Catalysts ternary

Lima A, Coutanceau C, Leger JM, Lamy C. 2001. Investigation of ternary catalysts for methanol electrooxidation. J Appl Electrochem 31 379-386. 

The Cp2VCl2/R3SiCl/Zn catalytic system can be used for the reductive coupling of the imines 29 (Scheme 18) [55]. These components of the ternary catalyst are essential and, interestingly, meso-diastereoselectivity is observed in contrast to the coupling with cat. Cp2TiCl2/Sm system. The selectivity de-... 

Ternary catalysts with different amounts of Ba were also prepared, in the range 0-30% (w/w) for this purpose, the Pt/y-Al203 (1/100 w/w) sample was impregnated with solutions containing various concentrations of Ba(CH3COO)2. 

The reference Pt-Ba/y-Al203 (1/20/100 w/w) catalyst shows surface area values in the range 140-160 m2/g, a pore volume of 0.7-0.8cc/g and an average pore radius close to 100 A (measured by N2 adsorption-desorption at 77 K by using a Micromeritics TriStar 3000 instrument). Slight differences in the characterization data are associated to various batches of the ternary catalyst [24,25],... 

Still, the CO tolerance is too low for practical purposes. Ideally, 1000 ppm CO or more should be tolerated without a voltage loss exceeding 20 mV. Moreover, the stability of binary and ternary catalysts under fuel cell operating conditions is an issue. 

The ternary system of Pt-Ru-Sn seems promising to enhance the overall catalytic activities over the binary systems of Pt-Ru and Pt-Sn. Studying how to make small particles of this ternary catalyst is of great importance. 

The high activity of V-W-Ti-0 and of V-Mo-Ti-O is due to a synergistic effect between V and W (Mo) oxide species and is related to the superior redox properties of the ternary catalysts. 

A molybdenum oxychloride-based catalyst system, MoOCl4- -Bu4Sn-EtOH, is more active than Mods ones. " In the polymerization of 1-chloro-l-octyne by the oxychloride-based catalyst, propagation rate is improved to be faster and MWD of the formed polymer is smaller. This ternary catalyst also induces living polymerization of... 

The low-pressure methanol synthesis process utilizes ternary catalysts based on copper, zinc oxide, and another oxide, such as alumina or chromia, prepared by coprecipitation. Cu-Zn0-Al203 and Cu-Zn0-Cr203 are usually the most important industrial catalysts. A significant advance was made when a two-stage precipitation was suggested in which ZnAl2C>4, a crystalline zinc aluminate spinel, was prepared prior to the main precipitation of copper-zinc species.372 This alteration resulted in an increase in catalyst stability for long-term performance with respect to deactivation. Catalyst lifetimes industrially are typically about 2 years. 

Last, but not least, the development of ternary catalyst systems consisting of a metallocene, an organoborate, and an aluminium compound will reduce the manufacturing costs of mPE and will improve its ability to compete with other polymers. 

Imai, Saegusa, Furukawa et al. (48,66) carried out kinetic studies of THF polymerization in bulk and in cyclohexane solution at 0° C. They used a ternary catalyst system consisting of AlEt3-H20(2 l)-epichloro-hydrin (ECH). They obtained high molecular weight polymer and noticed no evidence for either termination or transfer. Their polymerizations were preceded by an induction period as shown in Fig. 13 but after that their data could be fitted to an equation of the same form as equation 42. This time [f0] was defined as the concentration of propagating species ([P ]) determined from the amount and the molecular weight of product polymer. 

Fig. 11.17 Chronoamperometric screening results from the ternary catalyst library described in Figs. 11.15 and 11.16. Surface-area-normalized activity values of each individual composition are plotted as a function of composition. Color-coding indicates activity red = high, blue = low. The pt-Ru binary compositions are connected by a solid line to underscore the activity trends observed in this binary system. Conditions 1 M methanol, 0.5 M H2S04, 550 mV/RHE, 5 min.

