Exxon Research and Engineering Company

Harold S Horowitz

John M Longo

Joseph T Lewandowski

Joel I Haberman

LeRoy R Clavenna

Hugh H Horowitz

A method of preparing electrically conductive pyrochlore compounds of high surface area and unagglomerated form, having the formula

Method of synthesizing high surface area unagglomerated noble metal

A method for electrocatalytically reacting various oxidizable organic compounds by introducing current by means of an anode into an electrolyte of a cell containing the oxidizable organic compound. The anode comprises an electrocatalyst material which has at least one compound of the formula:

Method of electrocatalytic oxidation of organic compounds

A method of preparing electrically conductive pyrochlore compounds having the formula:

Method of making lead and bismuth pyrochlore compounds using an alkaline

A liquid solution method of preparing electrically conductive pyrochlore compounds having the formula:

Method of making lead and bismuth ruthenate and iridate pyrochlore

A liquid solution method of preparing electrically conductive pyrochlore compounds of high surface area, having the formula:

Method of making lead-rich and bismuth-rich pyrochlore compounds using

Method of making stoichiometric lead and bismuth pyrochlore compounds

Novel bismuth-rich pyrochlore-type compounds are described having the formula:

Bi.sub.2 [M.sub.2-x Bi.sub.x ]O.sub.7-y compounds wherein M is Ru, Ir or

An electrochemical device is described which has an oxygen electrode which contains a pyrochlore type electrocatalyst material. This electrocatalyst material is one or more electrically conductive pyrochlore compounds selected from the compounds of the following formula:

Electrochemical device having an oxygen electrode containing a

Novel lead-rich pyrochlore type compounds are described having the formula:

Pb.sub.2 [M.sub.2-x Pb.sub.x ]O.sub.7-y compounds wherein M is Ru, Ir or

Mixed metal oxides of the formula CaMn.sub.3 O.sub.6, CaMn.sub.4 O.sub.8 and CaMn.sub.7 O.sub.12 are disclosed. They are useful in electrochemical processes. CaMn.sub.3 O.sub.6 is a mixed valence composition whose formula may be written as Ca[Mn.sub.2.sup.3+ Mn.sup.4+ ]O.sub.6. The compound is stable in H.sub.2 to about 400.degree. C. and in oxygen to approximately 925.degree. C. CaMn.sub.4 O.sub.8 is also a mixed valence composition whose formula may be written Ca[Mn.sub.2.sup.3+ Mn.sub.2.sup.4+ ]O.sub.8. This compound is stable in H.sub.2 to about 250.degree. C. and in O.sub.2 to about 900.degree. C. CaMn.sub.7 O.sub.12 is a mixed valence composition whose formula may be written as Ca[Mn.sup.4+ Mn.sub.6.sup.3+ ]O.sub.12. The compound is stable in H.sub.2 to about 500.degree. C. and in oxygen to approximately 950.degree. C. These materials may be prepared by a variety of standard ceramic techniques, among them being heating in oxygen a mixture of calcium oxide and manganese oxide or mixed calcium and manganese salts or calcium salt and manganese oxide, or calcium oxide and manganese salt. Alternatively, solid solutions of mixed calcium and manganese carbonates may be decomposed to the compositions. The mixed calcium-manganese carbonate solid solutions are prepared by the precipitation from salt solution of the calcium and manganese by the addition of an excess of an appropriate carbonate ion source such as (NH.sub.4).sub.2 CO.sub.3. The metal ion ratio in this salt solution is adjusted so that the resulting precipitate has the same stoichiometry as the desired oxide. The precipitate is calcined to yield the mixed metal oxide product described. The compounds described have utility as primary battery cathodes and also find use as oxygen activating catalysts in applications such as partial oxidation; methanol decomposition and oxygen reduction at a fuel cell cathode.

Use of high surface area mixed metal oxides of manganese and calcium in

A process for the preparation of high surface area mixed metal oxides by decomposition of solid solutions of carbonates possessing the calcite structure. Oxide compounds comprising mixtures of Ca, Mn, Fe, Co, Ni, Zn, Cd and Mg can be prepared by this method. For example, CaMnO.sub.3 with a surface area of 11 m.sup.2 /g useful as a battery cathode, has been prepared by the instant method, that is, by decomposition of a CaMn(CO.sub.3).sub.2 precursor. The mixed metal carbonate solid solutions which are used as precursors for the preparation of the mixed metal oxides are themselves prepared by the precipitation from solution of the appropriate metal ions by the addition of an excess of a carbonate ion source (such as (NH.sub.4).sub.2 CO.sub.3). The metal-ion ratio in this solution is adjusted so that the resulting precipitate has the same stoichiometry as the desired oxide. The intimate mixing achieved by using the carbonate precipitation technique allows calcination to metal oxide to be run at lower temperatures for shorter periods of time, thereby achieving higher surface areas.

Preparation of mixed metal oxides by decomposition of carbonate solid

A new low temperature layered manganese compound of the formula Ca.sub.2 Mn.sub.3 O.sub.8 has unexpectedly been synthesized in pure form. The unit cell dimensions of this new compound have been determined by X-ray diffraction and reveal that the compound is monoclinic with lattice parameters of a=11.02 A, b=5.85 A, c=4.94 A, .alpha.=90.degree., .beta.=109.80.degree., .gamma.=90.degree.. The structure consists of pseudohexagonal Mn.sup.4+ sheets with similar oxygen sheets on either side, giving a distorted octahedral coordination to the Mn.sup.4+. Every fourth Mn.sup.4+ is missing in these layers, so their composition is Mn.sub.3 O.sub.8 with chains of coordination octahedra linked by common edges (rutile type arrangement). The Ca ions are situated between the Mn.sub.3 O.sub.8 layers. This new Ca.sub.2 Mn.sub.3 O.sub.8 compound is prepared in pure form by means of the solid solution precursor technique whereby solid solution, mixed metal carbonates of the desired metals (Ca and Mn) having the calcite structure are precipitated from mixtures of the solutions of the salts of calcium and manganese, said salts being selected from the group consisting of carbonates, nitrates, sulfates, oxalates, acetates, precipitation being the result of the addition of a source of carbonate ions, such as ammonium carbonate, sodium carbonate, potassium carbonate of CO.sub.2, so as to achieve mixing on the atomic scale. The resulting solid solution mixed metal carbonate is subsequently calcined, preferably at a temperature of from between 600.degree.-875.degree.C to the mixed metal oxide in the pure form possessing high surface area (on the order of 20-50 m.sup.2 /g). This new material has uses as a battery cathode.

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Clark, NJ, United States of America

Harold S Horowitz