Abstract: A catalyst with a high sulphur tolerance for the hydrogenation of middle distillate aromatics which comprises as a support (a) an alumina, the surface of which has been modified by contacting it with a silicon-containing compound, or (b) a silica, the surface of which has been modified by contacting it with an aluminum-containing compound. The support has been treated with air, oxygen or water vapor at an elevated temperature in order to convert the said silicon-containing compound or the said aluminum-containing compound to oxide form. The hydrogenating component of the catalyst is one or more metals of the platinum group.

Abstract: Modified particles obtained by a process comprising contacting water-containing particles(a), an organometallic compound(b) and a compound(c) having a functional group containing active hydrogen or a non-proton donative Lewis basic functional group, and having an electron attractive group; a carrier of said particles; a catalyst component for olefin polymerization of said particles; a catalyst for olefin polymerization comprising said particles(A) and a transition metal compound(B), and optionally, an organometallic compound (C); and a method for producing an olefin polymer with said catalyst for olefin polymerization.

Abstract: Aluminum-magnesium silicate- or fluorinated magnesium silicate- aerogels which may be calcined, chemically modified, ion-exchanged, agglomerated, used as a component of a catalyst composition for an addition polymerization; supported versions thereof; and processes for polymerization are disclosed.

Abstract: The present invention relates to a hydrotreating catalyst composed of a carrier having a Brønsted acid content of at least 50 &mgr;mol/g such as a silica-alumina carrier or a silica-alumina-third component carrier, in which the silica is dispersed to high degree and a Brønsted acid content is at least 50 &mgr;mol/g, and at least one active component (A) selected from the elements of Group 8 of the Periodic Table and at least one active component (B) selected from the elements of Group 6 of the Periodic Table, supported on said carrier. The present invention also relates to a method for hydrotreating hydrocarbon oils using the same. The hydrotreating catalyst of the present invention provides excellent tolerance to the inhibiting effect of hydrogen sulfide, high desulfurization activity, and exhibits notable effects for deep desulfurization of hydrocarbon oils containing high contents of sulfur, in particular gas oil fractions containing difficult-to-remove sulfur compounds.

Abstract: The invention relates to a method for producing an adsorbent and/or catalyst and binder system comprising I) mixing components comprising (a) a binder comprising a colloidal metal oxide or colloidal metalloid oxide, (b) an oxide adsorbent and/or catalyst particle, and (c) an acid, (ii) removing a sufficient amount of water from the mixture to cross-link components a and b to form an adsorbent and/or catalyst and binder system. The invention also relates to particles made by the process, binders, and methods for remediating contaminants in a stream.

Abstract: The present invention provides a method for the homogenous and highly efficient synthesis of an aluminosilicate material that can be used for adsorbents, deodorants, catalyst carriers, humidity adjustors, and the like, and relates to a method for manufacturing spherical hollow silicate clusters, comprising steps of mixing a solution of a silicon compound and a solution of an aluminum compound or transition metal compound, each with a solution concentration of 10-1000 mmol, rapidly or simultaneously at a rate of 1-10,000 mL/min, removing a salt formed as a by-product, and then subjecting the mixture to hydrothermal synthesis to yield the silicate clusters.

Abstract: Oxidation catalyst compositions include a catalytic material having a BET surface area of at least about 10 m2/g and consisting essentially of a combination of bulk ceria and a bulk second metal oxide which may be one or more of titania, zirconia, ceria-zirconia, silica, alumina-silica and &agr;-alumina. The combination may optionally also include activated alumina having a BET surface area of at least about 10 m2/g. The ceria, second metal oxide and optional activated alumina may be mixed together or provided as discrete layers. Optionally, one of platinum or palladium metal may be dispersed on the catalytic material provided that the platinum, when used, is used in limited amounts to preclude excessive oxidation of SO2 to SO3. The catalyst compositions may be used for oxidation of oxidizeable components in a gas-borne stream, e.g., in a method to treat diesel engine exhaust by contacting the hot exhaust with the catalyst composition to promote the oxidation of the volatile organic fraction.

Abstract: An electron accepting developer useful for producing visible images by reaction with an electron donor in carbonless paper and photo-imaging systems, the developer comprising an acid-treated, water insoluble alkali metal-modified, inorganic oxide or an acid-treated molecular sieve.

