Weak sulfuric acid

The bottoms from the stripper (40—60 wt % acid) are sent to an acid reconcentration unit for upgrading to the proper acid strength and recycling to the reactor. Because of the associated high energy requirements, reconcentration of the diluted sulfuric acid is a cosdy operation. However, a propylene gas stripping process, which utilizes only a small amount of added water for hydrolysis, has been described (63). In this modification, the equiUbrium quantity of isopropyl alcohol is stripped so that acid is recycled without reconcentration. Kquilibrium is attained rapidly at 50°C and isopropyl alcohol is removed from the hydrolysis mixture. Similarly, the weak sulfuric acid process minimizes the reconcentration of the acid and its associated corrosion and pollution problems. 

Other synthetic methods have been investigated but have not become commercial. These include, for example, the hydration of ethylene in the presence of dilute acids (weak sulfuric acid process) the conversion of acetylene to acetaldehyde, followed by hydrogenation of the aldehyde to ethyl alcohol and the Fischer-Tropsch hydrocarbon synthesis. Synthetic fuels research has resulted in a whole new look at processes to make lower molecular weight alcohols from synthesis gas. 

Technetium can also be precipitated and weighed as nitron pertechnetate CjqHj N TcO which is precipitated at 80 °C from a weak sulfuric acid or acetic acid solution with an excess of a solution of 5% nitron in 3% acetic acid. The precipitate is washed with cold water, dried at 100 °C and weighed. Nitrate, perchlorate, permanganate, periodate, chloride, bromide, and iodide ions disturb the determination. 

Fig. 14.4 Extraction of copper and zinc from weak sulfuric acid leach solutions.

The possibility of using nitric acid as an oxidizing agent in a leaching operation is often prohibitive because many reagents used in solvent extraction are not stable in an oxidizing solution. By the AX method, however, a nitric acid (nitrate) leach solution can be converted to a weak sulfuric acid (sulfate) solution, well suited for a solvent extraction treatment. 

As stated earlier in this paper, FGD wet scrubbers can produce either calcium sulfite (the typical product) or calciiun sulfate. The DDO crystallizer is advantageous for either product. The following industrial case history describes the production of calcium sulfate dihydrate (or gypsum) product fi om an industrial in-plant weak sulfuric acid liquor using a DDO crystallizer configuration. 

Properties Crystalline solid. Decomposes at 218C. Insoluble in water soluble in hydrochloric acid, weak sulfuric acid, and sodium hydroxide solution. 

Preparation of Ethanol from Ethylene. Via Ethyl Hydrogen Sulfate Ethylene is scrubbed, purified, and piped in gaseous form direct to processing in the alcohol plant (Fig. 13-6). On entering an absorber, ethylene comes into contact with sulfuric acid of 95 per cent concentration or higher. The resulting liquid is a mixture of monoethyl and diethyl sulfate. The esters leave the bottom of the absorber and are pumped into the bottom of a hydrolyzer column along with a measured volume of water. Here the esters formed in the absorber are converted to alcohol, ethyl ether, weak sulfuric acid, and small volumes of other materials. 

The first step in manufacture of cellulose is to treat the cellulose with caustic soda (NaOH) and allow it to oxidize until the degree of polymerization is down to 200 to 400. Treatment with CSj then yields sodium cellulose xanthate, which is dissolved in aqueous NaOH. This material, called viscose, is extruded through a small slit onto a roller immersed in a tank of weak sulfuric acid and sodium sulfate, which hydrolyzes the xanthate groups, regenerating the cellulose and yielding CSj and... 

Both 25% and 65% oleum were introduced into chemical processing in search of stronger sulfonating agents. However, with the sulfonation process SO3 was used and the weak sulfuric acid by-product required disposal as a waste product. Enviromnental consideration led to large effluent treatment plants (ETPs) with consumption of lime in large quantities. As a result, heaps of waste gypsum were formed and posed solid waste disposal problem. 

Weak sulfuric acid return to sulfuric acid plant 50 °C (max)... 

High level in weak sulfuric acid tank. 

In 1919 M/s. Dharamsi Moraiji Chemical Co. Ltd. was pioneer in producing sulfuric acid in India. A Lead chamber process plant was imported on Turnkey basis from England. This produced weak sulfuric acid in the range of 50-60%. 

After a time it became obvious that we were forming weak sulfuric acid in the tower on start-up. On one occasion several days after such a start-up, we opened the drain on the case of the spare depropanizer reflux pump. Weak acid (it turned pH paper red) poured out. 

Weak acid is death to carbon steel. We investigated further. Small amounts of weak sulfuric acid were found in nearly all of the cold, low, or dead-ended locations. With traces of sulfuric acid in the lower, numerous leaks soon developed in the carbon steel tubes of the overhead condenser. This forced a shutdown. 

Strong sulfuric acid above 85 percent strength is entirely noncorrosive. As the sulfuric acid is diluted with water, it becomes exponentially more corrosive to carbon steel. Small amounts of weak sulfuric acid were carrying over into the reactor effluent line from the caustic settler. 

About 20 Sulfacid installations worldwide produce weak sulfuric acid (10-20% H2SO4) from very low concentration gases (<1.0 volume% SO2) using an activated carbon catalytic reactor where SO2 reacts with O2 and H20( ) at 30-80 °C to produce H2SO4 (Kruger, 2004). The acid is intermittently washed with water from the catalyst which produces weak sulphuric acid. The cleaned gas is discharged to the atmosphere. 

About 20 Sulfacid installations worldwide produce weak sulfuric acid (10-20% H2SO4) from wet, very low SO2 concentration gases (<1.0volume% SO2). 

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