Abstract:The
alkaline catalysts commonly applied to alkoxylation are characterized
by a limited spectrum of activity caused by an irreversible termination
of the polyether chains. The presented results show that double metal
cyanide (DMC) catalysts reduce or eliminate the aforementioned adverse
rearrangement of hydroxyl groups. Moreover, DMC catalysts indicate
high activity at low concentrations (ppm range), as expressed by high
polymerization rates. It was demonstrated that decreased concentrations
of DMC catalyst irr… Show more
“…Regardless of the appropriate selection of substrates, preparation of the DMC catalysts is highly complex, with many critical factors, which determine the obtained catalytic activity and the quality of the polyadducts. The precise characteristic of DMC is described in one of our previous papers [10]. Fig.…”
The synthesis and basic properties of 2-ethylhexanol based innovative nonionic surfactants are described in this paper. 2-Ethylhexanol as an available and relatively inexpensive raw material was used as the hydrophobe source modified by propoxylation and followed by polyethoxylation. As the result, six series of 2-ethylhexyl alcohol polyalkoxylates (EHPmEn) were obtained with three steps of propoxylation, each followed by polyethoxylation and two series only with polyethoxylation (EHEn). Two different catalysts were used, a dimetalcyanide and KOH. Values of average conversion rates and chemical content of the obtained products (GC, TG and GPC techniques) were compared. The influence of the applied catalyst and polyaddition degree on the homologue distribution, reactant conversion and amount of byproducts is discussed. The basic physicochemical parameters including refractive index, solubility in polar media, foaming properties and wettability were investigated and compared. Furthermore, surface activity parameters, i.e. surface tension (γCMC) and critical micelle concentrations were determined. Results are compared to C12–14 alcohol ethoxylates (LaEn). Accordingly, it was found that the studied 2-ethylhexyl alcohol based compounds are effective, low foaming nonionic surfactants.
“…Regardless of the appropriate selection of substrates, preparation of the DMC catalysts is highly complex, with many critical factors, which determine the obtained catalytic activity and the quality of the polyadducts. The precise characteristic of DMC is described in one of our previous papers [10]. Fig.…”
The synthesis and basic properties of 2-ethylhexanol based innovative nonionic surfactants are described in this paper. 2-Ethylhexanol as an available and relatively inexpensive raw material was used as the hydrophobe source modified by propoxylation and followed by polyethoxylation. As the result, six series of 2-ethylhexyl alcohol polyalkoxylates (EHPmEn) were obtained with three steps of propoxylation, each followed by polyethoxylation and two series only with polyethoxylation (EHEn). Two different catalysts were used, a dimetalcyanide and KOH. Values of average conversion rates and chemical content of the obtained products (GC, TG and GPC techniques) were compared. The influence of the applied catalyst and polyaddition degree on the homologue distribution, reactant conversion and amount of byproducts is discussed. The basic physicochemical parameters including refractive index, solubility in polar media, foaming properties and wettability were investigated and compared. Furthermore, surface activity parameters, i.e. surface tension (γCMC) and critical micelle concentrations were determined. Results are compared to C12–14 alcohol ethoxylates (LaEn). Accordingly, it was found that the studied 2-ethylhexyl alcohol based compounds are effective, low foaming nonionic surfactants.
