Showing papers on "Silicic acid published in 1991"

Well cement compositions having improved properties and methods

Abstract: Cement compositions which have improved properties such as increased stability, reduced settling tendencies, enhanced fluid loss properties and the like and methods of using such cement compositions are provided. The cement compositions are comprised of water, hydraulic cement and an aqueous colloidal silicic acid suspension wherein the colloidal silicic acid particles have a specific surface area in the range of from about 50 m 2 /g to about 1000 m 2 /g.

Preparation of amorphous silica-alumina particles by acid-treating spherical P-type zeolite particles crystallized from a sodium aluminosilicate gel

Abstract: The invention is a process for preparing amorphous silica alumina spherical particles by mixing sodium silicate or silicic acid gel with sodium aluminate and sodium hydroxide in an aqueous solution to form a gel, homogenizing the formed gel, crystallizing this intermediate product at 85° C. to 200° under atmospheric pressure or under hydrothermal conditions to form spherical zeolite particles with an x-ray diffraction pattern inherent to P-type zeolites and with a notched surface, treating the zeolite particles with acid to remove the sodium, thereby rendering the particles amorphous.

The molecular basis of aging of aqueous silica gel

Abstract: The influence of aging on the local structure of aqueous silica gels has been investigated using small angle X-ray scattering (SAXS), solid state nuclear magnetic resonance (NMR), and nitrogen sorption techniques (BET). From SAXS experiments it is deduced that aging of aqueous silica aggregates is a process of migration of active, dissolved silicate species (e.g., monomeric silicic acid) from the more soluble and less dense places within silica aggregates (i.e., the peripheral primary particles) to the less soluble and denser parts within the aggregates (i.e., the core of the aggregates). This process results not only in an increase in size of the scattering primary particles but also in an increase in the gradient of mass density, as such corresponding to a decrease in fractal dimensionality of the silica aggregates from D = 2.25 to D = 2.0. The rate at which aging processes occur is strongly effected by the pH value of the solution. Addition of fluorine anions to the polymerizing silicate solutions causes an increase in rate of restructuring as well. Nitrogen sorption measurements on freeze-dried samples of the gels show that a porous silica structure is only obtained in case the silica gel network has been reinforced through reorganization of the fragile aggregates. The aged silica gel consists of an ensemble of densified aggregates formed by primary particles with sizes in the nanometer range.

Use of an aqueous swollen macromolecule-containing system as water for fire fighting

Abstract: In the fighting of fires or protection of objects from fire by applying thereto water, the improvement which comprises dispersing in the water particles of a cross-linked water-insoluble but hightly water-swellable acrylic acid derivative polymer in an amount insufficient to bring the viscosity above 100 mPa's. Advantageously, the particles are present in an amount such that after swelling the swollen particles hold 60 to 70% by weight of the total water, the particles are from 0.1 to 3 mm in diameter and are present in from 0.1 to 0.6% by weight of the water, the polymer being a copolymer of an acrylic acid, the water containing silicic acid and/or a silicate as well as sodium, potassium or ammonium ions. The water is freely pumpable but the swollen particles adhere to surfaces they contact rather than running off rapidly.

Equilibrium and structural studies of silicon(iv) and aluminium(iii) in aqueous solution. xxviii, formation of soluble silicic acid-ligand complexes a s studied by potnetiometric and solubility measurements

Abstract: Amorphous silica solubilities in the presence of organic (mannitol, oxalate, citrate, catechol) and inorganic (SO 4 2− ) ligands have been studied in 0.6 M Na(Cl) medium at 25 o C. Apart from the catechol system, the experiments were performed at neutral pH with an equivalent ligand concentration of ≤0.6 M. In the presence of mannitol, the solubility of SiO 2 (am) was found to decrease with increasing ligand concentration. With oxalate, citrate and sulphate, an increased solubility was observed

Herstellung und 29Si‐NMR‐Untersuchung von Polymeren mit definierten Kieselsäurebaueinheiten

