Solvent and cleaning process

There is also an excellent web site, SAGE (http //clean.rti.org), that provides a comprehensive guide to pollution prevention information on solvent and cleaning process alternatives. The U.S. EPA Air Pollution Prevention and Control Division developed SAGE (Solvent Alternatives Guide). 

Contaminants may be of three general types particulates, highly polar (ionic) residues, and nonpolar (grease-Uke) residues. In many production environments, all three types are present and several solvents and cleaning processes may be required to remove them. Both the choice of solvent or cleaning solution and the cleaning process are critical, and several theoretical principles may be followed in their selection. Ultimately, cleaning is more an art than a science, and the procedure chosen should be experimentally verified in each case. Qualitative and quantitative tests can be performed to determine the efficiency of a selected solvent and process. 

One example of the effect of such factors is UV inks used in printing, which were the snbject of a scandal early on, the positive evaluation of aqueous systems and bio paints , which were evaluated veiy positively despite their not unproblematic content of vegetable-based solvents. In addition, the comparatively speedy snbstitntion of chlorinated solvents in cleaning processes and formaldehyde separators in cooling lubricants can only in fact be explained by the pubhc-ity-effective scandals relating to chlorinated chemicals or formaldehyde. 

OTHER COMMENTS used as a solvent in paint removers and as a solvent for cellulose acetate vapor degreasing solvent for metals and plastics major use as a solvent and cleaning agent in the chemical processing industry used in the pharmaceutical industry as a solvent in the production of antibiotics, steroids, and vitamins chemical intermediate for bromochlo-romethane. 

Catalyst monoliths are also effective in the control of air pollution from stationary sources. They have been used for many years to oxidize hydrocarbon vapors in the vent streams from chemical plants and to reduce solvent emissions from printing and cleaning processes. More recent applications include CO removal from gas turbine exhaust and the selective catalytic reduction of NO in flue gas. Performance curves for the oxidation of various compounds over a Pt/Al203 catalyst are shown in Figure 10.5, where the conversion is plotted against the feed temperature. The reactors operate adiabatically, and the exit temperature may be 10-100°F above the feed temperature. At first, the conversion increases exponentially with temperature, as expected from the Arrhenius relationship. The decrease in slope... 

Ionic liquids are often considered as promising solvents for clean processes and green chemistry mainly due to their non-volatile character [1,2]. These two catchwords represent current efforts to drastically reduce the amounts of side and coupling products, as well as the solvent and catalyst consumption in chemical processes. As another green solvent concept for chemical reactions the replacement of volatile organic solvents by supercritical CO2 (scCOz) is frequently discussed [3]. 

Of the many factors in choosing a metal cleaning method, the degree of cleanliness required is perhaps the prime consideration. By selection of the proper solvent and cleaning equipment best suited to the shape of the work and the contaminants involved, the desired degree of cleanliness can usually be attained with the degreasing process. Solvent-soluble soils can be completely removed, and the insoluble soils flushed off. Because the final cycle in the process is a rinse in pure solvent vapors, no soluble residues will remain on the part nor will soil be redeposited. 

Some semi-aqueous cleaning is done by spray cleaning. In this case, the various solutions which are part of the semi-aqueous technology are successively applied to surfaces (probably large ones) and later collected. Then the solvent and water processing inherent to semi-aqueous technology is practiced in separate facilities. 

While process designs will be system specific (soil, solvent, and cleaning qualify), general calculations show that roughly 50% more total energy is required for a Class... 

Regardless of the metal pretreatment used, it is important to maintain as much control over the process as possible in order to assure consistently good results. Lubricants and anticorrosive oils that contain chlorinated paraffins or silicone should be avoided, as they can interfere with adhesion. All degreasing solvents and cleaning solutions must be kept clean and free of contamination. Grits and abrasives must be kept clean and periodically changed. Rinse water and drying air must be checked frequently for purity and kept free from oils. A simple test to measure the effectiveness of the metal pretreatment is called the water-break test. In this test, the prepared metal part is dipped briefly in... 

Recrystallisation. The process of purification by recrystallisation is undoubtedly the most frequent operation in practical organic chemistry, and it is one which, when cleanly and efficiently performed, should give great pleasure to the chemist, particularly if the original crude material is in a very impure and filthy condition. Yet no operation is carried out so badly, wastefully (and thoughtlessly) by students in general, not only by elementary students, but often by research students of several years experience. The student who intends later to do advanced work must master the process, for unless he can choose a suitable solvent and then successfully recrystallise often minute quantities of material, he will frequently find his work completely arrested. 

All glassware should be scrupulously clean and, for most purposes, dry before being employed in preparative work in the laboratory. It is well to develop the habit of cleaning all glass apparatus immediately after use the nature of the dirt will, in general, be known at the time, and, furthermore, the cleaning process becomes more difficult if the dirty apparatus is allowed to stand for any considerable period, particularly if volatile solvents have evaporated in the meantime. 

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