Sealed-vessel

Owing to the great tendency of hydrazobenzene to undergo oxidation, all operations involving filtration should be carried out as rapidly as possible and air should not be drawn through it unnecessarily. The substance should be dried in a vacuum desiccator it can only be preserved in a colourless condition if it is kept in an atmosphere of carbon dioxide or nitrogen or in sealed vessels. 

Germanium difluoride can be prepared by reduction (2,4) of GeF by metallic germanium, by reaction (1) of stoichiometric amounts of Ge and HF in a sealed vessel at 225°C, by Ge powder and HgF2 (5), and by GeS and PbF2 (6). Gep2 has been used in plasma chemical vapor deposition of amorphous film (see Plasma TECHNOLOGY Thin films) (7). 

Fig. 23. O-ring backed up by miter ring to seal vessel (121).

The bulk polycondensation of (10) is normally carried out in evacuated, sealed vessels such as glass ampules or stainless steel Parr reactors, at temperatures between 160 and 220°C for 2—12 d (67). Two monomers with different substituents on each can be cocondensed to yield random copolymers. The by-product sdyl ether is readily removed under reduced pressure, and the polymer purified by precipitation from appropriate solvents. Catalysis of the polycondensation of (10) by phenoxide ion in particular, as well as by other species, has been reported to bring about complete polymerisation in 24—48 h at 150°C (68). Catalysis of the polycondensation of phosphoranimines that are similar to (10), but which yield P—O-substituted polymers (1), has also been described and appears promising for the synthesis of (1) with controlled stmctures (69,70). 

Also, the presence of strong bases, even in trace amounts, can promote the formation of isocyanurates or carbodiimides. In the event of gross contamination, the exothermic reaction can sharply increase the temperature of the material. Normally, the trimerization reaction occurs first and furnishes heat for the carbodiimide reaction. The carbodiimide reaction Hberates carbon dioxide and forms a hard soHd. The Hberation of carbon dioxide in a sealed vessel could result in overpressurization and mpture. 

The recognition that PPS had significant commercial potential as an advanced material came in the late 1940s (12). MacaHum s PPS process is based on the reaction of elemental sulfur, -dichlorobenzene, and sodium carbonate in sealed vessels at 275—300°C (12). Typical products produced by the MacaHum process contain more than one sulfur per repeating unit x = 1.2-2.3) ... 

Methylene chloride is one of the more stable of the chlorinated hydrocarbon solvents. Its initial thermal degradation temperature is 120°C in dry air (1). This temperature decreases as the moisture content increases. The reaction produces mainly HCl with trace amounts of phosgene. Decomposition under these conditions can be inhibited by the addition of small quantities (0.0001—1.0%) of phenoHc compounds, eg, phenol, hydroquinone, -cresol, resorcinol, thymol, and 1-naphthol (2). Stabilization may also be effected by the addition of small amounts of amines (3) or a mixture of nitromethane and 1,4-dioxane. The latter diminishes attack on aluminum and inhibits kon-catalyzed reactions of methylene chloride (4). The addition of small amounts of epoxides can also inhibit aluminum reactions catalyzed by iron (5). On prolonged contact with water, methylene chloride hydrolyzes very slowly, forming HCl as the primary product. On prolonged heating with water in a sealed vessel at 140—170°C, methylene chloride yields formaldehyde and hydrochloric acid as shown by the following equation (6). 

Treatment of 2-methylthiirane with t-butyl hydroperoxide at 150 °C in a sealed vessel gave very low yields of allyl disulfide, 2-propenethiol and thioacetone. The allyl derivatives may be derived from abstraction of a hydrogen atom from the methyl group followed by ring opening to the allylthio radical. Percarbonate derivatives of 2-hydroxymethylthiirane decompose via a free radical pathway to tar. Acrylate esters of 2-hydroxymethylthiirane undergo free radical polymerization through the double bond. 

Some toll processes lend themselves to test runs in the pre-startup phase. Actual materials for the toll may be used in the test or substitute materials, typically with low hazard potential, are often used to simulate the charging, reaction, and physical changes to be accomplished in the toll. Flow control, temperature control, pressure control, mixing and transferring efficiency can be measured. Mechanical integrity can be verified in regard to pumps, seals, vessels, heat exchangers, and safety devices. 

Acetone may be used as solvent in place of ethyl methyl ketone, but the reaction must then be carried out in a sealed vessel at 95-100° for thirty to thirty-six hours. 

The pressure in the vapour space of an incompletely full, sealed vessel containing liquid cannot be reduced by partially draining off liquid. 

