Lanthanum cobaltate catalysts

Lanthanum cobaltate catalysts carbon monoxide oxidation, kinetics, 36 281-283... 

The relatively high cost and lack of domestic supply of noble metals has spurred considerable efforts toward the development of nonnoble metal catalysts for automobile exhaust control. A very large number of base metal oxides and mixtures of oxides have been considered, especially the transition metals, such as copper, chromium, nickel, manganese, cobalt vanadium, and iron. Particularly prominent are the copper chromites, which are mixtures of the oxides of copper and chromium, with various promoters added. These materials are active in the oxidation of CO and hydrocarbons, as well as in the reduction of NO in the presence of CO (55-59). Rare earth oxides, such as lanthanum cobaltate and lanthanum lead manganite with Perovskite structure, have been investigated for CO oxidation, but have not been tested and shown to be sufficiently active under realistic and demanding conditions (60-63). Hopcalities are out-... 

Support modification has been reported earlier in the open literature [5,6,7,8,9]. Zirconia modification of silica supports was used to prevent the formation of unreducible cobalt-silicates [5]. Zr, Ce, Hf, or U modification of titania supports was reported to prevent the formation of cobalt-titanates during regeneration [6]. To increase the porosity of titania supports, they were modified with small amounts of binders, e.g. silica, alumina or zirconia [7]. Lanthanum oxide promotion of alumina was reported to be beneficial for improved production of products with higher boiling points [8], and zirconia modification of alumina supports was carried out to decrease the interaction of cobalt with alumina [9]. All these modified supports were either used for fixed bed cobalt based Fischer-Tropsch synthesis catalysts or they were used for slurry phase cobalt catalysts, but not tested under realistic Fischer-Tropsch synthesis conditions in large scale slurry bed reactors. 

Silica-supported cobalt catalysts were prepared from cobalt nitrate (Co(N03)2), lanthanum nitrate (La(N03)3) and commercially available silica gel (Fuji Davison, ID gel, 270 m /g) using conventional methods of impregnation [14]. The composition of the catalyst was Co La Si02 = 20 6 87 by weight. The catalyst precursor was dried in air at 120°C and then calcined at 450 °C for 3 h to form supported metal oxides. It was then exposed to hydrogen at 400 °C for 12 h. The mean pore diameter of the catalyst was 8.7 nm. 

Rosa et al. [251] investigated catalysts for autothermal reforming of diesel. Numerous systems were tested. Firstly, platinum, ruthenium, cobalt and nickel catalysts on an alumina carrier promoted with magnesium and lanthanides to improve thermal stability were investigated. The second set of samples was composed of cobalt perovsldte catalysts. In addition, Rosa et al. investigated ruthenium and platinum catalysts on lanthanum/cobalt perovsldtes. The samples were tested at gas hourly space velocities of between 20 000 and 80 000 h and S/C ratios from 3 to 5. The O/C ratio was set to between 0.4 and 1.4 and the temperature to 650-900 °C. Amongst the first set of samples, platinum stabilised by a dual set of lanthanum stabilisers, that were not disclosed, showed improved performance over nickel and ruthenium. The optimum conditions were 750 °C reaction temperature,... 

Barnard, K.R., Foger, K., Turney, T.W., and Williams, R.D. (1990) Lanthanum cobalt oxide oxidation catalysts derived from mixed hydroxide precursor. /. Catal, 125 (2), 265-275. 

It is well known that the major limitation of the application of perovskites as combustion catalysts is their lower surface area and their increased tendency to sinter. One solution to increase the contact surface between the VOC and the perovskite is to disperse it on a large surface area and thermally stable support. Thus, supported LaCoOs perovskites on CeZr02 have been studied recently. The use of a CeZr02 support for lanthanum cobalt perovskites promoted the catalytic activity with respect to the corresponding bulk perovskites, decreasing the temperature for complete toluene oxidation by more than 50 C. The increased activity was related to two factors (i) the larger exposed surface and (ii) the composition of the support which provided the increased oxygen mobility of the catalyst. 

Catalysts used for preparing amines from alcohols iaclude cobalt promoted with tirconium, lanthanum, cerium, or uranium (52) the metals and oxides of nickel, cobalt, and/or copper (53,54,56,60,61) metal oxides of antimony, tin, and manganese on alumina support (55) copper, nickel, and a metal belonging to the platinum group 8—10 (57) copper formate (58) nickel promoted with chromium and/or iron on alumina support (53,59) and cobalt, copper, and either iron, 2iac, or zirconium (62). 

Reduction of sulfur dioxide by methane is the basis of an Allied process for converting by-product sulfur dioxide to sulfur (232). The reaction is carried out in the gas phase over a catalyst. Reduction of sulfur dioxide to sulfur by carbon in the form of coal has been developed as the Resox process (233). The reduction, which is conducted at 550—800°C, appears to be promoted by the simultaneous reaction of the coal with steam. The reduction of sulfur dioxide by carbon monoxide tends to give carbonyl sulfide [463-58-1] rather than sulfur over cobalt molybdate, but special catalysts, eg, lanthanum titanate, have the abiUty to direct the reaction toward producing sulfur (234). 

