Probing the interaction between asphaltene-wax and its effects on the crystallization behavior of waxes in heavy oil via molecular dynamics simulation

High content of asphaltenes and waxes leads to the high pour point and the poor flowability of heavy oil,which is adverse to its efficient development and its transportation in pipe.Understanding the interaction mechanism between asphaltene-wax is crucial to solve these problems,but it is still unclear.In this paper,molecular dynamics simulation was used to investigate the interaction between asphaltenewax and its effects on the crystallization behavior of waxes in heavy oil.Results show that molecules in pure wax are arranged in a paralleled geometry.But wax molecules in heavy oil,which are close to the surface of asphaltene aggregates,are bent and arranged irregularly.When the mass fraction of asphaltenes in asphaltene-wax system(ω_(asp))is 0-25 wt%,the attraction among wax molecules decreases and the bend degree of wax molecules increases with the increase ofω_(asp).Theω_(asp)increases from 0 to 25 wt%,and the attraction between asphaltene-wax is stronger than that among waxes.This causes that the wax precipitation point changes from 353 to 333 K.While theω_(asp)increases to 50 wt%,wax molecules are more dispersed owing to the steric hindrance of asphaltene aggregates,and the interaction among wax molecules transforms from attraction to repulsion.It causes that the ordered crystal structure of waxes can't be formed at normal temperature.Simultaneously,the asphaltene,with the higher molecular weight or the more hetero atoms,has more obvious inhibition to the formation of wax crystals.Besides,resins also have an obvious inhibition on the wax crystal due to the formation of asphalteneresin aggregates with a larger radius.Our results reveal the interaction mechanism between asphaltene-wax,and provide useful guidelines for the development of heavy oil.

Differences in leaf cuticular wax induced by whole-genome duplication in autotetraploid sour jujube

Drought-resistant plants exhibit strong water retention capability.In this regard,the autotetraploid sour jujube leaves exhibit better water retention than diploid leaves.Morphological comparisons and physiological comparisons of diploid and autotetraploid leaves showed that the autotetraploid leaves had thicker leaf cuticles and more leaf wax accumulation than the diploid leaves,which could reduce cuticle permeability and improve the drought tolerance of leaves.In this study,the cuticular wax crystalloids on the adaxial and abaxial sides of young and mature jujube leaves were observed in the two ploidy types,and unique cuticular wax crystalloids covering a large area of the cuticle on autotetraploid sour jujube leaves may provide an advantage in reducing leaf non-stomata transpiration and improving plant drought tolerance.Based on the transcriptome,115 differentially expressed genes between diploids and autotetraploids were further analyzed and found to be involved in the accumulation of cuticular wax components,including terpenoids,fatty acids,and lipids,as well as ABC transporter and wax biosynthetic process.Finally,14 genes differentially expressed between glossy autotetraploid leaves and nonglossy diploid leaves,such as LOC107414787,LOC107411574 and LOC107413721,were screened as candidate genes by qRT-PCR analysis.This findings provided insights into how polyploidization improved drought tolerance.

The effect of ethylene-vinyl acetate copolymer on the formation process of wax crystals and hydrates

