Abstract: A process for disintegrating material containing alkali-alkali earth silie for yielding alkali silicate or alkali carbonate solutions and materials having a large specific surface is characterized in that a material containing silicate is crushed and subsequently is treated in an autoclave at a temperature in excess of 100.degree. C, preferably in excess of 130.degree. C, with a solution containing alkali carbonate.

Abstract: A process for recovering mineral values from fly ash in commercial quantities comprising forming an alkaline aqueous fly ash blend, filtering the alkaline aqueous fly ash blend and recovering a solids blend therefrom, leaching the solids blend with hydrochloric or hydrofluoric acid to form dissolved chloride or fluoride salts of iron, aluminum and other metals, electrolyzing the dissolved chloride or fluoride salt solution to plate out at least iron, and, optionally, one or more other metals, recovering silicon dioxide as a precipitate from the leaching solution, and recovering the leaching solution free of silicon dioxide. Neutralizing the leaching solution in a certain pH range permits precipitation and recovery of aluminum hydroxide as a solid. The hydroxide may then be converted to alum or alumina by conventional methods.

Abstract: A multistage precipitation and flocculation production process is disclosed in which primary silica particles are prepared and flocculated useing an alkali metal salt solution and further silica precipitated in the presence of the salt, the pH of the mixture reduced and the silica isolated, purified carefully dried and optionally milled.

Abstract: A novel method of controlling electrodialytically produced silica sol particle size and concentration comprising effecting electrodialysis of an alkali metal silicate anolyte in an electrodialysis cell with a cation permselective membrane separating the anolyte and the catholyte while adding alkali metal silicate solution to the anolyte to maintain the desired pH whereby a silica sol with increasing particle size is formed and when the silica sol has reached the desired particle size, continuing electrodialysis with addition of an alkali metal hydroxide solution to control the pH until the silica sol has the desired concentration.

Abstract: A method for producing precipitated silicic acid products and silicates having a unique combination of physical and chemical properties is disclosed. The products are produced by acidulating a solution of an akali metal silicate with an acid until precipitation just begins. At this point the reaction mass is aged for a period of time and thereafter the acid addition is continued until the precipitated product is obtained. Products produced in accordance with the invention exhibit lower wet cake moisture (or higher percent solids) and are characterized by their low structure, low oil absorption, high abrasiveness and high pack density. The products can be used as abrasive and polishing agents in dentifrice compositions, in the production of molecular sieves, in paints and the like. In a particularly advantageous embodiment, an adduct material, such as aluminum, is added to control the refractive index of the precipitated silica.

Abstract: Amorphous silicon dioxide particles for polishing semiconductor surfaces are prepared by boiling, at reflux, a mixture of surplus organic amine, a hydroxybenzene, water and silicon in the presence of oxygen to precipitate silicon dioxide.

Abstract: Porous silica particles useful in catalysis are prepared by adding excess alkali to a body of water glass; the excess alkali is responsible for increasing the pore diameter.

Abstract: A process for the production of spherical silica gel which comprises emulsifying water glass in a dispersion medium composed of a polar solvent and a non-polar solvent and gelling the water glass while maintaining it in emulsified state.

Abstract: A method for producing precipitated silicic acid pigments and silicates having a unique combination of physical and chemical properties is disclosed. The pigments are produced by acidulating alkali metal silicate solutions which contain a salt or electrolyte, such as sodium sulfate, which serves to pre-polymerize the said silicate solution. Pigments produced in accordance with the invention exhibit lower wet cake moisture (or higher percent solids) and are characterized by their low structure, low oil absorption, high abrasiveness and high pack density. The products can be used as abrasive and polishing agents in dentifrice compositions, in the production of molecular sieves, in paints and the like. In a particularly advantageous embodiment, an adduct material, such as aluminum, is added to control the refractive index of the precipitated pigment.

Abstract: Large crystals of a silica polymorph having a characteristic X-ray diffraction pattern, a specific gravity of 1.70 .+-. 0.05 g/cc. and a mean refractive index of 1.39 .+-. 0.01 after calcination in air at 600.degree. C., are prepared by a hydrothermal process in which fluoride anions are included in the reaction mixture. The crystals, which can be as large as 200 microns, exhibit a substantial absence of infrared adsorption in the hydroxyl-stretching region and also exhibit an exceptional degree of hydrophobicity.

