蜡晶改进剂对润滑油馏分中蜡组分结晶控制作用的研究

针对中国石油抚顺石化公司石油一厂润滑油过滤速度差异大的问题,研究了润滑油各侧线所含不同蜡组分对应的晶型特点和蜡晶改进剂的作用机理,提出了蜡晶改进剂的选用原则。     

Influence of viscosity on wax settling and refining loss in rice bran oil

The role of viscosity on was settling and refining loss in rice bran oil (RBO) has been studied with model systems of refined peanut oil and RBO of different free fatty acids contents. Wax was the only constituent of RBO that significantly increased the viscosity (81.5%) of oil. Monoglycerides synergistically raised the viscosity of the oil (by 114.2%) and lowered the rate of wax settling. Although a reduction in the viscosity of the oil significantly decreased the refining loss, the minimum loss attained was still 20% more than the theoretically predicted value. This led us to conclude that some chemical constituents, such as monoglycerides, must be removed before dewaxing; thereafter, oryzanol and phospholipids have to be removed. One can get an oil free of wax, recover other by-products and reduce processing losses.     

Isolation and identification of the causative factors responsible for color fixation in rice bran oil

To understand the chemical nature of the dark coloring constituents responsible for color fixation in rice bran oil, crude and dewaxed rice bran oils of 6.8% free fatty acids were fractionated on a silica gel column to get a dark-colored material (0.57% of the oil). Thin-layer chromatographic analysis of the material showed a spot corresponding to monoglycerides, but there were no spots corresponding to other glycerides. It contained traces of phosphorus (<0.1 ppm, which is equivalent to 2.5 ppm phospholipids) and iron (1.3 ppm) that could not be attributed to phospholipids or to any iron-complex. Upon saponification it yielded 12% nonsaponifiable matter. Gas-liquid chromatographic analysis of the saponifiable matter (after acidification and methylation of fatty acids) showed the presence of palamitic, oleic and linoleic acids. Further, on the basis of comparison with spectroscopic data of synthetic monoglyceride, the constituent was characterized to be a mixture of monoglycerides with side chains of oxidized unsaturated fatty acids.     

多功能乳化蜡产品的制备和应用

报告了利用石蜡、地蜡、蜂蜡及复合乳化剂制备乳化蜡的方法。乳化条件为乳化温度 80℃ ,乳化时间40 min,搅拌速度不低于 80 0 r/m in,乳化剂用量 10 %～ 15 % ,蜡含量 15 %～ 2 0 %。制成的乳化蜡产品呈半透明白色乳液 ,略带兰光、中性、放置 30 d稳定性良好。该乳化蜡可用于皮革顶层涂饰 ,汽车、家具、地板等上光剂配方中 ,效果良好。     

Effect of dewaxing pretreatment on composition and stability of rice bran oil: Potential antioxidant activity of wax fraction

The effect of dewaxing pretreatment on rice bran oil composition and stability was investigated, as well as the possibility to use rice bran oil waxes as natural antioxidants at high temperatures. A correlation between wax content and dewaxing time was noticed. The pre‐dewaxing process led to a loss of minor compounds, which negatively affected the oxidative stability index (OSI) of the dewaxed oil. The addition of rice bran oil waxes improved the oil stability index and heat stability of sunflower oil. An increase of 60% of the OSI and a significant decrease in polymer formation (59.2%) were observed.     

Effect of refining of crude rice bran oil on the retention of oryzanol in the refined oil

The effect of different processing steps of refining on retention or the availability of oryzanol in refined oil and the oryzanol composition of Indian paddy cultivars and commercial products of the rice bran oil (RBO) industry were investigated. Degumming and dewaxing of crude RBO removed only 1.1 and 5.9% of oryzanol while the alkali treatment removed 93.0 to 94.6% of oryzanol from the original crude oil. Irrespective of the strength of alkali (12 to 20° Be studied), retention of oryzanol in the refined RBO was only 5.4–17.2% for crude oil, 5.9–15.0% for degummed oil, and 7.0 to 9.7% for degummed and dewaxed oil. The oryzanol content of oil extracted from the bran of 18 Indian paddy cultivars ranged from 1.63 to 2.72%, which is the first report of its kind in the literature on oryzanol content. The oryzanol content ranged from 1.1 to 1.74% for physically refined RBO while for alkali-refined oil it was 0.19–0.20%. The oil subjected to physical refining (commercial sample) retained the original amount of oryzanol after refining (1.60 and 1.74%), whereas the chemically refined oil showed a considerably lower amount (0.19%). Thus, the oryzanol, which is lost during the chemical refining process, has been carried into the soapstock. The content of oryzanol of the commercial RBO, soapstock, acid oil, and deodorizer distillate were in the range: 1.7–2.1, 6.3–6.9, 3.3–7.4, and 0.79%, respectively. These results showed that the processing steps—viz., degumming (1.1%), dewaxing (5.9%), physical refining (0%), bleaching and deodorization of the oil—did not affect the content of oryzanol appreciably, while 83–95% of it was lost during alkali refining. The oryzanol composition of crude oil and soapstock as determined by high-performance liquid chromatography indicated 24-methylene cycloartanyl ferulate (30–38%) and campesteryl ferulate (24.4–26.9%) as the major ferulates. The results presented here are probably the first systematic report on oryzanol availability in differently processed RBO, soapstocks, acid oils, and for oils of Indian paddy cultivars.     

