Sulphate regeneration

A more detailed investigation of the rate expression for ferric sulphate regeneration with SO2/O2 will be presented later. Based on these results and data already published, the reaction rate for ferric ion regeneration with SO2/O2 mixtures can be expressed as ... 

Third, regeneration efficiency (i.e., the conversion of CaS04 into CaO) as determined by the Sulphation-Regeneration-Oxidation-test in a thermobalance [5] dqrends strongly on the... 

If the mixture contains an excess of ethanol, and is heated to 140°, the ethyl hydrogen sulphate reacts with the ethanol, giving diethyl ether And regenerating the sulphuric acid ... 

If the mixture contains a considerable excess of sulphuric acid and is heated to 160-170 , the ethyl hydrogen sulphate breaks down, giving ethylene and again regenerating the sulphuric acid. 

The sulphuric acid and ethyl hydrogen sulphate required in reactions 1 and 3 respectively are regenerated in reactions 2 and 4, but the water formed is retted in the acid mixture and ultimately results in such a dilution that the caiversion into ether is no longer efficient. Furthermore, some ethylene is always formed this partly polymerises to give materials capable of reacting with sulphuric acid and reducing it to sulphur dioxide. In industrial practice, sulphuric acid is sufficient for the production of about 200 parts of ether. 

The resultant yellow sodium cellulose xanthate is dispersed in an aqueous caustic soda solution, where some hydrolysis occurs. This process is referred to as ripening and the solution as viscose . When the hydrolysis has proceeded sufficiently the solution it transferred to a hopper from which it emerges through a small slit on to a roller immersed in a tank of 10-15% sulphuric acid and 10-20% sodium sulphate at 35-40°C. The viscose is coagulated and by completion of the hydrolysis the cellulose is regenerated. The foil is subsequently washed, bleached, plasticised with ethylene glycol or glycerol and then dried. 

Preparation. The mother liquors from strychnine manufacture are concentrated and the alkaloids precipitated as neutral oxalates. The precipitate is dried and extracted with dry alcohol in which the strychnine salt is the more soluble. The less soluble salt dissolved in water is decolorised with charcoal, the alkaloid regenerated with ammonia and purified by crystallisation as the sulphate. According to Saunders, pure brucine may be obtained by slow crystallisation from a solution of the pure hydrochloride in alcoholic ammonia. A method of separation depending on the greater solubility in water of strychnine hydriodide was employed by Shenstone, whilst others have made use of the sparing solubility of strychnine chromate for the removal of small quantities of this alkaloid from brucine. For a large scale process see Schwyzer. ... 

Thus for non-ferrous metals, SO is consumed in the corrosion reactions whereas in the rusting of iron and steel it is believed that ferrous sulphate is hydrolysed to form oxides and that the sulphuric acid is regenerated. Sulphur dioxide thus acts as a catalyst such that one SOj" ion can catalyse the dissolution of more than 100 atoms of iron before it is removed by leaching, spalling of rust or the formation of basic sulphate. These reactions can be summarised as follows ... 

Acetylcyclohexanone. Method A. Place a mixture of 24-6 g. of cyclohexanone (regenerated from the bisulphite compound) and 61 g. (47 5 ml.) of A.R. acetic anhydride in a 500 ml. three-necked flask, fitted with an efficient sealed stirrer, a gas inlet tube reaching to within 1-2 cm. of the surface of the liquid combined with a thermometer immersed in the liquid (compare Fig. II, 7, 12, 6), and (in the third neck) a gas outlet tube leading to an alkali or water trap (Fig. II, 8, 1). Immerse the flask in a bath of Dry Ice - acetone, stir the mixture vigorously and pass commercial boron trifluoride (via an empty wash bottle and then through 95 per cent, sulphuric acid) as fast as possible (10-20 minutes) until the mixture, kept at 0-10°, is saturated (copious evolution of white fumes when the outlet tube is disconnected from the trap). Replace the Dry Ice-acetone bath by an ice bath and pass the gas in at a slower rate to ensure maximum absorption. Stir for 3 6 hours whilst allowing the ice bath to attain room temperature slowly. Pour the reaction mixture into a solution of 136 g. of hydrated sodium acetate in 250 ml. of water, reflux for 60 minutes (or until the boron fluoride complexes are hydrolysed), cool in ice and extract with three 50 ml. portions of petroleum ether, b.p. 40-60° (1), wash the combined extracts free of acid with sodium bicarbonate solution, dry over anhydrous calcium sulphate, remove the solvent by... 

When ion-exchange resin containing zirconium hydroxide comes into contact with acidic brine in the RNDS , zirconium hydroxide adsorbs bisulphate ions thus sulphate is removed from brine. For regeneration of the ion-exchange resin, a basic solution is supplied and when it comes into contact with the resin, sulphate desorption starts. 

For repeated use of the resin, a regeneration process is applied. This involves supplying alkaline water to the column from the bottom, where sulphate is desorbed by way of the fluidised bed, based on the equations ... 

Novel ion-exchange technology has recently been developed for purification of brine. Different resins have been developed for removal of sulphate impurities as well as calcium and magnesium hardness. The process is very simple and since only water is consumed to regenerate the ion-exchange resins, the operating costs are extremely low. The equipment, which is similar to that currently widely utilised for purification of waste acid, is very compact. It is expected that commercial-scale systems of both types will be installed later in 2000. 

FIGURE 6.7. Catalytic conversion of 1-butene in the alkylation of isobutane with 1-butene (at a mol ratio of 12 1) versus reaction time over various catalysts (1 g each) JML-I50 (A) JML-I50 regenerated five times by calcination and sulphation (B) SZ(C) SZ/Si02 (Zr/Si = 50/100, mol/mol) (D) zeolite Beta (Si02/Al203 = 40) (E) zeolite ZSM-5 (Si02/Al203 = 40) (F). 

Manganese dioxide can be used to absorb the initially low concentration SO2 to produce the sulphate in a Mitsubishi Process (23). In this case the absorbing phase is itself the oxidising agent. Regeneration with ammonia and air simultaneously produces ammonium sulphate which can be directly marketed as a fertiliser, thus the calcium ion problem of the dry limestone process is replaced by a plant nutrient ion -... 

Calcium sulphate (anhydrous). (Prepared by heating the dihydrate or the hemihydrate in an oven at 235 for 2-3h it can be regenerated.) Available commercially as Drierite. It forms the hemihydrate, 2CaSO4.H2O, so that its capacity is fairly low (6.6% of its weight of water), and hence is best used on partially dried substances. It is very efficient (being comparable with phosphorus pentoxide and concentrated sulphuric acid). Suitable for most organic compounds. Solvents boiling below 100 can be dried by direct distillation from calcium sulphate. 

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