Abstract: A process is disclosed for producing hydrocarbons by contacting a feed stream comprising hydrogen and carbon monoxide with a catalyst in a reaction zone maintained at conversion-promoting conditions effective to produce an effluent stream comprising hydrocarbons. The process is characterized by using a catalyst prepared by a method involving (1) forming a catalyst gel by destabilizing an aqueous colloid comprising (a) at least one catalytic metal for Fischer-Tropsch reactions (e.g., iron, cobalt, nickel and/or ruthenium), (b) colloidal cerium oxide, zirconium oxide, titanium oxide and/or aluminum oxide, and optionally (c) Al(OR)3, Si(OR)4, Ti(OR)4 and/or Zr(OR)4 where each R is an alkyl group having from 1 to 6 carbon atoms; and (2) drying the gel.

Abstract: A process for making a calcined, oxide material by at least partially delaminating a swollen, layered oxide material prior to calcination, and the product thereof having an increased active surface area that corresponds to an adsorption capacity for 1,3,5-trimethylbenzene of at least 0.50 mmol/g at a temperature of 42° C. and a pressure of 173.3 Pa. The calcined, oxide material retains a porous shape although non-pillared.

Abstract: The invention provides a process for commercial production of syndiotactic polyolefins using a metallocene catalyst supported on silica treated with MAO. The invention includes contacting the supported metallocene catalyst with an aluminum alkyl and aging the catalyst prior to polymerization. In addition, the catalyst is prepolymerized in a tubular reactor prior to being introduced into the polymerization reaction zone. The treated silica is produced by removing water to a level of 0.5-1.08%, slurrying in a nonpolar solvent, adding an alumoxane, heating to reflux, cooling the slurry, and separating the solid product.

Abstract: The invention relates to a method of producing a catalyst comprising a porous support and a catalytically active metal deposited thereon comprising the steps of treating the porous support with a solution of a salt of the catalytically active metal and a reducing agent to achieve electroless deposition of the catalytically active metal on the support. The invention also relates to a catalyst obtainable by the method and a process of producing hydrogen peroxide.

Abstract: A catalyst for the production of alkenylaromatics from alkylaromatics, wherein the catalyst is predominantly iron oxide, an alkali metal compound and less than about 100 ppm of a source for a noble metal, such as palladium, platinum, ruthenium, rhenium, osmium, rhodium or iridium. Additional components of the catalyst may include compounds based on cerium, molybdenum, tungsten and other such promoters. Also a process for the production of alkenylaromatics from alkylaromatics using this catalyst.

Abstract: Synthetic clay minerals are made up of elementary three-layer platelets consisting of a central layer of octahedrally oxygen-surrounded metal ions (octahedron layer), which layer is surrounded by two tetrahedrally surrounded, silicon atom-containing layers (tetrahedron layers), a number of such elementary platelets being optionally stacked. The dimensions of the clay platelets vary from 0.01 &mgr;m to 1 &mgr;m, the number of the stacked elementary three-layer platelets varies from on average one platelet to twenty platelets, while in the octahedron layer at most 30 at. % of the metal ions has been replaced by ions of a lower valency and in the tetrahedron layers at most 15 at. % of the silicon ions has been replaced by ions of a lower valency, such a replacement having taken place in at least one of these layers and these layers having a deficiency of positive charge because of the replacement.

Abstract: A honeycomb structure in which partitioning walls comprising, as a chief component, cordierite of a chemical composition containing 45 to 55% by weight of SiO.sub.2, 33 to 42% by weight of Al.sub.2 O.sub.3, and 12 to 18% by weight of MgO are formed in the shape of a honeycomb. The partitioning walls have a thickness of not larger than 250 .mu.m and a porosity of from 45 to 80%.

Abstract: A mixed metal oxide catalytic system consisting of molybdenum, vanadium, palladium, lanthanum, niobium and X, wherein X is copper and/or chromium, providing higher yields of acrylic acid and acrolein in the low temperature oxidation of propylene with a molecular oxygen-containing gas without the production of side products such as CO.

