Trace analysis of surfactants derived from fatty alcohols II. Hydrolysis and enrichment techniques

Summary Acid catalyzed hydrolysis of fatty alcohol sulfates under reflux condition or by microwave heating is compared. Microwave hydrolysis turned out to be faster and more convenient to use. The combination of reflux hydrolysis of fatty alcohol sulfates or alkyl polyglycosides and the simultaneous steam distillation of the generated fatty alcohols gives a very powerful sample preparation and enrichment method for fatty alcohol sulfates and alkyl polyglycosides. The preconcentrated fatty alcohols are derivatized and detected via fluorescence detection. The applicability of the method is demonstrated by the analysis of fatty alcohol sulfates in cosmetics and in river water as matrices spiked with approximately 4 ppb fatty alcohol sulfates.     

Optimization of steam explosion to enhance hemicellulose recovery and enzymatic hydrolysis of cellulose in softwoods

A combination of Douglas fir heartwood and sapwood chips were steam pretreated under three conditions as measured by the Severity Factor (log R_o), which incorporated the time, temperature/pressure of pretreatment. By adjusting the steam pretreatment conditions, it was hoped to recover the majority of the hemicellulose component as monomers in the water-soluble stream, while providing a cellulosic-rich, water-insoluble fraction that could be readily hydrolyzed by cellulases. These three conditions were chosen to represent either high hemicellulose sugar recovery (low severity [L], log R_o=3.08), high-enzyme hydrolyzability of the cellulosic component (high severity [H], log R_o=4.21), and a compromise between the two conditions (medium severity [M], log R_o=3.45). The medium-severity pretreatment conditions (195°C, 4.5 min, 4.5% SO₂ logR_o=3.45) gave the best compromise in terms of relatively high hemicellulose recovery after stream pretreatment and the subsequent efficiency of enzymatic hydrolysis of the water-insoluble cellulosic fraction. The percent recovery of the original hemicellulose in the water-soluble fraction dropped significantly when the severity was increased (L-76.8%, M-64.7%, and H-37.5%). However, the ease of enzymatic hydrolysis of the cellulose-rich, water-insoluble fraction increased with increasing severity (L-24%, M-86.6%, and H-97.9%). Although more severe pretreatment conditions provided optimum hydrolysis of the cellulosic component, less severe conditions resulted in better recovery of the combined hemicellulose and cellulosic components.     

CFETR水冷包层一回路系统初步设计和配套设备的模拟

通过设计两套独立的聚变堆一回路系统(PHTS),分别为増殖区(BZ)和第一壁(FW)提供冷却,采用在FW PHTS和电力转换系统(PCS)之间设计一套中间传热系统(IHTS)的方案,解决了托卡马克装置脉冲操作对PCS的影响.同时利用Ebsilon软件建立一套核电厂配套设备(BOP)的系统模型,模拟该系统在1.5GW聚变...     

Determination of carboxylic acids and phenols in water by extractive alkylation using pentafluorobenzylation,glass capillary GC and electron capture detection

A method is presented for the simultaneous determination of a wide range of carboxylic acids and phenols in water. Extractive alkylation is used with the tetrabutylammonium ion as counter ion and pentafluorobenzylbromide as alkylating agent. Extracts are analyzed by glass capillary gas chromatography and electron capture detection. Using one ml of water sample, the detection limit lies in the range of 1–10 μg/l. Application has been made to the analysis of steam condensate and domestic sewage effluent.     

Steam distillation and supercritical fluid extraction of some Mexican spices

Summary By means of steam distillation and supercritical fluid extractions, we are in a process of evaluating the essential oil and the oleoresin quality and yield obtain respectively by the above methods outlined.Our area of interest is the isolation, separation and purification of compounds whose applications are well supported by the food technology demands.We pretend to characterize the aromatic components of edible or other commercial oils from the widespread spices and plant natural collections, throughout the country of Mexico.The facilities for the obtention of reference standards characteristic of our flora specimens, is under research.Poster presented at the First Symposium of Supercritical Fluids, Nice, France, 14–17 October, 1988     

Determination of resistance to coking in the steam reforming of hydrocarbons

For a long time the microbalance reactor has played an important role in catalyst deactivation studies, but it has a number of limitations. The initial temperatures of coking of Ni and Ni-Mo catalysts in the temperature-programmed reaction (TPReaction) of n-butane with steam are compared with the results of coking rates obtained by the traditional thermogravimetric method. The investigations show good agreement of the results.     