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. 

Reduction with carbon monoxide at high temperatures can form either carbonyl sulfide or sulfur depending on the catalyst used. With cobalt molybdate, COS is the primary product. On the other hand, lanthanum titanate catalyzes the reaction to form sulfur. 

In the 1990 s research on the replacement of the noble metals (platinum, rhodium, palladium) in the catalyst has centered on oxides of cobalt with smaller amounts of co-catalysts such as lanthanum metal and oxides of scandium, yttrium and lanthanum. It is believed that new catalyst designs will provide more-efficient, lighter-weight gauzes that will reduce (but not eliminate) the amount of platinum required91. 

Complex oxides of the perovskite structure containing rare earths like lanthanum have proved effective for oxidation of CO and hydrocarbons and for the decomposition of nitrogen oxides. These catalysts are cheaper alternatives than noble metals like platinum and rhodium which are used in automotive catalytic converters. The most effective catalysts are systems of the type Lai vSrvM03, where M = cobalt, manganese, iron, chromium, copper. Further, perovskites used as active phases in catalytic converters have to be stabilized on the rare earth containing washcoat layers. This then leads to an increase in rare earth content of a catalytic converter unit by factors up to ten compared to the three way catalyst. 

An earlier review of the promoter literature revealed that cerium, cobalt, chromium, copper, iron, hafnium, lanthanum, molybdenum, niobium, nickel, titanium, and zirconium are elements that are commonly reported to enhance the activity (170). Cations of these elements are suggested to form solid solutions with the catalyst, KVO)yMi (where M is a... 

Use Lanthanum salts, electronic devices, pyrophoric alloys, rocket propellants, reducing agent catalyst for conversion of nitrogen oxides to nitrogen in exhaust gases (usually in combination with cobalt, lead, or other metals), phosphors in x-ray screens. 

Molybdenum catalysts, Ruthenium porphyrins, Ruthenium(lll) complexes, Iron catalysts, Titanium catalysts. Sharpless epoxidation, Tungsten catalysts, Methyltrioxorhenium, Cobalt, Nickel, Platinum, Aerobic epoxidation, Lanthanum, Ytterbium, Calcium, BINOL-complexes. 2008 Elsevier B.v. 

This process carries out the vapor phase oxychlorination of ethane, in the presence of oxygen or air enriched with oxygen, between 350 and 450°C, and between Oil and 10.10 Pa absolute. It employs a catalyst system based on silver doped by derivatives of manganese, cobalt or nickel, and possibly of rare earths (such as lanthanum), and which is employed in mass form or supported on a Y-type zeolite (offretite). 

Iron and its compounds (carbide, nitride), as well as ruthenium, cobalt, rhodium, and molybdenum compounds (sulfide, carbide), are used most frequently to produce high-molecular-weight hydrocarbons. Iron can be prepared as a high-surface-area catalyst (==300 m /g) even without using a microporous oxide support. 7-AI2O3, Ti02, and silica are frequently used as supports of the dispersed transition-metal particles. Recently zeolites, as well as thorium oxide and lanthanum oxide, have... 

The mono- and bimetallic substituted MCM-41 catalysts with cobalt, vanadium or lanthanum have been prepared by direct synthesis or impregnation and characterized by various techniques, such as XRD, N2 adsorption-desorption, SEM, TEM and TGA. The catalytic activity in the selective oxidation of styrene with H2O2 has been evaluated. Adsorption of benzene and ammonia on the mono- and bimetallic mesoporous molecular sieves with cobalt and vanadium has been studied by IR spectroscopy and the results have been correlated with their catalytic properties and the characteristics of the structure. Co-incorporated catalysts prepared by direct synthesis show to be very active and selective. 

A synergistic effect leading to the increased catalyst activity and selectivity in selective catalytic reduction (SCR) of NO with methane or propane-butane mixtures was found when cobalt, calcium and lanthanum cations were introduced into the protic MFl-type zeolite. This non-additive increase of the zeolite activity is attributed to increased concentration of the Bronsted acid sites and their defined location as result of interaction between those and cations (Co, Ca, La). Activation of the hydrocarbon reductant occurs at these centers. Doping the H-forms of zeolites (pentasils and mordenites) with alkaline earth metal and Mg cations considerably increased the activity of these catalysts and their stability to sulfur oxides. 

Chlorinated alumina-supported metal catalysts are the typical catalysts used today for catalytic naphtha reforming, which is performed at temperatures of480-550 °C (410). Modem versions of this type of catalyst are mul-timetaUic the catalytic properties of platinum are improved by the addition of another metal, often rhenium. Further elements that may be added are tin, silicon, germanium, lead, gallium, indium, iridium, thorium, lanthanum, cerium, cobalt, and nickel. AH these components are supported on chlorinated y-alumina (with a surface area of 150—300 m g ), which provides the acid function (411). 

---