PH, control unit

In continuous-flow experiments a feasible way is to apply a pH-control unit which continuously doses NaOH. The slight scatter of the pH normally observed will not negative influence on the oxidation results. ... 

Method A. Enantiomerically pure ethyl (R-)2-fluorohexanoate (60% hydrolysis). A 1-L Morton flask equipped with a mechanical stirrer, glass baffle, an electrode connected to a pH control unit and an addition tube connected to a syringe pump, is charged with 300 mL of 0.05 M aqueous phosphate buffer (pH 7.0) (Fisher), 300 mL of deionized water, and 70 g (0.43 mol) of ethyl 2-fluorohexanoate. The resulting mixture is stirred for several minutes and the pH is adjusted to 7.0 with the addition of a few... 

Modifications of the basic process are undersoftening, spHt recarbonation, and spHt treatment. In undersoftening, the pH is raised to 8.5—8.7 to remove only calcium. No recarbonation is required. SpHt recarbonation involves the use of two units in series. In the first or primary unit, the required lime and soda ash are added and the water is allowed to settie and is recarbonated just to pH 10.3, which is the minimum pH at which the carbonic species are present principally as the carbonate ion. The primary effluent then enters the second or secondary unit, where it contacts recycled sludge from the secondary unit resulting in the precipitation of almost pure calcium carbonate. The effluent setties, is recarbonated to the pH of saturation, and is filtered. The advantages over conventional treatment ate reductions in lime, soda ash, and COg requirements very low alkalinities and reduced maintenance costs because of the stabiUty of the effluent. The main disadvantages are the necessity for very careful pH control and the requirement for twice the normal plant capacity. 

A full set of bioreactors with pH and temperature controllers are shown in Figure 1.3. The complete set of a 25 litre fermenter with all the accessory controlling units creates a good opportunity to control suitable production of biochemical products with variation of process parameters. Pumping fresh nutrients and operating in batch, fed batch and continuous mode are easy and suitable for producing fine chemicals, amino acids, and even antibiotics. 

FIG. 9 Saponification of alkane sulfochlorides (Leuna technology). 1, Saponification reactor 2, pH control 3, separation tube 4, cooler 5, dilution stirring unit 6, preheater 7, vaporizer 8, cyclone separator 9, condensor 10, cooling roller 11, stirred dissolution tank. 

Several cases of spontaneous ignition after exposure to air of fine coke particles removed from filter strainers on a petroleum refinery furfural extraction unit have been noted. This has been associated with the use of sodium hydrogen carbonate (bicarbonate) injected into the plant for pH control, which produced a pH of 10.5 locally. This would tend to resinify the aldehyde, but there is also the possibility of a Cannizzaro reaction causing conversion of the aldehyde to furfuryl alcohol and furoic acid. The latter, together with other acidic products of autoxidation of the aldehyde, would tend to resinily the furfuryl alcohol. Pyrolysis GLC showed the presence of a significant proportion of furfuryl alcohol-derived resins in the coke. The latter is now discarded into drums of water, immediately after discharge from the strainers, to prevent further incidents. 

Figure 5 Temperature-dependent turbidimetry profiles for solutions of poly(Lys-25) at pH 7.0 and 11.0. These measurements were performed on a Pharmacia Biotechnology Ultrospec 3000 UV/visible spectrophotometer equipped with a programmable Peltier cell and temperature control unit.

By attachment of a chiral controlling unit, the reaction could also be carried out asymmetrically (100). Subjecting 352 (R = 2-naphthyl, R = H) to cycloaddition with 353 in the presence of AgOAc (1.5 M equiv) and EtaN (1.0 M equiv) furnished the enantiopure adduct 354 in 50%, with no other reaction products being observed. The reaction could be improved by alteration of the metal salt. Treatment of 352 (R = R = Ph) with dipolarophile 353 in the presence of LiBr and EtsN delivered the expected, enantiomerically pure adduct 354 in >90% yield, while 352 (R = 2-naphthyl, R = H) gave rise to 354 in quantitative yield with TINO3 and EtaN (Scheme 3.119). 

In AAC technologies, water is exposed to an AAC material, and metals in the water are adsorbed by the material. AAC systems can be designed and built as stand-alone units or integrated to work efficiently in concert with complementary water treatment systems designed for hydrocarbon removal, pH control, particulate removal, or electrodialysis. AAC systems can tolerate hard water (calcium and magnesium) and high temperatures (up to 200°F) without a decrease in performance. 

In laboratory experiments, selective membranes were already applied years ago for the pH-control during the electro-dialysis of pH-sensitive colloids. In the three-compartment cells used, the electrode chambers were rinsed with distilled water. On account of the high mobility of the H+ ions, the desalting cell was inclined to become acid. To oppose this effect, anode- and cathode membranes with different polarity were sought for. At the beginning the influence of these membranes on the current efficiency — i.e. the amount of salt removed per unit of charge flown through — was mentioned only sporadically (5,23). 

Both plant concepts, [R 10] and [R 11], can be equipped with different types of online analytics, e.g. pH value, conductivity, UV, IR, and different process control units. Incorporation of additional reactor device allows one to perform even complex chemical reactions, including gas/liquid reactions. The pressure is limited to 8 bar, in special cases up to 30 bar, and the maximum temperature is 200 °C. 

The STR was equipped with temperature, pH, and Po2 control units. Only one Rushton impeller was used to homogenize the system. Almost 1L of the culture medium supplemented with the carbon sources was used during the test runs. In the configuration with marbles, the total volume occupied by marbles (average diameter of 16 mm) was roughly 350 mL. In the configuration with the metal cylinder around the stirrer axle, the volume available in the external cavity was 565 mL. 

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