Molecular vacuum distillation

Isolation of Volatile Compounds from Oat Oil. Four oil samples were obtained from each oat variety, as shown in Figure 1. Each oil was isolated, in triplicate, for its volatile fraction by means of molecular vacuum distillation. The equipment used has been previously described (11, 12). Aliquots of 5.0 grams were used. The isolation was performed at room temperature and proceeded for 4 hours from the time secondary vacuum was... 

Molecular Vacuum Distillation, 3-5 10 >mbar/4h at Room Temp. 1... 

Two oat varieties were studied with respect to their oil content. The composition of these SCCO2 extracted oils, with regard to fatty acids, free fatty acids, phosphorus and thermal stability has previously been reported (Fors and Eriksson, submitted for publication 1988). Volatile compounds were isolated from the oat oils by molecular vacuum distillation. The fractions obtained were transferred to aqueous alkali and extracted by CH2CI2. The adjustment in pH was made to remove fatty acids which could otherwise interfere with the later work. Moreover, it is well established that many heterocycles are important flavor compounds in heated food items. These compounds are normally isolated in the basic fraction. The isolates were analysed by chemical and sensory methods. 

For the above-mentioned products, critical fluid technology faces stiff competition from molecular (vacuum) distillation techniques, a time-honored technique, although greater selectivity is potentially available utilizing critical-fluid-based methods. This, coupled with the fact that C02-derived extracts exhibit, in many cases, extended shelf-lives due to the prophylactic action of the residual, nonoxidative CO2 atmosphere, as well as micro-organism de-... 

The so-called hydro-vac pump, shown in Fig. 11, 22, 2 (the upper half of the mercury reservoir and the column above it are insulated by a layer of asbestos), is an inexpensive, all-glass, mercury diffusion pump, which can be used in series either with an oil pmnp or with a water Alter pmnp (compare Fig. 11,21, 1) capable of producing a vacuum of at least 2 mm. It is accordingly of particular value in the organic laboratory for vacuum distillations, fractionations, sublimations and pyrolyses as well as for molecular distillations (see Section 11,26). The hydro-vac... 

AH three processes give perfluoropolyethers with a broad distribution of molecular weights. They are typically separated into fractions by vacuum distillation. 

The copolymerization occurs in an aqueous emulsion. When free radicals are used, a random copolymer is obtained. Alternating copolymers are produced when a Zieglar-Natta catalyst is employed. Molecular weight can be controlled by adding modifiers and inhibitors. When the polymerization reaches approximately 65%, the reaction mixture is vacuum distilled in presence of steam to recover the monomer. 

Two heat-sensitive organic liquids of an average molecular mass of 155 kg/kmol are to be separated by vacuum distillation in a 100 mm diameter column packed with 6 mm stoneware Raschig rings. The number of theoretical plates required is 16 and it has been found that the HETP is 150 mm. If the product rate is 5 g/s at a reflux ratio of 8, calculate the pressure in the condenser so that the temperature in the still does not exceed 395 K (equivalent to a pressure of 8 kN/m2). It may be assumed that a = 800 m2/m3, /x = 0.02 mN s/m2, e = 0.72 and that the temperature changes and the correction for liquid flow may be neglected. 

A packed column, 1.2 m in diameter and 9 m tall, is packed with 25 mm Raschig rings, and used for the vacuum distillation of a mixture of isomers of molecular mass 155 kg/kmol. The mean temperature is 373 K, the pressure at the top of the column is maintained at 0.13 kN/m2 and the still pressure is 1.3-3.3 kN/m2. Obtain an expression for the pressure drop on the assumption that this is not appreciably affected by the liquid flow and may be calculated using a modified form of Carman s equation. Show that, over the range of operating pressures used, the pressure drop is approximately directly proportional to the mass rate of flow rate of vapour, and calculate the pressure drop at a vapour rate of 0.125 kg/m2. The specific surface of packing, S = 190 m2/m3, the mean voidage of bed, e = 0.71, the viscosity of vapour, // = 0.018 mN s/m2 and the molecular volume = 22.4 m3/kmol. 

A packed column, 1.22 m in diameter and 9 m high, and packed with 25 mm Raschig rings, is used for the vacuum distillation of a mixture of isomers of molecular mass 155 kg/kmol. The mean temperature is 373 K, the pressure at the top of the column is maintained at 0.13 kN/m2, and the still pressure is 1.3 kN/m2. Obtain an expression for... 

Lower members of the series of acid chlorides are colourless liquids the higher members are colourless crystalline solids. At ordinary pressure most of them boil without decomposition. Vacuum distillation is only indicated with those of high molecular weight. The boiling points of the add chlorides are lower than those of the acids, for the replacement of hydroxyl by chlorine usually causes a lowering of the boiling point ... 

Table I provides a summary of the experimental data and the results obtained. As mentioned earlier, the final molecular weight of the oligomers are dictated by the initial ratio of D4 to DSX, the "end blocker . As expected, Mn values are usually slightly lower than that aimed for. This is no doubt due to the formation of the cyclic side products. The latter are removed from the system by vacuum distillation and are known to be present in such equilibrations at a typical level of around 10 percent by weight.

Residua are the dark-colored nearly solid or solid products of petroleum refining that are produced by atmospheric and vacuum distillation (Figure 11.1 Chapter 3). Asphalt is usually produced from a residuum and is a dark brown to black cementitious material obtained from petroleum processing that contains very high-molecular-weight molecular polar species called asphaltenes that are soluble in carbon disulfide, pyridine, aromatic hydrocarbons, and chlorinated hydrocarbons (Chapter 3) (Gruse and Stevens, 1960 Guthrie, 1967 Broome and Wadelin, 1973 Weissermel and Arpe, 1978 Hoffman, 1983 Austin, 1984 Chenier, 1992 Hoffman and McKetta, 1993). 

Haas) and I(-( hydroxymethyl)acrylamlde (IJ-methylol acrylamide, American Cyanamld) were used without purification. Acetonitrile was dried over molecular sieves (4A) and distilled prior to use. Ethanolamlne and l-amlno-2-propanol were vacuum distilled. Reagent grade acryloyl chloride, 2-propanol, and sodium persulfate were used as received. 

Poly(ethyl methacrylate) (Cellomer Associates) was vacuum dried at 50 C. The molecular weight (M ) was determined to be 3.3 X 10 from its intrinsic viscosity in ethyl acetate.— Chloroform (spectral grade) and deuterochloroform (MSD Isotopes) were used as received. Prior to sample preparation the solvent was degassed using five freeze-thaw cycles. The solvent was vacuum distilled onto the polymer In a 12 nm NMR tube, and sealed. 

Since fermentation takes place in a dilute aqueous solution, the reaction continues until the alcohol concentration approaches about 14%. At higher concentrations, the process becomes self-inhibitory. By-products from starch fermentation to ethanol can include higher-molecular-weight alcohols, glycerine, and ethers. Usually no more than 10% starch is converted to these compounds. Atmospheric distillation, vacuum distillation, and membrane separation techniques can be used to recover ethanol from the final fermented product. The distillate bottoms, called stillage, are recovered as a by-product for animal feed. A biomass fermentation flow diagram is provided in FIGURE 12-2. 

The HC1 dissolves quickly in the water but the PF3 hydrolysis is slow. The product is then given a final purification from water and other materials by a vacuum distillation from a methylcyclohexane slush bath (—128 °C). However, the molecular sieve trap works better and avoids the 10 to 20% loss that occurs from PF3 hydrolysis. The product should give a negative chloride test7 indicating absence of HC1 and/or by-products PC1F2 or PC12 F. 

---