Abstract: The present invention relates to amorphous microporous mixed oxides, characterized by having, in dried form, a narrow pore size distribution (half width <.+-.10% of the pore diameter) of micropores with diameters in the range of <3 nm and a total surface area of between 20 and 1000 m.sup.2 /g, containing a fraction of from 0.1 to 20% by weight of non-hydrolyzable organic groups, and to a process for the preparation of such oxides.

Abstract: A composition of matter is provided including an inorganic porous material having wall portions defining mesopore-sized channels having a mean diameter of between about 15 .ANG. and about 100 .ANG. and a narrow diameter distribution of less than or equal to about 30 .ANG., the material having a void volume from the mesopore-sized channels of at least about 0.1 cc/g and a surface area of at least about 500 m.sup.2 /g and having a number of hydroxyl groups of at least about 1.5 mmol of hydroxyl groups per gram of material, and exhibiting thermal and hydrothermal stability at temperatures up to about 500.degree. C. Catalytic materials incorporating aluminum and other active metals, as well as a process for preparing the composition, are also disclosed.

Abstract: A process for the preparation of a catalyst comprising sequential deposition of cobalt or a cobalt compound, and scandium or a scandium compound, on an inert carrier oxide, which catalyst can be used in the conversion of synthesis gas according to the Fischer-Tropsch process.

Abstract: A synthetic, crystalline, porous material is disclosed, together with the related preparation process. Such material of zeolitic nature containing oxides of silicon, titanium and gallium corresponds, in the calcined and anhydrous state, to the following empyrical formula:pHGaO.sub.2 .multidot.qTiO.sub.2 .multidot.SiO.sub.2,wherein p has a value greater than zero and smaller than or equal to 0.050, and q has a value greater than zero and smaller than or equal to 0.025, and the H.sup.+ of HGaO.sub.2 can be at least partially replaceable or replaced by cations.

Abstract: A mixed metal oxide MoVLaPdNbXO catalytic system (wherein X=Al, Ga, Ge and/or Si) providing higher selectivity and space time yield of acetic acid at low pressure and low temperature in a single stage oxidation of ethane with a molecular oxygen-containing gas and steam.

Abstract: A catalyst system comprising a nitrided silicoaluminophosphate, and a method of preparing such catalyst system which comprises nitriding a silicoaluminophosphate, are disclosed. The thus-obtained catalyst system is employed as a catalyst in the conversion of a hydrocarbon feedstock comprising oxygenated hydrocarbons to olefins.

Abstract: A catalyst system comprising a silylated silicoaluminophosphate composition, and methods of preparing such catalyst system, are disclosed. The thus-obtained catalyst system is employed as a catalyst in the conversion of a hydrocarbon feedstock comprising oxygenated hydrocarbons to olefins.

Abstract: A method of making a unique, promoted support for improved catalysts for conversion of exhaust from internal combustion engines, said support comprising a mixed-metal-oxide promoter containing at least Ce and Zr substantially uniformly dispersed as homogeneous crystallites of less than about 100 .ANG. on a high-surface-area refractory oxide support substrate, comprising dissolving a combination of Ce- and Zr-oxide precursors, and optionally another metal oxide precursor, and a compatible organic depositing agent, slowly heating to transform the depositing agent into a gel-like matrix coating the substrate in which the mixed-metal-oxide precursor compounds are uniformly distributed and thereafter calcining to burn off the organic matrix and form the appropriate oxide morphology.

Abstract: A composition comprises silicon, aluminum, zirconium, and boron. A process for producing the composition comprises contacting a silicon compound, an aluminum compound, a zirconium compound, and a boron compound under a condition sufficient to effect the production of a composition comprising silicon, aluminum, zirconium, and boron. Also disclosed is a process for catalytically cracking a hydrocarbon-containing fluid which comprises contacting said hydrocarbon-containing fluid with a catalyst composition which comprises silicon, aluminum, zirconium, and boron.

Abstract: A FCC catalyst having improved coke selectivity and a FCC process for converting hydrocarbon feedstocks to lower boiling products. The catalyst comprises a crystalline aluminosilicate zeolite, gibbsite, rare earth metal compound and a silica matrix prepared from at least one of a silica sol made by an ion-exchange process and an acidic silica sol prepared by mixing sodium silicate, an acid and an aluminum salt of an acid.