Purification and identification of rice bran oil fatty acid steryl and wax esters

Fatty acid steryl esters (FASE) and wax esters (WE) of rice bran oil (RBO) have potential applications in cosmetic, nutraceutical, and pharmaceutical formulations. FASE and WE were extracted from RBO by a modified Soxhlet extraction using hexane as the solvent. FASE and WE were then separated by storage in acetone at 10°C for 24 h. The FASE fraction was further purified by silica, gel column chromatography. The contents and compositions of FASE and WE, as well as their saponified products, were identified by GC and GC-MS. The identification of FASE and WE was carried out by comparing the retention time of GC peaks and mass spectral analysis with standards synthesized in our laboratory. FASE and WE accounted for ca. 4.0% of crude RBO, of which 2.8–3.2% and 1.2–1.4% are FASE and WE, respectively. GC-MS of FASE showed five major peaks. Major FA in the FASE fraction were linoleic acid and oleic acid, which were esterified with 4-desmethyl, 4-monomethyl, and 4,4-dimethyl sterols. The contents of 4-desmethylsterol, 4-monomethylsterol, and 4,4-dimethylsterol esters in crude RBO were 76.1, 8.7, and 15.1%, respectively. WE of RBO consisted of both even and odd carbon numbers ranging from C₄₄ to C₆₄. The major constituents were, saturated esters of C₂₂ and C₂₄ FA and C₂₄ to C₄₀ aliphatic alcohols, with C₂₄ and C₃₀ being the predominant FA and fatty alcohol, respectively. The advantages of using a modified Soxhlet extraction over column chromatography are less solvent usage and larger sample size per batch with shorter operation time.     

A process for the preparation of food-grade rice bran wax and the determination of its composition

A two-step method was developed for the preparation of food-grade wax. The first step involved the solventdefatting of crude wax, which gave a dark brown, dry, powdered wax with a m.p. of 75–79°C. The major impurity in the defatted wax was the dark brown resinous matter. In the second step, the resinous matter was removed by bleaching with sodium borohydride in isopropanol. This step yielded a pale yellow, odorless wax with purity higher than 99% and with a m.p. of 80–83°C. The resinous matter was a mixture of aliphatic aldehydes, fatty alcohols, and FA. High-temperature GC analysis of the purified rice bran wax indicated that it contained 11 major and 9 minor types of saturated wax esters. The major and minor peaks contained C₄₄–C₆₄ and C₄₅–C₅₉ wax esters, respectively. Rice bran wax was mainly a mixture of saturated esters of C₂₂ and C₂₄ FA and C₂₄ to C₄₀ aliphatic alcohols, with C₂₄ and C₃₀ being the predominant FA and fatty alcohol, respectively. The alcohol portion of the wax esters also contained small amounts of branched and odd carbon number fatty alcohols.     

流化床中硝酸钙晶体生长的实验研究

流态化结晶分离硝酸钙是改进硝酸磷肥工艺的关键技术。实验获得了流化床循环流动条件下的Ca(NO3)2-H2O二元体系溶液在6.5～24.5℃的第1过饱和曲线,其对应的拟介稳相区过饱和度Δw(Ca(NO3)2)=4.2%～4.5%。该条件下四水硝酸钙晶体在流化床中均匀生长,平均线性生长速率可达u=0.06mm/min。     

Young压力对晶核形成和晶体生长的影响

本文以Young压力和构晶时的水体扩散为基础讨论了晶核形成和晶体生长的微观机理。     

氯化钾间歇冷却结晶生长规律及粒度控制实验研究

采用聚焦光束反射测量技术（FBRM）考察了氯化钾（KCl）间歇冷却结晶过程中晶体成核和生长规律,重点研究了降温速率对KCl水溶液冷却时产生过饱和度的影响,以及添加晶种的相关条件（如晶种粒径和添加量等因素）与KCl晶体产品粒度的关系。同时,采用直接冷却刺激起晶产生“晶种”,并控制其生长达到控制晶体产品粒度的目的。结果表明,在添加晶种条件下,程序降温过程产生的低过饱和度不易引起爆发成核,且晶种的添加量决定着晶体产品的平均粒度与理想生长模型的偏差。另外,降温速率是冷却刺激起晶产生“晶种”粒径的关键因素。     