“…DMC is a coordination-type dimethylcyanide catalyst [4] used in industrial practice for the synthesis of polyetherpolyalcohols as intermediates for polyurethane polyols. The use of coordination DMC-type catalysts in the polyoxyalkylenation of detergent alcohols has not been appreciated by industry but there are a few exceptions [12,13]. Table 1 shows analytical characteristics of the test series of nonionic surfactants.…”
Section: Characterization Of Test Materialsmentioning
confidence: 99%
“…The ordinates show foamability (upper graph) in millimeters of foam layer and emulsifiability (lower graph) in seconds of emulsion lifetime for five concentrations of a mixture of surfactants (Figs. 3,4,5,6,7,8,9,10,11,12,13,14). The abscissae show the surfactant concentrations in the form of mole fractions.…”
Section: Surface Properties Of the Surfactant Test Systemsmentioning
confidence: 99%
“…Moreover, we investigated the effect of the range of homologue distribution on the curve profiles illustrating the dependence of surface properties vs. concentrations of components in the test mixtures. An alternative surfactant series with a different range of homologue distribution was generated using classical catalysis with an alkaline catalyst (KOH) which yielded products having the so-called broad range of distribution combined with propoxylation and ethoxylation using zinc hexacyanocobaltate as the double metal cyanide (DMC) coordination catalyst, generating oxyalkylenation products having a relatively narrow fractional composition [12,13]. [12,14].…”
The surface properties of quasi-ternary systems comprising two surfactants in water were studied in the light of previously published hypotheses of specific two-dimensional arrangements of associated surfactant molecules and compatibility of their hydrophobic chains. In contrast to the studies of model ternary systems of pure components reported previously in the literature, the title quasi-ternary systems were prepared as water solutions of two polydisperse mixtures of surfactants: an anionic one (quasi-component 1) and nonionic one (quasi-component 2). The complex quasi-components used were polydisperse in terms of both ethylene oxide substituent numbers and the carbon chain length, obtained as received under industrial conditions from commercial raw materials. The novel surfactants which are the subject of the present study were synthesized by elongation of the hydrophobic chain of 2-ethylhexan-1-ol molecules by catalytic polyaddition of methyloxirane (propylene oxide), followed by introduction into the resulting transformed structure of a hydrophilic group (in the form of a polyether chain and/or a sulfosuccinate group). All synthesized surfactants were therefore polydispersed mixtures of methyloxirane and oxirane (ethylene oxide) homologues. It was shown that, in the case of the quasi-ternary aqueous systems studied, the extrema of the investigated functions describing the surface properties occur in the neighborhood of some specific stoichiometric ratios of the surfactant concentrations, namely 1:3/3:1. On the other hand, synergistic effects associated with the compatibility of the hydrophobic chains studied were not confirmed.
“…These catalysts are commonly applied at industrial ring-opening polymerization of the epoxides, being the initial stage of the polyurethanes manufacturing route. [1][2][3] The DMC catalysts have a considerably high activity, which is their key feature. A typical, state-of-the-art DMC catalyst frequently occurs to be a nonstoichiometric multiphase compound, the chemical composition of which is usually defined by general formula Me 1…”
Double metal cyanide (DMC) catalysts are commonly applied at industrial ring-opening polymerization of the epoxides, being the initial stage of the polyurethanes manufacturing route. This group of catalysts is frequently used in industry, but the knowledge on the molecular nature of their high activity and selectivity is limited to some phenomenological hypotheses based on overall chemical premises. To shine some light on the relation between structural and chemical properties of DMC catalysts and their activity, the complementary X-ray powder diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and X-ray absorption spectroscopy studies were performed. The comprehensive characterization of DMC catalyst synthesized from ZnCl 2 and potassium hexacyanocobaltate(III) solution, in presence of the organic ligand ( t BuOH), confirmed that a significant part of the catalyst material reveals the features of the non-crystalline structure. Extended X-ray absorption fine structure (EXAFS) analysis established that only Zn atoms are the active metallic centers in the DMC catalyst. The coordination around Zn was changed from octahedral in reference material to tetrahedral in catalysts, and Cl atoms were detected near some of the Zn atoms, but no significant amount of oxygen atoms was detected, which agrees with XPS chemical analysis. The performed experimental studies give direct experimental evidence for the model deduced by Zhang et al., and for the calculation performed by Wojdeł et al. Moreover, the generally accepted formula Zn 3 [Co(CN) 6 ] 2 • xZnCl 2 • ytBuOH • zH 2 O describing this catalyst is not valid, because none of the compounds were detected by XRD or EXAFS techniques.Regarding the relation between structural and chemical activity of catalyst, we conclude that for the chemical activity of DMC catalyst not only is the content of Cl very important, but also the fraction of non-crystalline phase, the formation of which is stimulated by ligand. The non-crystalline fraction of catalyst may offer the easier access to the active center with Cl.
Results and discussion
X-ray diffractionTrizinc bishexacyanocobaltate(III), used as a reference material, has been reported to be dimorphic, cubic (Fm-3 m) and rhombohedral Catalytic centre in double metal cyanide catalysts
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