Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
  • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
  • B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
  • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
  • B01D53/9454—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific device
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
  • B01J23/42—Platinum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
  • B01J23/75—Cobalt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/85—Chromium, molybdenum or tungsten
  • B01J23/88—Molybdenum
  • B01J23/882—Molybdenum and cobalt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0215—Coating
  • B01J37/0221—Coating of particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/03—Precipitation; Co-precipitation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
  • B01J27/04—Sulfides
  • B01J27/043—Sulfides with iron group metals or platinum group metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
  • B01J27/04—Sulfides
  • B01J27/047—Sulfides with chromium, molybdenum, tungsten or polonium
  • B01J27/051—Molybdenum
  • B01J27/0515—Molybdenum with iron group metals or platinum group metals
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies

Definitions

• catalytically active substances such as oxides and sulphides of Fe, Co, Mo, Ni, W etc, which are highly insoluble, and also metals, such as Pt, Pd etc.
• these catalytically active substances are deposited on a catalyst support in order to obtain a physical shape suited for the catalytic process and to economize on the catalytic substances which are generally very expensive.
• Swedish patent specifications SE-B-345,393 and SE-B-408,375 disclose a method for obtaining a large surface area of a catalytically active material on the surface of carrier particles, the catalytically active material being precipitated on carrier particles which may be in the form of a suspension of synthetic or natural minerals.
• carrier particles which may be in the form of a suspension of synthetic or natural minerals.
• suspended carrier materials mention is made of "AEROSIL” which is a highly porous spray-dried silica and which when used is suspended in a suitable liquid.
• the precipitation of the catalytically active substance on the surface of the carrier particles will be in the form of fine particles having a diameter of 10-50 ⁇ .
• a relatively thick coating of the catalytically active material is therefore obtained on the carrier particles which themselves consist of aggregate particles.
• this known method suffers from a number of drawbacks, e.g. limitations as regards the obtainable degree of dispersion for the catalytically active substance and a relatively large consumption of catalytically active material.
• One object of the present invention is to achieve extremely fine particles with a surface coating of a metal or a sparingly soluble metal compound, in particular a catalytically active substance.
• Another object of the invention is to achieve a novel method of producing fine catalytically active particles.
• Yet another object of the invention is to achieve particles coated with a metal or a metal compound and having, in relation to the mass of the particles, a low content of metal or metal compound material located in the very surface of the particles.
• a further object of the invention is to achieve a method of depositing and/or precipitating thin coatings of insoluble or sparingly soluble substances on surfaces of fine particles.
• a further object of the invention is to produce a catalyst mass having such a low content of catalytically active material that the losses of catalytic material are minimal when disposing of spent catalyst mass.
• the present invention is based on the idea of depositing from a solution, preferably but not necessarily an aqueous solution, a metal, a metal compound or a precursor of the metal or metal compound on monodisperse solid sol particles in suspension, such as sols of e.g. silica or aluminium oxide.
• a solution preferably but not necessarily an aqueous solution
• a metal, a metal compound or a precursor of the metal or metal compound on monodisperse solid sol particles in suspension, such as sols of e.g. silica or aluminium oxide.
• a liquid-borne monodisperse sol of carrier particles is first prepared, having a surface area accessible to the liquid of at least 100 m 2 /g, and thereafter dissolving in this sol a soluble metal compound which is thereafter precipitated as metal or a sparingly soluble metal compound on the carrier particles.
• a monodisperse sol a maximally large particle surface will be available for receiving the precipitated substance which is not the case if suspended aggregate particles are used as carrier particles.
• the components of the sparingly soluble compound are therefore supplied in such a manner that precipitation occurs on the surface of the sol particles.
• This may be effected in that the components, under vigorous agitation of the sol, are supplied simultaneously at different pointsor supplied, successively after each other, such that one component is attracted by the particle surface prior to or in connection with the reaction with the other component or such that the newly formed compound is preferentially attracted by the sol particles without any major aggregates of the insoluble compound having time to form.
