Emulsions esterification reactions

Quaternary oxalkylated polycondensates can be prepared by esterification of an oxalkylated primary fatty amine with a dicarbonic acid. An organometallic titanium compound is used as a catalyst for condensation [842]. The reaction product is then oxalkylated in the presence of a carbon acid [841], These polycondensates can be used as demulsifiers for crude oil emulsions and as corrosion inhibitors in installations for the production of natural gas and crude oil they can and also be used in processing. 

The amounts of DBSA used were also found to affect the equilibrium position (Table 13.6). Each equilibrium position was confirmed by conducting both esterification of the carboxylic acid with the alcohol and hydrolysis of the ester. Table 13.6 clearly shows that increase of the amount of DBSA resulted in decrease of the yield of the ester at the equilibrium position. This result may be attributable to the size difference of the emulsion droplets that were formed by the hydrophobic substrates and the surfactant in water. As the amount of the surfactant-type catalyst increases, the size of each droplet may decrease, because the emulsion system may become a microemulsion system where the substrates are solubilized in water by a large amount of the surfactant. In fact, while 10 mol% DBSA gave the white turbid mixture, the reaction mixture was almost clear in the presence of 200 mol% DBSA, indicating that the size of the droplets became smaller. The smaller the droplets, the larger the sum of surface area of the droplets. As a result. 

Unlike in conventional emulsion polymerization processes, the droplets can be regarded as individually acting nanoreactors, suitable for a wide variety of different reactions. Organic reactions (esterifications) [4, 5], crystallization processes [6-9] and sol-gel reactions [10], to name only few, can be conducted in... 

Acylation reactions of cellulose with tty acids have been accomplished in the absence of solvent with the help of a co-reagent and the solvent exchange technique as a pretreatment for cellulose. The latter included soaking of cellulose with water, followed by washing with ethanol and finally with the tty acid. In the present work, we propose a new technique for the synthesis of cellulose and starch tty esters by esterification with fatty acids without the use of co-reagent or organic solvent. This technique passes through an emulsion to accomplish an intimate contact betwe the polysaccharide and the fatty acid. 

Addition polymerizations proceed either by free-radical or by ionic mechanisms and can be carried out either in bulk solution, i.e., on the neat monomer, or in suspension or emulsion. Each method has its own advantages and disadvantages. The choice of method of polymerization also depends to a very great extent both on the nature of the monomer and on the product desired. Polycondensations or step-reactions proceed according to the mechanism demanded by the reactive functional groups. Some common step-reactions are esterification, amidification, and urethane formation, as well as ring-opening or transesterification. 

Fatty acid esters of propane-1,2-diol (E477), also known as propylene glycol (11-62), and fatty acid esters of polyethylene glycol 8000 (11-63, E1521, the HLB value depends on the degree of ethoxylation) are obtained by direct esterification or by enzymatic reactions. These substances are used for oU-in-water emulsions (o/w emulsions for short). 

Virtually supeiimposable conversions vs. time result from esterifications conducted at 25 C in w/o microemulsion catalyzed by DBSA or in a w/o emulsion catalyzed by NaDBSA/7.4N H2SO4. Figure 2. Apparently ion exchange can rapidly occur between the aqueous 7.4N H2SO4 phase and the NaDBSA to give conditions at the reaction site similar to those in the o/w microemulsion with just the DBSA catalyst. Neither NaDBSA or 7.4N H2SO4 alone are effective catalysts under these conditions. 

Two concurrent reaction pathways can account fOT the observations. One is proposed to occur in the hydrophobic phase and the other at the interfacial boundary between the hydrophobic and hy ophilic phases. Figure 6. Esterification is consider to occur at both sites so the forward rate constant will be conq)osed of the rate constants from both reactions (kf = kf + kf ). Hydrolysis (k,), on the other hand, is considered to occur primarily in solution in the hydrophobic phase whae it is limited by the solubility of water in the hydrophobic m a, as determined by the constant K2. The interface consists of a boundary between the hydrophobic and the polar regions of w/o emulsion particles, or the micelles in w/o microemulsions. In the s/i dispersions the interface is between the surface of the cation exchange resin particles and the hydrophobic medium. In either case catalysis at the interface is considered essentially irreversible while the process in the hydrophobic phase is a typical reversible esterification in solution defined by Ki in equation 1. 

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