Lanthanum-based catalysts

Perovskites, 27 358 band structure, 38 131-132 crystal structure, 38 123-125 Perovskite-type oxides see also specific lanthanum-based catalysts actinide storage in radioactive waste, 36 315-316... 

Figure 17 shows a comparison of the fresh SO2 removal ability for these five major types of commercially available SOx catalysts. The materials were tested at 1350 F at various concentrations with a very low capacity cracking catalyst. The magnesia-based catalyst is much better than lanthanum-based catalyst followed by platinum or cerium on alumina and finally alumina alone. The reverse order in activity observed for the lanthanum-based and cerium additives, compared to the relative results given previously for lanthanum and cerium, was not investigated, but may be related to the presence of cerium on the lanthanum-based additive (27). 

In alkyl aluminum chlorides of the type RxAlyClz two different chemical moieties which cause alkylation as well as chlorination are present in one molecule. Therefore, RAAL,Clz-type activators do not require the separate addition of other halide donors in order to achieve high cis-1,4-contents. In Nd-based catalyst-systems the dual role of RXA1 C1Z compounds is demonstrated by Watanabe and Masuda [364], These findings only hold true for Nd-based catalyst systems. For lanthanum-based catalyst systems Lee et al. found that the use of alkyl aluminum chlorides results in trans- 1,4-polymerization (93-94%) [371]. However, usually, in Nd catalysts the alkylating power of RxAlyClz is not sufficient at the applied amounts of RXA1 C1Z. Thus, an additional standard cocatalyst has to be added for the activation of the Nd precursor. 

Vella, L.D., Villoria, J.A., Specchia, S., Mota, N., Fierro, J.L.G., and Specchia, V. (2011) Catalytic partial oxidation of CH4 with nickel-lanthanum-based catalysts. Catal Today, 171 (1), 84-96. 

Podldlzin, S. G., Strangland, E. E., Jones, M. E. (2007). Methyl chloride production from methane over lanthanum based catalysts. Journal of the American Chemical Society, 129, 2569-2576. 

SCHEME 4.138 Preparation of a-hydroxyphosphonates using a lanthanum-based catalyst [231]. 

J. Sfeir, P A. Buffat, P. Mockli, N. Xanthopoulos, R. Vasquez, H. J. Mathieu, J. Van herle, and K. Ravindranathan Thampi, Lanthanum chromite based catalysts for oxidation of methane directly on SOFC anode, J. Catal. 202, 229-244 (2001). 

Two of the materials were furnished by catalyst companies and are referred to as magnesia-based or magnesia and lanthanum-based or lanthanum. These latter materials are both known to contain cerium and alumina as well. 

Commercial catalysts vary in the degree to which they are regenerable at reactor temperatures as shown on Figure 18. The initial SO2 removal for all five materials was adjusted to an equal basis by varying the amount of additive used 0.8% magnesia-based, 3% lanthanum-based, 10% of both cerium/alumina and... 

The same authors (77) also investigated the Michael addition of nitromethane to a,/l-unsaturated carbonyl compounds such as methyl crotonate, 3-buten-2-one, 2-cyclohexen-l-one, and crotonaldehyde in the presence of various solid base catalysts (alumina-supported potassium fluoride and hydroxide, alkaline earth metal oxides, and lanthanum oxide). The reactions were carried out at 273 or 323 K the results show that SrO, BaO, and La203 exhibited practically no activity for any Michael additions, whereas MgO and CaO exhibited no activity for the reaction of methyl crotonate and 3-buten-2-one, but low activities for 2-cyclohexen-l-one and crotonaldehyde. The most active catalysts were KF/alumina and KOH/alumina for all of the Michael additions tested. 

Zhang, G., Hattori, H. and Tanabe, K. Aldol addition of acetone, catalyzed by solid base catalysts magnesium oxide, calcium oxide, strontium oxide, barium oxide, lanthanum-(III) oxide and zirconium oxide, Appl. Catal., 1988, 36, 189-97. 