Abstract: A process of leaching silicated zinc ores with sulfuric acid in which the ore is reacted at elevated temperature with at least a stoichiometric amount of sulfuric acid, treating products of the reaction with a predetermined quantity of hot water, filtering the zinc sulfate solution from precipitated silica, washing with a further predetermined quantity of hot water (the total amount of hot water used being determined so as to obtain the desired concentration of zinc in solution). The zinc is later recovered electrolytically. A 1 to 6N sulfuric acid solution may be used in which case a gelatinous mass is formed upon reaction and then it is evaporated at 100.degree. C of at least 60% of its water content. Alternatively the ore can be malaxated with about 20% stoichiometric excess concentrated sulfuric acid, and filtered at out at elevated temperature.

Abstract: Potassium fluoride and silica are reacted with an aqueous solution of hydrofluorosilicic acid. The resulting potassium fluorosilicate is recovered. The potassium fluorosilicate may be further reacted with ammonia in water to form an aqueous mixture of ammonium fluoride and potassium fluoride. The ammonium fluoride is then heated in aqueous solution in the presence of excess potassium fluoride to release ammonia and to form potassium bifluoride. The potassium bifluoride is recovered from solution substantially free from ammonia and heated to release hydrogen fluoride. Alternatively, the recovered potassium bifluoride may be reacted with sodium fluoride to produce sodium bifluoride. The sodium bifluoride is then heated to release hydrogen fluoride.

Abstract: A method for producing precipitated silica products having a unique combination of physical and chemical properties is disclosed. The products are produced by acidulating a solution of an alkali metal silicate with an acid under carefully controlled precipitation conditions. In accordance with the method, at least a portion of the alkali metal silicate solution theoretically required to react with said acid is initially charged to the reaction vessel. Thereafter, the remaining silicate solution and the acid are simultaneously added to the reaction vessel in a manner to control the alkalinity of the reaction medium. By controlling the percent of the silicate solution initially charged to the reaction vessel, silicas having predetermined properties can be obtained. Properties of the products include low wet cake moisture content, low structure, low oil absorption, high abrasivness, and low void volume. The products can be used as abrasive and polishing agents in dentifrice compositions.

Abstract: Hydrogen fluoride is produced from hydrofluosilicic acid. The hydrofluosilicic acid is reacted with ammonia. An aqueous solution of ammonium fluoride thus produced is fed with partly recycled alkali metal fluoride to a continuously operated reactor where a bifluoride of the alkali metal is formed in aqueous solution. Reaction mixture is continuously withdrawn and solid alkali metal bifluoride crystallized therefrom. The mother liquor is recycled to the reactor. The solid alkali metal bifluoride is decomposed by heat to produce hydrogen fluoride and solid alkali metal fluoride. The alkali metal fluoride is recycled to the reactor.

Abstract: Anhydrous hydrogen fluoride is produced from fluorosilicic acid by its decomposition with sulphuric acid in an improved process. Fluorosilicic acid of high concentration 40-50%, free of suspended silica is decomposed while being heated up to its boiling temperature with partial conversion into gaseous state. Earlier in the process evolved gaseous fluorine compounds which are desiccated by means of sulphuric acid and then separated by hydrogen fluoride absorption in a circulating liquid consisting of sulphuric acid and fluorosulphonic acid. Later hydrogen fluoride is distilled from this liquid and liquefied.

Abstract: A novel crystalline silica composition having uniform pore dimensions of approximately 6 Angstrom units is prepared by calcining a crystalline hydrated alkylonium silicate prepared hydrothermally from a reaction mixture containing as essential reagents, water, amorphous silica and a quaternary ammonium compound at a pH of at least 10. The crystalline silica, because of its uniform pore structure, is capable of making size-selective separations of molecular species, but neither it nor its silicate precursor exhibit ion-exchange properties.This absorbent has a very useful hydrophobic/organophilic characteristic which permits its use in selectively adsorbing organic materials from water, either in liquid or vapor phase.

Abstract: An improvement in the process for the recovery of aluminum from alunite in which the alunite in particulate form is dehydrated, sulfur and alkali metal compounds removed from the dehydrated ore leaving a particulate residue containing aluminum values, the residue digested with at least one alkali metal hydroxide to convert the aluminum values to soluble aluminates, silicon removed from the soluble aluminate solution, and aluminum values precipitated from the aluminate solution, the improvement comprising: multiple stage digestion of the particulate residue accomplished by dividing the particulate residue into two fractions, digesting one fraction first and using the first stage liquor from the first digestion step to digest the remaining fraction. The fraction digested first may be the one having the smaller particle size, or the one having the larger particle size.

