Water-promoted processes

Fringuelli, R, Pizzo, R and Vaccaro, L., Azidolysis of a,/i-epoxycarboxylic acids. A water-promoted process efficiently catalyzed by indium trichloride at pH 4.0, /. Org. Chem., 2001, 66, 3554-3558. 

Li demonstrated the water-promoted CDC reaction between indoles and benzoquinones without any catalyst, organic solvent, or additives (Scheme 8.72). This water-promoted process enables a highly efficient and direct transformation to mono- and bis(indolyl)benzoquinones (148 and 149). 

Separation of two liquid phases, immiscible or partially miscible liquids, is a common requirement in the process industries. For example, in the unit operation of liquid-liquid extraction the liquid contacting step must be followed by a separation stage (Chapter 11, Section 11.16). It is also frequently necessary to separate small quantities of entrained water from process streams. The simplest form of equipment used to separate liquid phases is the gravity settling tank, the decanter. Various proprietary equipment is also used to promote coalescence and improve separation in difficult systems, or where emulsions are likely to form. Centrifugal separators are also used. 

One approach which enables lower water concentrations to be used for rhodium-catalysed methanol carbonylation is the addition of iodide salts, especially lithium iodide, as exemplified by the Hoechst-Celanese Acid Optimisation (AO) technology [30]. Iodide salt promoters allow carbonylation rates to be achieved at low (< 4 M) [H2O] that are comparable with those in the conventional Monsanto process (where [H20] > 10 M) while maintaining catalyst stability. In the absence of an iodide salt promoter, lowering the water concentration would result in a decrease in the proportion of Rh existing as [Rh(CO)2l2] . However, in the iodide-promoted process, a higher concentration of methyl acetate is also employed, which reacts with the other components as shown in Eqs. 3, 7 and 8 ... 

Currently, the most important application area for membrane distillation is water desalination technology. Figure 10 shows one of the water desalination processes developed by a Japanese organization, the Water Re-Use Promotion Center, in cooperation with Takenaka Corporation and Organo Corporation (204). The process uses solar energy and can therefore be installed at locations without an electricity supply. Other application areas for membrane distillation reported in the literature are summarized in Table 8. 

Another, less well-documented occurrence of celadonite is the subaerial alteration of basic and basaltic rocks. Here interaction of surface waters promotes the formation of celadonite, a similar process to that of hydrothermal alteration but at a lower temperature. In both cases there is significant oxidation of the initial iron-bearing rocks. This is reflected in the high ferric iron content of the celadonite minerals. 

Mobilization of sedimentary phosphorus by microbial activity during diagenesis causes dissolved phosphate buildup in sediment pore waters, promoting benthic efflux of phosphate to bottom waters or incorporation in secondary authigenic minerals. The combined benthic flux from coastal (sFcbf) and abyssal (sFabf) sediments is estimated to exceed the total riverine-P flux (F24(d+p>) to the ocean. Reprecipitation of diagenetically mobilized phosphorus in secondary phases significantly enhances phosphorus burial efficiency, impeding return of phosphate to the water column (see Section 8.13.3.3.2). Both processes impact the... 

In 1996 BP announced the commercialization of their version of a low-water methanol carbonylation technology named Cativa based upon a promoted iridium catalyst. The Cativa process replaced the high-water Monsanto process which had been used by BP. 

The mechanism of the Nef reaction has been extensively studied. Under the original reaction conditions, the nitronate salt is first protonated to give the nitronic acid, which after further protonation is attacked by a molecule of water. The process is strongly dependent on the pH of the reaction medium. Weakly acidic conditions favor the regeneration of the nitro compound and by-product formation (oximes and hydroxynitroso compounds), whereas strongly acidic medium (pH 1) promotes the formation of the carbonyl compound. The most popular reductive method (TiCb) proceeds via a nitroso compound that tautomerizes to form an oxime and finally upon work-up the desired product is obtained. 

Friedel-Crafts alkylation reactions are, in general, accompanied by isomerization processes. Olah et a/. reported the results of the water-promoted, AlCb-catalyzed isomerization of o-, m- and p-di-f-bu-tylbenzene. No ortho isomer was present in the equilibrium mixture. The isomerization of o-di-r-bu-tylbenzene was very rapid largely due to relief of steric strain. In these and other related sterically hindered arenes, intramolecular isomerization and not dealkylation was observed. Isomerization of di-and mono-methylnaphthalenes, catalyzed by HF-BF3, was also reported. Isomerization of /i-alkyl-toluenes and -xylenes, catalyzed by AICI3 at room temperature, afforded chiefly /n-/i-alkyltoluenes and /n-/i-alkylxylenes, respectively. The process leading to the meta isomer has a lower energy than the other processes. 

It helps to regulate body temperature, irrigates the cells and organs, and is an almost universal solvent. Water promotes all the functions of elimination. Nerves must be bathed in moisture. Without adequate water content, the blood cannot flow, waste matter won t be eliminated from the body, and many chemical processes will be disrupted. But an excess of water in the body causes pressure on and enlargement of all organs. 

Lowering the water concentration would normally result in a decrease in the proportion of rhodium existing as [Rh(CO)2I2]. However, the lithium iodide-promoted process also employs a higher concentration of methyl acetate, which reacts with the other components as shown in Equations (8) and (9). Thus, raising the methyl acetate concentration results in a lower HI concentration, which tends to inhibit oxidation of [Rh(CO)2I2] to give [Rh(CO)2I4], thus suppressing the WGS reaction significantly, which is beneficial for catalytic carbonylation activity. 

When oxygen or air are used as gasification agents, their content in the reaction medium must be kept low in order to avoid complete oxidation into carbon dioxide and water. The process can be promoted by metal catalysts, usually added to the raw material in aqueous solutions. 

In recent years the Asahi Corporation has developed a benzene-to-cyclohexene process involving a liquid-liquid two-phase system (benzene-water) with a solid ruthenium catalyst dispersed in the aqueous phase. The low solubility of cyclohexene in water promotes rapid transfer towards the organic phase. An 80000 t annum plant using this process is in operation. Another way to scavenge the intermediate cyclohexene is to support the metal hydrogenation catalyst on an acidic carrier (e. g. silica-alumina). On such a bifunctional catalyst the cyclohexene enters catalytic alkylation of the benzene (present in excess) to yield cyclohexylbenzene [19], which can be converted, by oxidation and rearrangement reactions, into phenol and cyclohexanone. 

We will consider in this chapter the sources of freshwater supply in the Asian region and the main sources of water pollution, principal water chemical processes and accumulation of differentpollutants in surface and ground waters with degradation of water quality. Finally, we review briefly the policies and programs that have been undertaken in the region to promote sustainable development of water resources at national and international levels. 

For the purpose of a stable, long-term energy security, promoting industries, and development of local areas, Japan is currently investigating the potential of light-water reactor process heat applications. The chemical industries in Japan occupy a share of about one sixth of the electricity which is mostly consumed in the form of heat. Designs have been presented to utilize steam from 1100 MW(e) class PWRs or BWRs. 

---