Large-scale preparative liquid

Anhydrous sulfuric acid is a dense, viscous liquid which is readily miscible wilh water in all proportions the reaction is extremely exothermic ( 880kJmol at infinite dilution) and can result in explosive spattering of the mixture if the water is added to the acid it is therefore important always to use the reverse order and add the acid to the water, slowly and with stirring. The large-scale preparation of sulfuric acid is a major industr) in most countries and is described in the preceding Panel. 

However, the unpredictably explosive nature of CI2O in the liquid state renders this process somewhat hazardous and the best large-scale preparation is the low-temperature fluorination of CIONO2 (p. 884) ... 

The strategy for preparing gold catalysts for liquid-phase oxidation is based on environment friendly and cheap methodologies with the aim to produce 3-5 nm particles, well dispersed on carbon supports, to be applied also to large-scale preparations. 

Cyclization by addition of a side-chain carbanion to an aryne bond has been proposed as the method of choice for synthesis of the versatile 1-substituted benzocyclobutene system.7 This general procedure now has been modified to permit convenient large-scale preparations utilizing a commercially available base, a minimum amount of liquid ammonia, and distillation for isolation of the product. 

The use of ionic liquids in most applications is stiU in development. The chemical industry in Europe is showing increasing interest in them, particularly for olefin dimerizations and Friedel-Crafts reactions. A two-phase loop reactor has been designed for large-scale preparations which allows for continuous reaction, separation of the product, and recycling of the ionic liquid (Chauvin and Helene, 1995). 

Two types of columns are used. A packed column is one filled with inert, solid particles coated with a liquid stationary phase. Standard tubing is about 0.5 cm in diameter, with lengths ranging from 1 m to 20 m however, columns for large-scale preparative work may be up to 5 cm in diameter and several meters long. Commonly used solid supports are diatomaceous earth, Teflon powder, and glass beads. The stationary liquid must be chosen on the basis of the compounds to be analyzed. A more recently developed and more widely used type of column is the open-tubular or capillary column. This is prepared by coating the inner wall of the column with the stationary liquid phase. The inside diameter of a typical capillary tube is 0.25 mm, and... 

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