Gas/particle partitioning and size distribution of primary and secondary carbonaceous aerosols in public buildings

The gas and particulate phase of semi-volatile organic compounds (six samples) and the composition of organic aerosol as a function of particle size (six samples) were studied in two public buildings in Greece. The objectives of this study were: i) to chemically characterize the organic content of indoor gas and particulate phases; ii) to classify indoor organic aerosol constituents as a function of particle size; and iii) to reconcile the sources of organic compounds indoors. Non-polar, semi-polar, polar, and acidic compounds were identified in both gas and particulate phases by using gas chromatography/mass spectrometry (GC/MS). Branched iso- and anteiso-alkanes were used to trace environmental tobacco smoke (ETS) concurrently with other compounds. Polycyclic aromatic hydrocarbons (PAHs) in the gas phase gave a pattern more characteristic to ETS than the corresponding pattern in the particulate phase. The chemical composition observed for n-alkanols and n-alkanoic acids in both gas and particulate phases indicated ETS as one of their main sources indoors. PAHs and n-alkanols were evenly associated between fine and coarse particles and their corresponding total mean mass median aerodynamic diameter (MMAD) was 1.27 and 1.38 microns respectively, indicating a mixed origin. Conversely, the MMAD of n-alkanes, unresolved complex mixture (UCM), iso- and anteiso-alkanes and free fatty acids varied from 0.30 to 0.62 micron denoting a stronger association with indoor sources.     

Modeling Alkane and Haloalkane Mixture Viscosities in a Three-Parameter Corresponding States Format

The fundamental structure of the model is based upon a detailed and innovative conformality analysis of the viscosity surfaces of pure fluids similar to that proposed for thermodynamic properties [G. Scalabrin et al. Fluid Phase Equilib. 170:23 (2000); Int. J. Refrig. 26:35 (2003)], resulting in the introduction of a new specific scaling parameter for viscosity, defined by a single experimental viscosity value. The model structure is based on two reference fluids for which pure-fluid viscosity dedicated equations (VDE) are available, which in this work are ethane and propane. The model is then extended to mixtures following the classical corresponding states (CS) one fluid model using mixing rules without interaction parameters. This gives the model a predictive character. It can be reliably applied in a wide range of pressure–temperature values, in both liquid and vapor phases, due to the validity ranges of the reference equations. The investigated mixtures include binary and multicomponent systems of both light and heavy n-alkanes and halogenated alkanes including R134a, R125, R152a, R143a, R22, R142b, R32, and R124 as components. For both families of fluids, the accuracy in terms of absolute average deviation (AAD) is within 2.68% in the vapor phase and 3.0% in the liquid phase. The model has also been validated for strongly azeotropic mixtures such as R32–R290 and R134a–R290 giving interesting results by fitting the interaction parameters on a limited subset of data. The effectiveness of the proposed procedure is enhanced by the comparison with a recently published advanced theoretical model.Paper presented at the Sixteenth European Conference on Thermophysical Properties, September 1–4, 2002, London, United Kingdom.     

Thermal Conductivity Modeling of Refrigerant Mixtures in a Three-Parameter Corresponding States Format

A predictive model for the thermal conductivity (TC), in a corresponding states (CS) format, is proposed here for mixtures of homologous fluids such as the halogenated alkanes (HA) and the alkanes (A), most of which are used as refrigerants. The predictive nature of the model originates from a new study carried out for the TC of pure fluids. For the dilute-gas term the model requires an individual correlation for each component, whereas for the excess contribution the model structure makes use of TC dedicated equations (TCDEs) of two reference fluids, which in this work are methane and R134a. The mixture model adopts specific mixing rules for each of the two TC contribution terms: the dilute-gas term _0mix is obtained from the Mason and Saxena mixture model, while the excess term _{E mix} is determined from the Wong et al. mixing rules in the one fluid model approach. Setting the mixing rules interaction coefficients to unity, the resulting model presents a completely predictive character. The model has been tested on both liquid and vapor phases of the following systems: R32/R125, R32/R134a, R125/R134a, R404a, and R32/R134/R125. For a total of 1223 experimental points in the liquid phase, the overall AAD is 5.39%, while for a total of 2358 points in the vapor phase, the AAD is 2.62%. These predictive mode performances can then be regarded as particularly satisfactory and are of a level similar to the claimed experimental uncertainty. An improved version of the model is also proposed for modeling azeotropic mixtures. The results reached in this case for a total of 1989 experimental points give an average AAD of 5.30%. Considering both the predictive nature and the simple computational procedure of the model, it significantly enhances the calculations of the TC of mixtures.Paper presented at the Sixteenth European Conference on Thermophysical Properties, September 1–4, 2002, London, United Kingdom.     