More recently, a very efficient yttrium-based catalyst, yttrium 2-methoxyeth-oxide, has been applied successfully for /f-butyrolactone polymerisation which proceeded easily at room temperature [99], It is worth mentioning that rare-earth metal alkoxides (derived from yttrium and lanthanum) exhibit outstanding efficiency as catalysts for the polymerisation of cyclic esters such as e-caprolactone [132] and lactide [133]. 

From the early 1960s onwards, the use of lanthanide (Ln) based catalysts for the polymerization of conjugated dienes came to be the focus of fundamental studies [31]. The first patent on the use of lanthanides for diene polymerization originates from 1964 and was submitted by Union Carbide Corporation (UCC) [32,33]. In this patent the use of binary lanthanum and cerium catalysts is claimed. Soon after this discovery by UCC, Throckmorton (Goodyear) revealed the superiority of ternary lanthanide catalyst systems over binary catalyst systems. The ternary systems introduced by Throckmorton comprise a lanthanide compound, an aluminum alkyl cocatalyst and a halide donor [34], Out of the whole series of lanthanides Throckmorton... 

Neodymium-based catalysts are favored over other Ln metals because they are highly active and the catalyst precursors are readily available for reasonable prices. In addition, Nd catalyst residues do not catalyze aging of the rubber. The use of didymium catalyst systems is also reported in the literature. Didymium consists of a mixture of the three lanthanides neodymium (72 wt. %), lanthanum (20 wt. %) and praseodymium (8 wt. %). 

Some of the metal-based catalysts used in the asymmetric hydrophosphonylation of aldehydes (see Section 6.4) can also be applied to the phosphonylation of imines. For instance, Shibasaki s heterobimetallic BINOL complexes work well for the catalytic asymmetric hydrophosphonylation of imines. In this case lanthanum-potassium-BINOL complexes (6.138) have been found to provide the highest enantioselectivities for the hydrophosphonylation of acyclic imines (6.139). The hydrophosphonylation of cyclic imines using heterobimetallic lanthanoid complexes has been reported. Ytterbium and samarium complexes in combination with cyclic phosphites have shown the best results in the cases investigated so far. For example, 3-thiazoline (6.140) is converted into the phosphonate (6.141) with 99% ee using ytterbium complex (6.142) and dimethyl phosphite (6.108). The aluminium(salalen) complex (6.110) developed by Katsuki and coworkers also functions as an effective catalyst for the hydrophosphonylation of both aromatic and aliphatic aldimines providing the resulting a-aminophosphonate with 81-91% ee. ... 

Sfeir J, Buffat PA, Mockli P, Xanthopoulos N, Vasquez R, Mathieu HJ, Van herle J, Thampi KR (2001) Lanthanum chromite based catalysts for oxidation of methane directly on SOFC anodes. J Catal 202 229-244... 

Barbero, B.P., and Cadus, L.E. (2013) Lanthanum-based perovskites as catalysts for the ozonation of selected organic compounds. Appl Catal B Environ.,... 

The behaviour of a Pt-based catalyst on a metallic monolith support washcoated with alumina, with the addition of lanthanum and cerium, was studied by Musialik-Piotrowska and Mendyka. The activity of the catalyst was tested in the oxidation of ChB and DCE alone and in two-component mixtures with toluene, -hexane, acetone, ethanol, and ethyl acetate. The influence of non-chlorinated compounds on ChB oxidation differed from one compound to another. Over the whole range of reaction temperatures, ethanol enhanced the conversion of ChB by 10%. The addition of both hydrocarbons also slightly improved ChB destruction, while DCE conversion was inhibited in the presence of each non-chlorinated compound that was added. Both chlorinated hydrocarbons not only inhibited catalytic destruction of each of the non-chlorinated compounds added, but also increased the reaction selechvity and concentration of the intermediate yielded, the first of which was acetaldehyde. 

Zhang et al. [194] proposed the following mechanistic steps, involving a Ni/La203 catalyst, which has been found to be appUcable to various other lanthanum-based supports [157, 195] ... 

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