• major aggregates refers to so-called oligomeric or more polymeric aggregates.
• the addition of the components must be effected under conditions promoting colloidal stability. Thus, the electrolyte content in the solution should not attain a level which destabilizes, coagulates, the sol particles, i.e.
• a soluble compound of one component (anionic or cationic) of the sparingly soluble metal compound is dissolved in a very low concentration in a liquid-borne sol of carrier particles, the other component of the sparingly soluble metal compound being supplied at a supply rate which allows preferential adsorption or attraction of the precipitating sparingly soluble compound on the sol particles instead of an excess of the limit of solubility of the compound in the liquid phase of the sol and, hence, formation of crystal nuclei of the sparingly soluble metal compound therein.
• a surface coating of metal on sol particles may also be achieved in that the metal is first precipitated on the sol particles as a reducible sparingly soluble metal compound which is thereafter reduced to metal.
• a soluble compound of the desired metal can be dissolved in the sol in order that this should adsorb or attract the metal-containing ion or molecule of the compound, whereupon these ions or molecules are directly reduced to metal.
• a soluble compound of the desired metal or metal compound i.e. a precursor of the desired final catalytically active substance
• the soluble compound being supplied in such an amount that substantially all metal ions or molecules in the solution can be adsorbed against or be attracted by the surface of the sol particles by surface chemical forces, such as surface charge, van der Waals' forces, dispersion forces etc.
• a very slow addition is thereafter effected of a substance which precipitates the desired catalytically active substance or a precursor thereof directly on the surface of the sol particles by reacting with the ions or molecules attracted or adsorbed against it.
• the production of the coated sol particles may be effected in several stages, i.e. if the particles initially lack a surface chemical nature suitable for the deposition with respect to the final catalytically active substance or any other desired substance, it is possible similarly to build up several layers to change the surface charge of the initial sol particles from negative to positive and vice versa.
• the same technique can be used if it is desirable to deposit a mixture of catalytically active substances on the particles, e.g. a mixture of cobalt oxide and molybdenum oxide or a mixture of cobalt sulphide and molybdenum sulphide.
• the sol particles will thus serve as carriers for the catalytically active substance or substances.
• the carrier particles are monodisperse and have a large available surface area, such that the carrier surface per unit volume of the sol is large, and 2) that the precipitation of the desired substance (or precursor thereof) occur so slowly that the resulting substance will have time to diffuse up to the carrier surface and be deposited thereon without excess of the limit of solubility of the substance in the liquid phase of the sol and without any spontaneous formation of crystal nuclei therein.
• the simplest way of carrying out this aspect of the invention is using water as the liquid medium in which the coating of the surface of the sol particles is brought about.
• other liquid media are usable provided the contemplated substances are soluble in the liquid media and can be precipitated therefrom with the technique here described.
• the substances used for coating or depositing must be such substances as precipitate as highly sparingly soluble compounds and do not easily crystallize. if the compounds are liable to crystallization, they should not undergo so-called Ostwald ripening, since such ripening implies a growth of crystal grains at the expense of the formation of new crystal nuclei on adjoining surface portions of the carrier particles. It is believed that the most suitable substances for coating or depositing are those which are least apt to spontaneously form nuclei when supersaturated solutions of the substances are formed. Usually, this is the case with compounds which are highly insoluble and which crystallize very slowly, e.g. barium sulphate, cobalt sulphide etc.
• SiO 2 e.g. from Si(OH) 4 Aluminium oxide, e.g. Al(OH) 3 ⁇ 3H 2 O Aluminium silicates ZrO 2 , e.g. from ZrOCl 2 Al(PO) 4 , e.g. from A1 3+ and PO 4 3-
• Silicates and carbonates of polyvalent metals e.g. Silicates and carbonates of polyvalent metals.
• Metals e.g. precious metals, such as Pd and Pt.
• the carrier in the form of a sol must have a very low solubility in the liquid phase used, generally and preferably water, or at least have a very low dissolution rate in the liquid phase.