Abstract: An oxidation catalyst based on titanium silicalites or vanadium silicalites having a zeolite structure and containing from 0.01 to 30% by weight of one or more noble metals selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, rhenium, gold and silver has been molded by a compacting shaping process.This oxidation catalyst is used for the preparation of epoxides, in particular propylene oxide, from olefins, hydrogen and oxygen.

Abstract: A metal foil has improved resistance to permanent thermal expansion. This metal foil includes a metal foil substrate and a thin barrier layer on at least one surface of the metal foil substrate. The metal foil can be used in a catalyst assembly to provide a catalyst support having improved resistance to permanent thermal expansion. The catalyst assembly includes a metal foil substrate and a thin barrier layer on at least one surface of the metal foil substrate. A catalyst material is provided on at least a portion of the barrier layer. This invention further relates to a method for reducing permanent thermal expansion of a metal foil. This method includes applying a barrier layer coating to at least one surface of a metal foil substrate. The method further can include the step of applying a catalyst material to at least a portion of the barrier layer.

Abstract: Methods of making substantially phase-pure and thermally stable crystalline alumina compositions stabilized with an oxide of silicon, germanium, phosphorus, arsenic or a mixture thereof. Also provided are crystalline alumina compositions and catalyst supports made using these methods.

Abstract: A FCC catalyst having improved coke selectivity and greater catalyst strength, and a FCC process for converting hydrocarbon feedstocks to lower boiling products. The catalyst comprises a crystalline aluminosilicate zeolite, gibbsite, and a silica matrix prepared from at least one of a silica sol made by an ion-exchange process and an acidic silica sol prepared by mixing sodium silicate, an acid and an aluminum salt of an acid.

Abstract: Disclosed is a process for the preparation of pyridine bases by a reaction of an aliphatic aldehyde and/or ketone with ammonia under gaseous phase using a specified catalyst in which a specified metal or combined metals are carried in or onto specified zeolites, for example, such as zeolites having a specified specific density range.

Abstract: A method of preparing an alumina-based bodies suitable for use as an adsorbent or catalyst, the method comprising providing a source of activated alumina powder for forming into bodies and providing an aqueous solution containing at least two different alkali metals, at least one alkali metal derived from a soluble carboxylic acid alkali metal salt. As said powder is formed into said bodies, the bodies are contacted or sprayed with the aqueous solution to provide composite bodies containing the alumina powder and the alkali metals and the soluble carboxylic acid alkali metal salt. Alternatively, the alumina bodies may be formed first and then contacted, e.g., soaked in the aqueous solution. Or, a viscous slurry of the activated alumina powder and the aqueous solution may be made. The viscous slurry may be made into bodies by extrusion or by the oil drop method. Thereafter, the bodies are thermally treated to activate alumina therein and remove or decompose the organic part, e.g.

Abstract: A catalyst useful in purifying exhaust gases is disclosed which includes: (a) a carrier including a composite of SiO.sub.2, .gamma.-alumina and an alkali earth metal oxide selected from the group consisting of MgO and BaO; (b) an oxygen absorbing material; and (c) at least one noble metal.

Abstract: A transition metal containing catalyst having a silica-support is provided for the production of polyolefins from .alpha.-olefins that can be converted to polymer films, preferably thin films of polyolefin, which have lower defects resulting from a decreased presence of silica-containing residues from the catalyst. The catalyst has a porous silica support component and a catalytic component which may include, but is not limited to, such materials as chromium, magnesium-titanium (Ziegler-Natta type) or metallocene compounds (Metallocene catalyst type). The porous silica component of the catalyst has an average pore volume of from about 2.5 to about 3.5 ml/g and a surface area of 200 to 400 m.sup.2 /g and preferably 250 to 350 m.sup.2 /g. The average pore diameter ranges from about 285 to about 700 Angstroms and preferably 500-700 Angstroms for porous silica components having surface areas of 200 m.sup.2 /g and preferably 285-400 Angstroms for porous silica components having surface areas of 350 m.sup.2 /g.

Abstract: A novel aqueous solution for the one step impregnation of catalytic supports, catalysts prepared from such solution, and the preparation and the use of catalysts prepared thereby. The catalysts prepared are used in the hydrotreatment of petroleum fractions and particularly in hydrodesulfurization and/or denitrogenization. The solution is a combination of at least one compound of a metal from group IVa (e.g. Zr), at least one compound of a metal from group VIa (e.g. Mo or W), at least one compound of a metal from group VIII (e.g. Co or Ni), and at least one water soluble amine (e.g. ethylenediamine or MEA).

