Lanthanum hydroxide oxide

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. 

Lanthinum hydroxide on dehydration produces lanthanum oxide monohydrate, La203 H20 ... 

The salt is prepared by dissolution of lanthanum oxide, hydroxide or carbonate in nitric acid, followed by crystallization, and obtained as a hexahydrate. The general reactions are as follows ... 

Lanthanum oxide can be produced by direct combustion of lanthanum in oxygen or air. The oxide also may be prepared by decomposition of an oxo salt of lanthanum, such as nitrate, sulfate, carbonate, hydroxide or oxalate. 

Lanthanum sulfate is prepared by dissolving lanthanum oxide, hydroxide or carbonate in sulfuric acid, followed by crystallization. 

Lanthanum aluminate. Mechanochemical synthesis of lanthanum aluminate was carried out by the joint grinding of lanthanum oxide La203 with aluminium hydroxide or oxide in a planetary mill [20]. After activation for 120 min, a monophase product LaA103 with a large specific surface area was obtained. However, the formation of LaA103 was not observed when a-AI2O3 was used as an initial reagent. 

The hydroxides are precipitated by NaOH from Ln solutions and are insoluble in an excess. Apart from the exceptions already mentioned, they are converted into the sesquioxides, 1 303, by heating in air. Lanthanum oxide, a very strong base, slakes like CaO on the addition of water and wil then take up COg. The oxides of the other elements become progressively weaker bases as the size of the Ln + ion diminishes. The lanthanide oxides have particularly high heats of formation ... 

The liquid phase hydrogenation of benzene on carrier-fixed ruthenium colloid catalysts suspended in an aqueous solution of sodium hydroxide proceeds with 59% cyclohexene selectivity at 50% benzene conversion. The catalysts are prepared by adsorbing a hydrophilic stabilized ruthenium metal colloid on lanthanum oxide. Protection of metal colloids with chiral molecules can lead to a new type of enan-tioselective catalyst combining good selectivity control with extraordinarily high activity in hydrogenation reactions. This concept has been applied for the first time in the form of platinum sols stabilized by the alkaloid dihydrocinchonidinel °°l (Fig. 7). 

The thermal transformation fix)m lanthanum hydroxide (La(OH)3) to lanthanum oxide (La203) was studied by Neumann and Walter [188]. They reported two successive endothermic effects, caused by loss of water. Thermal analysis (DTA-TG, DSC), and high-temperature powder XRD were used to characterize this process. Lanthanum hydroxide oxide (LaOOH) was obtained as a temporary product at about 330 C. The structure of lanthanum hydroxide oxide was characterized by powder XRD and subsequent Rietveld refinement. The enthalpies of dehydration were calculated by DSC to be 87 kJ mof for the transformation La(OH)3 to LaOOH, and 54 kJ mof for the transformation LaOOH to La203. The activation energy of the transformation of lanthanum hydroxide to lanthanum hydroxide oxide was estimated by isothermal TG studies. 

Lithium hydroxide Lithium hydroxide monohydrate 215-185-5 AS-9600 DWS 1016 DWS 1017A pHreeGUARD 1215C pHreeGUARD 2350 Sodium hydroxide Unichem SOHYD 215-193-9 Indium oxide 215-197-0 Potassium sulfide 215-199-1 Potassium silicate Trasol KA-L Trasol KA-N Trasol KC-K Trasol KD-K 215-200-5 Lanthanum oxide 215-202-6 Manganese dioxide 215-204-7 Charmax MO Molybdenum trioxide Molyhibit POM POC Polu-U 215-208-9 Sodium oxide 215-211-5 Sodium polysulfide Sodium sulfide 215-213-6 Niobium oxide 215-215-7 Nickel oxide (ous)... 

