37 results about "Lanthanum hydroxide" patented technology

The invention relates to a dephosphorization material, a preparation method thereof and a dephosphorization method, belongs to the field of water treatment, and solves at least one of the problems of contradiction between adsorption capacity and structural stability, fast capacity fading, short service life, difficult recovery, higher cost and the like of the existing lanthanum-based dephosphorization material. The phosphorus removal material is a nano-porous carbon-supported lanthanum composite material, and comprises an amorphous nano-porous carbon matrix, an amorphous nano-porous carbon carrier, an amorphous nano-porous carbon carrier, and an amorphous nano-porous carbon carrier, and an active component embedded in situ in the nanoporous carbon matrix; wherein the active component comprises lanthanum oxide and / or lanthanum hydroxide. According to the invention, the adsorption capacity is high, the structure is stable, the attenuation of the adsorption capacity is delayed, the service life is prolonged, the cost is reduced, and the adsorbent can be recycled.

Provided here are methods for producing a shaped metal-supported catalyst. One such method includes the steps of mixing a support hydroxide with an aqueous mixture of an active metal compound to form a malleable mixture of an active metal incorporated support hydroxide, passing the malleable mixture through a molding device to produce a shaped metal-supported wet catalyst; and drying and calcining the shaped metal-supported wet catalyst. The support hydroxide contains one or more of aluminium hydroxide, silica hydroxide, zirconia hydroxide, cerium hydroxide, titanium hydroxide, lanthanum hydroxide, gallium hydroxide, or niobium hydroxide. The active metal compound can be one or more of vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, and rhenium.

The invention discloses a copper-cobalt alloy / lanthanum hydroxide heterojunction catalyst and a preparation method and application thereof.The preparation method includes the steps that lanthanum-based perovskite oxide LaCu (1-x) CoxO3 is prepared through a sol-gel method, and x is equal to 0.1-0.5; laCu1-xCoxO3 is placed in hydrogen and argon mixed gas for reduction treatment, and the copper-cobalt alloy / lanthanum hydroxide heterojunction catalyst is obtained and used for preparing ammonia through electro-catalysis nitrate radical reduction. According to the preparation method, an in-situ dissolution strategy is adopted, a copper-cobalt alloy / lanthanum hydroxide strong interface coupled heterostructure is constructed, CuCo alloy nanoparticles provide high conductivity and rich active sites and form a heterostructure with La (OH) 3, the d-band center of the active sites is optimized through interaction of strong electrons, NO3 <-> adsorption and reaction intermediate stability are promoted, and the stability of the reaction intermediate is improved. The excellent electro-catalytic performance is realized.

The application provides a porous carbon nanofiber electrocatalyst loaded with cobalt / lanthanum hydroxide heterojunction and a preparation method. The preparation method comprises the following steps: adding 4,4-diamino diphenyl ether and pyromellitic dianhydride into a solvent, uniformly mixing, and preparing a polyamide acid precursor spinning solution; electrospinning the prepared polyamide acid precursor spinning solution to prepare polyamide acid nanofibers; immersing the prepared polyamide acid nanofibers in a mixed metal salt solution containing cobalt salt, lanthanum salt and zinc salt to prepare polyamide acid nanofiber precursors loaded with metal ions; and performing programmed temperature heat treatment on the prepared polyamide acid nanofiber precursors loaded with metal ions in a protective atmosphere to prepare the porous carbon nanofiber electrocatalyst loaded with cobalt / lanthanum hydroxide heterojunction. The prepared porous carbon nanofiber electrocatalyst loaded with cobalt / lanthanum hydroxide heterojunction has excellent electrochemical oxygen reduction reaction and oxygen evolution reaction bifunctional catalytic activity.

The invention relates to the technical field of lanthanum oxycarbonate, and discloses a lanthanum oxycarbonate catalyst and a preparation method and application thereof, and the lanthanum oxycarbonate catalyst comprises hexagonal crystal phase lanthanum oxycarbonate and hexagonal crystal phase lanthanum oxycarbonate containing a doping element R. The method comprises the following steps: (1) adding alkali liquor into a solution of a lanthanum source, and then carrying out solid-liquid separation and drying to obtain lanthanum hydroxide; (2) contacting a solution of a compound containing a doping element R with lanthanum hydroxide, and then drying; and (3) roasting the dried product in the step (2) in a carbon-containing atmosphere to obtain the lanthanum oxycarbonate catalyst. When the catalyst prepared by the method is used for the oxidative coupling reaction of methane, the yield of C2 hydrocarbon is relatively high.

