Hydration process

Below 0.07 h thermodynamic and IR spectroscopic measurements have shown that water adsorbed to the protein is localized at charged 

At the 0.07 h discontinuity, the heat capacity function shifts from generally downward-trending to strongly upward-trending. This is expected for a two-dimensional condensation process—here, the formation of mobile water clusters from dispersed water associated with ionizable protein surface groups. This transition in the surface water is seen also in the IR spectroscopic properties (Fig. 38) and other proper- 

At the 0.25 h discontinuity, condensation of water over the weakest interacting regions of the surface begins and proceeds until completion of the hydration shell at 0.38 h. This event is a typical condensation. It occurs within a narrow range of water activity, near unity, and is associated with addition to the surface of about one-third of the total hydration shell. 

38 h discontinuity corresponds to the hydration end point, above which the nonideality per mol of protein is constant. The heat capacity measurements define the hydration end point tightly. These measurements are sensitive to the interactions of water with both hydrogen-bonding and nonpolar protein surface groups and should reflect essentially all time-average chemistry associated with hydration. 

The above picture should be general. As noted, globular proteins are closely similar in their sorption isotherms, and heat capacity measurements in the water-poor region, for several proteins, are consistent with the data of Fig. 38. 

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From Acetylene. Although acetaldehyde has been produced commercially by the hydration of acetylene since 1916, this procedure has been almost completely replaced by the direct oxidation of ethylene. In the hydration process, high purity acetylene under a pressure of 103.4 kPa (15 psi) is passed into a vertical reactor containing a mercury catalyst dissolved in 18—25% sulfuric acid at 70—90°C (see Acetylene-DERIVED chemicals). 

The manufacture of cryoHte is commonly iategrated with the production of alumina hydrate and aluminum trifluoride. The iatermediate stream of sodium aluminate from the Bayer alumina hydrate process can be used along with aqueous hydrofluoric acid, hydrogen fluoride kiln gases, or hydrogen fluoride-rich effluent from dry-process aluminum trifluoride manufacture. 

E. Matsunaga and R. G. Muller, Secondary Butyl Mlcohol via Direct Hydration, Process Economics Program, Review No. 84-2-2, SRI International, Menlo Park, Calif., Aug. 1985. 

The indirect hydration, also called the sulfuric acid process, practiced by the three U.S. domestic producers, was the only process used worldwide until ICI started up the first commercial direct hydration process in 1951. Both processes use propylene and water as raw materials. Early problems of high corrosion, high energy costs, and air pollution using the indirect process led to the development of the direct hydration process in Europe. However, a high purity propylene feedstock is required. In the indirect hydration process, C -feedstock streams from refinery off-gases containing only 40—60 wt % propylene are often used in the United States. 

Process. A typical indirect hydration process is presented in Eigure 1. In the process, propylene reacts with sulfuric acid (>60 wt%) in agitated reactors or absorbers at moderate (0.7—2.8 MPa (100—400 psig)) pressure. The isopropyl sulfate esters form and are maintained in the Hquid state at 20—80°C. Low propylene concentrations, ie, 50 wt %, can be tolerated, but concentrations of 65 wt % or higher are preferred to achieve high alcohol yields. Because the reaction is exothermic, internal cooling coils or external heat exchangers are used to control the temperature. 

Fig. 1. Indirect hydration process for the manufacture of isopropyl alcohol CBM = constant boiling mixture (61,62).

Fig. 3. Direct hydration process where the product is isolated as diisopropyl ether.

Butanol is produced commercially by the indirect hydration of / -butenes. However, current trends are towards the employment of inexpensive Raffinate 11 type feedstocks, ie, C-4 refinery streams containing predominandy / -butenes and saturated C-4s after removal of butadiene and isobutylene. In the traditional indirect hydration process, / -butenes are esterified with Hquid sulfuric acid and the intermediate butyl sulfate esters hydroly2ed. DEA Mineraloel (formerly Deutsche Texaco) currentiy operates a 2-butanol plant employing a direct hydration of / -butenes route (18) with their own proprietary catalyst. 

There are two main processes for the synthesis of ethyl alcohol from ethylene. The eadiest to be developed (in 1930 by Union Carbide Corp.) was the indirect hydration process, variously called the strong sulfuric acid—ethylene process, the ethyl sulfate process, the esterification—hydrolysis process, or the sulfation—hydrolysis process. This process is stiU in use in Russia. The other synthesis process, designed to eliminate the use of sulfuric acid and which, since the early 1970s, has completely supplanted the old sulfuric acid process in the United States, is the direct hydration process. This process, the catalytic vapor-phase hydration of ethylene, is now practiced by only three U.S. companies Union Carbide Corp. (UCC), Quantum Chemical Corp., and Eastman Chemical Co. (a Division of Eastman Kodak Co.). UCC imports cmde industrial ethanol, CIE, from SADAF (the joint venture of SABIC and Pecten [Shell]) in Saudi Arabia, and refines it to industrial grade. 

