Reactive separation extraction

Residuum oil supercritical extraction-petroleum deasphalting Polymer fractionation Edible oils fractionation Analytical SGF extraction and chromatography Reactive separations... 

Method A Aqueous NaOH (50%, 50 ml) is added dropwise to the reactive substrate (0.2 mol), CHBr2F (39 g, 0.2 mol) and TEBA-Cl (0.8 g, 3.5 mmol) in CH2CI2 (50 ml). The reaction is exothermic and refluxes spontaneously after 10 min. Heating is continued for a further 3 h and, finally, the mixture is stirred at room temperature for 1.5 h before being diluted with H20 (2000 ml) and neutralized with HC1 (10%). The aqueous phase is separated, extracted with CH2C12 (3 x 100 ml), and the combined organic solutions are washed well with aqueous NaHCO, (sat. soln.) and H20, dried (MgS04), and evaporated to yield the product. 

Reactive distillation Membrane-based reactive separations Reactive adsorption Reactive absorption Reactive extraction Reactive crystallization... 

The most important examples of reactive separation processes (RSPs) are reactive distillation (RD), reactive absorption (RA), and reactive extraction (RE). In RD, reaction and distillation take place within the same zone of a distillation column. Reactants are converted to products, with simultaneous separation of the products and recycling of unused reactants. The RD process can be efficient in both size and cost of capital equipment and in energy used to achieve a complete conversion of reactants. Since reactor costs are often less than 10% of the capital investment, the combination of a relatively cheap reactor with a distillation column offers great potential for overall savings. Among suitable RD processes are etherifications, nitrations, esterifications, transesterifications, condensations, and alcylations (2). 

This chapter concerns the most important reactive separation processes reactive absorption, reactive distillation, and reactive extraction. These operations combining the separation and reaction steps inside a single column are advantageous as compared to traditional unit operations. The three considered processes are similar and at the same time very different. Therefore, their common modeling basis is discussed and their peculiarities are illustrated with a number of industrially relevant case studies. The theoretical description is supported by the results of laboratory-, pilot-, and industrial-scale experimental investigations. Both steady-state and dynamic issues are treated in addition, the design of column internals is addressed. 

A rather simple and convenient method to separate methyl alcohol and trimethylborate is the extraction technique. Since trimethylborate is highly reactive, its extraction requires well-purified oils, e.g. salve base. Salve base is a highly convenient agent, since it practically does not dissolve methyl alcohol in the presence of trimethylborate the solubility of methyl alcohol increases in proportion to the trimethylborate content. 

James Douglas Let me add two more things. I think reactive crystallization and reactive extraction will become more important in the future, as has reactive distillation. Reactive distillation is receiving a lot of attention at present, but reactive separations should find more applications. 

Solvent extraction is widely used in pharmaceutical and food processing industries. Oil seed extraction, manufacturing of neutraceuticals, decaffeinated coffee, intermediates, and some reactive-separation processes utilize solvent extraction. Hydrocarbons are common solvents for oil seed extraction. Supercritical solvents are gaining popularity in producing neutraceuticals and other active ingredients. 

Pervaporation membrane reactors (PVMR) are an emerging area of membrane-based reactive separations. An excellent review paper of the broader area of pervaporation-based, hybrid processes has been published recently [3.1]. The brief discussion here is an extract of the more comprehensive discussions presented in that paper, as well as in an earlier paper by Zhu et al [3.2]. Mostly non-biological applications are discussed in this chapter. Some pervaporation membrane bioreactor (PVMBR) applications are also discussed additional information on the topic can be found in a recent publication [3.3], and a number of other examples are also discussed in Chapter 4. 

Groot et al [3.86] investigated the technical feasibility of five reactive separation technologies (fermentation coupled to stripping, adsorption, liquid-liquid extraction, pervaporation, and membrane solvent extraction). They concluded that liquid-liquid extraction and pervaporation reactive separation processes show the greatest potential, with PVMBR systems particularly attractive due to their operational simplicity. Membranes utilized include silicone [3.76, 3.77, 3.74, 3.87, 3.75, 3.85, 3.88], supported liquid membrane systems [3.87, 3.89], polypropylene [3.70], and silicalite filled PDMS membranes [3.90, 3.91]. The results with PVMBR systems have been very promising. 

Today, RD is discussed as one part of the broader area of reactive separation, which comprises any combination of chemical reaction with separation such as distillation, stripping, absorption, extraction, adsorption, crystallization, and membrane separation. In the next decade, unifying approaches to reactive separators should be developed allowing the rigorous selection of the most suitable type of separation to be integrated into a chemical reactor. 

Integration of reaction and separation in a single unit is a powerful tool to increase efficiency and economic advantages of many chemical processes. Reactive distillation, extraction, and adsorption are well-known examples of this technological resource. Recently, a very promising solution is offered by membrane reactors... 

Since the different microcomponents react differently, it would be necessary to separate them as several gravity-cut by a flotation technique and establish their reactivity separately. The reactivity of the as-mined coal (composite sample), along with the reactivity of the microcomponents, would be a valuable parameter. A suitable test method would also provide data for yield and composition of gaseous products and minimum hydrogen requirement that has to be fed in the reactor using solvent as a carrier. The spectroscopic characterization of the extractable matter would provide information helpful in downstream processing of the primary liquefaction products. 

For the applications involving multiphase reactions and separations, the mass transfer of a solute from one phase to the other or of a pure phase into another is necessary. The mass transfer rates are different in nonreactive and reactive chemical systems. In nonreactive (separation/extraction) case, the mass is transferred from the phase with higher chemical potential (partial pressure or concentration) to the lower until the equilibrium is reached. In reactive systems, the mass transfer is enhanced because of the consumption of transferring species from one phase to the other. 