Boiling liquid expanding vapour explosion follows failure of a pressurized eontainer of flaimnable liquid, e.g. LPG, or a sealed vessel eontaining volatile flammable liquids, under fire eonditions. Ignition results in a fireball and missiles. 

As the seale of operation inereases, the effeet of the heat eonsump-tion by the plant typieally deelines. Therefore, the extent to whieh the kineties of the runaway reaetion is influeneed by the plant is redueed. For plant seale vessels, the ([t-faetor is usually low (i.e., 1.0-1.2) depending on the heat eapaeity of the sample and the vessel fill ratio. Laboratory testing for vent sizing must simulate these low ([t-faetors. If the laboratory ([t-faetor is high, several anomalies will oeeur ... 

A mixture of 4,4 parts of 1-chloro-3-(1-naphthoxy)-2-propano and 16 parts of isopropylamine is heated in a sealed vessel at 70° B0°C for 10 hours. The vessel is cooled and to the contents there are added 50 parts of water. The mixture is acidified with 2N hydrochloric acid, and washed with 50 parts of ether. The aqueous phase Is decolorized with carbon, and then added to 50 parts of 2N sodium hydroxide solution at 0°C, The mixture is filtered. The solid residue is washed with water, dried, and crystallized from cyclohexane. There is thus obtained 1-isopropylamino-3-(1-naphthoxy)-2-propanol, MP 96°C. 

Ref. [33] suggests minimum design pressure for such a seal vessel of 50 psig, ASME Code stamped (this author). Most flare seal drums operate at 0-5 psig pressure. 

Self-Test 9.9A The initial partial pressures of nitrogen and hydrogen in a rigid, sealed vessel are 0.010 and 0.020 bar, respectively. The mixture is heated to a temperature at which K = 0.11 for N2(g) + 3 H2(g) 2 NH3(g). What are the equilibrium partial pressures of each substance in the reaction mixture ... 

Vessels designed for microwave-assisted SPOS must fulfill several require-menfs because of fhe harsh conditions (i.e., high temperatures and pressures) usually associated with microwave heating. Open vessels are often impractical because of the possible loss of solvent and/or volatile reagents during the heating process. However, in cases where a volatile byproduct inhibits a reaction, their use may be superior over closed systems. A sealed vessel retains the solvents and reagents, but must be sturdily constructed to avoid the obvious safety implications due to the buildup of pressure. 

Fig. 26 Solid-phase synthesis of indol-2-ones by microwave-assisted radical cyclization. Reagents and conditions a NaH, DMF b BusSnH, AIBN, DMF, MW 170 °C, 45 min, sealed vessel c 10% TFA in CH2CI2. R = H, F, Me, OCF3 R = Phe, 3-OMe - Phe, 4-Me - Phe, 3,4-0CH20-Ph, (CH2)4, diMe R" = H, Me R " = H, Me...

Fig. 39 Microwave-assisted synthesis of pyridinones from resin-bonnd 2(iH)-pyrazinones. Reagents and conditions a dimethyl acetylenedicarboxylate, chlorobenzene, reflux (132 °C), 1-2 days or 1,2-dichlorobenzene, MW 220 °C, 20-40min b bromobenzene, reflux (156 °C), 2h or 1,2-dichlorobenzene, MW 220 °C, 10min R = OC2H4C2H c TFA, reflux (72 °C), 20-24 h or TFA/Ch2Cl2, MW 120 °C, 10-40min. R=OMe or Ph, R = methoxyphenyl. All microwave-assisted reactions were rim in sealed vessels...

Since the synthesis temperatures are higher than the dissociation temperatures of the phases that are formed (at a pressure of lO N m ), it is necessary to react the alkali metal with boron under metal pressure in excess of that defined by Eq. (a), in sealed vessels. The alkali metal is present as a liquid in equilibrium with the vapor phase, the pressure of which is determined by the T of the coldest point. This pressure (greater the more volatile the metal) favors the synthetic reaction relative to the reverse dissociation reaction. 

Seal vessel turn on jacket heat (140°C steam)... 

Nitrogen and hydrogen will sit happily together in a sealed vessel without reacting to form ammonia, with the equilibrium for the reaction being completely over to the left hand side of the equation under ambient conditions. 

Separation of the products was achieved using an ion-exchange method, the reaction taking place in sealed vessels with the Cr(Vl) labelled ( Cr). Under various conditions only 40% of the Cr appears in the product Cr2(OH)2. This led these workers to propose a modified mechanism in which the step involving Cr(V) proceeds in two ways... 

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