Abstract: Durch Additionsreaktion der kafigartigen Doppelvierring-(D4R-)kieselsaurederivate [(CH3)2Hsi]Si8O20 mit dem zweifach ungesattigten Divinyltetramethyldisiloxan bzw. den mehrfachfunktionellen Tetramethylcyclotetrasiloxan und Polymethylhydrogensiloxan in molaren Verhaltnis der funktionellen Gruppen von 1:1 wurden 3 in organischen Losungsmitteln unlosliche Polymere hergestellt. 29Si-Festkorper-NMR-Untersuichungen zeigen, das sich die Polymere aus D4R-Kieselsaureeinheiten aufbauen, die uber ketten- oder ringformige Siloxanbruckcn miteinander vernetzt sind. Mit zunehmender Zabl funktioneller Gruppen in den Reaktionspartnern der D4R-Derivate wachst die raumliche Behinderung der Vernetzungsreaktionen. Die Polymere weisen nur eine kleine Oberflache zwischen 1 und 8 m2/g auf. Preparation and 29Si NMR Spectroscopic Investigation of Polymers with Definite Silicic Acid Units Three polymers were synthesized by additive reaction of the cage-like double fourring (D4R) silicic acid derivatives [(CH3)2HSi]8Si8O20 and [CH2CH(CH3)2Si]8Si8O20 resp., with the unsaturated diviyltetramethyldisiloxane or the multiple functional tetramethylcyclotetrasiloxane and polymethylhydrogensiloxane in a molar ratio of functional groups 1:1. By means of 29Si solid state NMR spectroscopy was shown that the in organic solvents insoluble polymers are built up by D4R silicic acid units, which are connected by chain-like or cyclic siloxane bridges. With increasing functional groups of the reactants the sterical hindrance of the reaction of D4R derivates grows. The polymers show small surfaces of 1 to 8 m2/g.

Tectoaluminosilicate cement and a process for its manufacture

Abstract: A tectoaluminosilicate cement which consists of K, Ca and aluminosilicates plus, optionally, Li, Na and Mg, contains: a phyllosilicate dehydroxylated at a temperature between 500° and 900° C., reactive amorphous silica, reactive calcium silicate glass or reactive calcium aluminosilicate glass with a Ca:Si ratio of ≧1 and alkali silicate with the total formula: a(M 2 O) * x(SiO 2 ) * y(H 2 O) in which M=Li, Na or K, a=0-4, x=0-5 and y=3-20, the overall Si:Al ratio being ≧1. The tectoaluminosilicate cement preferably alkali hydroxide. The dehydroxylated phyllosilicate is a metakaolin giving tectosilicate structures. The reactive amorphous silica is a dealuminated phyllosilicate, a fly ash dealuminated with mineral acids, where applicable, a fine-grained crystalline form of SiO 2 contained in calcinated clays, a silicic acid gel, thermally activated by alkali-activated aluminosilicate, obtained by sintering an aluminosilicate with alkali carbonate at a temperture between 800° and 1,200° C., the alkali and aluminosilicate components being mixed in the ratio 1:6 to 1:1, and/or microsilica ("silica fume"). The alkali metal activator may be prepared in situ from the dealuminated phyllosilicate and/or from the silicic acid gel in the presence of the alkali hydroxide. A bonding matrix obtained from the tectoaluminosilicate cement by reacting with water in the ratio 3:1 to 6:1 consists essentially of the formula: (Li, Na) 0-7 K 1-6 Mg 1-0 Ca 3-0 [Al 4 Si 6-14 O 21-36 ].(0-15H 2 O).

Process for producing microporous foam composed of essentially anorganic elements.

