大理地区烤烟陈化过程中有机酸含量变化研究

使用衍生化-气质联用方法研究了大理地区烤烟连续陈化4年其有机酸变化。结果表明,烤烟在陈化过程中,①非挥发酸在6到18个月内含量明显降低,18到30个月内变化减缓,30到48个月内下降又加快,非挥发酸总量与苹果酸含量线性相关;②半挥发酸随陈化时间延长呈缓慢下降趋势;③挥发酸总量在6到24个月的陈化时间内明显增加,24到36个月内保持不变并略有下降,36到48个月内基本呈下降趋势,挥发酸总量与异戊酸含量线性相关。     

烟草中挥发性与半挥发性有机酸的GC-MS法快速检测

建立了气相色谱-质谱联用同时测定烟草中25种挥发性与半挥发性有机酸的快速定量分析方法。样品经二氯甲烷震荡萃取,N,O-双(三甲基硅基)三氟乙酰胺(BSTFA)硅烷化,以反-2-己烯酸和肉桂酸双内标法定量,利用GC-MS/SIM法同时测定了25种挥发性、半挥发性有机酸。结果表明:此方法测定有机酸具有良好的线性(r2≥0.985)和重复性(RSDs≤8.93%,n=5),平均回收率81.43%~100.58%,检测限为0.03~2.30μg/g,定量限为0.10~7.67μg/g。建立的方法简便快捷,且具有较高的准确度和精密度,适用于烟草中挥发性与半挥发性有机酸的快速和同时测定。     

SBSE-TDS-GC-MS测定烟草表香挥发性与半挥发性成分

以固态萃取搅拌棒为样品前处理技术,采用气相色谱/质谱联用法分析了烟草表香挥发性与半挥发性成分.对影响萃取效果的实验条件进行了考察,并采用正交实验法对影响热解吸的3个主要实验参数(热解吸温度、解吸时间和进样口冷聚焦温度)进行考察,得到优化的实验条件.结果表明,同一样品经6次测定,所得27个组分峰面积的相对标准偏差(RSD...     

不同陈化年份鸢尾挥发性成分的分析研究

为了研究不同陈化年份鸢尾挥发性成分的变化情况,采用同时蒸馏萃取方法分别提取不同陈化年份鸢尾的挥发性成分,将得到的挥发油通过气相色谱-质谱仪进行分离和鉴定,采用峰面积归一化法确定各成分的相对质量分数。从4个不同陈化年份鸢尾挥发油中分别鉴定出37、39、39和38种成分,分别占总量的63.0%、70.4%、75.0%和65.7%。这些成分主要由酸类、酮类、酯类和醛类等化合物组成,其中十四酸、正癸酸、十二酸、6-甲基-α-紫罗兰酮、α-鸢尾酮和辛酸等是主要成分。结果表明,3年陈化的鸢尾挥发油得率最高,得到鉴定的挥发性成分个数最多,其挥发性成分在总成分中所占质量比最大,因此鸢尾的陈化时间选择3年较佳。     

基于小波分析理论的指数平滑模型预测自然陈化中钢渣f-CaO含量

采用自然陈化方法处理滚筒钢渣,跟踪检测渣中游离氧化钙(f-CaO)含量,分析f-CaO含量变化机理;运用小波分析理论和指数平滑模型建立了指数平滑模型,预测滚筒钢渣自然陈化过程中f-CaO含量. 结果表明,自然陈化方法可有效降低滚筒钢渣中f-CaO含量,A类滚筒钢渣自然陈化180 d后f-CaO含量约为1.2%,B类滚筒钢渣自然陈化60 d后f-CaO含量为5.0%~6.0%,满足安全利用要求;基于小波分析理论的指数平滑模型的预测值与实验值吻合较好,相对误差为-3.442%~4.651%,有效提高了滚筒钢渣自然陈化中f-CaO含量预测精度.     

聚酯污水中挥发性脂肪酸测定的改进

聚酯装置产生的废水含有大量的有机物,通过厌氧消化处理产生大量的挥发性脂肪酸,挥发性脂肪酸是污水系统运行的重要控制指标.传统的挥发性脂肪酸的检测采用蒸馏后滴定的方法,检测时间长约3.5-4h且加热过程中需要人员监控加热过程,防止样品蒸干造成蒸馏瓶炸裂等安全隐患,经过对样品组分的分析、实验,进行分析优化,检测时间缩短至1....     

