Pressure of Pure ILs

Based on the experience obtained up to now [25-27, 32], the following strategy is proposed to determine the vapor pressure and the rate constant of thermal decomposition of ILs  

1) At first, ambient pressure TG experiments with two different inert gases should be performed. In this work, N2 and He were used, because the diffusion coefficients differ by a factor of 2.5. 

2) If the rates of mass loss in N2 and He are equal, only decomposition takes place, and the respective kinetic parameters E ) are yielded by fitting of the TG experiments. 

4) If even at the lowest heating rate only decomposition occurs (no change of TG signal if different carrier gases are used), the vapor pressure caimot be determined by ambient pressure TGA, and complimentary HV effusion 

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For ILs with a low stability regarding thermal decomposition and/or relatively low vapor pressures, HV experiments (<10 Pa) should be conducted, for example, with a magnetic suspension balance (MSB y)- The schematic setup of these two methods used in this work to evaluate the thermal stability and vapor pressure of pure and supported ILs are shown in Figure 6.2. For details see [25-27, 32]. 

Vapor Pressure Data and Kinetic Parameters of Decomposition of Pure ILs... 

While this technique can be used for gas solubility in volatile liquids, where the vapor pressure of the liquid is determined prior to the introduction of the gas, it is uniquely suited for fhe measurement of gas solubilities in ILs because the gas phase remains pure. This is the technique used by Costa Gomez and coworkers [8-10] to measure the solubility of various gases in ILs and a schematic of the apparatus is shown in Figure 8.3. These apparatuses are frequently made entirely from glass and, therefore, are limited to low-pressure operation. Nonetheless, this makes them ideal for determining Henry s law constants. 

After completion of the reaction the NO F is purified fractional distillation in a quartz column at a pressure of 100 mm. The fraction boilii at —79°C (99 mm.) is pure NO3F. The first cut consists of SiF the residue, chiefly of IL,SiFe and HF. 

The use of ionic hquids (ILs) or eutectic mixtures as solvent in zeolite synthesis has been reported [178]. The IL, viz. l-methyl-3-ethylimidazolium bromide, was used both as solvent and as SDA. It solubilizes all components involved in the synthesis, while the electrostatic interaction between cations, IL and framework species form the basis of a strong templating effect [165, 178]. It was shown that the IL also works as a microwave absorber [172] and is suited for microwave-assisted zeolite synthesis. Because of the low vapor pressure of IL, the synthesis occurs at low pressure. The addition of amines to such synthesis mixtures yields pure API and ATV structures. The amine as well as the IL seem to exert a structure-directing effect [179]. This method is particularly useful for preparation of transition-metal functionalized frameworks, viz. Co-AlP04-n [180]. New zeotypes were obtained in the Al, P system, viz. SIZ-7, as well as in the Si system, viz. SIZ-12. 

For the development and design of supported ionic liquid (IL) processes - but also of those utilizing pure ILs, for example, as solvents-the thermophysical properties such as density, heat capacity, thermal conductivity, viscosity, melting point, solvation properties, mass transport properties in/of ILs, thermal stability, and vapor pressure are important [1-24]. Here, the emphasis is on the three last-mentioned properties. 

The vapor pressure of ILs supported on a porous soHd may be lower than the saturation vapor pressure of a pure IL, as known from multilayer ad/desorption of gases. 

The sorption of SO2 in pure IL and IL-coated SILP was investigated at 20 °C and ambient pressure, as shown in Figure 21.4. 

To form a Langmuir monolayer, the molecule of interest is dissolved in a volatile organic solvent (frequently chloroform or hexane) that will not react with or dissolve in the subphase (1,2,4). A quantity of this solution is placed on the surface of the subphase, and as the solvent evaporates, the siuTactant molecules spread and alter the surface pressure of the water surface. A barrier designed to measure this surface pressure (D), relative to that of the pin-e subphase, is the principle behind the Langmuir balance. Alternatively, the siuTace pressure is measured as the difference between the surface tension (y) of the monolayer and that of the pure subphase iyo), n = yo — K- A common method for measining surface tension involves using a Wilhelmy plate, usually a piece of platimun or paper that is wetted by the subphase, suspended from a balance. As the monolayer is compressed by using the moveable barrier to reduce the sinface area, the surface pressure increases. A plot of the siuTace pressin-e versus surface area is called a pressure versus area isotherm (or Il-A isotherm). Isotherms are normally plotted in terms of area/molecule, and the imits of surface pressure are mN/m. 

Several studies have been reported in the hterature about the viscosity behavior of methylimidazolium, pyridiniurn and pyrrolidinium as pure ILs or in binary mixture using water or organic solvents (IL + water or IL + organic solvent) at different temperatures and pressure values. [109]... 

Friifltion 1, ar attno ipheric pressure, boiled al 175 to 176° and yielded with bromine a letraliromide meltinj al 125 . Il coosieled of alrnosl pure dipeuseue. 

One of the most important characteristics of IL is its wide temperature range for the liquid phase with no vapor pressure, so next we tested the lipase-catalyzed reaction under reduced pressure. It is known that usual methyl esters are not suitable for lipase-catalyzed transesterification as acyl donors because reverse reaction with produced methanol takes place. However, we can avoid such difficulty when the reaction is carried out under reduced pressure even if methyl esters are used as the acyl donor, because the produced methanol is removed immediately from the reaction mixture and thus the reaction equilibrium goes through to produce the desired product. To realize this idea, proper choice of the acyl donor ester was very important. The desired reaction was accomplished using methyl phenylth-ioacetate as acyl donor. Various methyl esters can also be used as acyl donor for these reactions methyl nonanoate was also recommended and efficient optical resolution was accomplished. Using our system, we demonstrated the completely recyclable use of lipase. The transesterification took place smoothly under reduced pressure at 10 Torr at 40°C when 0.5 equivalent of methyl phenylthioacetate was used as acyl donor, and we were able to obtain this compound in optically pure form. Five repetitions of this process showed no drop in the reaction rate (Fig. 4). Recently Kato reported nice additional examples of lipase-catalyzed reaction based on the same idea that CAL-B-catalyzed esterification or amidation of carboxylic acid was accomplished under reduced pressure conditions. ... 

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