Hydrolysis reactions, titanate

Another reaction of the titanate which has an important effect in waste solidification is the reaction with hydrogen ion, as in the hydrolysis reaction shown in Eq. 3 ... 

The barium bis-isopropoxide was prepared by the metal/alcohol reaction method. Appropriate amounts of these alkoxides were dissolved in a mutual solvent, such as isopropyl alcohol or benzene, for a barium and titanium molar ratio of 1 1. The solution was refluxed for 2 h with vigorous stirring before the hydrolysis reaction. Drops of deionized triply distilled water were slowly added to the solution, which was continuously stirred. The reaction was carried out in a C02-free atmosphere. The hydrated oxide was dried in vacuum or in a dry helium atmosphere at 50°C for 12 h. At this stage the oxide was a finely divided, stoichiometric titanate with 50-150 A (maximum agglomerate size <1 pm) particles and was more than 99.98% pure. TEM photomicrographs of the as-prepared and the calcined (700°C for 1 h) powders are shown in Fig. 8. The rectilinear symmetry of the particles is evident in the calcined powders. 

In this study, ZT powders were obtained from hydrolysis reactions of zirconium n-propoxide (NPZ) and titanium isopropoxide (tetra-isopropyl titanate - TPT). These reactions were performed by hydrolyzing the alkoxides separately, at the molar ratio of ZriTi of 1 1, in n-propanol, using the sol-gel process at ambient temperature (20°C) and... 

The hydrolysis reaction to obtain zirconium titanate (ZT), ZrTi04, was performed with the alkoxides zirconium n-propoxide (NPZ) (Dupont), and titanium isoproxide (TFT) Dupont, deionized water in the presence of nitric acid (Merck). The solvent used was n-propanol (Merck). 

High purity tetraalkyl titanates can be obtained by a process whereby the Hquid organic titanate esters are subjected to partial hydrolysis to form a sohd that can be separated from the reaction mass. The remaining Hquid is distilled to give a high purity product (4). For example, tetraisopropyl titanate purified in this manner contains ... 

Reaction of 2,4-diorgano-l,3-diols, such as 2-ethylhexane-l,3-diol, with TYZOR TPT in a 2 1 molar ratio gives the solvent soluble titanate complex, TYZOR OGT [5575-43-9] (4) (73). If the reaction is conducted in an inert solvent, such as hexane, and the resultant slurry is treated with an excess of water, an oligomeric hydrolysis product, also solvent-soluble, is obtained (74). 

Some elucidation of the mechanism of elastomer reinforcement is being obtained by precipitating chemically-generated fillers into network structures rather than blending badly agglomerated filler particles into elastomers prior to their cross-linking. This has been done for a variety of fillers, for example, silica by hydrolysis of organosilicates, titania from titanates, alumina from aluminates, etc. [85-87], A typical, and important, reaction is the acid- or base-catalyzed hydrolysis of tetraethylorthosilicate ... 

The alcohol exchange reaction was shown above in equation (2). The reactive alkoxy group (OR) is replaced by an alkoxy group that has less hydrolysis sensitivity (OR ). A representative example here is the use of reagents such as zirconium n-propoxide and titanium /-propoxide, both of which possess polar bonds, for the production of lead zirconate titanate films. Commonly in these processes, R OH is 2-methoxyethanol (CH3OCH2CH2OH), which is generally present as a bidentate ligand.35... 

In other examples, also involving propargyl carbonates, the parent derivative 86 was first coupled with 87 - obtained by reaction of 5-octyne with the titanium diiso-propoxide - propene complex at -50 °C, providing the titanated vinylallene 88, which on hydrolysis furnished the vinylallenes 89 in good yield [29]. Carbonate 90 in the presence of a Pd° catalyst readily decarboxylated and yielded the allenylpalladium intermediate 91, which could be coupled with various vinyl derivatives to afford the vinylallenes 92. Since X represents a functional group (ester, acetyl), functionalized vinylallenes are available by this route [30]. 

Reports of depolymerization studies carried out by Semiyen and co-workers at the University of York, UK, typically used much longer reaction times (24-72 h) for the depolymerization of PET [27], This group also reported that the titanates were ineffective catalysts for depolymerization, but it is not known whether measures to prevent titanate hydrolysis were taken. The York group also reported that the relative proportions of cyclic oligomers (trimer, tetramer, etc.) altered as the dilution ratio was changed. Similar results were seen with PBT. They have also reported fast-atom bombardment mass spectrometry (FAB-MS), LC-MS, GPC and X-ray crystallography data. The most recent work reports characterization of the cyclic oligomers from six ester and ether ester systems [29],... 

This paper describes some of our initial studies of the solution properties of sodium titanate powders in order to understand and control the metal-loading process in the preparation of a heterogeneous catalyst from the materials. The purposes of this study are 1) to define the pH and concentration regimes in which nickel is loaded onto sodium titanate as monomeric ions via ion exchange, as polymeric clusters via hydrolysis, or as discrete particles of colloidal nickel hydroxide, and 2) to characterize the catalysts with respect to the dispersion of the active metal under reaction conditions by measuring the activity and selectivity of the catalysts for a known "structure-sensitive" reaction, the hydrogenolysis of n-butane. 

Reaction of the Titanated Bislactim Ether. The titanium derivative of the bislactim ether of cyclo(L-Val-Gly) reacts with alkyl aldehydes, aryl aldehydes, and a,(3-unsaturated aldehydes highly diastereoselectively to give almost exclusively the syn addition products (eq 2). Hydrolysis with dilute Trifluo-roacetic Acid affords (2R, 35 )-(3-hydroxy-a-amino acid methyl esters. a-Amino-y-nitro amino acids can be obtained by 1,4-addition of the titanated bislactim ether to nitroalkenes and subsequent hydrolysis of the adduct. ... 

Methylation of the lithium enolates derived fn>m cyclohexen-2-one and l,l-bis(methylseleno)etiiylli-thium takes place regioselectively but requires the use of more titan one equivalent of HMPA (S equiv., 0 C, 1 h). The product consists quite exclusively of the Irons stereoistxner (99%) vrith a trace (1%) of the cis (Scheme 140, d and e). The latter can be obtained as a single stereoisomer on hydrolysis of the adduct resulting fixnn the reaction of the same organometallics with 2-methylcyclohexen-2-one... 

Scheme /. Reaction pathways for hydrolysis and cross-linking of titanates.

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