nature of binding to the surface and interacts with alumina via a coordination mechanism.     

Photochemistry of adsorbed nitrate

In the atmosphere, gas-phase nitrogen oxides including nitric acid react with particle surfaces (e.g., mineral dust and sea salt aerosol) to yield adsorbed nitrate, yet little is known about the photochemistry of nitrate on the surface of these particles. In this study, nitrate adsorbed on alumina surfaces, a surrogate for mineral dust aerosol, is irradiated with broadband light (lambda > 300 nm) in the absence and presence of coadsorbed water, at <1% and 45 +/- 2% relative humidity (%RH), respectively, and molecular oxygen. Upon irradiation, the nitrate ion readily undergoes photolysis to yield nitrogen-containing gas-phase products, NO2, NO, and N2O. Although NO2, NO, and N2O form under the different conditions investigated, both coadsorbed water and molecular oxygen change the gas-phase product distribution, with NO being the major product under dry and humid conditions in the absence of molecular oxygen and NO2 the major product in the presence of molecular oxygen. To the best of our knowledge, this is the first study to investigate the role of solvation by coadsorbed water in the photochemistry of adsorbates at solid interfaces and the roles that molecular oxygen, adsorbed water, and relative humidity may have in photochemical processes on aerosol surfaces that have the potential to alter the chemical balance of the atmosphere.     

Quinolium Dichromate Adsorbed on Alumina: A Mild,Convenient, and Inexpensive Reagent for Cleavage of C˭N Under Nonaqueous Conditions

Oximes, hydrazones, and semicarbazones are converted to the corresponding carbonyl compounds using quinolium dichromate adsorbed on alumina (QDC/alumina) under nonaqueous conditions.     

Surface reactions of dimethyl ether on γ-Al2O3

The surface reactions of dimethyl ether (DME) on industrial alumina (γ-Al₂O₃) were studied by chromatographic analysis of the products at the outlet of the flow reactor and (independently) by diffuse reflectance IR spectroscopy. The major products of the reactions at 250°С were found to be methanol formed in the reaction of DME with hydroxyl groups (the 3720 and 3674 cm^–1 bands in the diffuse reflectance spectrum) and various methoxy groups (the 1121, 1070, 695, and 670 cm^–1 bands in the differential spectra). The presence of molecularly adsorbed methanol was confirmed by experiments with methanol fed in a high-temperature IR cell. The interaction of the resulting methanol molecule with the hydroxyl group led to the formation of a water molecule in the gas phase and a methoxy group on the oxide surface. Strong adsorption of molecular DME was revealed, which was favored by an increase in the temperature of the preliminary calcination of oxide from 250 to 450–500°С; treatment of alumina with water vapor after its preliminary contact with DME led to a recovery of the hydroxyl coating and a replacement of molecularly adsorbed DME with hydroxyl. The thermal effect recorded in a flow reactor was positive during the adsorption of DME and negative during the desorption of weakly bonded DME. Schemes of formation of methoxy groups in the interaction of DME and methanol with surface hydroxyls were suggested.     

Spectral reconstruction of surface adsorbed species using band-target entropy minimization. Application to CO and NO reaction over a Pt/gamma-Al2O3 catalyst using in situ DRIFT spectroscopy

The adsorption of NO and CO was studied on an alumina-supported platinum catalyst by in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS). The temperature range was 50-160 degrees C and a wide variety of partial pressures was used. The band-target entropy minimization (BTEM) algorithm was applied to the DRIFTS data sets resulting in the pure component spectra of numerous species adsorbed on both the Pt (primarily a variety of Pt0-CO and Pt2+ -CO species) and alumina surface (i.e. nitrates, nitrites, bicarbonates, isocyanates) as well as gas-phase species. Thirty-one previously known species were identified as well as 6 new and previously unreported or previously unassigned spectra. The present results indicate that BTEM analysis of DRIFTS data is a very promising tool for the study of heterogeneous catalytic in situ spectroscopic data.     

Diffuse reflectance FTIR study of the interaction of alumina surfaces with ozone and water vapor

The interaction of ozone with alumina has been examined at ambient temperature as a function of ozone concentration and relative humidity. The experiments used diffuse reflectance FTIR spectroscopy in a small flow reactor, which provided control of the temperature, pressure, and composition of the gas mixture to which the sample was continuously exposed. Treatment of alumina with ozone produced a new spectroscopic feature at 1380 cm(-1), which we attribute to an aluminum oxide species formed by interaction of O3 with Lewis acid sites on the alumina surface. After exposure of the alumina sample to O3 was stopped, subsequent exposure of the sample to humidified nitrogen resulted in the slow removal of the peak at 1380 cm(-1). Simultaneously, the uptake of water by the alumina increased as indicated by the growth of the adsorbed water features which extend from approximately 3700 to 2500 cm(-1). Treatment of dry alumina with humidified ozone strongly inhibited both the rate of formation of the spectral feature at 1380 cm(-1) and its limiting extent of formation. These observations are analyzed in terms of the adsorption and surface reaction properties of ozone on alumina. The observation that the new oxide feature on alumina, produced by reaction with ozone, can be removed by water is important for assessing the ability of mineral dust aerosols to process atmospheric trace gases over a significant time scale. We believe the work reported here to be the first direct and quantitative kinetic study of the competition between O3 and water for adsorption sites on alumina.     