Figure 3.9 Layer composition of two ternary catalyst mixtures examined with SNMS before tempering (left) and after tempering at 850 °C for four hours (right) [37] (by courtesy of Elsevier Ltd.).

Up to 48 ternary catalyst mixtures were prepared simultaneously in less than 1 h. Hence the sputtering procedure is much faster than the wet chemical route and in fact one of the fastest syntheses available. This advantage is gained at the expense of low layer porosity. Thus, sputtered catalysts are new artificial catalysts and not directly comparable to catalysts prepared by wet-chemical procedures. These catalysts offer the advantage of quick preparation and characterization compared with alumina-based catalysts. They can also be used for obtaining so-called intrinsic kinetics because there is no influence of diffusion. 

For the partial hydrogenation of 1,3-butadiene, anodically oxidized aluminum catalyst carriers were impregnated with Pd, Co, and Cu. The concentrations of the catalytically active component were varied to form a ternary catalyst library with at least 132 different catalysts (Figure 3.21) [51]. 

Figure 3.21 Ternary catalyst library prepared by wet impregnation of oxidized aluminum carriers with Pd, Co and Cu salts [51]...

The results for the selected reaction conditions are shown in Figure 3.22. The ternary diagrams show the sum of n-butene yield, the reaction products of the hydrogenation of 1,3-butadiene, at the corresponding catalyst composition. It can be shown that the binary Cu and Co catalyst composition is inactive. An increase in Pd increases the yield of n-butene. However, binary catalyst compositions with Pd/Cu or Pd/Co show higher performance than single Pd. Furthermore, it is demonstrated that high catalytic activity can be observed also at isolated catalyst compositons within the field of ternary catalysts [51]. 

The high activity of Nd-based catalysts was reported by Shen et al. in 1980 [92], In this publication, the polymerization activity of the whole lanthanide series was studied. Ln halogen-based binary catalyst systems (LnCb/EtOH/AlEts or LnCl3 (TBPU/Al Bua), as well as Ln-carboxylate-based ternary catalyst systems (Ln(naphthenate)3/AlIBu3/EASC) were used. The activity profile for the entire series of lanthanides is depicted in Fig. 2. Two years later, Monakov et al. confirmed in a similar study that Nd is the most active Ln element [93,94]. 

Standard Nd-based catalysts comprise binary and ternary systems. Binary systems consist of Nd chloride and an aluminum alkyl or a magnesium alkyl compound. In ternary catalyst systems a halide free Nd-precursor such as a Nd-carboxylate is combined with an Al- or Mg-alkyl plus a halide donor. By the addition of halide donors to halide-free catalyst systems catalyst activities and cis- 1,4-contents are significantly increased. In quaternary catalyst systems a solubilizing agent for either the Nd-salt or for the halide donor is used in addition to the components used in ternary systems. There are even more complex catalyst systems which are described in the patent literature. These systems comprise up to eight different catalyst components. 

In addition to the polymerization of dienes the versatility of NdP-based catalysts is exceptional regarding the number of different non-diene monomers which can be polymerized with these catalysts. Acetylene is polymerized by the binary catalyst system NdP/AlEt3 [253,254]. Lactides are polymerized by the ternary system NdP/AlEt3/H20 [255,256]. NdP/TIBA systems are applied in the copolymerization of carbon dioxide and epichlorhy-drine [257] as well as for the block copolymerization of IP and epichloro-hydrin [258]. The ternary catalyst system NdP/MgBu2/TMEDA allows for the homopolymerization of polar monomers such as acrylonitrile [259] and methylmethacrylate [260]. The quaternary system NdP/MgBu2/AlEt3/HMPTA is used for the polymerization of styrene [261]. 

In addition to these two studies the polymerization kinetics of three different Nd-compounds which were activated by DIBAH and EASC were comparatively studied. In this investigation a Nd alcoholate [NdA = neodymium(III) neopentanolate], a Nd phosphate [NdP = neodymium(III) 2-ethyl-hexyl-phosphate] and a Nd carboxylate (NdV) were compared with a special focus on the variation of the molar ratios of zzdibah/hncI and ci/ Nd [272]. For each of these ternary catalyst systems the polymerization activities depend... 

