Extraction, solvent conversion

If the analyte contains either an acidic or a basic functionality, adjusting the pH of the extraction solvent to make the analyte either ionic or nonionic may be advantageous. To make an analyte that contains an acidic or basic functionality nonionic for extraction into a nonpolar solvent, a small amount (5% or less) of an organic acid (such as acetic acid or trifluoroacetic acid) or organic base (triethylamine) along with methanol (about 10%) can be added to diethyl ether or ethyl acetate. Conversely, buffered solutions can be used to control the pH precisely in such a way as to control the charge on an analyte and thus improve its extraction efficiency into polar solvents. 

It is well known that coal reactivity depends on the solvent, the conditions of hydroliquefaction, and the composition of the coal. Different extracting solvent results in different conversion, but it can be considered that the different conversion shows a similar tendency to coal reactivity. Thus, it is desirable that the parameter representing coal reactivity shows essentially the same tendency, despite the conditions of hydroliquefaction. Accordingly comparison of parameters was carried out, using some previously reported results (2, 3). 

The procedures are very easy to reproduce and to scale up. Reaction products are isolated by evaporation of the extraction solvent (e.g. hexane, pentane). In the case of the carene halohydrin, further product purification is not necessary if reaction is allowed to proceed until total substrate conversion due to the high selectivity of product formation. 

The yield of glucolimnanthin 1 and nitrile 2 in seed meal by extraction with mixtures of water and MeOH was less critical and maximal at all proportions below 80% MeOH (Fig. 10.4b). For extraction of seed meal we chose 50% aqueous MeOH as the extraction solvent. The extraction yield of glucolimnanthin 1 appears to be poor at 50% aqueous MeOH in Fig. 10.4a, but the low yield in this case is primarily due to enzyme-mediated conversion into its breakdown products 2 and 3. 

This method for the conversion of tosylates into the corresponding bromides is a variant of the method described in the previous experiment, It is more suitable for volatile bromides (with boiling points up to 55 C/15 mmHg) than the acetone-method because the isolation procedure is more convenient (no frequent extraction with pentane or EtjO, no time-consuming distillative separation from the extraction solvent). 

Although solvents may form two visibly distinct phases when mixed together, they are often somewhat soluble in each other and will, in fact, become mutually saturated when mixed with each other. Data on the solubility of various solvents in water (Table 2.2) and on the solubility of water in other solvents (Table 2.3) should be consulted when selecting an extraction solvent pair. For example, 1.6% of the solvent dichloromethane (or methylene chloride) is soluble in water. Conversely, water is 0.24% soluble in dichloromethane. According to Table 2.3, when the phases are separated for recovery of the extracted analyte, the organic solvent layer will contain water. Similarly, according to Table 2.2, after extraction the depleted aqueous phase will be saturated with organic solvent and may pose a disposal problem. (Author s note I previously recounted [43] my LLE experience with disposal of extracted aqueous samples that were cleaned of pesticide residues but saturated with diethyl ether. Diethyl ether is 6.89% soluble in water at 20° C.)... 

Compounds found in anolyte extracts from experiments with the RCA were acetone, methyl acetate, acetic acid, isopropyl acetate, dioctyl phthalate, and an unknown nitro species characterized by a base peak at 46 daltons. Isopropyl acetate was probably formed by the acid-catalyzed esterification of IPA (extraction solvent) and acetic acid (found in the anolyte) in the presence of HNO3. Similarly, methyl acetate could have been formed from the reaction of methanol with acetic acid. Methanol could have formed during the destruction of BZ. Since no residual methanol was found, it is assumed that the conversion to methyl acetate was complete. Results are summarized in Table 2. 

Chlorinated solvents have been extensively used as extraction solvents. As is shown in Table 6.1, these solvents have very limited solubilities in water (1.6% for dichloromethane to 0.0025% for l,2,4-trichloroben2ene). Conversely, these solvents all offer low water solubilities, even when water saturated (0.31% for 1,2-dichlorobenzene to 0.008% for carbon tetrachloride). The chlorinated solvents also offer a wide range of polarities (in order of decreasing polarity) n-butyl chloride, dichloromethane, chloroform, and carbon tetrachloride. Most chlorinated solvents are still readily available in high-purity form, but environmentally driven legal restrictions are beginning to take effect and will, ultimately, severely limit or totally prohibit their production and use. 

