Industrial nitration, heterogenous

The nitrate deposits are made up of several layers (Fig. 1). The ore bodies are very heterogeneous and variable in size, thickness, composition, and hardness. The overburden may include chuca a layer of unconsoHdated sand, silt, and clay, andpanqueque a layer of semiconsoHdated and porous material poody cemented by salts over poody cemented gravel. The ore composition has degraded considerably since the eady days of the industry, when it was reported that ores of up to 50% sodium nitrate were mined. There are stiU reserves that can be commercially mined well into the twenty-first century (1). 

Liquid-liquid reactions of industrial importance are fairly numerous. A list of 26 classes of reactions with 61 references has been compiled by Doraiswamy Sharma (Heterogeneous Reactions, 1984). They also indicate the kind of reactor normally used in each case. The reactions range from prosaic examples such as making of soap with alkali, nitration of aromatics to make explosives and alkylations with sulfuric acid to make improved gasoline, to some much less familiar operations. 

Heterogeneous fluid-fluid reactions are made to take place for one of three reasons. First, the product of reaction may be a desired material. Such reactions are numerous and can be found in practically all areas of the chemical industry where organic syntheses are employed. An example of liquid-liquid reactions is the nitration of organics with a mixture of nitric and sulfuric acids to form materials such as nitroglycerin. The chlorination of liquid benzene and other hydrocarbons with gaseous chlorine is an example of gas-liquid reactions. In the inorganic field we have the manufacture of sodium amide, a solid, from gaseous ammonia and liquid sodium ... 

As the nitration of cellulose is a heterogeneous reaction involving irregular esterification of some or all OH groups, the attributing of definite formula to products of nitration is not necessarily valid. The N content of any particular NC largely defines its soly other props, and consequently its industrial application. A summary of the types of NC s used in industry is as follows(Refs 43 59)... 

Nickel compounds are of great importance industrially and a review is available on the use of nickel in heterogeneous catalysis, electroplating, batteries, pigments, ceramics and hydrogen storage.76 This concerns simple aqua complexes of nickel(II) with anions such as carbonate, halide, hydroxide, nitrate and sulfate. Nickel acetate and formate find similar use, and the acetate is employed in the sealing of anodized aluminum.77 [Ni(NH3)6]Cl2 has been shown to be potentially applicable in heat pumps.78... 

In general a much wider use has been made of electrophilic substitution reactions with t-octylphenol from the reaction of diisobutene with phenol and rather less applications in the field of polymer chemistry. Thus for example, estenfication, nitration, phosphorylation, diazotisation, chlorination, sulphation, carboxylation, formylation and etherification have led to well-characterised derivatives (ref.93). Unlike t-nonylphenol, t-octylphenol [4-(1,1,3,3-tetra-methylbutyOphenoQ is a crystalline compound yielding characteristic crystalline derivatives as can be seen in the following instances. t-Nonylphenol by contrast is a mixture of sidechain isomers although predominantly a p-substituted compound. Its heterogeneity like that of many technical product undoubtedly enhances its physical properties in many of its industrial applications. Thus for... 

Subsequently, Hanson and co-workers(5,6) studied the heterogeneous mononitration of both toluene and chlorobenzene in a miniature CFSTR (45ml capacity) using nitrating acid typical of that employed in industry (15 mole % HNO3, 30 mole % H2SO4,... 

Industrial aromatic nitration, carried out heterogeneously with aqueous mixtures of nitric emd sulphuric acids as nitrating agent, is cui example of simultaneous mass transfer and chemical reaction, for the system forms two phases with the reactants distributed between them. For this type of system, either the chemical kinetics or the meuss transfer process may limit the overall rate, depending on the reaction conditions. It is not our intention here to discuss the various mathematical models... 

Other recent industrial examples include the nitration and bromination of heterocycles, where the reaction not only could be conducted more safely in flow, but also it was reported that less impurities were observed within the flow synthesis. Various examples of the Swem oxidation have been reported recently, where the products were obtained in higher selectivity than in batch reactions, even when the reactions were conducted at higher temperatmes. Furthermore, the scientific community has frequently expressed concerns about conducting reactions involving heterogeneous catalysts within flow reactors, but a recent pubhcation has shown that it is possible to handle catalyst slurry within reactors when performing hydrogenation... 

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