Suppliers, high pressure equipment

The hydroformylation of alkenes generally has been considered to be an industrial reaction unavailable to a laboratory scale process. Usually bench chemists are neither willing nor able to carry out such a reaction, particularly at the high pressures (200 bar) necessary for the hydrocarbonylation reactions utilizing a cobalt catalyst. (Most of the previous literature reports pressures in atmospheres or pounds per square inch. All pressures in this chapter are reported in bars (SI) the relationship is 14.696 p.s.i. = 1 atm = 101 325 Pa = 1.013 25 bar.) However, hydroformylation reactions with rhodium require much lower pressures and related carbonylation reactions can be carried out at 1-10 bar. Furthermore, pressure equipment is available from a variety of suppliers and costs less than a routine IR instrument. Provided a suitable pressure room is available, even the high pressure reactions can be carried out safely and easily. The hydroformylation of cyclohexene to cyclohexanecarbaldehyde using a rhodium catalyst is an Organic Syntheses preparation (see Section 4.5.2.5). 

To take away the mystery from the word supercritical, it should be recognized that a supercritical fluid can be used like any other solvent for maceration and percolation processes. The only restriction is that it must be handled under high pressure, a fact that requires a special and expensive design of the extraction apparatus. This obvious disadvantage however is compensated by many benefits as demonstrated below. Supercritical C02-extraction of botanical materials is today a well-developed and reliable procedure applied on an industrial scale for about 20 years. The equipment is available turn-key from various suppliers in multi-purpose design or tailor made for special applications. 

There are many vendors of rotor-stator mixers. The reader may refer to current editions of Thomas s Register, Chemical Engineering Buyers Guide, and so on, for an up-to-date list of major suppliers. There are a number of other suppliers whose equipment is used to produce dispersions or emulsions but which does not fit the definition of having a rotor and stator. These include high-pressure devices such as valve homogenizers, whistles, and cavitation-based devices. 

Where water is used as a cooling medium for compressor and ancillary equipment it should be within the temperature and pressure levels prescribed by the compressor supplier and should be free from harmful impurities. The cooling water should have a low inlet temperature in order to assist in achieving a high volumetric efficiency in the compressor and to cool the air passing through the aftercooler to a temperature adequate for effective condensation of water vapor. 

Samples of punch-and-die pressing can be produced in a variety of home made or purchased small machines. The previously mentioned force/pressure test stands (Fig. 11.18), which may also use hydraulic actuation with hand or motor pumps, can be applied in connection with home made punch-and-die arrangements. Many laboratories are equipped with automatically or hand operated hydraulic laboratory presses, for example as shown in Fig. 11.20 (see also Fig. 8.92, Section 8.4.3). From the suppliers of such machines a large number of simple or sometimes highly sophisticated and automated presses are available. They are used for the determination of a variety of strength and force or pressure related product characteristics and, although the densification and compaction mechanisms are quite different from those of roller presses and can not be correlated, punch-and-die compacts are often made and evaluated to preliminarily investigate the compactibility of different feed materials or powder mixtures and to determine the type and amount of potential binders. 

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