Ethylene-vinyl acetate copolymer(EVA) as a kind of effective polymeric pour point depressant has been extensively used in the pipeline transportation of crude oil to inhibit wax deposition and improve the low temperature fluidity of crude oil. In this work, molecular dynamics simulations were performed to investigate the effect of EVA on wax-hydrate coexistence system to evaluate the application potentiality of EVA to the flow assurance of deep-sea oil-gas-water multiphase flow system. Our simulation results reveal that wax molecules gradually stretched and stacked from random coiling to a directional and ordered crystalline state during the process of wax solidification. The strong affinity of polar vinyl acetate side chains of EVA to neighboring water molecules made the EVA molecule prefer being in a curly state,which disrupted the ordered crystallization of surrounding wax molecules and delayed the solidification rate of wax cluster. In addition, it is found that EVA cocrystallized with wax molecules to form eutectic when the wax was fully solidified. The simulation results of hydrate nucleation and growth show that the EVA molecule displayed a two-sided effect on gas adsorption of wax crystals, which was the key factor that affected the nucleation and growth of hydrates in the methane-water system. The nonpolar hydrocarbon backbone of EVA increased the diffusion rate of methane and water, allowing more methane to diffuse to the surface of wax crystals, reducing the methane concentration in aqueous solutions and inhibiting the hydrate formation. On the other hand, the nonpolar vinyl acetate chains had a repulsive effect on methane, which reduced the adsorption area of methane on the eutectic surface and decreased the adsorption threshold value of the wax crystal. The excluded methane molecules would continue dissociating in the aqueous phase and participating in the nucleation and growth process of hydrates.Therefore, the probability of hydrate formation would be increased. It was worth noting that the inhibition performance of EVA on hydrate formation mainly played a significant role in the system with small wax crystal, while its hydrate promotion effect played a dominant role in the system with lager wax crystal. In summary, EVA could significantly inhibit both of the wax and hydrate deposition for the waxgas-water multiphase system with low wax content. When the wax content in the system was high, the role of EVA was mainly played in the alleviation of wax crystallization rather than the gas hydrates. The results of the present work can contribute to a better understanding of EVA on wax deposition and hydrate formation, and provide theoretical support of the potential industrial applications of EVA.

Experimental study on wax deposition of highly paraffinic oil in intermittent gas-oil flow in pipelines

Oil-gas two phase wax deposition is a fairly common and open-ended question in flow assurance of multiphase transportation pipelines.This paper investigated the two main aspects of oil-gas two phase wax deposition layer:apparent thickness and crystal structure characteristics.A typical highly paraffinic oil in Bohai Sea,China,was used as the experimental material to investigate the wax deposition thickness in oil-gas two phase under the influence of different oil temperatures,superficial gas/liquid phase velocities and gas-oil ratios by using multiphase flow loop experimental device.Just as in the classical theory of wax molecular diffusion,it showed that wax deposition thickness of oil-gas two phase increased with increasing oil temperature.Analysis of the impact of different superficial phase velocities found that the actual liquid flow heat transfer and shear stripping was the gas phase dominant mechanisms determining wax deposit thickness.In addition,the crystal structure of the wax deposition layer was characterized with the help of small-angle X-ray scattering(SAXS)for different circumferential positions,flow rates and gas-oil ratios.The bottom deposition layer had a complex crystal structure and high hardness,which were subject to change over flow rate variations.Furthermore,the SAXS results provided evidence that the indirect effect of the actual liquid velocity modified by the gas phase was the main mechanism.Our study of the effect of gas phase on the wax deposition of oil-gas two phase will help shed light onto the mechanism by which this important process occurs.Our findings address a very urgent need in the field of wax deposition of highly paraffinic oil to understand the flow security of oilgas two phase that occurs easily in multiphase field pipelines.

ZmCER1,a putative ECERIFERUM 1 protein in maize,functions in cuticular wax biosynthesis and bulliform cell development

The cuticular wax,acting as the ultimate defense barrier,is essential for the normal morphogenesis of plant organs.Despite this importance,the connection between wax composition and leaf development has not been thoroughly explored.In this study,we characterized a new maize mutant,ragged leaf4(rgd4),which exhibits crinkled and ragged leaves starting from the sixth leaf stage.The phenotype of rgd4 is conferred by ZmCER1,which encoding an aldehyde decarbonylase involved in wax biosynthesis.ZmCER1 function deficient mutant displayed reduced cuticular wax density and disordered bulliform cells(BCs),while ZmCER1 overexpressing plants exhibited the opposite effects,indicating that ZmCER1 regulates cuticular wax biosynthesis and BCs development.Additionally,as the density of cuticular wax increased,the water loss rate of detached leaf decreases,suggesting that ZmCER1 is positively correlated with plant drought tolerance.

