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Water metal salt catalysts

CONDENSOL I New is a special metal salt catalyst for water-repellent finishing with the silicone product PERSISTOL SIN. [Pg.87]

The solution (pad bath) contains one or more of the amino resias described above, a catalyst, and other additives such as a softener, a stiffening agent, or a water repeUant. The catalyst may be an ammonium or metal salt, eg, magnesium chloride or ziac nitrate. Synthetic fabrics, such as nylon or polyester, are treated with amino resias to obtaia a stiff finish. Cotton (qv) or rayon fabrics or blends with synthetic fibers are treated with amino resias to obtain shrinkage control and a durable-press finish. [Pg.331]

Pyrrohdinone forms alkaU metal salts by direct reaction with alkaU metals or their alkoxides or with their hydroxides under conditions in which the water of reaction is removed. The potassium salt prepared in situ serves as the catalyst for the vinylation of 2-pyrrohdinone in the commercial production of A/-vinylpyrrohdinone. The mercury salt has also been described, as have the N-bromo and N-chloro derivatives (61,62). [Pg.360]

Hydration and dehydration employ catalysts that have a strong affinity for water. Alumina is the principal catalyst, but also used are aluminosihcates, metal salts and phosphoric acid or its metal salts on carriers, and cation exchange resins. [Pg.2094]

To accelerate the polymerization process, some water-soluble salts of heavy metals (Fe, Co, Ni, Pb) are added to the reaction system (0.01-1% with respect to the monomer mass). These additions facilitate the reaction heat removal and allow the reaction to be carried out at lower temperatures. To reduce the coagulate formation and deposits of polymers on the reactor walls, the additions of water-soluble salts (borates, phosphates, and silicates of alkali metals) are introduced into the reaction mixture. The residual monomer content in the emulsion can be decreased by hydrogenizing the double bond in the presence of catalysts (Raney Ni, and salts of Ru, Co, Fe, Pd, Pt, Ir, Ro, and Co on alumina). The same purpose can be achieved by adding amidase to the emulsion. [Pg.68]

From the preceding discussion, it is easily understood that direct polyesterifications between dicarboxylic acids and aliphatic diols (Scheme 2.8, R3 = H) and polymerizations involving aliphatic or aromatic esters, acids, and alcohols (Scheme 2.8, R3 = alkyl group, and Scheme 2.9, R3 = H) are rather slow at room temperature. These reactions must be carried out in the melt at high temperature in the presence of catalysts, usually metal salts, metal oxides, or metal alkoxides. Vacuum is generally applied during the last steps of the reaction in order to eliminate the last traces of reaction by-product (water or low-molar-mass alcohol, diol, or carboxylic acid such as acetic acid) and to shift the reaction toward the... [Pg.61]

Although organosilanes appear to react slowly (if at all) with water alone, in the presence of acids or bases (e.g., alkali metal hydroxides), reactions to give a silanol and H2 are rapid, with bases being particularly powerful catalysts. The evolution of H2 in this type of reaction may be used as both a qualitative and a quantitative test for Si-H bonds, and the mechanism of the acid and the base hydrolysis has been discussed in detail (30,31). This hydrolytic method is not very common for the preparation of silanols that are to be isolated, because both acids and bases catalyze the condensation of silanols to siloxanes, and therefore, only compounds containing large substituents are conveniently made in this way. If an anhydrous alkali metal salt is used, a metal siloxide may be isolated and subsequently hydrolyzed to give the silanol [Eq. (10)] (32). [Pg.158]

Alternatively, esterification of carboxylic acid can be carried out in aqueous media by reacting carboxylic acid salts with alkyl halides through nucleophilic substitutions (Eq. 9.10).20 The reaction rate of alkyl halides with alkali metal salts of carboxylic acids to give esters increases with the increasing concentration of catalyst, halide, and solvent polarity and is reduced by water. Various thymyl ethers and esters can be synthesized by the reactions of thymol with alkyl halides and acid chlorides, respectively, in aqueous medium under microwave irradiation (Eq. 9.11).21 Such an esterification reaction of poly(methacrylic acid) can be performed readily with alkyl halides using DBU in aqueous solutions, although the rate of the reaction decreases with increasing water content.22... [Pg.304]

