Nonaqueous absorption systems

Recovery and Purification. AH processes for the recovery and refining of maleic anhydride must deal with the efficient separation of maleic anhydride from the large amount of water produced in the reaction process. Recovery systems can be separated into two general categories aqueous- and nonaqueous-based absorption systems. Solvent-based systems have a higher recovery of maleic anhydride and are more energy efficient than water-based systems. 

D. A. Paterson, R. A. Conradi, A. R. HUgers, et al. A nonaqueous partitioning system for predicting the oral absorption potential of peptides. Quantitative Structure-Action Relationships, 13, 4-10 (1994)... 

Merocyanine Dye Method for Acid Analysis. Resist photochemistry can often be monitored by the changes in ultraviolet absorption spectra associated with a bleaching of the sensitizer absorbance. In the case of resist systems with triphenylsulfonium salts, no change in the film absorption is observed on irradiation. In order to determine the amount of acid produced, a direct method for acid analysis was required. A highly sensitive method was desirable since the amount of acid produced is approximately 10 6 mmol for a 1 micrometer thick film on a 2 inch wafer. Furthermore a nonaqueous technique is preferred in order to avoid hydrolysis of the hexafiuoroantimonate salt. Hydrolysis gives hydrogen fluoride (14) which makes accurate acid determination more difficult. 

FTIR is a natural for HPLC in that it (FTIR) is a technique that has been used mostly for liquids. The speed introduced by the Fourier transform technique allows, as was mentioned for GC, the recording of the complete IR spectrum of mixture components as they elute, thus allowing the IR photograph to be taken and interpreted for qualitative analysis. Of course, the mobile phase and its accompanying absorptions are ever present in such a technique and water must be absent if the NaCl windows are used, but IR holds great potential, at least for nonaqueous systems, as a detector for HPLC in the future. 

Most of the above membrane-oriented studies were carried out for peptides in multilayer systems that were collapsed or transferred onto a sample cell surface. An alternative and very interesting way to study membrane systems is by IRRAS (infrared reflection absorption spectroscopy) at the air-water interface. In this way, unilamellar systems can be studied as a function of surface pressure and under the influence of various membrane proteins and peptides added. Mendelsohn et al.[136] have studied a model series of peptides, [K2(LA) ] (n = 6, 8, 10, 12), in nonaqueous (solution), multilamellar (lipid), and unilamellar (peptide-IRRAS) conditions. In the multilamellar vesicles these peptides are predominantly helical in conformation, but as peptide only monolayers on a D20 subphase the conformation is (1-sheet like, at least initially. For different lengths, the peptides show variable surface pressure sensitivity to development of some helical component. These authors further use their IR data to hypothesize the existence of the less-usual parallel (i-sheet conformation in these peptides. A critical comparison is available for different secondary structures as detected using the IRRAS data for peptides on H20 and D20 subphasesJ137 ... 

The recovery area uses a patented organic solvent to remove the maleic anhydride from the reactor effluent gas. Aconventional absorption (2)/stripping (3) scheme operates on a continuous basis. Crude maleic anhydride is distilled to separate light (4) and heavy (5) impurities. A slipstream of recycle solvent is treated to eliminate any heavy byproducts that may be formed. The continuous nonaqueous product recovery system results in superior product quality and large savings in steam consumption. It also reduces investment, product degradation loss (and byproduct formation) and wastewater. 

In addition to their high absorptive eapacity hormite clays offer useful thickening properties. When dispersed in water they do not swell, as smectites do. Instead, their needle-like colloidal particles deagglomerate in proportion to the amoimt of shear applied and form a random colloidal lattice. This loosely cohesive structure thickens the water and imparts thixotropy, pseudoplasticity, and yield value. Because of their mechanically-based dispersion and colloidal structure building, hormite cl s are largely insensitive to the types and levels of acids, bases, and salts dissolved in the aqueous systems in which they are used. Since their dispersion is mechanically rather than ionically driven, as with smectites, they can be used in nonaqueous applications in much the same... 

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