煤制生物氢放大模拟实验研究

在5L厌氧发酵罐内,控制温度为30℃,pH值为6.5,进行为期10d的厌氧发酵产氢实验,对实验过程中液相的pH值、VFA(挥发性脂肪酸)摩尔浓度和COD值进行实时监控分析,并进行纤维素酶活性和氢化酶活性的检测.结果表明,氢气最大体积分数可达到52.3%,氢气最终产率为13.7mL/g.pH值一直下降,最低降至5.46;VFA摩尔浓度基本呈上升趋势,与pH值变化相对应,发酵类型属于丁酸型发酵.COD值呈现先上升后下降的趋势,最高值为4 368mg/L,且最终COD降解率为51.10%.纤维素酶活性在反应第4天出现最高值0.016 9mg/(mL·h),氢化酶活性最高值出现在反应第6天,为0.568mmol H_2/(min·mg).     

陈化过程中不同部位烤烟烟叶香味成分变化的研究

采用SDE-GC/MS法对陈化过程中不同部位烤烟烟叶的香味成分进行分析检测,并按照香味物质的产生来源对分析结果进行了分类研究。结果表明,陈化过程中不同部位烟叶的香味物质的变化情况差别明显。从香味成分的变化情况看,各个部位适宜的陈化时间有所不同:上部烟叶2年以上,中部烟叶1.5~2年,下部烟叶1年左右。     

碳化法纳米SiO2表面结构研究

采用红外、热重、N2吸附等分析方法,研究了碳化法制备的纳米SiO2表面羟基、孔隙结构和吸油值等随陈化pH值、陈化时间及干燥温度的变化关系.实验结果表明,在不同陈化pH值下SiO2凝聚反应速率不同,陈化pH值由2升高到5,凝聚反应加快,颗粒表面羟基含量由1.54个/nm2减少到1.44个/nm2,平均孔径由11.51 nm增大到23.06 nm,吸油值由1.70 cm3/g升高到1.81 cm3/g;在不同陈化时间下SiO2颗粒间凝聚反应进程不同,陈化时间由10 min延长到90 min,颗粒表面羟基含量由1.48个/nm2减少到1.40个/nm2,平均孔径、吸油值变化不明显;在不同干燥温度下颗粒表面羟基脱除程度不同,干燥温度由100℃升高到500℃,表面羟基脱除增多,羟基含量由1.43个/nm2减少到0.70个/nm2,平均孔径由13.2 nm增加到41.07 nm,吸油值由1.82 cm3/g升高到2.00 cm3/g.     

自然陈化过程中红大青筋黄片烟叶致香成分的变化

应用同时蒸馏萃取-气质联用法测定了红花大金元(红大)青筋黄片和正常烟叶中的致香成分含量,研究了青筋黄片致香成分在自然陈化(陈化)期间内的变化规律.结果表明,随着陈化时间延长,青筋黄片的大多数致香成分含量均呈上升趋势,新植二烯含量则呈下降趋势;青筋黄片关键致香成分含量增加比正常烟叶快.表明陈化有利于青筋黄片香气物质的积累从而使得烟叶内在品质得到明显提升并趋近于正常烟叶.     

Investigation on water distribution and state in tobacco leaves with stalks during curing by LF-NMR and MRI

The water distribution and state in tobacco leaves with stalks and without stalks during curing were measured by low-field nuclear magnetic resonance and imaging. Results showed that, moisture content of the stalk and midrib was higher than that of the lamina. Only immobilized and free water were found in the midrib of fresh tobacco leaves, whereas the bound water was found in the lamina and stalk. In addition, the mobility of each water state in the stalk and midrib was stronger than that in the lamina. Water migrated from the stalk to the lamina via the midrib during curing, which resulted in a higher proportion of free water in the lamina and a lower drying efficiency of tobacco leaves with stalks than those of nonstalks.     

Effects of agingmortierella mycelium on production of arachidonic and eicosapentaenoic acids

Arachidonic acid and eicosapentaenoic acid (EPA) are important intermediates of eicosanoid metabolism and are presently the subject of extensive nutritional and medical research. The effects of mycelial aging on production of these fatty acids were investigated as part of a research program directed toward examining the feasibility of economically producing these products by fungal fermentation. Arachidonic acid content ofM. alpina ATCC 32222 increased from 4.1–8.3% to 13–16% during aging while lipid content of mycelium increased from 14–18% to 33–45%. Maximum lipid content produced in biomass during storage declined as harvesting time was increased from 3 to 6 days while maximum arachidonic acid content in lipid increased. Maximum lipid and arachidonic acid was produced during aging at pH 8, whereas arachidonic acid content of lipids was highest in mycelium aged at pH 6. EPA content ofM. elongata NRRL 5513 biomass increased during aging, reaching a maximum after 22–28 days. When the pH of the culture prior to harvesting was adjusted in the range of pH 4–9, pH values for development of maximum EPA in biomass and in lipids during storage were found to be 6 and 7, respectively. Temperature of aging had little effect on arachidonic acid or EPA content.     