Inhibition of wax crystallization and asphaltene agglomeration by core-shell polymer@SiO_(2) hybride nano-particles

The gelation of crude oil with high wax and asphaltene content at low temperatures often results in the block of transportation pipeline in Africa. In recent years, it was reported that surface hydrophobicmodified nanoparticles have important applications in crude oil flow modification. In this work, four kinds of core-shell hybride nanoparticles by grafting poly(octadecyl, docosyl acrylate) and poly(acrylate-α-olefin) onto the surface of nano-sized SiO_(2) were synthesized by grafting polymerization method.The chemical structure of nanoparticles was analyzed by Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM) and thermogravimetric analysis(TGA). The rheological behaviors of crude oil and precipitation of asphaltenes in the presence of nanoparticles were studied by measuring the viscose-temperature relationship curve, the cumulative wax precipitation amount, and morphology of waxes and asphaltenes. The results indicate that the docosyl polyacrylate@SiO_(2) nanoparticle(PDA@SiO_(2)) can reduce the cumulative wax precipitation amount of crude oil by 72.8%, decline the viscosity of crude oil by 85.6% at 20℃, reduce the average size of wax crystals by 89.7%, and inhibit the agglomeration of asphaltene by 74.8%. Therefore, the nanoparticles not only adjust the crystalline behaviors of waxes, but also inhibit the agglomeration of asphaltenes. Apparently, core-shell hybride nanoparticles provides more heterogeneous nucleation sites for the crystallization of wax molecules,thus inhibiting the formation of three-dimensional network structure. The core-shell polymer@SiO_(2) hybride nanoparticles are one of promising additives for inhibiting crystallization of waxes and agglomeration of asphaltenes in crude oil.

涂装高浸透WAX应用说明

主要介绍了高浸透WAX材料的特性,以及基于现有设备基础进行相关的设备改造及注意事项。

Prediction Model of Wax Deposition Rate in Waxy Crude Oil Pipelines by Elman Neural Network Based on Improved Reptile Search Algorithm

A hard problem that hinders the movement of waxy crude oil is wax deposition in oil pipelines.To ensure the safe operation of crude oil pipelines,an accurate model must be developed to predict the rate of wax deposition in crude oil pipelines.Aiming at the shortcomings of the ENN prediction model,which easily falls into the local minimum value and weak generalization ability in the implementation process,an optimized ENN prediction model based on the IRSA is proposed.The validity of the new model was confirmed by the accurate prediction of two sets of experimental data on wax deposition in crude oil pipelines.The two groups of crude oil wax deposition rate case prediction results showed that the average absolute percentage errors of IRSA-ENN prediction models is 0.5476% and 0.7831%,respectively.Additionally,it shows a higher prediction accuracy compared to the ENN prediction model.In fact,the new model established by using the IRSA to optimize ENN can optimize the initial weights and thresholds in the prediction process,which can overcome the shortcomings of the ENN prediction model,such as weak generalization ability and tendency to fall into the local minimum value,so that it has the advantages of strong implementation and high prediction accuracy.