• the particles of the sol should be monodisperse and have a very large surface area, calculated on the accessible surface, for although particles which are large and have a spongy structure have a large internal surface, this surface is not always accessible to the solution from which the coating is precipitated or deposited.
• the required size of the accessible surface is determined by a number of factors of which the surface chemical effect of the surface is one of the most important.
• the surface accessible to the solution must be at least 100 m 2 /g in order to obtain practical production rates. A practical range of surface areas is 100-1000 m 2 /g.
• sols having a surface area of 300-700 m 2 /g, corresponding to a particle size of about 4-9 nm, can be used to advantage.
• silicic acid sols (which have a negative surface charge) may first be modified with a polyaluminium compound, e.g. from basic aluminium chloride, in order to have a positive surface charge, if necessary for depositing or precipitating the desired catalytically active substance or its precursor.
• the polarity may also be affected by the pH of the liquid medium. In the case of e.g. a silicic acid sol, the surface of the sol is about neutral at a pH of 2-3 and the negative charge increases with increasing pH.
• the pH is an aid for adjusting the surface charge.
• Another means for increasing the negative charge of a silicic acid particle is to react aluminium with the surface of the silicic acid particles with formation of negative SiAl 4 -1 sites.
• Such a modified silicic acid contains a considerable negative charge also at acid pH, as opposed to unmodified silicic acid sols.
• the carrier particles have or are first imparted the ability to adsorb or attract one or more of the components of the desired coating (e.g. by ensuring that the surface of the carrier particles has a suitable surface charge), so as to make it possible by a slow controlled precipitation rate to direct the precipitation to the surface of the sol particles.
• the carrier i.e. the sol particles
• the carrier i.e. the sol particles
• the conditions for the deposition must be such that the sol particles (or modified particles) of the carrier material have a sufficiently large total surface for a surface chemical adsorption or attraction of substantially all ions or molecules which are present in the solution and should be included in the subsequently precipitated or deposited substance.
• the other ion(s) or molecule(s) to be combined with the ions or molecules adsorbed or attracted to the sol particles must thereafter be supplied at such a low rate that the chemical compound or compounds to be precipitated or deposited will have time to diffuse up to the surface of the particles and be deposited thereon without the limit of solubility being exceeded and without any spontaneous formation of crystal nuclei in the solution.
• the rate at which a coating can be built up on the sol particles without the formation of new free crystal nuclei in the solution depends on the crystallinity of the coating and varies over a very wide range depending on what substances are combined to form the coating.
• the invention is also usable in connection with catalysts of the type where the surface of sol particles comprises a catalytically active metal, such as Pt or Pd.
• a catalytically active metal such as Pt or Pd.
• One method of producing such catalytically active surfaces is to reduce a metal compound together with the sol, such that the metal is directly precipitated on the surface of the sol particles.
• Another way is to first precipitate an insoluble compound of the metal on the surface of the sol and thereafter convert this compound to a catalytically active form of the metal.
• the liquid-borne sol of surface-coated particles can be used for different purposes, e.g. for producing an adsorbent or a catalyst by spray drying.
• a catalyst it is highly advantageous to coat the surface of a catalyst support with said surface-coated solid sol particles. This gives an advantageous increase of the activity of the resulting catalyst mass in that the accessible surface area of catalytically active substance will thus be increased 2-3 times as compared with the case where the surface coating of active material is deposited directly on the surface of the catalyst support instead of the surface of the sol particles.
• EXAMPLE 1 Comparative example without sol
• pH is adjusted to 9.7.
• 150 g of an aqueous solution containing 0.256 g CoCl 2 ⁇ 6H 2 O, and 160 g of an aqueous solution containing 0.272 g Na 2 S.9H 2 O are added dropwise and simultaneously to the beaker at a rate corresponding to 10 g solution every 27 minutes.
• the temperature of the solutions is maintained at 25°C.