A process for manufacturing a lanthanum oxycarbonate powder comprising the following steps: a step of grinding an initial powder comprising lanthanum hydroxide La(OH)3 in the presence of a control agent, said control agent comprising ethylene glycol and said grinding resulting in a paste and a subsequent step wherein said paste is subjected to a heating step allowing the oxidation of the La(OH)3 powder into a La2O2CO3 powder. Figure for abstract: no figure

Polymeric composition comprising a thermoplastic polyester and a rare earth compound selected from the group consisting of lanthanum hydroxide, cerium oxide hydrate and mixtures thereof, characterized in that the amount of the thermoplastic polyester in the polymeric composition is more than 50 wt. %, preferably more than 70 wt. %.

The invention discloses a preparation method of a rare earth hydroxide nanowire, and belongs to the technical field of composite materials, and the preparation method specifically comprises the following steps: firstly, dissolving rare earth salt in deionized water, slowly dripping a surfactant into the solution, and adding an ammonia water solution to adjust the pH value of a reaction system to be greater than 10 to obtain a reaction solution; and putting the reaction liquid into a hydrothermal reaction kettle, reacting for 12 hours at the temperature of 200 DEG C, and synthesizing a rare earth hydroxide nanowire product. The preparation method adopts a hydrothermal synthesis technology, is relatively simple and controllable, and avoids the use of high-cost and pollution-free reagents. The preparation method is simple, the reaction temperature is low, the yield of the nanowire reaches 70% or above, and the prepared lanthanum hydroxide nanowire is large in length-diameter ratio and good in dispersity.

The invention discloses an application of lanthanum hydroxide rich in oxygen vacancy in electro-catalysis florfenicol hydrogenolysis dechlorination, a preparation method of the lanthanum hydroxide rich in oxygen vacancy comprises the following steps: (1) adding alkali liquor into a lanthanum source solution, and then performing aging, solid-liquid separation and drying to obtain lanthanum hydroxide; (2) adding a glucose solution into the lanthanum hydroxide obtained in the step (1), and then drying; (3) grinding the dried product obtained in the step (2), and calcining in a nitrogen atmosphere to obtain lanthanum hydroxide rich in oxygen vacancy; loading lanthanum hydroxide rich in oxygen vacancy on a conductive substrate to prepare a working electrode; and taking the working electrode as a cathode of an electrochemical reaction device, and adding florfenicol-containing wastewater to carry out an electrocatalytic hydrogenolysis dechlorination reaction. The lanthanum hydroxide rich in oxygen vacancy can efficiently degrade the antibiotic florfenicol, and shows high florfenicol degradation rate and dechlorination rate.

The invention provides a multi-element alloy co-permeation agent and application thereof, the multi-element alloy co-permeation agent comprises composite zinc-aluminum alloy powder, Zn powder, composite AIMg alloy powder and a rare earth compound, and the rare earth compound comprises lanthanum hydroxide. By adopting the combination of the composite zinc-aluminum alloy powder, the Zn powder, the composite AIMg alloy powder and the rare earth compound, an efficient anti-corrosion coating can be formed on the surfaces of parts such as railway equipment, bolts and spikes, and the corrosion resistance of the parts is remarkably improved. Especially in an open-air environment, the coating can effectively resist corrosion of wind, sunlight and acidic materials, and the service life of equipment is prolonged.

The present application relates to the technical field of medicine and chemical industry, in particular to a kind of alginate / nano lanthanum hydroxide composite microspheres and its preparation method and application.The composite microspheres use sodium alginate as organic matrix material, and nano lanthanum hydroxide as inorganic filling phase, which are prepared by electrospray technology, and can realize the uniform dispersion and wrapping of nano lanthanum hydroxide in alginate microspheres.The size of the composite microspheres can be adjusted as needed between 235.5 μm and 748.4 μm, and the mass ratio of alginate to nano lanthanum hydroxide can be adjusted as needed within 1: (0.5-1.5).The composite microspheres of the present application have a phosphorus binding capacity of 41.0 mg / g-90.0 mg / g in a gastric acid environment with pH=2, and excellent phosphorus binding ability, which can be used as an oral phosphorus binding agent for the treatment of hyperphosphatemia, providing a new technical solution for clinical intervention of hyperphosphatemia.

