PREDICTION OF MOLAR VOLUMES, VAPOR PRESSURES AND SUPERCRITICAL SOLUBILITIES OF ALKANES BY EQUATIONS OF STATE

A generalized cubic equation of state which can represent all the cubic equations is introduced and thermodynamic property relations for it are presented. Five cubic equations of states with respective mixing rules are used to predict molar volumes and vapor pressures of pure alkanes (from methane till n-tritriacontane) and solubilities of solid wax components (high molecular weight alkanes) in supercritical solvents. They are the RK (Redlich-Kwong), MMM (Mohsennia-Modarress-Mansoori), RM (Riazi-Mansoori), PR (Peng-Robinson), and SRK (Soave-Redlich-Kwon) equations of state. The experimental data necessary to compare the equations of state are taken from the literature. It is demonstrated that the SRK equation of state is more accurate for predicting vapor pressures of alkanes. The RM equation of state is shown to be more accurate for predicting molar volumes of saturated and sub-cooled liquid alkanes as well as molar volumes of alkanes in their supercritical condition. For the solubility of wax components in supercritical solvents it is shown that the MMM equation of state gives the least AAD% for the 270 data points of 10 binary systems studied consisting of a high molecular weight alkane and supercritical ethane and carbon dioxide.     

阻燃剂V6的合成研究

以三氯化磷、季戊四醇、氯气及环氧乙烷为原料,四氯化钛为催化剂,通过三步反应合成了阻燃剂V6——四(2-氯乙基)-2,2-二(氯甲基)-1,3-亚丙基二磷酸酯。用IR、元素分析对合成的阻燃剂V6进行了表征,并且对各步的反应条件进行了优化,最佳反应条件为:反应物配比n(季戊四醇)∶n(三氯化磷)∶n(氯气)∶n(环氧乙烷)为1∶2.5∶2.2∶4.2;各步的最佳反应时间依次是2h,3h,4h;适宜的反应温度分别为80°C,23～25°C,80°C。产率达93.5%。     

正辛烷脱氢生成直链烯烃的热力学分析

计算了不同反应条件下正辛烷脱氢生成直链烯烃的主反应热力学平衡参数。计算结果显示,ΔH随温度上升变化不大,正辛烷脱氢反应的平衡常数较小。反应平衡时的产物中,1 辛烯含量最少,顺 4 辛烯次之;产品中绝大部分是双键位于第2到第4碳的烯烃,并且反式辛烯的物质的量大于相应的顺式。温度是一个很敏感的热力学参数,随着温度的升高,正辛烷的平衡转化率呈较大幅度的增加;增加体系压力和氢/烃摩尔比可以明显降低正辛烷的平衡转化率,同时这些参数处于较低值时的影响较大。     

Highly effective P-modified HZSM-5 catalyst for the cracking of C4 alkanes to produce light olefins

A series of HZSM-5 zeolites modified by different amounts of phosphorus (P/HZSM-5) were prepared. The physicochemical features of P/HZSM-5 catalysts were characterized by means of XRD, BET, NH₃-TPD, FT-IR spectra of adsorbed pyridine, etc., and their performances for the catalytic cracking of the mixed C₄ alkanes to produce light olefins were investigated. The results indicated that phosphorus (P) modification not only modulated the amount of acidic sites and the percentage of weak acidic sites in total acidic sites, but also regulated the acid type, i.e., the ratio of L/B (Lewis acid/Brönsted acid). The introduction of P also altered the basic characteristics of HZSM-5 which was evidenced by CO₂-TPD analysis. Consequently, P modification with suitable amount was favorable for enhancing the selectivity to light olefins, especially to propene. At the temperature of 650 °C, the maximum yields of propene and ethene were achieved 25.6 and 33.9%, which were higher than those over parent HZSM-5 by 7 and 4.5%, respectively. Aromatics yield was found to be decreased with the increasing P loading due to the reduction of strong acid and the formation of new basic site which inhibited the hydrogen transfer reaction. All this indicates that P-modified HZSM-5 zeolites are effective catalysts for the cracking of mixed C₄ alkanes to produce more light olefins.     