成熟度和温度对芙蓉李贮藏期间生理生化特性及蜡质结构的影响

为研究成熟度和温度对芙蓉李贮藏期间生理生化特性和果皮蜡质结构的影响,本研究选择2个成熟度(F:约六成熟;S:约八成熟)的芙蓉李,于4、25℃条件下进行试验,分析16个生理生化指标的差异,采用正交偏最小二乘判别法(OPLS-DA)筛选不同成熟度芙蓉李在不同温度贮藏期间的主要差异性指标,检测芙蓉李贮藏前后蜡质结构的变化并分析其贮藏效应。结果表明,4℃条件下F与S之间的主要差异性指标为可溶性固形物含量(SS)、果肉硬度(FF)、果皮色度值a^(*)(PC-a^(*))、花色苷(AC)含量、可滴定酸(TA)含量、果皮硬度(PF),25℃时为SS、超氧化物歧化酶(SOD)活性、PC-a^(*)、果皮色度值b*(PC-b*)。不同成熟度果实的SS含量、PC-a^(*)、AC含量均随贮藏天数增加而逐渐上升(S贮藏28 d除外),同一贮藏天数下AC含量在25℃时显著高于4℃时,同一温度同一贮藏天数时S中的SS含量、PC-a^(*)显著高于F;PF、FF和TA含量随贮藏天数的延长而逐渐下降,4℃和F有利于FF和PF的保持,而25℃下TA含量下降更快;SOD活性随贮藏天数的延长先升高后下降,且在25℃和S中下降更显著。芙蓉李蜡质主要以直立片状晶体和颗粒状结晶的形式存在;两种晶体数量和形态的变化可能影响水分的流失,从而影响细胞壁结构的稳定性,进而影响贮藏性。本研究可为芙蓉李的采收和贮藏保鲜提供技术参考。

Steedman’s wax包埋切片DAPI染色法证实铝诱导花生根尖细胞程序性死亡

【目的】检验Steedman’swax包埋切片DAPI染色法是否适用于观察花生根尖细胞核形态。【方法】分别采取100μmol/L AlCl3处理不同时间(0、4、8、12 h)后两个花生品种(铝敏感型中花2号和耐铝型99-1507)的根尖,经过Steedman’s wax包埋切片等一系列过程,利用荧光染料DAPI染色观察细胞核形态变化。【结果】100μmol/L AlCl3可引起花生根尖细胞核形态发生改变,核质浓缩、核边缘化、呈新月状等,具有明显的PCD特征。花生根尖细胞在铝胁迫下发生PCD,PCD程度与花生耐铝性呈负相关,与处理时间呈正相关。【结论】Steedman’swax包埋切片DAPI染色法是一种快速、高效的适用于观察花生根尖细胞核形态的方法。

一种用于DAPI染色的方法——Steedman's wax包埋切片法

以植物的胚珠和子房为实验材料,介绍一种用Steedman swax包埋对组织切片中的细胞核进行DAPI染色的方法.Steedman swax作为一种低熔点多酯蜡,具有与石蜡相似的性质,切片方法同常规石蜡切片,适合于切成厚度大于5μm的连续切片.Steedman swax包埋的切片能成功地进行DAPI染色.与用压片法和Technovit7100或GMA包埋切片法进行的DAPI染色相比,用Steedman swax包埋切片法进行的DAPI染色具有廉价、操作简便、可进行连续切片、图象清晰等优点,特别在植物细胞程序化死亡 PCD 的研究中及细胞核DNA含量测定方面,有着较大的应用价值和潜能.

Determination of wax pattern die profile for investment casting of turbine blades

In order to conform to dimensional tolerances, an efficient numerical method, displacement iterative compensation method, based on finite element methodology （FEM） was presented for the wax pattern die profile design of turbine blades. Casting shrinkages at different positions of the blade which was considered nonlinear thermo-mechanical casting deformations were calculated. Based on the displacement iterative compensation method proposed, the optimized wax pattern die profile can be established. For a A356 alloy blade, substantial reduction in dimensional and shape tolerances was achieved with the developed die shape optimization system. Numerical simulation result obtained by the proposed method shows a good agreement with the result measured experimentally. After four times iterations, compared with the CAD model of turbine blade, the total form error decreases to 0.001 978 mm from the orevious 0.515 815 mm.

