Reactions Involving Liquids

In reactions containing liquids (laminar flow), diffusion coefficients are four orders of magnitude smaller compared with those of gases [7]. Hence, passive/ active mixing of the reactants and a proper interfacial mass transfer are the main goals in the design of MSRs. 

The use of a heterogeneous catalyst not only iaciUtates its reutihzation but also provides certain heat and mass transfer limitations, which are known to modify selectivity and yield. As MSRs offer high spedfic siulaces, the influence of transfer phenomena on the overall reaction can be reduced partially or completely improving the catalytic performance. Some examples reported in the hterature are the Simiki coupling reactions, the Knoevenagel condensation reaction, enzymatic hydrolysis [10], and the esterification reaction [5]. 

MSRs can be classified according to the type of the catalytic bed and their design criteria [9]. 

This kind of reactor is easy to fabricate, commonly operates with laminar flow, and is used for catalyst screening and for the production of chemicals. However, micropacked bed reactors (MPBRs) usually have a high pressure drop dimng the passage of gases. Therefore, catalytic wall microreactors are more suitable. 

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Caution All reactions involving liquid ammonia must be... 

For reactions involving liquids and gases a quantitative calculation based on (9.1) is clearly impossible in the absence of data on the... 

Note that the reaction quotient expression /ooh similar to the equilibrium constant expression. The difference is that the reaction quotient can be calculated at any time during the reaction—at equilibrium or not at equilibrium. For reactions involving liquids or solids, the corresponding reaction quotient, Q, omits those species (the same species that are not included in the equilibrium constant expression). 

Keep in mind that we have assumed that the A S and A V from the tables are unchanged at all temperatures and pressures, that is, that they are constants. This is quite a good approximation for a reaction involving only solid phases such as this one, but you would not use it for reactions involving liquids, gases, or solutes. In general, all thermodynamic parameters do vary with T and P, so phase boundaries are in principle curved and not straight as we have assumed. However, the amount of curvature is quite small in some cases, such as this one. 

A common technique for isolating and purifying the product of a chemical reaction involves liquid-liquid extraction, or simply extraction the theory and applications are discussed in Chapter 5. This process involves transferring a solute from one solvent into another, because of its greater solubility in the second. The two solvents must be immiscible and form two distinct layers, and in general one layer is aqueous and the other is an organic solvent such as diethyl ether, hexane, or dichloromethane. Depending upon the amounts of material, the physical separation of the two immiscible phases will be performed in separatory fuimels or conical vials. 

Since the reaction involves liquids, there are no volume effect changes, so that... 

Handling, Storage, and Precautions a light sensitive, hygroscopic solid. It should be stored in a dark container under an inert atmosphere. It is extremely destructive to tissues of the mucous membranes and upper respiratory tract, eyes, and skin. It emits toxic fumes under fire conditions. It also forms explosive adducts with ammonia reactions involving liquid or gaseous ammonia should be carried out with extreme caution. Use in a fume hood. 

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