Two-phase process

A two-phase process developed by CDTech in the 1980s (22,23) and Hcensed also by ABB Lummus Crest is claimed to be appHcable to dilute... 

The most limiting factor for enzymatic PAC production is the inactivation of PDC by the toxic substrate benzaldehyde. The rate of PDC deactivation follows a first order dependency on benzaldehyde concentration and reaction time [8]. Various strategies have been developed to minimize PDC exposure to benzaldehyde including fed-batch operation, immobilization of PDC for continuous operation and more recently an enzymatic aqueous/octanol two-phase process [5,9,10] in which benzaldehyde is continuously fed from the octanol to the enzyme in the aqueous phase. The present study aims at optimal feeding of benzaldehyde in an aqueous batch system. 

Hydrolysis of diphenyl phosphorochloridate (DPPC) in 2.0 M aqueous sodium carbonate is also believed to be a two-phase process. DPPC is quite insoluble in water and forms an insoluble second phase at the concentration employed (i.e. 0.10 M). It seems highly significant that the hydrophobic silicon-substituted pyridine 1-oxides (4,6,7) are much more effective catalysts than hydrophilic 8 and 9. In fact, 4 is clearly the most effective catalyst we have examined for this reaction (ti/2 < 10 min). Since derivatives of phosphoric acids are known to undergo substitution reactions via nucleophilic addition-elimination sequences 1201 (Equation 5), we believe that the initial step in hydrolysis of DPPC occurs in the organic phase. Moreover, the... 

A two phase process, in which the feedstock (e.g., petroleum) was mixed with water and an organic solvent to improve denitrogenation of aromatic nitrogen compounds [102], led to an improvement of the process. Additionally, a surfactant was used to increase the interfacial area. Carbazole and quinoline and their alkyl derivatives were used as primary compounds for demonstration. The biocatalyst is used in resting stage and is continuously fed to the system to keep the reaction rate at an acceptable level. It was observed that quinoline was hardly removed under the conditions at which carbazole was decomposed and assimilated. 

Aqueous biphasic catalysis is a special case of the two-phase processes of homogeneous catalysis. Despite the academic literature s provocative question "Why water " [18a, 18b], the advantages of water as the second phase and the "liquid support" are numerous. On the one hand, the search for the necessary solubility gap is much easier with water than with various organic-phase liquids (Figure 5.2). Additionally, water has many properties which predestine it as a ideal liquid support in homogeneous catalysis (see T able 5.1)[18c,18d]. 

Whereas this important quotient is calculated solely from the product spectrum, process simplifications are a consequence of combining the rhodium catalyst with the special two-phase process. Compared with the conventional oxo process and with other variants (which, for example, include disadvantegeously thermal separation of the oxo reaction products from the catalyst) the procedure is considerably simplified (as shown in several papers, e.g., [2,12]). 

In a review of feeding and digestion in the Bivalvia [37], it was proposed that the accumulation of metal-bound particulates in the digestive gland was a two-phase process reflecting extracellular and intracellular digestion, and Viarengo [87] has reached similar conclusions. In a pulse chase study of the uptake of radiolabelled metals (Ag, Cd, Cr, Hg, Se) by the zebra mussel Dreissena... 

By adding up to 36% ethylene glycol to the aqueous catalyst phase, the space-time yield could be boosted up to approx. 3 mt m-3 h-1 for propene hydroformylation, a factor of 20 in comparison to the conventional two-phase process without changing the reaction conditions. Because of this surprising speed-up, higher alpha-olefins up to 1-octene are converted with high to acceptable space-time yield (Fig. 22). Up to date this process is not commercialized, but has been tested in a continuous pilot plant. 

Fig. 22 Static mixer reactor for two-phase process Comparison with conventional stirred tank...

Two-phase process, tppts Ruhrchemie/Rhone-Poulenc... 

The tppts process has been commercialised by Ruhrchemie (now Celanese), after the initial work conducted by workers at Rhone-Poulenc, for the production of butanal from propene. Since 1995 Hoechst (now Celanese) also operates a hydroformylation plant for 1-butene. The partly isomerised, unconverted butenes are not recycled but sent to a reactor containing a cobalt catalyst. The two-phase process is not suited for higher alkenes because of the... 

The most straightforward and efficient method now available for N-alkylation of carbazoles is the catalytic two-phase process utilizing a benzene solution of the carbazole, 50% aqueous sodium hydroxide, and a catalytic quantity of a tetraalkylammonium salt (benzyltrimethylammo-nium chloride has been used) with the requisite halide. - The efficient and simple formation of 9-methyl, 9-ethyl, 9-n-propyl, 9-n-butyl, and 9-benzyl derivatives has been described. ... 

A breakthrough in the hydroformylation of propene was achieved following the synthesis of the water soluble ligand tppts for the preparation of the RhH(CO)(tppts)3 catalyst345 which formed the basis for the development of the Ruhrchemie/Rhone-Poulenc two phase process. This process operates under mild reaction conditions giving excellent n/i ratios and easy separation of products from the catalyst by decantation with virtually no catalyst leaching. 

The history of aqueous industrial two-phase catalysis began in 1984 when the hydroformylation of propene in water was first carried out in the plants of Ruhrchemie AG. The development of the aqueous two-phase process was completely atypical in that the initial research work was done by Rhone-Poulenc but the development work was done by the former Ruhrchemie (today part of Hoechst AG). A rather long time elapsed before further fundamental work was begun in academic laboratories. 

In the two-phase process dyes and chemicals are applied in separate steps first dyes and thickener ( solid phase ) are printed, then chemicals and auxiliaries are added as an aqueous solution by padding. Sodium dithionite (Hydrosulfite) is used as reducing agent, and steaming time is kept short (20-40 s). For stabilized reducing agents, see [5, p. 296-298],... 

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