Ni catalyst promotion of a Cis-selective Pd catalyst for canola oil hydrogenation

A Ni catalyst was added to a cis-selective Pd catalyst in an attempt to further improve the Pd catalyst's cis-selectivity and activity for canola oil hydrogenation. The system was tested under reaction conditions known to be suitable for cis-selective hydrogenation with the Pd catalyst (50 ppm Pd, 70 °C, and 5.2 MPa). Although inactive on its own under these conditions, the addition of 100 ppm Ni increased the hydrogenation activity (from 2.12 to 2.49 10⁻² min⁻¹). Further addition of Ni up to 1000 ppm resulted in no further improvements in activity. The trans isomer contents of the oils hydrogenated with Pd and the Pd/Ni systems were similar. The level of conjugated dienes decreased rapidly during hydrogenation with both Pd alone and with the Pd/Ni combination and no changes in conjugation were detected in the presence of the Ni catalyst alone. The increased activity of the Pd/Ni system over Pd alone was attributed to adsorption of catalyst poisons from the oil by Ni.     

Heat Transfer Analysis for Gas-to-Liquids Transportation Through Trans Alaska Pipeline

Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this article, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations.     

Relationship between oxidative stability of vitamin E and production of fatty acids in oils during microwave heating

Effects of microwave heating on the oxidative stability ofd-tocopherols were studied in relation to the production of fatty acids in oils. During microwave heating, the stability of tocopherols decreased in the orderδ>β>γ>α. This order did not depend on the types of ethyl esters of fatty acids or oils present. But, the shorter the chainlength and the lower the degree of unsaturation of the fatty acid ethyl esters, the greater was the reduction in amount of individual tocopherols. A similar tendency was observed when tocopherol-stripped vegetable oils, with equimolar mixtures of tocopherols added, were treated under the same conditions. The reduction in tocopherols became greater with increasing levels of free fatty acids.     

The composition of hydrogenated fats by high-resolution13C nuclear magnetic resonance spectroscopy

The high-resolution¹³C nuclear magnetic resonance spectra of twelve hydrogenated fats have been examined. Each spectrum contains 50–100 signals and reveals much about the nature of the acyl chains of both double-bond position and configuration. The signals for the ω1, ω2 and ω3 carbon atoms give information on thecis andtrans isomers of the Δ15, Δ14, Δ13 and Δ12 18:1 esters, respectively. Allylic signals distinguish betweencis andtrans esters, and the proportion of totalcis to totaltrans isomers can be obtained from these. Olefinic signals are the most informative, and most of these have been assigned. This leads to a semi-quantitative estimate of the various 18:1 isomers present. Assignments are based mainly on information already in the literature, but some were confirmed after urea fractionation of the acids from a hydrogenated oil in whichcis andtrans monoene acids were separately concentrated.     

N-乙基-N-苄基间磺酸苯胺中异构体的分离研究

对N-乙基-N-苄基间磺酸苯胺中间位、对位及邻位异构体进行了分离研究，用苯甲醛邻磺酸与N-乙基-N-苄基闯磺酸苯胺混合物缩合，制成衍生物，再用HPLC(色谱柱：CLC-ODS，检测波长：254nm，流动相：甲醇／四丁基溴化铵=60％／40％)分离，可使异构体得到有效分离，并能判断N-乙基-N-苄基间磺酸苯胺商品中间位物主含量的高低。     

二硝基芘异构体在模拟大气条件下的光化学反应

本文研究了二硝基芘异构体在模拟大气条件下的光化学反应，结果表明反应速率呈二级动力学关系，除光源变化的影响外，二硝基芘异构体在不同气氛中，反应速率不同，存在着氧的猝灭和氧化作用，而不同的异构体之间，相应的反应速度也不同。光解产物中存在硝基羟基类化合物、醌类和二聚体。毒理实验表明，光解产物致突变性下降。     

化学计量学-荧光分析法同时测定甲酚的3种同分异构体

利用化学计量学中的主成分回归法(PCR)和荧光分析法相结合,并用遗传算法(GA)对其进行优化,建立了同时测定甲酚混合物中3种同分异构体的新方法。在p H 4.92的磷酸氢二钠-磷酸二氢钾缓冲介质中,邻、间、对甲酚浓度在3.00~12.0μg/m L范围内,以λ=274 nm为定激发波长,测定300~335 nm波长范围内的荧光光谱,分别使用PCR和GA-PCR两种校正模型对光谱数据进行解析,并同时对3种异构体进行定量分析。研究结果表明,两种方法对邻、间、对甲酚进行预测的平均回收率分别为89.0%、107.5%、100.4%和100.6%、99.1%、98.0%,均方根预测误差分别为0.71、0.49、0.15μg/m L和0.17、0.16、0.21μg/m L,精密度试验的相对标准偏差均小于1.0%,且经GA优化后的PCR方法的加标回收率得到了明显改善,均方根预测误差减小50%,具有更好的准确度。     

Oral and intestinal digestion of oligosaccharides as potential sweeteners: A systematic evaluation

The utilisation of oligosaccharides by oral microorganisms and intestinal enzymes are important factors in determining their effectiveness as alternative sweeteners. In this study, classes of naturally occurring sugars were assessed using in vitro models for oral and intestinal digestibility, in order to test the influence of chemical structure on functional properties. Amongst the classes of sucrose isomers, α-glucobioses, β-glucobioses and sucrose-based oligosaccharides, structures were identified that were not utilised by the common oral bacterium Streptococcus mutans, and would therefore contribute to the non-cariogenic potential of a sweetener. Analysis of the rate and products of digestion by a rat glucosidase mixture was used to determine the relative intestinal digestibility. The results showed that oligosaccharides containing a (1 → 6)-β-Glc group, including gentiobiose and gentiobiitol, together with melezitose, a sucrose-derived oligosaccharide containing a α-Glc-(1 → 3)-Fru moiety were resistant to digestion by both S. mutans and mammalian intestinal enzymes, highlighting their potential as dietary sugar substitutes.     

三氧化二铝PLOT柱气相色谱法分离氢同位素自旋异构体

氢同位素核自旋异构体正-仲态比例影响氢同位素的低温物性,有必要对其比例进行测定。本文利用活性三氧化二铝多孔层开管(Porous Layer Open Tubular,PLOT)柱实现了正-仲氢同位素(氕、氘)的基线分离,发展了一种可在液氮温度下测定同核分子正-仲态比例的色谱分析技术。研究结果表明,与传统三氧化二铝填充柱相比,高效PLOT柱实现了正、仲氕(o-H_2、p-H_2)以及正、仲氘(o-D2、p-D2)的基线分离(分离度R_s大于1.5),当流量为5 m L·min-1时,分离度R_s(p-H_2,o-H_2)=6.9,R_s(o-D2,p-D2)=1.8。正仲态分离度与进样量、流量均有关系。根据峰面积的积分结果,常温(298 K)下正、仲氕比例为2.77:1,正、仲氘比例为1.78:1,与理论测算值基本符合。HD与o-H_2实现了部分分离,R_s(o-H_2,HD)=0.5,根据理论预测,实现HD与o-H_2的基线分离(R_s达到1.5),理论塔板数需要达到3.9×105。