For isomer separations, extractive distillation usually fails, since the solvent has the same effect on both isomers. For example, Berg (1969) reported that the best entrainer for separating m- and p-xylene increased the relative volatility from 1.02 to 1.029. An alternative to normal extractive distillation is to use a solvent that preferentially and reversibly reacts with one of the isomers fPoherty and Malone. 20011 The process scheme will be similar to Figure 8-14. with the light isomer being product A and the heavy isomer product B. The forward reaction occurs in the first column, and the reaction product is fed to the second column. The reverse reaction occurs in column 2, and the reactive solvent is recycled to column 1. This procedure is quite similar to the combined reaction-distillation discussed in Section 8.8. 

Chapter 7 will consider separations achieved under the bulk flow-force combination of (b). Separation systems utilizing the configurations of (c) are treated in Chapter 8. (There will be occasional examples of two combinations of bulk flow and force directions.) Chapters 6, 7 and 8 will generally employ one separator vessel. Reactive separations will be treated immediately alongside non-reactive separations as often as possible. Different feed introduction modes will be considered as required in all three configurations, (a), (b) and (c). Multistage separation schemes, widely used in the processes of gas absorption, distillation, solvent extraction, etc., are studied in Chapter 8 when only one vessel is used. When multiple devices are used to form a separation cascade, an introductory treatment is provided in Chapter 9. 

The carbonyl compounds are isolated by separation, extraction, or steam distillation, depending on their nature. They can also be cleaved by expelling the carbonyl compound with a more reactive aldehyde benzal-dehyde is most commonly used, but p-nitrobenzaldehyde, 2,4-dinitroben-zaldehyde, and formaldehyde can be used as well (97 — 99). The expulsion of 2,4-dinitrobenzaldehyde from its hydrazone can be carried out with glyoxal or diacetyl (100). 

Another reactive separation processes studied for ethyl lactate production is the catalytic extractive reaction (Figure 20.4.7). In this case, the esterification is performed in a biphasic liquid solvent system composed by a reactive polar liquid phase which contains the esterification constituents lactic acid, eflianol and catalyst, and an extractive organic solvent selective of the ester. Therefore, ethyl lactate should preferably be dissolved in the extractive organic phase shifting, in this way, the reaction equilibrium to ester formation. The immiscible extractive solvent is an aromatic or other solvent like toluene, benzene or diethyl ether, among others. Nevertheless, it has also been used an immiscible solvent based on fatty acid methyl ester, but in this case, the procedure represents a method to produce an organic biosolvent and not just ethyl lactate as solvent. 

Extraction of C-8 Aromatics. The Japan Gas Chemical Co. developed an extraction process for the separation of -xylene [106-42-3] from its isomers using HF—BF as an extraction solvent and isomerization catalyst (235). The highly reactive solvent imposes its own restrictions but this approach is claimed to be economically superior to mote conventional separation processes (see Xylenes and ethylbenzene). 

Future Trends. In addition to the commercialization of newer extraction/ decantation product/catalyst separations technology, there have been advances in the development of high reactivity 0x0 catalysts for the conversion of low reactivity feedstocks such as internal and a-alkyl substituted a-olefins. These catalysts contain (as ligands) ortho-/-butyl or similarly substituted arylphosphites, which combine high reactivity, vastiy improved hydrolytic stabiUty, and resistance to degradation by product aldehyde, which were deficiencies of eadier, unsubstituted phosphites. Diorganophosphites (28), such as stmcture (6), have enhanced stabiUty over similarly substituted triorganophosphites. 

In the initial thiocyanate-complex Hquid—Hquid extraction process (42,43), the thiocyanate complexes of hafnium and zirconium were extracted with ether from a dilute sulfuric acid solution of zirconium and hafnium to obtain hafnium. This process was modified in 1949—1950 by an Oak Ridge team and is stiH used in the United States. A solution of thiocyanic acid in methyl isobutyl ketone (MIBK) is used to extract hafnium preferentially from a concentrated zirconium—hafnium oxide chloride solution which also contains thiocyanic acid. The separated metals are recovered by precipitation as basic zirconium sulfate and hydrous hafnium oxide, respectively, and calcined to the oxide (44,45). This process is used by Teledyne Wah Chang Albany Corporation and Western Zirconium Division of Westinghouse, and was used by Carbomndum Metals Company, Reactive Metals Inc., AMAX Specialty Metals, Toyo Zirconium in Japan, and Pechiney Ugine Kuhlmann in France. 

Separation and Purification of Isomers. 1-Butene and isobutylene caimot be economically separated into pure components by conventional distHlation because they are close boiling isomers (see Table 1 and Eig. 1). 2-Butene can be separated from the other two isomers by simple distHlation. There are four types of separation methods avaHable (/) selective removal of isobutylene by polymeriza tion and separation of 1-butene (2) use of addition reactions with alcohol, acids, or water to selectively produce pure isobutylene and 1-butene (3) selective extraction of isobutylene with a Hquid solvent, usuaHy an acid and (4) physical separation of isobutylene from 1-butene by absorbents. The first two methods take advantage of the reactivity of isobutylene. Eor example, isobutylene reacts about 1000 times faster than 1-butene. Some 1-butene also reacts and gets separated with isobutylene, but recovery of high purity is possible. The choice of a particular method depends on the product slate requirements of the manufacturer. In any case, 2-butene is first separated from the other two isomers by simple distHlation. 

---