Preparation and Characterization of High‐Temperature Non‐Flowing Diurea/Paraffin/Oil Composites as Form‐Stable Phase Change Materials

A series of form‐stable phase change materials (FSPCMs ) comprising paraffin as the latent heat storage material, diurea as the supporting material and base oil as the performance improvement agent were prepared. The diurea was synthesized in the system of paraffin/oil directly. A series of characterization was carried out for a deep understanding of shape stability and material properties of diurea‐FSPCMs . The results showed that paraffin and base oil were packaged in the three‐dimensional supra‐molecular structures network which was formed by diurea. The dropping point of the prepared FSPCMs could reach 256 °C and the oil separation rate was as low as 1.19% at 100 °C for 30 h. The results of thermal properties tests showed that the prepared FSPCMs exhibited excellent thermal stability and the FSPCMs remained solid‐like state in the temperature range from 25 to 200 °C. This study proposes a novel method to prepare high‐temperature non‐flowing FSPCMs composites and methods to detect the thermal stability and shape stability of FSPCMs , which is helpful in understanding the shape stability mechanism and broadening the potential application of FSPCMs .     

The wax deposition rate of water-in-crude oil emulsions based on the laboratory flow loop experiment

This paper aims to develop a mathematical model to predict the wax deposition rate of waxy crude emulsions, combining heat and mass transfer mechanisms. According to the flow loop experimental results, the wax deposition rate increases with the decreasing average temperature of oil/wall in a manner of linear regularity, and shows a downtrend with the increase of water cut due to diffusion resistance. An applicable model is developed regarding emulsion properties, radial temperature gradient, shear stress, and wax diffusion coefficient. In model validation, the prediction results are in good agreement with experimental data with the relative errors within 28.87%.     

Phenomenological study on heat and mass coupling mechanism of waxy crude oil pipeline transport process

Based on the phase equilibrium model of the paraffin wax precipitation in the process of oil pipeline transportation, theory and method of non-equilibrium thermodynamics were applied to obtain the linear phenomenological equations for the cross-interaction of heat and mass transfer during pipeline transport, which were derived from the irreversible entropy production rate equation. Then, the analysis of the irreversible heat flow and the mass flow were carried out, and the mathematical expressions of the phenomenological coefficient of liquid phase, the phenomenological coefficient of solid phase flow, and the heat flow phenomenological coefficient were obtained. Taking a waxy crude oil transportation pipeline in Daqing Oilfield as an example, based on the analysis of liquid–solid phase equilibrium, the irreversible linear phenomenological mechanism of heat and mass coupling in waxy crude oil pipeline transportation was analyzed in detail from three levels: phenomenological coefficients which reflect characteristic of the effect of force on flow in heat and mass transfer; thermodynamic forces which trigger heat and mass transfer; transmitted heat and mass flow density, providing a theoretical basis for the further study of the wax deposition in the process of pipeline transportation.     

Effect of the liquid–liquid phase separation on the crystallization behavior and mechanical properties of poly(ethylene‐ran‐vinyl acetate) and paraffin wax blend

The effect of liquid–liquid phase‐separation (LLPS) on the crystallization behavior and mechanical properties of poly(ethylene‐ran‐vinyl acetate) (EVA) with various amounts of vinyl acetate and paraffin wax blend was investigated. The blend of EVA‐H (9.5% vinyl acetate) and the wax became homogeneous at temperatures greater than its upper critical solution temperature (UCST) (98°C), and an LLPS was observed between UCST and the melting point of 88°C for EVA‐H in the blend. The existence of the LLPS is attributed to the relatively large amount of the hydrophilic component of vinyl acetate in EVA, although the molecular weight of the wax was just 560. However, LLPS did not occur for the EVA/wax blend when the content of vinyl acetate in EVA was less than 3%. This behavior was explained by using the Flory–Huggins lattice model with an effective interaction parameter. The degree of crystallinity of EVA‐H in the EVA‐H/wax blend, judged from a melting endothermic peak in differential scanning calorimeter (DSC) thermograms obtained during heating runs, decreased with increasing duration time in the LLPS region. The flexural modulus of the EVA/wax blend became maximum at certain blend composition (about 30 ∼ 40 wt % EVA depending upon the amount of vinyl acetate). This behavior can be explained by the fact that this blend composition has the largest relative degree of crystallinity of EVA measured by DSC and wide‐angle X‐ray scattering method. We found that the flexural modulus of the binder itself is directly related to that of a feedstock consisting of larger amounts of metal powder and the binder, which can help someone to develop a suitable binder system for a powder injection molding process. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1991–2005, 1999     