Abstract: In a coal gasification operation or similar process carried out in the presence of an alkali metal-containing catalyst wherein spent solids containing ash and alkali metal catalyst residues are produced, alkali metal constituents are recovered from the spent solids by first removing magnetic constituents from the solids, contacting the solid particles from which magnetic constituents have been separated with an acid solution to extract alkali metal constituents from the solids and produce a spent acid solution enriched in alkali metal salts, raising the pH of the enriched solution sufficiently to precipitate aluminum from the solution as aluminum hydroxide, heating the remaining solution to precipitate silicon compounds, and recovering an enriched alkali metal solution from which aluminum and silicon compounds have been removed.

Abstract: A process for producing sodium fluoride from sodium silicofluoride in which sodium silicofluoride is added to an ammonium fluoride solution for double decomposition reaction to obtain a slurry containing sodium fluoride as crystals and ammonium silicofluoride in dissolved form, and the solution from which the sodium fluoride crystals have been removed is added with ammonia to decompose the ammonium silicofluoride into silica and ammonium fluoride. The ammonium fluoride obtained by the decomposition is recycled to the double decomposition step. Alternatively, the ammonium fluoride is reacted with a sodium salt for recovery as sodium fluoride.

Abstract: Silica xerogels having pore volumes greater than about 2.0 cc/g., the major portion of which volumes are provided by pores having pore diameters ranging from 300 to 600 A, and surface areas ranging from 200 to 500 m.sup.2 /g. Xerogels having such cumulative pore volume, pore diameter distribution, and surface area characteristics are useful as supports for stereospecific catalysts for particle form olefin polymerization reactions effecting the production of low molecular weight, high melt index polyolefins.

Abstract: A loosely aggregated 200-500 millimicron primary particle size silica can be produced by a silicate neutralization technique. The process consists of neutralizing an alkali metal silicate solution by addition to an ammoniated acetic acid or carbonic acid mixture. These particles are loosely aggregated to an average particle size of about 1 micron. These particles are readily deaggregated in a fluid energy mill. A very convenient technique is to dry and deaggregate in a fluid energy mill in a single step.

Abstract: A method for producing precipitated silicic acid pigments and silicates having a unique combination of physical and chemical properties is disclosed. The pigments are produced by acidulating a solution of an alkali metal silicate with an acid until precipitation just begins. At this point the reaction mass is aged for a period of time and thereafter the acid addition is continued until the precipitated product is obtained. Pigments produced in accordance with the invention exhibit lower wet cake moisture (or higher percent solids).

Abstract: A method for producing precipitated silicas and silicates having a unique combination of physical and chemical properties is disclosed wherein the silicas are produced by acidulating alkali metal silicate solutions. The refractive index of the silicas is controlled within desired ranges by the addition of an adduct material, such as aluminum, during the reaction. The products can be used as abrasive and polishing agents in dentifrice compositions, in the production of molecular sieves, in paints and the like.

Abstract: A method for producing precipitated silicic acid pigments and silicates having a unique combination of physical and chemical properties is disclosed. The pigments are produced by acidulating alkali metal silicate solutions which contain a salt or electrolyte, such as sodium sulfate, which serves to pre-polymerize the said silicate solution. Pigments produced in accordance with the invention exhibit lower wet cake moisture (or higher percent solids) and are characterized by their low structure, low oil absorption, high abrasiveness and high pack density. The products can be used as abrasive and polishing agents in dentifrice compositions, in the production of molecular sieves, in paints and the like. In a particularly advantageous embodiment, an adduct material, such as aluminum, is added to control the refractive index of the precipitated pigment.

Abstract: A process for the manufacture of olefin polymers by polymerization of .alpha.-monoolefins by means of a silicic acid xerogel/chromium trioxide catalyst, which is obtained by a method wherein (1) a finely divided silicic acid xerogel is first manufactured by (1.1) employing a silicic acid hydrogel of relatively high solids content, (1.2) extracting at least 60% of the water contained in the hydrogel from the latter by means of a particular organic liquid, (1.3) drying the gel thus obtained until there is no further loss in weight (xerogel formation) and (1.4) reducing the xerogel thus obtained to particles of diameter from 20 to 2,000 .mu.m,2. this xerogel is then charged with the desired amount of chromium from a solution of chromium trioxide or a solution of a chromium compound which under the conditions of stage (3) is converted to chromium trioxide, with evaporation of the solvent, and3. finally the product thus obtained is heated in an anhydrous stream of gas containing oxygen.

