Distillation, Extraction

The volatile aroma compounds, together with some water, are removed by vacuum distillation from an aqueous food suspension. The highly volatile compounds are condensed in an efficiently cooled trap. The organic compounds contained in the distillate are separated from the water by extraction or by adsorption to a hydrophobic matrix and reversed phase chromatography and then prefractionated. 

The apparatus shown in Fig. 5.5 is recommended for the gentle isolation of aroma substances from aqueous foods by means of distillation. In fact, a condensate can be very quickly obtained because of the short distances. As in all distillation processes, the yield of aroma substances decreases if the food or an extract is fatty (Table 5.7). 

After application of high vacuum ( 5 mPa) the distillation procedure is started by dropping the 

Solid foods are first extracted, the addition of water may be required to increase the yield of aroma substances. 

An extraction combined with distillation can be achieved using an apparatus designed by Likens-Nickerson (Fig. 5.6). 

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Hydrolysis of a sulphonamide. Mix 2 g. of the sulphonamide with 3-5 ml. of 80 per cent, sulphuric acid in a test-tube and place a thermometer in the mixture. Heat the test-tube, with frequent stirring by means of the thermometer, at 155-165° until the solid passes into solution (2-5 minutes). Allow the acid solution to cool and pour it into 25-30 ml. of water. Render the resulting solution alkaline with 20 per cent, sodium hydroxide solution in order to liberate the free amine. Two methods may be used for isolating the base. If the amine is volatile in steam, distil the alkaline solution and collect about 20 ml. of distillate extract the amine with ether, dry the ethereal solution with anhydrous potassium carbonate and distil off the solvent. If the amine is not appreciably steam-volatile, extract it from the alkaline solution with ether. The sulphonic acid (as sodium salt) in the residual solution may be identified as detailed under 13. 

Isolate. A relatively pure chemical produced from natural raw materials by physical means, eg, distillation, extraction, crystallization, etc, and therefore natural or by chemical means, ie, via hydrolysis, bisulfite addition products, and regeneration, etc, and therefore artificial by 1993 U.S. labeling regulations. 

Refinery product separation falls into a number of common classes namely Main fractionators gas plants classical distillation, extraction (liquid-liquid), precipitation (solvent deasphalting), solid facilitated (Parex(TM), PSA), and Membrane (PRSIM(TM)). This list has been ordered from most common to least common. Main fractionators are required in every refinery. Nearly every refinery has some type of gas plant. Most refineries have classical distillation columns. Liquid-liquid extraction is in a few places. Precipitation, solid facilitated and membrane separations are used in specific applications. 

Distillation, extractive distillation, liquid-liquid extraction and absorption are all techniques used to separate binary and multicomponent mixtures of liquids and vapors. Reference 121 examines approaches to determine optimum process sequences for separating components from a mixture, primarily by distillation. 

Reliable analytical methods are available for determination of many volatile nitrosamines at concentrations of 0.1 to 10 ppb in a variety of environmental and biological samples. Most methods employ distillation, extraction, an optional cleanup step, concentration, and final separation by gas chromatography (GC). Use of the highly specific Thermal Energy Analyzer (TEA) as a GC detector affords simplification of sample handling and cleanup without sacrifice of selectivity or sensitivity. Mass spectrometry (MS) is usually employed to confirm the identity of nitrosamines. Utilization of the mass spectrometer s capability to provide quantitative data affords additional confirmatory evidence and quantitative confirmation should be a required criterion of environmental sample analysis. Artifactual formation of nitrosamines continues to be a problem, especially at low levels (0.1 to 1 ppb), and precautions must be taken, such as addition of sulfamic acid or other nitrosation inhibitors. The efficacy of measures for prevention of artifactual nitrosamine formation should be evaluated in each type of sample examined. 

Removal of reaction products can shift the equilibrium, forcing the reaction to go to completion. This can be effected by evaporation of products from the reaction mixture (reactive distillations), extraction (including supercritical extraction) of products from the reaction mixture (reactive extractions), or membrane processes. Counter- and cocurrent operation also falls within this category. If the reaction is equilibrium-limited or inhibited by reaction products countercurrent operation outperforms cocurrent operation. 

Separations for removing undesirable by-products and impurities, and making suprapure fine chemicals constitute a major fraction of the production costs. There is an enormous variety of methods for product separation and purification and many books on the subject have been published. Here, we deal with the problem in a very general way and we refer the reader to advanced books for details. Conventional techniques for product isolation and purification, such as fractional distillation, extraction, and crystallization, still predominate. Some guidelines for scale-up of these techniques and producing experimental data for scale-up are given in Chapter 5. More information on specific separation and purification techniques applied to particular problems of fine chemicals manufacture the reader can find in Chapter 6. 