The invention provides a method for preparing a lanthanum hydroxide phosphate adsorbent through potassium borohydride reduction, and belongs to the technical field of adsorbents. The adsorption mechanism is based on chemical adsorption phosphorus removal, potassium borohydride is added into a lanthanum nitrate solution to realize reduction oxidation of lanthanum ions, a nano phosphorus removal material with the average size smaller than 10 nanometers is formed, and the porous non-fixed type porous hydrogel is formed through a series connection process. Compared with a conventional powdery adsorbent and a directly synthesized lanthanum hydroxide adsorbent, the lanthanum hydroxide adsorbent has the advantage that the adsorption performance of lanthanum hydroxide to phosphate is multiplied by introducing a reduction-oxidation process.

The application discloses a silver-nickel electric contact material added with lanthanum oxide and a preparation method thereof. The method comprises the following steps: calculating the required amounts of lanthanum oxide, nickel powder and Ag element for preparing the contact, weighing the Ag element as silver nitrate and preparing a silver nitrate solution by adding water; first, reacting the lanthanum oxide with the silver nitrate solution, calculating the total amount of sodium hydroxide required for completely reacting the generated lanthanum nitrate and the unreacted silver nitrate with sodium hydroxide to generate lanthanum hydroxide and silver oxide respectively, weighing the sodium hydroxide and preparing a sodium hydroxide solution by adding water; then, reacting the sodium hydroxide solution with the aforementioned suspension to obtain a composite powder of silver oxide and lanthanum hydroxide; washing the composite powder to neutral, drying and roasting to obtain a silver-lanthanum hydroxide composite powder; and mixing the obtained silver-lanthanum hydroxide composite powder with the nickel powder, and then performing the processes of isostatic pressing, sintering and extrusion to obtain the silver-nickel electric contact material. The method can make the lanthanum oxide more uniformly distributed in the silver matrix, and obtain a uniform metallographic structure.

The invention discloses a steel member alloy co-permeation anti-corrosion process, and particularly relates to the technical field of zinc impregnation treatment, and the steel member alloy co-permeation anti-corrosion process comprises the following process steps: step 1, spraying a lanthanum hydroxide-containing ethanol activating solution on the surface of a polished steel member, drying and then charging; step 2, adding an impregnation agent into the zinc impregnation furnace layer by layer, wherein the bottom layer is an aluminum oxide anti-sticking agent, the middle layer is a mixture of zinc powder, aluminum powder, ammonium chloride and nano silicon dioxide, and the covering layer is a mixture of zinc powder and lanthanum hydroxide; and step 3, gradient temperature rise. According to the technology, under the condition of being compatible with an existing production line of a traditional technology, through the four innovative steps of rare earth pre-activation, gradient heating, dynamic zinc supplementing and inert gas cooling, the corrosion-resistant service life of a zinc impregnation layer is doubled, the workpiece deformation rate approaches zero, the cooling efficiency is improved, meanwhile, the cost of an anti-sticking agent and the loss of zinc powder are reduced, the comprehensive production cost is reduced, and the production efficiency is improved. And the industrial-grade precise zinc impregnation standard of zero rework, zero adhesion and zero performance fluctuation is achieved.

The present invention belongs to the technical field of metal materials, and specifically relates to a high-strength ultra-fine tungsten alloy wire and a preparation method thereof. A high-strength ultra-fine tungsten alloy wire, the tungsten alloy wire comprising the following components in weight percentage: 98.5-99.95% tungsten powder, 0.05-1.5% lanthanum hydroxide powder. The present invention provides a high-strength ultra-fine tungsten alloy wire and a preparation method thereof, which obtains a tungsten alloy powder with a uniform distribution of rare earth oxides by efficiently doping a solid (tungsten powder)-solid (lanthanum hydroxide) mixture. The tungsten alloy wire is doped with lanthanum hydroxide instead of lanthanum oxide, because lanthanum oxide easily absorbs water and denatures, resulting in the breakage of the tungsten bar after pressing; then the sintered tungsten alloy billet (20-30 mm) is continuously rolled to 3.0-4.0 mm, and finally, it is drawn to the required specifications by a wire drawing machine, thereby solving the problems of uneven mixing, low strength, high wire breakage rate, low efficiency, and low yield rate of the existing process.

