High pressure vessel general

The procedure described illustrates a new general synthetic method for the preparation of (E)-3-allyloxyacrylic acids and their conversion to a-unsubstituted y,6-unsaturated aldehydes by subsequent Claisen rearrangement-decarboxylation. Such aldehydes are traditionally prepared by Claisen rearrangements of allyl vinyl ethers. Allyl vinyl ethers are typically prepared by either mercury-catalyzed vinyl ether exchange with allylic alcohols or acid-catalyzed vinylation of allylic alcohols with acetals. The basic conditions required for alkoxide addition to the betaine to produce carboxyvinyl allyl ethers, as described in this report, nicely complements these two methods. In addition, this Claisen rearrangement is an experimentally very simple procedure, since sealed tube and other high pressure vessels are not required. The allyloxyacrylic acids are heated neat (in most cases a small amount of hydroquinone is added) and, by adjusting the pressure at which the reaction is performed, the aldehyde products distill from the reaction mixture in analytically pure form. 

The experimental determination of the melting point at high pressures is generally somewhat difiicult. In some cases it is easier to determine the pressure at which the fusion or solidification of a substance in a closed vessel comes to a stop at constant temperature. A very simple and ingenious mano-cryometer was invented by de Visser for this purpose (Fig. 24). The substance in A is separated by a column of mercury Digitized by Microsoft ... 

In the design of high-pressure vessels, both the size and the pressure involved will dictate the type of construction used. In general the following four types are used. 

The synthesis of crystalline molecular sieve zeoHtes in hydrothermal systems involves the combination of the appropriate amoimts of aliuninates and sih-cates, usually in basic media, and usually in an aqueous medium. Syntheses generally will proceed at ambient or moderate temperatures, however, crystallization rates generally are much faster at elevated temperatures, approaching 100 °C, if pressures below one atmosphere are desired, and temperatures up to about 180 °C, if high pressure vessels are used. Most zeolites of commercial interest are metastable phases, requiring that synthesis processes be terminated at some predetermined time to avoid contamination of the solid product with denser undesirable phases. 

Gas processing facilities generally work best at between 10 and 100 bar. At low pressure, vessels have to be large to operate effectively, whereas at higher pressures facilities can be smaller but vessel walls and piping systems must be thicker. Optimum recovery of heavy hydrocarbons is achieved between 20 bar and 40 bar. Long distance pipeline pressures may reach 150 bar and reinjection pressure can be as high as 700 bar. The gas process line will reflect gas quality and pressure as well as delivery specifications. 

Explosion-Pressure-Resistant Design for Reduced Maximum Explosion Overpressure with Explosion Suppression Explosion suppression systems provide one means to prevent the buildup of an inadmissibly high pressure, which is the consequence of explosions of combustible material in vessels. They operate by effectively extinguishing explosion flames in the initial stage of the explosion. An explosion of combustible material can generally be regarded as successfully suppressed when the maximum explosion overpressure can be lowered to a reduced explosion overpressure of not more than 1 bar (see Fig. 26-40). 

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