Secondary impregnation

Fig. 3.9 Secondary impregnation workflow showing the precursor preparation station, support preparation, impregnation station, washing station, thermal processing hardware, and impregnated catalyst array.

Uses. Nickel nitrate is an intermediate in the manufacture of nickel catalysts, especially those that are sensitive to sulfur and therefore preclude the use of the less expensive nickel sulfate. Nickel nitrate also is an intermediate in loading active mass in nickel—alkaline batteries of the sintered plate type (see Batteries, SECONDARY cells). Typically, hot nickel nitrate symp is impregnated in the porous sintered nickel positive plates. Subsequendy, the plates are soaked in potassium hydroxide solution, whereupon nickel hydroxide [12054-48-7] precipitates within the pores of the plate. 

A number of disinfectants apparentiy owe their activity to formaldehyde, although there is argument on whether some of them function by other mechanisms. In this category, the dmg with the longest history is hexamethylenetetramine (hexamine, urotropin) [100-97-0] which is a condensation product of formaldehyde and ammonia that breaks down by acid hydrolysis to produce formaldehyde. Hexamine was first used for urinary tract antisepsis. Other antimicrobials that are adducts of formaldehyde and amines have been made others are based on methylolate derivations of nitroalkanes. The apphcations of these compounds are widespread, including inactivation of bacterial endotoxin preservation of cosmetics, metal working fluids, and latex paint and use in spin finishes, textile impregnation, and secondary oil recovery (117). 

Unlike the cells above, which are all primary cells, this is a secondary (i.e. rechargeable) cell, and the two poles are composed in the uncharged condition of nickel and cadmium hydroxides respectively. These are each supported on microporous nickel, made by a sintering process, and separated by an absorbent impregnated with electrolyte. The charging reactions are ... 

The major dasses of antibiotics are secondary metabolic products of micro-organisms. Many were discovered by empirically screening culture filtrates or cell extracts for antimicrobial activity. A range of techniques (examples are methods using, impregnated discs, porous cylinders, cut wells, see Figure 6.2) have been used to carry out such screening. 

Fig. 11. EPR spectra of Ti3+ (at 77 K) showing the influence of Cs exchange and platinum impregnation on the intensity and g-parameters of Ti3+ signals in ETS-10 reduced in dry H2 at 673 K (signals denoted by an asterisk correspond to superoxide radical species generated by secondary reactions by Ti3+ interaction with 02) [from Bal et al. (130)].

Sodium salts of carboxylic acids, including hindered acids such as mesitoic, rapidly react with primary and secondary bromides and iodides at room temperature in dipolar aprotic solvents, especially HMPA, to give high yields of carboxylic esters.679 The mechanism is Sn2. Another method uses phase transfer catalysis.680 With this method good yields of esters have been obtained from primary, secondary, benzylic, allylic, and phenacyl halides.681 In another procedure, which is applicable to long-chain primary halides, the dry carboxylate salt and the halide, impregnated on alumina as a solid support, are subjected to irradiation by microwaves in a commercial microwave oven.682 In still another method, carboxylic acids... 

Ordinarily the chromium binds to the silica by reacting with hydroxyls on a fully hydrated surface, because chromium is impregnated aqueously onto the silica and then calcined. However, a different catalyst results if the chromium attaches instead to a surface already dehydrated by calcining. A large promotional effect, particularly on the termination rate, is obtained (76). To do this the silica is first dehydrated at 900°C, for example, then impregnated with chromium anhydrously so that the surface is not rehydrated. A secondary calcining step at some lower temperature such as 300-600°C then fixes the chromium to the silica. The method is especially effective if the support also contains titania. 

TYUYANUN1TE. An ore of uranium with the composition. Ca(U02)2 (V04)2 5 — 8H2O, which occurs in yellow incrustations as a secondary mineral. The mineral is orthorhombic, It occurs as a secondary mineral as incrustations on limestones, and as disseminated impregnations in sandstones. Found abundantly 111 the Western United Stales, at Grants, New Mexico, and in Wyoming, Utah, Colorado. Nevada, Arizona and Texas. Also at Tyuya Muyan in Turkestan, the former U.S.S.R. 

Cerium (TV) ammonium nitrate (CAN)37 and a cerium (TV) impregnated resin38 are able to catalyze the selective oxidation of secondary alcohols with sodium bromate (NaBrOi). Stoichiometric cerium bromate— CelBrCb h, prepared in situ from barium bromate and cerium (III) sulfate, is also able to perform selective oxidations of secondary alcohols.39... 

The biosynthesis of many bis-indole alkaloids has been postulated to proceed by dimerisation of appropriate precursors, and there is now a substantial amount of experimental evidence to support this hypothesis. For example, treatment of the alcohol 1 with acid gives the alkaloid yuehchukene 2, and 1 could arise biogenetically by in vivo prenylation of indole followed by enzymatic oxidation. A study of related 2-prenylated indoles has confirmed the ease with which such molecules can "dimerise". Thus, treatment of the secondary alcohol 3 in benzene with silica gel impregnated with TsOH gave a complex mixture of products from which 4 (5.1%) and 5 (2.1%) were isolated (3 is very sensitive to acid, and is easily decomposed). Treatment of the isomeric tertiary alcohol 6 with a catalytic amount of TFA in anhydrous benzene gave much higher yields of the two "dimeric" products 7 (31%) and 8 (25%). 

Until recently, the mechanism of the inhibition of light-induced yellowing was subject to speculation. However, solid state ESR and CIDEP have provided insight into the mode of inhibition by thiols (Wan, J.K.S., et al, J. Wood Chem. Technol., in press). Near-uv irradiation of unbleached and peroxide bleached thermomechanical pulp impregnated with thiols caused a rapid increase of the thiol radicals. The time resolved CIDEP spectrum, however, shows a symmetric broad band characteristic of the polarized phenoxy radical. This result suggests that thiols quench triplet generated phenoxy radicals in a secondary thermal process. 

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