A complete process design and costings have been produced for the conversion of de-proteined whey into a CBE yeast fat (Davies and Holdsworth, 1992). The process has run in large-scale trials in a 250m bubble fermenter. For the extraction of the fat, a novel extraction process was developed that used a continuous ball-mill and a mixture of propan-2-ol/hexane as extracting solvent. Recoveries in excess of 97% were achieved from the yeast cream coming out of the nozzle separator. 

In the oxidative solvent extraction processes, the AAT compounds are first oxidized to AATS using various oxidants (notably hydrogen peroxide) before they are removed by solvent extraction. Solvent is reeovered by distillation for recycle Ifom the ultra-low-sulfur raffinate and high-sulfur extract. The conversion cost consists primarily of the cost of oxidant, solvent losses, fuel cost and capital charges. Where the reduction of poly-aromatics from the ULS diesel is desired, the solvent-based EDS processes may present advantages, because the extract fraction can be adjusted to meet this need. However, high levels of olefins may limit the oxidation approach because they can consume additional oxidant and produce undesired byproducts. 

Preparation of chloride-free HQO by electrodialysis, distillation, or solvent extraction before conversion to NaQO with alkali [22-27]... 

The foremost separation process is crude distillation and in second place, if deeper conversion is envisaged, solvent extraction (deasphalting). 

METHOD 2 [89]--1M MDA or benzedrine and 1M benzaldehyde is dissolved in 95% ethanol (Everclear), stirred, the solvent removed by distillation then the oil vacuum distilled to give 95% yellow oil which is a Schiff base intermediate. 1M of this intermediate, plus 1M iodomethane, is sealed in a pipe bomb that s dumped in boiling water for 5 hours giving an orangy-red heavy oil. The oil is taken up in methanol, 1/8 its volume of dH20 is added and the solution refluxed for 30 minutes. Next, an equal volume of water is added and the whole solution boiled openly until no more odor of benzaldehyde is detected (smells like almond extract). The solution is acidified with acetic acid, washed with ether (discard ether), the MDMA or meth freebase liberated with NaOH and extracted with ether to afford a yield of 90% for meth and 65% for MDMA. That s not a bad conversion but what s with having to use benzaldehyde (a List chemical) Strike wonders if another aldehyde can substitute. 

Pollution Prevention. Procedures haven been developed for recovery of composite ammonium perchlorate propellant from rocket motors, and the treatment of scrap and recovered propellant to reclaim ingredients. These include the use of high pressure water jets or compounds such as ammonia, which form fluids under pressure at elevated temperature, to remove the propellant from the motor, extraction of the ammonium perchlorate with solvents such as water or ammonia as a critical fluid, recrystalli2ation of the perchlorate and reuse in composite propellant or in slurry explosives or conversion to perchloric acid (166,167). 

Synthetic Fuel. Solvent extraction has many appHcations in synthetic fuel technology such as the extraction of the Athabasca tar sands (qv) and Irish peat using / -pentane [109-66-0] (238) and a process for treating coal (qv) using a solvent under hydrogen (qv) (239). In the latter case, coal reacts with a minimum amount of hydrogen so that the solvent extracts valuable feedstock components before the soHd residue is burned. Solvent extraction is used in coal Hquefaction processes (240) and synthetic fuel refining (see Coal conversion processes Fuels, synthetic). 

Liquid Fuels. Liquid fuels can be obtained as by-products of low temperature carbonization by pyrolysis, solvent refining, or extraction and gasification followed by catalytic conversion of either the coal or the products from the coal. A continuing iaterest ia Hquid fuels has produced activity ia each of these areas (44—46). However, because cmde oil prices have historically remained below the price at which synthetic fuels can be produced, commercialization awaits an economic reversal. 

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