Steam Reforming of Methanol Over Pd-Zn Catalysts

Heating the physical mixtures of Pd and Zn selectively yielded PdZn or Pd_3.9Zn_6.1 alloy. These alloys were highly selective for the steam reforming of methanol.     

Influence of steam explosion on the thermal stability of cellulose fibres

The aim of the present study was to compare the effect of different steam explosion treatments on the thermal degradation of a bleached cellulose. The intensity of a steam explosion treatment, which allows breakdown of the structural lignocellulosic material was determined by a correlation between time and temperature of the process.Results of this study showed that thermal degradation of cellulose fibres was limited when the severity factor applied was below 4.0. For higher intensities, determination of the degradation products in the water-soluble extract showed an important increase of the 5-hydroxymethyl-furfural concentration with the temperature. When the severity factor reached 5.2., TGA analysis showed that the increase of degradation products was coupled to an increase of the char level meaning a strong degradation of the cellulose. dTGA behaviour also showed that thermal stability of the steam explosion samples decreased with the intensity of the treatment. To conclude, a theoretical diagram predicting the degradation of the cellulose during the steam explosion treatment was established.     

Composite Cathode Based on Redox-Reversible Nb2TiO7 for Direct High-Temperature Steam Electrolysis

Ni/YSZ fuel electrodes can only operate under strongly reducing conditions for steam electrolysis in an oxide-ion-conducting solid oxide electrolyzer (SOE). In atmosphere with a low content of H₂ or without H₂, cathodes based on redox-reversible Nb₂TiO₇ provide a promising alternative. The reversible changes between oxidized Nb₂TiO₇ and reduced Nb_1.33Ti_0.67O₄ samples are systematically investigated after redox-cycling tests. The conductivities of Nb₂TiO₇ and reduced Nb_1.33Ti_0.67O₄ are studied as a function of temperature and oxygen partial pressure and correlated with the electrochemical properties of the composite electrodes in a symmetric cell and SOE at 830 oC. Steam electrolysis is then performed using an oxide-ion-conducting SOE based on a Nb_1.33Ti_0.67O₄ composite fuel electrode at 830 oC. The current-voltage and impedance spectroscopy tests demonstrate that the reduction and activation of the fuel electrode is the main process at low voltage; however, the steam electrolysis dominates the entire process at high voltages. The Faradic efficiencies of steam electrolysis reach 98.9% when 3%H₂O/Ar/4%H₂ is introduced to the fuel electrode and 89% for that with introduction of 3%H₂O/Ar.     

Comparative study of extraction techniques for determination of garlic flavor components by gas chromatography–mass spectrometry

Several sampling techniques based on steam distillation (SD), simultaneous distillation and solvent extraction (SDE), solid-phase trapping solvent extraction (SPTE), and headspace solid-phase microextraction (HS-SPME) have been compared for the determination of Korean garlic flavor components by gas chromatography–mass spectrometry (GC–MS). Diallyl disulfide (57.88%), allyl sulfide (23.59%), and diallyl trisulfide (11.40%) were found to be the predominant flavor components of garlic samples extracted by SDE whereas these components were at levels of 89.77%, 2.43%, and 3.89% when the same sample was extracted by SD, 97.77%, 0.17%, and 0.10% by SPTE, and 97.85%, 0.01%, and 0.01% by HS-SPME using the 50/30-m divinyl benzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber. Thermal degradation of components such as allyl methyl sulfide, dimethyl disulfide, and thiirane were observed for SDE and SD but not for SPTE or HS-SPME. HS-SPME had several advantages compared with SD, SDE, and SPTE—rapid solvent-free extraction, no apparent thermal degradation, less laborious manipulation, and less sample requirement. Five different fiber coatings were evaluated to select a suitable fiber for HS-SPME of garlic flavor components. DVB/CAR/PDMS was most efficient among the five types of fiber investigated.