Study on wax precipitation characteristics of wax deposit in pipes

Wax deposit properties are a significant concern in pipeline pigging during waxy crude oil transportation. In the present work, the impacts of flow conditions and oil properties on the wax precipitation characteristics of wax deposits are investigated. A flow loop apparatus was developed to conduct wax deposition experiments using four crude oils collected from different field pipes. The differential scanning calorimetry (DSC) technique was employed to observe the wax precipitation characteristics of crude oil and wax deposit. The results show that the wax content and the wax appearance temperature (WAT) of the deposits increase with shear stress and radial temperature gradient, and decrease with radial wax molecule concentration gradient near the pipe wall. The DSC tests on the wax deposits revealed that the deposit wax content is strongly correlated to the oil wax content. Furthermore, an empirical correlation was developed to predict the wax content and the WAT of the wax deposit. Verification of the empirical correlation using the different oils indicated that the average relative error of the wax content prediction and average absolute error of WAT prediction were 13.2% and 3.6°C, respectively.     

Solution of the growth equation for asymmetric crystal faces

Most melt-grown and many solution-grown lamellar polymer crystals have curved lateral faces. Mathematical treatments by Mansfield, Point and Villers, and Toda, have provided a satisfactory interpretation of the shape of such crystal faces in terms of nucleation and relatively slow propagation rates of layers of attaching stems. The treatments by these authors, which start with the Frank-Seto growth model, assume that the propagation rates of growth steps to the right (v_r) and to the left of the secondary nucleus (v_l) are equal. However, for many crystal growth faces this is not the case; faces which lack a mirror plane perpendicular to the lamella have v_r≠v_l, resulting in asymmetric curvature. Here, we set up and solve the differential equations and reconstruct the shape of the growth front for the case of asymmetric spreading of steps. The solution is presented for the simple square lattice model. The asymmetric growth front is still described as part of an ellipse, as in the symmetric case, except that the centre of the ellipse is translated parallel to the underlying crystallographic plane in the direction of fast v. In forthcoming publications we will adapt the solution to other 2D Bravais lattices, appropriate to the crystal structures of specific polymers. Thus we will analyze complete habits of polymers such as polyethylene, poly(ethylene oxide), and poly(vinylidene fluoride), whose {110}, {120} and {110} growth faces, respectively, are asymmetric. The results of the present work allow a detail kinetic analysis of any well-developed polymer growth face in terms of the step initiation rate i and the propagation rates v_r and v_l. The present work also quantifies explicitly the deviations from elliptic shape and the substrate edge effects, and discusses when these can be ignored.     

Evaluation of phosphoglycolipid elimination from rice bran oil by a nonporous membrane using NMR spectroscopy

The presence of phosphoglycolipids (PGL) in degummed rice bran oil (RBO) affects the color in the subsequent refining process, posing problems in producing a final product of acceptable quality. A nonporous membrane could achieve near complete removal of phospholipids even under hexane‐diluted conditions, including PGL present in RBO. PGL from glycolipid fractions isolated from various membrane process stream samples, analyzed by ¹H, ¹³C and ³¹P NMR spectroscopic techniques, indicated the absence of PGL in the permeate, besides identifying them to be oleates/linoleates of phosphatidic acid. Hence, the efficacy of a nonporous membrane in the removal of PGL suggests its application for effective degumming of crude RBO.     

Methane hydrate crystal growth on shell substrate

Hydrate crystals growth on the surface of methane bubble (hydrate film) in pure water was studied by using a high-pressure visible microscope under the conditions of subcooling ΔT = 5.44–13.72 K and methane concentration difference ΔC = 2.92–8.19 mol·L^-1. It was found the hydrate film is porous and the hydrate crystals grow towards the liquid phase on the film substrate. The crystal morphology and growth rate are affected by ΔT and ΔC. When ΔT < 8.82 K and ΔC < 4.12 mol·L^-1, the hydrate grows into scattered columnar crystals, and the axial growth rate of the crystal gradually decreases. When ΔT > 8.82 K or ΔC > 4.12 mol·L^-1, the hydrate crystals grow in dendritic shape, and the axial growth rate increases first and then decreases. The perimeter and area of the growing hydrate crystals were measured, and the fractal dimension of hydrate crystal under different ΔC and ΔT was calculated. The results show that the fractal dimension of columnar hydrate crystal is greater than 3. When 3.87 mol·L^-1 < ΔC < 4.20 mol·L^-1 and 7.4 K < ΔT < 8.8 K, the fractal dimension of columnar hydrate crystal is greater than 4; The fractal dimension of dendritic hydrate crystal is less than 3. When ΔC > 4.77 mol·L^-1, ΔT < 8.52 K, the fractal dimension of dendritic hydrate crystal is less than 2.     

