Sulphuric acid economics

To obtain a maximum yield of the acid it is necessary to hydrolyse the by-product, iaoamyl iaovalerate this is most economically effected with methyl alcoholic sodium hydroxide. Place a mixture of 20 g. of sodium hydroxide pellets, 25 ml. of water and 225 ml. of methyl alcohol in a 500 ml. round-bottomed flask fitted with a reflux (double surface) condenser, warm until the sodium hydroxide dissolves, add the ester layer and reflux the mixture for a period of 15 minutes. Rearrange the flask for distillation (Fig. II, 13, 3) and distil off the methyl alcohol until the residue becomes pasty. Then add about 200 ml. of water and continue the distfllation until the temperature reaches 98-100°. Pour the residue in the flask, consisting of an aqueous solution of sodium iaovalerate, into a 600 ml. beaker and add sufficient water to dissolve any solid which separates. Add slowly, with stirring, a solution of 15 ml. of concentrated sulphuric acid in 50 ml. of water, and extract the hberated acid with 25 ml. of carbon tetrachloride. Combine this extract with extract (A), dry with a httle anhydrous magnesium or calcium sulphate, and distil off the carbon tetrachloride (Fig. II, 13, 4 150 ml. distiUing or Claisen flask), and then distil the residue. Collect the wovaleric acid 172-176°. The yield is 56 g. 

Both of these methods are more economical in the consumption of alcohol and more convenient than that in which the acid is refluxed with a large excess of alcohol in the presence of concentrated sulphuric acid. An example of the latter procedure is described ... 

Although the first industrial application of anodic protection was as recent as 1954, it is now widely used, particularly in the USA and USSR. This has been made possible by the recent development of equipment capable of the control of precise potentials at high current outputs. It has been applied to protect mild-steel vessels containing sulphuric acid as large as 49 m in diameter and 15 m high, and commercial equipment is available for use with tanks of capacities from 38 000 to 7 600000 litre . A properly designed anodic-protection system has been shown to be both effective and economically viable, but care must be taken to avoid power failure or the formation of local active-passive cells which lead to the breakdown of passivity and intense corrosion. 

The evaluation of carriers and catalyst compositions showed that significantly higher SO2 oxidation activity could be achieved with Cs as a promoter under the operating conditions downstream the intermediate absorption tower as demonstrated by the results in Table 1, where the activity compared to the standard product is increased by more than a factor 2. This was clearly sufficient for the introduction of VK69 to the market as a new sulphuric acid catalyst. The activity results for different melt compositions were used to optimise the vanadium content and the molar ratios of K/V, Na/V. and Cs/V. However, the choice of Cs/V was not only a question of maximum activity, because of the significant influence of the Cs content on the raw material costs (the price of caesium is 50-100 times the price of potassium on a molar basis). Here, the economic benefits obtained by the sulphuric acid producer by the marginal activity improvement at high Cs content also had to be taken into account. 

The alkali sulphates can also be made by neutralizing, say, a soln. of 5 grms. of sulphuric acid in 30 c.c. of water with the alkali hydroxide or carbonate, and evaporating the soln. until crystals begin to form. The process is not economical except on a small scale. It is used mainly for lithium, rubidium, and caesium sulphates. H. Erdmann 20 treated a hot soln. of crude rubidium iron alum with milk of lime made from purified lime, and filtered the liquid from the excess of lime, calcium sulphate, and ferric hydroxide, by suction. The small amount of lime in soln. is precipitated by adding rubidium carbonate. The filtrate is neutralized with sulphuric acid, and evaporated to the point of crystallization. 

The primary object of these improvements is to render again available in the manufacture the sulphur contained in alkaline waste, which in the ordinary method is totally lost. As those relate more especially to the economical production of sulphuric acid, they will be further noticed in connection with the article to be specially devoted to that substance. 

Originally, the hydration of olefins to alcohols was carried out with dilute aqueous sulphuric acid as the catalyst. Recently, the direct vapour phase hydration of olefins with solid catalysts has become the predominant method of operation. From the thermodynamic point of view, the formation of alcohols by the exothermic reaction (A) is favoured by low temperatures though even at room temperature the equilibrium is still in favour of dehydration. To induce a rapid reaction, the solid catalysts require an elevated temperatue, which shifts the equilibrium so far in favour of the olefin that the maximum attainable conversion may be very low. High pressures are therefore necessary to bring the conversion to an economic level (Fig. 11). To select an optimum combination of reaction conditions with respect to both rate limitation and equilibrium limitation,... 

The limit of concentration attainable by any of the foregoing methods is about 98 per cent. If acid of higher concentration than this is required, acid of 97 to 98 per cent, strength can be partially frozen,2 when the colourless prisms which separate contain 99-5 to 100 per cent. H2S04 and constitute the frequently so-called, but misnamed, monohydrate. Owing to the success of the contact process for the preparation of sulphur trioxide and of fuming sulphuric acid, the production of highly concentrated sulphuric acid has been rendered so simple a matter that concentration of the lead chamber acid is of diminished importance. The main value of the chamber process lies in its economical production of a not necessarily very concentrated acid. There are indications, however, that by a suitable combination of the two processes, an even more economical production of concentrated acid may be obtainable (see p. 162). 

Although the commercial manufacture of sulphur trioxide and sulphuric acid by the catalytic process has attained success only in comparatively recent years, a patent was acquired in 1831 by P. Phillips of Bristol for the production of sulphuric acid in this way, the suggested catalyst being platinum.4 The commencement of the twentieth century saw the main difficulties overcome and the installation of an economical and commercial process in Germany. Since then the number of plants has increased largely and various modifications have been introduced in many countries. 

It was observed that the presence of sulphuric acid promotes the hydrolysis of esters (e.g. [104,107,109]). The rate of hydrolysis is for the most part significantly lower than the esterification rate. Moreover, as already discussed above, in addition to the main reaction producing alcohol and nitrating acid, the hydrolysis process is generally accompanied by side reactions. Acids other than sulphuric, or perchloric [104], e.g. acetic [106] or phosphoric, if present in the esterifying mixture, hydrolyse esters to a markedly smaller extent than sulphuric acid. The acid make up of an esterification mixture in industry is established experimentally. Economic factors also plays a part here. 

Such evaluation should be adopted in all the simpler preparations. In this way the student will become acquainted with the elements of costing which play such an important part in his later life in the factory. He should hardly wait until he enters the factory to appreciate the cost of such common substances as sulphuric acid, benzene, aniline, naphthalene he should be able to estimate roughly the cost of derivatives such as dinitrobenzene, p-nitroaniline, etc. Even should he not take up the industrial side of his profession, he should be acquainted with the relative value of the more common products, and trained to decide for himself whether, for example, it would be more economical to extract with ether or benzene, taking into consideration the relative efficiencies of the two processes. 

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