Regeneration method procedure

It is possible that the regeneration method succeeds by removing short chain, inactive polymer fragments, which will be soluble in the aqueous medium. Once these smaller polymer chains have been removed, the bulk of the polymer is then able to reform its preferred tertiary structure, thus restoring its catalytic activity. The aqueous nature of the procedure may also aid regeneration by... 

Rigorous scale homogenization procedures lead to continuum models for the entire DPF (Bissett, 1984 Konstandopoulos et al., 2001, 2003) exploiting (as is common in continuum descriptions) a suitable scale disparity, namely the ratio of the channel hydraulic radius to the entire DPF diameter. The smallness of this parameter is invoked to formulate a perturbation expansion of the discrete multichannel equations. The continuum multichannel description of the DPF can accommodate various regeneration methods (thermal, catalytic and N02-assisted) and can provide spatio-temporal information of several quantities of interest (e.g. filter temperature, soot mass distribution, flow distribution, etc.) as illustrated in Fig. 38. 

Most synthetically useful phosphorylating enzymes require nucleoside triphosphates as cofactors. The central importance of cofactor regeneration, and the most used regeneration methods for these cofactors, are discussed in Section 13.2.1. The end of Chapter 13 includes tabular surveys of the most important applications, classified in compound or structural classes (see Sections 13.2.2 and 13.3.3), to facilitate the search for relevant enzymes and procedures. 

The abiUty of LDH materials to regenerate their layered structure from an aqueous dispersion of their mixed-oxide form is also applied to prepare the monomer-intercalated hybrids (path 3, Fig. 6). This is called the regeneration method, which is similar to the procedure used for converting C03 "-containing LDH to other forms. 

Boron trifluoride catalyst may be recovered by distillation, chemical reactions, or a combination of these methods. Ammonia or amines are frequently added to the spent catalyst to form stable coordination compounds that can be separated from the reaction products. Subsequent treatment with sulfuric acid releases boron trifluoride. An organic compound may be added that forms an adduct more stable than that formed by the desired product and boron trifluoride. In another procedure, a fluoride is added to the reaction products to precipitate the boron trifluoride which is then released by heating. Selective solvents may also be employed in recovery procedures (see Catalysts,regeneration). 

The authors have written and revised six chapters that describe the aspects of purificatton and properties of chemical substances. In addition to detailing physical method and procedures such as crystallization, distillation, chromatography, etc, the authors also address chemical methods and procedure used in purification Including conv sion to specific derivatives or complexes and regeneration of the original material in a much-purified form. 

Methyliminodiacetic acid has been prepared by the action of methylamine on formaldehyde cyanohydrin, subsequent hydrolysis of the dinitrile with barium hydroxide, and regeneration from the barium salt with sulfuric acid.1 This method was found by the submitter to be much less satisfactory than the procedure given above. 

The amount of resin used contains about 0.012 mole of active carbodiimide. Methods for preparing this reagent, determining its carbodiimide content, and regenerating spent resin are described in the preceeding procedure (p. 95). 

A very attractive method for the preparation of nitroalkenes, which is based on the reaction with NO, has been reported. Treatment of alkenes at ambient pressure of nitrogen monoxide (NO) at room temperature gives the corresponding nitroalkenes in fairly good yields along with P-nitroalcohols in a ratio of about 8 to 2. The nitroalcohol by-products are converted into the desired nitroalkenes by dehydration with acidic alumina in high total yield. This simple and convenient nitration procedure is applied successfully to the preparation of nitroalkenes derived from various terminal alkenes or styrenes (Eq. 2.27).53 This process is modified by the use of HY-zeolites instead of alumina. The lack of corrosiveness and the ability to regenerate and reuse the catalyst make this an attractive system (Eq. 2.28).54... 

Except for those catalysts subjected to the previously mentioned conditions, which lead to irreversible transformation of the active phase and/or the support material, the HDT catalysts are regenerable [37], Through a systematic and careful procedure, the spent catalyst is unloaded from the reactor and regenerated by specialized companies. The possibility of in situ regeneration is also commercially offered and the decision, on which method would be used, is typically based on economical considerations [38],... 

A brief exposure of diacetate derivatives of aromatic aldehydes to MW irradiation on neutral alumina surface rapidly regenerates aldehydes (Scheme 6.5) [36], The selectivity in these deprotection reactions is achievable by merely adjusting the time of irradiation. As an example, for molecules bearing acetoxy functionality (R = OAc), the aldehyde diacetate is selectively removed in 30 s, whereas an extended period of 2 min is required to cleave both the diacetate and ester groups. The yields obtained are better than those possible by conventional heating methods and the procedure is applicable to compounds bearing olefmic moieties such as cinnamaldehyde diacetate [36],... 

