Showing papers on "Precipitated silica published in 1983"

Catalyst for alkylation of aromatic hydrocarbons

Abstract: This specification discloses a process for the alkylation of aromatics utilizing ZSM-23 catalyst. A particularly preferred embodiment utilizes ZSM-23 made from a forming mixture containing amorphous precipitated silica, as a silica source, including trace amounts of alumina and sodium chloride.

Adsorption of some divalent cations from aqueous solution on precipitated silica

Abstract: The adsorption of the cations CoII, NiII, CuII, ZnII and CdII on the K+ form of a precipitated silica is reported. The adsorption isotherms of CoII and of NiII at pH 7.0 and different temperatures follow the Langmuir isotherm. The endothermic ‘apparent’ heats of adsorption, 2 and 10 kJ mol–1, respectively, are compared with those for CuII and CdII. The limiting amount adsorbed, Xm, of the four ions decreases as the pH is lowered. An ion-exchange mechanism between hydrated K+ ions in the outer Helmholtz layer and metal, MII, ions in solution is proposed. The results also suggest that (MOH)+ ions are adsorbed at the higher pH values. A plot of Xm at pH 6.0 and 323 K for the five ions studied against atomic number exhibits the Irving–Williams sequence.At pH 3.0, i.e. close to the point of zero charge of silica, the adsorption results have been used to calculate the free energy of specific adsorption, ΔG, using the Grahame equation. ΔG was –11.1, –10.7, –13.4, –13.3 and –12.1 kJ mol–1 for M = Co, Ni, Cu, Zn and Cd, respectively. Specific adsorption is tentatively ascribed to the formation of surface coordination complexes.

Continuous process of removing silica from spent pulping liquors

Abstract: A continuous process of removing silica from spent pulping liquors (black liquors) which have been obtained by the alkaline digestion of annual plants. The spent liquor is preconcentrated and contacted with a CO2 -containing gas. The CO2 -containing gas is supplied at a rate of 30 to 40 m3 s.t.p. per m3 of spent liquor. The precipitated silica is removed from the treated liquor. The silica-containing precipitate which has been separated is diluted and washed with water and causticized by an addition of lime or milk of lime. Solid and liquid phases are separated from each other and the resulting residue is combusted.

Treatment of geothermal brine sulfate-rich fluids to facilitate the precipitation of silica

Abstract: A method for the treatment of geothermal brines to control the precipitation of silica is disclosed. A sulfate-rich liquid is introduced into geothermal brine within a production well prior to flashing or is introduced into the residual geothermal brine remaining after the brine has been flashed to produce steam. The sulfate in the liquid reacts with the barium, calcium, and/or lead salts within the brine to produce a colloidal suspension which serves to accelerate precipitation of silica from the brine and to adsorb the precipitated silica particles. The colloidal suspension with its adsorbed silica particles is then removed from the brine by conventional gravimetric or filtration methods. The method of the invention substantially reduces the deposition of silica in wellbores and in energy extraction equipment and facilitates removal of the silica from the brine. The method further reduces the deposition of silica in injection wells wherein the silica cleansed brine is discharged.

Process for improving the rheological properties of a suspension of precipitated silica

Abstract: The present invention provides a process for improving the rheological properties of a suspension of precipitated silica by the addition of an aluminum compound, thereby producing a sprayable suspension or slurry with a pH of greater than 3.5, a solids content of at least about 15% by weight, which may be spray dried to form silica in either powder or microbead form. In a preferred embodiment, the aluminum compound added to the suspension is in the form of sodium aluminate.

Manufacture of extremely high purity silica

Abstract: PURPOSE: To manufacture high purity silica by ultrafiltering an aqueous soln. of an alkali silicate, treating it with an ion exchange resin to prepare purified silica sol. adding a specified coagulating agent to deposit and precipitate silica, separating the silica from the mother liquor, and heat treating it. CONSTITUTION: A commercially available aqueous soln. of sodium silicate or potassium silicate contg. 20W35% SiO 2 is diluted to prepare an aqueous soln. contg. <10% SiO 2 . This aqueous soln. is ultrafiltered to remove collidal particles, and it is diluted to ≤5% concn. of SiO 2 and brought into contact with an ion exchange resin to prepare acidic silica sol. This silica sol is reacted with a coagulating agent which is gasified by heating such as NH 4 NO 3 , NH 4 Cl or (NH 4 ) 2 CO 3 . Silica is deposited and precipitated by the reaction. The precipitated silica is separated from the mother liquor, and the coagulating agent sticking to the silica is gasified by heating to manufacture extremely high purity silica. COPYRIGHT: (C)1985,JPO&Japio

Precipitated silica in silicone rubber

Abstract: Etude serieuse necessaire avant de remplacer de la silice obtenue par pyrolyse par de la silice precipitee

Structural Changes During the Silica Rubber Filler Precipitation Investigated by IR and NIR Spectroscopy

Abstract: Different kinds of silicic acids have been proved to have different properties in the infra red and near infra red1–2/. Precipitated white rubber fillers similarly as the pyrogenic Aerosil differ from silica gels by sharper and more intensive Si-O bands in the infra red, which may be explained by a higher periodicity of structure1/. In dry CCl4 Aerosils and precipitated silica rubber fillers form a permanent, more or less transparent suspension, whereas the silica gel particles drop to the bottom. The suspension of silicic acids gives a distinct spectrum of OH bands in the near infra red.

Adsorption of some divalent cations from aqueous solution on precipitated silica

Abstract: The adsorption of the cations CoII, NiII, CuII, ZnII and CdII on the K+ form of a precipitated silica is reported. The adsorption isotherms of CoII and of NiII at pH 7.0 and different temperatures follow the Langmuir isotherm. The endothermic ‘apparent’ heats of adsorption, 2 and 10 kJ mol–1, respectively, are compared with those for CuII and CdII. The limiting amount adsorbed, Xm, of the four ions decreases as the pH is lowered. An ion-exchange mechanism between hydrated K+ ions in the outer Helmholtz layer and metal, MII, ions in solution is proposed. The results also suggest that (MOH)+ ions are adsorbed at the higher pH values. A plot of Xm at pH 6.0 and 323 K for the five ions studied against atomic number exhibits the Irving–Williams sequence.At pH 3.0, i.e. close to the point of zero charge of silica, the adsorption results have been used to calculate the free energy of specific adsorption, ΔG, using the Grahame equation. ΔG was –11.1, –10.7, –13.4, –13.3 and –12.1 kJ mol–1 for M = Co, Ni, Cu, Zn and Cd, respectively. Specific adsorption is tentatively ascribed to the formation of surface coordination complexes.

Process for the preparation of boric acid as well as process for the preparation of silica using boric acid thus obtained

Abstract: Boric acid is prepared by reaction of a fluoroboric acid solution at elevated temperature with calcium carbonate and separation of the calcium fluoride precipitate formed from the remaining solution of boric acid. The fluoroboric acid solution used is preferably obtained by conversion of hexafluorosilicic acid with boric acid (formed from fluoroboric acid) and separation of the precipitated silica. Highly pure silica and valuable calcium fluoride can be prepared in a cyclic process using by-product hexafluorosilicic acid and cheap calcium carbonate.