用对称透射二维WAXS强度研究PET取向非晶态结构

用对称透射法，测试聚酯（PET）取向非晶试样的二维广角X射线散射相干强度Ie（K，α），将不同方位角α上的Ie（K，α）非晶重叠峰曲线进行计算机分解，获得分子链间原子散射引起的二个峰为A（K＝0．126）、B（K＝0．169）；分子链内原子散射引起的五个峰分别为C（K＝0．304）、D（K＝0．553）、E（K＝0．374）、F（K＝0．465）、G（K＝0．606），K单位为nm－1．分析了它们的结构起源以及主要峰参数与α的关系，得到PET取向非晶态的细微结构信息．

双轴拉伸PET薄膜成膜过程非晶区分子取向的WAXS研究

本文将常应用于小的角度范围(29_(CuK_α)<50°)的结晶峰和非晶峰的计算机分峰法,推广到PET薄膜的广角度散射范围(2θ_(CuK_α)=5°—140°)。通过对分离出来的表征非晶区分子链间分布的非晶主峰特征参数的分析,探讨了在特定拉伸条件下非晶区分子取向在成膜过程的变化。

3个水稻WAX2同源基因表达的组织特异性及逆境响应特征

利用拟南芥的WAX2基因序列BLAST检索出3个水稻同源基因,命名为OsWAX2-1、OsWAX2-2和OsWAX2-3,与拟南芥WAX2基因的同源性分别为56.0%、55.2%和52.0%;其预测的编码蛋白与WAX2蛋白的同源性分别为61.5%、60.5%和64.7%。这3个蛋白都分别存在4个跨膜结构区和1个甾醇去饱和酶的保守区,说明它们都属于跨膜蛋白并可能与角质层的蜡质合成有关。采用半定量RT-PCR方法检测3个OsWAX2基因在水稻不同部位的表达情况,及高温、低温、NaCl、PEG和ABA5种处理对3个OsWAX2基因在转录水平表达的影响。结果表明,3个OsWAX2基因在水稻中的表达存在时空差异,3个基因在水稻萌动的胚中表达量都很高,OsWAX2-3基因在叶中的表达量最高;3个OsWAX2基因对高温、低温、盐、干旱及ABA胁迫响应也存在差别,OsWAX2-1只在ABA处理时增强表达;OsWAX2-2受高温、低温、盐、干旱胁迫及ABA诱导并且响应迅速。这一结果为进一步研究OsWAX2基因在水稻生长发育过程及逆境胁迫下的功能与作用机制提供了参考。

Properties of Compound Systems of Paraffin Wax Emulsion and Copper Azole and Treated Wood

[Objective]Preservation and waterproof treatment are two crucial parts in wood protection, which can not only extend the service time, but also expand the application range of wood products. [Method] This work combined CA with paraffin wax emulsion to treat wood samples, and basic properties of the compound system, such as stability （storage stability and centrifugal stability）, particle size and pH val-ue, and water repel ency （water absorption, shrinkage and swel ing） of treated sam-ples were investigated. [Result and Conclusion] 1） the compound systems of CA and paraffin latex had a favorable miscibility and stability; 2） compared with untreated wood, CA-treated samples showed poor water repel ing properties, whereas samples treated with the compound systems indicated an obvious reduction in water absorp-tion, and the shrinkage and swel ing of them were improved as wel .