A novel method for the electrolytic regeneration of periodate ion in oxidizing solutions has been reported.240 This procedure shows industrial promise, since it circumvents the initial, high cost of periodates. 

The regeneration of deactivated immobilized catalysts is not as easy as with conventional supported metal catalysts, where combustion of the deposited material is frequently used. Because such a procedure would destroy the organic ligands, one must resort to washing procedures. However, when this method fails, attempts must be made to recover the metal and the ligand, and to prepare a fresh catalyst. In principle, it is possible to recover the metal complexes from physically and ionically immobilized catalysts. This can also be done from covalently bound catalysts by using an easily hydrolyzable linker. 

This procedure uses readily available starting materials and in one operational step generally gives higher yields of cyclopentanecarboxaldehyde than other preparations described in the literature. Because mercuric sulfate is an expensive reactant, a method of regenerating the mercury products is given. Cyclopentanecarboxaldehyde is a useful intermediate for many cyclopentane derivatives. 

The reported procedure for the selective oxidation of natural glycosides is mild, convenient and easily reproducible. The biotransformations are performed in mildly acidic water solutions therefore, this method is complementary to other chemical approaches for the in situ regeneration of the oxidized form of TEMPO, such as sodium hypochlorite, that require alkaline pH. 

The conversion of the mixed metal oxides into LDHs has been variously referred to as regeneration, reconstruction, restoration, rehydration or the calcination-rehydration process , structural memory effect or simply memory effect . This method is usually employed when large guests are intercalated. It also avoids the competitive intercalation of inorganic anions arising from the metal salts. The procedure is more complicated than coprecipitation or ion-exchange methods, however, and amorphous phases are often produced simultaneously. 

This mechanism is of particular significance for electroanalytical methods utilizing both adsorptive accumulation and catalytic regeneration for amplifying the analytical sensitivity. In the modeling of the mass transport of the O form, the equivalent procedure as described for the mechanism (2.178) is required. The mass transport of the R form is described by the differential equation (2.189) and the boundary... 

When the resulting mixture of benzoylformic acid and (i )-mandelic acid was treated with a cell free extract of Streptomyces faecalis IFO 12964 in the presence of NADH,the keto acid can be effectively reduced to (i )-mandelic acid (Fig. 1). Fortunately the presence of A. bronchisepticus and its metabolite had no influence on the reduction of the keto acid. The regeneration of NADH was nicely achieved by coupling the reaction with reduction by formic acid with the aid of formate dehydrogenase. As a whole, the total conversion of racemic mandelic acid to the i -enantiomer proceeded with very high chemical and optical yields. The method is very simple and can be performed in a one-pot procedure [6]. 

Since in method C di(2-thienyl) ditelluride is formed as a by-product and NaBH4 seems to reduce ditellurides preferentially to the carboxyl group, a catalytic procedure can also be employed in which NaBH4 is added to the halo compound in the presence of a catalytic amount (0.1 equiv) of the ditelluride (which is continuously regenerated). 

The most convenient and commonly employed method for promoting the generation of TEMPO-oxoammonium is instead the so-called Anelh procedure It resorts to NaClO as the regenerating oxidant in 1 1 molar ratio with the substrate, under co-catalysis by EUlr. In a two-phase CH2Cl2-water system at 0°C, the oxidation of a primary alkanol does take place, to give the aldehyde selectively and in good yields (entry 3) after a few minutes. In contrast, if the reaction is run in aqueous solution with 2 molar equivalents of... 

The adsorption of NO, under lean conditions was studied by imposing a step change of NO and NO2 feed concentrations in the presence and absence of excess oxygen over the reference catalysts in a fixed-bed flow microreactor operated at 350 ° C and analyzing the transient response in the outlet concentrations of reactants and products [transient response method (TRM)[. The adsorption/desorption sequence was repeated several times in order to condition the catalytic systems fully due to the regeneration procedure adopted (either reduction with 2000 ppm H2 + He or TPD in flowing He), BaO was the most Ba-abundant species present on the catalyst surface. FT-IR spectroscopy was used as a complementary technique to investigate the nature of the stored NO species. 

This procedure has been used to prepare a variety of substituted a-bromohydrocinnamic acids 2 p-acetyl-a-bromohydro-cinnamic acid was prepared for the first time by this method. The method illustrates a typical application of the Meerwein reaction for the arylation of unsaturated substrates.3 In this reaction a catalytic amount of a copper(I) salt is used to reduce an aryl diazonium salt forming an aryl radical and a copper(II) halide. Addition of the aryl radical to an unsaturated substrate forms an alkyl radical that is reoxidized by the copper(II) halide present forming an alkyl halide and regenerating the copper(I) salt catalyst. In this preparation, the product, an a-bromo acid, is formed in an acidic reaction mixture and dehydro-halogenation does not occur. However, dehydrohalogenation... 

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