• a black precipitate of CoS is immediately formed upon the addition of the first drops of the sulphide and chloride solutions.
• silicic acid sol containing 4.85% SiO 2 and having a surface area of 392 m 2 /g (corresponding to a particle size of about 7 nm) and a pH of 9.7 are added 160 g of an aqueous solution containing 0.2 g CoCl 2 ⁇ 6H 2 O, and 160 g of an aqueous solution containing 0.272 g Na 2 S ⁇ 9H 2 O dropwise and simultaneously under vigorous agitation at a rate which corresponds to 10 g solution every 27 minutes.
• the solutions are maintained at a temperature of 25°C.
• the sol solution is gradually coloured brownish black during the addition of the two solutions, but no separate precipitation of CoS occurs. When the sol solution is ultracentrifuged, black sol particles settle and a clear supernatant is formed.
• the sediment contains CoS in an amount corresponding to the added amount of sulphide and cobalt.
• silicic acid sol which contains 4.85% SiO 2 and has a surface area of 392 m 2 /g (corresponding to a particle size of about 7 nm) and a pH of 9.7 and whose surface has been modified with sodium aluminate, such that 25% of the atoms in the surface are aluminium atoms, are added 160 g of an aqueous solution containing 0.256 g CoCl 2 ⁇ 6H 2 O, and 160 g of an aqueous solution containing 0.272 g Na 2 S ⁇ 9H 2 O dropwise and simultaneously under vigorous agitation at a rate corresponding to 10 g solution every 27 minutes. The solutions are maintained at a temperature of 25°C.
• the sol solution is gradually coloured black during the addition of the solutions, but no precipitation of CoS occurs.
• black sol particles will settle and a clear supernatant be formed.
• the sediment contains CoS in an amount corresponding to the added amount of sulphide and cobalt.
• silicic acid sol which contains 3.94% SiO 2 and has a surface area of 110 m 2 /g (corresponding to a particle size of about 25 nm) and a pH of 9.7 and whose surface has been modified with sodium aluminate, such that 25% of the atoms of the surface are aluminium atoms, are added 160 g of an aqueous solution containing 0.256 g CoCl 2 ⁇ 6H 2 O, and 160 g of an aqueous solution containing 0.272 g Na 2 S ⁇ 9H 2 O dropwise and simultaneously at a rate which corresponds to 10 g solution every 27 minutes. The temperature of the solutions is maintained at 25°C.
• the sol solution is gradually coloured blackish brown during the addition of the two solutions, but no precipitation of CoS occurs.
• blackish brown sol particles will settle and a clear supernatant be formed.
• the sediment contains CoS in an amount corresponding to the added amount of sulphide and cobalt.
• Example 3 To the same sol as in Example 3 are added 40 g of an aqueous solution containing 0.256 g CoCl 2 ⁇ 6H 2 O, and
• Example 3 is repeated with the exception that 160 g of an aqueous solution containing 0.256 g NiCl 2 ⁇ 6H 2 O is added together with the sodium sulphide solution.
• the sol solution is gradually coloured black during the addition of the two solutions, but no precipitation of nickel sulphide occurs.
• the sol solution is ultracentrifuged, black sol particles settle and a clear supernatant is formed.
• the sediment contains NiS in an amount corresponding to the added amount of sulphide and nickel.
• silicic acid sol which contains 11.5% SiO 2 and has a surface area of 476 m 2 /g (corresponding to a particle size of about 6 nm) and a pH of 10 and whose surface has been modified with sodium aluminate, such that 25% of the atoms in the surface are aluminium atoms, is added dropwise and under vigorous agitation 45 g of a 0.2 molar Na 2 S ⁇ 9H 2 O solution. pH is thereafter decreased to 4.3-4.4 by the addition of a 0.5 molar HCl solution under vigorous agitation.
• 0.2 g Co(NO 3 ) 2 ⁇ 6H 2 O is dissolved in 100 g silicic acid sol in which the surface of the sol particles has been modified with sodium aluminate, such that 25% of the atoms in the surface are aluminium atoms.