Universal scaling of the charge transport in large-area molecular junctions

Charge transport through alkanes and para-phenylene oligomers is investigated in large-area molecular junctions. The molecules are self-assembled in a monolayer and contacted with a top electrode consisting of poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonic acid) (PEDOT:PSS). The complete set of J(V,T) characteristics of both saturated and π-conjugated molecules can be described quantitatively by a single equation with only two fit parameters. The derived parameters, in combination with a variation of the bulk conductivity of PEDOT:PSS, demonstrate that the absolute junction resistance is factorized with that of PEDOT:PSS.     

FAAS法测定卤化丁基橡胶塞中氧化镁含量不确定度的分析

按照JJF 1059-1999《测量不确定度评定与表示》技术规范与要求,分析了不确定度的各项来源,建立了FAAS法测定卤化丁基橡胶塞中氧化镁含量不确定度的评定方法,对不确定度的分量进行了分析评定。     

The Influence of Basic Volcanic Fluids on Gaseous Products of Source Rocks

The aspects, such as composition, temperature, viscosity, and fluidity, of basic volcanic fluids are greatly different from acidic volcanic fluids. In order to further complement the conceptual model of the influence of volcanic fluids on source rocks in petroliferous basins, this research uses the thermal simulation experiment to analyze the characteristics and reasons of the ratio of alkanes to acid, dry coefficient, and carbon isotope in the dry and fluid systems. The results show that, the ratio of alkanes to acid of all samples in the two systems will increase with the rise of temperature and presents features of the dry system higher than the fluid system, which indicates that the basic volcanic fluids restrain the generation of gaseous hydrocarbons. The dry coefficient of the fluid system at the range of 300–400°C is greater than that of the dry system, while smaller at the range of 400–450°C, which indicates that the basic volcanic fluids promote the generation of CH₄ in low temperature. In the two systems, δ¹³CO₂ of all samples have no obvious change as the rising of temperature, but in the fluid system the proportion of carbon isotopic will increase with the rising of temperature, which shows that carbonate exists in the volcanic fluids. The carbon isotopes of gaseous hydrocarbon in three samples are presented as δ¹³C₁ < δ¹³C₂ < δ¹³C₃, and it accords to general pyrolysis regularity without reversal phenomenon, which indicates alkane gases produced by pyrolysis of three samples are of organic origin.     

In Vitro Double Oxidation of n‐Heptane with Direct Cofactor Regeneration

A novel concept for the direct oxidation of cycloalkanes to the corresponding cyclic ketones in a one‐pot synthesis in water with molecular oxygen as sole oxidizing agent was reported recently. Based on this concept we have developed a new strategy for the double oxidation of n‐heptane to enable a biocatalytic resolution for the direct synthesis of heptanone and (R)‐heptanols in a one‐pot reaction. The bicatalytic cascade employs an NADH driven P450 BM3 monooxygenase variant (WT^NADH, 19A12^NADH or CM1^NADH) and an (S)‐enantioselective alcohol dehydrogenase (RE‐ADH). In the initial step n‐heptane is hydroxylated under consumption of NADH to produce (R/S)‐heptanol. In the second oxidation step the (S)‐heptanol enantiomers are transformed to the corresponding ketones, reducing and thereby regenerating the cofactor. Characterization of initial hydroxylation step revealed high turnover frequencies (TOF) of up to 600 min⁻¹, as well as high coupling efficiencies using NADH as cofactor (up to 44%). In the cascade reaction a nearly 2‐fold improved product formation was achieved, compared to the single hydroxylation reaction. The total product concentration reached 1.1 mM, corresponding to a total turnover number (TTN) of 2500. Implementation of an additional cofactor regeneration system (D ‐glucose/glucose dehydrogenase) enabled a further enhancement in product formation with a total product concentration of 1.8 mM and a TTN of 3500.     

卤代烷基铝的合成及机理

以铝和溴乙烷为原料制备溴代烷基铝,氯化铝和碘为引发剂,39℃下搅拌15rain引发。引发机理为：微量水存在时,氯化铝水解的酸性环境破坏铝表面氧化膜;同时,碘取代溴得到更活泼的卤代烃。反应机理为：铝向卤代烃提供单电子生成含铝的自由基,自由基结合生成卤代烷基铝。     

有机化合物热力学性质的预测（Ⅱ）——人工神经网络法预测烷烃的吉布斯自由能

采用分子子图编码法将烷烃的分子子图码作为人工神经网络的输入参数,对烷烃的吉布斯自由能进行预测.将预测值与文献值进行线性拟和,其回归系数达到0.9812.