This invention relates to the field of water treatment agents, specifically to a compound defluoridating agent, its preparation method, and its application in industrial wastewater. The defluoridating agent provided by this invention comprises component A and component B. Component A is prepared by mixing polyaluminum ferric chloride, aluminum salt, and magnesium salt; component B comprises a lanthanum-doped biochar-montmorillonite composite material and calcium chloride supported thereon. The lanthanum-doped biochar-montmorillonite composite material is prepared through chitosan-montmorillonite intercalation, lanthanum hydroxide loading, and nitrogen pyrolysis carbonization. In application, the pH of the fluoride-containing industrial wastewater is first adjusted to 5-6, component A is added, and the mixture is stirred and allowed to settle to remove most of the fluoride ions. Then, the pH of the supernatant is adjusted to 8-9, component B is added, and the mixture is stirred and allowed to settle to further remove residual fluoride ions. The defluoridating agent of this invention can achieve a defluoridation rate of over 99% for industrial wastewater, with stable fluoride content in the effluent meeting standards, demonstrating good prospects for industrial application.

The present application relates to the technical field of oxy-lanthanum carbonate, and discloses an oxy-lanthanum carbonate catalyst, a preparation method and application thereof, the oxy-lanthanum carbonate catalyst comprising hexagonal crystal phase oxy-lanthanum carbonate and hexagonal crystal phase oxy-lanthanum carbonate containing doping element R.The method comprises the following steps: (1) adding an alkali solution into a solution of a lanthanum source, and then performing solid-liquid separation and drying to obtain lanthanum hydroxide; (2) contacting a solution containing a compound of doping element R with the lanthanum hydroxide, and then performing drying; (3) performing calcination on the dried product of step (2) in a carbon-containing atmosphere to obtain the oxy-lanthanum carbonate catalyst.The catalyst prepared by the present application has a high carbon dihydrocarbon yield when used in a methane oxidative coupling reaction.

The application discloses a preparation method of a functional lanthanum hydroxide composite PEO-based solid electrolyte for a solid-state battery, and relates to a preparation method of a PEO-based solid electrolyte.The application solves the problems of poor contact with an electrode plate, low ion transmission and unstable interface of an existing PEO electrolyte.The preparation method comprises the following steps: one, preparation of functional group modified La(OH)3-NH2 nanofibers; and two, preparation of a PEO-based composite solid electrolyte.The application is used for the preparation of the functional lanthanum hydroxide composite PEO-based solid electrolyte for the solid-state battery.

The present application relates to the technical field of oxy-lanthanum carbonate, and discloses an oxy-lanthanum carbonate catalyst, a preparation method and application thereof, the oxy-lanthanum carbonate catalyst comprising hexagonal crystal phase oxy-lanthanum carbonate and hexagonal crystal phase oxy-lanthanum carbonate containing a doping element.The method comprises the following steps: (1) adding an alkali solution into a solution of a lanthanum source, then performing aging, solid-liquid separation and drying to obtain lanthanum hydroxide; (2) under a protective atmosphere, contacting a solution of a compound containing a doping element with the lanthanum hydroxide, and then performing drying; (3) performing calcination on the dried product of step (2) under an atmosphere containing CO2 to obtain the oxy-lanthanum carbonate catalyst.The catalyst prepared by the present application has a high carbon dihydrocarbon yield when used in a methane oxidative coupling reaction.

The invention relates to a method for producing a lanthanum oxycarbonate powder, comprising the following steps: an initial step of grinding a powder comprising lanthanum hydroxide La(OH)3 in the presence of a control agent, the control agent comprising ethylene glycol and the grinding resulting in a paste, and a subsequent step in which the paste is subjected to a heating step for oxidising the La(OH)3 powder to give an La2O2CO3 powder.