Abstract: This invention relates to a method of growing a single quartz crystal stone. In particular, a method for hydrothermally growing a quartz stone from a quartz seed is disclosed. A substantially stress-free quartz stone is grown in an autoclave by clamping a quartz crystal seed plate in a clip so as to permit substantially unobstructed growth of the stone in the plane of the seed plate, and growing at least a portion of the stone through at least one aperture formed in the clip.

Abstract: Microfine silicas that are useful as rubber reinforcing fillers and thickening agents, and are readily dispersible are prepared by modifying the surface layer of the silica. The surface modification results from including in or affixing to the surface of the silica certain inorganic polyvalent ions.

Abstract: The addition of sodium phosphate to a dilute solution of alkali metal silicate, precipitates microfine silica that is readily dispersible.

Abstract: In the production of an ammonium fluoride solution by precipitating hexafluosilicic acid from its solution with ammonia and from the resulting suspension separating off the silicon dioxide precipitated, the improvement which comprises thoroughly mixing the hexafluosilicic acid solution and ammonia at a temperature of about 40.degree. to 90.degree. C, in such proportions that the suspension obtained contains at least 1% of free ammonia and at most 22% of ammonium fluoride, the average residence time of the reactants in the precipitation zone being at least 4 minutes. Advantageously, the silicon dioxide is separated off from the suspension obtained without previous cooling, the resulting ammonium fluoride filtrate is left standing for at least 30 minutes to permit flocculation of silicon dioxide contained therein and the flocculated silicon dioxide is separated off.

Abstract: A method of producing citrine crystals comprising the step of growing citrine crystals under hydrothermal conditions by the temperature difference method in a high-pressure autoclave on crystalline quartz seeding plates oriented in parallel with the pinacoid crystallographic plane {0001} or with planes inclined at an angle within the range of up to 20.degree. with respect to said pinacoid plane using a charge comprising crystalline quartz and aqueous solutions of potassium carbonate with a concentration of from 5-10 wt.%. Said solutions contain iron introduced in the autoclave in the form of metallic iron in an amount of from 2-20 g per lit. of the solution, as well as nitrites or nitrates of alkali metals or potassium permanganate which are introduced in the autoclave in an amount of from 1-20 g per lit. of the solution. The above-described method of growing citrine crystals is carried out at a crystallization temperature of from 300.degree.-345.degree. C, under a pressure of from 300-1500 kg/cm.sup.

Abstract: A process for producing amethyst crystals involving growing of colorless quartz crystals by a hydrothermal method of a temperature drop in a high-pressure autoclave on crystalline quartz seed plates oriented parallel to the crystallographic planes of the major {1011} and minor {1101} rhombohedrons using crystalline quartz as a charge. Said growing is effected from aqueous solutions of potassium carbonate or potassium hydroxide having a concentration ranging from 4 to 7 wt.% and containing iron introduced into the autoclave in the form of metallic iron or in the form of its oxydic or hydroxydic compounds in an amount ranging from 5 to 30 g/l of the solution. The growing process is effected at a crystallization temperature within the range of from 300.degree. to 500.degree. C. under a pressure ranging from 200 to 1,700 kg/cm.sup.2 and a crystal growth rate of from 0.05 to 0.5 mm/day.

Abstract: A new precipitated silica having a unique combination of physical and chemical properties is disclosed. The silicon dioxide is produced by acidulating a solution of an alkali metal silicate having a specific SiO.sub.2 /Na.sub.2 O mol ratio with an acid until precipitation just begins. At this point, the reaction mass is aged for a period of time and thereafter the acid addition is continued until the precipitated product is obtained. Products produced in this manner exhibit lower wet cake moisture and are characterized by their low structure, low oil absorption, high abrasiveness and high pack density, and as such are distinctly different from silicas used as reinforcing fillers in rubber. An adduct material, such as aluminum, is added to control the refractive index and surface area of the precipitated product. Because of the controlled refractive index and other properties, the novel silicon dioxides have particular utility for use as abrasion and gelling agents in clear toothpaste compositions.