Site requirements in the kinetics of alkane transformations catalysed by metals

Hydrogen pressure is often found to cause an inhibiting effect on the kinetics of alkane reactions on metal surfaces. The most common interpretation of such results is focussed on the degree of dehydrogenation of the active surface intermediate following a dissociative mechanism. A series of arguments will be given in favour of an associative mechanism in which the hydrocarbon reacts with an adsorbed hydrogen atom. In this mechanism, the adsorption site or “landing site” is composed of a chemisorbed hydrogen atom associated with an ensemble of “Z” potential sites. These sites are associated with the hydrogen chemisorption site. The validity of H₂ adsorption to determine the metallic dispersion will be also discussed. Contribution in honour of Dr. Alfred Frennet     

Olefin as an Intermediate in n-Butane Isomerization on Sulfated Zirconia. An In Situ 13C MAS NMR Study of n-Octene-1 Conversion

By using in situ ¹³C MAS NMR and ex situ GC-MS, the analysis of hydrocarbon products formed from n-octene-1 adsorbed on sulfated zirconia catalyst (SZ) has been performed. It is shown that a mixture of alkanes and stable alkyl substituted cyclopentenyl cations (CPC) is formed as the basic reaction products. Formation of both alkanes and CPC from n-octene-1, a precursor of C₈ ⁺ cation, the key intermediate in n-butane isomerization via a bimolecular pathway, implies that formation of the isomerized alkane occurs by a complex process of conjunct polymerization, rather than isomerization itself. CPC deposited on the SZ surface can be in charge of the catalyst deactivation.     

分子筛催化剂的研究进展

综述了常用分子筛催化剂的研究现状及发展趋势,总结了烷烃异构化的反应特点,介绍了具有代表性的中孔分子筛类催化剂、硅磷铝分子筛类催化剂、杂多酸等催化剂的合成方法、条件及应用前景。着重介绍了各类催化剂的性能和最新研究状况,具体包括MCM-41、SAPO-11、沸石分子筛等,同时对目前面临研究问题进行概述。最后指出绿色、中低温合成烷烃异构化催化剂将是未来的研究热点。     

超声辐射下双吲哚甲烷衍生物的合成

以吲哚、醛为原料,蒙脱土固载路易斯酸为催化剂,超声条件下合成双吲哚甲烷类衍生物。得到最优合成条件为n(吲哚)∶n(醛)=2.0∶1.1,蒙脱土负载氯化铜为催化剂,二氯甲烷作溶剂,反应温度为50℃,超声时间为15 min。产率最高达99.3%,催化剂循环3次产率仍可达81.3%。产物通过核磁、红外、熔点进行表征。     

One‐Step Fabrication of Uniform Biodegradable Microbeads with Unimodal and Bimodal Porous Structures Using Spontaneous Microphase Separation

Uniform poly(l ‐lactic acid) (PLLA) microbeads with unimodal or bimodal porous structures are fabricated using a simple fluidic device based on a single oil‐in‐water emulsion method, where an alkane (octane, undecane, tridecane, and pentadecane) serves as the porogen. During the solvent evaporation, the alkanes spontaneously undergo a microphase separation, resulting in a highly porous structure. The size and size distribution of the pores in the PLLA microbeads can be easily controlled by changing the alkane type and concentration. When the undecane, tridecane, and pentadecane are used as the porogen at 6 wt%, the PLLA microbeads have the bimodal porous structure with a large hollow pore in the center and many small pores. In vitro and in vivo studies reveal that those PLLA microbeads with the bimodal porous structure readily facilitate the penetration and proliferation of cells and host tissues compared with the other PLLA microbeads. These results indicate that the superior properties of PLLA porous microbeads with a bimodal porous structure are suitable for diverse biomedical applications such as tissue engineering, cell delivery, and plastic surgery.     

氯代烷的合成及应用

通过试验确定了用盐酸和醇为原料合成氯代烷的较佳工艺条件,得到了合格的助剂产品,在此工艺条件下,助剂收率可达到68%～69%。同时还考察了不同助剂对重芳烃副产的烷基化反应的影响,用合成的精制助剂对重芳烃副产进行烷基化反应,可使甲乙苯的转化率达到95%～96%。     

超临界二氧化碳-烷烃体系相平衡和界面张力的研究进展

超临界二氧化碳(SC-CO2)和烷烃体系的相平衡和界面张力是石油、化工及环境保护等诸多领域中的基础数据。对SC-CO2-烷烃二元体系的相平衡和界面张力的实验测定和理论模型方面的研究进展进行了综述,并分析了同时适用于SC-CO2-烷烃体系的本体和界面性质研究的自洽模型的发展方向。