Anisotropic growth kinetics and electric properties of PZT-5H single crystal by solid-state crystal growth method

The PZT-5H single crystal growth on [111]c-, [110]c-, and [001]c-oriented seed crystal by solid-state crystal growth (SSCG) method was investigated. The growth rate of PZT-5H single crystal strongly depends on seed crystal orientation and annealing time. The mean growth distance is 682, 620, and 93 μm for [111]c-, [110]c-, and [001]c-oriented PZT-5H single crystal grown at 1150°C for 8 h, respectively. The growth kinetics of SSCG-grown PZT-5H single crystal was discussed. It is found that the growth of single crystal is driven by the solubility difference between the matrix grains and single crystal growth front interface, arising from the local curvature and the crystallographic directions dependent solubility. The growth of [001]c-oriented PZT-5H single crystal was mainly contributed from the difference solubility arising from the local curvature of growth front interface, while the growth of [111]c- and [110]c-oriented PZT-5H single crystal was mainly contributed from the difference solubility between {111} and {110} plane of single crystal and matrix grains. The piezoelectric coefficient d₃₃ of up to 1028pC/N (about 50% larger than that of the same component ceramic) was obtained in a [110]c-oriented PZT-5H single crystal with a Curie temperature of about 230°C. The large field piezoelectric constants d₃₃* of up to 1160 pm/V (about 50% larger than that of the same component ceramic) at 15 kV/cm was also obtained in [110]c-oriented PZT-5H single crystal with a large strain of 0.18%. This work deepens our understanding on the growth kinetics of SSCG and pushes the way of growth of soft PZT single crystal by SSCG.     

Hydrothermal synthesis of gallosilicate (MFI) zeolite: Factors influencing crystallization kinetics and crystal size/growth

The kinetics of the hydrothermal synthesis of gallosilicate (MFI) zeolite (under autogeneous pressure at 180°C) from a gel containing a source of silica (Na-trisilicate or fumed silica), gallium nitrate, templating agent (TPA-Br or TPA-OH), deionized water and sulfuric acid have been thoroughly investigated in order to understand the influence of various synthesis parameters (viz. gel composition, source of silica, template, method of gel preparation and pH of gel) on the crystallization kinetics and crystal size/growth of the zeolite. The zeolite samples were characterized for their crystallinity by XRD and crystal size and morphology by SEM. The crystallization rate and crystal size of the zeolite were found to be strongly influenced by the above synthesis parameters. © 1998 SCI     

Investigation of thickness and wax content of wax deposits in polyethylene pipe using a flow loop

In this study, the thickness and wax content of wax deposits were found to be thinner and lower in the polyethylene (PE) pipe than in the stainless steel (SS) pipe using a flow loop apparatus. The diffusivity of wax, radial thermal gradient, and wax precipitation rate in the PE and SS pipes were calculated and compared. It was found the diffusivity of wax in the PE pipe was higher and tended to enhance the wax deposition in the PE pipe, while the radial thermal gradient and wax precipitation rate were lower in the PE pipe and had the opposite effects. These factors are shown to be comparable with each other and the effect of the thermal gradient dominates the mass flux of wax from bulk to the oil-deposit interface and into the deposits finally, thus causing differences in thickness and wax content of deposits between the PE and SS pipes.     

硫酸锶晶体生长动力学研究

为了从控制晶体生长角度，说明制备纳米硫酸锶沉淀体系中存在的EDTA对产品粒径的影响作用，根据过程机理，用恒组成法研究硫酸锶晶体生长动力学。根据叠加模型和弱化模型，建立体系中有EDTA存在时，硫酸锶沉淀过程的晶体生长动力学模型。结果表明，硫酸锶沉淀过程中晶体生长属于表面反应控制机理。EDTA存在能降低晶体生长速率，有利于减小粉体粒径。     

Polymorphism of D-mannitol: Crystal structure and the crystal growth mechanism

The polymorphism of D-Mannitol(mannitol) is reviewed in this paper. It was found that the structure of the stable form is consistent in most literatures, but different authors have given different information about the two metastable forms. Therefore the commonly used nomenclature of mannitol was summarized based on the crystal unit cell parameters with the help of X-ray powder diffraction. Moreover, the crystal growth mechanism of mannitol polymorphs was summarized. Considering the lack of kinetic data for the metastable form especially, a reported method was attempted to apply to δ mannitol in an aqueous cooling crystallization process based on the induction time previously measured, and it was identified that the growth of the δ form follows the two-dimensional(2D) nucleationmediated mechanism. The results also indicate that the method based on induction time and supersaturation should have the potential to be expanded to the metastable polymorphs for the growth property study in a bulk system.