Chlorine-free precursor

Danishefsky s total synthesis of 317 and its chlorine free precursor monocillin I 316 features an RCM reaction with a substrate 310 that in addition to a dithiane protective group contains a vinyl epoxide and a diene moiety at... 

C of solids prepared using chlorine-free precursors would be Ru>Rh>Pt> Pd. 

Another relevant issue in methane combustion over palladium is the significant increase in activity that is observed with lime on stream [46,49]. This may be explained by the removal of chloride ions from palladium precursor [46] but was also observed for chlorine-free precursors [49]. A change in the morphology of the palladium oxide on the surface during operation may be the cause for the activity enhancement. 

C1F = catalyst prepared with a chlorine-free precursor. 

FYom the data of Table 2, the relative activities in 02/ 02 equilibration at 300°C (chlorine-free precursors) would be... 

It is known that chlorine acts as severe poison for NH3 synthesis [20,21]. Hence recent kinetic studies used chlorine-free Ru precursors like Ru3(CO)i2 [8,22] or Ru(N0)(N03)3 [7]. In addition to chlorine, the presence of sulphur was found to poison Ru catalysts. Fig. 2A demonstrates that both poisons may originate from the Ru precursor. The binding energies for the Cl 2p peak and of the S 2p peak observed for Ru prepared form RUO3 are typical for chloride and sulfide anions, respectively [23]. Ru prepared from Rus(CO)i2 was found to have a significantly higher purity. As shown in fig. 2B, sulphur and chlorine impurities can also originate from the support. The XPS data of MgO with a purity of 98 % reveal the presence... 

Regarding the preparation of praseodymia and teibia supported metal catalysts, the information available is rather scarce. All the reported studies have dealt with dispersed noble metal samples. Though metal vapor deposition has been applied in some cases (231), the impregnation techniques have coirstituted the most usual preparation procedure. Chlorine-containing (53,82,85,127,175,278), and chlorine-free (53,84,232,278) metal precursors have been used. As already reported, PrOCl and Tb(3CI have been identified in praseodymia and terbia supported catalysts prepared from chlorinated precursors (82). Water (82,85,127,175), and non-aqueous solvents. 

In a recent review work (117) on the chemical and nano-structural characterization of NM/CeO catalysts, a detailed study of the H interaction with a Pt/CeO catalyst reduced at temperatures ranging fh)m 473 K to 773 K is reported. The experimental techniques used in this work were TPD-MS and Isotopic Transient Kinetics (ITK) of the H2/D2 exchange at 298 K. The catalyst sample was carefully selected in order to minimise the Pt and support sintering effects in the investigated range of reduction temperatures. Likewise, a chlorine-free metal precursor, [Pt(NH3)4](OH)2, was used in the preparation of the catalyst. 

A rather similar observation on a Rh/Ce02 catalyst, also prepared from a chlorine free metal precursor, has been interpreted as due to the activation of the spillover... 

Metal loading (wt%). (Cl) and (N) stand respectively for catalysts prepared from chlorine-containing and chlorine-free metal precursors. 

The controversy has not hurt business for the chlorine industry, which is booming.238 There have been some shifts in the product line. Methylene chloride demand is dropping. More trichloroethylene is being produced as a feedstock for fluorocarbon production. More sodium chlorite is being produced as a precursor for chlorine dioxide to be used in the bleaching paper. The trend should start downward in the future as chlorine-free alternatives are found and as ageing plants are retired. 

Reaction (11), the disproportionation of the C102 ion to CIO2 and Cl , affords chlorine-free chlorine dioxide. Reaction (12) is less useful when CIO2 is being used to combat taste and odor, since the product is inevitably contaminated with hypochlorous acid, thus defeating the objective of using a chlorine substitute. The precursor in either case is sodium chlorite, NaC102, which is a powerful oxidizer, and has to be stored carefully. 

Chlorine free platinum precursors TG analysis of [Pt (NH3)4](N03)2 in air showed a small increase in weight (5%) in the range 100-215°C. This is probably due to oxidation of the sample, but it is not possible to clarify this from the TGA results. SDTA analysis indicated exothermic character of the decomposition reactions in both oxidizing and reducing environments. In the... 

We must keep in mind, that lor the automotive exhaust reactions, which are oxydo-reduction type, the catalyst has to be chlorine free. Thus, we never use precursor salts containing chlorine. 

The above mentioned four kinds of ruthenium compounds can be divided into two groups One is chlorine-containing and another is chlorine-free. Both of them can be used as the precursor of ruthenium in catalysts. 

Ru3 (CO) 12 is widely studied as precursor of chlorine-free ruthenium compoimd. A lot of studies have been conducted on Rus (CO) 12 due to its high activity caused by low valence states of Ru in Rus (CO) 12, high diserpsion on support and absence of chlorine which can poison the ruthenium catalyst. 

The lack of oxygen in the reducing environment of the gasifier prevents formation of free chlorine from HC1 and limits chlorination of any precursor compounds in the gasifier... 

The metabolism of carbon tetrachloride proceeds via cytochrome P-450-dependent dehalogenation (Sipes et al. 1977). The first step involves cleavage of one carbon-chlorine bond to yield Cl- and a trichloromethyl free radical, which is then oxidized to the unstable intermediate trichloromethanol, the precursor of phosgene. Hydrolytic dechlorination of phosgene yields C02 and HC1 (Shah et al. 1979). Although there are similarities in the metabolism of chloroform and carbon tetrachloride, metabolic activation of chloroform produces primarily phosgene, whereas the level of phosgene production from... 

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