In the polymerization of dienes with Ziegler/Natta catalyst systems it is a well-established fact that the presence of halide donors is essential in order to achieve high catalytic activities and high cis-1,4-contents [360,361]. The halide free catalyst system NdO/TIBA is a good example for a catalyst with a poor performance and a high trans- 1,4-specificity [362,363]. For various binary and ternary catalyst systems the qualitative impact of chlorides on the stereochemistry of BR is demonstrated in a series of fundamental experiments the results of which are summarized in (Table 5) [364],... 

For ternary catalyst systems a vast number of halide donors was investigated which renders a complete quotation impossible. It is important to note, however, that for a given halide, the actual halide source neither has a strong influence on catalyst activity nor on cis- 1,4-contents. As halogen sources which are found in the literature cover the whole range from ionic halides to covalently bound halogen atoms the strength by which the halide is bound to the donor is not a critical factor. 

Variations of the amount of cocatalyst which are usually expressed by the molar ratio W Nd have a significant influence on polymerization rates, molar masses, MMDs and on the microstructures of the resulting polymers. These aspects are addressed in the following sections with a special emphasis on ternary catalyst systems. For ternary systems it has to be emphasized, however, that in many reports the ratio Ai/ Nd only accounts for the amount of aluminum alkyl cocatalyst and not for other Al-sources such as alkyl aluminum halides. Variations of the Ai/ Nd-ratios are also used for defined control of molar mass. This aspect is addressed in separate sections (Sects. 2.2.8 and 4.5). 

In the context of ternary catalyst systems Throckmorton s pioneering work is worth mentioning although in this study Ce rather than Nd-based catalyst systems were used. For the two catalyst systems Ce octanoate/TIBA/DEAC and Ce octanoate/TIBA/EADC catalyst activities increased up to TiBA/ Ce = 20. Further increases in the TiBA/ Ce-ratios from 20-60 did not result in further activity improvements [34]. For a ternary didymium (Di)-based oc-tanoate catalyst system Witte described a similar dependence. Within the wAl/ Di-range 20-40 significant increases of polymerization rates were reported. Further increases of the nAi//iDi-ratios did not have an additional effect [49]. 

With a few exceptions, for binary as well as for ternary catalyst systems cis-1,4-contents decrease with increasing Ai/ Nd-ratios. This decrease of as-1,4-contents can be best explained on the basis of a model given in Scheme 30 in Sect. 4.3. According to this model aluminum alkyls act as ligands competing for vacant Nd sites. 

For ternary catalyst systems the decrease in cis- 1,4-contents with increasing Ai/ Nd-ratios is a common feature. The first report in which the decrease of ds-1,4-contents with increasing cocatalyst concentrations is addressed dates back to Throckmorton s study in which Ce-based catalyst systems were used [34]. The same dependence was confirmed in a subsequent study in which didymium octanoate-based catalysts were used [49]. In this study BD was polymerized and a decrease of the cis- 1,4-content from 95% at Al/ Di = 20 to 90% at Ai/ r)i = 60 is reported. 

Halide donors constitute an essential component of ternary catalyst systems (Sect. 2.1.3). In these systems variations of the molar ratios x/ Nd (X = halide) affect catalyst activities, molar masses, MMDs and the microstructures of the poly(diene)s. 

In ternary catalyst systems halides play an important role in the activation process of the Nd-precursor (Sect. 4.2). At low x/ Nd-ratios the contribution of the halide is small. Increasing Mx/ Nd-ralios, on one hand result in catalyst... 

For Nd-based ternary catalyst systems the dependence of polymerization rates on nx/ Nd ratios was in the focus of numerous studies. The results of these studies are summarized in Table 8. 

The literature referring to catalyst preformation of binary catalyst systems is not addressed in this work. In this review the available studies on ternary catalyst systems are summarized. The available literature is discussed in the following two subsections Preformation without Monomer and Preformation in the Presence of Diene Monomers . 

---