Abstract: Porous silicic acid having a specific surface of about 50 to 1000 m.sup.2 /g and having an anion content below the chemically determinable limit of detection is made by hydrolyzing methyl or ethyl silicate or polymethyl or polyethyl silicate with about 70 to 120% of the stoichiometric amount of water with moderate stirring.Hydrolysis activators such as acids or bases may be present as well as alcoholates of oxides of transition metals which then appear in the end product. Alcohol may also be present to facilitate hydrolysis.The products are characterized by marked purity and their specific surface can be closely and reproducibly controlled.

Abstract: Superfine amorphous, high structure silicic acid is made by subjecting the components in the precipitation reaction, that is, an acid or acidic substance and an alkali-metal silicate solution to a shearing force during the alkaline phase of the precipitation reaction, the shearing force being applied by passing the reaction mass in a continuous flow through a dispersing device and the dispersing device being operated with an hourly throughput frequency of at least 10 h.sup..sup.-1, the said frequency being determined as the ratio of the performance of the dispersing device to the initial volume of the reaction mass.The high structure silicic acid is particularly useful as carrier and filler for pesticides, animal feed additives and as matting agent for lacquers.

Abstract: Superfine amorphous, high structure silicic acid is made by subjecting the components in the precipitation reaction, that is, an acid or acidic substance and an alkali-metal silicate solution to a shearing force during the alkaline phase of the precipitation reaction, the shearing force being applied by passing the reaction mass in a continuous flow through a dispersing device and the dispersing device being operated with an hourly throughput frequency of at least 10h.sup.- .sup.1, the said frequency being determined as the ratio of the performance of the dispersing device to the initial volume of the reaction mass.The high structure silicic acid is particularly useful as carrier and filler for pesticides, animal feed additives and as matting agent for lacquers.

Abstract: A new method for producing precipitated silicas having a unique combination of physical and chemical properties is disclosed. The silicas are produced by acidulating a solution of an alkali metal silicate having a specific SiO.sub.2 /Na.sub.2 O mol ratio with an acid until precipitation just begins. At this point, the reaction mass is aged for a period of time and thereafter the acid addition is continued until the precipitated product is obtained. Products produced in accordance with the invention exhibit lower wet cake moisture and are characterized by their low structure, low oil absorption, high abrasiveness and high pack density, and as such are distinctly different from silicas used as reinforcing fillers in rubber. In a particularly advantageous embodiment, an adduct material, such as aluminum, is added to control the refractive index of the precipitated pigment silica. Products produced in this manner have particular utility for use as abrasion and gelling agents in clear toothpaste compositions.

Abstract: A process for producing precipitated silicic acid pigments having new and improved properties is disclosed. The pigments are produced by the simultaneous introduction of a solution of an alkali metal silicate and an acid, such as sulfuric acid, into an aqueous receiving medium which contains a salt or electrolyte. The pH of the aqueous receiving medium is adjusted prior to the introduction of the acid and silicate so that it is the same or equal to that pH at which the precipitation of the pigment is effected. The electrolyte is preferably a metal salt of the acid used for acidulation of the silicate. The acid and silicate are added to the receiving medium at a rate such that the precipitating pH is maintained constant. The products of the invention are characterized by their high abrasiveness and have a relative cleaning ability or scale (RCS) equivalent to high grade phosphates used as polishing agents in toothpastes and a superior fluoride compatibility to that of said phosphates.

Abstract: Precipitated silicas having very high structure as defined by the ability of the silica material to hold water in its wet cake, high oil absorption, and very high surface area can be produced by controlling the rate of acidulation during their production and maintaining the same at a very low rate during the course of the addition of acid to the solution of alkali metal silicate. The control of the index of refraction of the silica so produced is achieved by introduction of controlled amounts of adduct material such as aluminum sulfate to the acid prior to its introduction to the silicate solution.

Abstract: The invention relates to a process of the treatment of sodium silico fluoride. In the invention, sodium silico fluoride is decomposed with a relatively high concentration of an aqueous ammonium solution or an ammonia gas to produce a mixed aqueous slurry solution of ammonium fluoride containing sodium fluoride and silica gels as solid materials, the obtained mixed aqueous slurry solution is separated to the ammonium fluoride solutions containing sodium fluoride and silica gels, respectively, by means of a physical method and then sodium fluoride, silica gels and the aqueous ammonium fluoride solution are manufactured in high purity and good yield, respectively. In the other way, the mixture of sodium fluoride and silica gels are separated from said mixed aqueous slurry solution by means of the filter, washed with water and dried. The dried mixture is separated to sodium fluoride and silica gels by means of a physical method.