Maignial, L., Pibrot, P., Bonetti, G., Chaintrau, A., and Marion, J. P. (1992). Simultaneous distillation-extraction under static vacuum Isolation of volatile compounds at room temperature. J. Chromatogr. A 606, 87-94. 

The most frequently used methods of analyte isolation and concentration for organic compounds involve distillation, extraction auid adsorption techniques. Some typical applications of these techniques and their attendant -advantages and disadvantages for the analysis of trace organic solutes in water are summarized in Table 8.1 [4,26]. These methods will be elaborated on below and in subsequent sections of this chapter. 

Solid-phase microextraction eliminates many of the drawbacks of other sample preparation techniques, such as headspace, purge and trap, LLE, SPE, or simultaneous distillation/extraction techniques, including excessive preparation time or extravagant use of high-purity organic solvents. SPME ranks amongst other solvent-free sample preparation methods, notably SBSE (Section 3.5.3) and PT (Section 4.2.2) which essentially operate at room temperature, and DHS (Section 4.2.2),... 

QQQ, QqQ Triple quadrupole analyser SDE Simultaneous distillation extraction... 

Once the standards are set and the pollution sources analyzed, the solution to the problem is no different than the design of any other chemical plant. The methods used may be any of those presented previously plus a number that are more esoteric. The one thing that is different, as noted, is that the pollutants are often present in very low concentrations. When this is true such standard methods as distillation, extraction, and crystallization are usually too expensive. 

An autocatalytic reaction may be able to proceed in. the absence of the catalyst. In some cases the catalytic product may be removed as it forms, by distillation, extraction, precipitation, or some other means. The process, A => B + P, may have the rate equation... 

Define recrystallization, distillation, fractional distillation, extraction, liquid-liquid extraction, solvent extraction, countercurrent distribution, liquid-solid extraction, and chromatography. 

As documented in Chapter 5, zeolites are very powerful adsorbents used to separate many products from industrial process steams. In many cases, adsorption is the only separation tool when other conventional separation techniques such as distillation, extraction, membranes, crystallization and absorption are not applicable. For example, adsorption is the only process that can separate a mixture of C10-C14 olefins from a mixture of C10-C14 hydrocarbons. It has also been found that in certain processes, adsorption has many technological and economical advantages over conventional processes. This was seen, for example, when the separation of m-xylene from other Cg-aromatics by the HF-BF3 extraction process was replaced by adsorption using the UOP MX Sorbex process. Although zeolite separations have many advantages, there are some disadvantages such as complexity in the separation chemistry and the need to recover and recycle desorbents. 

Olivetol. (5-Alkyl Resourcinol) BER 69, 1644 (1936). Mix 25 g of ethyl-3,4,5-trimethoxy benzoyl acetate and 2.0 g of clean sodium in 100 ml ethanol and warm to react. Add 2 g n-propyl iodide (this may be replaced with n-amyl iodide) and heat on a steam bath for 12 hours, then neutralize and remove the ethanol by distillation. Extract the residue with ether, dry, and evaporate in vacuo to get 30 g of the alkyl acetate. Heat 22 g of this acetate in 5% KOH ethanolic solution for 1 hour at 50° and let stand to precipitate 14 g of 3,4,5-trimethoxyvalerophenone. Mix 11 g of the above product with 60 g of sodium in 600 ml ethanol. Warm and after dissolving the sodium add 2 liters of water. M e acidic with HCl acid and remove the ethanol by distillation. Extract with ether, dry, and evaporate the ether in vacuo to get if. g olivetol dimethyl ether. To demethylate this ether add it to 70 ml of hydrogen iodide and heat to boiling and reflux for two hours. Distill and keep the fraction at 160°-170° with 3-4 mm of vacuum applied to the distillation set-up. Yield about 6 g. 

C) Steam distillation, extraction, and evaporation (Waller et al. 113. 14]) were completed and the resulting mixtures bioassayed. 

Uri ne Acidify steam distill extract with methylene chiori de GC/MS No data No data Angerer 1985 o... 

We typically think of the chemical reactor as the unit in which reactions are run and that the reactor is preceded and followed by separation units such as distillation, extraction, centrifugation, etc., to remove reactants fi om products and to prepare products with required purities. In fact, a crucial feature of many chemical reactors is that they involve the integration of chemical reaction and separation in a single chemical reactor. 

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