Hydrolyzate conditioning

The flowsheet of the pretreatment and hydrolyzate conditioning is presented in Figure 15.11. 

Cooking and frying oils are used at high temperatures, often in the presence of hydrolyzing conditions, namely water and steam. Hydrolysis causes free fatty acid development, which results in more acidic flavors. Some products that are eaten shortly after preparation do not need as stable a frying oil as other foods that are packaged and require an atmospheric shelf life of several weeks. Products that... 

Activity and selectivity of monometallic Ag catalysts can be controlled by the preparation conditions leading to micro- and meso- to macroporous catalysts which are active and selective in the hydrogenation of crotonaldehyde. In Ag catalysts modified by a second metal, bimetallic sites exhibiting surface polarity and Ag particles in close contact with a partially reduced early transition metal or a rare earth element, or Ag species stabilized and incorporated in these oxides were concluded to be the active species in the working state of these catalysts. Simultaneous introduction of both metals during the sol-gel process under optimized hydrolyzing conditions could further increase the metal-promoter interaction and lead to well-tailored new hydrogenation catalysts. 

The nucleophilic attack of the carbonyl group of an amide under hydrolyzing conditions is a very nice example of medium-assisted reaction (Menger and Fei, 1994). Long-chain ammonium amides could be hydrolyzed... 

FIGURE 10.15 Separation of 17-component amino acid hydrolyzate. Conditions Column, Dionex AS-8 gradient. Peaks (25 nmol each, except 12.5 nmol for cystine) a, arginine b, lysine c, threonine d, alanine e, glycine f, serine g, valine h, proline i, isoleucine j, leucine k, methionine 1, histidine m, phenylalanine n, glutamic acid o, aspartic acid p, cystine and q, tyrosine. (Reprinted from Welch, L.E., LaCourse, W.R., Mead, D.A., Jr., and Johnson, D.C., Ana/. Chem., 61, 555, 1989.)... 

The formation of 2.6-octadienol (27) by the reaction of 1,3-butadiene with water has attracted attention as a novel method for the commercial production of n-octanol, which has a considerable market. However, the reaction of water under the usual conditions is very sluggish. The addition of CO2 facilitates the telomerizdtion of water and 2,6-octadienol (27) is obtained as a major pro-duct[31]. In the absence of CO2, only 1,3,7-octatriene (7) is formed. Probably octadienyl carbonate is formed, which is easily hydrolyzed to give 27. A com-... 

Attack on the electrophilic C-2 may occur as in the 2-aminothiazoles series, which probably explains the rearrangements observed in acidic medium (121, 711, 712, 723, 724), in aqueous medium with NaOAc (725), or with aqueous NaHCOj (725) (Scheme 232). That the initial attack probably involves the C-2 atom is substantiated by the fact that this rearrangement occurs under extremely mild conditions for 2-iinino-3-substituted-5-nitro-4-thiazolines (725). As the whole mechanism proposed (see p. 92) is reversible, when imino derivatives are submitted to such rearrangement conditions the rearrangement is expected to occur faster if steric interaction between 3- and 4-substituents exists in the 2-imino isomer. Another reaction may occur in acidic medium phenylimino-2-bipheny]-3,4-4-thiazoline hydrolyzed with hydrochloric acid gives the corresponding 4-thiazoline-2-one and aniline (717). 

Some of these compounds are used as potential intermediates for the preparation of 4,7-dioxo-4,5,6,7-tetrahydrothiazolo[4,5d]pyridazines (78). The diesters (77) are hydrolyzed under appropriate conditions to free acids (79), whose monopotassium salts (80) yield the cyclic anhydrides (81) under the influence of thionylchloride. Pyrolysis of 79, Rj = a-thienyl, results in its decarboxylation to 82. 

The Stephen s method allows the reduction of nitriles by stannous chloride in acid medium. If the amine chlorhydrate initially formed is hydrolyzed, the corresponding aldehyde is obtained (37, 91). Harington and Moggridge (37) have reduced 4-methyl-5-cyanothiazole by this method (Scheme 23). However, Robba and Le Guen (91) did not obtain the expected products with 4.5-dicyanothiazole and 2-methyl-4,5-dicyanothiazole. These compounds have been reduced with diisobutyl-aluminium hydride with very low yields (3 to 6%) (Scheme 24). In other conditions the reaction gives a thiazole nitrile aldehyde with the same yield as that of the dialdehyde. 

Nitrile groups m cyanohydrins are hydrolyzed under conditions similar to those of alkyl cyanides Cyanohydrin formation followed by hydrolysis provides a route to the preparation of a hydroxy carboxylic acids... 

The reaction is used for the chain extension of aldoses in the synthesis of new or unusual sugars In this case the starting material l arabinose is an abundant natural product and possesses the correct configurations at its three chirality centers for elaboration to the relatively rare l enantiomers of glucose and mannose After cyanohydrin formation the cyano groups are converted to aldehyde functions by hydrogenation m aqueous solution Under these conditions —C=N is reduced to —CH=NH and hydrolyzes rapidly to —CH=0 Use of a poisoned palladium on barium sulfate catalyst prevents further reduction to the alditols... 

This reaction has been used m an imaginative way to determine the ring size of glycosides Once all the free hydroxyl groups of a glycoside have been methylated the glycoside is subjected to acid catalyzed hydrolysis Only the anomeric methoxy group IS hydrolyzed under these conditions—another example of the ease of carbocation for matron at the anomeric position... 

