TOMAC

As expected, HTMAB made a respectable showing in these experiments. Trioctylmethylammonium chloride (TOMAC) and trioctylmetliylammonium bromide (TOMAB) outperformed all other catalysts. It was postulated that the three octyl groups were the proper length for solvation of the polymer while at the same time small enough to avoid sterically hindering the reaction. In order to determine if TOMAB could be used to catalyze PET depolymerization for more than one treatment cycle, the catalyst was recovered upon completion of one treatment and added to a second run for 60 min. Tetraethylammonium hydroxide (TEAOH) was studied as a catalyst in order to demonstrate the effect of hydroxide ion as a counterion. The percent PET conversion for the second cycle was 85.7% compared to a conversion of 90.4% for the first treatment cycle. 

In a 300-mL round-bottom flask, a 5% sodium hydroxide solution (250 mL) was heated to 80° C in a constant-temperature bath. The catalysts were added in the following amounts in separate experiments trioctylmethy-lammonium chloride (TOMAC) (0.04 g, 0.0001 mol) trioctylmethylammo-nium bromide (TOMAB) (0.045 g, 0.0001 mol) hexadecyltrimethylammo-nium bromide (HTMAB) (0.045 g, 0.0001 mol) tetraethylammonium hydroxide (TEAOH) (0.015 g, 0.0001 mol) and phenyltrimethylammonium chloride (PTMAC) (0.02 g, 0.0001 mol). PET fibers (1.98 g, 0.01 mol) were added to the mixture and allowed to react for 30, 60, 90, 150, and 240 min. Upon filtration, any remaining fibers were washed several times with water, dried in an oven at 130-150°C, and weighed. The results are shown in Table 10.1. 

Surfactants employed for w/o-ME formation, listed in Table 1, are more lipophilic than those employed in aqueous systems, e.g., for micelles or oil-in-water emulsions, having a hydrophilic-lipophilic balance (HLB) value of around 8-11 [4-40]. The most commonly employed surfactant for w/o-ME formation is Aerosol-OT, or AOT [sodium bis(2-ethylhexyl) sulfosuccinate], containing an anionic sulfonate headgroup and two hydrocarbon tails. Common cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB) and trioctylmethyl ammonium bromide (TOMAC), have also fulfilled this purpose however, cosurfactants (e.g., fatty alcohols, such as 1-butanol or 1-octanol) must be added for a monophasic w/o-ME (Winsor IV) system to occur. Nonionic and mixed ionic-nonionic surfactant systems have received a great deal of attention recently because they are more biocompatible and they promote less inactivation of biomolecules compared to ionic surfactants. Surfactants with two or more hydrophobic tail groups of different lengths frequently form w/o-MEs more readily than one-tailed surfactants without the requirement of cosurfactant, perhaps because of their wedge-shaped molecular structure [17,41]. 

Trialkyl methyl ammonium chloride [TOMAC]/w-alkanol [17,20-22]... 

Bek K, Tomac N, Delibas A, Tuna F, Tezic HT, Sungur M. (1999). The effect of passive smoking on pulmonary function during childhood. Postgrad Med J. 75(884) 339-41. 

Ejfect of temperature Luisi et al. [26] reported that the temperature markedly affected the transfer of a-chymotrypsin in a chloroform-trioctyl-methylammonium chloride (TOMAQ system. By increasing the temperature from 25-40°C, about 50% higher transfer yield was realized. No appreciable transfer of glucagone took place at room temperature, whereas transfer at 37°C was possible. These results contradict work by Dekker et al. [27], who studied the back stripping (desolubilization) of a-amylase from a TOMAC/isooctane/octanol/Rewopal HV5 system by increasing the temperature. This caused a decrease in Wo with increasing temperature and, as a result, the a-amylase was expelled from the reverse micelle phase. 

