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Water as the Liquid Phase

Typical approaches to this biphasic system have involved the immobilization of catalysts in the aqueous phase as colloids [53] or using water-soluble catalysts based on ligands such as the trisulfonated TPPTS [55, 56]. Particularly high reaction rates have been obtained with surfactant-stabilized microemulsions and emulsions that allow for intimate contact of all reagents with the catalyst during the reaction [57]. The emulsions separate readily into two phases by small pressure changes and the C02-phase is then vented to isolate the products. The catalyst RhCl(tppds)3 (tppds = [Pg.223]

The techniques discussed up to now use C02 as the mobile phase for substrates and products. Naturally, this restricts the applications to relatively non-polar and/or volatile components with sufficient solubility in the supercritical medium. An intriguing alternative for processing highly polar substrates are inverted aqueous systems. In this approach, a C02-philic catalyst resides in the non-polar C02 phase, while water-soluble substrates and products are contained in the aqueous layer [58, 59]. A very attractive and unique feature of the scC02/H20 system is that the stationary supercritical phase is never depressurized and hence the large energy input required for recompression is avoided. Furthermore, the aqueous solution is not contaminated with any organic solvent or catalyst residues, which is particularly important if the product is a fine chemical intended for direct further use in aqueous solution. [Pg.224]


It can be seen that Henry s constants can be dimensionless (Ki, Eqn. 12) expressed in units of pressure, (Ki, Eqn. 2) or take the molaltity format, K (Tables 3 and 4). A similar form of Equation (13) for Ki or K can be simply derived taking due account of units. For example we consider Henry s constant, Ki, expressed in units of atm and water as the liquid phase. In this case the mole fraction, Xi, can be related to the concentrations in terms of the water density, Ph20 (g/cm ) and the water volume, Vh20 (cm ) where... [Pg.549]

Equations have been developed to predict the efficiency of NO2 removal based on experience over many years with ceramic saddle-type packings, NO2 removal efficiency, as defined by Equation 5-14, can be related to the gas retention time (i.e., the depth of the packed bed divided by the superficial gas velocity). Empirically, suitable designs for such scrubbers employing water as the liquid phase are produced using ... [Pg.134]

Figure 3 presents results for acetic acid(1)-water(2) at 1 atm. In this case deviations from ideality are important for the vapor phase as well as the liquid phase. For the vapor phase, calculations are based on the chemical theory of vapor-phase imperfections, as discussed in Chapter 3. Calculated results are in good agreement with similar calculations reported by Lemlich et al. (1957). ... [Pg.91]

Emulsions. Emulsions are formed when one liquid is dispersed as small droplets in another liquid with which the dispersed liquid is immiscible. Mutually immiscible fluids, such as water and oil, can be emulsified by stirring. The suspending liquid is called the continuous phase, and the droplets are called the dispersed (or discontinuous) phase. There are two types of emulsions used in drilling fluids oil-in-water emulsions that have water as the continuous phase and oil as the dispersed phase, and water-in-oil emulsions that have oil as the continuous phase and water as the dispersed phase (invert emulsions). [Pg.651]

To illustrate the application of the proposed algorithm the agrochemicals problem already presented in Chapter 4 of this textbook is revisited. It involves a completely batch operation wherein reusable water is generated from liquid-liquid extraction (product washing) operations with water as the aqueous phase in the production of three agrochemicals A, B and D. The data for the production of these products are shown in Table 5.1. These agrochemicals are produced in batch reactors. All three reactions form sodium chloride (NaCl) as a byproduct which is later removed from... [Pg.112]

Aqueous biphasic catalysis is a special case of the two-phase processes of homogeneous catalysis. Despite the academic literature s provocative question "Why water " [18a, 18b], the advantages of water as the second phase and the "liquid support" are numerous. On the one hand, the search for the necessary solubility gap is much easier with water than with various organic-phase liquids (Figure 5.2). Additionally, water has many properties which predestine it as a ideal liquid support in homogeneous catalysis (see T able 5.1)[18c,18d]. [Pg.108]

The only difference between them is that Reaction (1) involves water in the liquid phase and Reaction (2) involves water as water vapor. Since more heat is released when H20(g) - H20(f), as shown in the adjacent diagram, Reaction (1) is more exothermic than Reaction (2). [Pg.239]

Biphasic systems that contain the catalyst in the supercritical phase and the substrates/products in a second liquid phase can also be implemented. With water as the polar phase, these inverted systems are particularly attractive for the conversion of highly polar and/or low-volatile hydrophilic substrates with limited solubility in typical SCFs such as scC02. [Pg.1364]

Based on the results of these studies it is quite evident that the reaction with ionic liquid as immobilization phase requires a chloride-free catalyst phase in order to achieve any advantage over the reaction with water as the immobilizing phase. [Pg.1399]

IL. Dilute solution viscosity measurements were done at 30 with the appropriate Ostwald-Fenske capillary viscometers. The water content of all organic solvents, used as the liquid phase in solid-liquid PTC runs was analyzed by potentiometric Karl Fischer titration using a Metrohm AG CH 9100 model automatic titrator. [Pg.138]