Abstract: A moulding material for producing a microporous foam product essentially composed of anorganic elements contains, besides components known in the art, a stone-forming solid, a hardening agent, a foaming additive, as well as surface-active amphiphilic additives for improving pore structure and solidity. As stone-forming component, a reactive solid from the group formed by (I) finely powdered, at least partially amorphous aluminium silicate containing amorphous silicium dioxide and aluminium oxide; (II) vitreous, amorphous electrofilter ashes; (III) ground calcinated bauxite; (IV) electrofilter ashes from brown coal fired power station; (V) undissolved, amorphous SiO2, in particular from amorphous, disperse-powdery, dehydrated or aqueous silicic acid or from high temperature processes (silica fume); (VI) metakaolin, is used. The hardening agent is in particular a solution of alkaline silicate having 1.2-2.5 moles of SiO2 per mole of K2O and/or Na2O.

Flow analysis method for the determination of silicic acid in highly purified water by gel-phase absorptiometry with molybdate and Malachite Green

Abstract: A flow analysis method based on the on-line concentration and direct absorptiometric measurement of the ion-associate species formed between molybdosilicate and Malachite Green on Sephadex LH-20 gel, is described for the determination of silicic acid in highly purified water. The increase in the attenuance of the coloured species, which was concentrated on-line onto the gel packed in a flow-through cell, could be measured continuously with a spectrophotometer at 627 nm. The coloured species on the gel was easily desorbed with a mixture of sulphuric acid and acetone, and the gel-packed flow-through cell could be used repeatedly. The concentrations of silicic acid in 4–5 samples of highly purified water were determined in less than 1 h. The detection limit was 0.1 µg dm–3 of Si using water samples with a volume of about 5 cm3. The total amount of silicate-silicon in highly purified water was determined after treating the samples with ammonia solution.

Molecular mechanics study of 18-azacrown-6 and its binding interactions in 1 : 1 host–guest complexes with neutral and anionic species

Abstract: The stereochemical preferences of 18-azacrown-6 have been studied by molecular mechanics and semiempirical quantum mechanics. Eight possible conformations were considered. Molecular mechanics results showed that several of these conformations had similarly low energies but that the order of preferences were dependent upon the charge dipole used for the C—N and N—H bonds. Calculations were also carried out for the [H3(18-azacrown-6)]3+ cation in the presence of silicic and boric acids and carbonate ion. All three guests could be attached to the host via the formation of intermolecular hydrogen bonds. The energy of the combined species was considerably less than that of the sum of the individual species in all three cases. For boric acid and the carbonate anion the difference was ca.– 13.0 kcal mol–1, but for silicic acid where three strong hydrogen bonds could be formed the difference was – 26.4 kcal mol–1.

Production of heat insulating material

Abstract: PURPOSE: To readily and efficiently produce a heat insulating material of any shape in ultra-fine silica-based heat insulating material by using synthetic hydrous silicic acid of ultra-fine particles and molding the synthetic hydrous silicic acid by press molding using a mold. CONSTITUTION: Synthetic hydrous silicic acid of ultra-fine particles is produced by a wet method of reacting sodium silicate with sulfuric acid. The synthetic hydrous silicic acid of ultra-fine particles is blended with an infrared light screening material of ultra-fine particles and reinforcing heat-resistant inorganic fibers, the prepared mixture is packed into a mold and press molded. The synthetic hydrous silicic acid of ultra-fine particles requires to have ≤100g/L bulk density and ≥100m 2 /g specific surface area. By this method, a high-performance heat insulating material having approximately the same heat insulating performance as that of a heat insulating material comprising aerogel can be produced more readily than a conventional method without restriction of molding shape. COPYRIGHT: (C)1993,JPO&Japio

Process for obtaining and manufacturing lubricant greases from fumed silica and precipitated silicic acid

Abstract: A process to manufacture in laboratory and/or industrial scale lubricant greases using hydrophilic or hydrophobic silicon bioxide (fumed silica with a surface area in the range of 120 to 300 m 2 /g), or ground precipitated silicic acid which is mixed and dispersed in an adequate and proportional manner with liquid or solid additives and with either pure paraffinic or naphthenic, heavy or light, refined or regenerated, mineral oils derived from petroleum to obtain mineral lubricant greases, or with treated vegetable oils, such as castor oil and soy oil, or synthetic esters like polyol esters and diesters or glycerine or propylene glycol, in order to obtain synthetic type lubricant greases, or with dimethyl and phenylmethyl polysiloxanes in order to obtain silicon greases. The lubricant greases of this invention may be applied with great advantages in the automotive and food industries, as well as industry in general, due to their special characteristics and properties of lubrication, purity and resistance to high or low temperatures, to water and to some solvents.

