Temperature effects extraction

Different types of other coal liquefaction processes have been also developed to convert coals to liqnid hydrocarbon fnels. These include high-temperature solvent extraction processes in which no catalyst is added. The solvent is usually a hydroaromatic hydrogen donor, whereas molecnlar hydrogen is added as a secondary source of hydrogen. Similar but catalytic liquefaction processes use zinc chloride and other catalysts, usually under forceful conditions (375-425°C, 100-200 atm). In our own research, superacidic HF-BFo-induced hydroliquefaction of coals, which involves depolymerization-ionic hydrogenation, was found to be highly effective at relatively modest temperatnres (150-170°C). 

When PET is extracted with water no detectable quantities of ethylene glycol or terephthaUc acid can be found, even at elevated extraction temperatures (110). Extractable materials are generally short-chained polyesters and aldehydes (110). Aldehydes occur naturally iu foods such as fmits and are produced metabohcaHy iu the body. Animal feeding studies with extractable materials show no adverse health effects. 

The producer of column No. 6 tried to supplementary remove admixtures from the gel matrix by applying liquid extractions. He revealed that the extraction process was very slow and that the apparently clean material started to bleed again after some time or when the temperature of extraction was raised. This result indicates that the retention properties of SEC columns may change in the course of their use as a result of cleaning their surface. Maybe the recipes for the gel synthesis will have to be modified to suppress the effects of additives. It seems that the producer of column No. 5 is not far from the ideal situation, at least for the PMMA-toluene system. We cannot exclude... 

The effectiveness of a number of crude oil dispersants, measured using a variety of evaluation procedures, indicates that temperature effects result from changing viscosity, dispersants are most effective at a salinity of approximately 40 ppt (parts per thousand), and concentration of dispersant is critical to effectiveness. The mixing time has little effect on performance, and a calibration procedure for laboratory dispersant effectiveness must include contact with water in a manner analogous to the extraction procedure otherwise, effectiveness may be inflated [587]. Compensation for the coloration produced by the dispersant alone is important only for some dispersants. 

Effective temperatures. When extracting stream data to represent the heat sources and heat sinks for the heat exchanger network problem, care must be exercised so as to represent the availability of heat at its effective temperature. For example, consider the part of the process represented in Figure 19.8. The feed stream to a reactor is preheated from 20°C to 95°C before entering the reactor. The effluent from the reactor is at 120°C and enters a quench that cools the reactor effluent from 120°C to 100°C. The vapor leaving the quench is at 100°C and needs to be cooled to 40°C. The quenched liquid also leaves at 100°C but needs to be cooled to 30°C. How should the data be extracted ... 

Continuous Multicomponent Distillation Column 501 Gas Separation by Membrane Permeation 475 Transport of Heavy Metals in Water and Sediment 565 Residence Time Distribution Studies 381 Nitrification in a Fluidised Bed Reactor 547 Conversion of Nitrobenzene to Aniline 329 Non-Ideal Stirred-Tank Reactor 374 Oscillating Tank Reactor Behaviour 290 Oxidation Reaction in an Aerated Tank 250 Classic Streeter-Phelps Oxygen Sag Curves 569 Auto-Refrigerated Reactor 295 Batch Reactor of Luyben 253 Reversible Reaction with Temperature Effects 305 Reversible Reaction with Variable Heat Capacities 299 Reaction with Integrated Extraction of Inhibitory Product 280... 

Lagenfeld et al. [116] studied the effect of temperature and pressure on the supercritical fluid extraction of polychlorobiphenyls and polyaromatic hydrocarbons from soil. At 50°C raising the pressure from 356 to 650atm had no effect on recovery of polychlorobiphenyls. A temperature of 200°C was necessary for effective extraction. 

The robustness of an analytical procedure is a measure of its capacity to remain unaffected by small but deliberate variations in the analytical procedure parameters. The robustness of the analytical procedure provides an indication of its reliability during normal use. The evaluation of robustness should be considered during development of the analytical procedure. If measurements are susceptible to variations in analytical conditions, the analytical conditions should be suitably controlled or a precautionary statement should be included in the procedure. For example, if the resolution of a critical pair of peaks was very sensitive to the percentage of organic composition in the mobile phase, that observation would have been observed during method development and should be stressed in the procedure. Common variations that are investigated for robustness include filter effect, stability of analytical solutions, extraction time during sample preparation, pH variations in the mobile-phase composition, variations in mobile-phase composition, columns, temperature effect, and flow rate. 

