烷烃混合气体的太赫兹光谱分析

太赫兹时域光谱技术(THz-TDS)是近十多年发展起来的一种新的远红外光谱技术,在气体研究方面有了一定进展,尤其是对极性气体,而对非极性气体研究较少。本文以干馏气、天然气以及各种沼气的主要成分CH₄, C₂H₆和C₃H₈气体(非极性气体)为研究对象,首先对CH₄,C₂H₆和C₃H₈三种纯气进行测量,利用THz-TDS技术得到其太赫兹频域谱和相位谱,然后将其以不同比例、不同种类混合成二元气体,进一步研究混合气体的频域谱和相位谱。实验结果表明CH₄,C₂H₆对太赫兹波的吸收很小而C₃H₈对太赫兹波有一定的吸收,这与C₃H₈极性增强的物理特性相符合。为了实现对烷烃混合气体的压强和各成分浓度的定量分析,本文利用BP人工神经网络法对上述二元混合体系的太赫兹频域谱进行分析,对训练集和预测集分别计算了混合气体的压强和各成分浓度的预测值与实际值的相关系数,训练集和预测集的相关系数取值分别为0.994～0.999和0.981～0.993。研究表明,利用太赫兹时域光谱技术结合BP人工神经网络数学方法可以实现对烷烃混合气体的压强和各成分浓度的定量分析,使THz-TDS技术在气体领域研究范围更加广阔。     

Comparison of reactivity of alkane hydroxylation with intact cells and cell- free extracts ofMethylosinus trichosporium OB3b

Kinetic studies for hydroxylation of a series of alkanes (methane, ethane and propane) with intact cells and cell-free extracts ofMethylosinus trichosporium OB3b were carried out.K _m values for alkane hydroxylation with cell-free extracts were lower than those with intact cells, suggesting that cytoplasm plays an important role in the solubility of alkanes to increase their concentration.     

近红外光谱烷烃类气体定量分析系统的研究

介绍了一种近红外光谱烷烃类气体在线定量分析测量方法.该方法以单片闪耀光栅为核心构成分光系统,分析计算了分光系统的关键参数,设计构建了硬件系统平台,完成了窄带光束实验测试和烷烃类七种单组分气体光谱探测实验.实验表明,入射狭缝为2 mm时,分光系统在中心波长1 200～1 800 nm波段内能够分离谱宽为10 nm的窄带光...     

The Interfacial Tension and Alkane Carbon Number (nmin) of Alkyl Benzene Sulfonates in Relation to Enhanced Oil Recovery. Part I: Effect of Surfactant Molecular Weight/Temperature and Electrolyte on nmin

Twelve anionic monoisomeric surfactants based on the alkyl benzene sulfonic acid were prepared. In two sets of experiments, the (n_min) values were determined at 28 and 70°C for them. The n-hydrocarbon scans (n-C₅ to n-C₁₈) against the interfacial tension were used to determine the (n_min) values. The factors affecting (n_min) such as; molecular weight, branching of side chain, temperature and electrolyte addition were investigated. From the obtained results, it was found that the surfactants which has the highest molecular (8φ C₁₅ ABS) gave (n_min) equal 8, so it can be used in the enhanced oil recovery(EOR) without additives (the suitable (n_min) for EOR between 7-9). Otherwise, the lowest molecular weight surfactant (7φ C₁₃ ABS) gave (n_min) equal 5 without addition of alcohols or electrolyte. This case needs some additives to adjust the (n_min) in the range of 7 to 9. By investigation the factors affecting (n_min), it was found that the side chain of alkyl benzene shifted the (n_min) to the highest values. The increasing of temperature decreased the (n_min) values. Also, it was found that the (n_min) increased to high value by adding the electrolytes and alcohols. The mixture between surfactants with and without side chain shifted the (n_min) to the highest value. Using these parameters, the alkane carbon number (n_min) can be used to select the suitable solvent during the preparation of emulsion to get the minimum interfacial tension at which the maximum emulsion stability should be obtained and also to select the surfactant for EOR.     

Cation effect of ammonium imide based ionic liquids in alcohols extraction from alcohol-alkane azeotropic mixtures

During recent last years, outstanding properties of ionic liquids such as low melting point, large liquid range and negligible volatility have turned them into possible volatile organic solvents replacers to break alcohol-alkane azeotropic mixtures. On this basis, two ionic liquids, butyltrimethylammoniumbis(trifluoromethylsulfonyl)imide, [BTMA][NTf₂], and tributylmethylammoniumbis(trifluoromethylsulfonyl)imide, [TBMA][NTf₂], were studied through ternary liquid+liquid equilibrium (LLE) of {alkane(1) + alcohol (2) + IL(3)} at T = 298.15 K and atmospheric pressure in order to consider the effect of ionic liquid cation alkyl chain length on the extraction process.The ILs capability as azeotrope breakers was determined by the calculation of parameters such as solute distribution ratio, β, and selectivity, S and this capability was compared with other bis (trifluoromethylsulfonyl)imide based ionic liquids from literature. The consistency of tie-line data was ascertained by applying the Othmer–Tobias and Hand equations. Finally, the experimental LLE were correlated by the Non Random Two Liquid (NRTL) thermodynamic model.     

Are safe results obtained when the PC-SAFT equation of state is applied to ordinary pure chemicals?

The PC-SAFT equation of state is a very popular and promising model for fluids that employs a complicated pressure-explicit mathematical function (and can therefore not be solved analytically at a specified pressure and temperature, contrary to classical cubic equations). In this work, we demonstrate that in case of pure fluids, the PC-SAFT equation may exhibit up to five different volume roots whereas cubic equations give at the most three volume roots (and yet, only one or two volume roots have real significance). The consequence of this strongly atypical behaviour is the existence of two different fluid–fluid coexistence lines (the vapour-pressure curve and an additional liquid–liquid equilibrium curve) and two critical points for a same pure component, which is obviously physically inconsistent. In addition to n-alkanes, nearly 60 very common pure components (branched alkanes, cycloalkanes, aromatics, esters, gases, and so on) were tested out and without any exception, we can claim that all of them exhibit this undesired behaviour. In addition, such similar phenomena (i.e. existence of more than three volume roots) may also arise with mixtures. From a computational point of view, most of the algorithms used for solving equations of state only search for three roots at the most and are thus likely to be inefficient when an equation of state gives more than three volume roots. To overcome this limitation, a simple procedure allowing to identify all the possible volume roots of an equation of state is proposed.     

Metal-Organic Frameworks for C6 Alkane Separation

The separation of alkane isomers is an important yet challenging process in the petrochemical industry. Being a crucial step to produce premium gasoline components as well as optimum ethylene feed, the current industrial separation by distillation is extremely energy intensive. Adsorptive separation based on zeolite is limited by insufficient adsorption capacity. Metal-organic frameworks (MOFs) hold enormous promise as alternative adsorbents due to their diverse structural tunability and exceptional porosity. Precise control of their pore geometry/dimensions has led to superior performance. In this minireview, we highlight the recent progresses in developing MOFs for the separation of C6 alkane isomers. Representative MOFs are reviewed based on their separation mechanisms. Emphasis is put on the material design rationale for achieving optimal separation capability. Finally, we briefly discuss the existing challenges, possible solutions, and future directions of this important field.