H2 reduction method

H2 reduction method. The elimination of chlorines in catalyst is an important role and step during the preparation of ruthenium catalyst. In order to eliminate the Cl in activated carbon supported ruthenium catalyst prepared using RuClg as the precursors, it is necessary that RuCla is reduced to elementary ruthenium and... 

The efficiency of H2 reduction method depends on the removal of the retained chlorines because HCl produced during the reduction process of the catalyst can be adsorbed once again so that the chlorines cannot be completely removed, even though the reduction reaction is complete. 

The introduction of tritium into molecules is most commonly achieved by reductive methods, including catalytic reduction by tritium gas, PH2], of olefins, catalytic reductive replacement of halogen (Cl, Br, or I) by H2, and metal pH] hydride reduction of carbonyl compounds, eg, ketones (qv) and some esters, to tritium-labeled alcohols (5). The use of tritium-labeled building blocks, eg, pH] methyl iodide and pH]-acetic anhydride, is an alternative route to the preparation of high specific activity, tritium-labeled compounds. The use of these techniques for the synthesis of radiolabeled receptor ligands, ie, dmgs and dmg analogues, has been described ia detail ia the Hterature (6,7). 

It is known that Au nanoparticles efficiently catalyze various reactions, but its activity greatly depends on the degree of dispersion, support, and preparation method. We tried to synthesize Au wires and particles by our photo- and H2-reduction. For the S5mthesis of Au nanowires, several groups use HAUCI4 as a precursor. 

The anchoring and the reduction methods of precious metal precursors influence the particle size, the dispersion and the chemical composition of the catalyst. The results of SEM and H2 chemisorption measurements are summarised in Table 3. The XPS measurements indicate that the catalysts have only metallic Pd phase on their surface. The reduction of catalyst precursor with sodium formate resulted in a catalyst with lower dispersion than the one prepared by hydrogen reduction. The mesoporous carbon supported catalysts were prepared without anchoring agent, this explains why they have much lower dispersion than the commercial catalyst which was prepared in the presence of a spacing and anchoring agent (15). 

Similar to the Fisher indole synthesis, reductive cyclization of nitro aromatics offers a powerful means of forming indoles. Reductive cyclization of ortho, 2 -dinitrostyrenes has occurred in many ways, by TiCl3, NaBH4-Pd/C, H2-Pcl/C, and other reductive methods.89 Corey and coworkers have used the Borchardt modification (Fe-AcOFI, sihca gel, toluene at reflux for the reductive cyclization of o-ji-dinitrostyrenes) to prepare 6,7-dimethoxyindole (Eq. 10.65) in a total synthesis of aspidophytine (see Schemes 3.3 and 3.4 in Section 3.2.l).89d... 

Hydrogen uptake of reduced catalysts (X) was measured by volumetric method with an AUTOSORB-l-C analyzer (Quantachrome Instruments). Hydrogen adsorption was carried out at 373 K after in situ H2 reduction at 773 K for 6 h in the adsorption cell. The dispersion and particle size of metallic Co were calculated by the following equations, assuming that the stoichiometry for hydrogen adsorption on the metallic site is unity ... 

Use of copper and silver salts in ethylenediamine solution provides a method for catalytic H2 reduction of nitroalkanes to oximes (541) ... 

High Diffusivity Low Viscosity Figure 15.21 Proposed mechanism of PtRh nanoparticles highly dispersed in HMM-1, which is prepared by H2 reduction of the PtRh salt-impregnated in FSM-16 or HMM-1 after the SCCO2 treatment, while the larger Rh and Pt particles are formed on the external surface of mesoporous supports by the conventional method. 

Another approach for H2 photocatalytic production is reported by Mizukoshi et al. [9] that described the syntheses of noble metal nanoparticles Ti02 composite photocatalysts by the sonochemical reduction method for hydrogen evolution from ethanol aqueous solutions at room temperature. 

The third method developed for preparing DENs is known as the sequential reduction method. This method, shown in Scheme 3 involves the initial complexation and reduction of a seed metal (Ma), followed by the com-plexation and subsequent reduction of the second metal (Mb) to produce the MaMb system. The synthetic utility of this method is that it provides the means to access both well mixed and core/shell-type DENs. When the reducing agent used for Mb is a mild reductant, such as H2 or ascorbic acid, core/shell nanoparticles with an Ma core and Mb shell can be selectively pre-... 

The final step in the preparation of a catalyst is the transformation of the precursor to the active phase (e.g. metal, sulfide) which is sometimes called activation. The activation may be a reduction (e.g. by H2), reduction-sulfidation (e.g. by H2 + H2S), dehydroxyla-tion (e.g. by removal of H20 from zeolite) or oxidation (e.g. by O2). The details of the activation process must be stated (e.g. partial pressure and purity of gas, method of heating and its rate, gas reacting flow rale, sample size). 

One of the standard methods for the preparation of aldehydes involves the reduction of acid halides. A variety of stoichiometric reducing systems are available for this transfomiation, which include NaAlH(OBu-r)3, LiAlHfOBu-O.i, NaBHfOMe). Catalytic hydrogenation with H2 and Pd on carbon is also a popular method. In contrast, methods based on the radical reduction of acyl halides are synthetically less important. Radical reduction methods involve generation and subsequent hydrogen abstraction as key steps, which is complicated by decarbonylation of the intermediate acyl radicals. The first example in Scheme 4-1 shows that this competitive reaction is temperature dependent, where an acyl radical is generated from an acyl phenyl selenide via the abstraction of a phenylseleno group by tributyltin radical [5]. 

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