Complex distillation processes solvents

CAA [Cuprous ammonium acetate] A general process for separating alkenes, di-alkenes, and alkynes from each other by extraction of their cuprous complexes from aqueous cuprous ammonium acetate into an organic solvent. Exxon used it for separating C4 fractions containing low concentrations of butadiene. The liquid-liquid extraction processes for butadiene have all been replaced by extractive distillation processes. 

In [1677] complex alkoxides and alkoxide-carboxylates were compared as precursors for preparation ofBST films. In contrast to the introduction of alkaline earth carboxylates in the form of preliminary isolated salts, in this work metal alkoxide solution in methoxyethanol containing titanium and alkaline-earth metal was modified by addition of 2-ethylhexanoic acid with subsequent slow distilling off the solvent and repeated dilutions with fresh portions of methoxyethanol. During the distillation process, part of the alkoxide groups are substituted by the 2-ethylhexanoate ligands. The exchange reaction of Ti(OPr )4 with acid was studied in different solvents, and it was demonstrated that in the course of distillation the titanium oxoisopropoxy-2-ethylhexanoate is formed with elimination of ester ... 

An xs of BClj is distilled into the LiAlH in (CjHj) at — 196"C. The mixture is wanned to 25°C and thoroughly mixed, the B H distills through a trap maintained at — 112 C and the xs BClj forms a complex with the solvent. Because LiAlH, may be prepared simply from LiH and AlClj, the process may be considered as a synthesis from LiH and BClj with AICI3 present as a solubilizing agent for LiH. 

Many separations which would be difficult to achieve by conventional distillation processes may be effected by a distillation process in which a solvent is introduced which reacts chemically with one or more of the components to be separated. Three methods are presented for solving problems of this type. In Sec. 8-1, the 0 method of convergence is applied to conventional and complex distillation columns. In Sec. 8-2, the 2N Newton-Raphson method is applied to absorbers and distillation columns in which one or more chemical reactions occur per stage. The first two methods are recommended for mixtures which do not deviate too widely from ideal solutions. For mixtures which form highly nonideal solutions and one or more chemical reactions occur per stage, a formulation of the Almost Band Algorithm such as the one presented in Sec. 8-3 is recommended. 

Outadiene is one of the most valuable chemicals produced in the mod-em chemical refining complex. The pure monomer is recovered from crude C4 streams by liquid-liquid extraction or extractive distillation with a selective solvent. A simplified diagram of an extractive distillation process is shown in Figure 1. The C4 feed is separated into two product streams in the extractive distillation column—a butane-butene stream which goes overhead from the column and a butadiene concentrate which is carried out the bottom of the column dissolved in the solvent. The butadiene concentrate contains cis- and trans-2-butene, and after being stripped from the solvent, it is subjected to normal distillation. Butadiene is distilled overhead at 99+% purity. 

The biological activity of molecules such as proteins, cells, and viruses can easily be destroyed by processing conditions that do not conform to their natural environment. Therefore, traditional separation processes such as distillation or solvent extraction are seldom used to isolate them. Affinity adsorption is one of the most effective methods for the direct isolation and purification of biomolecules from complex mixtures (Camperi et al., 2003). It is based on recognition between a pair of molecules determined by the steric structure (three-dimensional arrangement of its atoms) of the molecules. When molecules have complementary steric structures, they can interact to maximize the hydrogen bonds and electrostatic interactions. Affinity adsorption allows a separation with high specificity and purity. 

These experiments suggest (1) metallic materials are found in process solvents, (2) metals are organically bound since they have survived both distillation and chromatographic separation and (3) a large number of different molecular sized species co-exist. The exact nature of these metal components remains a mystery primarily because (1) the separation behavior of metal complexes via size... 

During extraction the feed is polluted with traces of the solvent since there always exists some mutual solubihty of the two phases (i.e., rafifinate and extract). This fact requires a further separation process for solvent recovery, making extraction processes more complex than, for instance, distillation processes. 

It is quite common in the chemical process industry to use various kinds of salts to dehydrate complex mixtures of solvents to avoid azeotropic distillation. These salts can cause many serious problems in the whole process. They can also cause a msting problem in the whole piping system. The disposal of such toxic wastewater is a colossal issue for the chemical industry. The AZEO SEP pervaporation hybrid system can eliminate the use of salt, and it can breakdown the azeotropes for further process or use. 