Counterion extraction Due to the relative slowness of back extraction based on the methods above, the back-extraction of proteins encapsulated in AOT reverse micelles was evaluated by adding a counterionic surfactant, either TOMAC or DTAB, to the reverse micelles [33]. This novel backward transfer method gave higher backward extraction yields compared to the conventional method. The back-extraction process with TOMAC was found to be 100 times faster than back-extraction with the conventional method, and as much as three times faster than forward extraction. The 1 1 complexes of AOT and TOMAC in the solvent phase could be efficiently removed using adsorption onto montmorillonite so that the organic solvent could be reused. 

Cetyltrimethyl ammonium bromide (CTAB) dodecyltrimethyl ammonium bromide (DTAB) tetradecyltrimethyl ammonium bromide (TTAB) trioctyl-methyl ammonium chloride (TOMAC) N-benzyl-N-dodecyl-hf-bis(2-hy-droxy ethyl) ammonium chloride (BDBAC) cetyl pyridinimn chloride (CPC) quaternary ammonium salt with carbon atoms of R ranging from 8-10 (CHj Rj N+ CL) (Aliquat 336)... 

Gluco amylase Aspergillus awamori TOMAC/Revopal HV5/n-octanol/ Extraction [57,58]... 

Carbonic anhydrase Flavodoxin Hemoglobin Hexokinase Insulin Rubredoxin Superoxide dismutase Bovine erythrocytes Megasphaera elsdenii Bovine blood Yeast Bovine pancreas M. elsdenii Bovine erythrocytes TOMAC/Rewopal HVS/octanol/ isooctane Solubilization [105]... 

Cardoso et al. [115] using the phase transfer technique studied the driving forces involved in the selective solubilization of three different amino acids having same pi, namely aspartic acid (hydrophilic), phenylalanine (slightly hydrophobic), and tryptophan (hydrophobic) in cationic TOMAC-RMs. The main driving forces involved were found to be hydrophobic and electrostatic interactions. Few other researchers have also identified that the major driving forces involved in the amino acid solubilization were hydrophobic interactions [ 114,159] and amino acid structure as well as its ionization state [160,161]. 

Dekker et al. [170] studied the extraction process of a-amylase in a TOMAC/isooctane reverse micellar system in terms of the distribution coefficients, mass transfer coefficient, inactivation rate constants, phase ratio, and residence time during the forward and backward extractions. They derived different equations for the concentration of active enzyme in all phases as a function of time. It was also shown that the inactivation took place predominantly in the first aqueous phase due to complex formation between enzyme and surfactant. In order to minimize the extent of enzyme inactivation, the steady state enzyme concentration should be kept as low as possible in the first aqueous phase. This can be achieved by a high mass transfer rate and a high distribution coefficient of the enzyme between reverse micellar and aqueous phases. The effect of mass transfer coefficient during forward extraction on the recovery of a-amylase was simulated for two values of the distribution coefficient. These model predictions were verified experimentally by changing the distribution coefficient (by adding... 

Protein partitioning and ion co-partitioning in the two-phase system was also modeled by Fraaije et al. [177]. Experiments performed on the partitioning of cytochrome C in TOMAC-octanol-isooctane provided good agreement with the model. At the pH of maximum solubiHzation, no co-partitioning of ions occurred. At pH values below and above the maximum solubiHzation pH, there was exclusion and inclusion, respectively of electrolytes. 

AOT/isooctane Periplasmic cytochrome C553 (recombinant protein) Back extraction was performed using a coimter-ionic surfactant (TOMAC). Yield and piuity were comparable to colmnn chromatography [104]... 

AN (alone or contg a small amt of dendritic inotg nitrates), 1.5% mineral oil, 1.0% dia-tomaceous earth 16.0% bagasse (or other low-d fuel such as shredded corn stalks or shredded synthetic plastics). This mixt... 

The intermediate size is dusted with a small amount of coating material (dia-tomaceous earth or kaolin) in a rotary coating drum. 

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