W. R. Grace & Co.

W.r. Grace & Co. -conn.

Other

Moises G Sanchez

Norman R Laine

Michael V Ernest

Stephen Raymond Schmidt

Richard N Hill

Jose E Herrera

Sandra M Waters

Charles C Chang

This application describes ceramic oxide superconductors, their precursors and methods of preparation. The superconductors contain no copper, but comprise the transition metals Nickel or Cobalt (M ) together with bulky cations of Groups 2 and 1 of the Periodic Table (M and M ) such as Ba and K . Their hexagonal crystal structure comprises parallel chains of highly covalent, octahedrally coordinated oxygen around the transition metal, which exhibits its highest valence &plus;4. The octahedra are facet-linked forming polyacid chains or macroanions that run the full length of crystallites or single crystals along the c axis. The chains are separated by distances that prevent covalency or orbital overlap among them. They are held together by coulombic forces from the cations located between them that also run parallel to the c axis. Electrical current, carried by holes, can only flow within the chains. Thus the materials are one-dimensional superconductors of composition M M M O .

One dimensional ceramic conductive oxides

Catalysts which are suitable for auto exhaust use are made with a promoter oxide that is deposited in a concentration gradient. A solution of the promoter oxide precursor, e.g., cerous nitrate solution, is impreganted uniformly into the pore structure of a support which can be in the form of beads or extrudates to a level just below the full incipient wetness. The impregnated support is then treated with a gaseous base such as ammonia, under dynamic conditions such as tumbling (to insure uniformity), which causes the precipitation of the promoter oxide in the form of a radial concentration gradient. The resulting product is then dried and calcined at sufficiently high temperature to effect complete conversion of the promoter precursor to its oxide form, e.g., CeO.sub.2.

Catalyst supports having promoter oxide gradient, resulting catalyst and

ZSM-5 crystallites are produced with very low levels of blocking tetrapropyl ammonium ions (Q). The reaction mixture contains sources of silica, soda, alumina and trace amounts of Q ions as nucleation agents. Because the crystallites as synthesized from the aqueous medium exhibit only a very small fraction of blocking cations, there is always a diffusion path for the hydrated sodium ions to be exchanged without the need of prior removal of the blocking cations by calcination or otherwise. The small size crystallites can be exchanged, blended with other materials, and formed into catalyst particles. The silica to alumina ratio can be varied and when no aluminum is added, silicalite may be formed. The systhesis can be done in 24 hours or less.

Process for making crystalline siliceous materials

Spheroidal alumina particles have a combination of high macroporosity, surface area, crush strength and low attrition loss and bulk density. The particles are prepared by an improved external gelation oil-drop process. In the process a slurry of alumina, preferably a microcrystalline boehmite-pseudoboehmite intermediate, is prepared in an acidic aqueous medium and droplets of the slurry are passed through air into a column containing an upper body of water-immiscible liquid and ammonia and a lower body of aqueous coagulating agent. Catalysts employing the particles as a support and having catalytic agents distributed at controlled depths in the particle have excellent initial and sustained activity and durability, especially for eliminating pollutants in automotive exhaust streams.

Spheroidal alumina particles and catalysts employing the particles as a

An alumina composition comprising a microcrystalline boehmite-pseudoboehmite intermediate having from about 70 to about 85 weight percent of the total amount of Al.sub.2 O.sub.3 present in crystalline form. The composition is prepared by adding aluminum sulfate and sodium aluminate solutions to a mixture of water and aluminum sulfate solution to precipitate alumina and adjusting the pH to a pH higher than the precipitation pH. The reactant concentrations, and rates of addition, temperatures, and pH's in the precipitation are specifically controlled to form the boehmite-pseudoboehmite intermediate.

Alumina compositions

A thermally stable, pure transition alumina extrudate suitable for use as a catalyst support has a uniquely defined bimodal pore size distribution and very good mechanical properties. Most of the surface area is in a micropore region having pores of less than 500 Angstrom units, a pore volume of 0.60 to 0.80 cm..sup.3 /g., a narrowly defined effective pore volume distribution within this region and a median pore diameter which can be controlled within the range of 90-210 Angstrom units. The macropore region made of pores having diameters of 1,000- 10,000 Angstrom units has a pore volume of at least 0.10 cm..sup.3 /g. These two pore volumes are essentially connected directly to each other. The extrudates can be strengthened by acidic additives and given increased thermal stability by adding rare earth oxides.

Extruded alumina catalyst support having controlled distribution of pore

This invention is directed to an improvement in the Hill phosphoric acid process, whereby the Hill process can be used with high-iron phosphate rock. The improvement involves oxidation of divalent iron in an early stage of the Hill process, followed by addition of a soluble potassium compound to the acid in the crystallizer.

Oxidation of phosphoric acid plus K compound addition

Improvement in the Hill phosphoric acid process. Fe.sup.++ in high iron feed is oxidized to Fe.sup.+++ to improve post-precipitation characteristics, optionally, a minor stream from the crystallizer is returned to the oxidation zone.

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Severna Park, MD, United States of America

Moises G Sanchez