Although Pd is cheaper than Rh and Pt, it is still expensive. In Pd(0)- or Pd(ll)-catalyzed reactions, particularly in commercial processes, repeated use of Pd catalysts is required. When the products are low-boiling, they can be separated from the catalyst by distillation. The Wacker process for the production of acetaldehyde is an example. For less volatile products, there are several approaches to the economical uses of Pd catalysts. As one method, an alkyldi-phenylphosphine 9, in which the alkyl group is a polyethylene chain, is prepared as shown. The Pd complex of this phosphine has low solubility in some organic solvents such as toluene at room temperature, and is soluble at higher temperature[28]. Pd(0)-catalyzed reactions such as an allylation reaction of nucleophiles using this complex as a catalyst proceed smoothly at higher temperatures. After the reaction, the Pd complex precipitates and is recovered when the reaction mixture is cooled. 

Butadiene Separation. Solvent extraction is used in the separation of butadiene (qv) [106-99-0] from other C-4 hydrocarbons in the manufacture of synthetic mbber. The butadiene is produced by catalytic dehydrogenation of butylene and the Hquid product is then extracted using an aqueous cuprammonium acetate solution with which the butadiene reacts to form a complex. Butadiene is then recovered by stripping from the extract. Distillation is a competing process. 

Economic considerations in the 1990s favor recovering butadiene from by-products in the manufacture of ethylene. Butadiene is a by-product in the C4 streams from the cracking process. Depending on the feedstocks used in the production of ethylene, the yield of butadiene varies. Eor use in polymerization, the butadiene must be purified to 994-%. Cmde butadiene is separated from C and C components by distillation. Separation of butadiene from other C constituents is accomplished by salt complexing/solvent extraction. Among the solvents used commercially are acetonitrile, dimethyl acetamide, dimethylform amide, and /V-methylpyrrolidinone (13). Based on the available cmde C streams, the worldwide forecasted production is as follows 1995, 6,712,000 1996, 6,939,000 1997, 7,166,000 and 1998, 7,483,000 metric tons (14). As of January 1996, the 1995 actual total was 6,637,000 t. 

The clay-cataly2ed iatermolecular condensation of oleic and/or linoleic acid mixtures on a commercial scale produces approximately a 60 40 mixture of dimer acids and higher polycarboxyUc acids) and monomer acids (C g isomerized fatty acids). The polycarboxyUc acid and monomer fractions are usually separated by wiped-film evaporation. The monomer fraction, after hydrogenation, can be fed to a solvent separative process that produces commercial isostearic acid, a complex mixture of saturated fatty acids that is Hquid at 10°C. Dimer acids can be further separated, also by wiped-film evaporation, iato distilled dimer acids and trimer acids. A review of dimerization gives a comprehensive discussion of the subject (10). 

As mentioned earlier, a major cause of high costs in fine chemicals manufacturing is the complexity of the processes. Hence, the key to more economical processes is reduction of the number of unit operations by judicious process integration. This pertains to the successful integration of, for example, chemical and biocatalytic steps, or of reaction steps with (catalyst) separations. A recurring problem in the batch-wise production of fine chemicals is the (perceived) necessity for solvent switches from one reaction step to another or from the reaction to the product separation. Process simplification, e.g. by integration of reaction and separation steps into a single unit operation, will provide obvious economic and environmental benefits. Examples include catalytic distillation, and the use of (catalytic) membranes to facilitate separation of products from catalysts. 

The linear telomerization reaction of dienes was one of the very first processes catalyzed by water soluble phosphine complexes in aqueous media [7,8]. The reaction itself is the dimerization of a diene coupled with a simultaneous nucleophilic addition of HX (water, alcohols, amines, carboxylic acids, active methylene compounds, etc.) (Scheme 7.3). It is catalyzed by nickel- and palladium complexes of which palladium catalysts are substantially more active. In organic solutions [Pd(OAc)2] + PPhs gives the simplest catalyst combination and Ni/IPPTS and Pd/TPPTS were suggested for mnning the telomerizations in aqueous/organic biphasic systems [7]. An aqueous solvent would seem a straightforward choice for telomerization of dienes with water (the so-called hydrodimerization). In fact, the possibility of separation of the products and the catalyst without a need for distillation is a more important reason in this case, too. 

The lack of satisfactory solvent recovery methods prior to 1930 prevented the use of selective solvents more suitable for lubricating oils. The major part of any solvent extraction plant is its complex solvent recovery system. Chemical engineering s contributions to distillation theory and process design resulted in the development of efficient solvent recovery techniques. In 1933, as illustrated by Figure 3, large commercial plants were... 

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