Distillation, automatic

For the reduction of pump noise in the actual laboratory the vacuum puiu]>s art-placed in a separate pump room. The pumps P are close to the wall between this room and the laboratory, so as to make the vacuum lines as short as possible. The other aide of tliis wall is provided with a framework M and is reserved for vacuum distillation. Automatic pressure controllers and vacuum gauges are placed on or behind the framework where they are accessible and can easily be watched. The pump room can also serve as a small workshop. 

Commercial equipment is available which automatically switches from atmospheric distillation to vacuum distillation and calculates the distillation curve as temperatures under atmospheric pressure conditions as a function of weight or volume per cent recovery. 

The purified commercial di-n-butyl d-tartrate, m.p. 22°, may be used. It may be prepared by using the procedure described under i o-propyl lactate (Section 111,102). Place a mixture of 75 g. of d-tartaric acid, 10 g. of Zeo-Karb 225/H, 110 g. (136 ml.) of redistilled n-butyl alcohol and 150 ml. of sodium-dried benzene in a 1-litre three-necked flask equipped with a mercury-sealed stirrer, a double surface condenser and an automatic water separator (see Fig. Ill, 126,1). Reflux the mixture with stirring for 10 hours about 21 ml. of water collect in the water separator. FUter off the ion-exchange resin at the pump and wash it with two 30-40 ml. portions of hot benzene. Wash the combined filtrate and washings with two 75 ml. portions of saturated sodium bicarbonate solution, followed by lOu ml. of water, and dry over anhydrous magnesium sulphate. Remove the benzene by distillation under reduced pressure (water pump) and finally distil the residue. Collect the di-n-butyl d-tartrate at 150°/1 5 mm. The yield is 90 g. 

Liquid crystal polyesters are made by a different route. Because they are phenoHc esters, they cannot be made by direct ester exchange between a diphenol and a lower dialkyl ester due to unfavorable reactivities. The usual method is the so-called reverse ester exchange or acidolysis reaction (96) where the phenoHc hydroxyl groups are acylated with a lower aHphatic acid anhydride, eg, acetic or propionic anhydride, and the acetate or propionate ester is heated with an aromatic dicarboxyHc acid, sometimes in the presence of a catalyst. The phenoHc polyester forms readily as the volatile lower acid distills from the reaction mixture. Many Hquid crystal polymers are derived formally from hydroxyacids (97,98) and thein acetates readily undergo self-condensation in the melt, stoichiometric balance being automatically obtained. 

Distillation columns are controlled by hand or automatically. The parameters that must be controlled are (/) the overall mass balance, (2) the overall enthalpy balance, and (J) the column operating pressure. Modem control systems are designed to control both the static and dynamic column and system variables. For an in-depth discussion, see References 101—104. 

Since the reliability of gas turbines in the power industry has been lower than desired in recent years because of hot-corrosion problems, techniques have been developed to detect and control the parameters that cause these problems. By monitoring the water content and corrosive contaminant in the fuel line, any changes in fuel quality can be noted and corrective measures initiated. The concept here is that Na contaminants in the fuel are caused from external sources such as seawater thus, by monitoring water content, Na content is automatically being monitored. This on-line technique is adequate for lighter distillate fuels. For heavier fuels, a more complete analysis of the fuel should be carried out at least once a month using the batch-type system. The data should be input directly to the computer. The water and corrosion detecting systems also operate in conjunction with the batch analysis for the heavier fuels. 

General. With simple instrumentation discussed here, it is not possible to satisfactorily control the temperature at both ends of a fractionation column. Therefore, the temperature is controlled either in the top or bottom section, depending upon which product specification is the most important. For refinery or gas plant distillation where extremely sharp cut points are probably not required, the temperature on the top of the column or the bottom is often controlled. For high purity operation, the temperature will possibly be controlled at an intermediate point in the column. The point where AT/AC is maximum is generally the best place to control temperature. Here, AT/AC is the rate of change of temperature with concentration of a key component. Control of temperature or vapor pressure is essentially the same. Manual set point adjustments are then made to hold the product at the other end of the column within a desired purity range. The technology does exist, however, to automatically control the purity of both products. 

Bums and Hazzan demonstrated tlie use of event tree and fault tree analysis in tlie study of a potential accident sequence leading to a toxic vapor release at an industrial chemical process plant. The initiator of tlie accident sequence studied is event P, the failure of a plant programmable automatic controller. Tliis event, in conjunction willi the success or failure of a process water system (a glycol cooling system) mid an operator-manual shutdown of tlie distillation system produced minor, moderate, or major release of toxic material as indicated in Fig. 21.4.1. The symbols W, G, O represent tlie events listed ... 