Abstract: The invention concerns a catalyst for conversion of hydrocarbon feeds. The catalyst is essentially constituted by 0.05% to 10% by weight of a precious metal and a silica (5-70%)/alumina support with a specific surface area of 100-500m.sup.2 /g. The catalyst has an average pore diameter of 1-12 nm, the pore volume of pores with diameters between the average diameter.+-.3 nm being more than 40% of the total pore volume. The dispersion of the precious metal is 20-100% and the distribution coefficient for the precious metal is greater than 0.1.The invention also concerns a process for the hydroisomerization of feeds with boiling points of more than 350.degree. C. using this catalyst. The process is operated between 200.degree. C. and 450.degree. C. at 2-25 MPa with a VVH of 0.1-10 h.sup.-1 and a hydrogen/feed volume ratio of 100-2000.

Abstract: The present invention provides a catalyst for reduction of nitrogen oxides represented by the formula (A.sub.a O.sub.x.B.sub.b O.sub.y).(C.sub.c O.sub.z.C'.sub.c' O.sub.z')/S which is produced by supporting mixed metal oxides represented by the formula (A.sub.z O.sub.x.B.sub.b O.sub.y).(C.sub.c O.sub.z.C'.sub.c' O.sub.z') in amorphous state on aluminum or silicon-containing support at calcination temperature of 400.degree. to 700.degree. C. in a molar ratio of 0.01:1 to 5:1, anda method for removing nitrogen oxides through selective catalytic reduction which comprises converting 50 to 50,000 ppm of nitrogen oxides in exhaust gas from automobile or from fixed source such as plant turbine and boiler, and other industry in a state of having 0.1 to 20% of excessive oxygen over (A.sub.a O.sub.x.B.sub.b O.sub.y).(C.sub.c O.sub.z.C'.sub.c' O.sub.z')/S catalyst by using 100 to 100,000 ppm of hydrocarbon reducing agent having 1 to 5 carbons under the reaction condition of 200.degree. to 800.degree. C.

Abstract: Compacts produced from a pyrogenically produced oxide, magnesium stearate, methyl cellulose and urea are mixed together in the presence of water, compacted, dried, comminuted to a powder, and the powder is pressed with an isostatic press to compacts and the compacts tempered. The resulting compacts have an outside diameter of 16 to 100 mm.

Abstract: Aerogels or xerogels containing atomically dispersed noble metals for applications such environmental remediation. New noble metal precursors, such as Pt--Si or Pd(Si--P).sub.2, have been created to bridge the incompatibility between noble metals and oxygen, followed by their incorporation into the aerogel or xerogel through sol-gel chemistry and processing. Applications include oxidation of hydrocarbons and reduction of nitrogen oxide species, complete oxidation of volatile organic carbon species, oxidative membranes for photocatalysis and partial oxidation for synthetic applications.

Abstract: Micro-mesoporous gel consisting of a silica matrix possibly wherein one or more metal oxides selected from transition metals or metals belonging to groups IIIA, IVA and VA are uniformly dispersed, characterized by a monomodal porosity distribution.

Abstract: The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilation, olefin oxidation, isomerization, hydrocyanation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical.

Abstract: A lightweight aggregate and a process and apparatus by which FCC, petroleum equilibrium fluid-cracking catalyst, a by-product of the oil refinery industry, can be added to the feedstock materials fed into the feed end of a rotary lightweight aggregate kiln or blown into the discharge end of the same kiln by insufflation, or by a combination of both techniques, to form the lightweight aggregate utilizing the FCC as received without further processing.

Abstract: A process for manufacturing a silica porous material with high solid acidity, catalytic activity and adsorption ability as well as excellent crystallinity and heat resistance has the steps of adding a compound of metallic element such as Al to a waterglass, aging the resultant mixture, calcining the aged mixture to form a layered crystal, incorporating an organic substance between layers of the layered crystal, calcining the resultant layered crystal for crosslinking the layered crystal. By this process, a plurality of layers formed of SiO.sub.4 tetrahedral and metallic oxide constitute a silica porous material, and the gap between adjacent layers of the layered crystal is reduced at a crosslinking site, while the gap of the other portion is expanded to form a micro pore.