From experiments, equations have been derived that enable calculation of the minimum velocity in the nozzle, the nozzle velocity, and the Sauter diameter at the drop size minimum. They provide the basis for the correct design of a sieve tray [3,4]. Figure 9.4a shows the geometric design of sieve trays and their arrangement in an extraction column. Let us again consider toluene-phenol-water as the liquid system. The water continuous phase flows across the tray and down to the lower tray through a downcomer. The toluene must coalesce into a continuous layer below each tray and reaches... [Pg.375]

Water was used as the liquid phase. The liquid delivery system consists of a feed tank, pump, and a flow indicator. Water is recycled, as well as added if necessary, to maintain a constant suction head at the pump. The in-house air system was used as the gas delivery system through a rotameter. Air enters the setup at a point below the packing. Two taps are mounted at the inlet and outlet of the packed column for pressure drop measurement. [Pg.61]

The presence of the term y) makes the permeability coefficient a function of the solvent used as the liquid phase. Some experimental data illustrating this effect are shown in Figure 2.7 [11], which is a plot of the product of the progesterone flux and the membrane thickness, 7, against the concentration difference across the membrane, (cio — cif ). From Equation (2.28), the slope of this line is the permeability, P]. Three sets of dialysis permeation experiments are reported, in which the solvent used to dissolve the progesterone is water, silicone oil and poly(ethylene glycol) MW 600 (PEG 600), respectively. The permeability calculated from these plots varies from 9.5 x 10 7 cm2/s for water to 6.5 x 10 10 cm2/s for PEG 600. This difference reflects the activity term yj/ in Equation (2.28). However, when the driving force across the membrane is... [Pg.29]

Choose as standard states for water and ethylene glycol the pure liquids at 1 bar and for ethylene oxide the pure ideal gas at 1 bar. Assume that the Lewis/Randall rule applies to the water in the liquid phase and that the vapor phase is an ideal gas. The partial pressure of ethylene oxide., river the liquid phase is given by, ... [Pg.518]

Procedure (See Chromatography, Appendix IIA.) Use a high-performance liquid chromatograph capable of separating acesulfame potassium and 4-hydroxybenzoic acid ethyl ester with a resolution of 2. Use a chromatograph equipped with a UV or diode array (227 nm) detector and a 25-cm x 4.6-mm (id) stainless steel column, or equivalent, packed with 3 to 5 p,m of reversed phase C18 silica gel, or equivalent. The elution is isocratic. Use a 40 60 (v/v) solution of acetoni-trile 0.01 MlL tetrabutyl ammonium hydrogen sulfate (TBAHS) in water as the mobile phase, with a flow rate of about 1 mL/min. [Pg.10]

Chromatographic System Determine as directed under Chromatography, Appendix HA, but use a liquid chromatograph equipped with a differential refractometer detector and a 30-cm x 7.8-mm (id) column packed with 25-pm diameter beads of silver bonded to sulfonated divinyl benzene-styrene copolymer (Aminex HPX-42A, Bio-Rad Laboratories, or equivalent). Maintain the column at a constant temperature of 65° 10°, and the flow rate at 0.3 to 1.0 mL/min. Use deionized water as the mobile phase. [Pg.129]

Alternatively, polar liquids other than water can be used to generate supported liquid-phase catalysts with sulfonated ligands. For example, supported liquid-phase Pd-TPPTS catalysts have been prepared on silica with ethylene glycol as the liquid phase. " ... [Pg.4723]

We conclude this section by giving a topical example of the utility of conditional averages in considering molecularly complex systems (Ashbaugh et al, 2004). We considered the RPLC system discussed above (p. 5), but without methanol n-Ci8 alkyl chains, tethered to a planar support, with water as the mobile phase. The backside of the liquid water phase contacts a dilute water vapor truncated by a repulsive wall see Fig. 1.2, p. 7. Thus, it is appropriate to characterize the system as consistent with aqueous liquid-vapor coexistence at low pressure. A standard CHARMM force-field model (MacKerell Jr. et al, 1998) is used, as are standard molecular dynamics procedures - including periodic boimdary conditions - to acquire the data considered here. Our interest is in the interface between the stationary alkyl and the mobile liquid water phases at 300 K. [Pg.19]

In a pioneering investigation, Serizawa [127, 128] measured the lateral void distribution as well as the turbulent axial liquid velocity fluctuations for bubbly air/water up-flows in a vertical pipe of diameter 60 (mm) inner diameter. They used electrical resistivity probes to measure the local void fraction, the bubble impaction rate, the bubble velocity and its spectrum. Turbulence quantities, such as the liquid phase mean velocity, and the axial turbulent fluctuations were measured using a hotfilm anemometer. A supplementary... [Pg.760]

The balance contains just two adjustable hydrodynamic parameters, tl l and PeL. The Peclet number is estimated from the separate impulse experiments carried out with the inert tracer (NaCl), while the quantity Tl l is estimated from the kinetic experiments in order to ensure a correct description of the reactor dynamics. The flow pattern of the reactor is characterised by separate impulse experiments with an inert tracer component injecting the tracer at the reactor inlet and measuring in this case the conductivity response at the outlet of the reactor with a conductivity cell operated at atmospheric pressure. In order to get a proper conductivity response, water was employed as the liquid phase. The liquid and hydrogen flow rates should be the same as in the hydrogenation experiments and the liquid hold up was evaluated by weighing the reactor. Some results from the tracer experiments are given in Figure 8.12. [Pg.301]


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