Leaching of catalysts

Catalyst leaching - The mixture may segregate leading to possible leaching of snlfate gronps. The leaching of catalyst was stndied in organic and in aqneons phases. 

The leaching of catalyst components into the aqueous phase during the reaction represents a possible disadvantage of the process. Therefore, the choice of catalyst support materials has to be limited to those that exhibit long-term hydrothermal stability (e.g. carbon, titania, zirconia). 

An example of this approach to TSIL formulation is the synthesis from 1-vinylim-idazole of a series of imidazoHum cations with appended tertiary phosphine groups [Scheme 2.3-3]. The resulting phosphines are then coordinated to a Rh(I) organometallic and dissolved in the conventional IL [BMIM][PF6], the mixture constituting a TSIL. The resulting system is active for the hydroformylation of 1-octene, with no observable leaching of catalyst [17]. 

Fluorous biphase reactions have been reviewed extensively in the past few years, and most important types of reaction may now be conducted under fluorous conditions [46,51], However, partitioning of catalysts and reagents into the fluorous phase is seldom perfect - even a loss of 1-2% of an expensive catalyst may be unacceptable. Solubility and partitioning between phases relies on a complex balance of properties and interactions, and rather than simply adding more fluorocarbon chains to a catalyst (which is a common approach to the problem of leaching of catalyst from the fluorous phase), studies have indicated that the partition coefficients of fluorous compounds may better be optimised by... 

PtBi/C catalysts were reported earlier to enable selective oxidation of the secondary hydroxy function of glyceric and tartronic acid to hydroxypyruvic and mesoxalic acid, respectively [13]. In the work reported here, these two reactions were studied in more detail to determine Ae influence of the following parameters on selectivity and reaction progress pH of the reaction medium, over-oxidation of targeted products, and leaching of catalyst components. 

Catalyst immobilization can leaching of catalyst into the product stream be... 

A drawback to the use of commercial catalysts in ILs concerns the leaching of catalyst or catalyst residues into the organic solvents used for product isolation. This leads to high levels of product contamination, along with the rapid decrease of... 

To increase the hpophihc character, cosolvents can be added to the classical RCH/RP system. Solvents like methanol, ethanol, polyethylene glycol strongly increase the hydroformylation rate [8]. The potential disadvantages of these cosolvents are leaching into the organic phase and their reactivity towards acetals. Leaching of catalyst and hgand seems to be no problem, provided that certain concentrations of cosolvents are not... 

MgAl and MgCa oxides were found to be efficient catalyst for transesterification of ethyl butyrate and methanol and for methanolysis of sunflower oil. With 1 12 of oil and methanol and 2.5% of catalyst at a temperature of 60° C, 92% of yield of FAME was obtained. The best ratio of Mg Ca was foimd to be 3.8 and there was no leaching of catalyst into the reaction medium [37]. 

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