Abstract: A method of processing of waste gases containing hydrogen fluoride and silicon tetrafluoride or hydrogen fluoride, silicon tetrafluoride and sulfur dioxide by absorption of hydrogen fluoride and silicon tetrafluoride or hydrogen fluoride, silicon tetrafluoride and sulfur dioxide from waste gases by water solutions containing ammonium compounds such as ammonium carbonate, ammonium bicarbonate and ammonium fluoride. In addition to these ammonium compounds the absorption solutions contain sodium fluoride and ammonia. The absorption process produces a water solution containing ammonium fluoride and the precipitate of sodium fluosilicate. This solution is treated with sodium carbonate after which the precipitate of sodium fluoride is separated from the solution and the latter is delivered for absorption.

Abstract: A process for producing precipitated silicic acid pigments having new and improved properties is disclosed. The pigments are produced by the simultaneous introduction of a solution of an alkali metal silicate and an acid, such as sulfuric acid, into an aqueous receiving medium which contains a salt or electrolyte. The pH of the aqueous receiving medium is adjusted prior to the introduction of the acid and silicate so that it is the same or equal to that pH at which the precipitation of the pigment is effected. The electrolyte is preferably a metal salt of the acid used for acidulation of the silicate. The acid and silicate are added to the receiving medium at a rate such that the precipitating pH is maintained constant. The products of the invention are characterized by their high abrasiveness and have a relative cleaning ability or scale (RCS) equivalent to high grade phosphates used as polishing agents in toothpastes and a superior fluoride compatibility to that of said phosphates.

Abstract: In a process for the treatment of a material containing zinc and soluble silica by dilute aqueous solutions of sulphuric acid at a temperature below its boiling point under atmospheric pressure, the acid is progressively added to the zinc containing material over a period of at least 3 hours, in such a quantity that the final acidity of the solution will be 1.5 to 15 g/l, while carefully maintaining the temperature at 70.degree. to 90.degree.C, thereby inducing the lixiviation of the material and simultaneously the reprecipitation of silica in a crystalline form which can readily be eliminated by filtration.

Abstract: This invention discloses a new form of wet precipitated silica which is characterised in terms of energy required to breakdown particles and a defined thickening effect. A multistage precipitation and flocculation production process is also disclosed in which primary silica particles are prepared and flocculated using an alkali metal salt solution and further silica precipitated in the presence of the salt, the pH of the mixture reduced and the silica isolated, purified carefully dried and optionally milled.

Abstract: A process for producing amethyst crystals which involves growing colourless quartz crystals by a hydrothermal method of a temperature drop in a high-pressure autoclave on crystalline quartz seed plates oriented parallel to pinacoid crystallographic planes {0001} or to planes inclined to said pinacoid planes at an angle of up to 15.degree. with the use of silica as a charge, said growing being effected from aqueous solutions of ammonium fluoride with a concentration of from 5 to 30% by weight and containing iron introduced into the autoclave in the form of its oxydic or hydroxydic compounds in an amount ranging from 5 to 30 g/l of the solution. Said growing of colourless quartz crystals is effected at a crystallization temperature within the range of from 150.degree. to 500.degree.C under a pressure of from 10 to 1,200 kg/cm.sup.2 and at a crystal growth rate of from 0.05 to 1.5 mm/day.

Abstract: A process for preparing a wide-pore adsorbent adapted for use in chromatography, comprising mixing fine disperse non-porous silica having a specific surface area S of 35 to 380 m.sup.2 /g with water followed by drying the aqueous suspension at a temperature within the range of 100.degree. to 450.degree.C to give a silica xerogel and particulating thereof. The xerogel, prior to the particulation or thereafter, is subjected to the hydrothermal treatment in an autoclave at a temperature within the range of from 100.degree. to 380.degree.C and under a pressure of 1 to 300 atm., followed by drying at a temperature of 100.degree. to 300.degree.C.The above-described process enables the preparation of an adsorbent with larger pores as compared to adsorbents prepared from fine disperse non-porous silica and produced by conventional processes. The process according to the present invention makes it possible to produce an adsorbent having a specific surface area within the range of from 2 to 280 m.sup.