Sulphuric acid process

Diethyl ether may be prepared from ethyl alcohol by the sulphuric acid process. A mixture of alcohol and sulphuric acid in equimolecular proportions is heated to about 140° and alcohol is run in at the rate at which the ether produced distils from the reaction mixture. Ethyl hydrogen sulphate (or ethyl sulphuric acid) is first formed and this yields ether either by reacting directly with a molecule of alcohol or by the formation and alcoholysis of diethyl sulphate (I) ... 

Downstream from the 3rd bed, the gas is cooled and passed to an intermediate absorption tower, in which the S03 formed is absorbed in recirculating sulphuric acid. The cold and practically S03-free process gas is reheated to 380-440°C and returned to the converter, where the remaining SO2 is converted to S03 in a 4th catalyst bed. The rest of the S03 is subsequently recovered in a final absorption tower before the process gas, containing a small fraction of unconverted S02, is emitted through the stack. The combustion air is dried with the 98 wt% product acid in order to avoid corrosion and acid mist problems in the plant. The sulphuric acid process normally operates close to atmospheric pressure with the combustion air blower dimensioned just for compensation of the pressure drop through the plant. 

In the leaching processes, large volumes of liquid have to be handled, and the mother liquors contain large amounts of salts in soln. much potassium chloride is rendered less useful since these liquors are boiled down and utilized in other ways— principally as fertilizers. The mother liquors also yield rubidium alum. The cost of the operation, small as it is, does not enable potassium sulphate to be prepared of a sufficient degree of purity to enable it to displace the potassium chloride and sulphuric acid process which can be made to yield almost the theoretical amount of sulphate. Consequently, most of the schonite—natural or artificial—is sold as a fertilizer. 

Fig. 1.3. Sulphuric acid process for the recovery of rare earths from monazite [2].

Quartering.—This designation is applied to the parting with nitric acid mentioned above, although it is also employed to describe the sulphuric-acid process. Usually, the gold-silver alloy is made to contain 2 parts of gold to 5 parts of silver. It is granulated, and boiled with nitric acid. The silver solution produced is either worked up into lunar caustic, or precipitated as chloride by addition of sodium chloride, and then reduced to metal. 

A modification of the sulphuric acid process has been patented (1) when applied to a mixture of mono-nitrotoluenes and paraffin hydrocarbons. The nitration of the toluene is carried on carefuUy so as to take it only as far as the mononitrotoluene. The mono-nitrotoluene is dissolved in sulphuric acid, but any paraflShs that may be present will not dissolve, and will form a separate layer. A separation of these two layers and the subsequent nitration of the sulphuric acid solution of mononitrotoluene yields a very high grade TNT. Thus a toluene containing a comparatively large percentage of paraffins may be utilized in the manufacture of TNT. 

A typical example of the application of ceramic membranes in chemical industry is the cleaning of mono ethanol amine. Mono ethanol amine (MEA) is used for the absorption of H2S from acid gasses but is polluted during this process by various organic compounds. Filtration of the MEA over 0.2 pm HIC ceramic membranes at an average flux of 32 1/m h produces a clean, transparent yellow liquid, free of solids. Filtration temperature is 37°C, pH is about 11.5. Tests lasted successfully for over 700 h. Another example is the filtration of Ti02 from a waste stream in the so-called sulphuric acid process... 

P.A. Riveros, J.E. Dutrizac, E. Benguerel and G. Houlachi, The Recovery of Iron From Zinc Sulphate-Sulphuric Acid Processing Solutions by Solvent Extraction or Ion Exchange, Min. Pro. Ext. Met. Rev.. Vol. 18,1998,105-145. 

A. Philips, The modem sulphuric acid process. Chemistry in Britain, 13, 471, 1977. 

First World War, were based on the oxidation of acetaldehyde derived from either acetylene or fermentation ethanol. The latter could well return to favour in countries such as Brazil (section 12.7.1.). After the Second World War, fermentation ethanol gave way to synthetic ethanol, via the direct hydration of ethylene. (Synthetic ethanol made by the sulphuric acid process had already made some inroads in the U.S.A.). From 1960 onwards, the Wacker oxidation of ethylene added a further option for acetaldehyde manufacture. 

After isobutene removal, n-butenes in the mixture with butanes may be converted to 2-butanol by the old two-stage sulphuric acid process or by using an acidic ion-exchange resin catalyst. Essentially all 2-butanol so produced is converted to 2-butanone by dehydrogenation (cf. isopropanol... 

Solid/separation properties are superior to sulphuric acid processes. 

At this stage, the reader should compare the unit operations of the ammonia and sulphuric acid processes. Although some processes have special requirements, it should already be clear that the chemical engineer can apply his experience of designing heat transfer equipment for ammonia production to similar sorts of problems in nylon, drug or refrigerant production. The links with the food industry is the next subject. 

The importance of heat transfer to chemical engineering will be illustrated by returning briefly to Case study 1. In the sulphuric acid process there are three vital heat transfer operations ... 

Figure 7.7 Single absorption sulphuric acid process... 

According to Lant Carpenter, some 75 per cent, of solid fatty acids may be obtained from tallow by the sulphuric acid process, owing to the conversion of a considerable quantity of oleic acid into isoleic acid (vide p. 12), but in the process a considerable proportion of black pitch is obtained. C. Dreymann has recently patented (Eng. Pat. 10,466, 1904) two processes whereby the production of any large amount of hydrocarbons is obviated. In the one case, after saponification with sulphuric acid, the liberated fatty acids are washed with water and treated with an oxide, carbonate, or other acid-fixing body, e.g., sodium carbonate, prior to distillation. In this way the... 

Most of the sulphur we use is imported and is in the liquid form. It is of the bright or low-ash form. There is another darker or high-ash form which contains a greater proportion of carbon-based materials. The higher carbonaceous content can degrade the catalyst and cause acid mist later in the sulphuric acid process. This problem can be resolved by inserting a gas filter before the conversion process. 

International Standard, ISO 8080 (1985). Specification for Anodic Coating of Titanium and Titanium Alloys by the Sulphuric Acid Process. 

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