并流滴加法制备大孔容纤维状γ-氧化铝

以偏铝酸钠（NaAlO₂）-硫酸铝（Al₂（SO₄）₃）为原料,利用并流滴加法控制沉淀过程的反应pH,并通过调节原料浓度、老化pH和加入表面活性剂十二烷基苯磺酸钠（SDBS）等方法,成功制备得到了大孔容纤维状的γ-氧化铝。实验发现,不同的原料浓度会影响成核-生长过程,得到不规则片状、纤维状或颗粒状等不同形貌的γ-氧化铝,其中纤维状可形成大孔容。当NaAlO₂浓度为0.5~0.75 mol/L,反应pH控制在8~9.5,老化pH控制在9左右时,得到的γ-氧化铝呈纤维状,孔容较大;此外,在老化过程中添加SDBS可进一步提高孔容,并改善孔径分布。本方法成功制备出孔容为1.35~2.19 ml/g、比表面积为300~500 m²/g、平均孔径为14~21 nm的纤维状γ-氧化铝,纤维长度为50~60 nm,纤维宽度约5 nm,可为渣油加氢过程提供一种性能良好的催化剂载体。     

共沉淀法制备纳米羟基磷灰石

以硝酸钙、磷酸混合水溶液为前驱体,以氨水为沉淀剂,采用共沉淀法制备纳米羟基磷灰石。探讨了加料方式、加料速度、Ca-P溶液初始浓度、陈化温度、陈化时间以及反应pH值等工艺条件对纳米羟基磷灰石的结晶粒度与分散性的影响。结果表明,采用将氨水加入Ca-P溶液、快速加料的方式,在Ca2+浓度为1.0mol.L-1、陈化温度为60℃、陈化时间为12h、反应pH值为10的条件下可高效制备分散性较好的短棒状纳米羟基磷灰石粉体。     

生物固定化技术及其在烟叶陈化过程中的应用

简述了生物固定化技术的主要特点、壁材的选择、生产方法及在烟草加工过程中的控制释放机理等,主要对生物活性物质微胶囊固定化技术在烟草陈化过程中的应用、前景及存在的问题作了描述和分析。     

The effect of thermal aging on xanthan solutions

The viscosity stability of xanthan solutions is crucial to petroleum recovery processes. The effects of oxygen concentration, pH, and temperature on viscosity during aging up to 6 months were studied. The structure modifications of the xanthan (substituent contents, weight-average molecular weights) with aging times were followed and related to viscosity loss. In all cases, the acetyl groups were hydrolyzed. The best stability to thermal aging corresponds to neutral or basic conditions with very low oxygen concentrations. At these conditions the viscosity was stabilized to about 50% of its initial value after 6 months at 80°C. In these cases the pyruvate groups were not hydrolyzed. The stabilization of main chain breaks in the ordered xanthan conformation improves the stability results.     

Damping of polymer composite materials for flywheel applications

Damping of pure resin and T700/epoxy composite lamina in longitudinal and transverse directions were investigated experimentally and analytically. The effect of aging on damping was also studied by placing samples at 60°C in an oven for extended periods of time and using results from time‐dependant studies. Damping master curves vs. frequency were constructed from individual curves at various temperatures using the match principle. Master curves constructed using Arrhenius equation matched those constructed using the match principle for the matrix but not for the composite. The damping response of the composite lamina was used to predict the response of laminate composites. It was found that for a specific frequency range, damping decreases with the increase in aging time, and that damping is dependent on the direction of fibers, highlighting the importance of multi‐direction reinforcement for composite flywheel rotors. Laminate damping was also experimentally evaluated for a number of configurations (0°, ± 45° and 90°). The half power method was used to identify the damping characteristics for coupon samples. These experimental measurements matched results from lamina investigation and indicated that the 0° specimen has the lowest damping ratio in the fiber direction, while the highest damping ratio corresponds to the 45° fiber orientation. It was also observed that the damping factor was only weakly dependent upon frequency for a broad range of frequencies, which is an important result with regard to simulation and stability analyses. POLYM. COMPOS., 26:498–508, 2005. © 2005 Society of Plastics Engineers     

Chemical composition evolution of YAG co-precipitate determined by pH during aging period and its effect on precursor properties

The properties of YAG precursors aged at various pH levels for different aging times were examined to explore the influence of pH on the evolution of the chemical composition and the morphology of the precipitate, on the variation of phase composition during the calcination process. Precursors obtained at pH lower than 8.0 can be transformed into mono-phase YAG by calcination at low temperature, while those obtained at higher pH exhibit a variety of crystalline structures. Aging at high pH increased the impurity content of the calcined powder. Based on monitoring the pH during the precursor aging process, and the measurement of the Y/Al ratio in the precipitates, the mechanism of the chemical variation is discussed and the influence of pH and aging time on the synthesis of YAG precursor is discussed.