Vacuum large-scale

Boron Triiodide. Boron ttiiodide is not manufactured on a large scale. Small-scale production of BI from boron and iodine is possible in the temperature range 700—900°C (70—72). Excess I2 can be removed as Snl by reaction with Sn, followed by distillation (71). The reaction of metal tetrahydroborates and I2 is convenient for laboratory preparation of BI (73,74). BI can also by synthesized from B2H and HI in a furnace at 250°C (75), or by the reaction of B with excess Agl or Cul between 450—700°C, under vacuum (76). High purity BI has been prepared by the reaction of I2 with mixtures of boron carbide and calcium carbide at elevated temperatures. 

Distillation. Vacuum distUlation (qv) of water, which contains the three molecular species H2O, HDO, and D2O, was the first method used for the large-scale extraction of deuterium (10,58) (Fig. 2). From the equHibrium constant in the Hquid phase it is evident that the distribution of H and D is not statistical. The differences in vapor pressure between H2O and D2O are significant, and a fractionation factor (see Table 7) of 1.05 can be obtained at... 

Today the sulphonation route is somewhat uneconomic and largely replaced by newer routes. Processes involving chlorination, such as the Raschig process, are used on a large scale commercially. A vapour phase reaction between benzene and hydrocholoric acid is carried out in the presence of catalysts such as an aluminium hydroxide-copper salt complex. Monochlorobenzene is formed and this is hydrolysed to phenol with water in the presence of catalysts at about 450°C, at the same time regenerating the hydrochloric acid. The phenol formed is extracted with benzene, separated from the latter by fractional distillation and purified by vacuum distillation. In recent years developments in this process have reduced the amount of by-product dichlorobenzene formed and also considerably increased the output rates. 

In the usual high-vacuum apparatus I placed aluminum borohydride onto a sample of uranium tetrafluoride. I observed an immediate reaction, with formation of green crystals which could be moved about the vacuum apparatus. As it happened, on the very day I was performing the synthesis, we had a visit from Professor H. C. Urey, who was in charge of the overall study. He immediately asked us to increase our research effort and undertake to prepare uranium tetraborohydride on a relatively large scale, adequate for testing. 

For detailed characterization and extensive studies of reactivity, multi-gram quantities are still needed and large-scale metal vapor synthetic routes are necessary. The equipment required for this is well-documented (4) and so will not be described in detail here. The principles are those of the Fluid Matrix Technique except that in order to accommodate 10-100 gram of polymer, the coreactant is contained within a rotating flask which serves to provide a continuously renewed film as metal atoms are produced under high vacuum. 

The residue from a large scale atmospheric pressure distillation of trimethyl phosphate exploded violently. This was attributed to rapid decomposition of the ester, catalysed by the acidic degradation products, with evolution of gaseous hydrocarbons. It is recommended that only small batches of alkyl phosphates should be vacuum distilled and in presence of magnesium oxide to neutralise any acid by-products, and to suppress the acid catalysed reaction. 

During the vacuum fractional distillation of bulked residues (7.2 t containing 30-40% of the bis(hydroxyethyl) derivative, and up to 900 ppm of iron) at 210-225°C/445-55 mbar in a mild steel still, a runaway decomposition set in and accelerated to explosion. Laboratory work on the material charged showed that exothermic decomposition on the large scale would be expected to set in around 210-230°C, and that the induction time at 215°C of 12-19 h fell to 6-9 h in presence of mild steel. Quantitative work in sealed tubes showed a maximum rate of pressure rise of 45 bar/s, to a maximum developed pressure of 200 bar. The thermally induced decomposition produced primary amine, hydrogen chloride, ethylene, methane, carbon monoxide and carbon dioxide. 

Whilst it may be possible to predict qualitatively the effect of the physical properties of the fluid and the solid on the filtration characteristics of a suspension, it is necessary in all cases to carry out a test on a sample before the large-scale plant can be designed. A simple vacuum filter with a filter area of 0.0065 m2 is used to obtain laboratory data, as illustrated in Figure 7.5. The information on filtration rates and specific resistance obtained in this way can be directly applied to industrial filters provided due account is taken of the compressibility of the filter cake. It cannot be stressed too... 

Desalination has been practiced for many years, although the early large-scale industrial applications were in the 1960s in the Middle-East using thermal desalination technologies such as multistage flash or multi-effect distillation. These plants used sophisticated thermal or vacuum systems to effectively distil a portion... 

Air separation by PSA on a large scale is today dominated by machines in which the pressure swing may be from near atmospheric to substantially sub-atmospheric pressure. The industry typically calls these machines vacuum swing adsorption (VSA) separators. A second sub-class in air separation is the machines that use a pressure swing the ranges from somewhat super-atmospheric to sub-atmospheric and these may be called trans-atmospheric PSA. The distinctions made here have implications as to equipment specifications and performance limitations in both bed size factor and O2 recovery. 

For the stoichiometric liquid-liquid large-scale synthesis a flat steel pan (31x44 cm ) was charged with benzaldehyde (77k) (99.5% 848 g, 7.95 mol) and aniline (236s) (99.5% 744 g, 7.95 mol) (Scheme 51). The liquids were mixed at 18 °C. The temperature rose to a maximum of 32 °C and fell back to 24 °C when crystallization started with another increase in temperature to a maximum of 35 °C within 12 min when crystallization was virtually complete and water of reaction separated. Next day, the wet crystal cake was crunched with an ordinary household grain mill and dried in a vacuum at room temperature to give 1.438 kg (100%) of pure benzylidene-aniline (54s). 

Thermal reduction processes are not being practiced anywhere in the world at present for large-scale production of sodium. Such methods, however, can he conveniently adapted for laboratory preparation of metalhc sodium. Sodium can be prepared by thermal reduction of its hydroxide, carbonate, or chloride at elevated temperatures. These salts are heated with carbon, calcium carbide, iron carbide, ferrosilicon, or other reducing agents at temperatures above 800°C under vacuum ... 

Batch crystallizers are used primarily for production of fine chemicals and pharmaceuticals at the rate of 1-100 tons/week. The one exception is the sugar industry that still employs batch vacuum crystallization on a very large scale. In that industry, the syrup is concentrated in triple- or quadruple-effect evaporators, and crystallization is completed in batch vacuum pans that may or may not be equipped with stirrers [Fig. 16.11(g)]. 

Drying. The conditioned frozen material to be dried is placed in a vacuum chamber, where sublimation and desorption of water occur. As soon as the chamber has been evacuated and the optimum vacuum has been reached (0.5 to 0.05 millimeters of mercury), heating is applied so that the ice sublimes. For large-scale production of food products, the combination of conduction and radiation that results from circulating a hot fluid through coils or plates has proved quite satisfactory for heating. 

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