Studies on the syntheses of polymetalloxanes and their properties as a precursor for amorphous oxide. V. Preparation and properties of polytitanosiloxanes from silicic acid and bis(2,4‐pentanedionato)titanium diisopropoxide

Abstract: The polytitanosiloxanes (PTS) obtained are soluble in methanol, ethanol, and the molecular weight (M n ) is 1500-4200 depending on the reaction molar ratio (SA/PTP). Dry spinning of the solution provided golden yellow precursor fibers which can be subjected to thermal-treatment to give ceramic fibers. The PTS is considered to be a copolymer formed by the condensation of oligomeric silicic acid with PTP consisting of Si-O-Ti and Si-O-Si linkages in the molecular main chain with the ligand and hydroxy groups as pendants

Production of silica glass

Abstract: PURPOSE:To obtain a silica glass having improved bonding strength and plasticity by adding an organic binder to a slurry of spherical silica produced by the reaction of a silicic acid ester in a specific reaction solution, forming the mixture and subjecting the formed product to drying, degreasing and heating. CONSTITUTION:A slurry of spherical silica having particle diameter of 0.03-5mum is produced by mixing and reacting (A) a silicic acid ester (e.g. tetramethroxysilane) with (B) a reaction solution having a concentration of 0.001-5mol/l and containing 1.0-7.5mol/l of a base (e.g. ammonia), 1.0-30mol/l of water and an organic solvent (e.g. methanol). The slurry is concentrated to 1-95wt.% concentration and the viscosity of the slurry is adjusted to 15-500 poise by the addition of a organic binder (e.g. methylcellulose). The slurry is formed, dried by heating at 50-200 deg.C, degreased by heating at 400-800 deg.C and finally heated at 1150-1600 deg.C to obtain a transparent glass.

Liquid detergent compositions containing fluorescent whitening agents, polyvinyl pyrrolidone polymer or copolymer and silicic acid

Abstract: There are described novel storage-stable liquid detergent compositions which comprise 0.001% to 0.2% of at least one water-insoluble or sparingly soluble fluorescent whitening agent, 0.001% to 0.2% of at least one polymer and/or copolymer, and 0.2% to 5% of at least one highly disperse silicic acid, and to the preparation thereof with the aid of an aqueous dispersion which contains the fluorescent whitening agent and the polymer components, and to the use thereof. When using these liquid detergent compositions for cleaning fabric, no bleach spots are formed.

The hydrolysis of [OSi(OCH3)2]4 — a new precursor for the sol-gel process

Abstract: The hydrolysis of octamethoxycyclotetrasiloxane was carried out in the absence of a catalyst and 29Si-NMR spectra were measured. It is shown that under these conditions the siloxane ring stays intact. Due to the many possible isomers in partially hydrolysed cyclic tetramer silicic acid esters, assignment of the 29Si chemical shifts in the NMR spectra to individual species was not possible in most cases. However, the general shift area for the building units of rings > Si(OCH3)2, > Si(OCH3)(OH) and > Si(OH)2 was obtained by observing the proton coupled Si spectra. The rate constants for the formation of the ring units > Si(OH)(OCH3) and > Si(OH)2 were determined.