A more sophisticated method, giving a much more detailed characterization, involves the on-line coupling of EC and GC (LC-GC). Analysis schemes for middle distillates (kerosine, diesel and jet fuels) combining EC and GC have been reported by various authors (25-31). However, only Davies et al. (25) andMunari et al. (27) have reported on the required automatic transfer of all of the individual separated fractions from the EC unit the GC system. Davies used the loop-type interface and Munari the on-column interface. Only Beens and Tijssen report a full quantitative characterzation by means of LC-GC (31). 

When the distribution ratio is low, continuous methods of extraction are used. This procedure makes use of a continuous flow of immiscible solvent through the solution if the solvent is volatile, it is recycled by distillation and condensation and is dispersed in the aqueous phase by means of a sintered glass disc or equivalent device. Apparatus is available for effecting such continuous extractions with automatic return of the volatilised solvent (see the Bibliography, Section 9.10). 

It should also be emphasised that unless otherwise stated all reagents employed in the analytical procedures should be of appropriate analytical grade or spectroscopic grade materials. Similarly, where solutions are prepared in water this automatically means distilled or deionised water from which all but very minor impurities will have been removed. 

Automatic control of distillate composition (xD) may also be affected by control of the reflux ratio, for example to maintain the distillate composition at constant set point (xDset). 

The technique and apparatus used in this work have been described in detail [81]. The reaction vessel was made hydrophobic by exposure to the vapour of trimethylchlorosilane and evacuated for several hours. Then isobutene, dried by sodium, and methylene dichloride, stored over calcium hydride, were distilled into it, the temperature adjusted, and the reaction started by the breaking of a phial containing a solution of titanium tetrachloride in methylene dichloride and one containing water. These could be broken in this, or the reverse, order, or simultaneously. The ensuing reaction was registered as a time-temperature curve by an automatic recorder. The range of conditions studied was [C4H8] = 0.05 -0.6 mole/1, [TiClJ = (0.1-5) x 10 3 mole/1, [H20] = (0.05-5) x 10 4 mole/1, T= 18°- -95°. 

Norbornadiene (from Koch-Light Ltd.) of purity greater than 99% was purified by distillation through a Normatron automatic still at a reflux ratio of 25 1. The fraction (60 vol%) boiling at 89.3 °C/998 mbar was collected [18] bp 89.5 °C/1013 mbar). Analysis by gas liquid chromatography (GLC) (Pye Unicam - with OVO-1 columns), showed one... 

Even complex procedures can be automated, such as dialysis to clean up dirty samplers, solvent extraction, automatic distillation and on-hne UV digestion. Unhke the earlier AutoAnalyzer systems which use a purely step-wise autosampler, the TRAACS is fitted with a random-access sampler as standard. 

Automation of the manual UV method using an AutoAnalyzer method that incorporates a flash distillation stage has been described [S] and has been used routinely. This technique is unsuitable for unattended automatic operation because the flash distillation stage requires constant supervision. Attention was therefore concentrated on alternative chemical methods of measuring total nicotine alkaloids. By far the most promising of these is an AutoAnalyzer method based on the Konig reaction [6]. The mechanism of this reaction has been discussed by Roy [7] and is illustrated in Fig. 3.S. 

Fig. 4.3 Manifold diagram for the automatic determination of total SO 2 using a flash distillation technique.

Hydrocarbon distillates in the gas oil range ( diesel or derv ) are subject to duty when used as a road fuel. Gas oil, which is often identical to diesel oil in hydrocarbon composition, is exempt from duty when used for stationary machines. In order to prevent its misuse as a road fuel, gas oil is marked with a mixture of 1,4-dfhydroxyanthraquinone (quinizarin), 2-fiirfuraldehyde (furfural) and a red dye. An automatic method for the extraction, identification and determination of quinizarin in gas oil has been used hy the Laboratory of the Government Chemist (LGC) for some years. The presence of furfiiral provides evidence for legal prosecution and the numbers of analyses ordered in the UK merit automatic analysis. 

The ammonium extracted by the potassium chloride reagent is analysed by steam distillation. This may be carried out using an automatic instrument such as the Kjeltec Auto 1035 Analyzer (USDA, 1996, pp. 203-210), or a micro (or semi-micro) steam distillation unit such as that described by Bremner and Keeney (1965), or the readily available Markham still. We will describe the manual procedure. 

Distillation unit - the Markham semi-micro distillation unit is suitable, or a proprietary automatic unit. 

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