摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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 (MT) together with bulky cations of Groups 2 and 1 of the Periodic Table (M2+ and M1+) such as Ba2+ and K1+. Their hexagonal crystal structure comprises parallel chains of highly covalent, octahedrally coordinated oxygen around the transition metal, which exhibits its highest valence +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 M2+(1−x)M1+xMTO3−&dgr;.
摘要翻译:本申请描述了陶瓷氧化物超导体,其前体和制备方法。 超导体不含铜,但是包含过渡金属镍或钴(M)以及周期表第2族和第1族的大体积阳离子(M 2+和M 1+),例如Ba 2+和K 1 +。 它们的六方晶体结构包括在过渡金属周围高度共价,八面体配位的氧的平行链,其价态呈现出最高的价格。 八面体是刻面连接形成的多酸链或大分子,其沿着c轴运行全长的微晶或单晶。 链条间隔开距离,防止它们之间的共价或轨道重叠。 它们通过库仑力从位于它们之间的阳离子保持在一起,它们也平行于c轴延伸。 通过孔承载的电流只能在链内流动。 因此,这些材料是组成为M 2+(1-x)M 1 x M O 3-δ的一维超导体。
摘要:
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.
摘要翻译:一种氧化铝组合物,其包含以结晶形式存在的Al 2 O 3总量的约70至约85重量%的微晶勃姆石 - 假勃姆石中间体。 通过将硫酸铝和铝酸钠溶液加入到水和硫酸铝溶液的混合物中以沉淀氧化铝并将pH调节至高于沉淀pH的pH来制备组合物。 特异性地控制反应物浓度以及沉淀速率,温度和pH值以形成勃姆石 - 假勃姆石中间体。
摘要:
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.