Fluoride wastewater treatment by adsorption onto metallurgical grade alumina

The adsorption of fluoride onto metallurgical grade alumina (to produce Al) was investigated under different conditions: pH, contact time and adsorbent concentration. Data were evaluated with the aim of developing an alternative treatment technology for washing wastewater arising from an Aluminum can production plant. Kinetics and adsorption isotherms data have been also produced Sorption is greatly affected by pH and the best condition for fluoride removal are obtained at pH 5-6 and alkalinity competes successfully with fluoride ions for the exchange sites. Experiments with fixed beds indicate that fluoride is removed from wastewater by metallurgical-grade alumina with a capacity of 12.21 mg of F per gram and adsorption increases of about 25% at appropriate pH. The Mass Transfer Zone at 5% of the breakthrough occupies 70.6% of the total column length. The optimization of aluminum precipitation by pH adjustment and with different precipitant agents has been done.     

Determination of the fluorescence properties of polynuclear aromatic hydrocarbons in the vapor phase and adsorbed on solid supports by laser-induced molecular fluorescence

The fluorescence properties (lifetimes and spectra) of anthracene and fluoranthene were found to be independent of temperature in the ranges 80–110°C and 60–95°C, respectively, in vacuum and in helium, nitrogen, and air atmospheres. The fluorescence lifetimes and spectra were also measured for these two compounds individually adsorbed on silica, alumina, magnetite, or hematite. In all cases, the emission profiles for the adsorbed aromatic hydrocarbon were red-shifted with respect to the gas-phase spectra. The fluorescence lifetimes for both anthracene and fluoranthene increased for the different supports in the order alumina < silica < magnetite < hematite.     

ESR study of radiation-induced polymerization of methyl methacrylate on solid surfaces

ESR spectra of methyl methacrylate (MMA) adsorbed on solid surfaces such as silica, alumina, and CPG-10 show a seven-line absorption due to monomer radicals when γ-irradiated at ?196°C. These spectra turn into conventional nine-line spectra by annealing at ?86°C as a result of polymerization. The intensity ratio of the four-line component to the five-line component changes with further polymerization. The ratio depends on the kind of solid and the smallest value is obtained in the spectra of alumina-MMA. The temperature of irradiation strongly affects the value in alumina-MMA. These results suggest that MMA is strongly adsorbed and deformed the conformation on alumina surface.     

巯基微球富集用于近红外光谱同时定量分析微量汞(Ⅱ)和银(Ⅰ)离子

针对近红外光谱技术的检出限高和金属离子在近红外区无信号响应的问题, 合成了巯基聚倍半硅氧烷微球(PMPSQ), 用以高效富集水溶液中的微量汞(Ⅱ)和银(Ⅰ)离子. 通过金属离子与巯基官能团螯合从而获得相应的近红外信号响应, 采集吸附了金属离子的PMPSQ的近红外漫反射光谱, 采用偏最小二乘法建立了定量校正模型. 结果表明, 采用巯基微球富集结合近红外光谱技术可以同时测定水中浓度分别为0.16~1.80 mg/L的汞(Ⅱ)离子和0.15~1.70 mg/L的银(Ⅰ)离子.     

Segmental dynamics of poly(styrene-b-2-vinylpyridine) in bulk and at the surface/air interface

Anionically polymerized poly(α-deuterostyrene) and poly(β-deuterostyrene-b-2-vinylpyridine) (DSVP), selectively deuterated on the styrene backbone, were studied using deuterium wide-line NMR in bulk and adsorbed on silica and alumina. Changes in the segmental dynamics of the bulk and adsorbed polymers were inferred via changes in the NMR line shape with temperature. The DSVP bulk sample, which consisted of micellar aggregrates with a 2-vinylpyridine core, was more rigid than the homopolystyrene of a similar molecular weight. A significant change in mobility occurred at 20°C higher in the DSVP bulk sample than it did in homopolystyrene. The DSVP-adsorbed sample showed more restrictive mobility than bulk DSVP. The spectra of the adsorbed samples contained “rigid” Pake patterns with considerable intensity at temperatures where the collapse of the Pake pattern for the DSVP bulk sample was observed. DSVP bound to the silica surface was found to have a mobility similar to the same copolymer on alumina. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1609–1616, 1998     

FT-IR study on CO<Subscript>2</Subscript> adsorbed species of CO<Subscript>2</Subscript> sorbents

The stability of amine-functionalized silica sorbents prepared through the incipient wetness technique with primary, secondary, and tertiary amino organosilanes was investigated. The prepared sorbents were exposed to different gaseous streams including CO₂/N₂, dry CO₂/air with varying concentration, and humid CO₂/air mixtures to demonstrate the effect of the gas conditions on the CO₂ adsorption capacity and the stability of the different amine structures. The primary and secondary amine-functionalized adsorbents exhibited CO₂ sorption capacity, while tertiary amine adsorbent hardly adsorbed any CO₂. The secondary amine adsorbent showed better stability than the primary amine sorbent in all the gas conditions, especially dry conditions. Deactivation species were evaluated using FT-IR spectra, and the presence of urea was confirmed to be the main deactivation product of the primary amine adsorbent under dry condition. Furthermore, it was found that the CO₂ concentration can affect the CO₂ sorption capacity as well as the extent of degradation of sorbents.     