The solid base catalysts were prepared by dissolving Cs(N03)2 (Aldrich, 99%) in the minimum amount of distilled water before addition to the silica support by spray impregnation a method used to give a high dispersion of the metal salt on the support. The amount of each precursor added was calculated in order to give a 10% loading of metal on each catalyst. The catalyst was then dried in an oven overnight at 373 K. Prior to the reaction the catalyst was calcined in situ in a flow of N2 (BOC, 02 free N2) at 10 cm3 min"1 for 2 hours at 723 K. [Pg.364]

Surfactants are well known as stabilizers in the preparation of metal nanoparticles for catalysis in water. Micelles constitute interesting nanoreactors for the synthesis of controlled-size nanoparticles from metal salts due to the confinement of the particles inside the micelle cores. Aqueous colloidal solutions are then obtained which can be easily used as catalysts. [Pg.226]

The TEAF system can be used to reduce ketones, certain alkenes and imines. With regard to the latter substrate, during our studies it was realized that 5 2 TEAF in some solvents was sufficiently acidic to protonate the imine (p K, ca. 6 in water). Iminium salts are much more reactive than imines due to inductive effects (cf. the Stacker reaction), and it was thus considered likely that an iminium salt was being reduced to an ammonium salt [54]. This explains why imines are not reduced in the IPA system which is neutral, and not acidic. When an iminium salt was pre-prepared by mixing equal amounts of an imine and acid, and used in the IPA system, the iminium was reduced, albeit with lower rate and moderate enantioselectivity. Quaternary iminium salts were also reduced to tertiary amines. Nevertheless, as other kinetic studies have indicated a pre-equilibrium with imine, it is possible that the proton formally sits on the catalyst and the iminium is formed during the catalytic cycle. It is, of course, possible that the mechanism of imine transfer hydrogenation is different to that of ketone reduction, and a metal-coordinated imine may be involved [55]. [Pg.1227]

Lewis acids as water-stable catalysts have been developed. Metal salts, such as rare earth metal triflates, can be used in aldol reactions of aldehydes with silyl enolates in aqueous media. These salts can be recovered after the reactions and reused. Furthermore, surfactant-aided Lewis acid catalysis, which can be used for aldol reactions in water without using any organic solvents, has been also developed. These reaction systems have been applied successfully to catalytic asymmetric aldol reactions in aqueous media. In addition, the surfactant-aided Lewis acid catalysis for Mannich-type reactions in water has been disclosed. These investigations are expected to contribute to the decrease of the use of harmful organic solvents in chemical processes, leading to environmentally friendly green chemistry. [Pg.4]


See other pages where Water metal salt catalysts is mentioned: [Pg.140]    [Pg.7197]    [Pg.140]    [Pg.7197]    [Pg.294]    [Pg.187]    [Pg.380]    [Pg.294]    [Pg.427]    [Pg.260]    [Pg.430]    [Pg.538]    [Pg.538]    [Pg.36]    [Pg.23]    [Pg.391]    [Pg.479]    [Pg.6121]    [Pg.163]    [Pg.52]    [Pg.18]    [Pg.346]    [Pg.125]    [Pg.64]    [Pg.1035]    [Pg.12]    [Pg.394]    [Pg.210]    [Pg.233]    [Pg.295]    [Pg.449]    [Pg.7]    [Pg.11]    [Pg.123]    [Pg.85]   
See also in sourсe #XX -- [ Pg.493 ]

See also in sourсe #XX -- [ Pg.493 ]

See also in sourсe #XX -- [ Pg.6 , Pg.493 ]




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