Electrophotographic transfer paper

Abstract: PURPOSE:To enhance white paper glossiness and image glossiness by producing the above paper by a cast coating method using a coating liquid for coating prepd. by compounding a specific ratio of synthetic silica with the pigments incorporated in a coating material. CONSTITUTION:The transfer paper provided with recording layers having at least >=1 layers of layer constitution on a base is constituted by coating the extreme surface layer of the recording layer with the coating liquid prepd. by incorporating the synthetic silica having 20 to 600m /g specific surface area at 30 to 100 pts.wt. into 100 pts.wt. pigment and compounding 10 to 50 pts.wt. binder with 100 pts.wt. pigment by using the cast coating method, by which the coating material is applied on the surface layer at 5 to 50g/m' dry solid content per one surface. The white paper glossiness of 75 deg. specular surface of the coated surface is specified to >=50%. The synthetic silica refers generally to amorphous silica, unshaped silica, silicic acid anhydride, hydrous silicic acid, fine powder silica or silicic acids which are known as white carbon, etc., consist of the network structure of Si-O and has no specified crystal structures.

Process and plant for removing gas in water containing oxygen

Abstract: The mole ratio of silicic acid to metallic ion in this flocculant is 0.3-0.5:1 at a pH value of 5-2.5 and the weight percentages are as follows: SiO2 (5-5.5), Al2O3 (1.2-2.0), Fe (<0.5), Ca (6.5-8.5), Mg (0.5-1.0), Mn (<0.5) and C (18.5-10.5). The flocculant whose main components is blast-furnace water slag, along with small quantity of aluminium, alumina, iron and zinc, is obtained by step dissolution with chlorhydric acid at ordinary temp. and pressure, filtration of insoluble matter after polymerization, curing for 3-5 hours and regulation of pH value to about 2. It has advantages of long retention period up to 20-30 days, water purifying effect better than that of aluminium sulfate, low cost and simple operation.

Rare earth metal silicate salt fluorescent substance and preparation thereof

Abstract: PURPOSE:To prepare the subject fluorescent substance reduced in the lowering of brightness and highly useful for CRT, fluorescent lights, etc., by subjecting a gel or sol to a hydrothermal reaction to allow a crystal to grow for forming a polyhedron having a clear crystal habit. CONSTITUTION:A homogeneous solution containing rare earth ions for forming the center of emission, other rare earth element ions for forming matrix salts and a silicic acid alkoxide is prepared, and a solvent is removed before or after a gel product is prepared from the solution or after a co-precipitated sol is formed. The prepared gel or sol is subjected to a hydrothermal reaction to form the nuclei of crystals, and evaporative decomposed components are removed to pulverize. The prepared powder is reacted with water in a closed container under high temperature and pressure to allow crystals to grow. The crystals are dehydrated and heated in the atmosphere or in a reducing atmosphere to stabilize the surfaces of the crystals for providing the objective fluorescent substance.

Producing mouldings for catalytic use from pyrogenic silicic acid - by hydrothermally treating initially moulded body with ammonia contg. solution

Abstract: Mouldings based on pyrrogenic silicic acid are produced by hydrothermally treating an initially moulded body with an ammonium solution or a solution of a compound which liberates ammonia. The initial body is produced by mixing particles of the pyrogenic silicic acid in aqueous phase with either a silica sol or an aqueous or aqueous/alcoholic ammonium solution to form a paste which is moulded, dried and calculated. USE/ADVANTAGE - Producing catalyst supports or catalysts. The particles of pyrogenic silicic acid are held together with using a binding agent thereby producing high mechanical stability. The final product has a high specific porous volume and high specific surfacesp

Process for preparing hydrogen fluoride

Abstract: A process for preparing hydrogen fluoride, which comprises (i) reacting calcium fluoride with sulfuric acid to produce a gypsum and a gas containing hydrogen fluoride, (ii) separating hydrogen fluoride from said gas containing hydrogen fluoride, (iii) absorbing said hydrogen fluoride-separated gas with water to obtain an aqueous solution containing hydrogen fluoride and silicofluoric acid, (iv) reacting calcium carbonate with said aqueous solution to obtain a suspension containing silicic acid and calcium fluoride, (v) adding an alkaline substance to said suspension to make pH at least 8, thereby stabilizing the silicic acid as a colloidal solution, (vi) separating a calcium fluoride solid and the colloidal solution of silicic acid from said suspension, and (vii) recycling the separated calcium fluoride as a starting calcium fluoride.