甘蓝型油菜BnaSLY1基因进化分析及功能研究

赤霉素调控植物表皮细胞增长、茎叶伸长以及株型建成。拟南芥SLY1属于F-box蛋白,它通过靶向泛素化赤霉素信号转导路径的负向调控因子——DELLA蛋白来影响植物生长发育,然而油菜中BnaSLY1的基因功能尚未揭示。本研究对BnaSLY1进行了表达特征和进化树分析,利用CRISPR/Cas9技术创制了BnaSLY1不同拷贝数的突变体,结合RNA-Seq技术对BnaSLY1的生物学功能及其对油菜生长发育的影响进行了研究。结果表明,甘蓝型油菜Westar中有2个SLY1同源拷贝BnaA01.SLY1和BnaA06.SLY1,它们表达模式基本相同,为组成型表达基因,其蛋白定位在细胞核,且在不同的油菜品种及十字花科植物间序列保守。与对照相比,单突bnaa01sly1和bnaa06sly1开花时间推迟,株高显著降低,而双突bnasly1还表现出深绿色光叶表型,叶片厚度增加,开花期比单突进一步推迟,株高也进一步降低。RNA-Seq结果显示,双突与Westar之间的差异表达基因显著富集在生长素信号转导路径以及蜡质合成通路,多个开花时间相关基因表达也发生显著变化。本研究表明, BnaSLY1除影响植物株高和开花时间等生长发育进程,还影响表皮蜡质合成,为探索赤霉素信号转导路径在甘蓝型油菜生长发育中的重要作用奠定了理论基础。

亲水性石墨烯@TiO_(2)@石蜡光热相变微胶囊的制备及性能

【目的】解决光热相变材料(phase change materials,PCMs)在实际光热储存领域中存在易泄漏、导热以及光热转换效率低的问题。【方法】采用微胶囊法,氧化石墨液相剥离可膨石墨制备亲水性石墨烯;亲水性石墨烯与无机材料TiO_(2)复合作为壳层,以石蜡为核,制备复合相变微胶囊,系统研究微胶囊性能。【结果】亲水性石墨烯添加量(质量分数)为1%时,制备的微胶囊为形状规则的球形结构,泄漏率为6.90%,热导率为0.459 W(/m·K),熔融焓为84.58 J/g,结晶焓为91.26 J/g,微胶囊化效率为63.33%;在模拟光照10 min后,微胶囊的温度最高达到64.8℃,相比纯石蜡提升31.4℃。【结论】亲水性石墨烯的加入对复合PCMs的光热转换效率有显著提升,具有良好的光热转换及储存性能。

橡胶树GT1和RRIM600的叶片结构及与白粉病抗性的相关性

橡胶树RRIM600和GT1品种是天然橡胶产业两个重要的橡胶品种,GT1品种抗寒、抗病,RRIM600为高产品种,但抗旱性和抗病性较差。为弄清这两个橡胶品种的叶片结构及其与白粉病抗性的相关性,采用石蜡切片法和显微观察方法,对RRIM600和GT1叶片进行解剖结构特征观察。结果表明:GT1的蜡质含量高于RRIM600,橡胶树的蜡质层形成一个屏障阻碍病原菌的入侵;两个品种的气孔数量、面积、密度等差异不明显,说明GT1和RRIM600的气孔与抗病性无相关性;橡胶树叶片厚、叶肉厚、结构疏松度大、海绵组织厚和上表皮薄可能更有利于白粉病菌侵染。蜡质含量与橡胶树白粉病抗性存在一定的相关性,而叶片的组织结构、气孔结构等特征对白粉病抗性的影响较小。

食用蜡基稻米油油凝胶的制备及其性能特性研究

以稻米油为油相,蜂蜡、米糠蜡、巴西棕榈蜡和小烛树蜡作为凝胶剂制备油凝胶,并对其持油率、硬度、流变特性和微观结构进行表征。结果表明:蜂蜡、米糠蜡、巴西棕榈蜡的临界添加量为4%(以凝胶剂和稻米油的总质量为基准,下同),小烛树蜡则为2%,其中蜂蜡的持油效果最佳;随着凝胶剂添加量的增加,油凝胶硬度和黏附性总体上增强。流变学分析显示,所有油凝胶呈现剪切变稀的假塑性行为,弹性模量(G′)大于黏性模量(G″),表明以弹性形变为主。微观结构揭示,不同蜡凝胶剂在6%添加量下形成的油凝胶中存在α、β'和β型晶体。红外光谱分析证实了凝胶剂与稻米油间的非共价相互作用。差示扫描量热分析表明,巴西棕榈蜡油凝胶具有最高的熔化峰值温度。