Speciation of Cr(III) and Cr(VI) in potable waters by using activated neutral alumina as collector and ET-AAS for determination

The speciation of Cr(III) and Cr(VI) has been performed by using activated neutral alumina as adsorbent. Both species were quantitatively adsorbed on a small column filled with neutral alumina. The adsorbed Cr(III) was eluted with 4 mol L(-1) HNO(3) and Cr(VI) with 1.0 mol L(-1) ammonia solution. Recoveries of Cr(III) and Cr(VI) were 99% and 100%, respectively. Using ET-AAS for Cr determination the limit of detection in the sample was 0.01 microg L(-1). The combined procedure is fast and sensitive. It can be applied for routine analysis of water samples at sub-microg L(-1) levels with a relative standard deviation (RSD) of 2-10% (three determinations).     

Structural analysis of reactive dye species retained by the basic alumina surface

The alumina-dye composites were prepared by treating the basic alumina with the water solutions of Reactive Red 120 (RR 120) and Reactive Blue 15 (RB 15) dyes. The bands of low intensities in the 1400–1600 cm⁻¹ region and at 783 cm⁻¹ in the IR spectra of these composites point out that the dye species is bound weakly to the surface. In the case of mechanochemical adsorption of dye molecules, the asymmetric and symmetric S(=O)₂ and the S-O-C stretching bands together with the vibrations of aromatic ring revealed that dye types under dry conditions interacted effectively with alumina surface. After the heating of the alumina dye complexes in the temperature range 150–350°C, the intensities of the IR and XRD peaks for adsorbed types decreased. The endothermic peaks over 200°C and the bigger total mass losses for the alumina-dye composites can be ascribed to the decomposition of dye species retained by the alumina surface. The mass losses on TG curves of the alumina-dye complexes up to ∼800°C exhibit the removal of black residues occurred by decomposition of first adsorbed products. The thermal analysis data also point out that the water molecules bonded strongly to the alumina surface and dye types compete to accommodate at the surface active sites.     

An Efficient One-Pot Synthesis of Nitriles from Carboxylic Acids Without Solvent Under Microwave Irradiation

Nitriles were prepared from alkyl and aryl carboxylic acids in dry media conditions, under microwave irradiation. Heating of the carboxylic acid, urea and amidosulfonic acid adsorbed on alumina support in a microwave oven affords nitriles in 20–93% yields.     

An infrared and inelastic neutron scattering spectroscopic investigation on the interaction of eta-alumina and methanol

The industrially important interaction of methanol with an eta-alumina catalyst has been investigated by a combination of infrared spectroscopy (diffuse reflectance and transmission) and inelastic neutron scattering (INS) spectroscopy. The infrared and INS spectra together show that chemisorbed methoxy is the only surface species present. Confirmation of the assignments was provided by a periodic DFT calculation of methoxy on eta-alumina (110). The thermal conversion of adsorbed methoxy groups to form dimethylether was also followed by INS, with DFT calculations assisting assignments. An intense feature about 2600 cm(-1) was observed in the diffuse reflectance spectrum. This band is poorly described in the extensive literature on the alumina/methanol adsorption system and its observation raised the possibility of a new surface species existing on this particular catalyst surface. INS measurements established that the 2600 cm(-1) feature could be assigned to a combination band of the methyl rock with the methyl deformation modes. This assignment was reinforced by an analysis of the neutron scattering intensity at a particular energy as a function of momentum transfer, which confirmed this particular adsorbed methoxy feature to arise from a second order transition. Similar behaviour was observed in the model compound Al(OCH3)3. The anomalous infrared intensity of the 2600 cm(-1) peak in the diffuse reflectance spectrum is a consequence of the different absorption coefficients of the C-H stretch and the combination mode. The implications for catalyst studies are discussed.     

Trimethylammonium Chlorochromate Adsorbed on Alumina: An Efficient and Convenient Reagent for the Oxidative Cleavage of 4-Phenylsemicarbazones and Semicarbazones to Their Parent Carbonyl Compounds

Deprotection of 4-phenylsemicarbazones and semicarbazones to their parent aldehydes and ketones in high yields has been carried out by using trimethylammonium chlorochromate adsorbed on alumina as selective oxidant under mild conditions.     

Adsorption and catalytic properties of peroxidase

The adsorption of peroxidase was studied on ten silicate adsorbents, aluminosilicate, and alumina. It was shown that its value depended on both the parameters of the porous structure and the nature of the adsorbent. The maximum adsorption values were obtained on biporous silicate adsorbents and biporous aluminosilicate. It was established that the adsorbed peroxidase layers on these adsorbents had the best catalytic properties as well. It was shown that the specific activity of the enzyme depended on the degree of the surface filling.