Liquid-phase reaction studies

A number of laboratory studies have been recorded recently aimed at characterizing the kinetics of both the chemical reaction and crystallization steps in a reaction crystallization process. Examples of liquid phase reactions studied for this purpose are the crystallization of salicylic acid from aqueous solutions of sodium salicylate using dilute sulphuric acid (Franck et al, 1988) and the crystallization of various calcium phosphates by reacting equimolar aqueous solutions of calcium nitrate and potassium phosphate (Tsuge, Yoshizawa and Tsuzuki, 1996). Several aspects of crystal size distribution control in semi-batch reaction crystallization have been considered by Aslund and Rasmuson (1990) who studied the crystallization of benzoic acid by reacting aqueous solutions of sodium benzoate with HCl. An example of crystallization arising from a gas-liquid reaction in an aqueous medium is the precipitation of calcium carbonate from the reaction between calcium hydroxide and CO2 (Wachi and Jones, 1995). 

Schmid and Heinola [J. Am. Chem. Soc., 90 (131), 1968] have studied the liquid phase reactions of 1-phenylpropyne (A) and 2,4-di-nitrobenzenesulfenyl chloride (B) in chloroform solution at 51° C. The primary products of the reaction are l-phenyl-t/ams-l-chloro-2-(2, 4 di-nitrophenylthio) propene (C) and 1-phenyl-tnms-2-chloro-l-(2, 4-dinitrophenylthio) propene (D). The reaction stoichiometry may be... 

Hydroxylation of benzene with hydrogen peroxide in the presence of solid zeolite catalyst (titan-silicate-zeolite) was chosen by Radoiu et al. [57] as a model heterogeneous liquid-phase reaction for study of microwave effects, Scheme 10.12. 

Floyd TM, Schmidt MA, Jensen KF (2005) Silicon micromixers with infrared detection for studies of liquid-phase reactions. Ind Eng Chem Res 44 2351-2358... 

Suppose the liquid-phase reaction A + j/B B -> products was studied in a batch reactor at two temperatures and the following results were obtained ... 

In pulp and paper processing, anthraquinone (AQ) accelerates the delignification of wood and improves liquor selectivity. The kinetics of the liquid-phase oxidation of anthracene (AN) to AQ with NO2 in acetic acid as solvent has been studied by Rodriguez and Tijero (1989) in a semibatch reactor (batch with respect to the liquid phase), under conditions such that the kinetics of the overall gas-liquid process is controlled by the rate of the liquid-phase reaction. This reaction proceeds through the formation of the intermediate compound anthrone (ANT) ... 

A liquid-phase reaction, A products, was studied in a constant-volume isothermal batch reactor. The reaction rate expression is (-rA) = kAcA, and k = 0.030 min 1. The reaction time, t, may be varied, but the down-time, td, is fixed at 30 min for each cycle. If the reactor operates 24 hours per day, what is the ratio of reaction time to down-time that maximizes production for a given reactor volume and initial concentration of A What is the fractional conversion of A at the optimum ... 

In a batch-reactor study of the kinetics of a liquid phase reaction A -> products, the following data were obtained ... 

In general, liquid-phase reactions (Sc > 1) and fast chemistry are beyond the range of DNS. The treatment of inhomogeneous flows (e.g., a chemical reactor) adds further restrictions. Thus, although DNS is a valuable tool for studying fundamentals,4 it is not a useful tool for chemical-reactor modeling. Nonetheless, much can be learned about scalar transport in turbulent flows from DNS. For example, valuable information about the effect of molecular diffusion on the joint scalar PDF can be easily extracted from a DNS simulation and used to validate the micromixing closures needed in other scalar transport models. 

Although most of the studies of acetylation of wood have used liquid phase reactions, there have been some reports of vapour phase reactions. Arora etal. (1979, 1980) and... 

Abstract More than a decade has passed since fullerenes became avaUahle to researchers in almost all fields of science. The explosive development of study on the chemical functionalization of fullerenes has led to a wide variety of fullerene derivatives. However, most of these reactions have been carried out in the liquid phase, and curiously enough the solid-state reaction (or solid-solid reaction) of fullerenes has been developed only in recent years. This chapter focuses on the solid-state reaction of fullerenes, particularly the reaction which was conducted under what is called high-speed vibration milling conditions. It will be shown how this reaction technique is pertinent for the creation of fullerene derivatives with novel structures, and how efficient this method is for certain reactions compared with the liquid-phase reaction. 

One of the early specialized techniques used for the study of radical reactions was the rotating sector method. The use of this technique (Fig. 6) for determining reaction kinetics was demonstrated by Melville for the gas phase polymerization of methyl methacrylate, and later by Bartlett and Swain for the liquid phase reaction, and by Carlsson and Ingold for tin hydride reductions. ... 

For the liquid phase kinetic studies of esterification, with a few exceptions [402,435—437] only the standard (non-porous, see Sect. 1.2.5) ion exchangers were used. The macroreticular (porous) ion exchangers with a large inner surface area are prefered for vapour phase reactions, especially in more recent studies [436—443]. The authors claimed that diffusion was not the limiting process under their conditions. This observation cannot be generalised, however, and even with vapour phase reactions and macroreticular polymers, the possibility of transport limitations through the pores or the polymer mass cannot be excluded a priori. 

By writing molar component balances for gas and crystallite phases, assuming Henry s law equilibrium between these phases and applying exponential rate decay, the equilibrium model (model a) is obtained (13). All parameters in the model can be measured or estimated, independent of reaction studies, with the exception of Mi and M2y which are obtained from the observed rate decay. The Henry s law constant H was estimated from a liquid-phase equilibrium study. A model involving diffusional limitations within the crystallites has been developed by Tan and Fuller (6) and is not discussed here. 

In the present study, liquid-phase reactions over both NaY and KY showed significant production of SAL compared to the gas-phase studies. The higher temperature of the liquid-phase work might... 

The stoichiometry of the reactions studied and the results achieved using different catalysts are contained in Tables 2-5. It has to be remarked the strong decrease in reactivity observed in these liquid phase reactions when moving from tri to monodirectional zeolites, the latest being much more inefficient as catalysts for the reactions tested. 

The application of HTE techniques for studying liquid-phase reactions has been demonstrated for several catalytic reactions. Good results are obtained when the design of the catalyst library, typically a small, full-factorial library of 24 catalysts, is coupled to an extensive literature survey that pinpoints the major variables of the reaction system under study. Combining less important parameters into the reduced and optimised catalyst library can be used to further fine-tune the catalyst. 

These examples reveal the wide applicability of HTE techniques in studying catalyst systems for liquid-phase reactions. 

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