• the sol contains 3.9% SiO 2 and has a surface area of 110 m 2 /g
• a solution of 0.2 g (NH 4 ) 6 Mo 7 O 24 ⁇ 4H 2 O in 100 ml water is prepared and added to the sol dropwise and under vigorous agitation at room temperature. pH is adjusted to 10.5 with ammonium hydroxide. The solution is left under agitation for 1 hour at room temperature. After centrifuging, the sample consists of a pale pink sediment and a clear colourless supernatant. The added amount of molybdenum and cobalt is quantitatively found in the sediment. If the experiment is conducted in the absence of silicic acid sol, there is obtained a bluish precipitate when pH is adjusted to 10.5 with ammonium hydroxide.
• Cobalt- and molybdenum sulphides on modified silicic acid sol Example 9 is repeated but the resulting sediment is dried. The dried sediment is thereafter treated with hydrosulphuric acid at a temperature in the range of
• a first solution is prepared by adding 2 ml hydrazine hydrate under agitation to a silicic acid sol containing 3.94% SiO 2 and having a surface area of 110 m 2 /g. 4.5 ml of an H 2 PtCl 6 solution containing 30 g Pt/1 and being acidified with HCl so as to be 5.8 molar with respect to HCl is diluted with 20.5 ml water to obtain a second solution. At a supply rate of 0.37 ml/min the second solution is added dropwise to the first solution under agitation. During the addition of the second solution to the first solution, an ammonium hydroxide solution is also added dropwise, so that pH never falls below 4.3.
• Platinum on aluminium silicate sol Example 11 is repeated but the first solution is instead a solution of 2 ml hydrazine hydrate in 25 g silicic acid sol whose surface has been modified with sodium aluminate, such that 25% of the atoms are aluminium atoms, this silicic acid sol containing 3.87% SiO 2 and having a surface area of 110 m 2 /g (corresponding to a particle size of about 22 nm). Upon centrifuging, a blackish brown sediment is formed and a clear colourless supernatant. The supplied amount of platinum is quantitatively found in the sediment.
• EXAMPLE 13 Molybdenum sulphide on surface-modified silicic acid sol In a beaker is introduced 50 g silicic acid sol which contains 4.5 g sol particles and 45.5 g water and in which the surface of the silicic acid particles has been modified with sodium aluminate, such that 25% of the atoms in the surface are aluminium atoms.
• the sol has a surface area of 110 m 2 /g and contains 3.87% SiO 2 and 0.07% Al 2 O 3 .
• the sol solution is gradually coloured blackish grey during the addition of the ammonium molybdate solution, but no separate precipitation of molybdenum sulphide occurs. Upon ultracentrifuging, a blackish grey sediment settles on the bottom, in which the added molybdenum and sulphide can be quantitatively found. If this experiment is repeated in the absence of aluminium-modified silicic acid sol, a blackish grey precipitate of molybdenum sulphide is obtained in the reaction vessel.

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• 1984
  • 1984-01-30 SE SE8400426A patent/SE8400426L/xx not_active Application Discontinuation
• 1985
  • 1985-01-29 JP JP60500638A patent/JPS61501134A/ja active Pending
  • 1985-01-29 BR BR8504995A patent/BR8504995A/pt unknown
  • 1985-01-29 ES ES539929A patent/ES8608057A1/es not_active Expired
  • 1985-01-29 WO PCT/SE1985/000036 patent/WO1985003239A1/en not_active Ceased
  • 1985-01-29 JP JP60500594A patent/JPS61501133A/ja active Pending
  • 1985-01-29 FI FI853777A patent/FI853777A7/fi not_active Application Discontinuation
  • 1985-01-29 EP EP85900813A patent/EP0169876A1/en not_active Withdrawn
  • 1985-09-26 DK DK435485A patent/DK435485D0/da not_active Application Discontinuation
  • 1985-09-27 NO NO853818A patent/NO853818L/no unknown

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