Abstract: The present invention is directed to a process for the carbonylation of an arylene to an arylaldehyde (e.g., toluene to tolualdehyde) in the presence of a solid acid catalyst. The process for making tolualdehyde comprises carbonylating toluene in the presence of either carbon monoxide or a source of carbon monoxide and in contact with a solid acid catalyst. The reaction is carried out at a temperature ranging from -40.degree. to 200.degree. C., and at a pressure ranging from 20-4000 psig.

Abstract: A method of making a catalyst, catalyst support or adsorbing structure which involves forming a mixture of raw material which can be ceramic and/or molecular sieve, silicone resin permanent binder, dibasic ester as a solvent for the silicone resin, organic binder of cellulose ether, and/or derivatives thereof, and water, shaping the mixture into a green body which is then dried and heated to develop strength and form the catalyst, catalyst support, or adsorber.

Abstract: In order to provide a temperature- and acid-resistant catalyst carrier based on a gas-pervious carrier body and a porous surface layer having a high silica content, while dispensing with a washcoat, the carrier body and the surface layer are designed as a chemically and physically homogeneous structure shaped in a single operation. The SiO.sub.2 content amounts to at least 99% by weight and has a specific surface from 5 m.sup.2 /g to 50 m.sup.2 /g. In a process for producing a catalyst carrier made of synthetic, amorphous silica particles with more than 99% by weight SiO.sub.2, a paste is prepared with the particles, a liquid, and a binder. Plastifying agents are added to the paste and the paste is continuously extruded into a monolithic greenware strand. The alkali and alkaline earth content of the paste is set at no more than 200 ppm and the greenware is cut to length and sintered at a temperature in a range between 800.degree. C. and 1400.degree. C.

Abstract: A supported Lewis acid catalyst system for catalyzing hydrocarbon conversion reactions including cationic polymerization, alkylation, isomerization and cracking reactions is disclosed, wherein the catalyst system comprises an inorganic oxide support having immobilized thereon a least one strong Lewis acid comprising at least one metal salt of a strong Bronsted acid wherein the metal is selected from the group consisting of aluminum, boron gallium, antimony, tantalum, niobium, yttrium, cobalt, nickel, iron, tin, zinc, magnesium barium strontium, calcium, tungsten, molybdenum and the metals of the lanthanide series and wherein the strong Bronsted acid is selected from the group consisting of mineral and organic acids stronger than 100% sulfuric acid.

Abstract: An engine exhaust gas purifying catalyst contains, as active substances, platinum and at least one of iridium, III-B metals and IV-B metals. In particular, the catalyst contains mainly platinum and iridium and, desirably, rhodium as an additive catalyst substance.

Abstract: A process for shape selective hydrocarbon conversion involves contacting a hydrocarbon feedstream under conversion conditions with a catalytic molecular sieve which has been modified by treatment with an amino silane polymer while molecular sieve acid sites are protected. When the process is toluene disproportionation, a toluene feedstream may also contain a second silicon source which is a high p-xylene selectivating agent. The invention also includes the modification method and the shape selective catalyst which results from the modification.

Abstract: A stable aqueous sol of amorphous alumina containing Al.sub.2 O.sub.3 up to 15% by weight and 0.1 to 0.5 gram equivalent of an anion of acid to 1 mol of aluminum in the sol, in which the colloidal particles of amorphous alumina have a controlled thickness in a range of 20 to 100 millimicrons and a uniform length in a range of 200 to 500 millimicrons is produced by a process comprising feeding an aqueous solution of an acid into an aqueous slurry containing 1 to 7% by weight of metallic aluminum, 10 to 200 ppm by weight as SiO.sub.2 of a water-soluble silicate and 0 to 20 ppm by weight of a water-soluble sulfate as SO.sub.4 to the water in the slurry while maintaining the slurry at a temperature of 80.degree. C. to boiling point under normal pressure, said acid being in an amount of 0.1 to 0.5 gram equivalent to 1 mol of the metallic aluminum in said slurry, at a rate of 0.001 to 0.