Methacrylic acid produced from propionic acid in this process can be esterified with methanol to yield methyl methacrylate. Catalysts used in this route include alkali metal or alkaline-earth metal aluminosilicates, potassium hydroxide- or cesium hydroxide-treated pyrogenic silica, alumina, and lanthanum oxide. Both propionic acid and methyl propionate are commercially available through the Oxo process (i.e., by the carbonylation of ethylene or by the hydrofor-mylation of ethylene to propionaldehyde, followed by oxidation of the aldehyde to the corresponding acid). This alternative route has, however, shown only 50% conversion and >80% selectivity rates, and it appears that additional catalyst development is necessary in order to make this process more attractive. 

In the case of the formation of ATLS from lanthanum oxide, the structure of lanthanum hydroxide as an intermediate allows the formation of apatite through the topotactic mechanism. Thus, the coordination number (CN) of lanthanum in lanthanum oxide is 7, while there are 7- and 9-coordinated lanthanum cations in the apatite (Table 6). The lanthanum oxide hydration leads to increase of lanthanum CN from 7 to 9. This is also accompanied by the lattice expansion in the a and b dimensions and its contraction in the c dimension (Table 6). Subsequent acid-base interaction between the lanthanum hydroxide and silica or intermediate amorphous silicate results in the silicon incorporation into the structure to form apatite structure. This leads to the additional lattice expansion in three dimensions and the decrease of CN from 9 to 7 for 64% of lanthanum cations. 

Figure 2.1. Illustration of two kinds of sample preparation procedures. One is the mositure desorbed La203 film (Type-A) which was annealed at 400 °C in high vacuum (HV) chamber (10-6Pa) to make lanthanum hydroxide decompose into lanthanum oxide and H2O[10]. The other is the moisture absorbed sample (Type-B) which was exposed to the air (the temperature is 24 °C and the relative humidity is around 55%) with different time (zero,6 and 12 hours). Both samples were followed by 6nm Si02 layer deposition. Type A sample was processed without any exposure to the air to prevent the moisture absorption...

For strontium-doped lanthanum chromites, the precipitation of SrO is not possible, because strontium ions are more stable in the perovskite stmctuie than the lanthanum ions. Lanthanum oxide, La203, is often precipitated instead of SrO. This causes the disintegration of sintered specimens at ambient temperatures by the volume change associated with the formation of lanthanum hydroxide, La(OH)3, due to the reaction of La203 with the water vapor in the air (Meadowcroft, 1969 Sakai et al., 1990a). The substitution of transition metals such as zinc (Hayashi et al., 1988), cobalt (Zhou et al., 1996), or vanadium (Larsen et al., 1997) have been used to improve the sintering of strontium substituted lanthanum chromite. The substitution of strontium and transition metals is often utilized for intercoimects of the planar type... 

In this special field, earlier work had been done in other laboratories, such as by the Schering Company, Berlin (36), and by Ipatieff (37) in connection with his work on the hydrogenation of camphor and of other organic compounds. At both places, the favorable effect of alkali oxides and earth alkali oxides on nickel, cobalt and copper has been investigated. Similarly, Paal and his coworkers (38) have used a palladium-aluminum hydroxide catalyst in 1913 for the hydrogenation of double bonds. Bedford and Erdman (39) had reported that the catalytic action of nickel oxide is enhanced by the oxides of aluminum, zirconium, titanium, calcium, lanthanum, and magnesium. 

Lanthanum [7439-91-0] M 138.9, m 920 , b 3470 , d 6.16. White metal that slowly tarnishes in air due to oxidation. Slowly decomposed by H2O in the cold and more rapidly on heating to form the hydroxide. The metal is cleaned by scraping off the tarnished areas until the shiny metal is revealed and stored under oil or paraffin. It burns in air at 450°. 

Arsenites of the Rare Earth Metals.—When cerium dioxide is heated with arsenious oxide some oxidation of the latter occurs, but the product appears to be a mixture of oxides.5 Didymium hydrogen orthoarsenite, Di2(HAs03)3, has been obtained6 as a white, granular, insoluble powder by boiling didymium hydroxide with an aqueous solution of arsenious oxide. Lanthanum hydrogen orthoarsenite, La2(HAs03)3, has been prepared in a similar manner. The existence of these compounds needs confirmation, however.7... 

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