Carbamates such as Aldicarb undergo degradation under both aerobic and anaerobic conditions. Indeed the oxidation of the sulfur moiety to the sulfoxide and sulfone is part of the activation of the compound to its most potent form. Subsequent aerobic metaboHsm can completely mineralize the compound, although this process is usually relatively slow so that it is an effective iasecticide, acaricide and nematocide. Anaerobically these compounds are hydrolyzed, and then mineralized by methanogens (61). 

Hexafluorophosphoric Acid. Hexafluorophosphoric acid (3) is present under ambient conditions only as an aqueous solution because the anhydrous acid dissociates rapidly to HF and PF at 25°C (56). The commercially available HPF is approximately 60% HPF based on PF analysis with HF, HPO2F2, HPO F, and H PO ia equiUbrium equivalent to about 11% additional HPF. The acid is a colorless Hquid which fumes considerably owiag to formation of an HF aerosol. Frequently, the commercially available acid has a dark honey color which is thought to be reduced phosphate species. This color can be removed by oxidation with a small amount of nitric acid. When the hexafluorophosphoric acid is diluted, it slowly hydrolyzes to the other fluorophosphoric acids and finally phosphoric acid. In concentrated solutions, the hexafluorophosphoric acid estabUshes equiUbrium with its hydrolysis products ia relatively low concentration. Hexafluorophosphoric acid hexahydrate [40209-76-5] 6 P 31.5°C, also forms (66). This... 

The extent of the initial hydrolysis depends on temperature and how the water is added. Hydrolysis is reduced at slower addition rates and lower temperatures. The hydrolysis subsequent to the initial fast reaction is slow, presumably because part of the acid is converted to fluorosulfate ions which hydrolyze slowly even at elevated temperatures. The hydrolysis in basic solution has also been studied (17). Under controlled conditions, hydrates of HSO F containing one, two, and four molecules of water have been observed (18,19). 

The vinyl ether in the latter part of the equation is copolymetized with tetrafluoroethylene, and then the sulfonyl fluoride group is hydrolyzed under basic conditions in order to produce the ion-exchange membrane (44—46). 

Plasteins ate formed from soy protein hydrolysates with a variety of microbial proteases (149). Preferred conditions for hydrolysis and synthesis ate obtained with an enzyme-to-substrate ratio of 1 100, and a temperature of 37°C for 24—72 h. A substrate concentration of 30 wt %, 80% hydrolyzed, gives an 80% net yield of plastein from the synthesis reaction. However, these results ate based on a 1% protein solution used in the hydrolysis step this would be too low for an economical process (see Microbial transformations). 

Eor the purpose of quantitative analysis, formamide can be hydrolyzed under basic conditions to alkaU formate and ammonia that can be deterruined by conventional methods. 

Tetravalent lead is obtained when the metal is subjected to strong oxidizing action, such as in the electrolytic oxidation of lead anodes to lead dioxide, Pb02 when bivalent lead compounds are subjected to powerful oxidizing conditions, as in the calcination of lead monoxide to lead tetroxide, Pb O or by wet oxidation of bivalent lead ions to lead dioxide by chlorine water. The inorganic compounds of tetravalent lead are relatively unstable eg, in the presence of water they hydrolyze to give lead dioxide. 

MAA and MMA may also be prepared via the ammoxidation of isobutylene to give meth acrylonitrile as the key intermediate. A mixture of isobutjiene, ammonia, and air are passed over a complex mixed metal oxide catalyst at elevated temperatures to give a 70—80% yield of methacrylonitrile. Suitable catalysts often include mixtures of molybdenum, bismuth, iron, and antimony, in addition to a noble metal (131—133). The meth acrylonitrile formed may then be hydrolyzed to methacrjiamide by treatment with one equivalent of sulfuric acid. The methacrjiamide can be esterified to MMA or hydrolyzed to MAA under conditions similar to those employed in the ACH process. The relatively modest yields obtainable in the ammoxidation reaction and the generation of a considerable acid waste stream combine to make this process economically less desirable than the ACH or C-4 oxidation to methacrolein processes. 

The rare-earth nitrides do not have any technical appHcations. These are high melting compounds but are hydrolyzed easily by moisture and are not stable under normal atmospheric conditions. 

The most commonly used polymers are partially hydrolyzed polyacrylamides (32). The optimum degree of hydrolysis depends on the apphcation, injection water composition, and reservoir conditions (33,34). More salt-tolerant acrylamide copolymers may permit this technology in higher salinity injection water (35). Eield apphcations of cross-linked xanthan gum have also been reported (36). 

Although reasonably stable at room temperature under neutral conditions, tri- and tetrametaphosphate ions readily hydrolyze in strongly acidic or basic solution via polyphosphate intermediates. The hydrolysis is first-order under constant pH. Small cycHc phosphates, in particular trimetaphosphate, undergo hydrolysis via nucleophilic attack by hydroxide ion to yield tripolyphosphate. The ring strain also makes these stmctures susceptible to nucleophilic ring opening by other nucleophiles. 

Hydrolysis and Polycondensation. One of the key properties of polyamides relates to the chemical equihbrium set up when the material is polymerized. The polymerization of nylon is a reversible process and the material can either hydrolyze or polymerize further, depending on the conditions. 

The recovery of fiber from broke (off-specification paper or trim produced in the paper mill) is compHcated by high levels of urea—formaldehyde and melamine—formaldehyde wet-strength resin. The urea resins present a lesser problem than the melamine resins because they cure slower and are not as resistant to hydrolysis. Broke from either resin treatment may be reclaimed by hot acidic repulping. Even the melamine resin is hydrolyzed rapidly under acidic conditions at high temperature. The cellulose is far more resistant and is not harmed if the acid is neutralized as soon as repulping is complete. 

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