Production spent acid regeneration

Sulfonated EPDMs are formulated to form a number of rubbery products including adhesives for footwear, garden hoses, and in the formation of calendered sheets. Perfluori-nated ionomers marketed as Nation (DuPont) are used for membrane applications including chemical-processing separations, spent-acid regeneration, electrochemical fuel cells, ion-selective separations, electrodialysis, and in the production of chlorine. It is also employed as a solid -state catalyst in chemical synthesis and processing. lonomers are also used in blends with other polymers. 

This chapter has provided study estimate level investment and production cost estimates for sulfur burning and metallurgical type sulfuric acid plants. Spent acid regeneration type acid plants are expected to have slightly higher investment costs than sulfur burning type acid plants. 

Because sulfur suppHes, either as elemental sulfur or by-product sulfuric acid, have grown owiag to iacreased environmental awareness, demand for sulfur has decreased ia some consuming iadustries for the same reason. Industries such as titanium dioxide productions, which traditionally utilized sulfuric acid, have concerted to more environmentally friendly processes. In addition, many consumers who contiaue to use sulfuric acid are puttiag an emphasis on regenerating or recycling spent acid. 

Fig. 5.1. Spent sulfuric acid regeneration flowsheet. H2S04(f) in the contaminated spent acid is decomposed to S02(g), 02(g) and H20(g) in a mildly oxidizing, 1300 K fuel fired furnace. The furnace offgas (6-14 volume% S02, 2 volume% 02, remainder N2, H20, C02) is cooled, cleaned and dried. It is then sent to catalytic S02 + Vi02 —> S03 oxidation and H2S04 making, Eqn. (1.2). Air is added just before dehydration (top right) to provide 02 for catalytic S02 oxidation. Molten sulfur is often burnt as fuel in the decomposition furnace. It provides heat for H2S04 decomposition and S02 for additional H2S04 production. Tables 5.2 and 5.3 give details of industrial operations.

Boron trifluoride catalyst may be recovered by distillation, chemical reactions, or a combination of these methods. Ammonia or amines are frequently added to the spent catalyst to form stable coordination compounds that can be separated from the reaction products. Subsequent treatment with sulfuric acid releases boron trifluoride. An organic compound may be added that forms an adduct more stable than that formed by the desired product and boron trifluoride. In another procedure, a fluoride is added to the reaction products to precipitate the boron trifluoride which is then released by heating. Selective solvents may also be employed in recovery procedures (see Catalysts,regeneration). 

The last reaction cited above as shown is very effectively catalyzed by bacterial action but is very slow chemically by recycling the spent ferrous liquors and regenerating ferric iron bacterially, the amount of iron which must be derived from pyrite oxidation is limited to that needed to make up losses from the system, principally in the uranium product stream. This is important if the slow step in the overall process is the oxidation of pyrite. The situation is different in the case of bacterial leaching of copper sulfides where all the sulfide must be attacked to obtain copper with a high efficiency. A fourth reaction which may occur is the hydrolysis of ferric sulfate in solution, thus regenerating more sulfuric acid the ferrous-ferric oxidation consumes acid. 

Spent 2,2,6,6-tetramethyl-l-oxopiperidinium can be regenerated directly at a platinum anode in aqueous acetonitrile and aldehyde products do not undergo further oxidation to the carboxylic acid [37]. Either of the two racemic quinolyl-l-oxyls 4 functions better as catalyst for the oxidation of primaiy and secondary al-kanols, but the chiral forms do not achieve selective oxidation of one enantiomer of... 

While several studies have compared various metal oxides for decarboxylative condensation reactions of acids and aldehydes, most were limited in scope due to the low conversions and/or partial pressures employed. In particular, the detrimental effects of water, often present in the feeds and always a product of the reactions, have usually been ignored. Regenerability of spent catalysts has also been given scant attention. 

Subsequently, instead of the sodium salt, the free sulfonic acid [149] is precipitated by addition of sulfuric acid or recycled mother liquor, followed by cooling. The mother liquor, which remains after filtering off the product, can be supplied directly to existing plants for regeneration of spent sulfuric acid. 

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