Other Methods of Preparation. In addition to the direct hydration process, the sulfuric acid process, and fermentation routes to manufacture ethanol, several other processes have been suggested. These include the hydration of ethylene by dilute acids, the hydrolysis of ethyl esters other than sulfates, the hydrogenation of acetaldehyde, and the use of synthesis gas. None of these methods has been successfilUy implemented on a commercial scale, but the route from synthesis gas has received a great deal of attention since the 1974 oil embargo. 

It has to be remembered that hydration processes and moisture exchange occur with old concrete when sprayed concrete is applied. Both processes can affect the potentials so that the protection current should only be switched on 4 weeks after... 

DJ Tobias. Water and membranes Molecular details from MD simulations. In M-C Bellissent-Eunel, ed. Hydration Processes in Biology Theoretical and Experimental Approaches. Amsterdam lOS Press, 1999, pp 293-310. 

Strong acids also catalyze the addition of alcohols to alkenes to give ethers, and the mechanistic studies which have been done indicate that the reaction closely parallels the hydration process. ... 

Subsequent investigations proved that identical hydration reactions occur on bare aluminum surfaces and bonded surfaces, but at very different rates of hydration [49]. An Arrhenius plot of incubation times prior to hydration of bare and buried FPL surfaces clearly showed that the hydration process exhibits the same energy of activation ( 82 kJ/mole) regardless of the bare or covered nature of the surface (Fig. 11). On the other hand, the rate of hydration varies dramatically, de-... 

Extensive drying or dewatering of the waste is not required because cement mixtures require water in the hydration process, and thus the amount of cement added can be adjusted to accommodate a wide range of waste water contents. 

L. Paz, J. M. Di Meglio, M. Dvolaitzky, R. Ober, C. Taupin. Highly curved defects in lyotropic (nonionic) lamellar phases. Origin and role in hydration processes. J Phys Chem 55 3415-3418, 1984. 

In the liquid-phase process, high pressures in the range of 80-100 atmospheres are used. A sulfonated polystyrene cation exchange resin is the catalyst commonly used at about 150°C. An isopropanol yield of 93.5% can be realized at 75% propylene conversion. The only important byproduct is diisopropyl ether (about 5%). Figure 8-4 is a flow diagram of the propylene hydration process. ... 

On the left, the divalent metal ion is spherical with a J-electron configuration which is amply described as d". On the right, the metal is engaged in six octahedrally disposed bonds and its J-electron configuration is best recorded as The electronic contributions to the hydration process refer, as usual, to the formation of the bonds and the attraction of electrons to the central metal, to the... 

Within the hydration process in Eqn. (8.8), a spherical ion becomes a (hydrated) octahedral ion, [M(H20)6]. Part of the Coulomb energy of the free ion concerns repulsion and exchange terms within the d" configuration. This is replaced by equivalent repulsion and exchange terms within the configuration. Let us estimate the trends in these quantities separately. 

Within the first-order estimations made here, it is apparent that no change in d-d repulsion energy accompanies the hydration process. Second-order adjustments would, of course, take account of the change in mean i/-orbital radius on complex formation. Let us agree to stop at the simple level of correction here. Overall, therefore, the significant Coulombic change on hydration concerns the loss of exchange stabilization. 

Diamond [38] has shown that considerable amounts of lithium become bound during the hydration process. A study of the influence of hydration on the observable lithium content in cement paste samples was undertaken. In parallel, a traditional approach to lithium content in the pore solution was conducted (physical extraction of the pore solution and subsequent chemical analysis). The relationship between pore solution extraction and bulk MR is shown to be linear (see Figure 3.4.15). This result indicates that MR will be able to image lithium held in the pore solution but not lithium bound to the cement paste matrix. MR and pore solution extraction results also confirm that large amounts of lithium become bound during hydration. 

The rate at which the hydration process proceeds, that is, the amount by which the layer grows in thickness per unit time (e.g., per year), is deter-... 

Ericson, J. E., J. D. McKenzie, and R. Berger (1976), Physics and chemistry of the hydration process in obsidian, in Taylor, R. E. (ed.), Advances in the Study of Obsidian Glass Studies, Noyes, Park Ridge, pp. 46-62. 

Penetration of dimethyl phosphite into the fibre, accompanied by decomposition of salt linkages and elimination of structural water in a multi-step hydration process. New salt linkages are formed between cationic groups in wool keratin and anionic dimethyl phosphite. 

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