Thermal analysis of paraffins as model compounds for polyethylene

The n‐paraffins C₅₀H₁₀₂, C₄₄H₉₀, and C₂₆H₅₄ were analyzed with standard and temperature‐modulated differential scanning calorimetry. Crystallization and ordering from the melt to the condis phase showed practically no supercooling. These observations were confirmed with hot‐stage microscopy and a melting‐point apparatus. Only the organization of the C₂₆H₅₄ condis crystals to fully ordered crystals showed a supercooling of 4.0 K. The measurement of the apparent reversing heat capacity with a 0.05‐K modulation amplitude revealed that the melting of C₅₀H₁₀₂ was completed within 1.0 K and the isotropization of C₂₆H₅₄ was completed within less than 0.6 K, but 62–78% of the total transitions occurred over a much narrower temperature range of 0.1 K or less. The link to polyethylene was made with fractions of the masses 15,520, 2150, and 560 Da. The 560‐Da sample corresponded to C₄₀H₈₂ and showed also almost no supercooling, whereas the others, with folded and extended‐chain crystals, supercooled by about 10 K. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2810–2822, 2000     

在Raney Fe催化剂上F-T合成产物的分布和选择性

在浆态相Ｆ－Ｔ合成的连续搅拌釜反应器中,研究了ＲａｎｅｙＦｅ系列催化剂和其它工业铁基催化剂的性能。结果发现,ＲａｎｅｙＦｅ的前驱体对其性能影响很大。由Ａ１／Ｆｅ比为３的合金得到的ＲａｎｅｙＦｅ表现出了良好的活性稳定性,常规条件下ＣＯ的转化接近完全,其较大的中孔分布可能对初级产物的扩散限制较小,因而生成的２－烯烃和异构烃就少。也比较分析了催化剂固载量和粒度对ＲａｎｅｙＦｅ上的烷烃选择性的影响。此外,从产物分布的规律来看,在ＲａｎｃｙＦｅ催化剂上以生成高碳数烷烃和低碳数烯烃为主。     

片状纳米石墨的制备及其作为润滑油添加剂的摩擦磨损性能

采用搅拌球磨法制备了平均直径1 μm、厚度10～20 nm的片状纳米石墨;利用扫描电子显微镜、透射电子显微镜和X射线衍射仪分析了片状纳米石墨的微观形貌和组织结构;利用四球和销-盘式摩擦磨损试验机考察了片状纳米石墨作为液体石蜡添加剂的摩擦磨损性能.结果表明,片状纳米石墨能够显著提高润滑油的抗磨性能及承载能力,降低摩擦系数,其最佳添加量约为50 ppm.     

石蜡相光度法测定痕量钯

本文系统研究了钯（Ⅱ）与１－亚硝基－２－萘酚显色体系酚显本系在石蜡相中的显色反应。在ＰＨ＝０．０６～１１．０范围内,石蜡能定量吸附此显色络合物。采用等吸收点双波长光度法测定固相吸不镀差值,钯的含量在０～１．４ｍｇ／Ｌ范围内符合比一律,从而建立了钯的石蜡相光度分析法。方法应用于钯分子中痕量钯的测定,结果满意。     

单取代烷烃电离能的估算

根据量子力学微扰理论,将单官能团取代甲烷(MeZ)和单官能团取代烷烃(RZ)分别当作未微扰体系和同扰体系,则后者的第一电离能Ip~1~(~R~Z~)可由下式估算：Ip~1~(~R~Z~)＝Ip~1~(~M~e~Z~)＋7.1702△qz－1.3949△PEI。其中Ip~1~(~M~e~Z~)为取代甲烷的第一电离能,△qz为RZ和MeZ分子中Z上面的部分电荷之差,△PEI为基团R和Me的极化效应指数(PEI)之差。对10类单官能团取代烷烃的61个化合物计算结果表明,计算值和实验值之间的平均相对误差仅为0.20%。     

油酸/三乙醇胺/液体石蜡水体系层状润滑性能

采用^2HNMRT和IR,表征了油酸／三乙醇胺／液体石蜡／水体系层状液晶的结构,并以该体系为润滑剂,测定了其在铝合金表面的磨痕宽度和摩擦系数,同时与液体石蜡和商用润滑剂12－羟基硬脂酸锂进行了比较。结果表明,OLA／TEA／LP／H2O体系丑状液晶具有较好的极压性能,对于铝合金材料是一种较好的润滑剂。