Method for producing flocculant for water treatment

Abstract: A flocculant for water treatment containing a highly polymerized silicic acid solution having a high concentration of SiO 2 and an extremely low concentration of alkali metal substance, and a method for producing such flocculant. The silicic acid solution is prepared by treating an aqueous solution of an alkali metal silicate such as water glass to remove alkali metal and allowing the solution to liquefy after once gelling. The flocculant may further contain a water soluble metal salt such as ferric chloride or ferric nitrate.

Adsorbent for malodorous gas

Abstract: PURPOSE: To obtain an adsorbent having excellent adsorptivity for various kinds of malodorous gas such as hydrogen sulfide, ammonia, mercaptan, amine, etc., by controlling the pH of an aq. soln. containing silicate and metal salt, keeping the soln. at specified temp. to produce a sol containing silicate and metal salt, and neutralizing the sol with an acid to make silicic acid gel structure. CONSTITUTION: pH of an aq. soln. containing silicate and metal salt is controlled to 9-11 and this soln. is kept at 45-70°C to produce a sol containing silicate and metal salt. This sol is neutralized with an acid to afford an adsorbent for malodorous gas having ≥500m 2 /g specific surface area and containing metal salt in its silicic acid gel structure. This adsorbent has excellent adsorptivity for various kinds of malodorous gas such as hydrogen sulfide, ammonia, mercaptan, amine, aldehyde, etc. This adsorbent consists of a nontoxic silicate compd. and the metal salt is contained in the silicic acid gel and does not dissolve to the outside of the gel. Therefore, the adsorbent is safe, and further, it is thermally stable up to about 500°C and can be kneaded into plastics. COPYRIGHT: (C)1992,JPO&Japio

Method for shortening ageing time of silica flocculant

Abstract: PURPOSE:To shorten the ageing time of a silica flocculant by ageing a soln. contg. a polyvalent metal ion such as Al ion, an alkaline-earth metal ion such as Ca ion and silicic acid and then diluting the soln. with water to restrain its gelling. CONSTITUTION:A powdered ore contg. Si, Al and Ca is dissolved in hydrochloric acid, sulfuric acid or their mixture to prepare a soln. contg. a polyvalent metal ion such as aluminum ion, an alkaline-earth metal ion such as calcium ion and silicic acid. The soln. is aged and then diluted with water to restrain its gelling, and the ageing time of the silica flocculant is shortened. A mineral powder obtained by melting blast-furnace slag powder and an ore contg. Si, Al and Ca to change its mineral crystal structure is appropriately used as the powdered ore.

Method and apparatus for analyzing silicic acid ion

Abstract: PURPOSE:To analyze the silicic acid ions in water with high sensitivity by separating the silicic acid ions from other ions by using a sepn. column, then determining the ions. CONSTITUTION:The color forming reagent supplied from a color developing reagent supplying line 13 into a color developing reagent tank 29 is preheated to a reaction temp. by a color development reactor 16 while the color developing agent is deaerated by a deaerator 18 and is applied with the pressure loss by a pressurizing coil 17. The reagent is then introduced by a pump 12 to a mixing point 11. The reagent is mixed with an electrolytic eluant from the sepn. column 8 at a mixing point 11 and the mixture is introduced to a vessel 16. The mixture is further cooled near to the temp. of an absorption photometer 15 by a cooling coil 22 and is then introduced to the photometer 15. The analysis of a so-called blank state is executed by the photometer 15 with the liquid mixture in which the silicic acid ions are not included. The liquid mixture is discharged to the outside of the system via a drain line 26 while a back pressure is applied thereon by a back pressure coil 23 after the analysis.

Verfahren zur herstellung von saeurefesten katalysatoren fuer die direkte hydrierung von carbonsaeuren zu alkoholen

Abstract: Acid-resistant copper chromite catalyst material containing foreign metal compounds as well as colloidal silicic acid, and a process for their production and use for direct fixed-bed hydration of fatty acids to produce fatty alcohols of appropriate chain-length.