Norbert Berkowitz I think the kinetic treatment of the experimental data is of questionable validity. The extraction process is evidently accompanied by considerable changes in the geometry of the coal particles (e.g., swelling and dispersion) there is the unresolved question of whether the extract forms a solution or dispersion finally, there is an obvious but somewhat indefinite effect of coal decomposition. The latter point alone would make determining a temperature effect (and hence, calculating an activation energy ) very difficult practically, if not impossible. 

The same authors have also studied the effect of the probe temperature and the extraction voltage on the sensitivity and fragmentation of several OPPs. As a general rule, it was found that the probe temperature has a greater effect on compound sensitivity than on fragmentation. A compromise between sensitivity and structural information has to be defined as a result, the probe temperature and extraction voltage have to be optimized, depending on the aim of each study (43). 

S Lacorte, C Molina, D Barcelo. Temperature and extraction voltage effect on fragmentation of organophosphorus pesticides in liquid chromatography atmospheric pressure chemical ionization mass spectrometry. J Chromatogr A 795 13-26, 1998. 

Hubert et al. [101] state that accelerated solvent extraction compared to alternatives such as Soxhlet extraction, steam distillation, microwave extraction, ultrasonic extraction and, in some cases, supercritical fluid extraction is an exceptionally effective extraction technique. Hubert et al. [ 101 ] studied the effect of operating variables such as choice of solvent and temperature on the solvent extraction of a range of accelerated persistent organic pollutants in soil, including chlorobenzenes, HCH isomers, DDX, polychlorobiphenyl cogeners and polycyclic aromatic hydrocarbons. Temperatures ofbetween 20 and 180 °C were studied. The optimum extraction conditions use two extraction steps at 80 and 140 °C with static cycles (extraction time 35 minutes) using toluene as a solvent and at a pressure of 15 MPa. 

The use of dilute aqueous solutions of HC1 [142, 152, 153] or phosphate buffer (pH 6.5-5) [133] are very appropriate for the extraction of amphetamines and other compounds in basic character. In this case, the extraction times are about 20 h. When supported by increased temperature, the extraction lasts only for 2 h, but it is not effective for the extraction of lipophilic compounds such as THC. The use of aqueous solutions of HC1 causes partial or complete hydrolysis of some substances, so phosphate buffer at pH 5 is preferred for the determination of cocaine and 6-MAM in these conditions these two molecules appear to have increased stability [154], In addition to acidic aqueous solutions, formic acid instead of hydrochloric acid solutions are also used in organic solvents [136],... 

Table 4 shows the surface properties of skeletal copper catalysts produced by leaching a 50wt% Cu alloy in aqueous sodium hydroxide solution at 293 K. It shows that the surface area decreases with increasing particle size of the alloy. Table 5 shows the effect of temperature of extraction on the surface area and pore structures of completely leached 1000-1180 fim particles of the 50wt% Cu alloy. The results show... 

TableS. The effect of the temperature of extraction on the surface area and pore structure of completely leached 100-1180 pm particles of CuA12 alloy (Ref. 22).

The effect of the temperature was investigated only in the supercritical range (32.5-50 °C). A rise in temperature at constant pressure led to an increase in extraction yield (Figure 5a). Similar temperature effects was observed for cv.s-chrysanthemic acid. The temperature dependency of enantiomeric excess of the extracts obtained from single extraction was different for the different acids. The enantiomeric excess of the cv.s-chrysanthemic acid extracts were 38 % and 75 % at temperatures 47 °C and 32 °C respectively. The enantiomeric excess of the ibuprofen was independent of the temperature (Figure 5b). 

Effects of pressure and temperature on extraction of oily material from 20g herb samples (CP grade C02 unless otherwise stated)... 

Effect of extraction temperature and extracting fluid composition... 

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