The invention relates to a polyester industrial yarn containing a rare earth flame retardant, raw materials of the polyester industrial yarn mainly comprise the rare earth flame retardant, the mass fraction of the rare earth flame retardant in the polyester industrial yarn is 6-9%, the rare earth flame retardant is a compound of porous carbon aerogel, and the components of the rare earth flame retardant mainly comprise porous carbon aerogel and lanthanum hydroxide. The preparation method has the technical characteristics that the physical barrier of the porous carbon aerogel is combined with the chemical flame retardancy of lanthanum hydroxide and magnesium hydroxide to form a multi-scale synergistic flame-retardant system of adsorption, heat absorption, oxygen isolation and char formation, so that the efficient and continuous flame-retardant property of the polyester is remarkably improved.

This invention relates to a long-chain alkyl surfactant-mediated lanthanum hydroxide material, its preparation method, and its applications. The lanthanum hydroxide material is synthesized by alkaline co-thermal precipitation of a soluble lanthanum salt and alkyltrimethylammonium bromide in a pressure-resistant reactor under closed conditions. This yields a long-chain alkyl surfactant-mediated lanthanum hydroxide material with optimal adsorption performance, suitable for removing phosphorus nutrients from low-concentration phosphorus wastewater. Compared with existing technologies, the long-chain alkyl surfactant-mediated lanthanum hydroxide material provided by this invention not only possesses good dispersibility but also exhibits higher phosphorus adsorption capacity and rate through the regulation of its physicochemical properties. Compared with lanthanum hydroxide prepared by conventional hydrothermal precipitation methods, its phosphorus separation performance is significantly higher.

The invention provides a crystallization defluorination method for fluorine-containing wastewater in the presence of high-concentration sulfate radicals, and belongs to the technical field of water treatment.The crystallization defluorination method comprises the following steps that before defluorination is conducted on fluorine-containing water containing the high-concentration sulfate radicals, lanthanum fluoride crystal seeds, a composite regulator and a defluorination agent lanthanum hydroxide are added into the water, crystallization reaction conditions are controlled, and the fluorine-containing water containing the high-concentration sulfate radicals is obtained. Enabling fluorine ions and lanthanum hydroxide to form a stable fluorine lanthanum compound crystal through directional crystallization; fluorine lanthanum compound crystals are removed through solid-liquid separation, and deep fluorine removal of the water body is achieved. According to the present invention, with the lanthanum hydroxide crystallization method, by using the extremely low solubility product of the fluorine lanthanum compound, the efficient fixation of the fluorine ions can still be achieved under the interference of the high-concentration sulfate radical, the fluorine concentration of the treated water body is stably reduced to less than 10 mg / L, the secondary pollution is avoided, and the defects of poor selectivity and easy saturation in the high sulfate radical environment of the traditional adsorption method are overcome; the method is suitable for treating high-salt fluorine-containing water bodies such as mining area wastewater and metallurgical fluorine-containing wastewater.

The invention relates to a polyetheretherketone (PEEK) composition (I), and the PEEK composition (I) contains lanthanum hydroxide. Lanthanum hydroxide was found to be useful for long-term stabilization of PEEK compositions at temperatures of 210 DEG C to 300 DEG C, preferably 230 DEG C to 270 DEG C, for a time period of 500 hours or longer, preferably 1000 to 3000 hours or longer. # imgabs0 #

The invention relates to the technical field of carbon dioxide adsorption, and discloses lanthanum hydroxide with a carbon dioxide adsorption function as well as a preparation method and application thereof, the lanthanum hydroxide has a rod-like structure, the length of the rod-like structure is 50-300nm, the diameter of the rod-like structure is 10-30nm, and the length-diameter ratio of the rod-like structure is 5-20. The invention discloses a method for preparing lanthanum hydroxide. The method comprises the following steps: (1) adding alkali liquor into an aqueous solution of lanthanum salt to adjust the pH value of the aqueous solution to be greater than 7; (2) performing three-frequency ultrasonic treatment on the material obtained in the step (1); and (3) drying a solid material obtained by separating the material subjected to the three-frequency ultrasonic treatment. The lanthanum hydroxide can effectively adsorb carbon dioxide, so that removal of carbon dioxide in reaction tail gas is realized, and the lanthanum hydroxide has relatively high carbon dioxide adsorption capacity and is particularly suitable for removing carbon dioxide in reaction tail gas of oxidative coupling of methane.

