Alumina particles
First Claim
1. Friable particles having an alumina content of at least about 98.5 weight percent, a surface area of less than about 1 m2 /g, an attrition resistance of less than about 0.3 weight % per hour when tested in an air jet apparatus, a particle size ranging from about 30 to about 110 microns, a tap density of about 1.3 to about 1.9 g/cc, a generally spherical shape, and sufficient porosity to hold catalytic quantities of catalytic metals.
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Accused Products
Abstract
Essentially spherical particles are disclosed of at least 98.5% alumina having a surface area less than about 1 m2 /g, an attrition resistance of less than about 0.3 weight percent/hour in an air jet attrition test, a particle size of about 30 to about 110 microns, a tap density of about 1.3 to about 1.9 g/cc, and sufficient porosity to hold catalytic metals in conventional catalytic amounts. The alumina particles are especially suited for use as fluid bed catalyst carriers for use in environments involving the presence of steam, particularly at high temperatures.
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Citations
26 Claims
- 1. Friable particles having an alumina content of at least about 98.5 weight percent, a surface area of less than about 1 m2 /g, an attrition resistance of less than about 0.3 weight % per hour when tested in an air jet apparatus, a particle size ranging from about 30 to about 110 microns, a tap density of about 1.3 to about 1.9 g/cc, a generally spherical shape, and sufficient porosity to hold catalytic quantities of catalytic metals.
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11. A process for preparing friable particles having an alumina content of at least about 98.5 weight percent, a surface area of less than about 1 m2 /g, an attrition resistance of less than about 0.3 weight percent per hour when tested in an air jet apparatus, a particle size ranging from about 30 to about 110 microns, a tap density of about 1.3 to about 1.9 g/cc, a generally spherical shape, and sufficient porosity to hold catalytic quantities of catalytic metals, said process comprising the steps of (i) forming an aqueous slurry having about 15 to about 50 weight percent solids wherein the solids comprise about 85 to about 99 weight percent -325 U.S. mesh of a high fired alumina having an ultimate crystallite size of greater than about 25 microns, and about 1 to about 15 weight percent of a material selected from the group consisting of (a) a super ground alpha alumina having a particle size less than about 5 microns, (b) a clay, and (c) a mixture of (a) and (b);
- (ii) spray drying the slurry to produce substantially spherical particles having an average particle size of about 30 to about 110 micron;
(iii) heat treating the spray dried particles at a temperature below their melting points to form agglomerates of alumina particles having a surface area below about 1 m2 /g and an attrition resistance of less than about 0.3 weight %/hour in an air jet apparatus; and
(iv) deagglomerating the agglomerates to produce the particles. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
- (ii) spray drying the slurry to produce substantially spherical particles having an average particle size of about 30 to about 110 micron;
- 21. A process for producing friable particles having an alumina content of at least about 99.5 weight percent, a surface area of less than about 1 m2 /g, an attrition resistance of less than about 0.3 weight percent per hour when tested in an air jet apparatus, a particle size ranging from about 30 to about 110 microns, a tap density of about 1.3 to about 1.9 g/cc, a generally spherical shape, and sufficient porosity to hold catalytic quantities of catalytic metals, said process comprising (i) heating hydrated alumina particles having a particle size of about 35 to about 150 microns to remove at least about 90 weight percent of the bound water and to convert the hydrate to at least gamma alumina and (ii) entraining the particles in a carrier gas and passing them through a high temperature zone of a plasma spray at a temperature sufficient to at least partially melt the particles and to cause them to have the properties.
Specification