The invention provides a cobalt / lanthanum hydroxide heterojunction loaded porous carbon nanofiber electrocatalyst and a preparation method thereof.The preparation method comprises the steps that 4, 4-diaminodiphenyl ether and pyromellitic dianhydride are added into a solvent and mixed to be uniform, and a polyamide acid precursor spinning solution is prepared; the prepared polyamide acid precursor spinning solution is subjected to electrostatic spinning, and polyamide acid nanofibers are prepared; dipping the prepared polyamide acid nanofiber in a mixed metal salt solution containing cobalt salt, lanthanum salt and zinc salt to prepare a polyamide acid nanofiber precursor loaded with metal ions; the prepared polyamide acid nanofiber precursor loaded with the metal ions is subjected to temperature programming heat treatment in a protective atmosphere, and the cobalt / lanthanum hydroxide heterojunction loaded porous carbon nanofiber electrocatalyst is prepared. The prepared cobalt / lanthanum hydroxide heterojunction loaded porous carbon nanofiber electrocatalyst has excellent bifunctional catalytic activity of electrochemical oxygen reduction reaction and oxygen evolution reaction.

The invention relates to the technical field of pharmaceutical chemicals, in particular to alginate / nano lanthanum hydroxide composite microspheres as well as a preparation method and application thereof. The composite microsphere is prepared by taking sodium alginate as an organic matrix material and nano lanthanum hydroxide as an inorganic filling phase through an electrospray technology, and the nano lanthanum hydroxide can be uniformly dispersed and wrapped in the alginate microsphere; the size of the composite microsphere can be adjusted between 235.5 microns and 748.4 microns as required, and the mass ratio of the alginate to the nano lanthanum hydroxide can be adjusted within 1: (0.5-1.5) as required. The phosphorus binding amount of the composite microspheres still reaches up to 41.0 mg / g-90.0 mg / g in a gastric acid environment with the pH value being 2, the phosphorus binding capacity is excellent, the composite microspheres can serve as an oral phosphorus binding agent to be used for treating hyperphosphatemia, and a novel technical scheme is provided for clinical intervention of the hyperphosphatemia.

The invention discloses an amorphous Cu / Si-LOC catalyst, a preparation method thereof and application of the amorphous Cu / Si-LOC catalyst in methanol preparation through CO2 hydrogenation, and belongs to the technical field of catalysts. The invention solves the problems of difficult CO2 activation, low methanol selectivity, easy sintering inactivation and the like of the catalyst in the prior art. The preparation method of the catalyst comprises the following steps: reacting lanthanum nitrate with stronger ammonia water to generate lanthanum hydroxide, and reacting the lanthanum hydroxide with tetraethyl orthosilicate to obtain a Si-LOC carrier; and carrying out ultrasonic dispersion on the carrier, and adding a copper source to obtain the Cu / Si-LOC catalyst. The amorphous Si-LOC carrier with rich specific surface area and surface defect sites is obtained through silicon doping, adsorption and activation of CO2 are promoted, and adsorption and further hydrogenation of an intermediate are enhanced through loading of Cu. In addition, the catalyst is not easy to sinter and inactivate. The catalyst is applied to a CO2 hydrogenation reaction, and efficient conversion of CO2 can be realized at a relatively low temperature.

A method of immobilizing contaminants disposed in an aqueous medium, the method comprising: contacting the aqueous medium with a particulate crystalline nanocomposite for a sufficient contact time to permit adsorption of the contaminants. The particulate crystalline nanocomposite comprises: a hexagonal lanthanum hydroxide (La(OH)3) crystalline phase; a lanthanum oxide (La2O3) crystalline phase; a monoclinic calcium silicate (CaSiO3) crystalline phase; and, a graphitic carbon nitride (g-C3N4) crystalline phase, wherein at least a fraction of the g-C3N4 is in the form of mesoporous nanosheets.

A lanthanum dioxide carbonate catalyst, a preparation method and a use thereof are provided. The lanthanum dioxide carbonate catalyst comprises hexagonal crystalline lanthanum dioxide carbonate and hexagonal crystalline lanthanum dioxide carbonate containing a doping element R. The method includes the steps of (1) adding an alkali solution to a solution of lanthanum source, and then performing a solid-liquid separation and a drying to obtain lanthanum hydroxide; (2) contacting a solution of a compound containing the doping element R with lanthanum hydroxide, and then performing a drying; (3) calcining the dried product of step (2) under a carbon-containing atmosphere to obtain a lanthanum dioxide carbonate catalyst.